Geology of the Sierra Nevada (California Natural History Guides) [2 ed.] 0520236955, 9780520236950

Table of contents :
CONTENTS
Acknowledgments
Introduction: The Ever-Changing Sierra
Geological Features and Where to See Them
Do-It-Yourself Rock Identification Key
Tables of Geological Features
Maps of Geological Sights
1. Geology: Of Time and Rocks
2. The Range Today
3. Being First
4. Plate Tectonics Puts the Sierra Nevada in Its Place
5. Seas of Long Ago
6. Great Is Granite
7. Treasures from the Earth
8. Landscapes of Yesteryear
9. Days of Fire
10. Days of Ice
11. Mono Lake: The “Dead Sea” of the West
12. The Yosemite “Problem”
13. The Mountains Tremble
Coda
Glossary
Suggestions for Further Reading

Citation preview

C A L I F O R N I A N AT U R A L H I S T O R Y G U I D E S

G E O L O G Y O F T H E S I E R R A N E VA D A

California Natural History Guides Phyllis M. Faber and Br uce M. Pavlik, General Editors

GEOLOGY of the

Mar y Hill

University of California Press, one of the most distinguished university presses in the United States, enriches lives around the world by advancing scholarship in the humanities, social sciences, and natural sciences. Its activities are supported by the UC Press Foundation and by philanthropic contributions from individuals and institutions. For more information, visit www.ucpress.edu.

California Natural Histor y Guide Series No. 80 University of California Press Berkeley and Los Angeles, California University of California Press, Ltd. London, England © 2006 by the Regents of the University of California Library of Congress Cataloging-in-Publication Data Hill, Mary. Geology of the Sierra Nevada / Mary R. Hill.— Rev. ed. p. cm. — (California natural history guides ; 80) Includes bibliographical references and index. ISBN 0-520-23695-5 — ISBN 0-520-23696-3 1. Geology—Sierra Nevada (Calif. and Nevada). 2. Sierra Nevada (Calif. and Nev.). I. Title. II. Series. QE90.S5H54 2006 557.94′4—dc22 Manufactured in China 10 09 08 07 06 10 9 8 7 6 5 4

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The paper used in this publication meets the minimum requirements of ANSI/NISO Z39.48–1992 (R 1997) (Permanence of Paper).A

Title Page: Mount Whitney (14,496 ft [4,418 m]) and adjacent mountains through an arch in the Alabama Hills. Whitney is near the center of the arch; to the left are Keeler Needle (14,240 ft [4,340 m]), Day Needle (14,080 ft [4,292 m]), and Third Needle (14,080 ft [4,292 m]). In many lists of high peaks, all four are grouped under “Mount Whitney.” The Alabama Hills, made of granitic rock like the Whitney group, look very old and worn. Worn they are, but their rock is roughly the same age as that in Mount Whitney—84 million years—despite the legend that they are the oldest rocks in the Sierra Nevada. The oldest rocks in the Sierra, as presently measured, are 542 million years old. The Earth’s own age is about 4.7 billion years, and a recent estimate of the age of the universe is 13.7 billion years. Cover photograph: Moonrise over Mount Whitney. Photograph by Larry Carver.

The publisher gratefully acknowledges the generous contributions to this book provided by the Gordon and Betty Moore Fund in Environmental Studies and the General Endowment Fund of the University of California Press Foundation.

CONTENTS

Acknowledgments

Introduction: The Ever-Changing Sierra Geological Features and Where to See Them

ix

1 9

Do-It-Yourself Rock Identification Key

11

Tables of Geological Features

17

Maps of Geological Sights

43

1. Geology: Of Time and Rocks

61

2. The Range Today

77

3. Being First

95

4. Plate Tectonics Puts the Sierra Nevada in Its Place

129

5. Seas of Long Ago

149

6. Great Is Granite

177

7. Treasures from the Earth

211

8. Landscapes of Yester year

241

9. Days of Fire

259

10. Days of Ice

289

11. Mono Lake: The “Dead Sea” of the West

321

12. The Yosemite “Problem”

335

13. The Mountains Tremble

363

Coda Glossary Suggestions for Further Reading

393 395 423

Quotation References Figure References Plate Credits Index

427 431 435 437

Overleaf: Jointed rock, making a steep face in the Sierra Nevada. The squarish blocks would make good stepping-stones if one had sevenleague boots. (See also pl. 31.)

ACKNOWLEDGMENTS In addition to all those who helped me with the first edition of this book — good friends such as Elisabeth Egenhoff, Robert D. Morgan, and Sarah Davis, who were my companions on numerous Sierran expeditions—my readers and I would not have this book without the work of the many fellow geologists of this past century and a half. For this current edition, I would like to thank that premier writer and editor Genny Smith, whose interest, support, and comments have been exceedingly useful. My special friend, Ute Haker, greatly improved the current manuscript, particularly the difficult parts, and kept me inspired and my nose to the grindstone. So did the staff of UC Press, who are largely responsible for this newly illustrated edition. Thanks especially to Stephanie Rubin, who gathered most of the color photographs; to Hayden Foell, who drew the maps; and to Scott Norton, Kate Hoffman, and Laura Cerruti, who worried about the words and the beautiful design. I also thank Bill Guyton for his careful reading, and my longtime friend Ed Kiessling for his help. Mike Diggles kindly made his extensive collection of slides available and stirred my jealousy of his trips. My good friends Susan Moyer and Dorothy Radbruch Hall aided me with photographs and comments. I hope that you, my readers, will like this book. It was fun to write.

ix

INTRODUCTION THE EVER-CHANGING SIERRA

Overleaf: Mount Russell from the summit of Mount Whitney. Mount Russell (14,086 ft [4,293 m]) was named for Israel C. Russell, pioneer Sierran geologist who studied and mapped much of the Sierran country in the nineteenth century. The knife-edged ridges shown here are typical of the high country. Many of them were carved by glaciers located on either side of the ridge, which almost, but not quite, met.

is the longest, highest, and most spectacular mountain range in the “lower 48” (fig. 1). It is a mighty mountain range, tall and long, with spectacular canyons, world-famous waterfalls, and precipitous peaks. How it got that way is the subject of this book, as it was of the first edition. Why a second edition? For one thing, science moves forward. Much more is known about the story of the Sierra Nevada today than we knew 30 years ago. “But aren’t the rocks the same?” a friend asked. Yes, of course they are, but some were never studied closely, and our way of looking at all of them has changed. Just a handful of years before the first edition of this book was prepared, a new, radical, unifying concept—plate tectonics— burst on the geological world, giving geologists a way to explain why many mountain ranges exist where they do, to make sense out of areas of Earth puzzling to scientists. Plate (or “global”) tectonics proposes that in the past the continents were joined and have, through the long reaches of time, drifted or been torn apart— probably more than once. In this view, the Earth comprises several large “plates” and numerous small ones containing continents and seas, all riding on part of the Earth’s underlayment. It is a unifying theory that not only reunites continents, but explains how mountains and valleys were formed, what is happening to the seas, and why land and water are distributed as they are. By the time the first edition was underway, no one had written specifically about plate tectonics and the Sierra Nevada, although clearly there was much to learn and much to say. Since then, the Sierra has been put through the plate tectonics intellectual filter, which has told us how the mountains might have been created, and why they are where they are. True, the first edition contained a short, broad-brush chapter on plate tectonics, but this new version of Geology of the Sierra Nevada has incorporated plate tectonics throughout the book, as well as in a greatly expanded chapter, as you will see. More than a cosmetic change, the new material increases our deeper understanding of the mountains. The book has some specialized words in it, but most of them are defined as you first read them, or in the glossary. In addition, the book has a new design and many more photographs. This edition also has more on human exploration of the Sierra Nevada, not just by geologists, although they were in the forefront of explorers, but by immigrants, trappers, and others THE SIERRA NEVADA

THE EVER-CHANGING SIERRA

3

C a s c a d e Ra

Klamath Mountains

Modoc Plateau

Great Basin

nge

North C o a st

Great Basin

R a n ges Si e rr a N e

rra S ie da

ley

lls oothi

l V al

a Nev

va da F

a Centr C e nt r a

l and S o ut

Great Basin

h Co

a st R an

g es

T ran

sve

rs e

R an

Mojave Desert ges

P ins en u la

Channel Islands

rR

ang

es

Colorado Desert

Figure 1. Location of the Sierra Nevada. The range is geologically related to mountains in the Peninsular Ranges of southern California and to the Klamath Mountains to the north.

4

THE EVER-CHANGING SIERRA

who pushed over the mountains. New chapters and numerous sidebars expand on the human impact on the Sierra Nevada. Although to us, whose days are brief, the Sierra Nevada seems immensely old (part of the “everlasting hills”), it is not, for it reveals but a tenth of the Earth’s tumultuous four-and-a-half-billionyear history. The record written in Sierran rocks starts hundreds of millions of years ago, in the middle of things. It opens in the depths of seas we will never sail, pushed aside by rising mountains we will never climb, drained by rivers we will never swim that rush through tropical forests inhabited by animals we will never see and birds we will never hear. It is a tale of steaming volcanoes and chilling glacial ice; of quiet, warm, shallow seas and sudden earthquakes. This edition, like the first, is an account of those events and of how we know that they took place. Its chapters emphasize the dynamic means by which the Sierra has changed through eons, one moment at a time, and continues to change even while humans camp in its canyons, climb its peaks, search for gold, or write the second edition of an earlier book. Erosion, volcanism, and glaciation are among the processes at work in the Sierra Nevada—erosion wearing the mountains down to stubs repeatedly; volcanism giving birth to volcanoes that spout forth lava and ash; glaciation filling the valleys with ice

Plate 1. Glass Creek obsidian flow, Inyo Domes, Long Valley Caldera.

THE EVER-CHANGING SIERRA

5

Plate 2. Tenaya Lake and Mount Conness, Yosemite National Park.

and slicing peaks into splinters. And we should not neglect sedimentation, which has piled grain upon grain in countless rivers and valleys, and at the bottom of the sea. Today, the rain and snow, the rivers and streams, the cold and bitter winds are at work altering the mountains — wearing them down, carrying them away. Even as we describe them, they are changing. To enhance your enjoyment of the Sierra Nevada, go into the mountains with your eyes opened to geology. Try to get a sense of what has happened to the mountains. You may decide that you do not know; perhaps no one knows; and you will be correct. All anyone can do is to give you what other students of the Sierra think or have thought. None of them is right or wrong. Ideas must be revised as fast as new facts are discovered. This is the scientific method, and the way of all learning. The chronology of the Sierra has not been easy to determine. It has taken hundreds of work-years to bring us to our present understanding of its complex history. Even so, we are looking through a glass darkly, for there are so many unresolved problems that our ideas of Sierran history and origin will surely change drastically again. But for now, this is what we know. Rocks are basic to the study of geology. The Earth, after all, is a gigantic rock, and through the study of its parts we hope to come to an understanding of the Earth as a whole. If you do not already

6

THE EVER-CHANGING SIERRA

Plate 3. Folded metalimestone (marble), Convict Creek, Convict Lake Basin. Fossils in Convict Lake Basin are very old, some dating back over 500 million years.

have a good idea of the different kinds of rocks but plan to visit the range, try to identify actual Sierran rocks by using the following rock key. This key is an interactive gateway into the rest of the book. By tracing the steps in the key, you can take any rock from the Sierra Nevada and determine what kind of rock it is. You will make some mistakes, and no key is foolproof. Rocks are difficult. Your answer, derived from the key, will be a fairly simple rock name. It is possible (and likely) that any geologist you ask will give your rock a more complex name. That does not matter; if you have identified it within a broad group, you will have taken the first step in understanding the process by which it got there and what it represents. Refinements in naming can come later. In fact, the whole problem of naming is quite complex, for a variety of reasons, some historical and some technical. It can be difficult for an individual unversed in the terminology to read geologic reports simply because the words are so strange. To make it possible for you to read technical geologic reports on the Sierra Nevada, if you like, the glossary lists most of the technical names that have been given to rocks of the Sierra. Through eyes opened by geology we can envision the turbulent history of the high peaks. By observing broad vistas, as well

THE EVER-CHANGING SIERRA

7

as microscopic details, we can look backward into time to see for ourselves the progress of Sierran yesterdays. After all the rocks are named and renamed, after the processes are described and redescribed, after geologic theories are thought and rethought, after all of the technical terms are defined and redefined, the mountains still abide. The rocks are there for you to study; you can find new facts and develop new theories, or you can deepen your appreciation of the mountains by understanding a bit more of the story they tell of the mighty range we call the Sierra Nevada.

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THE EVER-CHANGING SIERRA

GEOLOGICAL FEATURES AND WHERE TO SEE THEM

The following do-it-yourself key with supplemental tables and maps allows you to identify most of the rocks you encounter in the Sierra. For easy use, it is created like a botany key. Because it uses both the appearance of the rock and, in some cases, the appearance of the Sierran outcrop from which it came, the key is not usable in other areas, although similar ones could be constructed for any mountain range. Materials you need in order to use this key are a hand lens or field magnifier, preferably 10 power or more; a small amount of vinegar or other mild acid; a pocketknife or nail; a prospector’s geologic pick or other hammer; and a small container of water. Protective glasses are not required for the identification of rocks but are necessary for your own safety. Try it: Chip off a piece of rock from a Sierran outcrop and follow through the brief, easy steps below—usually five or six. At the end, you should have the name of the rock. For example, suppose you select a rock from Panum Crater near U.S. Hwy. 395. The first question you should ask is “does it float on water?” (Some rocks do!) If your answer is yes, the rock is pumice. Or, try this: “No, it does not float on water.” So, go to key 1 in the actual rock guide below. At 1, you are asked if the rock consists wholly of quartz (check table 1 if you are unsure). Let us say you do not know. Choose 2. Here you need to take a bit of acid (vinegar will do) and put it on the rock. Look at the note at 2 to understand the “fizzing.” It does fizz? Then you probably have calcareous rock (or its metamorphic equivalent, marble), described in table 2. Here is an example of a more difficult route: “No, it does not float on water.” So, go to 1. At 1, you are asked if it consists wholly of quartz. You do not know? Then go to 2. At 2, you are asked if the rock fizzes if acid is placed on it. No? Then go to 3. Are the individual rock or mineral grains large enough to see. No? Go to 5, where you must determine if it breaks in

“scoops,” like a piece of broken glass. No? Go to 6. The rock is not wholly dark brown or black, you say. Go to 7. Does it have a greasy look? Yes? Then you likely have serpentine, the California state rock. Check table 2 to verify your identification. Before you perform the tests, select a fresh piece of rock, that is, one that has not been exposed to weather. Most rocks become crusted after being exposed to air. Their color changes; their hardness changes; in fact, even the minerals themselves change. For that reason, break the rock open to see a fresh, unweathered surface. If at all possible, try to obtain the rock “in place.” Take it from an outcrop. That way, the sample will certainly be from the Sierra Nevada. Also, the outcrop itself—its location, shape, and aspect—may aid in the identification of your rock. Once you’ve reached a table, you are ready to validate your conclusion and find the rock’s name.

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DO-IT-YOURSELF ROCK IDENTIFICATION KEY

Rock floats on water . . . . . See pumice, table 5 (wasn’t this easy?) Rock does not float on water . . . . . . . . . . . . . . . . . . . . . . . Go to 1 1a 1b

Rock consists almost wholly of quartz (check table 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 26 Rock does not consist almost wholly of quartz or it is not possible to tell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 2 Note: One way to distinguish between the glassiness of quartz and the sheen of calcareous minerals is by scratching the rock or mineral with a nail or knife (see scratch test at 4).

2a 2b

Rock effervesces (fizzes) when acid is placed on it . . . . . . . . . . . . . . . . . . . . . . . . . . See calcareous rock, table 2 Rock does not fizz when acid is placed on it. . . Go to 3

Note: If you use vinegar, a very weak acid, you may see fizzing only under your hand lens. Be certain that the bubbles—the fizz—are distributed more or less uniformly throughout the drop of acid. Use a fresh surface for this test, as particles of dust may masquerade as fizz.

3a 3b

Rock has individual pieces of rock or grains large enough to see by eye or with a hand lens. . . . . . . . . . . . . . . . . . . Go to 4 Very few or no individual pieces of rock or grains are large enough to see by eye or with a hand lens. . . . . . . . . . Go to 5 Note: Texture of the rock—the size and arrangement of its mineral grains—is in question here. Color does not affect texture; fragments of rocks and minerals, whatever their color, are critical in determining texture. Very fine-grained rocks have grains too small to see either by eye or under a hand lens. Shale is such a rock: too fine grained to show its individual minerals. For such a rock, choose “Go to 5.” If individual grains or fragments can be distinguished, either

by eye or under the hand lens, the rock has coarse enough grain that you should select “Go to 3.” Granite and sandstone are such rocks. The salt-and-pepper look of granite is due to individual mineral grains of different colors, which you can see if you look at the rock closely. Sandstone, observed carefully, may be seen to be made up of similar grains cemented together. Or it may have several types of grains cemented together. The gritty “feel” of sandstone is a clue that it is made up of individual particles, which can be seen by eye or under the hand lens. If you can, try to compare granite and sandstone to clay and coal to see the difference in texture. Beware also of “accidental” inclusions in a rock in which the grains are otherwise indistinguishable. If there are only one or two such inclusions (fossils, for example), you should nevertheless select the second alternative; if there are several, or numerous “chunks” in the rock (like raisins in pudding), choose “Go to 3.”

4a 4b

Rock can be scratched by knife or nail on fresh surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 25 Rock cannot be scratched by knife or nail on fresh surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 5

Note: Inspect the scratch carefully with your hand lens to be certain that the rock has been scratched. If you see a metallic line on the rock, very likely the rock is harder than the nail. If you see a ridge of rock dust and an accompanying groove, the nail is harder than the rock.

5a

5b

Rock breaks in scoops (see note below) . . . . . . . . See chert, table 2, and obsidian, table 5; compare rhyolite, table 5, hornfels, table 2, and quartz, table 1 Rock does not break in scoops . . . . . . . . . . . . . . . . . . Go to 6 Note: Glass, when broken, shows conchoidal fracture on its edges. “Conchoidal” refers to the concentric, shell-like “scoops” on the broken part.

6a 6b

Rock is wholly dark brown or black on fresh surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 9 Rock is not wholly dark brown or black on fresh surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 7

Note: Beware of crystals or accidental inclusions. It is the overall color that is critical.

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7a

Rock has greasy look on fresh surfaces; may be greenish or brown; may split along thin planes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See serpentine, table 2 7b Rock does not have greasy look . . . . . . . . . . . . . . . . . Go to 8 8a Rock consists entirely of mineral grains or rock fragments of approximately the same size . . . . . . Go to 35 8b Rock does not consist of mineral grains or rock fragments of approximately the same size . . . . . . Go to 25 9a Rock has shiny or satiny surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See slate, table 2; compare schist, table 2 9b Rock does not have shiny or satiny surface . . . . . . . Go to 10 10a Rock is vesicular (has holes) . . . . . . . . . . . . . . Go to 46 10b Rock is not vesicular . . . . . . . . . . . . . . . . . . . . Go to 11 11a Can see a rock outcrop (field exposure) in the landscape, far or near . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 12 11b Cannot see a field exposure . . . . . . . . . . . . . . . . . . . Go to 14 12a Field exposure resembles columns . . . . . . . . . Go to 14 12b Field exposure does not resemble columns . . Go to 13 13a Field exposures on rolling hills with large boulders mixed with smaller material . . . . . . . . . . . . . . . . . . . . . . . . Go to 14 13b Field exposures not on rolling hills with large boulders mixed with smaller material . . . . . . . . . . . . . . . . . . Go to 15 14a Chip of rock held to light has translucent edges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See andesite, table 5 14b Chip of rock held to light is opaque . . . . . . . Compare basalt, table 5, hornfels, table 2, and lignite, table 4 15a Field exposures in layers. . . . . . . . . . . . . . . . . . . . . . Go to 16 15b Field exposures not in layers . . . . . . . . . . . . . . . . . . Go to 19 16a Rock splits along nearly parallel lines (bedding planes); you can examine the rock where it already may have split, or by hammering the rock carefully . . . Go to 17 16b Rock does not split along parallel lines. . . . . . Go to 18 17a Rock has greasy look on fresh surfaces; may be greenish or brown; may split along thin planes . . See serpentine, table 2 17b Rock does not have greasy look . . . . . . . . . . . . . . . . Go to 18 18a Rock splits along parallel lines to leave shiny smooth surface . . . . . . . . . . See slate, compare hornfels, table 2 18b Rock splits along more or less parallel lines but does not leave shiny smooth surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . See hornfels, table 2, compare shale, table 4 19a Field exposures in large, distinguishable flows . . . . Go to 20

D O - I T - Y O U R S E L F R O C K I D E N T I F I C AT I O N K E Y

13

19b Field exposures not in distinguishable flows . . . . . Go to 21 20a Chip of rock held to light has translucent edges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See andesite, table 5 20b Chip of rock held to light is opaque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See basalt, table 5 21a Rock splits easily into thin layers . . . . . . . . . . . . . . . Go to 22 21b Rock does not split easily into thin layers . . . . . . . . Go to 23 22a Rock has shiny smooth surface. . . . . . See slate, table 2 22b Rock does not have shiny smooth surface . . . Go to 23 23a Rock is red . . . . . . . . . . . . . . . . . . . . . . . . See laterite, table 4 23b Rock is not red . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 24 24a Rock is soft, punky, and burns smokily in fire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See lignite, table 4 24b Rock is not soft and punky and does not burn. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 25 25a Rock becomes plastic and sticky if wet. . . . . See clay, table 4 25b Rock does not become plastic and sticky if wet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 26 26a Rock breaks across grains . . . . . . . . . . . . . . . . . . . . . . . . . . . . Compare quartzite, table 2, and andesite, table 5 26b No grains are distinguishable . . . . . . . . . . . . . Go to 27 27a Rock may be in layers . . . . . . . . . . . . . . See rhyolite, table 5; compare with sandstone, table 4, and tuff, table 5 27b Rock not in distinguishable layers . . . . . . . . . . . . . . Go to 28 28a Rock consists of rounded or angular grains and pebbles. . . . . . . . . . . . . . . . . . . . See conglomerate, table 4; compare with conglomerate breccia, table 4 28b Rock does not consist of rounded or angular grains and pebbles. . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 29 29a Field exposures are visible . . . . . . . . . . . . . . . . . . . . Go to 30 29b Field exposures are not visible . . . . . . . . . . . . . . . . . Go to 31 30a Field exposures may be in distinguishable layers, which may have a texture (not necessarily color) like granulated sugar . . . . . . . . . . . . . . . . . . . . . . . Go to 32 30b Field exposures not in distinguishable layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 31 31a Rock has greasy look; may be greenish or brown; may split along thin planes . . . . . . . . . . . . . . . . See serpentine, table 2 31b Rock does not have greasy look . . . . . . . . . . . . . . . . Go to 32 32a Rock rings when struck . . . . . . . . . See rhyolite, table 5 32b Rock does not ring when struck . . . . . . . . . . . Go to 33

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Note: To ring a rock, strike it with a hammer while you are holding the rock freely in your hand; otherwise, the sound may be damped.

33a Rock breaks easily around grains. . . . See sandstone, table 4 33b Rock does not break easily around grains or no grains are distinguishable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 34 34a Rock has greasy look; may be greenish or brown; may split along thin planes . . . . . . . . See serpentine, table 2 34b Rock does not have greasy look. . . . . . . . . . . . Go to 35 35a Rock consists of broken fragments or rounded grains cemented together. . . . . . . . . . . . . . . . . See sandstone, table 4, and quartzite, table 2 35b Rock does not consist of broken fragments or rounded grains cemented together. . . . . . . . . . . . . . . . . . . . . Go to 36 Note: The difference required here is between a rock that is cemented together and one in which the grains are intergrown. If the grains are separate, yet the rock adheres together, choose the first alternative. If you can see interfingering of grains with your hand lens, choose the second. Experience in studying a known sample of sandstone (separate grains) and one of granite (interfingering grains) will help you with this distinction.

37a 37b

39a 39b

36a Rock has gritty feel. . . . . . . . . . . . . . . . See tuff, table 5; compare with shale, table 4, and cinder, table 5 36b Rock does not have gritty feel . . . . . . . . . . . . . Go to 37 Rock has wavy, banded, knotted, clotted, or gnarled appearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 38 Rock does not have wavy, banded, knotted, clotted, or gnarled appearance . . . . . . . . . . . . . . . . . . . . . . . . . Go to 39 38a Rock breaks along distinct lines, has flaky appearance (usually due to mica flakes) . . . . . . . See schist, table 2; compare with mariposite, under mica, table 1 38b Rock does not always break evenly along distinct lines but shows streaking of mineral grains, especially quartz, feldspar, and dark minerals . . . . . . See gneiss, table 2; compare with breccia, under conglomerate, table 4 Rock has a matrix of small grains with larger ones scattered through. . . . . . . . . . . . . . . . . . . . . . . . . See porphyry, table 3 Rock does not have a matrix with large grains . . . . Go to 40 40a Rock breaks in scoops (see note at 5) . . . . . . . . Go to 41

D O - I T - Y O U R S E L F R O C K I D E N T I F I C AT I O N K E Y

15

40b Rock does not break in scoops . . . . . . . . . . . . . Go to 42 41a Rock is glassy . . . . . . . . . . . . . . . . . . . . . See obsidian, table 5 41b Rock is not glassy . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 43 42a Rock rings when struck with hammer . . . . . . . . . . . . . Compare slate and hornfels, table 2, and basalt and andesite, table 5 42b Rock does not ring when struck with hammer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 43 43a Rock splits along definite planes; minerals large enough to see with hand lens . . . . . . . . . . . . . . . . . . See phyllite, table 2 43b Rock does not split easily along definite planes . . . Go to 44 44a Rock has grains of uniform size or no grains are visible . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 45 44b Rock has some large grains, others small . . . . Go to 39 45a Rock may break in scoops (see note at 5) . . . . . . . See chert, table 2; compare rhyolite, table 5, hornfels, table 2, and quartz, table 1 45b Rock does not break in scoops. . . . . . . . . . . . . . . . . Go to 46 46a Rock has spongy, porous look (but may be hard) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See cinder, table 5 46b Rock does not have spongy, porous look . . . . . . Go 47 47a Rock is dark red . . . . . . . . . . . . . . . . . . . . See laterite, table 4 47b Rock is not dark red . . . . . . . . . . . . . . . . . . . . . . . . . Go to 48 48a Rock has considerable quartz, also feldspar (see table 1); may have dark minerals; usually has a salt-andpepper appearance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See granite (granitic rock), table 3 48b Rock has very little or no quartz . . . . . . . . . . . Go to 49 49a Rock has feldspar and dark minerals. . . . . . . . . . . . Go to 50 49b Rock has no feldspar; only dark minerals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See peridotite, table 3 50a Rock has less than 50 percent dark minerals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See diorite, table 3 50b Rock has more than 50 percent dark minerals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See gabbro, table 3

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TABLES OF GEOLOGICAL FEATURES

TABLE 1

Common Rock-Forming Minerals

The few minerals essential to the field identification of igneous rocks are given here. The table is undoubtedly too simple, because it is not easy to be certain that a mineral is correctly identified when only a handful of the 1,500 recognizable by sight are listed. A good mineral identification book is an excellent start toward correct identification, but the quickest, surest, and best way to learn minerals is to see and touch the minerals themselves. AMPHIBOLE

Characteristics Common in dark-colored igneous rocks Commonly dark green or black; may look as if it were lacquered Crystals commonly long and narrow In granitic rock, commonly shows as brilliant black laths. Breaks (cleaves) at oblique angles (56° and 124°); pyroxene cleaves at right angles Where to see an example Near Nevada City (map 4, 1) Cosumnes copper mine, near Fairplay (map 5a, 3) Carson Hill mine, Calaveras County (map 7, 21) Near Vallecito (map 8, 4) Near Twin Lakes, Fresno County (map 11, 19) CALCITE

Characteristics Pearly or glassy appearance Breaks (cleaves) at oblique angles into rhombs Fizzes with acid Can be scratched by knife or nail Where to see an example Common in metamorphic rocks in the Sierra Nevada Not common in Sierran igneous or sedimentary rocks continued ➤

TABLE 1 continued

FELDSPAR

Characteristics Orthoclase group contains potassium; plagioclase group contains sodium and calcium The most common family of minerals Nearly as hard as quartz; does not appear as glassy Resembles porcelain Orthoclase may be pink; plagioclase is white to dark gray Does not fizz with acid Many fragments of feldspar show a multitude of closely spaced parallel lines Where to see an example Kingsbury grade (map 3, 4); see also “mica” Lembert Dome (map 9, 13) and Cathedral Peak (map 10, 4), Yosemite National Park; the “lumps” in the granitic rock are feldspar crystals Twin Lakes, Fresno County (map 11, 19) MICA

Characteristics Two varieties are common: muscovite, a clear mica, and biotite, which is dark An unusual mica in the Sierra Nevada is mariposite, a green mica containing chrome All mica splits into very thin sheets Very soft and flaky Does not fizz with acid Glimmers in the sun, so that tiny fragments in stream bottoms may be mistaken for gold (which is much heavier) Where to see an example Large “books” of mica are in pegmatite rock on Kingsbury grade (map 3, 4) Muscovite is “isinglass”; old-fashioned screw-in fuses have muscovite plates in the ends Mariposite is in road outcrops on State Hwy. 49 near Coulterville (map 8, 13), and at the Josephine (map 8, 18) and Mary Harrison (map 8, 14) mines PYROXENE

Characteristics Common in dark-colored igneous rocks

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Resembles amphibole except that pyroxene breaks at nearly right angles, and crystals are short and stubby rather than long and thin. An end view of a pyroxene crystal is nearly a square Where to see an example In gabbro, Nevada City (map 4, 1) Twin Lakes, Fresno County (map 11, 19) QUARTZ

Characteristics The most durable family of common minerals May sparkle like tiny glass beads (vitreous luster) Knife or nail does not scratch Does not effervesce (fizz) with acid Commonly clear, especially if it is a constituent of granitic rocks, but pebbles and boulders of white (milky) quartz are common in the Sierra Nevada Where to see an example Bear River, near Colfax (map 4, 5); cobbles of white quartz glisten in stream bed Clear crystals of quartz in mines near Mokelumne Hill (map 7, 10) White quartz vein near Jamestown (map 8, 9) and Coulterville (map 8, 12) Smoky quartz crystals at Dinkey Dome (map 11, 25)

TABLE 2

Metamorphic Rocks Commonly Found in the Sierra Nevada

CALCAREOUS ROCK

Characteristics Includes limestone, marble, dolomite, calc-hornfels Probably derived from limestone, dolomite Generally softer than other metamorphic rocks Usually effervesces (fizzes) in acid May contain fossils Where to see an example Caves

Mercer’s (near Murphys) (map 8, 1) Moaning (near Columbia) (map 8, 5) continued ➤

TA B L E S O F G E O L O G I C A L F E AT U R E S

19

TABLE 2 continued

Bower (map 8, 10) Boyden (map 13, 1) Crystal (Sequoia National Park) (map 13, 3) Clough (map 13, 12) Quarries

Cool-Cave Valley (map 4, 9) Diamond Springs (map 5a, 2) Near Volcano (map 7, 4) San Andreas (Kentucky House) (map 7, 17) Columbia (map 8, 6) Exposures from Mining

Near North San Juan, where river and State Hwy. 49 meet (map 2, 4) Near Volcano (map 7, 4) Volcano, buildings (map 7, 5) Indian Grinding Rock State Historic Park (map 7, 6) Columbia quarry (map 8, 6) CHERT (META)

Characteristics Probably derived from hert; replacement in other rocks Flinty appearance Grains not discernible Dish-shaped (conchoidal) fracture pattern Where to see an example South Fork Wolf Creek, Nevada County (map 4, 6) Hunter Valley, Mariposa County (map 8, 19) Merced River Canyon, State Hwy. 140 at the “Geological Exhibit” (map 10, 8) GNEISS

Characteristics Probably derived from sandstone, granite Medium to coarse grained Has knotted and gnarled appearance Commonly contains quartz, feldspar, and dark minerals

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Where to see an example Garnet Hill, Calaveras County (map 5b, 4) Twin Lakes, Fresno County (map 11, 19) Not common in Sierra Nevada GREENSTONE

Characteristics Probably derived from basalt and andesite; possibly also peridotite, gabbro, or serpentine Very fine grained Dark Does not show individual grains or crystals Weathers to red soil Where to see an example American River Canyon near bridge on road from Cool to Auburn (map 4, 8) Near Jamestown (map 8, 7) Near Coulterville (map 8, 11) Many places along State Hwy. 49 HORNFELS

Characteristics Can be derived from anything; calc-hornfels derived from calcareous rock Very fine grained; may have some large crystals in fine-grained matrix Flinty appearance Where to see an example Bond Pass, Emigrant Basin (map 6, 16) Ellery Lake (map 9, 8) Tioga Lake (map 9, 9) Mono Pass (map 9, 17) Mount Lewis, Mono Pass (map 9, 22, 17) Minarets Lookout (map 9, 44) PHYLLITE

Characteristics Probably derived from shale Breaks along flat planes Individual grains visible, especially mica continued ➤

TA B L E S O F G E O L O G I C A L F E AT U R E S

21

TABLE 2 continued

Where to see an example Merced River Canyon, State Hwy. 140 at the “Geological Exhibit” (map 10, 8) QUARTZITE

Characteristics Sandstone Fine to medium grained Generally layered Very hard May be light colored Where to see an example Bond Pass, Emigrant Basin (map 6, 16) Convict Lake, near Mount Morrison (map 11, 10) Miningtown Meadow (map 11, 23) and Grouse Lake (map 11, 24), Huntington Lake 15-minute quadrangle Not common in Sierra Nevada; most rock called quartzite in older reports is here called chert (metachert) SCHIST

Characteristics Probably derived from shale, volcanic rock, fine-grained sandstone, shaly sandstone, chert, or any fine-grained rock Flaky Minerals large enough to be seen; micas usually obvious In irregular, twisted layers (foliated) Where to see an example Bond Pass, Emigrant Basin (map 6, 16) Good field on State Hwy. 4 west of Copperopolis (map 7, 23) Near Coulterville (map 8, 12) Schist quarries at French Mills (map 8, 15) and Mount Ophir (map 8, 20) Shadow Canyon, off John Muir Trail, near Devils Postpile (map 9, 43) “Tombstone rocks” (also called “gravestone slates”) in Mother Lode area SERPENTINE

Characteristics Probably derived from periodotite, pyroxenite, other rocks composed of dark minerals

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Usually fine grained but may be granular Green to black in color Generally breaks in slivers Greasy look and feel Where to see an example Rollins Lake (map 4, 4) Bagby grade, 6 mi (10 km) north of Bagby (map 8, 17) Common in western foothills of the Sierra Nevada SLATE

Characteristics Probably derived from shale, tuff Very fine grained; grains cannot be seen even with a hand lens Shiny surface Breaks along flat planes (“fissile”; has “slaty cleavage”) Where to see an example Yuba River and road cuts east of Downieville (map 2, 2) Chili Bar mine, on south side of South Fork, American River, 3.5 miles (5.6 km) north of Placerville (map 5a, 1) Cape Horn, State Hwy. 4, Dardanelles Cone 15-minute quadrangle (map 6, 10) Agua Fria quarry (map 8, 21)

TABLE 3

Plutonic Igneous Rocks Commonly Found in the Sierra Nevada

DIORITE

Characteristics Rock once called quartz diorite is now called tonalite Grains large enough to distinguish from one another No quartz; plagioclase feldspar and dark minerals compose most of the rock (dark minerals are less than 50 percent) Gray Where to see an example Interspersed with metamorphic rock near Copperopolis (map 7, 22) El Portal (map 10, 9) continued ➤

TA B L E S O F G E O L O G I C A L F E AT U R E S

23

TABLE 3 continued

The Rockslides, Yosemite National Park (map 10, 11) In smaller plutons in the western Sierra GABBRO

Characteristics Grains large enough to distinguish from one another No quartz; plagioclase and dark minerals compose most of the rock (dark minerals are more than 50 percent) Dark gray to black Where to see an example On State Hwy. 49 1.5 mi (2.4 km) north of Camptonville (map 2, 3) Near Rough and Ready, Nevada County (map 4, 2) In road cuts 6 to 8 mi (9.6 to 13 km) west of Hornitos (Guadalupe Intrusive Complex) (map 8, 16) Twin Lakes, Fresno County (map 11, 19) GRANITE

Characteristics Here includes granodiorite and quartz monzonite Grains large enough to distinguish from one another Contains quartz, orthoclase feldspar, and potassium feldspar; may contain some dark minerals Usually has salt-and-pepper appearance; may be pinkish Where to see an example Desolation Valley (map 3, 8) Indian grinding rocks at Grover Hot Springs State Park (map 6, 4), and Yosemite Valley (map 10, 16) Yosemite National Park (map 10) Alabama Hills (map 14, 2) Mount Whitney (map 14, 4) PEGMATITE

Characteristics Very large crystals, usually quartz, feldspar, and mica Where to see an example Kingsbury grade (map 3, 4)

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PERIDOTITE

Characteristics Grains large enough to distinguish from one another Dark green or black No quartz, no feldspar Dark minerals only Where to see an example Red Hill, northwest of Meadow Valley, Feather River, Plumas County (map 1, 1) Pulga, Butte County (map 1, 3) Most peridotite in the Sierra Nevada has been partly or wholly altered to serpentine PORPHYRY

Characteristics Lumpy; some crystals much larger than others Where to see an example Lembert Dome, Tioga Pass Road, Yosemite National Park (map 9, 13) Cathedral Peak, Yosemite National Park (map 10, 4) Both of these are porphyritic granite exposures; better example of porphyry is the rhyolite dike west of Convict Creek, Mount Morrison quadrangle (map 11, 10)

TABLE 4

Sedimentary Rocks Commonly Found in the Sierra Nevada

CLAY

Characteristics Plastic, pliable when wet Commonly red, white, or gray Where to see an example Clay pits near Lincoln (map 4, 7), at Ione (map 7, 2) Sierran clay is to be seen mostly in lower western foothills CONGLOMERATE

Characteristics Rock is made up of grains 2 mm or more in diameter, together with coarser fragments continued ➤

TA B L E S O F G E O L O G I C A L F E AT U R E S

25

TABLE 4 continued

If fragments are angular, rather than rounded, rock is “breccia,” a word that can be used also for volcanic rocks made up of angular fragments Where to see an example Big Chico Creek (map 1, 2) Gravel at Malakoff Diggins State Historic Park (map 2, 5); Gold Run hydraulic pit, U.S. Interstate 80 (map 4, 3); other hydraulic mines Auriferous (gold-bearing) gravel; most is not consolidated enough to be called conglomerate. Some cemented gravel in lower part of Tertiary channels is conglomerate LATERITE

Characteristics Bright red soil Where to see an example Near Camptonville (map 2, 3) LIGNITE

Characteristics Soft, punky; wood structure visible in some specimens Lignite is soft coal (harder coal is classed as a metamorphic rock) Where to see an example Mines at Ione (map 7, 3) and Carbondale (map 7, 1) Buena Vista lignite mine (map 7, 16) SANDSTONE

Characteristics Rock is made up of distinguishable grains, usually somewhat rounded, cemented together; grains can be from .06 to 2 mm in diameter Most Sierran sandstone has tiny grains Where to see an example Folsom (map 4, 10) Buildings: state buildings at Ione (map 7, 3); Tullock mill, Knights Ferry (map 7, 24) SHALE

Characteristics Rock is made up of very fine grains, less than .06 mm in diameter 26

TA B L E S O F G E O L O G I C A L F E AT U R E S

Grains cannot be distinguished by naked eye; probably not with hand lens Where to see an example Dry Creek, west base of Oroville Table Mountain (8 mi [13 km] north of Oroville) (map 1, 4) TILL

Characteristics Jumbled mass of clay, sand, and boulders Distinguished from lahar by presence of large numbers of nonvolcanic boulders Where to see an example See “till,” table 8 TUFF

Characteristics Since tuff is deposited in layers, it is sedimentary; its source is volcanic Where to see an example See “volcanic ash and tuff,” table 6

TABLE 5

Volcanic Igneous Rocks Commonly Found in the Sierra Nevada

ANDESITE

Characteristics Medium gray Most minerals too small to be distinguished even with a hand lens; a few crystals of dark minerals may be visible Chip of rock held to light is translucent on edge Where to see an example State Hwy. 88, near Carson Spur (map 5b, 1) Tuolumne (Stanislaus) Table Mountain (latite) (map 8, 8) Devils Postpile (map 11, 2) See also “lahar” and “dome,” table 6 BASALT

Characteristics Dark colored; resembles andesite, but is usually more nearly black continued ➤ TA B L E S O F G E O L O G I C A L F E AT U R E S

27

TABLE 5 continued

Chip of rock held to light is opaque May form columns Where to see an example Honey Lake (index map, p. 43) Oroville Table Mountain (map 1, 5) Sawmill Creek (map 12, 16) Golden Trout Creek (map 14, 6) See also “lava flow,” table 6 CINDER

Characteristics Pebble-sized fragment, resembling very small furnace “clinker” Usually red or black (red results from oxidation [rusting] of iron) Where to see an example See “cone,” table 6 OBSIDIAN

Characteristics Glassy Rounded fragments chip off like glass (conchoidal fracture) Sharp; will cut flesh Generally dark colored Where to see an example Mono Craters (map 9, 28) Glass Creek flow (Obsidian Dome), off U.S. Hwy. 395 near Deadman Summit (map 9, 32) PUMICE

Characteristics Gray or yellowish gray May have many holes (vesicular) Floats on water (formed as lava froth) Where to see an example Mono Craters (map 9, 28) Devil’s Punchbowl, Mono Lake region, U.S. Hwy. 395 (map 9, 29)

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Pumice Flat, Devils Postpile National Monument (map 11, 1) Pumice Butte (map 11, 8) RHYOLITE (FELSITE)

Characteristics Light colored Fine grained; most minerals too small to be distinguished even with a hand lens; a few larger fragments of quartz, feldspar, or pumice may be visible Rock may be banded Generally very hard May ring when struck by hammer Where to see an example Silver Peak, Ebbetts Pass (map 6, 8) Highland Peak, Ebbetts Pass (map 6, 9) Wilson Butte, U.S. Hwy. 395 north of Deadman Summit (rhyolite glass) (map 9, 31) Lookout Mountain (map 9, 34) “Petroglyph Loop Trip,” near Bishop (rhyolite tuff) (map 12, 5); see also “volcanic ash and tuff,” table 6 TUFF

Characteristics Very fine grained; grains not visible under hand lens Usually light colored (microscope shows tuff to consist of very tiny pieces of volcanic glass or rock or both) Where to see an example See “rhyolite,” this table, and “volcanic ash and tuff,” table 6

TABLE 6

Volcanic Features of the Sierra Nevada

BOMB

Where to see an example Sawmill Creek lava flow, U.S. Hwy. 395 (map 12, 16) CONE

Where to see an example Lake Tahoe (cinder cone used for sewage disposal) (map 3, 3) continued ➤ TA B L E S O F G E O L O G I C A L F E AT U R E S

29

TABLE 6 continued

Black Point, Mono Lake (basaltic cinders) (map 9, 4) Paoha Island, Mono Lake (map 9, 6) Red Cones, middle fork of San Joaquin River (map 11, 5) Pumice Butte, near Mono Craters (pumice) (map 11, 8) Red Mountain, Owens Valley (cinder cone 600 ft [180 m] high) (map 12, 15) Fish Spring cinder cone (about 314,000 years old) (near map 12, 16) Headwaters of South Fork of Kern River (less than 1 million years old) (map 14, 7) Red Hill, north of Little Lake, U.S. Hwy. 395 (mined for cinders) (map 14, 10) DOME

Where to see an example Markleeville Peak, Alpine County (andesite dome) (map 6, 5) Silver Peak, Ebbetts Pass (carved from rhyolite dome) (map 6, 8) Highland Peak, Ebbetts Pass (rhyolite dome; cinder cone on one side) (map 6, 9) Jackson Butte (map 7, 8), McSorley Dome (map 7, 11), Tunnel Peak (map 7, 12), Hamby Dome (map 7, 13), Golden Gate Hill (map 7, 14), all near Mokelumne Hill (older, eroded andesite domes) Panum Crater (dome) (spines, ridges, bombs, pumice) (map 9, 27) Mono Craters (rhyolite tuff rings, domes, and flows) (map 9, 28) Glass Mountain, U.S. Hwy. 395 (obsidian) (map 9, 30) Wilson Butte, U.S. Hwy. 395 north of Deadman Summit (rhyolite) (map 9, 31) Templeton Mountain, Monache Mountain (“latite” andesite) (map 14, 8, 9) EXPLOSION PITS

Where to see an example Paoha Island, Mono Lake (map 9, 6) Inyo Craters, near Mammoth Mountain, U.S. Hwy. 395 (map 9, 45) LAHAR (VOLCANIC MUD FLOW)

Where to see an example Carson Spur, State Hwy. 88 (map 5b, 1) Thimble Peak, State Hwy. 88 (map 5b, 2) Two Teats, Mount Morrison 15-minute quadrangle (about 3 million years old) (map 9, 37)

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LAVA FLOW

Where to see an example Oroville Table Mountain, Butte County (olivine basalt) (map 1, 5) Dardanelles, Sonora Pass, State Hwy. 108 (map 6, 11) Columns of the Giants, Sonora Pass, State Hwy. 108 (columnar structure, 150,000 years old) (map 6, 12) Sonora Peak (map 6, 13), Leavitt Peak (map 6, 14) (sources of Tuolumne Table Mountain flows) Tuolumne (Stanislaus) Table Mountain, especially accessible at junction of State Hwys. 108 and 120 (map 8, 8) Glass Creek obsidian flow (rhyolite glass; 150 to 200 feet thick; banding common) (map 9, 33) San Joaquin Mountain, John Muir Trail, near Ritter Range (columnar structure, pumice) (map 9, 35) Piles at Devils Postpile National Monument (columnar structure; parts of flow show pillow structure where lava flowed into water) (map 11, 2) Mount McGee, Deadman Pass (2 to 4 million years old) (map 11, 12) San Joaquin River headwaters, especially near Pincushion Peak (map 11, 15) and Saddle Mountain (map 11, 16), Kaiser Peak quadrangle (2 to 4 million years old) Sawmill Creek, U.S. Hwy. 395 (spongy appearing lava, bombs) (map 12, 16) Golden Trout Creek, south of Mount Whitney (map 14, 6) (columnar structure) VOLCANIC ASH AND TUFF (REMNANTS OF NUÉE ARDENTE )

Where to see an example (landscape features) Buena Vista Peak (map 7, 16) and Valley Springs Peak (map 7, 15) near Valley Springs, Amador County Altaville quarry east of Altaville on road to Murphys (map 7, 18) Sotcher Lake, Devils Postpile National Monument (map 11, 3) Reds Meadow Ranger Station, Devils Postpile National Monument (welded tuff; very hard; sealed together as it cooled) (map 11, 4) Exposures on U.S. Hwy. 395 near Bishop (map 12, 5); along shores of Crowley Lake (map 12, 1); on Owens River (map 12, 2) and Rock Creek (map 12, 3) (petroglyphs of “Petroglyph Loop Trip” carved in 760,000-year-old tuff) Where to see an example (buildings) Alpine County courthouse, Markleeville (map 6, 6) Silver Mountain city jail, State Hwy. 4 (remnants only) (map 6, 7) IOOF Hall, Jackson (map 7, 7) continued ➤

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TABLE 6 continued

Town of Mokelumne Hill (most stone buildings) (map 7, 9) Prince and Garibardi store, Altaville (map 7, 19) Town of Angels Camp (most stone buildings; good example is Lake’s Hotel) (map 7, 20) Town of Murphys (many stone buildings) (map 8, 2) Douglas Flat (stone buildings) (map 8, 3) VOLCANO

Where to see an example Mount Rose, Nevada (map 3, 2) Negit Island, Mono Lake (map 9, 5) Mammoth Mountain, near U.S. Hwy. 395 (map 11, 6)

TABLE 7

Features of Sierra Nevada Glaciers

BERGSCHRUND

Characteristics Crack in ice parallel to head wall of glacier Probable origin Developed near head wall by meltwater trickling through head wall in relief of pressure Where to see an example Mount Conness (map 9, 7) Mount Dana (map 9, 12) Mount McClure (map 9, 38) Mount Lyell (map 9, 39) Palisades (map 12, 13) Most Sierran glaciers CREVASSE

Characteristics Crack in ice, often but not necessarily parallel to head wall Probable origin Developed when ice breaks in zones where one part is traveling faster than another or where there are obstructions beneath ice

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Where to see an example Most Sierran glaciers ROCK GLACIER

Characteristics Corrugated mass of angular rock near cirque, shaped like glacier Probable origin Mixture of ice and rock, moving like glacier, in areas not now cold enough or wet enough for glacier to form Where to see an example Cirque between San Joaquin Mountain and Two Teats (map 9, 36) Sherwin Canyon (map 11, 9) Mount Gabb (map 11, 18) Mount Tom (map 12, 6) Eastern side of Sierra

TABLE 8A

Features of Depositional Glaciers in the Sierra Nevada

ERRATIC

Characteristics Markedly different type of rock lying in terrain not its source Probable origin Boulder carried in or on ice, left when ice melts Where to see an example Faith Valley (granite on lava) (map 6, 2) June Lake (map 9, 26) Starr King Meadows (map 10, 7) Chiquito Creek (granite on lava) (map 10, 10) Moraine Dome (one type of granite on another) (map 10, 21) Sentinel Dome (map 10, 23) Glacier Point (metamorphic rock on granite) (map 10, 24) Cathedral Rocks (map 10, 26) Balloon Dome (map 11, 14) Twin Lakes near Kaiser Peak (granite on calcareous rock) (map 11, 19) Rock Creek (map 12, 4) continued ➤

TA B L E S O F G E O L O G I C A L F E AT U R E S

33

TABLE 8A continued

Humphreys Basin (map 12, 8) Bighorn Plateau (map 14, 1) KAME TERRACE

Characteristics Mound of poorly sorted sand and gravel forming ridge along glacier edge Probable origin Deposited in channels of streams at edge of ice Where to see an example Junction of Sonora Pass Hwy. (State Hwy. 108) and U.S. Hwy. 395 (map 6, 15) MORAINE (TERMINAL, LATERAL, MEDIAL)

Characteristics Long hills of unsorted sand, gravel, clay, and boulders; ridge form is distinctive; some boulders may be faceted Probable origin Deposited at sides (lateral), in center (medial), or end (terminal) of glacier; medial most commonly forms where two glaciers join Where to see an example Twin Lakes, Matterhorn Peak 15-minute quadrangle (map 9, 2) Lee Vining Canyon (map 9, 10) Gibbs Canyon (map 9, 11) Moraines enclose Walker Lake, at foot of Bloody Canyon (map 9, 19) Sawmill Canyon (map 9, 20) Convict Lake (map 11, 11) McGee Creek Canyon (map 11, 13) Lateral moraine near State Hwy. 168, Huntington Lake 15-minute quadrangle (map 11, 21) Modern glaciers have several small terminal moraines: Dana (3 or 4) (map 9, 12); Kuna (6 or 7) (map 9, 23); Lyell (map 9, 39); Palisades (map 12, 13) MORAINE-DAMMED LAKE

Characteristics Has natural dam made of till Probable origin Water held in by ridge of till

34

TA B L E S O F G E O L O G I C A L F E AT U R E S

Where to see an example Donner Lake (map 3, 1) Fallen Leaf Lake (map 3, 5) Gilmore Lake (map 3, 6) Walker Lake (map 9, 19) Grant Lake (map 9, 24) June Lake (map 9, 26) Convict Lake (map 11, 11) See also “till” OUTWASH PLAIN

Characteristics More or less stratified deposit in valley beyond moraine Probable origin Glacial meltwater carrying fragments of eroded moraine Where to see an example Sand Meadows (map 9, 15) PERCHED BOULDER

Characteristics Pedestal of local rock capped by erratic May resemble mushroom See also erratic (earlier in this table) Also called glacial table Probable origin Local rock protected from weathering by more durable erratic Where to see an example Parker Creek (map 9, 21) Starr King Meadows (map 10, 7) Chiquito Creek (map 10, 10), on trail to Chiquito Pass Upper Yosemite Falls (map 10, 14) Moraine Dome (map 10, 21) TILL

Characteristics Jumbled mass of clay, sand, and boulders; some boulders may be 25 ft (7.6 m) in diameter, some may be faceted; distinguished from volcanic mud flow (lahar) by presence of large numbers of nonvolcanic boulders continued ➤ TA B L E S O F G E O L O G I C A L F E AT U R E S

35

TABLE 8A continued

Probable origin Deposited by glacial ice on bottom or in moraine Where to see an example Around Lake Tahoe (map 3) Moraines on east side of Sierra: near Bridgeport (map 9, 1),Walker Lake (map 9, 19), Reversed Creek (map 9, 25), Convict Creek (map 11, 11), McGee Creek Canyon (map 11, 13), Rock Creek (map 12, 4), Pine Creek (map 12, 14) In Bloody Canyon (map 9, 18) In Sawmill Canyon (map 9, 20) Yosemite National Park (map 10) Around Lake Mary (map 11, 7) Most Sierran passes

TABLE 8B

Features of Erosional Glaciers in the Sierra Nevada

ARÊTE

Characteristics Grat, comb, knife-edged ridge are synonyms Steep, sharp rock ridge between adjacent cirques Probable origin Quarrying by glacier in cirque Where to see an example Mount McClure (map 9, 38) Mount Lyell (map 9, 39) Ritter Range (map 9, 40) Mount Humphreys (map 12, 7) South of Mount LeConte (map 12, 12) North Palisades (map 12, 13) Kaweah Crest (map 13, 6) Septum between Mount Russell (map 14, 3) and Mount Whitney (map 14, 4) AVALANCHE CHUTE

Characteristics Slick, steep, U-shaped groove barren of vegetation Probable origin Snow avalanches, following same path year after year

36

TA B L E S O F G E O L O G I C A L F E AT U R E S

Where to see an example Sequoia National Park (map 13) Bearpaw Meadows, High Sierra trail (map 13, 4) Hamilton Lakes (map 13, 5) Mount Whitney (map 14, 4) Mount Hitchcock (map 14, 5) CHAIN LAKES

See glacial stairway CHATTER MARK

Characteristics Crescentic gouges and fractures, deeper on downstream (down-ice) end Probable origin Impact pressure of ice Where to see an example Grant Lake (map 9, 24) Evolution Basin, near Sapphire Lake (map 12, 10) Mount Huxley (map 12, 11) CIRQUE

Characteristics Kar, cwm, botn, corrie, hoyo, are synonyms in other languages Bowl-shaped depression in mountain side; generally backed by steep cliff Probable origin Scouring of glacial ice at head of glacier; plucking of head wall Where to see an example Throughout Sierra, in high country CIRQUE LAKE (TARN)

Characteristics Lake in cirque (see cirque) Probable origin In cirque eroded by glacier Lake may be final remnant of glacier, or may occupy older glacial cirque continued ➤

TA B L E S O F G E O L O G I C A L F E AT U R E S

37

TABLE 8B continued

Where to see an example Gold Lake, on Feather River (map 2, 1) Kuna Crest (map 9, 16) Thousand Island Lake (map 9, 41) Garnet Lake (map 9, 42) Mount Humphreys (map 12, 7) Humphreys Basin (map 12, 8) Crystal Lake (map 13, 9) and Eagle Lake, near Mineral King (map 13, 10) Throughout high country COL (PASS)

Characteristics Low saddle in glacial ridge opposite two cirques Probable origin Erosion by the heads of two glaciers, coalescing to destroy part of arête Where to see an example Mono Pass, above Bloody Canyon (map 9, 17) COMB

See arête CYCLOPEAN STAIRS

See glacial stairway GIANT’S KETTLE

See glacial moulin work GIANT’S STAIRCASE

See glacial stairway GLACIAL MOULIN WORK

Characteristics Pothole, giant kettle Cylindrical holes in rock of glacier floor Probable origin Grinding of rock by boulder or pebble, in glacial eddies and vortices of water within ice

38

TA B L E S O F G E O L O G I C A L F E AT U R E S

Where to see an example End of Tuolumne Meadows, Yosemite National Park (map 9, 14) GLACIAL POLISH

Characteristics Shiny surface on rock; if weathered, shine may be worn off in spots All minerals shine Probable origin Polishing by finely ground rock in glacial ice Where to see an example Mokelumne Wilderness Area (map 5b, 3) Lembert Dome, Tuolumne Meadows, Tioga Pass Road (map 9, 13) Bloody Canyon (map 9, 18) Yosemite National Park; Pywiack Dome (map 10, 3), Tenaya Canyon (map 10, 6), base of El Capitan (map 10, 12), Three Brothers (map 10, 13), Washington Column (map 10, 17), walls near Mirror Lake (map 10, 18), Mount Broderick (map 10, 19), back of Liberty Cap (map 10, 20), upper Merced Canyon, above Nevada Fall (map 10, 22), Union Point (map 10, 25) Recess Peak (map 11, 17) Kaiser Ridge (map 11, 20) Evolution Basin (map 12, 9) Hamilton Lakes (map 13, 5) Big Arroyo (map 13, 8) Kern River Canyon (map 13, 11) Throughout high country GLACIAL STAIRWAY

Characteristics Glacial staircase, cyclopean stairs, giant’s staircase, glacial step; paternoster lakes are lakes in glacial stairway Series of flattish valley areas, commonly with lakes (paternoster lakes, chain lakes, glacial step lakes) connected to one another by steep areas commonly with waterfalls U-shaped valley and glacial marks indicate glaciation Probable origin Scouring of glacier bed Where to see an example Faith (map 6, 2), Hope (map 6, 1), and Charity (map 6, 3) Valleys continued ➤

TA B L E S O F G E O L O G I C A L F E AT U R E S

39

TABLE 8B continued

Yosemite Valley (map 10) Sixty Lake Basin (map 13, 2) Black Rock Pass (map 13, 7) GLACIAL STEP LAKES

See glacial stairway GRAT

See arête GROOVES

See scratches HANGING VALLEY

Characteristics Tributary valley much higher than main valley, usually marked by steep cliff, perhaps waterfall (hanging waterfall) Probable origin Thinner tributary glacier met main glacier at level where tops were even, bottoms not; when ice melted, channel of tributary glacier was left much higher Where to see an example Yosemite Valley, many falls (map 10) Hetch Hetchy Valley, Tueeulala Falls (map 10, 1) Evolution Basin (map 12, 9) HANGING WATERFALLS

See hanging valley KNIFE-EDGED RIDGE

See arête MATTERHORN (HORN)

Characteristics Pyramidal, steep mountain peak in glaciated area Probable origin Erosion at the heads of three or more converging glaciers

40

TA B L E S O F G E O L O G I C A L F E AT U R E S

Where to see an example Matterhorn Peak (map 9, 3) Mount Huxley (map 12, 11) PASS

See col PATERNOSTER LAKES

See glacial stairway POLISH

See glacial polish POTHOLE

See glacial moulin work ROCHE MOUTONNÉE

Characteristics Rocky outcrop in glacial landscape, rounded on one side, irregular on other Probable origin Erosion by overriding ice, smoothing upstream side by abrasion, plucking (quarrying) downstream side Where to see an example Glen Alpine Valley (map 3, 7) Desolation Valley (map 3, 8) Tuolumne Meadows (map 9, 14) Mount Broderick (map 10, 19) Liberty Cap (map 10, 20) Blaney Meadows (map 11, 22) SCRATCHES, GROOVES

Characteristics Long lines or indentations in rocks Probable origin Abrasion of glacial walls and floor by rocks embedded in ice Where to see an example Bloody Canyon (map 9, 18) continued ➤

TA B L E S O F G E O L O G I C A L F E AT U R E S

41

TABLE 8B continued

Grant Lake (map 9, 24) Yosemite Valley (map 10) Cathedral Pass (map 10, 5) Royal Arches (map 10, 15) Evolution Basin (map 12, 9) Hamilton Lakes (map 13, 5) Kern River Canyon (map 13, 11) TARN

See cirque lake U-SHAPED VALLEY

Characteristics Has horseshoe shape in cross section Probable origin Eroded by glacier, usually modifying stream valley Where to see an example Yosemite Valley (map 10) Hetch Hetchy Valley (map 10, 2) Evolution Basin (map 12, 9) Pine Creek Canyon (map 12, 14) Kern River Canyon (map 13, 11)

42

TA B L E S O F G E O L O G I C A L F E AT U R E S

MAPS OF GEOLOGICAL SIGHTS Tehama

Index map showing areas covered by maps 1–14. Locations shown on these maps by no means exhaust the places in the Sierra where you might find the feature or rock listed. Some were chosen so as to be scattered through the range. Some were chosen because they are accessible by automobile (parking was considered); others are accessible only by foot.

Lassen Honey Lake

Plumas

2 Butte Oroville Reservoir

Sier ra

3

1 Sutter

Nevada Placer

Yu b a

N E V A D A Lake Tahoe

El Dorado

Sacramento

6

5B

5A

4

Alpine

Amador

9 Calaveras San Joaquin

Mono

Tuolumne

Yosemite NP

7 Stanislaus

Mono Lake

11 8

Mer ced

Mariposa

12

10

Madera

Ki n g s Cyn NP

Inyo

Fr esno S e qu oi a NP

13 Kings

N

0 0

50 miles 50 kilometers

Tu l a r e

14

Map 1

121°30´

121°15´

To Quincy

Riv e

r

N

2

We st B

32

Fe ath er

Butte Cre ek

Big Chi

co

ranch Feather River

Tehama Co Butte Co

For k

40°00´

Cre ek

1

P lu

Magalia

m

3

a o

e

C

tt

s

u

Pulga

B

To Chico

C o

Paradise

er R ive r Feat h

5

le F or k

Oroville Reservoir

4

M idd

191

To Chico

70

Dry Creek

39°45´

99 70

N

Oroville

39°30´

5 miles

0

Feather River

0

Gridley

1. 2. 3. 4. 5.

5 kilometers

Red Hill: peridotite Big Chico Creek: conglomerate Pulga: peridotite Dry Creek: shale Oroville Table Mountain: lava flow, basalt

To Marysville

121°00´

40°00´

1. 2. 3. 4. 5.

Gold Lake: cirque lake To Quincy Yuba River: slate Near Camptonville: gabbro, laterite Near North San Juan: calcareous rock Malakoff Diggins State Historic Park: conglomerate

rk le Fo Midd

r the Fea

Map 2

120°45´

N 5 miles

0

5 kilometers

0 70

89

er Riv

1

Pl Yu

um

ba

as

C

C

o S

i

r er

a

C

Gold Lake

o

o

To Sierraville Downieville

Sierra City o

iver ba R k Yu C

39°30´

d va

S

3

a

ie

C

rr

o

a

or NF

2

N

e

Camptonville 49

iver Yuba R North 5 Bloomfield

k Middle For

4

North San Juan

er S Fork Yuba Riv To Nevada City

20

80

Map 3

1. 2. 3. 4. 5. 6. 7. 8.

Sierra Co Nevada Co 89

Donner Lake: moraine-dammed lake Mount Rose: volcano Near Lake Tahoe: cone Kingsbury grade: feldspar, mica, pegmatite Fallen Leaf Lake: moraine-dammed lake Gilmore Lake: moraine-dammed lake Glen Alpine Valley: roche moutonnée Desolation Valley: roche moutonnée, granite

To Reno 27

To Reno

80

Truckee

2

Mt. Rose

1

Nevada Co Placer Co

Donner Lake

3 89

Kings Beach

28

N

Tahoe City

5 miles

0

5 kilometers

0

395

Nevada

California

ve r Truckee Ri

39°15´

Carson City

Lake Tahoe

50

Meeks Bay

Placer Co El Dorado Co

39°00´

28

89

4

19

50

Fallen Leaf Lake 5

88

South Lake Tahoe

6

D E S O L AT I O N VA L L E Y

7

4

8

To Placerville 120°15´

50

89

To Markleeville

39°15´

Map 4

121°00´

River

a ub

20 49

S Fork

Y

121°15´

1

Nevada City

Rough and Ready

Grass Valley

2 20

3

Wo lf Cr e ek

Yu b a C o Nevada Co

174

N

4 5

Colfax 5 miles

0

6

5 kilometers

0

80

ca nR ive r

49

kA me ri

Be ar R iver

39°00´

or

To Marysville N

F

7 8

Auburn

7

9

Lincoln

d d le Mi

Fo

er Riv can i r e rk Am

Cool

65

49

To Coloma

80

Roseville 38°45´ Placer Co Sacrame nto Co

Folsom

Folsom Lake 10

Am er i

c

To Sacramento er Riv an 50

To Sacramento

1. Near Nevada City: pyroxene, amphibole 2. Rough and Ready: gabbro 3. Gold Run: conglomerate 4. Rollins Lake: serpentine 5. Bear River: quartz 6. South Fork Wolf Creek: chert 7. Near Lincoln: clay 8. American River Canyon: greenstone 9. Cool-Cave Valley quarry: calcareous rock 10. Folsom: sandstone buildings

Map 5b

Map 5a 20

89

ive r

50

R ar Be

39°15´

me r kA For

To Placerville 38°45´

River ican

1

Silver Lake

1. Chili Bar mine: slate 2. Diamond Springs quarry: calcareous rock 3. Cosumnes copper mine: amphibole

Do

El

ra

A

d ma

B ea r

iver nR a c i r Ame Middle Fork 39°00´

ado Co

River

3

elu Mok

N Fork

38°30´ Dor El

2

Co

or

Riv er

88

Caples Lake

Co do

ne

N

80

s Calavera 4 Salt

m

Co

Springs Reservoir

N 4

Tu

o

lu

m

n

e

C

To Angels Camp

5 kilometers

0

o

5 miles

0

S Fork Amer

N

iver ican R 0

1

0 49

Placerville

Diamond Springs 49

38°45´

50

2

To Lake Tahoe

Mi d

nes River sum o C ork Cosumnes Riv NF er ork eF dl 120°45´

Fairplay

3

5 miles 5 kilometers

38°15´

1. Carson Spur: andesite, lahar 2. Thimble Peak: lahar 3. Mokelumne Wilderness Area: glacial polish 4. Garnet Hill: gneiss

120°15´

W

89

1. Hope Valley: glacial stairway 2. Faith Valley: glacial stairway, erratic boulders 3. Charity Valley: glacial stairway 4. Grover Hot Springs State Park: 38°45´ granite 5. Markleeville Peak: dome 6. Alpine County courthouse, Markleeville: volcanic ash and tuff 7. Silver Mountain city jail: volcanic ash and tuff To Carson

88

r Fork Carson Rive

1 88

89

4 2

Map 6

119°45´

To Carson City

6

3

Markleeville 5

City

89

rs Ca

alke W Fork W

EF or k

7

ve r r Ri

9

River on

8 4

Tu

Al

pi 11 ne ol C u Co mn o e

Al

pin

o Tu

Co

lum

ne

Co Mono

e

Alpine

Co

Mokelumne Riv er 10 To Angels Camp

395

Co

Dardanelle Mi ddl 12 e Fo rk S 108 tanis laus River To Sonora

13

15

To Bridgeport 14

8. Silver Peak: dome, rhyolite 9. Highland Peak: dome, rhyolite, cinder cone 10. Cape Horn: slate 11. Dardanelle: lava flow 12. Columns of the Giants: lava flow 13. Sonora Peak: lava flow 14. Leavitt Peak: lava flow 15. Sonora Junction: kame terrace 16. Bond Pass: hornfels, quartzite, schist

38°15´ N 5 miles

0 16

0

Yosemite Na t i onal Par k

5 kilometers

119°30´

Map 7

120°45´

Plymouth 16

4

Volcano 49

Carbondale 104

Amador City Sutter Creek

A

Ione 2

7

Jackson

2

16

12

12

l

ra

s

Co

n m

veras River Cala

Mokelumne Hill

13 10

38°15´

14

26

15

Ca

e av

Co

or

9 11

Cannondale Reservoir

u kel Mo

8

Pardee Reservoir

88

d ma

88

2 3

5 6

eR iver

124

1

San Andreas

Valley Springs

N

sl

Co

ol

ni

um

ta

Tu

au

s

C

o

121°00´

ne

S

Sta n Ri isla ve r

5 miles 0 1. Carbondale mine: lignite 17 2. Ione clay pits: clay 5 kilometers 0 New Hogan 3. Ione: sandstone buildings, Reservoir 49 lignite mine To Murphys 4. Near Volcano: calcareous rock 5. Volcano: buildings of calcareous rock 19 18 6. Indian Grinding Rock State Historic Park: Altaville calcareous rock 20 Angels 7. IOOF Hall: volcanic ash and tuff 4 Camp 8. Jackson Butte: dome 9. Mokelumne Hill: volcanic ash and tuff buildings 21 New 10. Mines: quartz crystals Melones 11. McSorley Dome: dome Lake Copperopolis 12. Tunnel Peak: dome 22 23 13. Hamby Dome: dome 14. Golden Gate Hill: dome us 15. Valley Springs Peak: To Stockton volcanic ash and tuff 16. Buena Vista Peak: volcanic Tulloch ash and tuff, lignite Reservoir 17. Kentucky House: calcareous rock 18. Altaville quarry: volcanic ash and tuff 120 19. Prince and Garibardi store: volcanic ash and tuff 24 Knights 20. Lake’s Hotel: volcanic ash and tuff Ferry 21. Carson Hill mine: amphibole To Oakdale 22. Near Copperopolis: diorite 23. Near Copperopolis: schist 37°45´ 24. Tullock Mill: sandstone

3

us Riv er

Co

Fo rk

Ca

Sta n

la

2

Vallecito

N

4

s 5 S Fork Stanislau

r Rive

Columbia

6 108

Sonora

108

7

Jamestown

8

Map 8

120°15´

isla

ve

1

ra

Murphys

s

4

9

Jacksonville (site)

1. Mercer’s Cave: calcareous rock 2. Murphys: buildings of volcanic ash and tuff 3. Douglas Flat: buildings of volcanic ash and tuff 4. Near Vallecito: amphibole 5. Moaning Cave: calcareous rock 6. Columbia quarry: calcareous rock 7. Near Jamestown: greenstone 8. Tuolumne Table Mountain: andesite, lava flow 9. Near Jamestown: quartz 10. Bower Cave: calcareous rock 11. Near Coulterville: greenstone 12. Near Coulterville: quartz, schist 13. Near Coulterville: mica (mariposite) 14. Mary Harrison mine: mica (mariposite) 15. French Mills quarry: schist 16. Near Hornitos: gabbro 17. Bagby grade: serpentine

r Tuolumne Rive 120

N

49

5 miles

0

Don Pedro Reservoir

Tu

u ol

mn

Co

e

M

ip ar

os

Co

a

5 kilometers

10 11

12

13 15 14

132

St

an

i

sl

r Me

s au

ce

d

Coulterville

Lake McClure

Co

17

Bagby

Co

19

Merced Falls

Me

37°30´ 16

18

rce d Ri ver

La Grange

37°45´

N Fork M erced River

0

49

Hornitos

18. Josephine mine: mica (mariposite) 19. Hunter Valley: chert 20. Mount Ophir quarry: schist 120°15´ 21. Agua Fria quarry: slate

20

Mariposa 140

21

To Merced 120°00´

Map 9

119°15´

119°00´

r Ri ver

22

E Walke

Fales Hot Springs

N E V A D A

395

38°15´

Bridgeport 1

N 5 miles

0

2

5 kilometers

0

395

M ad

3

er um

Co

ol

a

Tu ne

Co

4

5 6

Mono Lake 38°00´

7

Lee Vining

120

8

10

9

Tuolumne 1 3 Meadows 14

11

12

27 19

15

18 16 17

Yo semite Na t i onal Pa r k C

M

a

ri M

p a

o d

s e

C

120

21 24

28

22 23

29 26

To 3 0

31

o

a ra

20

25 June o

Lake

38 39

41 42

35 36 37

32

Owens River

33

34

To Bishop 43

45

40 44

395

Map 9 1. Near Bridgeport: till 2. Twin Lakes: moraine 3. Matterhorn Peak: matterhorn 4. Black Point: cone; many tufa towers in and along lake 5. Negit Island: volcano 6. Paoha Island: cone, explosion pits 7. Mount Conness: bergschrund 8. Ellery Lake: hornfels 9. Tioga Lake: hornfels 10. Lee Vining Canyon: moraine 11. Gibbs Canyon: moraine 12. Mount Dana: bergschrund, terminal moraine 13. Lembert Dome: feldspar, porphyry, glacial polish 14. Tuolumne Meadows: glacial moulin work, roche moutonnée 15. Sand Meadows: outwash plain 16. Kuna Crest: cirque lake 17. Mono Pass: hornfels, col 18. Bloody Canyon: till, glacial polish, scratches, grooves 19. Walker Lake: moraine, moraine-dammed lake, till 20. Sawmill Canyon: moraine, till 21. Parker Creek: perched boulders 22. Mount Lewis: hornfels 23. Kuna Glacier: terminal moraine 24. Grant Lake: chatter marks, scratches, grooves 25. Reversed Creek: till 26. June Lake: erratic boulders, moraine-dammed lake 27. Panum Crater: dome, obsidian plug, pumice 28. Mono Craters: dome, obsidian, pumice 29. Devil’s Punchbowl: pumice 30. Glass Mountain (16 miles due east of Hwy 395): dome 31. Wilson Butte: rhyolite, dome 32. Obsidian Dome: obsidian 33. Glass Creek: lava flow 34. Lookout Mountain: rhyolite, obsidian 35. San Joaquin Mountain: lava flow 36. Cirque between 35 and 37: rock glacier 37. Two Teats: lahar 38. Mount McClure: bergschrund, arête 39. Mount Lyell: bergschrund, arête, terminal moraine 40. Ritter Range: arête 41. Thousand Island Lake: cirque lake 42. Garnet Lake: cirque lake 43. Shadow Canyon: schist 44. Minarets Lookout: hornfels 45. Inyo Craters: explosion pits

Map 10

119°45´

1

119°30´

Hetch Hetchy Reservoir

Tuolumne River 2 Tuo

lum

ne

C

o

12

3

4 5

120

120

6

37°45´

To Mariposa

iver Merced R

7

See Inset

El Portal 8

9

140

SF or k

Mer c ed

Yosemite Na t i onal Par k

41

C

M

River

a

p

ri

M

o a

s d

o

a C e

o

ra

N

37°30´ 0 0

5 miles 5 kilometers

YO

10

To Oakhurst

I SEM

VA L L E Y

TE Yosemite 14 Village 12

17

15

16

13

To Big Oak Flat

25 24

11

6

18

21

19 20 22

23 26

To Wawona

0

2 miles

0

2 kilometers

7

Map 10 1. Tueeulala Falls: hanging valley 2. Hetch Hetchy Valley: U-shaped valley 3. Pywiack Dome: glacial polish 4. Cathedral Peak: feldspar, porphyry 5. Cathedral Pass: glacial scratches, grooves 6. Tenaya Canyon: glacial polish 7. Starr King Meadows: perched boulders, erratic boulders 8. Geological Exhibit: phyllite, chert 9. El Portal: diorite 10. Chiquito Creek: erratic boulders, perched boulders 11. The Rockslides: diorite 12. El Capitan: glacial polish 13. Three Brothers: glacial polish 14. Upper Yosemite Falls: perched boulders 15. Royal Arches: glacial scratches, grooves 16. Indian grinding rocks: granite 17. Washington Column: glacial polish 18. Mirror Lake: glacial polish 19. Mount Broderick: glacial polish, roche moutonnée 20. Liberty Cap: glacial polish, roche moutonnée 21. Moraine Dome: erratic boulders, perched boulders 22. Upper Merced Canyon: glacial polish 23. Sentinel Dome: erratic boulders 24. Glacier Point: erratic boulders 25. Union Point: glacial polish 26. Cathedral Rocks: erratic boulders

Map 11

119°00´

1

Devils Pos t p i l e Na t i onal Monu ment

2

203

3

6

4

7 Mo

10

Co

12 13

o C

ra o

e

n

d

s

a

e

M

15

ork SF

16

Sa

n

ek Mono Cre

in qu

17

R

ive r

Mt. Abbot 18

Inyo Co

Lake Thomas A. Edison

a Jo

N

5 miles

0 0

Crowley Lake

11

8

Fr

14

10

9 no

395

o

C

Jo an

River uin aq

eF or k Midd l

37°30´

S

5

Mammoth Lakes

5 kilometers 19 20

Florence Lake

168

37°15´

21

Huntington Lake Big Creek

22

To Fresno 23

1. 2. 3. 4. 5. 6. 7. 8. 9.

Dinkey Creek

Shaver Lake

24 25

Pumice Flat: pumice Devils Postpile: basalt, lava flow Sotcher Lake: volcanic ash and tuff Reds Meadow: volcanic ash and tuff Red Cones: cone Mammoth Mountain: volcano Lake Mary: till Pumice Butte: pumice, cone Sherwin Canyon: rock glacier 119°15´

10. West of Convict Lake: quartzite, porphyry 11. Convict Lake: moraine, till, morainedammed lake, U-shaped canyon 12. Mount McGee: lava flow 13. McGee Canyon: moraine, till 14. Balloon Dome: erratic boulders 15. Pincushion Peak: lava flow 16. Saddle Mountain: lava flow 17. Recess Peak: glacial polish 18. Mount Gabb: rock glacier 19. Twin Lakes: amphibole, feldspar, pyroxene, gneiss, gabbro, erratic boulders 20. Kaiser Ridge: glacial polish 21. Huntington Lake: lateral moraine 22. Blaney Meadows: roche moutonnée 23. Miningtown Meadows: quartzite 24. Grouse Lake: quartzite 25. Dinkey Dome: quartz

Crowley 1. 2. 3. 4. 5. 6. 7. 8.

2

3 395

4

Map 12

118°30´

1 Lake

Crowley Lake: volcanic ash and tuff Owens River: volcanic ash and tuff Rock Creek: volcanic ash and tuff Rock Creek: erratic boulders, till Loop Trip: volcanic ash and tuff, rhyolite Mount Tom: rock glacier Mount Humphreys: arête, cirque lake Humphreys Basin: erratic boulders, cirque lake

Mono Co Inyo Co

5

Owens River

Bishop 6

7

N

8

37°15´ 5 miles

0

395

5 kilometers

0

9

In

10 11 Fr

12

es

Big Pine yo

Co

14 no

Co

13

King s Canyon Na t i onal Par k

9. Evolution Basin: chatter mark, glacial polish, hanging valley, scratches, grooves, U-shaped valley 10. Sapphire Lake: chatter mark 11. Mount Huxley: chatter mark, matterhorn 12. South of Mount Le Conte: arête 13. Palisades: bergschrund, terminal moraine, arête 14. Pine Creek Canyon: till, U-shaped valley 15. Red Mountain: cone 16. Sawmill Creek: basalt, lava flow, bomb Nearby: Fish Spring cinder cone

Tinemaha Reservoir

15

16

To Lone Pine

Map 13

118°45´

180

118°30´

Ki n g s Canyon Na t i onal Par k

1

To Fresno Kings River

2

36°45´

Fresno Co Tular e Co

Ro a

rin n Ker

ver g Ri

River

3 4

5 6

River eah Kaw

36°30´

7

Mineral King

198

SF

or

kK awe ah Ri ve

8 9

Three Rivers

S e qu oi a Na t i onal Par k

10

11

12

r ern River tl e K Lit

Boyden Cave: calcareous rock Sixty Lake Basin: glacial stairway Crystal Cave: calcareous rock Bearpaw Meadows: avalanche chute Hamilton Lakes: avalanche chute, glacial polish, scratches, grooves 6. Kaweah Crest: arête 7. Black Rock Pass: glacial stairway 8. Big Arroyo: glacial polish 9. Crystal Lake: cirque lake 10. Eagle Lake: cirque lake 11. Kern River Canyon: glacial polish, scratches, grooves, U-shaped valley 12. Clough Cave: calcareous rock 1. 2. 3. 4. 5.

N 0 0

5 miles 5 kilometers

36°15´

118°15´

Map 14

118°00´

1

2

395

Lone Pine 3 4

N

5

5 miles

0

S e qu oi a Na t i onal Par k

5 kilometers

36°30´

yo C

la

o

re C

7

Tu

6

In

Golden Tr o

ut C ree k

0

o

7 8

395

or k SF

36°15´

5. 6. 7. 8. 9.

ive r

R

1. 2. 3. 4.

rn Ke

9

Bighorn Plateau: erratic boulders Alabama Hills: granite Mount Russell: arête Mount Whitney: arête, avalanche chute, granite Mount Hitchcock: avalanche chute Golden Trout Creek: basalt, lava flow South Fork Kern River: cones Templeton Mountain: dome Monache Mountain: dome

36°00´ 10

10. Red Hill: cone

To Mojave

Little Lake

CHAPTER 1 GEOLOGY: OF TIME AND ROCKS

Overleaf: The Whitney group of peaks, the Sierra Nevada’s highest, towering more than 14,000 ft (4,267 m) in elevation. Mount Whitney is the bulky one near the center. During the Great Ice Age, Whitney’s crest was above the ice, but its sides were not.

GEOLOGY IS THE study of the Earth. Its ultimate purpose is to discover all there is to know about what the Earth is made of, how it is arranged, and how it got that way. The reconstruction of Earth’s history is one of geology’s principal aims: the story of the Earth itself through time and of all its living creatures. Because the Earth is one huge rock, it is from rocks that we have learned what we know about Earth. Even though human use of the Earth’s resources is as old as humans themselves, geology, like many sciences, dates back only to the Renaissance. As a separate branch of study, it is younger than that; the word “geology” is only about two centuries old. Geologists work with the techniques of many other sciences, together with liberal borrowings from everyday life, a heavy measure of logic, a wild imagination, and a large sprinkling of common sense. Geologists use inductive reasoning, as does a detective, searching the Earth for clues that can be fitted together to make a reasonable story. Almost never can they know for sure that their reasoning is correct. Their evidence is always circumstantial. Their culprits do not confess. Their witnesses are mute stones that cannot be interrogated, yet the stones reveal much. Geology lacks the very hallmark of science: it can rarely be tested in the laboratory to obtain repeatable results. We have but one Earth; we cannot create a new one to check theories of its creation. For this and other reasons, geology is still principally a science of observation and deduction, not experimentation. In spite of its dependence upon other sciences, geology is uniquely independent. Although it borrows freely, it has a tool of its own that sets it apart. This is a way of thinking that is different from the way a chemist, a physicist, or even a biologist thinks, and that is deeply involved with time. Scarcely a statement made in geology does not take time into account. It is now urgent that geologic time be consciously considered in our everyday lives. We have to consider the long reaches — not only yesterday’s time, but tomorrow’s as well. For example, knowledge of geology must be used to find ways to dispose of the nuclear waste now piling up in many nations of the world. It is extremely dangerous and must be disposed of in such a way that the people of Earth will be protected from it for a quarter of a million years, until its radioactive clock has run down.

GEOLOGY: OF TIME AND ROCKS

63

Telling a Rock’s Age Recently, we have found means to tell the age of a fossil, rock, or past event in actual years — partly by using a radioactive clock embedded in the rock itself. Of the many methods used to count the years past, radioactivity is the most useful. It involves calculating the rate of decay of radioactive elements and measuring minute quantities of isotopes of certain elements. For example, one method assumes that uranium, at the time the uraniumbearing mineral crystallized, contained no lead. As time passes, the uranium decays through a series of intermediate products into lead. Because the rate at which this decay takes place is constant, the age of the uranium itself, and therefore the rock containing it, can be calculated. Besides the uranium-lead techniques, the decay rates of the carbon isotope known as carbon-14, of lead-thorium, of potassium-argon, of rubidium-strontium, and of helium are also used. Dating by potassium-argon has been particularly useful in deciphering the story of Sierran granite, and carbon-14 has helped to clarify the last few thousand years of the Great Ice Age. Like uranium, carbon-14 has a steady radioactive decay rate, but a considerably faster one. This carbon isotope is obtained from the atmosphere by all organisms during their lifetimes. When a living organism dies and is buried, carbon-14 no longer enters its system, and whatever carbon-14 was in its body commences to decay to nitrogen-14. Wood is a particularly good subject for carbon-14 analysis, for even if it is burned, it can still be analyzed. Carbon-14 has been used in conjunction with another dating method—simple counting—to give a cross-calibration of the accuracy of the carbon-14 method. What is counted in this unusual check are the rings of the rare and ancient bristlecone pine. Since some of these trees have been producing annual growth rings for more than 4,000 years—they are among the world’s oldest living things — by counting the rings backward, it is possible to know which ring was produced in what year. Each ring is then carefully scraped off separately and burned. The ashes are analyzed for carbon-14, and the results associated with that particular calendar year. Another method of arriving at dates by counting is to enu-

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GEOLOGY: OF TIME AND ROCKS

merate “varves”—the dark and light layers deposited annually on the bottom of many lakes. Each year a black layer and a tan layer mark winter and summer, respectively, and by counting each pair, a researcher can tick off the passing years. Two other ways of measuring time involve calculating the damage radiation does to mineral crystals, and assessing the length of time certain chemical reactions take, such as the breakdown of amino acids. None of these methods is foolproof. The last two and the methods using radioactivity depend upon careful sampling and laboratory work, as well as upon fundamental assumptions that may not be wholly correct. In this book the story of the Sierra is told in years, but we must recognize that the dates given are subject to change as new information is discovered (fig. 2).

The Geologic Time Scale In past centuries geologists had no way of counting the years, so they used what tools they had—fossils—and based their ideas of the passage of time on the life and death of animals and plants. With fossils as the key, scientists developed the geologic time scale (fig. 3). Parts of it date back to the seventeenth century, when the intellectual revolution began to stir people’s minds to speculate scientifically about the Earth. Its originators were still tied to the Renaissance, and as they developed this time scale, still one of the geologist’s most important working tools, they used Greek and Latin roots in their terminology. Later other words from other languages were added. The time scale itself is built on the evolution of life—the idea that animals and plants developed from simple forms into more complex ones. This story fits together widely scattered fragments gathered throughout the world. Yet the fit depends upon just a few geologic principles that may seem almost self-evident to us now but were startling and revolutionary when first suggested. One principle is based upon the observation that many rocks are stacked in layers, heaped above one another like layers of a cake. Thus it seems reasonable that the lowest layer was laid down first, with the others piled in succession on top of it. If this is true, one can reason a step further: if certain rocks now stand on end,

GEOLOGY: OF TIME AND ROCKS

65

24 million

38 million

56 million

65 million

251 million

542 million

4,600 million

Years ago

ANCIENT SIERRAN SEAS Seas cover Sierra Nevada and much of the West. They are filled with layers of mud, sand, and gravel eroded from very old mountains to east. Undersea volcanoes contribute volcanic debris. Ancient Sierran rocks are derived from these sediments. Earth movements—possibly earthquakes—shake sea bottom.

THE EARTH’S BIRTHDAY

GRANITE FORMS Hot liquid rock (magma) cools and crystallizes in pulses to form Sierran granite core. Some magma rises to surface to supply volcanoes.

VEINS OF GOLD Hot liquids and gases carry gold and other metals upward into cracks within the ancient rocks and cooled granite.

Erosion

EROSIVE TIMES Ancestral Sierra Nevada uplifted. Erosion strips cover from granitic rock, exposing gold veins. Sierra begins to tilt westward and is eroded to a broad upland.

Miocene

TERTIARY PERIOD

PRECAMBRIAN

PERIOD PALEOZOIC ERA

PERIOD MESOZOIC ERA

4,030 million years

325 million years

180 million years

Figure 2. The long past of the Sierra Nevada, telescoped in sections.

66

Oligocene Epoch

Eocene Epoch

Paleocene Epoch

10 M CRETACEOUS

TRIASSIC

PERMIAN

MISSISSIPPIAN

50 M PENNSYLVANIAN

SILURIAN

DEVONIAN

CAMBRIAN

Geologic Time Scale

ORDOVICIAN

150 M

JURASSIC

Scales in years 2,000 M

GEOLOGY: OF TIME AND ROCKS

63 million years

150 134 Last advance of small glaciers Lone Pine earthquake

1,000

600–500

THE FUTURE

Glaciers disappear from main Sierran canyons

Mono Craters start forming

Last major glaciation begins

Eruptions begin to build Mammoth Mountain

Big Pine volcanic field eruptions begin

Long Valley volcano erupts 150 cubic miles of red hot ash, forming caldera

Violent eruptions bury the northern Sierra under lava flows, tuff, and volcanic mudflows, filling river channels, damming streams, covering low passes.

Small glaciers begin to form in the high peaks

Volcanoes continue to erupt to present day.

DAYS OF FIRE

Panum Crater and most recent of Inyo Craters form

2,500

10,000

35,000

60,000

300,000 220,000

760,000

2 million

5 million

Years ago

DAYS OF ICE Ice and snow cover most of high country, forming glaciers that extend down Sierran canyons. Glaciers wax and wane several times during Great Ice Age. Some glaciers partly covered or dammed by hot lava flows.

continues to present day. Sediments are accumulating to west in Central Valley; to east in desert valleys.

Uplift, tilting, and earthquakes still going on.

THE MOUNTAINS TREMBLE Sierra Nevada tilts westward. Earth movement along faults lifts mountains, causes earthquakes. Range is pushed upward to present height.

Epoch

Pliocene Epoch

1 Million

400,000

40,000

PLEISTOCENE EPOCH

Scales in years 10,000 1,000

HOLOCENE EPOCH

QUATERNARY PERIOD 2 million years

CENOZOIC ERA 65 million years

GEOLOGY: OF TIME AND ROCKS

67

MYA Era

Epoch

Duration (MY)

Holocene

0.01 (10,000 years)

Pleistocene

1.8

Pliocene

3.5

Miocene

17.7

Oligocene

10.9

Eocene

21.9

Paleocene

9.7

Period

Quaternary

0.01

23.0 33.9

Late Tertiary

5.3

Cenozoic

1.8

Early 55.8

145.5 199.6

Mesozoic

65.5 Cretaceous

80.0

Jurassic

54.1

Triassic

51.4

Permian

48.0

Pennsylvanian

18.1

Mississippian

41.1

Devonian

56.8

Silurian

27.7

Ordovician

44.6

Cambrian

53.7

251.0 299.0

359.2 416.0

Paleozoic

318.1

443.7 488.3

4600

Precambrian

542.0 4000 Origin of Earth

Figure 3. The geologic time scale. MY = million years; MYA = million years ago.

or are twisted, bent, broken, or gnarled, but otherwise resemble the rocks of the horizontal layers, then they, too, were probably horizontal when first laid down. The forces of Earth itself have moved, altered, and rearranged them (see fig. 3). This was an astonishingly long intellectual leap, reasonable though it may seem

68

GEOLOGY: OF TIME AND ROCKS

now. Earlier ideas either attributed the twisted rocks to the forces of evil or considered them to have always been that way. Once the idea of change was accepted, it was possible to understand that animals and plants change also. It was possible to show a definite progression, or evolution, of the form of organisms. If we couple this idea—that animals and plants change through time—with the idea that the layers of rock in which the fossilized remains of plants and animals are found were deposited horizontally, we can derive another important geologic principle: if two rock layers contain groups of organisms that are similar, the layers themselves were originally formed about the same time, regardless of their present configuration or geographical location. This is the principle of correlation. Sometimes the results of fossil correlation can be checked by determining the actual age in years of rock layers. By piecing together clues from rocks in various areas, we develop our idea of the past. Most rocks have contemporaries, both nearby and in distant parts. They are not necessarily the same kind of rocks; after all, rivers run, volcanoes erupt, and tides move the sea all at the same time, and each leaves a different mark—a different piece of the story. By matching fossils and using inductive reasoning, it is possible to match — to correlate —rocks of the same age over wide distances. In this way, a picture of the Earth through time gradually emerges, allowing us to see it as it was at various times in the past. For example, groups of land animals alive in eastern South America and western Africa 200 million years ago comprised the same animal species. This, together with other evidence, suggests that those continents were once connected and have since pulled apart.

Classes of Rocks That the components of some rocks were collected in water has been recognized throughout much of human history, but only in the course of systematizing geology have these and other rocks been carefully studied and classified. Today, rocks are generally sorted by geologists into three classes based on their origin: sedimentary, igneous, and metamorphic. The sedimentary rocks include most of the layered rocks. It is

GEOLOGY: OF TIME AND ROCKS

69

easy to see how the name is derived: if you shake a glass of muddy water, the mud— sediment— gradually falls to the bottom to form a layer, just as layers of sedimentary rocks were formed at the bottoms of lakes, rivers, and the sea. Some, but not many, of these rocks were not water laid— ancient sand dunes now turned to stone, for example. The igneous rocks, named from the same root as the word “ignite,” were once molten: fluid lava pours out on top of the ground to cool, and granite and its relatives, also molten, cool in the deep recesses of Earth without bursting onto the surface. The great mass of the Earth itself is an igneous rock. The metamorphic rocks are those that through the Earth’s unremitting restlessness have been changed from their original form into something else—something that may be quite different. Limestone may be altered to marble, peat to coal, or shale to slate. Some of the changes are obvious, but others require careful reasoning and the help of many other branches of science to decipher. Most metamorphic rocks have been formed by the intense heat, high pressure, and chemical changes involved in mountain building. Geologists divide each of the three classes of rocks into many smaller categories, depending upon their composition and origin (fig. 4). For example, sedimentary rocks are divided into those that were accumulated in water or on land solely from fragments of other rocks, those that were made from the remains of dead animals and plants or were in some other way derived from them, and those that were chemically precipitated from seawater or other natural chemical solutions on the Earth’s surface. Coral, peat, and some beds of limestone were once living matter, now turned to rock. Beds of rock salt, chert, potash, and some beds of limestone, in contrast, crystallized out of Earth’s solutions without life processes intervening. Thus, we could refer to “organic” sedimentary rocks, which were derived from once-living things, and “inorganic” sedimentary rocks, which were not. Sedimentary rocks are also given names according to the size and arrangement of the pieces in them. These are divisions most people know, even though they may not be aware of the mathematical lines of division that engineers and geologists have devised: mudstone is mud, now become stone; sandstone is just what the name implies; and conglomerate is rock consolidated from gravel mixed with sand and mud.

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lithifies (solidifies) into sedimentary rocks

erodes to form sediments

is metamorphosed

metamorphoses nearby rock cools into igneous rocks HOT MOLTEN ROCK

is buried and remelted into

Figure 4. The rock cycle. The ultimate source of Earth’s rocks, save for a rare meteorite, lies deep in the Earth in its mantle (a zone below the Earth’s crust and above the core). The arrows on the left depict the movement of fluid rock (magma) in response to convection currents in the Earth. Some of the magma rises along vents in the Earth’s crust, many of them in the deep sea, to solidify as igneous rocks. Meanwhile, weathering and erosion wear rocks into particles that are collected in the seas and on land to form sedimentary rocks. Slabs of lithosphere (the crust and part of the mantle), which provided the source for the magma in the deep sea, plunge downward toward the interior of the Earth along subduction zones (deep trenches in the Earth). As they plunge, some of the asthenosphere (a layer below the lithosphere) is melted, providing another source of magma. The melted rock rises through rocks of the continents (the continental lithosphere), cooling into igneous rock and causing mountains to rise. These igneous rocks, which have melted some continental rocks, have a different chemistry from igneous rocks formed from melts in the deep sea. Weathering and erosion attack the new mountains, wearing them down into particles that form other sedimentary rocks. Where the magma rises through the continental rocks, the continental lithosphere is altered to metamorphic rocks.

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71

The igneous rock group (fig. 5) also has some familiar names in it: a coarse-grained, salt-and-pepper crystalline rock most people know as “granite”; the common term “lava”; “obsidian” (volcanic glass) and “pumice,” which are other types of readily recognized igneous rocks. Through the years, geologists specializing in the study of igneous rocks have set up elaborate groupings with complicated rules for naming them. To apply these more sophisticated names, laboratory methods not available to most people are required. Metamorphic rocks are still more difficult to name. Even geologists, if they are not specialists in metamorphic terminology or do not have a laboratory at hand, content themselves with calling the rock by its name before it was metamorphosed (i.e., limestone) or giving it a simple field name (marble). To become adept at distinguishing the various types of rocks, even on a fairly simple basis, it is necessary to be able to recognize some minerals. Minerals are natural chemical elements or com-

Plutonic (Grains identifiable by eye or with a hand lens)

Volcanic (Grains too small to be identified by eye or with a hand lens)

Light

Rhyolite

Diorite

Andesite

Gabbro

Basalt

Peridotite

Figure 5. Common igneous rocks.

72

Color

Porphyry

Granite

More plagroclase feldspar

More dark minerals (pyroxene, amphibole, olivine)

More quartz and orthoclase feldspar

Mineral components

GEOLOGY: OF TIME AND ROCKS

Dark

FPO

Plate 4. Rhyolite, a light-colored lava.

pounds, and most are crystalline solids. They are the ingredients of rocks. Some rocks are made up of one mineral only; others have a dozen or more. California was the first state to have an official state mineral: gold. It also has an official state rock: serpentine, which can be made up of several related minerals. Although knowledge of many minerals is helpful, recognizing just a few will serve to identify the rocks in fig. 5 and in the rock identification key. Learn to know these few on sight: quartz,

GEOLOGY: OF TIME AND ROCKS

73

feldspar, mica, amphibole, and pyroxene. None is truly an individual mineral (or “mineral species”), and each belongs to a group, or family, of minerals. If you can recognize the group, you can use the tables in this book. Rocks may contain a wide variety of minerals, but more than three-quarters of the ingredients in all three classes of rocks are members of but two mineral families: quartz and feldspar. If you can recognize these, you have already gone a long way toward learning to distinguish rocks from one another. Some 1,500 minerals can be identified by a knowledgeable person using only a small hand lens. This represents roughly half of the total number of mineral species. For the avid mineral collector, recognizing 1,500 species is exciting, but not necessary to the general understanding of the story of the rocks; a few minerals can act as guideposts. The more you know, of course, the more interesting the story becomes, as subplots and counterplots are revealed.

Naming Rocks It is not easy to decide what any rock should be called. Many reasons exist for this naming difficulty, but basically the problem is simply that rocks do not yet have names that are entirely agreed upon, as do plants and animals. To help you get at least some idea of what to call a rock, the rock identification key has been constructed in a manner similar to those used by biologists. Bear in mind that this key is for the Sierra Nevada only; if you try to use it on rocks from other places, it may give you a wrong answer. Even after you have arrived at a simple field name for a rock (“schist,” for example), it does not prepare you to read the geological literature with any facility. In the two centuries that California rocks have been studied, the same type of rock — indeed, the same outcrop — has been given a host of different names by different investigators. This changing of names represents an increased knowledge of the rock itself, as well as an increase in knowledge of the science of rocks. But it does make reading about them extraordinarily difficult. To help you understand what you read, the glossary at the end of the book includes rock

74

GEOLOGY: OF TIME AND ROCKS

names used in the Sierra Nevada and refers you to the simplified field names used in this book. You will soon discover that “calchornfels” is the same rock you may already know as “limestone.” In addition, the tables tell you where to see good examples of the various types of rocks. If you become familiar with the rocks in the places suggested, you will have a good start toward recognizing the rocks of the Sierra Nevada.

GEOLOGY: OF TIME AND ROCKS

75

CHAPTER 2 THE RANGE TODAY

Overleaf: Three of the Palisade group of peaks. North, Middle, and South Palisade are all “14,000-footers,” and all stand above Dusy Basin and Palisade Glacier, the range’s largest glacier. Like Whitney, the Palisades are all constructed of granitic rock. Although these peaks are within the highest Sierra, the granitic rock of which they are made solidified deep underground, and was lifted to its present high elevation millions of years later, when it was subjected to extensive erosion. The peaks are sharp because they were torn by glaciers in the geologically recent past.

THE SIERRA NEVADA —the

long backbone of California —is steeper on the eastern side than on the western, giving a bird’seye view of the range a rakish aspect, an aspect that is undergoing constant change. Clouds passing over the range are intercepted by the range itself, causing rain and snow to fall on the western side, leaving the eastern side dry. Turbulent rivers, most flowing toward the sea, have cut deep canyons on the western side (fig. 6), where the slopes are so thickly forested that struggling through them on foot is daunting. The tilted range is so steep and dry on the eastern side that climbing the bare rock is a mountaineering challenge. But when word got to Washington, the nation’s capital, in 1848 that gold had been discovered in California, no one worried about the difficult terrain. The word “gold!” seemed to set the whole world on fire. The prospect of digging up one’s fortune in a new land sent many a man and woman off to the gold fields: from the North American south and east, from the Latin countries of the Americas, from Europe, from Africa, even from China and the Far East came the young and not so young. Some of them were experienced miners, especially those from Mexico and South America; some had extraordinary patience, especially the Chinese; and all learned to be carefully observant. For these were the qualities necessary to a good miner: experience, pa-

Figure 6. Diagram of the tilted Earth block that is the Sierra Nevada. The height and slant of the range are exaggerated. In front of the mountains is the Great Central Valley of California, comprising the Sacramento and San Joaquin Valleys, filled with sediment derived from the mountains. Owens Valley is marked on the eastern side of the mountain block. The fault system that bounds the east face is marked by arrows that indicate the direction of movement.

T H E R A N G E T O D AY

79

tience, and careful observation, mixed with a generous helping of good luck. At first it seemed that Lady Luck alone panned with the miners. The first few months only rivers tumbling from the mountains were worked. Lucky prospectors stumbled upon huge nuggets and mined gravel containing $500 worth of gold in a single pan, while unlucky prospectors, working not far away, could recover only a few dollars’, or a few cents’, worth. Gradually, the more canny and experienced among them began to discover a pattern to the accumulation of gold. The gold was in streambeds, and therefore a knowledge of the habits of streams might be useful to the prospector. Later, they were to learn that a knowledge of the habits of today’s streams would teach them about the habits of fossil streams and lead them to the discovery of even greater accumulations of gold.

Sierran Rivers It is a political and geographic fact, dependent upon a geologic fact, that almost all California rivers rise in California and end in the sea off the California coast or sink into the ground (fig. 7). A few exceptions exist: the Colorado River rises in the Rocky Mountains and flows into the Gulf of California; the Truckee, Carson, and Walker Rivers rise in the Sierra Nevada and flow into Nevada. The Owens River, whose bed lies at the eastern foot of the Sierra, is — or, rather, was — another exception, as its many tributaries rose in the High Sierra and flowed eastward, then southward into Owens Lake. Today, the water that once flowed in the Owens River is sent through aqueducts to Los Angeles. From the Sierra, the Feather, Yuba, Bear, and American Rivers all flow into the Sacramento. The Cosumnes, Mokelumne, Calaveras, Stanislaus, Tuolumne, Merced, Fresno, San Joaquin, Kings, and Kaweah Rivers all flow into the drainage area of the San Joaquin, although some of them lose their identity long before making a recognizable confluence. These two major rivers, the Sacramento and the San Joaquin, join in Suisun Bay to flow into San Pablo Bay, San Francisco Bay, and the sea. Today, much of the water is diverted or impounded before it reaches the sea.

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T H E R A N G E T O D AY

Eagle Lake N

r a Riv e Yub er

e rica nR iv

m

is u o la u s lu n

Mono Lake Ne Ca vad Owens lifo a rn ia

e iver mn R

R.

T

er Ri

n qui oa nJ

Bishop

ver

Sa

iv ced R Mer

R

i ve r

J Sa n

ui n aq

Kin

amento R. acr

St a

Calaveras River Flows to SF Bay and Pacific

Walker Lake

Co

S

Lake Tahoe iver R A n es River sum ne m u el Rive r M ok

Pyramid Lake Carson Truckee River Sink Reno River on Carson C ar s Lake Carson City Walker River

o

Feathe r

Riv er

Honey Lake

River gs

20

40 miles

r

n

0

R ive r

Owens Lake (dry)

0

40 kilometers

Ke

Ridgecrest

Figure 7. Central California showing the major rivers that drain the Sierra Nevada. Most of them rise in the Sierra and flow into the San Joaquin or Sacramento and thence to the sea; a few flow eastward into Nevada.

Think Snow In spite of California’s current concern with a sufficiency of water, a great deal falls on the Sierra Nevada, mostly in the form of snow (pl. 5). Much of the rain and snow falls on the western

T H E R A N G E T O D AY

81

Plate 5. Glacial moraines under snow.

side, because the mountain bulk, standing over 14,000 ft (4,267 m) in some places, interrupts the clouds as they are blown crosscountry by westerly winds. Most of the moisture in these clouds is removed as moist air is lifted up the western flank, so that little falls on the eastern side, making that face and the land beyond it a desert. There, the yearly rainfall averages from 5 to 15 in. (12.7 to 38.1 cm), while on the western side many places receive 50 in. (127 cm) of moisture a year. At Tamarack, in Alpine County, 450 in. (1,143 cm) of snow — more than 37 ft (11 m)— is the average, and in the winter of 1906–1907, 884 in. (2,245 cm) fell—almost 74 ft (23 m)! Tamarack holds the record for the greatest snowfall in one calendar month in all of North America: 390 in., which is 32.5 ft (9.9 m), in January 1911; it also once held the U.S. record for having the greatest depth of snow on the ground at any one time (not counting snowdrifts): 451 in. (11.5 m), nearly 37.6 ft! These records are not official, because they were measured before official government records were kept. Tamarack is only 8,000 ft (2,438 m) in elevation, but during one 22-year period, it received an average of 30 ft (9.1 m) of snow, about 40 times the snowfall of Antarctica.

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Think Big The eastern slope of the Sierra Nevada is precipitous, with lofty mountain peaks rising quickly and starkly. It is a large range, 50 to 80 mi (80 to 130 km) wide, containing nearly as much area as the French, Swiss, and Italian Alps combined, and is easily the largest single mountain range in the contiguous United States. Other large mountain areas, such as the Rockies and Appalachians, are mountain systems, made up of individual ranges, none as large as the Sierra Nevada. The Sierra’s general trend is northwestward, and measured in that direction it is nearly 400 mi (640 km) long. Its southern boundary lies at the end of the Tehachapi Mountains, where the Garlock fault meets the San Andreas fault. Its southern peaks are the highest. From Mount Whitney (14,496 ft [4,416.9 m]), crown of the range and highest mountain in the contiguous United States, the Sierra slopes downward to the north, where the crest is only about 8,000 ft (2,440 m) in elevation. Its northern boundary is covered by lava flows of the Cascade Range. Geologically, the Sierra Nevada can be thought of as a single mountain range, but it is part of the whole western mountain complex, with close relatives in the Klamath Mountains to the northwest, in the desert to the south, and in the White Mountains to the east. If the eastern slope is treacherously precipitous, the western side is deceptively gentle. It has an average tilt of only 2 degrees, compared with the 25 degrees in parts of the eastern side. But that long, slow, well-watered western side has been carved by Sierran rivers into deep canyons and steep ridges, generally covered by a thick growth of trees and brush that make travel up and down the slopes tedious and exceedingly difficult.

Sierra Nevada Canyons The major canyons of the Sierra, with the exception of the Kern and upper San Joaquin, are roughly parallel to one another and were cut at right angles to the range. You can follow one of the text continues on page 86

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MOUNT WHITNEY: THE U.S. ROOF (ALMOST)

ount Whitney, highest mountain in the United States south of Alaska, stands in the southern Sierra Nevada (pl. 6). Most lists and maps give its elevation as 14,496 ft (4,418.4 m) or 14,491 ft (4,416.9 m) above sea level, but recent measurements by the National Geodetic Survey gave 14,497 ft (4,418.7 m).The differences arise from what sea level is. Mean sea level in the Pacific is higher than in the Atlantic; in addition, mean sea level changes from day to day, and worldwide the mean level is rising about .1 in. (.25 cm) per year.The United States and Canada have agreed to use as sea level a point at the mouth of the St. Lawrence Seaway. At the top of Mount Whitney, several boulders of differing heights carry bench marks.The National Geodetic Survey thinks it has selected the highest one.The U.S. Geological Survey agrees, but no one in the government can justify the expense of changing numbers on millions of maps—accuracy notwithstanding. Mount Whitney is composed of granitic rocks of the Whitney Intrusive Suite (see chapter 6).Although the very top of Mount Whitney stood above the ice fields of the great glacial epoch, the hiking trail exhibits many glacial features such as glacial polish.A steep cirque, just below the mountain crest, marks the residence of a former glacier and has made the east face of the mountain a difficult climb. From the top of Mount Whitney’s barren crest, in clear weather you can see eight peaks that exceed 14,000 ft (4,267 m) in elevation—five of them in one group to the north.Among the 14,000-footers are Mount Tyndall (14,018 ft [4,273 m]), which geologist Clarence King climbed hoping it was Mount Whitney, and Mount Muir (14,015 ft [4,272 m]), named for Josiah Whitney’s rival. Most of Mount Whitney is, ironically— considering the difficulties between Josiah Whitney and John Muir (see chapter 12)—in the 100-mile-long John Muir Wilderness. In 1957, only 2,658 people climbed Whitney during the whole year, which then was a record.Two years later, the number of climbers nearly doubled to 5,490. More recently, more than 20,000 people per year climbed the peak. Often you can see 50 or 60 people on the windswept top at one time. Most come by way of the Whitney Trail, which requires no mountaineering experience. Climbing Mount Whitney has become so popular today that driving to the trailhead is restricted. Climbers must first hike the 11 miles from Whitney Portal near Lone Pine to the trailhead.A lottery is held each year to decide who will be given permits to

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climb the peak. Hikers must pause at Whitney Portal and take their turns going up the mountain.Also, probably, they must take their turns at the outhouse, the highest-elevation toilet in the country, and the most expensive to maintain, as the “honey pot” has to be emptied by helicopter. But what a mess without it! Whitney has been designated a “Special Zone,” requiring not only a wilderness permit, but also a special permit, even for day hikers coming from other trails. Despite these complications, the Whitney Trail in summer resembles a hiker’s freeway. Some have called it “Disneyland with a nosebleed.”

Plate 6. Sign atop Mount Whitney, marking it as the highest spot in the 48 contiguous United States. When this plaque was installed in 1930, Whitney was the highest mountain in the states, but since then Alaska has become a state and boasts the highest point in North America: Mount Denali (McKinley) (20,320 ft [6,194 m]). Denali is not the tallest peak in the United States, however; that honor belongs to Mauna Loa, Hawaii, which projects 13,680 ft (4,170 m) above sea level, making it a formidable mountain, but its base is on the floor of the Pacific Ocean thousands of feet below. Although measurements of Whitney’s elevation have changed, as for many mountain peaks (owing partly to more accurate instruments and partly to uplift and erosion of the peaks themselves), Whitney has remained the highest point in the contiguous United States.

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canyons westward; but if your goal is north or south, travel is constantly up and down, as anyone who has followed the Mother Lode route (State Hwy. 49) can testify. The up-and-down-ness is extreme because all of the rivers are entrenched in deep canyons. One, the Kings, has a canyon 8,000 ft (2,438 m) deep, measuring from Spanish Mountain—on the northern side of the canyon— to the river, which is considerably deeper than the Grand Canyon. To the hiker, the numerous deep canyons and sharp ridges present chaos. On foot, you cannot see that the entire mountain block is tipped slightly southwestward, and that master streams generally flow in that direction (fig. 7). In fact, they do not always flow in the principal downslope direction. In the Mother Lode and the northern mines, where the streams leave the granite of the high country to enter the metamorphic terrain of the foothills, they deviate from their courses, forced into a new direction by the resistant ridges of old rock. Water, like all else in the universe, conserves its own energy. It bends its course when it strikes obstacles, seeking the easiest, though not necessarily the shortest, route to the sea. As the streams pass through the metamorphic rocks, they pick up particles of minerals, including gold, that have broken loose from rocks in the fierce Sierran winter. Such was the gold that the early Argonauts sought: particles of gold carried along by the water, resting here and there in a stream channel on their way westward. The miner who could predict where the gold was likely to accumulate by studying the stream was more apt to be successful than one who depended wholly upon luck.

A Stream’s Path As anyone who has used a garden hose knows, the faster and heavier the stream of water, the greater the amount of soil and leaves it will push. Other things being equal—which they rarely are—this can be expressed as the “load” of a stream: the amount of rock, sand, and soil that it can move. Obviously, streams flow faster down steep slopes than they do down gentle ones. In general, then, you would expect streams in steep, high mountains to be stronger and straighter than those in more level country, as they have more strength to push aside obstacles in their paths than do the sluggish streams of the lower slopes. Meanders —

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Plate 7. The meandering Owens River. Once a rushing stream furnishing water for farms on the eastern slope of the Sierra Nevada, the Owens has been reduced to a trickle by the taking of much of its water by Los Angeles. The stream heads west in the High Sierra.

those repeated bends in stream channels—form where streams flow over nearly level ground (pl. 7). The Mississippi in its lower reaches meanders widely; there are miniature Mississippi patterns in the Sierra in high mountain flats, such as Leavitt Meadows, east of Sonora Pass. Almost all rivers tend to form constantly winding paths—to begin to meander. Even if water is started down a clean sheet of glass, the path the water takes begins to curve, just as raindrops may wander down a vertical window. The less steep the slope the water flows down, the greater the number of bends. There are, in fact, meanders in the freshwater currents that traverse the world’s oceans. The reason is not immediately apparent. True, the stream deflects its course as it strikes objects, but to the careful observer, it seems that the stream overreacts, that its bends are greater than one would expect from the size of the obstacle. Indeed, if you studied the patterns of streams on topographic maps, you might conclude that the smaller the obstacle, the greater the deflection! A river meanders because it is seeking the easiest route to follow. A stream that meanders uses less energy than one that does not. Therefore, where streams have little speed and force, the easiest course for them to follow is a meandering one; for them, the longest way round is the easiest way home.

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Carr ying the Load It is this tendency for streams to bend that provided the resting points for the particles of gold that prospectors sought and still seek. The stream carries a great mass of sand and gravel—and the gold with it—in its bed. Where the stream bends, or where there are irregularities in the bottom of the bed, some of the load of rock particles is dropped, at least until water from a new storm gives renewed vigor to the stream. In general, the larger and heavier the particle, the harder it is for a stream to move it. Enormous boulders in the stream courses of the high mountains are in the process of being moved. Large boulders are bounced along the bottom, sand and gravel are churned in the bed, and fine particles are carried in suspension or are dissolved in the water. The muddiness of rivers that meander over wide flat areas is witness to the load they carry. The particles in suspension or solution cannot always be seen, but they may tint the water a light chocolate or milky color. The clarity of mountain streams, in contrast, testifies to their load: in the colorless water, large pieces—sand, gravel, boulders—lie on the bottom, with only a few rock particles small enough or flat enough to be suspended. Eventually a river, if it has enough water, enters the sea. Where it enters, much of the load it has been carrying—small particles, because by this time the river is too sluggish to carry large ones— is dropped to form a delta. A delta is wedge shaped, if viewed from above, like the Greek letter from which it takes its name.

The California Delta California’s best-known delta is not at the seashore. It is inland, where the Sacramento and San Joaquin Rivers meet. This great region, crisscrossed by a thousand miles of river-channel waterways that meander and join in an intricate braided pattern, is the point at which Sierran water slows in its race downhill, before it mingles with ocean water. Although this region where the two rivers merge is called the Delta (fig. 8) it is not a simple triangle of the form and shape of

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Figure 8. Postcard aerial view of “the Delta,” created by the meandering Sacramento and San Joaquin Rivers flowing out of the Sierra Nevada toward San Francisco Bay and the sea.

the Nile delta, to which the word “delta” was first applied. It is, instead, two deltas: one a distributary for the San Joaquin River, and one for the Sacramento. Rivers that enter the sea have deltas that fan out broadly. In contrast, the delta system of the Sacramento and San Joaquin Rivers is truncated. After the rivers’ loads are dropped at the Delta, the combined rivers then race through the Carquinez Strait, bend into San Francisco Bay, and move out the Golden Gate to the sea. The story of this delta has been complicated by faulting, by the drowning of the area with seawater when ice melted at the end of the Great Ice Age, and by choking with debris from hydraulic gold mines in the Sierra Nevada.

A River’s Life The life story of rivers from the first drop of rain to their plunge into the sea or their disappearance into the desert sand is of great

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interest to all of us today. We value the brooks for their beauty; the rivers for their wildness. We thirst for their waters for ourselves, our lands, and our machines and need the gravel they carry and the life they support. For all these many reasons, the Delta, from the river confluence to the Golden Gate, has been studied to understand how rivers and bays the world over behave. Engineers and scientists have made a scale model of the whole region to use as an exact tool. It is housed in Sausalito, Marin County, and is open to the public. You can watch the tides in speeded-up action, see the water rise and fall, and measure the effect changes in the land or water have on the entire system. Those who made the model and those who use it (it can be rented for testing purposes) are not interested in gold (although their equipment could be used to study placer gold deposits), but in how streams behave. They need to know how fast a reservoir will fill with sediment and how to prevent silt from clogging an irrigation channel. Scientists once assumed that only mechanical laws applied to sedimentation; that sandstone, shale, conglomerate — all were formed according to the rules of physics alone. For example, there is a mathematical expression for the rate at which particles fall through water, taking into account their size and surface area. A different law gives the relationship of the shape of the particles to the rate at which they fall (in general, the flatter the particle, the slower it falls). Together, then, they should tell us how fast mud, silt, and sand will build up in watercourses, a matter of interest to engineers who manage our water supplies and to geologists who need to know how fast natural processes take place. But nature has surprises. An eight-year study of the DeltaMendota Canal, a part of the California Water Project, showed that physical laws alone do not account for all the accumulation of sediment. The canal is a concrete-lined ditch for 95 mi (153 km) of its 113 mi (183 km) length, carrying Sierran water from the Delta area southward. Its water is unusually turbid, owing partly to organic material picked up from extensive peat beds the canal passes through, and partly to abundant plankton living in the water. The organic material is very light in weight, easily carried long distances. Its presence prevents the rapid settlement of the fine mineral particles that engineers had predicted. On the other hand, when the canal was emptied of its water,

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stretches of unexpected sedimentary layers on the concrete liner were laid bare. Although the layers were horizontally stratified, as one would expect from settled particles, they showed a color change from light gray at the top to black at the bottom. In the black sediments were many empty shells of the Asiatic clam Corbicula fluminea, which had been accidentally introduced into this country. On the gray surface of the upper sedimentary layer were many live clams. In these clam-rich areas, the amount of sediment deposited was unusually large. Engineers, geologists, and biologists jointly studying the sediments and the sedimentary process came to the conclusion that the sediments came from the turbid canal water that had been pumped through the body of the clams. The layers were gradually turning to rock: shale organically produced through excretion by clams! How many other of our geologic processes, heretofore considered to be principally or wholly mechanical, have an unsuspected biological aspect? Not all rocks and minerals of the same size are the same weight. Some are as light as pumice, which floats on water, and some are nearly as heavy as gold. The heavy particles, particularly gold, are hard for the stream to move. They are so much heavier than the rest of the sand and gravel that the stream is constantly pushing the other material over the reluctant gold, thereby settling the gold and other heavy minerals deeper and deeper in the stream bed. Even novice prospectors soon found that these heavy gold particles, in the process of being winnowed by the stream to the bottom of its bed, dropped on the inside of curves more than on the outside of curves. They found “pay streaks,” which are concentrations of gold and other heavy minerals that had been sorted by the stream into zones within the sand body. They found that where the river channel bottom was smooth, such as in areas of polished granite, gold was less likely to accumulate than where there were irregularities to trap the gold. Here, behind the bumps and in the holes, they found nests of placer gold (pl. 8). In the lower reaches of Sierran streams, where the rivers leave the granite of the high country to enter an area made of metamorphic rock, the channel bottoms became a natural gold-concentrating machine. The metamorphic rocks have been upended in many places, although their original position must surely have been as horizontal as the sand in lakes of today. As the particles of

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gold were pushed downstream along the bottom of the channel, they dropped behind projections of the upended rock, sometimes burrowing into the weathering bedrock itself. Enterprising miners, knowing the habits of rivers, turned aside large waterways to mine the river bed. For one river-moving enterprise, which diverted the Feather River for more than a mile,

Plate 8. Gold in quartz.

miners built a concrete trough to contain the river while they stole its gold. It is no longer necessary to move rivers for the sake of gold; skin divers of today mine Sierran streams every summer with fin and mask, pry bar and suction tube. No one has yet grown rich, but it is a form of mining very close to the original Spanish meaning of the word “placer”: pleasure.

Wearing Down the Mountains The rivers get the sand, gravel, and silt they are carrying toward the sea by wearing down the mountains with water. Wind, too, erodes them and deposits particles in the rivers. Sometimes, you can watch the mountain being worn away: landslides, rockfalls, mudflows—all are tearing the mountains down, making smaller pieces that rivers and streams can move toward the sea. As the processes of erosion continue, whether at the speed of a rockfall or at nearly undetectable rates, the mountains are carved by wind, water, and ice into a mass of hills and valleys. The exact shape of the hills and valleys, the distribution and size of rivers

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that drain them, and in turn, the plants that clothe them are determined by a number of factors. The kind of rocks, the height of the mountains, the amount of rainfall, the number of rivers, the strength of the wind, the frequency of earthquakes, the severity of the climate, and the actions of animals and people all exert some influence on what mountains look like. Measurements of the San Joaquin River show that now, when dams have curtailed much of its flow and canals control it, the San Joaquin is carrying away the Sierra at the rate of 1 in. (2.5 cm) per thousand years. Compare this with the Eel River of northern California, which is removing the Coast Ranges at the rate of 40 to 80 in. (1 to 2 m) per thousand years! This is the fastest erosion rate in the nation and is 15 times as fast as the Mississippi is eroding its borderlands. Since erosion is constantly at work, are the mountains actually being worn away? The answer is, they are; however, they may not be getting lower, as mountain-building forces at work in the Sierra may be keeping pace with or exceeding the rate of erosion.

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CHAPTER 3 BEING FIRST

Overleaf: Hiker below Mount Lyell. The granitic rocks have been rounded by glaciers that passed through this valley during the Great Ice Age, which ended only 10,000 years ago. At that tiime, Mount Lyell was a source from which great glaciers descended into Tuolumne Canyon, Yosemite Valley, and other canyons in the Sierra Nevada. The rocks themselves are millions of years old, but their present shape was acquired much later. The glacier in the background, below the peak, is not a remnant of the Great Ice Age, but a relative youngster, dating from only the last millenium. (See also pl. 10.)

Clarence King dreamed of being the first to climb the highest mountain in the United States: Mount Whitney, in the Sierra Nevada (table 9). (This was before the United States owned Alaska, which has the highest peak in North America.) He helped give Whitney its name but never did succeed in being the first to stand on its top. King was an explorer who climbed peaks and mapped regions where no white person had gone before, but likely he was not the first to be there, nor was he the first man, woman, or child to cross the range or to probe its landscape. The mountains are crisscrossed by age-old Indian trails, many of them following tracks made by other animals. Several tribes of Native Americans called the Sierra home, and they and others came to its mountains also for practical reasons: to hunt game for meat and clothing; to harvest vegetables, seeds, and nuts; to harvest wood for lodges; to seek out useful mineral deposits. They knew the mountains intimately and had their own network of trails. Many threads of the network are now lost to us; others have become the roads and highways of today. How long the native groups had lived in and near the Sierra Nevada is not known, but certainly thousands of years. Scattered though the Sierra are the remains of many villages and sites of Indian occupation before 1849. Up and down the range are evidences of culinary activities in the form of grinding rocks, where women gathered to grind acorns (pl. 9). By rolling an elongate rock, to act as a pestle, over acorns laid on top of a rock outcrop, used as a mortar, they could grind the acorns into flour. Eventually a depression was worn in the rock outcrop, and slowly a hole. If, after years of use, the hole was ground into the rock 10 inches or so, it was too deep to work well, and a new one had to be started. Many such kitchen sites dot the Sierra, most of them in outcrops of granite, as it was coarse enough to provide a rasp to aid in crushing the acorns. The resultant meal was also a rasp on the teeth, as it often contained tiny broken rock fragments from the grinder. Stone grinding, though providing healthful flour, had its drawbacks. The mortars were used year after year. Those at higher elevations served as kitchen areas when the people fled to the mountains to escape the heat, as we do today. Because these kitchen implements could not be carried on the cooks’ backs, villages and residences, being more portable, were located near the bedrock text continues on page 100

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TABLE 9

The Sierra Nevada’s Highest Peaks and their “Firsts”

All but two of California's mountains exceeding 14,000 ft (4,270 m) in elevation are clustered in the southern Sierra Nevada. One exception is the volcano, Mount Shasta (14,162 ft [4,317 m]), north of the Sierra, the other is White Mountain Peak (14,246 ft [4,351 m]), in the White Mountains east of the Sierra. Colorado has more than fifty 14,000-ft peaks, but Mount Whitney, in California, is higher than any. Mount Rainier, in Washington, which like Shasta is a volcano, is only 84 ft (25.6 m) lower than Whitney. Alaska has a great many very high peaks, including the highest in North America, Mount Denali (20,320 ft [6,194 m]).Hawaii's Mauna Kea (13,796 ft [4,205 m]), is actually taller, because it rises from the seafloor rather than land. No other state has 14,000-ft peaks. Mount Clarence King, whose namesake yearned to climb the nation's highest peak but did not succeed until after it had been climbed by others, is only 12,905 ft (3,933 m) in elevation. MOUNT WHITNEY

14,491 ft (4,416.9 m), more properly, 14,497 ft (4,418.7 m) (See sidebar “Mount Whitney,” chapter 2)

Highest peak in contiguous 48 U.S. states. Named for California State Geologist Josiah Dwight Whitney. First climbed by John Lucas, Albert H. Johnson, and Charles D. Begole in 1873, three Lone Pine residents who called it Fisherman's Peak, not knowing it had already been named Mount Whitney, but not climbed. A horseback trail now goes to the top. Mount Whitney is composed of granodiorite, a granitic rock, part of the Whitney Intrusive Suite of rocks. Rocks in the central part of the suite contain giant crystals of potassium feldspar.

MOUNT WILLIAMSON

14,375 ft (4,380 m)

Named by Clarence King for Lieutenant Robert S. Williamson, leader of one of several parties exploring the western United States in 1853 for a practicable railroad route to the Pacific Ocean. Mount Williamson was first climbed in 1884 by W. L. Hunter and C. Mulholland.

NORTH PALISADE

14,242 ft (4,341 m)

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First climbed by James S. Hutchinson, James K. Moffet, and Joseph N. Le Conte in 1903. The three Palisades, North , Middle, and South, stand above Palisade glacier, the largest glacier remaining in the Sierra.

STARLIGHT PEAK

14,200 ft (4,328 m)

First climbed in 1930 by Norman Clyde, who made the first ascent of many Sierran high peaks.

MOUNT SILL

14,162 ft (4,314 m)

First climbed in 1903 by James S. Hutchinson, Joseph N. Le Conte, James K. Moffet, and Robert D. Pike.

POLEMONIUM PEAK

14,080 ft (4,267 m) Many sources give 14,200 ft (4,328 m)

First ascent not recorded. Peak is southeast of North Palisade. Named for Polemonium eximium (sky pilot), a plant with bright blue flowers that grows at higher elevations than any other Sierran plant.

MOUNT RUSSELL

14,086 ft (4,293 m)

Named for Israel C. Russell, geologist who studied the eastern slope of the Sierra and Mono Lake in 1882– 1883. First ascent by Norman Clyde, 1926.

SOUTH PALISADE

14,058 ft (4,285 m)

First ascent by Mr. and Mrs. Joseph N. Le Conte and C. Lindley, 1902.

MOUNT LANGLEY

14,042 ft (4,275 m)

Named for Samuel Pierpont Langley, later secretary of the Smithsonian Institution. Clarence King and Paul Pinson, a French mountaineer, climbed it in 1871, thinking they were climbing Mount Whitney. King noted that an Indian had preceded them.

MIDDLE PALISADE

14,040 ft (4,279 m)

First climbed by Francis P. Farquhar and A. F. Hall, 1921.

MOUNT TYNDALL

14,018 ft (4,273 m)

First climbed by Clarence King and Richard (Dick) Cotter in 1864 during their excursion to the highest Sierran peaks for the Whitney California Geological Survey. King called it Tyndall in honor of John Tyndall, Swiss glacial scientist. continued ➤

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TABLE 9 continued

MOUNT MUIR

14,015 ft (4,272 m)

Named for John Muir, conservationist founder of the Sierra Club. Mount Muir is very close to Mount Whitney, but who first climbed it is not recorded. Composed of granitic rock of the Whitney Intrusive Suite.

THUNDERBOLT PEAK

14,003 ft (4,267 m)

First climbed in 1931 by Lewis F. Clark, Norman Clyde, Glen Dawson, Jules M. Eichorn, Francis P. Farquhar, Bestor Robinson, and Robert M. L. Underhill. During the climb, a severe thunderstorm struck. Eichorn reported “a thunderbolt whizzed right by my ear.” From that, the peak was named.

grinding stones. Especially good sets of these bedrock mortars have been saved in Yosemite National Park, in Indian Grinding Rock State Historic Park near Volcano, and at Sugar Pine Point State Park, south of Homewood on Lake Tahoe. The grinding holes are just offshore from the Ehrman mansion. Acorns are not palatable until the bitter tannin is leached out of them, so the cooks boiled water in woven baskets waterproofed with pitch. They filled the basket with water, then dropped in hot stones to make the water boil. For this, they preferred finegrained metamorphic rock, as it did not come apart readily when heated. These people did not live by acorn bread alone. Men hunted big game—deer, elk, antelope, mountain sheep—with wooden bows and arrows tipped with obsidian (volcanic glass) from deposits near Mono Lake. Everyone hunted small game near the villages, especially squirrels and rabbits, which went into the cook pot after giving up their skins for blankets. Bulbs and seeds, nuts of piñon and other pines, manzanita berries, fish, lizards, birds, dried grasshoppers and caterpillars, as well as salt from dry desert lakes at the foot of the eastern Sierra, gave their diet variety and zest. On the eastern side of the range, near Mono Lake, the alkali flies (Ephydra hians) laid their eggs underwater in abundance. These unusual flies are able to crawl underwater, breathing air

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Plate 9. Holes ground into rock at Indian Grinding Rock State Historic Park, near Volcano. Through many years of grinding acorns using slabs of rock as pestles (manos), Indian women wore these holes into metamorphosed limestone bedrock. Many of the grinding rock areas in the Sierra Nevada are in granitic rock, which is very efficient, but the rock fragments that sometimes break off are hard on the teeth. Limestone, being softer, is not as effective, but easier on the teeth and digestion. The 1,185 holes in this rock indicate that the soft rock was worn down quickly. At a depth of about 10 in. the bottom could no longer be reached easily, forcing the woman grinding to shift to another spot. Besides holes, this rock features petroglyphs—decorative carvings—of spoked wheels, animal and human tracks, and wavy lines, among others. Some of the carvings may be as much as two or three thousand years old. Many are now dim, rain and snow having taken their toll on the slightly soluble bedrock. In modern times, acid rain and vandals are the most damaging.

trapped around their hairy bodies like primitive scuba tanks. When the larvae appeared, the local Indians scooped them up with joy, as they were considered a great delicacy. Food was plentiful in normal years — an abundance, if not an extensive variety. It was a comfortable life when natural disasters did not strike, but it came to a sudden and pitiful end when this homeland was found to be rich in gold.

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The Spanish Sight the Sierra Nevada Surprisingly, it was not the gold-hungry Spanish who found the Sierra’s gold. Shortly after Columbus “discovered” the Americas, Pope Alexander VI agreed with the Catholic monarchs of Spain and Portugal to divide between them the parts of the world that had not yet been mapped. Under the terms of a subsequent treaty, Spain could claim lands to the west of the Line of Demarcation, Portugal the lands to the east. So, for three centuries Spain considered that she owned California — not that she knew much about it, of course. The Englishman Francis Drake passed California on his piratical way around the world in 1579 and paused long enough to claim California for England. A century later, Russian traders were hunting seals and sea otters in Pacific waters, and in the early nineteenth century they established settlements at Bodega and Ft. Ross on the California coast to supply the hunters with food. They did this in the face of claims by Spain and England. But these nations were not looking beyond the barrier to the interior that was the Sierra Nevada. In 1542, some of the Spanish, led by Juan Rodríguez Cabrillo, had sailed along the California shore and spotted some high mountains they called las sierras nevadas, but they were not able to see the range we now call the Sierra Nevada. Not until the late eighteenth century did Spain start to bring California into her fading empire. In 1769, Gaspar de Portolá reached San Francisco Bay, traveling overland from the south. Three years later, a group under Captain Pedro Fages made its way into the Sacramento–San Joaquin Delta region and apparently saw the Sierra Nevada from a distance. The churchman who accompanied his expedition, Fray Juan Crespi, wrote in his diary about distant high mountains and made a curious sketch of them. In 1776, when the American Revolution was heating up on the East Coast, two Franciscan missionaries, Padres Francisco Garcés and Pedro Font, accompanied an expedition led by Juan Bautista Anza. Font went with the main body of the expedition to San Francisco Bay. He drew a map showing distant mountains that he labeled the Sierra Nevada. Meanwhile, Garcés, going southward along the San Felipe River (now called the Kern) saw a

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mighty range of mountains he labeled the Sierra de San Marcos. Both Font and Garcés had seen the Sierra Nevada. But there seemed no point in exploring the formidable range, so it remained an eastern barrier to Spanish colonization and a western barrier to the intrusion of others. Had the Spanish known about the golden treasure the Sierra harbored, its history would have been different.

Smith Crosses the Sierra The first non-Indian to cross the range was the trapper Jedediah Strong Smith, one of a group of “mountain men” busy killing beavers (Castor canadensis) for their fur. Beavers had been plentiful in the Rocky Mountains, but by the 1820s trappers had caused them to be in short supply. In 1826, Smith, then only 27 years old, took a party of mountain men toward the Sierra Nevada, hoping to find new beaver country, and beyond the mountains, possibly a Pacific coast outlet to market. They arrived in California by way of a southern route, following the Mojave River, which Smith called the Inconstant, as it sometimes disappeared into the desert sand only to resurface later. With relief from the desert, but no great supply of beaver pelts, they arrived at Mission San Gabriel, where they were welcomed by Padre José Bernardo Sánchez. The official welcome of the Mexican government (Mexico had won its independence from Spain in 1821) was less friendly. Smith and his party were ordered out of Mexican territory and told to return the way they had come. But they did not. Instead they trekked northwestward for 300 miles, keeping the Sierra Nevada to their right (east). When they reached the river Smith named Wim-mel-che (for Indians who lived there, but now called the Kings River), they tried to cross “Mount Joseph” (the Sierra Nevada), but it was the dead of winter and the snow was too deep. When five of the horses starved to death, they gave up. On May 20 Smith tried to cross the mountains again, this time taking two men, seven horses, and two mules. It took them eight days, but they made it, probably at Ebbetts Pass, losing only two horses and one mule. It was the first crossing of the great Sierra Nevada by non-Indians, and it was done from west to east.

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Walker Sees Yosemite Other expeditions followed, some to be stopped and their participants thrown in jail by representatives of the Mexican government. One of them, led by Joseph Reddeford Walker and recorded by Zenas Leonard, traversed the Sierra from east to west and glimpsed Yosemite Valley from precipices on the north. Walker’s tombstone in the Alhambra Cemetery in Martinez says he “camped at Yosemite Nov. 13, 1833,” but there is no evidence that the party went into the valley itself. The men of Walker’s party were becoming discouraged, hungry, and desperate when one of their scouts brought into camp some acorns he had frightened an Indian into dropping. Acorns! Soon, they reasoned, they could go downhill to a more hospitable land where oak trees grew. On the way, they passed through a stand of “incredibly large trees,” becoming the first white men to see the astounding sequoias. Walker and his men continued to San Francisco and Monterey before turning toward home in the spring of 1834. This time, they did not intend to cross the forbidding Sierra, but instead to skirt around its southern end, across the Tehachapis. Then Walker met an Indian who told him of a shortcut through

Figure 9. The “Twins,” in the Mariposa grove. Sketched from nature by G. Tirrel.

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the Sierra Nevada itself. It led through a pass now called Walker (named for him, not the Indian!), and they ended up traveling northward along the base of the Sierra to Owens Valley. The day of the beaver was drawing to a close, but the day of the settler was just dawning. New land, land they could move onto and own, was a bright dream that called would-be settlers from all over the East. The Oregon Trail, to the north, led to land the United States now owned, explored a generation before by the redoubtable Meriwether Lewis and William Clark. Clark, a collector of information about the West, was Superintendent of Indian Affairs in St. Louis when Smith crossed the Sierra; he received Smith’s report with interest and perhaps a touch of envy. He had never seen California.

The First Overland Party The first overland party of settlers to attempt to cross the Sierra was made up mostly of healthy, vigorous, adventure-loving young single men, but it also included Benjamin Kelsey, his young wife Nancy, and their year-old daughter Ann. The group came to be known as the Bartleson-Bidwell party, as it included two men of leadership mold, John Bartleson and John Bidwell, destined to become eminent in what was to be the thirty-first U.S. state. They did not know the area would become a state when in the spring of 1841 the party left the Missouri River. They did know they would be crossing into territory unknown to them, but they did not do so just to be first. They aimed to reach California, perhaps even to become Mexican citizens if that was what it took to acquire land, although they hoped it would not come to that. They reached the Sierra in October, having long ago abandoned their wagons and run low on provisions. They had no idea what to expect or how long the way was, but they could see the mountains were formidable. Some of the young men went up nearby peaks to scout out the land, but to their dismay it seemed to consist of more mountains. At length they crossed the crest and passed into the dense forests on the western side. They passed the Calaveras Big Tree grove (now a state park), noting with astonishment the trees’ gigantic size. (In his memoirs, written much later, Bidwell identified the tree as Sequoia gigantea—a

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Figure 10. Nineteenthcentury horseback party descending toward Yosemite Valley. “Trust your horse,” wrote J. M. Hutchings in 1871, “he makes his own personal safety a study, as well as yours.”

name that had not been applied to them when he first saw them.) The party was ragged and weary and thought the forests would never end. Intrepid Nancy Kelsey carried the baby on her horse when she could, or on foot when she could not. “I looked back,” one of the young men of the party said later,“and saw Mrs. Kelsey a little way behind me, with her child in her arms, barefooted, and leading her horse—a sight I shall never forget” (Farquhar 1965, 42). Nancy Kelsey probably did not care, then, that she was to be the first white woman and Ann the first white child to cross the forbidding Sierra Nevada. On the first of November 1841, the party, still intact and reasonably healthy, reached John Marsh’s ranch near the Sacramento–San Joaquin Delta, the first American settlers to make the crossing.

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Frémont, the “Pathfinder” The Bartleson-Bidwell party was two years in advance of John Charles Frémont (fig. 11), called by his admirers “The Pathfinder.”Frémont, like King, longed to be first in remote places and to name them. He, like most other white explorers, paid no attention to the names already given to places by the people who lived there. In the spring of 1843, he was a second lieutenant in the U.S. Topographical Engineers and had already led an exploring expedition to the Rocky Mountains. Now he was instructed to connect that reconnaissance with the surveys that had been made on the Pacific coast. He made the connection quickly, then on his way home decided to explore the Sierra Nevada, which was not exactly within the scope of his orders. His party made its way to the mouth of the Truckee River at Pyramid Lake, Nevada, where Indians drew him a map of the river, showing it issuing from a lake (probably Tahoe or Donner), and the route to what are now called the American and Yuba Rivers. Had Frémont followed their directions, he would have saved much time, but he did not. He elected instead to go back along the base of the Sierra to about the site of future Bridgeport, then doubled back to the Carson River and made his way into the mountains. He was lost, but did not admit it, and to keep his company’s spirits up, he attempted to cross the range at what today is called Carson Pass. It was February 1844 and the crossing was a very foolhardy thing to do. All the same, Frémont kept notes on his observations, and although lost in the cold, he noted the beauty of his surroundings. The party made it by eating half their horses and mules and on March 6 arrived at Sutter’s Fort. Sutter’s Fort was built by Johann Augustus Sutter, an immigrant from Germany via Switzerland who had obtained a large grant of land from the Mexican government and was creating New Helvetia, a self-contained agricultural community and trading post. Today the fortified part of his settlement is within the city of Sacramento and part of the state park system. In 1844, when it was nearly new, the fort was a square with adobe walls 18 ft (5.5 m) high and 2.5 ft (.8 m) thick—strong enough that arrows and bullets could not penetrate it. It contained granaries and storehouses, rooms for lodging, even a hospital. Sutter was a

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Figure 11. John Charles Frémont, called “The Pathfinder.” In the winter of 1845–1846, Frémont’s exploring party penetrated the High Sierra and surveyed the entire limits of the range. Frémont’s colorful career included, besides exploration, accepting the Mexican defeat in California during the Mexican-American War, being court-martialed, running for president on the new Republican ticket, issuing an emancipation proclamation freeing slaves in Missouri, being convicted of swindling, and being appointed governor of the Arizona Territory. He died broke but remembered.

gregarious man who welcomed newcomers. They would, after all, be his customers. Even the Army would need supplies. Two weeks later, Frémont’s party, having seen some of the high part of the Sierra Nevada, headed east via the Central Valley and Tehachapi Pass. This way, he could follow along the range and note its extent, as Jed Smith had before him, going in the opposite direction. Although Frémont told the politicians in Washington it was next to impossible to cross the Sierra in winter, the next year he set out again for the Sierra, with Christopher (“Kit”) Carson and Joseph Walker as scouts. He split his party, some going with him up the Truckee River (as he had been advised by the Indians to do before) and over what is now called Donner Pass to Sutter’s Fort, intending to meet up with the rest of the party soon. The remainder of his party, under the leadership of Theodore Talbot and guide Walker, went south to Walker Lake and the Owens River (naming the lake for the guide and the river for another party member, Richard Owens). They crossed the range at Walker Pass, intending to rendezvous with Frémont at the Lake Fork of the Tulare Lake, which Talbot’s party took to be what is now called

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the Kern River. To Frémont, though, it meant the Kings River, and the two halves of the expedition never met in the Sierra Nevada. The Talbot party waited staunchly for three weeks until their supplies were nearly gone. They were able to get some supplies from the Indians, which kept them alive. Meanwhile, Frémont pushed his party up into the area that is now Sequoia and Kings Canyon National Parks. But it was midwinter, and a blizzard struck, nearly ending the Pathfinder’s pathfinding. Frémont was appointed civil governor of California by Navy Commodore Robert Field Stockton, and in the conflict of authority between Stockton and Army Brigadier General Stephen Watts Kearny, who marched across the United States to “take” California after the Mexican-American War, Frémont was a casualty. He was between a rock and a couple of hard places. A Navy officer had appointed him to a civil post, yet he himself was an Army officer. He was court-martialed for mutiny and never led another government expedition. His penalty was the surrender of his commission. President James K. Polk remitted the penalty, but because of his arrest, Frémont was not able to complete the report of this last expedition.

Figure 12. Nineteenthcentury party ascending one of Yosemite’s domes by way of an old Indian trail.

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Still, an excellent map of the Sierra Nevada was drawn by Charles Preuss, the cartographer who had accompanied Frémont on three of his expeditions. Preuss was not actually present on this latest Frémont excursion but compiled the map from his own previous sketches, Frémont’s extensive data, and material from other people. Preuss’s artistic map showed topography by hachures but no geology, although the group made sporadic geologic notes. Frémont was bold and daring, and in spite of his rashness (one historian called him a “loose cannon”), during his months in California he had crossed the Sierra and delineated the extent of it. Also during his sojourn in California, he acquired land he called the Mariposa Estate, which proved to be rich in gold, making him a millionaire, but mismanagement and litigation drove him into bankruptcy.

Moses Schallenberger Becomes a Nineteenth-Centur y Robinson Crusoe In 1844, about the time Frémont first arrived at Sutter’s Fort, another party of immigrants loaded up for California. The “Stephens party” consisted of several families, including eight women and 15 children. They were a month later in reaching the foot of the Sierra, crossing in mid-November when snow was beginning to fall heavily. Taking the advice of an old Indian, they followed the Truckee River upward toward its source. They had understood the Indian to say his name was “Truckee” and so they called the river by that name. Truckee may not really have been his name, but at least they made an effort to honor the real pathfinder. This is the route Frémont did not take when the Indians advised him to on his first trip over the mountains in 1844, but he did take it in 1846, albeit too late to be first on the route. Coming to a fork in the river, the party split up, one group of impatient young men going on horseback up the main stream to reach a settlement on the western slope, and to send back help if the rest of the party and wagons did not arrive. The horseback party made good time, soon reaching Sutter’s Fort.

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The wagon party was to take the other fork of the river, up what is now the route of U.S. Interstate 80. They reached Donner Lake, only to be confronted by what looked like an impassable wall of rock. Half the party left their wagons at the lake to wait for spring. Three young men volunteered to stay behind to guard the supplies. The rest decided to try to get the wagons across, no matter how difficult. At times, they took imaginative measures, unyoking the oxen and leading them through narrow defiles to the top of a rock ridge; then virtually taking the wagons apart and boosting the parts up while the oxen at the top pulled with chains. What could not be hoisted the men carried up on their backs. Such measures, although they gave a way for wagons to cross the steep mountains, did not constitute a road. It was left to members of a following party in 1845 to throw large rocks aside and bulldoze a rough track by hand that wagons could be hauled and pushed up, intact. The rock here was granite, and although it did not crumble and generally gave good purchase, some spots, especially where smoothed by glaciers, were so slick the wagons had to be carried over them. It was now deep winter, and the Stephens party’s wagons, so laboriously lifted up, could no longer negotiate the snow, so five of them were abandoned for the winter. By March, the party had arrived at Sutter’s Fort, augmented by Elizabeth Yuba Murphy, born on the trail. Meanwhile, the three young men who had stayed behind to do guard duty at what would be called Donner Lake set about making a rude but fairly serviceable hut, using saplings and brush. Snow kept falling until it was 10 feet deep around the cabin. The two poor cows that were still with them were starving and had to be killed. Facing starvation themselves, two of the young men made crude snowshoes and set out for civilization, leaving behind the youngest, 17-year-old Moses Schallenberger, as he was not able to keep up. He was to become a modern-day Robinson Crusoe, except that he did not have the sea with its bounty, nor cats to dance with, nor goats to keep him company and provide food, and certainly not a Friday. Schallenberger had no plants to harvest, and what was left of the two cows was soon eaten. What he had was snow and more snow. But he was young, brave, resourceful, and intelligent. He managed to trap a coyote, which he roasted in a Dutch oven.“I ate the meat,” he wrote later, “but it was horrible. I next tried boiling him, but it did not im-

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prove the flavor. I cooked him in every possible manner my imagination, spurred on by hunger, could suggest, but I could not get him into a condition where he could be eaten without revolting my stomach” (Farquhar 1965, 46–47). But starving men cannot be choosers, and for three days that was all he had. Then on the third day he caught two foxes, which, roasted, were “delicious.” He grew quite fond of fox as the winter wore on. His limited diet was strong in protein, but weak in vegetables. He had books to read left by his brother-in-law, one of the settlers whose goods he was guarding. But he worried, not just about himself, but about his two erstwhile companions and the others who had gone on, among them his sister. Then one day in February he looked up to see a man on snowshoes coming toward him. He was being rescued. In the summer some of the men went back to the cabin and found it looted. Schallenberger’s vigil had been in vain.

The Donner Party The ransacked cabin, however, was to figure in another page of Sierran history, as it sheltered members of the ill-fated Donner party of 1846 during their winter ordeal. The Donner group was late in arriving at the Sierra Nevada, and the snow came early and heavy. Before the winter was over, only 44 had survived the trip. Thirty-six had died. Those who wintered in Schallenberger’s cabin and nearby resorted to cannibalism as their companions died. Unlike Schallenberger, they did not or could not live off the land, and no Indians offered them food. Later that year, Frémont and his men passed by the cabin where bodies of the starved immigrants still lay about. He had his men bury them and burn the cabins. John Muir said much later that if they had had mountaineering skills they could have had a delightful time in a beautiful place. They did not know they needed mountaineering skills; they had come to farm. Muir was right. It is a beautiful place, and the name Donner is attached to it: Donner Lake, Donner Pass, Donner Summit, Donner Creek, Donner Memorial State Park. Two years later, hordes of prospectors from all over the world began to converge on the Sierra, following the cry of

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“Gold!” and wagon roads and trails in the mountains multiplied. Prospectors will go anywhere to find gold, and they did, mostly concentrating along the foothills, but spreading out everywhere, road or no road.

Snowshoe Thompson Skis across the Sierra Prospectors may be willing to go the back of beyond in search of gold, but they cherish letters from home. In summer, horsemen and backpackers could get through, carrying mail across the range, and by the middle 1850s a primitive coach road was under construction. But winter was another matter. Neither vehicles, nor mules, nor horses could get through, as the snow was usually too deep. But an immigrant, John A. “Snowshoe” Thompson (fig. 14)

Figure 13. John A. “Snowshoe” Thompson, pioneer Sierran skier. For 20 years, beginning in 1856, Thompson carried the mail across the Sierra Nevada from Placerville, California, to Genoa, Nevada (then called Mormon Station), using long skis (then called “snowshoes”) of his own making. Animals and vehicles could not cross the mountains in the deep snow, but Thompson could. He carried no blankets and ate lightly. No blizzard ever lost him. He never had an accident and was rarely paid. His dog sometimes accompanied him, but probably an earlier dog than the one shown here.

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(his gravestone spells it “Thomson”), had mountaineering skills learned in his native Norway that solved the problem. For 20 years beginning in 1856, he carried the mail in winter across the Sierra Nevada from Placerville to Genoa, Nevada, using skis he made from his memories of his childhood. He was the first Sierran skier. He carried no blankets, relying on his exertions and a small night fire to keep him warm. He was never lost, even in the fiercest of blizzards, never had an accident, and seldom was paid. He went eastward over the Sierra in three days, back in two, as he could ski speedily down the long western slope.

A Railroad to Cross the Mountains In 1853, Jefferson Davis was appointed Secretary of War and supervised the Corps of Topographic Engineers survey of three possible railroad routes from the Mississippi River to the Pacific coast. The survey was to go along the 30th and 40th parallels of latitude as nearly as possible. Davis himself thought a route going around the southern end of the Sierra would probably prove to be the most practicable, but before the railroad was constructed the Civil War intervened, and anything “south” was out of the question. Nevertheless, Davis is considered to be the father of the U.S. interstate highway system. He is more commonly remembered as the president of the Confederate States. Lieutenant Robert S. Williamson was put in charge of the exploration through the Sierra Nevada. His conclusions were that any route across the Sierra was impossible or, at least, not practicable. The only good route lay around the end of the mountain block through Tehachapi Pass. Nevertheless, the Williamson party did a great deal of excellent work, railroad or no. (Later surveying for the railroad was done by private enterprise.) Williamson had in his party a geologist, William Blake, who prepared the first geologic map of most of the state, including the Sierra Nevada. It was published with Williamson’s report in 1856 and showed nine rock units, among them granite, metamorphic slate, and basaltic lava, each unit hand painted on each copy of the book.

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The California Geological Sur vey Is Born Blake had good geologic training at Yale, and more geologic experience in California than anyone else. He hoped to be named the first director of the California Geological Survey, but he was not chosen, so he took a professorship at what would become the University of California. Perhaps later he was glad to have been passed over, as he eluded the political difficulties the man chosen encountered; on the other hand, perhaps he could have avoided them. Josiah Dwight Whitney, who was chosen, expected to be selected. He had more or less dreamed up the idea of a geological survey for California; he had worked for other state geological surveys in the East and thought, in view of the gold in California, the state needed one. He marshaled support from influential people including his brother-in-law (who was an officer in a steamship company), a California supreme court judge, and a state legislator. The state legislature, in an act no doubt written by Whitney, empowered a highly scientific survey and actually named Whitney as state geologist, so Blake’s chances had been dim, at best. The legislators who voted for the act establishing the California Geological Survey in 1860 no doubt thought they were employing scientists to point out rich new gold deposits, but that was not mentioned in the legislation. What it did set up was, essentially, a natural history survey, which encompassed, in addition to “rocks, fossils, soils, and minerals,”“botanical and zoological productions.” Whitney was allowed to appoint his own staff, without being obliged to take political appointees of dubious scientific qualifications. His first choice was 32-year-old William H. Brewer (fig. 14), a Yale graduate, who was to be Whitney’s chief assistant and to lead the field parties. His second choice was William Ashburner, who had been educated in mining in Europe. Later, Charles F. Hoffmann, a young German engineer and an expert mapmaker, was added, as well as “young, grassy green, but decidedly smart,” wrote Brewer (1966, 261), paleontologist William Gabb. It was a minute staff for a monumental task. The Survey

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Figure 14. William H. Brewer, the first staff member hired by Whitney, was professor of chemistry and a graduate of the Yale Scientific School. He proved to be an excellent choice. Brewer’s journal, entitled Up and Down California in 1860–64, is one of the more interesting and informative products of the first California Geological Survey, although it was not a formal scientific document and was not published until 1930.

began field work in December 1860 but did not get around to working in the Sierra Nevada until 1863. That year, Brewer and Gabb, the paleontologist, studied the Walker Pass region, then moved northward to Hornitos before Gabb returned to San Francisco. Brewer went to Murphys to join Whitney and Hoffmann to start work on the High Sierra. They camped in Yosemite Valley and climbed a mountain nearby, which they named Mount Hoffmann, the first of the Sierran peaks to be named for a member of the Survey. Near Mono Pass (the northern one) they climbed a high mountain, naming it Mount Dana for “the most eminent of American geologists” (Brewer 1966, 411). At the time, they thought it was the highest in the state and wanted to accord high honors to American James Dwight Dana, a professor at Yale. Whitney returned to San Francisco to do office work, while

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Brewer and Hoffmann almost climbed a peak with ice and snow they named Mount Lyell after the most eminent of English geologists (pl. 10).“Almost climbed” because they reached a point near the top and decided the mountain was “inaccessible.”(Since then, hundreds of climbers, with and without previous mountaineering skills, have climbed it.) Hoffmann became ill, so Brewer joined Whitney, and the two visited the town and mines of Silver Mountain, now a ruin on State Hwy. 4 (the Ebbetts Pass route) near the summit of the range. Brewer went on visiting mining towns and mines up and down the Sierra on his way to San Francisco. It had been a beautiful and instructive trip, but Brewer was discouraged. So much to do, and so few men to do it. Brewer was on the paddlewheel steamer en route from Sacramento to San Francisco to ask Whitney to try to find funds to hire

Plate 10. Hiker in granitic landscape below Mount Lyell.

more field help—a disagreeable task—when two young men accosted him. Could he be William H. Brewer? He could. The young men introduced themselves as Clarence King and James Gardiner, recent graduates of his alma mater, Yale Scientific School, and soon the three were exchanging gossip about home, for Brewer’s benefit, and receiving information about the California Geological Survey, which President Eliot of Harvard had called “the finest State survey ever made,” for the young men’s benefit. By the time they got to rapidly growing San Francisco (which later King would call the monument to California’s march “from barbarism to vulgarity” [Wilkins 1958, 55]), the two young men would be set for an interview with Whitney, and King would be volunteering for unpaid field work with the survey (fig. 15). Gardiner would be sent to the Army Engineers.

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Figure 15. The California Geological Survey field party of 1864, minus one of its members, Charles Hoffmann, a young artistically talented German engineer who made the maps the geologists used for the surveys. Left to right are James T. Gardiner, Richard D. Cotter, William H. Brewer, and Clarence King. Brewer was Whitney’s chief assistant and in charge of the party. King and Gardiner were unpaid volunteers. As time passed, the California legislature became so penurious with funds that others in the Survey were unpaid and worked as volunteers. Some salaries Whitney paid out of his own pocket, as he did for the publication of much of the Survey’s results. In this picture Brewer and King are each holding a mercury barometer used to measure elevations, and King also has a geologist’s hammer. Gardiner is holding a sextant, used for surveying. Cotter seems to be in charge of defense; he has a musket, dagger, and pistol.

King began his work with Brewer through the northern mines—Nevada City, San Juan North, Camptonville, Poker Flat — where, in most of them, huge hoses (hydraulic giants) were washing away the landscape in search of gold. They crossed the Feather River and climbed Mount Lassen, where they could see the pristine volcanic cone of icy, majestic Shasta with lava flows at its feet. Brewer remarked that if this landscape were in Switzerland, he would call it glacial. King and Ashburner were next lent to the Mariposa Estate,

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supervised by Frederick Law Olmsted, architect of New York’s Central Park. Frémont had been the original American owner of the estate, but by now, through mismanagement, he had lost it. When the two Survey men arrived, mining on the Mariposa was in a slump, and Olmsted hoped Ashburner could give him help. Ashburner was kept so busy that King had the task of a general survey of the entire tract. From there, King could see the high peaks of the Sierra and dreamed of knowing them close up, to the

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distrust of Whitney and the dismay of paleontologist Gabb, who could see no use in peaks that did not likely have fossils. Miffed, King began to search for fossils in the gold country where he was and soon found fossils of cone-shaped belemnites (related to squids) that gave proof of the time of the gold belt’s uplift: the Jurassic. He was happy to brag about his find. King did, however, get to realize his dream. He had seen the high peaks from mountains in the gold country and was convinced they were the highest the range could offer — as high or higher than Mount Dana. Finally Whitney agreed to an expedition. After all, unless they could get at least a closer look at them, they would remain a blank on the geologic map, with no one knowing exactly where they were or how high, or what their geology might be. Brewer headed the expedition, accompanied by Hoffmann as topographer, Gardiner as volunteer surveyor, and King as general packer in charge of the mules, while King’s friend Dick Cotter learned the rudiments of packing. On May 15, 1864, they made their way down the eastern side of San Francisco Bay to San Jose. The countryside was in the grip of a terrible drought, and their way was littered with dead animals, now mummified. Dust storms swirled, making visibility almost nil and choking men and animals alike. It was hard to believe that just two years before, the Central Valley of California had been under flood so deep and widespread that steamers could ply their way from San Francisco to Sacramento without benefit of the river.

King and Cotter Climb the High Sierra On the last day of June they reached high country, where Brewer and Hoffmann took a surveying instrument—a theodolite—up a nearby peak, and found it to exceed 13,800 ft (4,206 m). Brewer’s party insisted on naming it for him: Mount Brewer. From here, King could see the high peaks that had excited him so when he was on the Mariposa Estate. They looked far away and inaccessible, but King, who had read European geologist John Tyndall’s work on glaciers in the Alps, thought no mountain was

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inaccessible. He begged to try for what he was calling— correctly — “the top of California.” Reluctantly, Brewer gave permission for King and Cotter, the fittest of the group, to make an excursion to the highest peaks. They set off with six days’ supply of bread, beans, and venison wrapped in their blankets. Brewer and Gardiner accompanied them to the top of the ridge near Mount Brewer. Once again Brewer tried to dissuade them, but King was determined. “The view of those blank granite walls, the thousand granite spires, the vast fields of snow and frozen lakes and the awful desolation were very impressive, but we had made up our minds to try,” King wrote later (King 1970, 62). He and Cotter climbed over and around many of the highest peaks of the Sierra Nevada, reaching spots never before climbed by a white man. (If the Indians climbed in these peaks above timberline they left no record, but it seems unlikely that a young Indian would not want to see the world spread out at his feet, as King did.) As they climbed, they took elevations and distances for a topographic map. Geology without topography is relatively useless, especially in mountainous country, so their pioneering efforts were of great importance. King had one main objective: to stand on top of the highest peak. He saw mountains such as he never dreamed existed outside the Alps: “a hundred peaks,” Brewer had thought during his own climbs,“over 13,000 feet high.”As they climbed, they named the peaks, reserving the highest for their boss, Whitney, although exactly which one that was they did not yet know. They climbed what they thought was the highest peak by roping up and down the steep cliffs. At one sheer rock wall, which King compared to a Yosemite cliff, “I tied the reata [rope] firmly about my body, and Cotter lowered me down to the first shelf; then he sent down the precious barometer and our packs. Next, he made a fast loop in the lasso, hooked it over a point of rock and came down handover-hand, whipping the rope off the rock to which it had been fastened, thus severing our communications with the top of the cliff.” After three hours they got to the bottom of the cliff and strode through fields of alpine grass to the base of the mountain they hoped to climb. The next morning they continued to the top, where King swept the horizon with a level and found they had not climbed the highest peak. Nevertheless,“I rang my hammer on the topmost rock,” King later wrote, “we grasped hands, and I reverently named the grand peak mount tyndall!” (King

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Plate 11. Mount Tyndall. Tyndall was climbed in 1864 by King and Cotter, hoping they had climbed Mount Whitney. Mount Whitney, though nearby, was still too far for them to attempt on that climbing adventure. King named the mountain for John Tyndall, a prominent European professor and student of glaciers. Tyndall’s popular book, The Forms of Water in Clouds and Rivers, Ice and Glaciers (1872), did much to make glaciers appealing to the armchair explorer. In the center of the photo is a large cirque, once host to a long-gone glacier, and a small glacial lake. Mount Tyndall and Mount Whitney are both underlain by granitic plutons, part of the Mount Whitney Intrusive Suite. The suite is 50 mi (90 km) long and more than 10 mi (20 km) wide. It contains the largest individual plutons in the Sierra Nevada and gives the landscape a pallid gray cast. The rocks themselves are coarse grained, with large crystals (phenocrysts) of potassium feldspar set in a finer matrix. In many places, the phenocrysts jut out of the surface because the matrix weathers more readily than the crystals. King used the crystals as handholds to climb the mountains and found them useful for climbing, but painful to sleep on.

1970, 75) (pl. 11). After that came Mount Williamson, named for Robert S. Williamson of the U.S. Pacific Railroad Surveys. But they were not Mount Whitney. King very much wanted to stand on the top of Mount Whitney—whichever that was—the top not only of California, but of the whole of the United States, and ringingly proclaim it “mount whitney,” but he never got the chance. By then, King and Cotter were nearly out of food and had to head back to camp.

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King tried again on July 14. Accompanied by two cavalrymen and a pack horse, he followed an Indian path upward, passing just north of a rounded peak he called Sheep Rock for the Bighorn on its sides. King now chose the wrong route to get to his goal—the top of Whitney—but because he was not correct about which was Mount Whitney, it proved a tiring and fruitless trip. Meanwhile, Brewer and the rest of the Survey party were exploring in the South Fork of the Kings River country. They saw two very high peaks and named them Mount King (later changed to Mount Clarence King) and Mount Gardiner. Months passed, but King kept thinking of Mount Whitney. He and Gardiner tried to climb steep Mount Ritter but failed. They then, following Whitney’s instructions, surveyed the peaks north of Soda Springs, making a first ascent of a mountain they named for John Conness, who had steered the bill establishing the California Geological Survey through the legislature. King left the California Survey shortly after that, but never gave up on Mount Whitney. In 1871, he and a French mountain climber, Paul Pinson, climbed what they thought was Whitney but found it measured too low to be that crowning peak. It was Mount Langley, but the climb was a first.

Plate 12. The Whitney Group. Mount Whitney is the bulky mountain in the right center of the photograph. To the left are Keeler Needle, Day Needle, and Third Needle. All four qualify as fourteen-thousand-foot peaks and are composed of granitic rock.

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Mount Whitney Is Climbed In 1873, three fishermen from Lone Pine climbed the real Mount Whitney (pl. 12) and tried to name it Fisherman’s Peak, but the name Whitney prevailed. Clarence King was chagrined that he had not been the first to ascend the peak, the roof of the nation. He was doubly chagrined that it proved to be what he had called Sheep Rock and passed right by. Later in 1873, King, going down the eastern Sierra on another geological mission, stopped to climb the true Mount Whitney, reaching the top on September 19, a little before noon, but three other parties had made it to the crest before him. King wrote on the climbing record at the top, “All honor to those who came before me.” John Muir found the record and King’s words a month later when he climbed Mount Whitney.

CLARENCE KING (1842–1901)

eologist Clarence King (fig. 17) was the best-known and most highly respected American scientist of his generation, yet today—and even shortly after his death—he is scarcely remembered. Henry Adams called him “the most remarkable man of our time” (Adams 1999). Brilliant in wit and intellect, personally magnetic, a fascinating raconteur with a talent for conversation, he was sought after in America and abroad.“He had a gift,” wrote one of his acquaintances,“for getting unending delight out of life, and for sharing it with all with whom he came in contact” (Wilkins 1958, 4). Mothers with daughters of marriageable age (and no doubt the daughters too) found him particularly attractive. King was descended from a line of Kings (Kinges) that came to Massachusetts from England in the 1640s.Already an old New England family, they went into the profitable China trade about 1800 and were still in it when Clarence Rivers King was born on January 6, 1842, at the family home in Newport, Rhode Island. He began his geological career after graduating from Yale Scientific School by volunteering in 1861 for the new California Geological Survey, headed by Josiah Dwight Whitney, as an unpaid field assistant. One of his first assignments was to survey the peaks of the Sierra Nevada in a party led by William H. Brewer.The geography and geology of the High Sierra

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were almost unknown, and with joy (and Brewer’s permission) King and drover Dick Cotter, both young and in superb physical condition, headed for the highest part of the Sierra Nevada.As they went, they took measurements and made drawings.They were the first white men to climb in much of the region. King yearned to climb high, where he could have long

Figure 17. Clarence Rivers King in the field.

vistas. He had read the work of John Tyndall, a European scientist who studied glaciers in the Alps.Tyndall climbed mountains for the joy of it and also because he wanted to see the effect of glaciers on the Alpine scenery. Mountaineering as a sport began with Tyndall in Europe and King and Muir in America, though each had more than climbing as his goal. King wrote many scientific papers and reports, numerous articles in national magazines, and a popular book, Mountaineering in the Sierra Nevada, first published in 1871 and steadily reprinted since. King left the California Geological Survey in 1866 to take charge of a special government expedition to study the geology and map the heart of the western United States: a 100-mile-wide strip along the 40th par-

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allel of latitude, from eastern Colorado to California, a route the Union Pacific Railroad would be taking. (The 40th parallel runs through or near Denver and Boulder, Colorado; Salt Lake City, Utah; and Reno, Nevada.) It was a plum of a job, and King made a great success of it. Throughout his life, King was a dandy. He had a favorite green velvet suit that he wore on important occasions, except in the field. But even in the field he sometimes dressed for dinner and ate on a white tablecloth under the eyes of soldiers keeping watch to fend off hostile Indians. In 1872, King—and the rest of the world—heard of a wonderful newly discovered gem field in the West.Two “honest miners,” Philip Arnold and John Slack, brought two mysterious sacks to San Francisco, reluctantly admitting they contained rough diamonds. Gossip about the diamonds quickly spread, and soon a company was formed and stock was being sold, not only in San Francisco, but in stock markets around the world.The firm hired Henry Janin, one of the foremost mining engineers of the day, to appraise the new find,“the richest in the world.” The honest miners insisted on keeping the location of the mine secret, even blindfolding legitimate inspection parties. It was not until Clarence King put two and two together that the bubble burst. He was fairly sure the new field must be in the area covered by the 40th parallel survey, and the descriptions of the geography given by those who had seen it made sense. But King had been in that region and was reasonably certain there was no rich gem field there. So during his geological work, he stopped by the place his knowledge of the territory told him must be the setting of the new gemstone mines. On November 3, he and Samuel F. Emmons (later to become the foremost U.S. mining expert) came upon the place: a cold and windswept Colorado gulch bearing a mining location notice for water rights signed by Henry Janin. Dropping to their knees, they soon found a few diamonds and rubies. Next morning they excitedly picked up rubies and diamonds by the handful. But the searchers were soon having doubts.True, they could easily find rubies, amethysts, emeralds, diamonds, sapphires, and spinels, but they were grouped together in a way most unlike Nature’s ways. Many were in anthills, and near each anthill was the footprint of a man. It was a fake. Each anthill had been salted with second-grade gems. Just then a lone horseman rode in saying he and his eight henchmen had been watching King, hoping to find and jump the claims.When he was told it was a swindle, he immediately thought of “selling short” in

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the stock market. Just as bad, he might touch off a rush to this remote and cold mountain valley, perhaps causing many to freeze to death in blizzards. King and Emmons decided King would ride hell-for-leather for the railroad, some 150 miles away, while Emmons would slowly break camp and take their outfit back to San Francisco. The plan worked; King got to San Francisco in time to warn Janin and the bankers and to forestall at least some of the disaster. “I have hastened to San Francisco,” he wrote in a formal letter to the diamond directors, “to lay before you the startling fact that the new diamond fields on which are based such large investments and such brilliant hope are utterly valueless, and yourselves and your engineer, Mr. Henry Janin, the victims of an unparalleled fraud” (Wilkins 1958, 167). King was applauded by everyone except his bosses in Washington, who thought preventing a greater financial disaster was no excuse for not following government red tape. Red tape that would, no doubt, have taken months. King’s success with the 40th Parallel Survey led to his being named the first director of the newly created U.S. Geological Survey, much to Whitney’s chagrin, as Whitney had hoped to take that post himself. But King only managed to organize the Survey when his family lost much of their money, and King thought he could recoup their fortunes by going into business and finding gold mines, as others were doing. He was not particularly good at business, affording him the first failure of his career. He was still working when death overtook him the day before Christmas, 1901, at the age of 59. Some of his friends, among them his climbing mates Cotter and Gardiner, as well as his best friend, Henry Adams, of the presidential family, mourned him greatly. Others of his social group mourned him until his will was read.Then it was discovered that he had been married, and left much of his estate to his black wife and their five children. He was no longer mentioned in gatherings of the “best” people.They could no longer afford to admit that they had known him, as he had broken both a written and an unwritten white law. King might be greatly pleased to know that one of his relatives, Dean Emeritus Robert A. Matthews of the University of California at Davis, spent some of his own career mapping the geology in that same region where King took his marvelous high-country hike.

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CHAPTER 4 PLATE TECTONICS PUTS THE SIERRA NEVADA IN ITS PLACE

Overleaf: The Whitney group of peaks from the east side. The eastern faces of the peaks are steeper and sharper than the western side because the bulk of the Sierra is so high that it interrupts the rain and snow coming from the west, making the western side well watered and the eastern side arid. The western side, with more moisture, has developed soil and is clad with trees; the eastern side, with far less moisture, is much the way it was when the glaciers left. (See also pl. 12.)

after King and Cotter’s wild adventure in the high peaks of the Sierra Nevada, and Brewer’s careful explorations, geographers knew the shape of the range and the locations of its high peaks, and geologists had a good idea of its rocks and how old they were, but they still did not know why the Sierra was where it was or how it got there, or for that matter, why any of the Earth’s mountain ranges are where they are. Science is modern mythology. It seeks to explain the “why” of the world. To do so, we must take into account what we know and build on that. It is not enough merely to consider the facts of Sierran history, although that must be done. We cannot divorce the Sierra from the world; its story must fit with the story of the rest of Earth. For most of the century after King’s climb, geologists were busy inventorying the Earth, trying to map and list Earth’s rocks and to calculate their composition, their chemistry, their location, their age, and their relationship to one another, hoping that in the process a pattern would show. And it has.

A HUNDRED YEARS

Earth’s Patterns Just a few years before the first edition of this book was prepared, a new, unifying concept burst on the geological world, giving geologists a way to explain why many mountain ranges exist where they do. At last they were able to make order out of the inventory, and this concept (or myth, if you will) has captured the American fancy. It was not a wholly new idea; the various parts of it had been assembling for some time. Many people have looked at a globe of the Earth and, noting the close fit of Africa and South America, have wondered if perhaps they were once joined and have since moved apart. The concept is called plate (or global) tectonics, and it has not only made sense out of puzzling areas of the Earth, but has also pointed the way to previously undiscovered mineral deposits. Plate tectonics proposes that in the past the continents were joined and have since drifted or been torn apart, probably more than once. It is a unifying theory that not only reunites continents, but explains how mountains and valleys were formed, what is happening to the seas, and why land and water are distributed as text continues on page 133

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SHIFTING CONTINENTS

e humans feel safer if we think that the reliable ground beneath our feet—the continent we live on—knows its place and has kept it through time, solid and immovable. But a few seconds in an earthquake show us that the Earth can shudder, and a glance at a globe of Earth suggests that the continents may have slithered sideways, as well. The neat match of South America and Africa, for example (particularly if one includes the continental shelves), makes it look as if a giant had ripped them apart.The ancient Greeks, who noticed so much, were unaware of this as they did not have maps showing the Americas. But as early as 1596, only a century after Columbus and those after him alerted Europe to the existence of the Western Hemisphere, the Dutch mapmaker Abraham Ortelius suggested in his atlas that the Americas had been torn away from Europe and Africa by earthquakes and floods. Not a bad guess, but it took until the twentieth century for the possibility to take root in the scientific community.The notion that continents can wander through the ages had as its chief proponent a brilliant German meteorologist,Alfred Wegener (fig. 18), who worked out his theory of “continental Figure 18. Alfred Wegener, pioneer drift” while recuperating from his of the concept of plate tectonics. wounds from World War I. Had he not frozen to death on an expedition to Greenland to deliver supplies to a severe-weather station, his fecund mind would doubtless have moved Earth science ahead by a score of years or more. (He delivered the supplies, but died on the way back.) Wegener was struck not only by the fit of the continents, but by the unusual geologic structures, as well as similar animal and plant species on both sides of the ocean.Wegener’s evidence included climatic records, fossils of tropical plants in coal deposits in Antarctica, and glacial deposits in South Africa. He conceived of a supercontinent, Pangea, that around 200 million years ago began to split apart, its pieces even-

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tually settling into their present configuration. But of course,“settling” is not precisely what they did. Most scientists could not believe Wegener’s ridiculous hypothesis and found many objections to it, including that Wegener was a meteorologist (his doctorate was actually in planetary astronomy) and therefore should not presume to have ideas on geology.They explained the strange locations of polar plants and animals as “polar wandering,” but why the poles should wander no one could say. Nonetheless, they attacked Wegener’s ideas. Geologist Rollin T. Chamberlain of the University of Chicago, a specialist in mountains, wrote a scathing denunciation of continental drift in 1928. He firmly believed that Wegener’s hypothesis would require us to throw out the previous 70 years of scholarly progress. He was right.We have had to unlearn a lot of geology. “What makes the continents move?”Wegener’s detractors asked, and neither Wegener nor his supporters, notably among them Alexander DuToit of South Africa, could answer. Even half a century later, when other imaginative scientists sent an early paper on seafloor spreading and continental drift to a scientific journal, the editor dismissed the paper as “too speculative.” But as more and more evidence came in, particularly from the depths of the ocean—evidence Wegener did not have—it soon became clear that however it happened, continents have moved in the past, are moving today, and will probably move in the future.

they are. To be able to treat Earth as a unit is satisfying to Earth scientists and fires the imagination of nonscientists. Derived from the Greek word for “builder,” tectonics, particularly plate tectonics, tells how the Earth is built. It may seem incredible, at first, to think of continents either drifting or being ripped apart, but remember that time is the friend of geology, and what seems impossible in our limited experience may happen easily in the long reach of time. We know very little about the world beneath our feet. The deepest hole we have managed to dig (for oil) is but six miles deep — scarcely a pinprick in comparison to the 4,000 miles to the center of the planet. We have gone underground only two miles in person to see the rocks, and then in a hot, dark South African gold mine. What little we know, or think we know, comes to us not by direct observation, but by courtesy of earthquakes.

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How We Know By measuring earthquake waves as they pass through the Earth, scientists have derived an idea of what is beneath us—the Earth we cannot see. Earth appears to be a ball, slightly flattened at the poles and bulging at the equator, with a thin crust on its surface. This crust ranges from 3 to 45 mi (5 to 70 km) in thickness, depending on whether it is measured in the deep sea (the thinnest part) or on the continents (the thickest part). The crust contains the rocks and veneer of “dirt” we know—all the granite, all the sandstone, all the soil. Even so, it is so thin in comparison to the rest of the globe that it would be many times thinner than an eggshell is to an egg (fig. 19). Mountain ranges within the crust stand higher than their surroundings; here, the crust has an obvious upward lump. Some mountain ranges, including the Sierra Nevada, consist of rocks of lighter weight than other rocks in the Earth’s crust, or than the

Crust 0–62 mi (0–100 km) thick Asth eno s

phe

Lithosphere re

Mantle

1,800 mi (2,900 km) Outer core (liquid) 3,170 mi (5,100 km) Inner core (solid) 3,960 mi (6,378 km) Not to scale

Figure 19. Inside the Earth. Circles to left show the major divisions of the Earth’s interior: crust, mantle, outer core, and inner core, to scale. An expanded pie shows the Earth’s interior in more detail, but not to scale.

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rock in the subcrustal part. Such mountains seem to have a “root” — a downward projection of lighter material into the heavier rock below, much like an iceberg in water. The portion we see is but a small part of the entire mountain mass, when its root into the crust is considered. Below the crust is the mantle, a region occupying about half the Earth’s radius, making it some 1,800 mi (2,900 km) thick. It contains rock that is more plastic (easily deformed) than rocks at the surface. The outer part of this zone may be the mother of most of the surface rocks; it may be from here that volcanoes take their source, and from which mountains are ultimately derived. Farther down is the Earth’s own core, first the outer core, which constitutes about two-thirds of the whole core and is intensely hot and liquid. Earth’s outer core is 96 percent of the total core by volume. The very center of the Earth, the inner core, may be solid and is thought by most scientists to be chiefly nickel and iron, although one geophysicist insists that the very center is a gigantic nuclear power plant, comprising a ball of uranium five miles wide, which, as it burns and churns, creates Earth’s magnetic field as well as the heat to power volcanoes and continental movement.

How Plate Tectonics Works The principles of plate tectonics are simple, the results profound. Earth’s crust and part of its mantle are divided geophysically into several large plates and a number of smaller ones. These plates include and underlie continents and seas. The North American plate, for example, includes all of North America (including Greenland) except for a tiny splinter along the Pacific Coast. We can see only portions of the plates and can identify and locate them only by geophysical clues. What we see is what is on the plates: the continents, islands, and seas. In only a few places in the world can we see plate boundaries, as most are covered by water. What we can see clearly are the Earth features that we interpret as being produced by plate movement: mountains, rift valleys, volcanoes, and much else. Based on an enormous amount of geophysical data, present theory is that the plates consist not only of the Earth’s thin crust,

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Transform boundary

Converging boundary

Spreading center

Indo-Australian

Philippine

Antarctic

Pacific

Juan de Fuca

Cocos

Nazca

Scotia

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Caribbean

North American

Figure 20. The major tectonic plates of Earth. Most plates carry continents and seas. The plates are in constant, if slow, motion, and that motion has given us Earth’s mountains and valleys.

African

Arabian

Eurasian

but of part of the underlying upper mantle as well, the more solid part. The crust and this part of the mantle together scientists term the “lithosphere” (lithos is Greek for “stone”). These lithospheric plates slide on the plastic lower part of the upper mantle, which is referred to as the “asthenosphere” (from asthenias, meaning weak). Below the lithosphere and asthenosphere lies the lower mantle, which, on the basis of earthquake waves, is thought to be rigid and stiff. It, in turn, overlies the outer and inner cores. So plate tectonics proposes that a soft, plastic layer (the asthenosphere), which lies 40 to 100 mi (60 to 200 km) deep within the Earth, is what the plates slide on; and, as we shall see, the asthenosphere is also what provides new material for the rocks of the Earth.

Earth’s Plates Each plate carries oceanic crust, and most plates have continents on them as well (fig. 20). These are the eight largest: carrying North America, the western North Atlantic, and Greenland SOUTH AMERICAN PLATE, carrying South America and the western South Atlantic ANTARCTIC PLATE, carrying Antarctica and the so-called Southern Ocean EURASIAN PLATE, carrying the eastern North Atlantic, Europe, and Asia excluding India AFRICAN PLATE, carrying Africa, the eastern South Atlantic, and the western Indian Ocean INDO-AUSTRALIAN PLATE, carrying India, Australia, New Zealand, and most of the Indian Ocean NAZCA PLATE, carrying the Pacific Ocean near South America PACIFIC PLATE, carrying most of the Pacific Ocean, including a sliver of California NORTH AMERICAN PLATE,

The plate boundaries are like state lines: they are invisible unless your attention is called to them. Along the San Andreas fault at Pt. Reyes, California, the plates are marked by signs reading “Pacific plate” (to the west) and “North American plate” (to the

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east). Otherwise, to recognize plate boundaries, you need to look at a map of earthquake epicenters and volcanoes, particularly around the Pacific, which marks out those plates clearly. Plates can be thousands of miles across or only a few hundred. They vary in thickness from 125 mi (200 km) or more (plates containing continents) to less than 10 mi (15 km) for young, fresh oceanic plates. All of them move about on the asthenosphere. The plates have been in motion—although they have changed direction, size, and shape many times—for at least hundreds of millions of years. Some geologists have suggested that plate motion began shortly after the birth of the Earth, and plates have been moving, connecting, and disappearing throughout most of Earth’s time.

Mountains in the Sea One surprising feature almost entirely covered by Earth’s waters is an enormous mountain range, the Mid-Ocean Ridge, some 43,000 mi (80,000 km) long. Along this ridge, liquid rock pours out, forming new layers of dark-colored basalt lava and adding to the ocean floor. The layers diverge away from the ridge in both directions. One segment of the ridge, running from the Arctic Ocean to the tip of Africa, is called the Mid-Atlantic Ridge. It is the plate boundary in the Atlantic Ocean, and is marked by a central rift valley. In the middle of the twentieth century, the U.S. National Science Foundation funded a project to traverse the oceans, mapping and taking samples. The project’s report gave us a picture of the ocean bottom that was entirely unexpected. Ocean waters cover not a dishlike surface, as scientists had more or less expected, but mountains and flat-topped volcanoes as much as 2.5 mi (4,000 m) high; ranges and valleys crisscrossed by faults, not unlike the Basin-Ranges country of the western United States (of which the Sierra Nevada is the westernmost part); and through the middle of the seas a 40,000 mi long (65,000 km long) volcanic mountain range, the longest on Earth. The range is Earth’s most prominent topographic feature, unappreciated because it is covered by the waters of the seas. Along the central ridge of this mountain range, volcanoes peri-

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Juan de Fuca Ridge

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nR

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t h east Ind ia

Ce tl an ti

Ind

Sou

d-A

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Equator

E a s t Pacific R is e

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Figure 21. Earth’s longest mountain range. The “stitching” on this diagram of Earth represents the 40,000-mi-long (65,000-km-long) ridge, in several parts, that lies almost wholly beneath the waters of the sea. In a very few places (Iceland, for one) the ridge is exposed on dry land. It is punctured in many places by active volcanoes and volcanic vents.

odically erupt, and molten basaltic lava flows to either side of the ridge. The lava probably comes from deep within the Earth, in the Earth’s mantle. Responding to the pressure of the lava and to other forces, the seafloor spreads apart, moving outward away from the central ridge on either side. Most of the range is underwater, but it does break the surface of the sea in a few places. Iceland is one such place, where new rock is constantly being added by way of the island’s numerous volcanoes. The mid-ocean ridges seem to mark “hot spots” in the Earth. Most of the ocean floor is basalt, a fine-grained volcanic rock, considerably heavier than granite or the sedimentary rocks common on the continents. Now we know that fluid basalt rises up in or pours out of the center of the ridges periodically, to form the lava flows on either side. While the basalt was still liquid, it contained tiny floating crystals of magnetic minerals, especially magnetite. These crystals pointed toward the magnetic (now north) pole, as any compass would. When the lava hardened into rock, the tiny mineral

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compasses were frozen into the position they had assumed, pointing toward the magnetic pole. When next the lava poured out or welled up, it took its place in the center of the spreading ridge. Gradually, older flows migrated to the edges of the basin as more and more flows were added to the center. In this way, the basalt flows became lined up as stripes across the ocean floor, youngest in the center, oldest at the edges. Scientists were able to discover that there were such things as basalt stripes because of these tiny compass needles oriented toward the magnetic pole. After all, the ocean is deep and dark; we have seen little of the bottom, and the samples taken with our meager instruments (rather like a tablespoon on a mile-long string) are neither large enough nor numerous enough to give much of a picture of the deep seafloor. But recording instruments measuring magnetic properties told a surprising story. Each new stripe on either side of the ridge was oriented opposite to the older one (fig. 22). If the new one pointed toward today’s north as the magnetic pole, the next older ones on either side of the ridge pointed south! The one next to that north again, then south, then north, and so on. Why this should be — why the poles should flip-flop— is not yet clear, but that magnetic north has been Lithosphere

Mid-ocean ridge

Magma

Normal magnetic polarity Reversed magnetic polarity Figure 22. How a mid-ocean ridge widens the sea. Left, The ridge cracks open to allow a lava flow to fill its center. Center, The center of the ridge is host to a new lava flow, which shoulders the former lava flow to the side, contributing to seafloor spreading. Right, Yet another central flow moves the other flows to the side. The tan, rust, and brown flows are separated by others, shown here in beige. If the first flow (tan) was emplaced during a time when Earth’s magnetic field was “normal,” that is, north was in the direction it is today, the polarity of the next flow (beige) is “reversed,” that is, north and south have traded places. This has happened many times in Earth’s history. Scientists have calibrated the flows so that the age in years of many of the flows is known.

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changing end for end is clear. Because scientists now have a method of measuring the actual age of a lava flow in years, they can tell precisely when each magnetic stripe was formed. Unless the Earth is expanding, which it does not appear to be, seafloors cannot continually widen with new basalt stripes unless the older stripes go somewhere. In some places the basalt layers dive (by being pulled or pushed or both) back down into the Earth’s mantle from which they came at “subduction zones.” In this way, Earth maintains its shape. These modern subduction zones are the deep-sea trenches; it is here that recycling takes place. Rock is pulled downward into the subduction zone, to be shipped down to the mantle, remelted, and, eventually perhaps, to rise again along a spreading center. This keeps the ocean basins geologically youthful, compared to rocks of the continent. Old rock is cremated and reworked while young magma (molten rock) is born. The process is not quick; it takes millions of years.

How Plates Move Earth’s plates move in several ways: away from each other (divergent), toward each other (convergent), and alongside each other along “transform” faults. Plates also plunge under one another and ride atop one another, so up-and-down movements, although byproducts of horizontal plate motion, are also possible. These motions are not restricted to tectonic plates. The same sort of movement is seen in Hawaii on crust forming on a hot lava flow, and cooks can easily see it in the crust on gravy, particularly if the initial crust is broken up by gentle stirring. The Mid-Atlantic Ridge is a prime example of a divergent boundary. The ridge is a spreading center along which new crust is created by hot molten rock pushing up from the mantle. As each new lava layer is added and flows to each side of the ridge, other older, cooler layers are pushed and pulled toward the side. Here the ocean crust is spreading, moving apart at the ridge axis at the rate of about 1 in. (2.5 cm) per year, or 16 mi (25 km) in a million years. This is far from the speed of an orbiting satellite, but nonetheless, over the past 100 to 200 million years it has caused the Atlantic Ocean to grow from a tiny inlet to a vast ocean that now separates the continents of Europe, Africa, and the

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Plate Asthenosphere Figure 23. Three types of plate boundaries. Where plates are moving away from one another, they are diverging (upper left), hence the name “divergent plate boundary.” Such a boundary is to be found in the sea along the Mid-Atlantic Ridge, where magma rises along the boundary to be expelled as lava. Most such boundaries are covered by ocean water, but one may see the boundary in action at a few places on Earth, such as Iceland, where the boundary is above water, and where active volcanoes intermittently add to the land. A convergent boundary (upper right), in contrast, is one where two plates push against one another, causing mountains to rise. In this manner the Himalayas have reached their great height, and the Sierra Nevada has been pushed upward. A transform boundary (lower) is one in which the plates move parallel to one another. California’s infamous San Andreas fault marks such a boundary.

Americas. This does not mean that the ocean crust is entirely lava, even though much of the surface of the ocean floor is. Near shore, sediments from the land form a wedge out to sea, and even the deep sea has a dusting of debris that has fallen from the surface of the water. Beneath the ocean floor, the crust includes solidified rocks from the mantle, as well as fluid rock that feeds the volcanic centers and provides heat for submarine hot springs. Plates moving toward each other are “convergent” and colliding very slowly. If one oceanic plate (a plate composed of heavy, dark rock such as basalt) meets another oceanic plate, one plate

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generally is pulled and pushed (subducted) under the other, forming a trench. The world’s deepest trench, the Marianas, east of the Philippines, at one spot as much as 36,198 ft (11,040 m) deep, is the site where the relatively speedy Pacific plate converges with the slower and smaller Philippine plate (fig. 20). The oceanic crust of the Pacific plate is subducted under the continents that surround it. If an oceanic plate meets a continental plate (a plate composed of lighter rock formed on the continents — rock such as sandstone), as along the South American coast where the oceanic Nazca plate meets the South American plate, the oceanic plate subducts under the continental plate — here the Nazca under the South American plate. This occasionally causes earthquakes generated deep within the Earth along the plate boundary and within the cool, brittle subducted lithosphere, often lifting the Andes even higher. Some of the subducted plate is remelted and recirculated to the spreading centers. Some stays closer to its last home and supplies molten magma for volcanoes on land. The volcanoes that rim the Pacific Ocean, the so-called Ring of Fire (fig. 24)—including Mount St. Helens in Washington, and two active volcanoes in California, Mount Shasta and Mount Lassen—have this origin. When two plates carrying continents converge, the results can be dramatic. Because both continental blocks are light compared to oceanic plates, neither is deeply subducted. Instead, the Earth’s crust buckles and is pushed upward or sideways. A collision like this between the Eurasian plate and the Indian plate beginning 50 million years ago lifted the Himalayas and the Tibetan Plateau to their great heights. Here the continental crust is about twice as thick as normal. The Himalayas are the highest mountains in the world, reaching nearly 30,000 ft (over 9,000 m). Not all plates are moving outward, propelled by new lava. Some are gliding past one another, not always smoothly, at horizontal displacement zones. This sort of movement is common along the San Andreas fault in California, where it is mostly horizontal, with one side of the fault slipping past the other. The San Andreas fault is about 590 mi (950 km) long and has generated earthquakes for millennia. It is a major plate boundary, separating the Pacific plate to the west from the North American plate to the east. It is one of the very few boundaries between plates that

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Kurile Trench Ryukyu Trench Philippine Trench

Java (Sunda) Trench

Aleutian Trench

Japan Trench Izu Bonin Trench

Puerto Rico Trench

Middle America Marianas Trench Trench Challenger Deep Bougainville Trench

Equator

Tonga Trench Kermadec Trench

Peru-Chile Trench

South Sandwich Trench

Figure 24. The “Ring of Fire” (in red), a zone around the Pacific Ocean where active volcanoes and strong earthquakes are common, and where some of the Earth’s subduction zones are located. Scientists think the areas marked “trench” (e.g., Bougainville Trench) are subduction zones plunging into the Earth’s mantle.

we can see on land. Many such boundaries exist in the ocean, breaking the magnetic basalt stripes into a checkerboard pattern.

What Propels the Plates? Almost as soon as geographers were able to put the continents of the Earth together, with the Americas taking their proper place, thinking people began speculating that South America and Africa looked as if they had once been joined and had moved apart. Elizabethan scientist Sir Francis Bacon entertained the thought but could not prove it. The most vocal advocate of “continental drift” was the German meteorologist Alfred Wegener. He assembled a great mass of evidence but stumbled on the question,“What makes the continents drift?” Even today the problem is not solved. Details as to how and why the plates move is not wholly agreed upon, but it seems clear that they do move. Most scientists agree that convection in the 144

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mantle is probably the driving force. The mobile mantle rock is heated — perhaps partly from radioactive heat and from hot areas left over after the Earth’s formation—then rises toward the surface, spreads out, cools, and sinks back down. In this way, “convection cells” form (fig. 25), the mantle heating, rising, cooling, and falling back and in the process moving the plates along. When a cold plate slab descends into the mantle through a subduction zone to a depth of about 435 mi (700 km), the Earth’s internal heat softens it so that it loses form and flows, producing convection currents in Earth’s mantle. Also, as the inner core crystallizes, enough latent heat is being released to provide energy to keep the mantle convecting long into the distant future. Some plate tectonics experts emphasize that subduction zones are the keys to plate movement. As the cold, dense oceanic slabs sink into subduction zones, they pull the rest of the plate with them, stirring up convection in the mantle, and are thus the Ridge Trench

Lithosphere

” B PULL “SLA

Trench

Asthen osp her e Mantle 435 mi (700 km)

Outer core

Inner core Figure 25. How convection cells in the mantle might power the movement of plates. As a slice of plate (a “slab”) is pulled into a trench (subduction zone), it descends toward the mantle. When it reaches a depth of 435 mi (700 km), Earth’s heat softens it so that it begins to flow. Convection cells, carrying heat, circulate in the asthenosphere and mantle of the Earth, encouraging the plates to carry on their tectonic dance.

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driving engines of plate tectonics. Possibly, as some researchers suggested in 1996, the independently spinning inner core, which whirls faster than the rest of Earth, also exerts a force that contributes to plate movement.

Land Forms at Last Early in Earth’s history, continental centers (cores)—dozens of them—called “cratons” by geologists, formed slowly, finally rising above the sea waters. The cratons became parts of the plates that slid around and occasionally crashed into one another. Where the plates collided, mountains formed, and volcanoes were active. The cratons, containing the oldest rocks on Earth, still are the centers of today’s continents. North America is made up of seven ancient cratons that stuck together about two billion years ago. Once the cratons formed, bits and pieces of new land and seafloor were added to them. Eventually they all coalesced into one gigantic landmass that split apart, joined again, and has since been continuing to split apart and move around, with the pieces bumping into one another. California is made up of a number of fragments that were pasted (“docked”) onto the beginnings of California at various times and from various places (fig. 26). These Earth fragments scientists call “terranes.” They consist of what we normally think of as “terrain” — an area of land— plus parts of the seafloor and all the Earth’s crust below, and perhaps even a fragment of Earth’s mantle. In the area of Kings Canyon and Sequoia National Parks in the Sierra Nevada, four terranes have been identified: the Kings-Kaweah Terrane, the Kings Terrane, the Goddard Terrane, and the High Sierra Terrane. The Kings-Kaweah Terrane, for example, consisting partly of rocks of the seafloor, was apparently transported thousands of miles northward during Mesozoic seafloor spreading. The limestone blocks of the terrane contain tiny microfossils of the fusilinid type of foraminifers, known to be about 250 million years old, thereby giving us an idea when the limestone was deposited, which was obviously sometime before its transportation. Moving, breaking apart, spreading—all this goes on constantly. The land builds outward toward the sea and then is raised from the waters into mountains. The sea widens by adding new

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Russia

an uti Ale

Koyukuk Terrane

Tre n

Wr a

Alaska

a Ter elli ng

ch

rane

PACIFIC PLATE

Canada

Alexander Terrane

sca dia

Trench

JUAN DE FUCA PLATE

Ca

NORTH AMERICAN PLATE

Island arc

San Andre

Submarine deposits Ancient ocean floor

u as Fa

Attached fragments

Guerrero

Convergent boundary

United States

lt

Ancient continental interior (craton) Divergent boundary

Sonomia Terrane

Figure 26. Plate tectonics features in western North America. The Pacific plate and the North American plate meet one another at Point Reyes. Terranes (Koyukuk, Alexander, Guerrero, and Sonomia) have migrated from afar to attach themselves to western North America.

Terrane

Transform boundary

Salton Trough

Mexico

East Pacific Rise

rock from the depths of the Earth, and by pushing against the continents, forces them back. As the sea is widened in the center, its plate’s edges plunge into deep trenches to lift and crumple the continental plate edges into mountains, causing earthquakes, and, eventually, to be pulled farther downward into Earth’s mantle where they are melted into new rock. It is an endless cycle.

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CHAPTER 5 SEAS OF LONG AGO

Overleaf: Mount Ritter (13,157 ft [4,101 m]) and Banner Peak (12,945 ft [3,964 m]) loom over Thousand Island Lake. Ritter and Banner mark the northwestern end of the Minaret group. The two mountains harbor small glaciers, as do some of the other Minarets. The mountains were carved into their present jagged shape by glaciers from the Great Ice Age, which tore blocks of metamorphic rock from the mountains to throw onto the glacier, which carried them into the valley below. The peaks themselves were not overridden by ice, so they did not acquire a rounded shape. The small, present-day glaciers on their slopes are not remnants of the Ice Age but are new glaciers formed within the last thousand years. Geologist Willard D. Johnson and John Miller first climbed Banner Peak in 1883. The first ascent of Mount Ritter was described by John Muir in The Mountains of California (1894). He climbed it in October 1872, starting from Thousand Island Lake, itself a relic of the Ice Age.

billion years of the region that has become the Sierra Nevada is veiled, as the rock record of the Earth’s beginnings does not appear in these mountains. The first pages of Sierran history that remain for us to read begin in rocks laid down about 540 million years ago (Cambrian Period). Other, earlier pages endure in the structurally related White and Inyo Mountains to the east, which probably reflect happenings in the Sierra; but in the Sierra Nevada proper, this is the oldest now known. These old rock pages hold the story of the mountains — of their landscapes and inhabitants, of the times they were not mountains at all but part of the vastness of the sea. Here and there are surprises, too: pockets of valuable minerals and deep caves, for example. THE FIRST FOUR

The Old Rocks and What They Tell Us Geologists of a century ago recognized two great groups of ancient rocks in the gold belt; one group that was Paleozoic in age, and one Mesozoic. We know that the Paleozoic rocks are more than 250 million years old, and that the Mesozoic ones were formed more than 65 million years ago. They constitute evidence of what the Sierra was like in those long-gone ages. During the early part of the Paleozoic Era, more than 400 million years ago, the western margin of the North American continent extended roughly from southeastern Idaho across central Nevada and into southeastern California. In basins along the shore a wedge of sediments accumulated. Now converted to rock, these beds range in thickness from .6 mi (1 km) on the south to 6 mi (10 km) on the north, showing that the basin deepened to the north. Seaward, beyond the basin and the continental mass, were islands that formed “island arcs” (similar to today’s Aleutian island arc) near where the northern Sierra Nevada and Klamath Mountains are today. These arcs were later added to the continent by action related to a subduction zone. What these rocks and their younger relatives tell us is that the sea washed over the land of the Sierra while the long ages rolled by, probably for more than 500 million years. Virtually all of the older rocks in the Sierra Nevada (called “bedrock” by miners, and

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“subjacent series” by earlier geologists) are marine in origin; that is, they were formed at the bottom of a sea, though most not in its deepest part. Judging by the kinds of rocks and the few fossils in them, the eastern part of what is now the mountains was closer to shore than the western part during Paleozoic time from about 540 million to 250 million years ago. Somewhere east of today’s mountains lay land. Very little is left of the creatures that lived in those ancient seas. Fossils are scarce in the Sierra, largely because most remnants of life were destroyed when the layers of rock that entombed them were pushed upward, bent, twisted, and faulted during plate tectonic episodes that created the range.

A Backward Look Suppose you were to travel backward in time and downward into the depths of the sea of 300 million years ago (fig. 27); you would surely have an altogether different view of the Sierra than we have today. Perhaps you would see a few small fishes swimming among the reefs and darting behind tall stems; or perhaps not, for no old fish remains are preserved in the Sierra. What seems to be a waving forest on the floor of the shallow sea is made up not of plants, but of animals. Sea lilies (crinoids) have stems and what appear to be leaves. Their tops, stirring gently in the warm water, look very much like flowers. If you peer closely at them, you will see that their stems as well as the petal-like parts of their “flowers” are made up of hard discs. When they die, these stony pieces fall slowly to the seafloor to be preserved in rock for millions of years. Nearby are corals, too, forming thick-stemmed “trees.” They are, in fact, animal cities: colonies that may be connected to the seafloor by the bodies of their own dead, with only their outer parts alive. For all that they look like a garden, these creatures do not live in soil or transform sunlight into food, as land plants do. Little soil or sunlight reaches the depths of the sea. This ocean bottom is sandy, and even the rocks that lie tumbled about are covered with a rough crust. This, too, is an animal: a “moss animal” (bryozoan) covering the rock so completely that you are not sure which “rocks” are made entirely of animals and which have cores of stone.

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Figure 27. Floor of the sea as it may have looked in late Paleozoic time, 300 million years ago, in the region where the Sierra stands today. Crinoids, bryozoans, brachiopods, straight and coiled cephalopods, starfish, snails, corals, sponges, and trilobites crowd the underseascape.

You cannot actually see the billions of tiny creatures floating in and on top of the water. If you could, you would see that some have minute clamlike shells, others have unique whorls and chambers, and still others resemble beautiful crystalline pinwheels. Some are the young of bryozoans, minute colonies on their way to becoming new aggregations of animals. These colonies are produced sexually by mating within the stem of the older colony, staying there to ripen before spinning out to found a new bryozoan city. Others, the tiny, elaborate crystalline ones, are radiolaria, floating through the water in clouds so thick you can see them, even though you cannot distinguish any single individual. These and the tiny-shelled foraminifers are being lured by the crinoids

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into their waving tentacles. The crinoids wash the minute ones through their bodies by the millions, using the built-in sieves in their flowerlike heads to sift out the tiny animals—now their dinners—then shoot the water back into the sea. Moving slowly along the seafloor here on the shelf of the continent are large, coiled cephalopods. They resemble snails; but there are snails here, too, and clams, recognizable as relatives of those of our own time. You know some of the animals, attached to rocks and coral, as “lampshells” (brachiopods), but there are far more of them than you have ever seen before. As you move westward and downward through this ancient sea, the scene darkens, for sunlight cannot penetrate deeply into the water. You feel fewer creatures about you as you move down the steep continental slope. Suddenly there is light and a great turbulence; a rush of warm water engulfs you. You are heading toward an undersea volcano erupting incandescent lava on the seafloor. The sea is boiling so furiously that you cannot quite see the source. You stop moving down the slope and travel across it instead.As you do, a mass of mud, sand, and rock shoots past you at perhaps 80 ft (24 m) per second. It is a “seaslide”—a turbidity current— speeding downward, a tumbling mass of sand and rocky debris. The danger is great. It is a good time to return to today to see more safely what has been preserved for us of those seas of yesteryear.

Adding Real Estate What has been preserved tells a surprising tale. The edge of the continent is where exciting events take place. Here, plates subduct or crash into one another; and here, too, smaller pieces of plates, sometimes having wandered from half a world away, crash into and are added to the continent. Every continent has had out-ofplace (exotic) pieces of terrane annexed to it. Western North America is a mosaic of patches accumulated (“accreted” is the technical term, although “fused,”“docked,” and “pasted” all mean roughly the same thing) through the ages. One large terrane attached itself to western North America in late Devonian time, some 380 million years ago, pushing almost to Utah. Another, the

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Sonomia Terrane, an island arc, docked in North America about 250 million years ago. The “suture” of the Sonomia (the place where the terrane attached) lies near Golconda, Nevada, at Nevada’s Sonoma Range. Sediments ceased to be deposited in the Paleozoic sea when ocean floor rocks were shoved over the margin of the sea, lifting mountains. This event — the shoving of the sea bottom rocks over the new continent — has been called the Antler Orogeny. “Orogeny” is an old, but still useful term for mountain building. (In earlier years mountain-building events were called “revolutions,” but the term has been abandoned.) Gradually, erosion leveled the mountains built by the Antler Orogeny, and rifting of the tectonic plate broke up the mountains and allowed the sea once more to cover the land. This all happened very slowly, except for seaslides and volcanoes, as in our imaginary trip, and an occasional earthquake. The “crash” took thousands or millions of years. Then once again, for 100 million years, the sea covered the land. The time of fairly quiet seas was ended when tectonic plate collisions, called the Sonoma Orogeny, brought various terranes from elsewhere to what would be the Sierra, among them the Kings-Kaweah Terrane (a complex ancient fault zone). While the seas covered the land, they piled up layer upon layer of sedimentary debris including sand, mud, skeletons and shells of animals, and pieces of older rock and gravel. As new layers were heaped upon older ones, the weight and pressure, together with chemical cement carried in the seawater, gradually consolidated the loose sediment into hard rock (pl. 13). In the eastern part of the sea basin, limestone and its relative, dolomite, accumulated from the remains of organisms, while in the western part, volcanoes were erupting undersea and their lava mingled with limestone as well as chert, a rock composed of silica (SiO2) containing microscopic fossils. The basin extended from Alaska far down into Mexico. Doubtless, many of the volcanoes rose high enough to protrude above the water as islands, making island arcs. To the west of the islands was a subduction zone. After millions of years of gradually shallowing seas, the great basin, about 700 mi (1,000 km) wide and perhaps 3,500 mi (5,600 km) long, was full of sediments, which solidified to become rock. The pile of rocks that had accumulated, consisting of bedded sedimentary rocks—limestone, sandstone, shale—as

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Plate 13. Red Spur (12,771 ft [3,893 m]) and the Kaweah Peaks. All of the Kaweah Peaks on the skyline are designated as “Class 3” climbs; that is, climbers should carry a rope in case they need it. The peaks are all composed of metamorphic rock. Some metamorphic rock, because it breaks rather easily into scree, generally makes more dangerous climbing than granitic rock.

well as volcanic rocks and other rocks added during subduction, was very thick, probably more than 13 mi (20 km). The sea was probably always less than that in depth; in fact, it was likely only about 2 mi (3 km) deep. Thirteen miles of rock can accumulate in two miles of water because as the sediments accumulated, the basin sank. While this was going on, the seacoast had migrated westward to about the center of what is now the Great Central Valley. At the beginning of the Mesozoic Era (250 million years ago), there was still no vestige of the land that was to be California, but by Jurassic times, two active trenches developed off the California coast, one dipping eastward and one westward. Both were destroyed by the arrival of the Smartville Terrane, which docked in California in the Jurassic, and for the first time, land appeared in the Sierra Nevada. By 140 million years ago (late Jurassic) the basin was caught in the jaws of a great pair of pliers. One jaw was the North American plate to the east, carrying the North American continent, the

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other the Pacific oceanic plate to the west. The pressure exerted by these pliers bent, twisted, and folded the rocks, lifting them up into mountains. The squeezing produced a great deal of heat, which melted some rocks and greatly changed others. This mountain building, which created the Ancestral Sierra Nevada, is called the Nevadan Orogeny. The pliers began squeezing about 140 million years ago and stopped about 118 million years ago. The enormous basin and the mountains built from the sediments in it by plate movement changed the geography of the western part of the North American continent profoundly. Although we know little about the topography of those mountains, we do know they extended from Alaska to Mexico. Our present Sierra Nevada is just a small part of that range.

Caverns Because movement of the great plates twisted, gnarled, and upended the once horizontal rocks, the caves and caverns that had developed in limestone layers were upended, too. This makes

Plate 14. A visitor, wearing cave garb preferred by speleologists, walks carefully through a passage in Crystal Cave, Sequoia National Park. Overhead are rock shields that have allowed mineral curtains to form along their lower edges. Mineral-charged water dripping through thousands of years created all of the formations.

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TABLE 10

Some Caves in the Sierra Nevada Open to the Public

The Sierra Nevada has hundreds of solution caves, several of them open to the public. Cavers do not publicize the locations of caverns, unless entrance to the cavern is carefully regulated. For would-be cavers, danger lurks in the unfamiliar darkness, but the danger of damage to the cave is even greater than danger to the caver. BLACK CHASM CAVERN

Near Volcano, El Dorado County

Unusual helictites. A National Natural Landmark.

BOWER CAVE

Stanislaus National Forest

Hosted community dances around the turn of the twentieth century. John Muir said it was a “delightful marble palace” in 1869. Apply to the U.S. Forest Service for permission to enter.

BOYDEN CAVERN

Near Cedar Grove, Kings Canyon National Park

Developed in Boyden Cave roof pendant (see pp. 164–65), one of the largest of the dozens of pendants in the southern Sierra Nevada. Commercially operated.

CALIFORNIA CAVERNS

On Cave City Road, 9 mi (14.5 California's first commercial cave (also km) east of San Andreas near called Cave City Cave), discovered in 1850; Vallecito, Calaveras County 1.47 mi (2.37 km) long. Current tour operator offers raft trips in the underground lakes and rivers. Early visitors included Mark Twain, Brett Harte, and John Muir. CRYSTAL CAVE (CAVERN)

In Sequoia National Park, near Has 2.42 mi of mapped passageways in Giant Forest Village. Closed in pendant 300 ft (91 m) wide and 600 ft winter. (183 m) long. Arrangements to visit must be made in advance through the National Park Service.

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MERCER CAVERNS

Near Murphys, on Sheep Ranch Road, Calaveras County

Discovered by a gold prospector in 1885, who found no gold but did find human bones (four adults, one child, and one infant). Caverns opened to the public in 1887. Unusual frostlike deposits of aragonite.

MOANING CAVE (CAVERN)

On Moaning Cave Road, near Vallecito, Calaveras County

Explored by gold miners in 1851. The “moaning” was caused by wind passing over the entrance. Contained human remains.

exploring Sierra Nevada limestone caverns somewhat of an upside-down mountaineering effort. The Sierra Nevada has many limestone caves — more than 225 in the southern Sierra alone — several of them open to the public (table 10). The longest cave in California is Lilburn Cave, in Kings Canyon National Park, which has 14.10 mi (22.69 km) of mapped underground passageways. The cave is set aside for scientific study. In Sequoia National Park, the name of 1.59-mi-long (2.56-km-long) Hurricane Crawl Cave gives an idea of the difficulties of exploring it. Caverns (solution caves) in the Sierra Nevada are intriguing, as they are far outside our normal alpine experience. The palpable darkness of the strange underground world lends mystery and an aura of danger. The caverns may be festooned with draperies, stalactites, stalagmites, columns, and many other odd forms made of glistening solid rock. They were formed in limestone that is hundreds of millions of years old, but the caves themselves are much younger—probably less than a million. These caves began when rain falling on the land surface seeped into the rocks along tiny fractures and pores. The water worked its way downward until it reached the level surface of standing underground water (the water table), where the rock and soil below were saturated. As it went through the surface vegetation and then soil and rock, the water absorbed some carbon dioxide, creating a weak carbonic acid solution. This acid slowly dissolved calcite, the mineral of which limestone is made, excavating cavities and passageways. The dissolving solution became rich in calcium bicarbonate, which was carried off in the natural underground plumbing.

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Plate 15. Visitor inspecting one of the pools and the formations surrounding it. Pools are often found in caves. Some pools contain “cave pearls,” small rounded structures formed around a nucleus while being agitated by dripping water. Cave pearls are rare, partly because visitors can easily put them in their pockets.

As the water table lowered, which water tables do as river valleys deepen and tap off some of the underground water, the cavities cut by the acid were left stranded above the water table, in the unsaturated zone where air could enter. But rain still sent water that had picked up carbon dioxide through the rocks, again dissolving portions of the rocks and leaving the solution rich in calcium bicarbonate. When the water reached the cavities, the carbon dioxide gas escaped into the air (as it does when a carbonated beverage bottle is opened), leaving the mineral calcite and water. The calcite was deposited as dripstone, creating speleothems, the fanciful deposits that decorate caverns (pl. 15). The higher parts of most caves, where water comes directly from the soil, contain the largest speleothems. The complete chemical reaction is shown in fig. 28. The most familiar speleothem is the stalactite, an icicleshaped mass of calcite that hangs downward from the ceiling (pl.

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calcium bicarbonate solution Ca2+ + 2HCO 3− →

carbon dioxide

calcite

water

CO2 ↑ + CaCO3

+ Η2Ο

Figure 28. Chemical reaction showing how calcite, which composes cave speleothems, is broken down from calcium bicarbonate in the Earth.

16). It forms as drop after drop of water slowly trickles from the surface through the cave roof. As each drop hangs from the tip, it loses carbon dioxide and leaves a film of calcite. Another drop adds another ring, and slowly a cylinder develops, a “soda straw” stalactite, very fragile, but sometimes reaching a meter or more in length. Surprisingly, such a stalactite is a single crystal, with the molecules rearranging themselves as each drop comes through the straw. If the flow of solution is too much for the narrow soda straw, it may run along the outside of the straw. The water flowing on the outside of the stalactite drops its calcite faster at the top, accounting for the often-seen carrot shape. This new calcite on the outside does not become part of the original crystal; instead, it adds wedge-shaped crystals to the exterior, which then grow out-

Plate 16. Light shining through stalactites in Crystal Cave. Crystal is not a “dead” cave, as attested to by the drops of water hanging from the ends of the carrot-shaped formations.

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Plate 17. Park ranger showing visitors the mysteries of cave formation in Crystal Cave. Here a stalactite from the ceiling has reached a stalagmite growing up from the floor, making a column. One stalactite from Moaning Cave, also in the Sierra Nevada, grows at the rate of about 2.4 in (6 cm) in 1000 years.

ward. When light shines through such a stalactite, it sparkles gloriously. Some of the charged water may drip off the stalactite onto the floor of the cave, gradually building up a stalagmite. If the stalactite grows downward to meet the upward-growing stalagmite, a column develops (pls. 17, 18). It is a slow process, perhaps taking as long as 100,000 years. Where the ceiling is inclined, water trickling down its slope may form draperies, some of which hang freely from the cave ceiling. Impurities in the calcite may impart striking color to the draperies. Bands of white, red, and yellow are common; in mining areas, copper impurities may provide green and blue, and iron may add brown. Here is a fragment of John Muir’s story of his 1869 trip into Cave City Cave (California Caverns) as he told it in The Mountains of California (Muir 1894, 152):

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Plate 18. Calcite flowstone, Boyden Cave. Mineral-laden water dripping from the roof has flowed over this structure, depositing rumpled layers of calcium carbonate. Excess water, reaching the edges of the formation, drips off the sides, creating stalactites. It takes many years— probably thousands—for such formations to be created. Thoughtless visitors or vandals, by “collecting” a stalactite, not only destroy the formation, but rob others of the opportunity to see the cave in its pristine glory. The Sierra Nevada has many caves, but to protect them we have listed only those caves that are either commercial or regulated by the National Park Service or the U.S. Forest Service.

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Though cold and bloodless as a landscape of polar ice, building was going on in the dark [of the cave] with incessant activity. The archways and ceilings were everywhere hung with down-growing crystals, like inverted groves of leafless saplings, some of them large, others delicately attenuated, each tipped with a single drop of water, like the terminal bud of a pine-tree. The only appreciable sounds were the dripping and tinkling of water falling into pools or faintly plashing on the crystal floors. In some places the crystal decorations are arranged in graceful flowing folds deeply plicated like stiff silken drapery. In others straight lines of the ordinary stalactite forms are combined with reference to size and tone in a regularly graduated system like the strings of a harp with musical tones corresponding thereto.

Helictites — thin, twisting, or spiraling cylinders or needles — are among the many other cave decorations. Anyone who has watched icicles form on a slanted roof may see forms as thin as straws along the roof edge; if more snow falls, the weight of it slowly moving down the roof slope may bend the thin icicles or twist them, if they are firmly anchored to the edge of the roof. Calcite helictites may have a similar origin—pressure—but other factors, such as chemical changes, may also influence the development of the thin helictites. Cave helictites grow as water seeps slowly through the narrow helictite core, never forming a drop, but depositing calcite around the hole in the tip. The time it takes nature to produce these marvels is quite long. Stalactites rarely grow more than .08 in. (2 mm) a year, and often less. Thoughtless visitors who break off a stalactite rob others of something that may have taken thousands of years to grow.

Changing from One Form to Another The scattered remnants of metamorphic rock embedded in granite were originally visualized by geologists as fragments of notyet-digested local (country) rock sometimes hanging from the roof (top) of the magma chamber (a natural container for an underground mass of fluid rock), like pieces of jewelry suspended from a necklace, so “roof pendants” is what they were named. Dozens of them are in the High Sierra, especially in the three

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WIND UNDERGROUND?

isitors are often surprised that caves are cool and pleasant when the day outside is hot or when the outside temperature is below zero. Crystal Cave in Sequoia National Park, for example, maintains a temperature of 48 degrees F (9 degrees C) both winter and summer.The extremes of hot and cold in the outside air penetrate only a few feet into the cave, and through thousands of years, the rock far below has adjusted to changes, keeping its thermostat set at a steady temperature. Crystal is not the only cave with a pleasant, steady climate, because the temperature of a cave is usually equal to the average annual temperature of the area outside. The adjusting rock thermostat produces wind underground, which is another surprise. In summer, warm air enters from outside through openings, is cooled by the interior rock, and in cooling pulls more air in behind it.The cooled air inside the cave is pushed by that coming in from outside, setting up a cave circulation, eventually pushing cooled air outside, giving visitors the pleasure of a cool wind emanating from the cave. In winter, the reverse is true. Cold air enters, is warmed, and a new circulation sets up, allowing air warmer than the air outside to blow out the cave entrance. Wind blows strongly in many large cave systems, including Carlsbad Caverns in New Mexico, and Wind Cave and Jewel Cave in South Dakota. Winds can roar through the cave, sometimes reaching more than 80 mph (130 km per hour).

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national parks. The largest ones are more than five miles in length, among them 1,500-ft-thick (457-m-thick) Boyden Cave pendant, host to Boyden Cavern. The roof pendants were originally layered sedimentary or volcanic rocks that have been recrystallized as the process of metamorphism worked during plate movement. Metamorphic rocks have contributed color to the high mountain landscape (pl. 19). Black Kaweah Peak, Black Divide, and Black Giant Peak all take their color from dark metamorphic rocks. Rainbow Mountain is named for its variously colored metamorphic rocks. Mountains of granitic rock, in contrast, are generally light colored, but some are confusingly dark. All the rocks in the Sierran Paleozoic and Mesozoic systems are now metamorphosed. In many places, it is possible to tell

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Plate 19. High mountain rockscape.

what they once were; when this is possible, geologists have called them by their original names — limestone, shale, sandstone— rather than by their more correct technical metamorphic names. This has, perhaps, promoted an understanding of the geologic history of the range but has confused those trying to learn to recognize the rocks. If you read geologic reports on the Sierra Nevada, especially those published recently by the U.S. Geological Survey, you should bear in mind that all the Paleozoic and Mesozoic rocks except those younger than the granite are metamorphosed, even though they may be designated by names that indicate their origin rather than what they are today. Many of the old beds once were limestone, siltstone, shale, and mudstone, with some volcanic rocks mixed in. Today, many of them can simply be called “hornfels,” which means that they are even- and fine-grained metamorphic rock. A good field name for a rock that breaks in layers along mica minerals is “schist”; “slate,” for one that breaks along flat planes but does not show shiny mica flakes; “marble,” if the rock is calcareous and crystalline; or “quartzite,” if it has been derived from sandstone and is crystalline. Many names have been applied to the metamorphic rocks of the Sierra Nevada. If you look up an unfamiliar rock name in the glossary, you can discover what general type of rock it is, and what word is used in this book for its general field name. The study of the process of metamorphism—literally,“change of form” — is in its youth. This is somewhat surprising, because many of our most valuable mineral deposits have been the result of metamorphism. In the language of geology, the metamorphic process is described as the application of heat, pressure, or both,

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Plate 20. Metamorphic rock. Bedding planes are light transverse lines.

on rocks, changing them from one form to another. Obviously, this definition does not include many changes of form that the rocks undergo, perhaps without the benefit of heat or pressure beyond that of the Earth’s surface. Weathering—the chemical change of minerals due to rain, snow, sun, wind, and other Earthsurface forces — is surely a change of form. The rusting of metal is, also. Yet these are, largely for simplicity, not included as part of the metamorphic process. Neither is the consolidation of sediments — mud, sand, gravel — into rock, although pressure and perhaps heat are surely involved. Nevertheless, in the broadest sense, all these processes are metamorphic. At the other extreme, where heat or pressure is so great that some rocks within the depths of the Earth are liquid and can digest other rocks completely, the metamorphic process is so complete that it has become igneous, involving fluid rock. We cannot then easily distinguish metamorphic rocks from igneous ones. At a subduction zone, heat and pressure are so intense that some rocks of the plate are melted above the zone, and some of the resulting magma rises to produce volcanoes; the melted rock remaining below the Earth’s surface will, other things being equal, cool to form granitic rock. Some rocks, however, will not be subjected to enough heat and pressure to melt, but will undergo the “change of form”described by metamorphism. Changes in chemical composition and physical form of the minerals that compose the rock itself occur while the rock is solid, which gives the minerals a different aspect from those crystallized from a liquid. Commonly, metamorphic rocks tend to be “foliated,” to break along certain planes. This is due to the arrangement of metamor-

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OPHIOLITES: THE SEA’S SECRET

n 1892, the German geologist Gustav Steinmann visited Marin County, where he saw a sequence of rocks that reminded him of rocks in the Alps. It was a succession of serpentine, pillow lava, and red chert containing fossils of tiny radiolaria. Hikers today in the Golden Gate National Recreation Area are familiar with these striking rocks. In 1905, Steinmann published a paper on the odd rock succession, calling the grouping “ophiolite” (ophis is Greek for “snake”), but which others soon called “Steinmann’s trinity.” He was convinced they were rocks formed in the deep sea. Plate tectonics geologists of today agree with him. Ophiolites are found throughout the world, from the Himalayas to the Caribbean, from Mount Olympus to New Guinea.They form in the deep sea, near volcanic centers.The Sierra Nevada has several ophiolitic complexes that arrived in California from elsewhere, including, among others, the Kings-Kaweah Terrane in the High Sierra and the Smartville complex of the gold country. Serpentine is thought to be rock of the Earth’s mantle, altered by the addition of water. If the rock were not altered, it would be peridotite. In some places, the ophiolite sequence includes unaltered peridotite. Pillow lava, a peculiar rock shape, was long a geologic puzzle. One geologist in the early part of the twentieth century suggested that the

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phic minerals, which tend to flatten themselves against the pressure on them. In schist, for example, sheets of mica are formed into fairly regularly shaped “books,” so that you can take the books apart into sheets— flakes — theoretically down to one molecule in thickness. If the books are twisted, or oriented at random, it is much harder to flake them apart. Mica is the most obviously oriented mineral and the easiest to identify, but other minerals line up also. It is not that the minerals actually turn to become flattened against the pressure, but rather that the whole chemistry of the rock is reworked, using the old constituents (occasionally adding or subtracting some) to make wholly new minerals that grow in this flattened fashion. In some places, where metamorphism has been intense, the rocks are wholly recrystallized, their original parents identifiable with great difficulty or not at all. Most Sierran rocks have not been this drastically changed, unless they have been totally remelted.

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pillows were the result of lava cooling underwater. He was proved right when, in 1975, geologist James G. Moore donned a wet suit and followed a steaming lava flow into the sea off Hawaii and watched pillows form. (Moore is also an expert on the Sierra Nevada. In his career, he has mapped geologically much of the terrain King and Cotter saw on their wild hiking adventure.) Usually at the top of the ophiolitic sequence (though sometimes capped by limestone) is chert, generally the product of shallow seas. Chert, chemically identical to quartz (silicon dioxide, SiO2), may have accumulated from organisms or from an excess of silica from exploding undersea volcanoes. That ophiolites do come initially from the deep sea has been shown by scientists of the research vessel Glomar Challenger, who brought up cores of ophiolite drilled from beneath the seafloor. In the Smartville block of the Sierra Nevada, the sequence consists of a layer of metamorphosed gabbro, a middle layer of basalt, and an upper layer of pillow lava and related volcanic products. It does not have a layer of chert.The Smartville forms a belt in the foothills of the Sierra Nevada near Oroville. It is as much as 25 mi (40 km) wide and at least 4 mi (6.4 km) thick, and perhaps more. It has been dated radiometrically at 160 million years.

In many Sierran rocks, the planes along which the rocks break are not straight, but wavy. These waves are clues to the rock’s history. By painstaking geometric analysis, some geologists have undertaken to decipher the direction and, to some extent, the amount of pressure the rock has undergone at various times. The few Sierran studies that have been made using this exacting technique indicate that the story of these old rocks is quite complex. The older metamorphic rocks of Mesozoic age— those that formed before the granite backbone—are to be found in the same general areas as the still older Paleozoic beds. It is very difficult to tell the two groups apart unless they lie adjacent to each other. Where they do, a close look shows that the older, Paleozoic group is tilted at a different angle than the younger, Mesozoic strata. This lack of parallelism marks a time of unrest in the Earth, when mountain-building forces were at work. It is technically called an “unconformity.” The types of rocks in both groups

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Figure 29. “Tombstone rock,” metamorphosed volcanic rock that crops out as isolated slabs in the gold country. It is the product of undersea volcanoes of 140 million years ago, now upended and changed by mountain-building forces. A field of such slabs reminded early miners of an untended cemetery, hence the name “tombstone rocks,” “gravestone slate,” or “gravestone schist.”

are similar. They have been changed from layers of sand, mud, and lime to sandstone, shale, and limestone, and now, after metamorphism, we see them as uneven layers of slate, schist, phyllite, hornfels, and marble (table 2). Metamorphosed volcanic rocks are prominent among the

Plate 21. Pillow lava is formed when hot molten lava runs into water.

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old rocks in the gold country (fig. 29). Some of them once were “pillow basalts” (a rounded form that lava takes when it flows into water, such as into the sea or out of volcanoes on the ocean floor [pl. 21]), in places surrounded by red chert. If you look at the chert through a microscope, you may see skeletons of the Radiolaria that served as food for the larger animals in those ancient seas. The chert lenses are still recognizable, but the volcanic rocks, whether they were pillow basalts, lava flows, or volcanic ash falls, are harder to identify. Most of them have become schist. In places in the high country, the Mesozoic and Paleozoic groups can be separated by their color when weathered. The Paleozoic ones are reddish brown on their exposed surfaces, whereas those of Mesozoic age have turned gray. Mixed in among or next to the old rocks are bodies of serpentine, a shiny green rock derived, perhaps, from material brought upward from the Earth’s mantle. Through the processes of mountain building it has been altered from primordial Earth material to green rock.

See for Yourself The best way to become familiar with any of these old rocks is to see them in the mountains, where you can study their outcrops. It is much more difficult to understand a rock that has been sepa-

Granitic rock Metamorphic rock West

East

Figure 30. Cross section showing the arrangement of igneous and metamorphic rocks in the Sierra Nevada. To the west, metamorphic rocks can be seen along the foothills; in the range crest, you see mostly granitic rock, but here and there a remnant of metamorphic rock remains as a reminder that the sea once covered the area where the range is now. Such isolated fragments of rock are called “roof pendants,” meaning that they hang down into the rock that was under the roof of a molten magma chamber.

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SERPENTINE: THE CALIFORNIA STATE ROCK

Plate 22. Serpentine, common in the Sierra Nevada, is a rock in the sense that it may consist of several different minerals, as rocks do.

erpentine (or serpentinite), the California state rock, is a green, shiny, metamorphic rock altered from such dark-colored igneous rocks as peridotite by the addition of water to its chemistry (pl. 22). Serpentine often feels slick or greasy. It consists largely of lizardite and chrysotile, both minerals composed of sodium silicate. Geologists consider serpentine to be the remains of rock from the Earth’s mantle below the oceanic crust. For this reason, the distribution of serpentine provides im-

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rated from its natural context. One of the most pleasant ways to see a great number of exposures of these rocks is to drive along State Hwy. 49, the Mother Lode Highway, from its beginning at Oakhurst near Mariposa to its end at State Hwy. 89. The drive from Yosemite on the Priest Grade road spreads out a superb exhibit of metamorphosed rock, stacked upright for inspection. Some of the oldest rocks in the Sierra are exhibited in the panorama at Convict Lake, near Bishop. Almost the whole Paleozoic story of the Sierra Nevada is told in these rocks.

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portant clues to the forces that helped construct and elevate the Sierra Nevada. Serpentine can be found in most Sierran counties, sometimes forming distinctive greenish or dark outcrops or road cuts. Because serpentine contains chrysotile, an asbestos mineral, in 1990 serpentine containing more than 5 percent asbestos was prohibited by law from being used for road surfacing. When Goodwin Knight became governor of California in 1953, word came to the California Division of Mines that his wife,Virginia, the First Lady, would please like to borrow 78 colorful rocks, each about 8 in. (20 cm) in diameter, to use as centerpieces at a dinner she was hosting for prominent political spouses. Especially, she requested, she would like that “pretty green rock that looks like jade” (Hill 1953). Except for small samples from scientific study, the Division had only a few rocks they used to supply schools with Earth science material, nowhere near 78 of such a large size, and the dinner was to be the next day. But a First Lady is a First Lady, and two young geologists took a pickup on a hurried trip to gather samples.They collected and carefully trimmed several specimens of red chert, several of serpentine (“that pretty green rock”), some glistening black peridotite, and other colorful rocks. It was a weighty project.An 8 in. (20 cm) piece of serpentine, for example, having a specific gravity of about 2.5, would weigh about 45 pounds, making a total of nearly 2 tons! When the two tired geologists delivered the rocks to Sacramento, a horrified Mrs. Knight exclaimed, “Oh, no! I wanted seven or eight!”All was not lost.The Division of Mines had gathered enough specimens to supply schools with small samples for some years to come. It was Governor Edmund G. Brown Sr., Goodwin Knight’s successor, who signed the bill making serpentine the California state rock.

For a leisurely view of the old metamorphic rocks, including serpentine, park in Plumas-Eureka State Park and see them in safety on foot. Or drive to the Lakes Basin or Sierra Buttes Recreation Area, where you can see the rocks without taking your life in your hands. The greatest thickness of older Mesozoic rocks in the high country is to be seen in the wildly beautiful reaches of the Ritter Range. From the John Muir Trail northward from the Devils Postpile, climb the steep trail upward to Shadow Lake to pass

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through a series of volcanic and sedimentary rocks of Triassic and Jurassic age that have been metamorphosed into bands of sparkling minerals. Some minerals are fairly rare; one zone that has the manganese-rich epidote mineral, piemontite, as a prominent constituent can be followed as a reddish band for two miles through the gray schist upward and northward nearly to Thousand Island Lake at the foot of Mount Ritter and Banner Peak. Another hike through metamorphic rock starts at Tuolumne Meadows and goes to Mono Lake through Bloody Canyon, a principal route for Sierran foot traffic before the Tioga road was built. It is called Bloody Canyon in memory of the poor pack animals who scraped their sides against the sharp rocks, leaving the rocks bloody. There, at Mono Pass, you may study old metamorphic rocks on the slopes of Mount Gibbs or Mount Lewis and pick over the tailing of the Golden Crown mine. Parker, Koip, and Kuna Peaks to the south are also within a day’s walk of the pass. A walk over the shoulder of Mount Lewis into Parker Pass, up Koip and Kuna Peaks, then back along the sheared, metamor-

Plate 23. Serpentine and ancient seafloor sediments.

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Plate 24. View west toward Convict Lake Basin. The rumpled area at the foot of the peaks is a group of moraines. The buildings on the left are Hot Creek State Fish Hatchery, which supplies two and a half million trout for lakes and streams in the Sierra Nevada. The hatchery is particularly successful because it is located on a region of hot springs, warm springs, and fumaroles that derives its heat from magma underground. The spring area has been active for some 300,000 years, although spring activity waxes and wanes. The hot, mineral-laden water chemically alters the surrounding rock.

phosed zone below Kuna Crest is a geologically revealing, if tiring, journey. Atop Parker Peak is an outcrop of dense black hornfels that breaks into smooth fragments. Sierra Buttes, to the north, provides a less exhausting trip. These buttes are composed of light-colored metamorphosed rock that had been volcanic ash and breccia, exploded from undersea volcanoes millions of years ago. Table 2 lists other places to see examples of metamorphic rock. They are suggestions that may start you on your way to understanding the Sierra Nevada better and will surely provide impetus for many interesting drives and hikes into the wilderness.

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CHAPTER 6 GREAT IS GRANITE

Overleaf: Half Dome, Yosemite National Park. The most famous of the many domes that grace Yosemite, Half Dome is not half a dome, but almost a whole one. It is composed of nearly unjointed Half Dome granodiorite, andd therefore has a more massive shape than many of Yosemite’s other features, and has been less altered by erosion. (See also fig. 32 and pls. 25 and 32.)

and the Yo-Semite is its prophet!” wrote the Reverend Thomas Starr King in 1860 (King 1962). And surely, if you walk the high country or the deep canyons, you do get an overwhelming impression of granite — of the granite that is the very heart of the mountains. Sierran granite — more properly called granitic rock because you must include granite and all its relatives—is part of a vast field of rock that underlies the mountains. It is exposed along the crests and extends downward an unknown distance into the Earth.

“GREAT IS GRANITE,

The Sierra Nevada Batholith Geologists call such a field a “batholith,” meaning “deep rock.” The Sierra Nevada Batholith extends southward into Mexico as the Southern California Batholith and northward into the Klamath Mountains, where the serrate peaks of little-known Castle Crags are a rock-climber’s challenge. Although the granite underlies about 15,000 sq mi (38,800 sq km) of the Sierra Nevada, nearly a tenth of the area of the state of California, it is part of a much larger granitic belt along the western side of North America that extends from Mexico to Alaska. The Sierra Nevada Batholith and other batholiths up and down the western coast developed as two tectonic plates encountered each other. One, composed of oceanic lithosphere, was subducted beneath a plate composed largely of continental lithosphere. In the late Jurassic, 150 million years ago, the giant Farallon plate (the oceanic one) began to be subducted under the North American plate (the continental one) and continued to be subducted until the Farallon plate was almost entirely consumed more than 100 million years later. Today, two plates still encounter each other along the Pacific coast, the Pacific plate and the North American plate, and at least in part of the region of the encounter, plates are not being subducted but are slipping past one another along the San Andreas fault. It was during the millions of years of subduction that the Sierra Nevada Batholith formed. As subduction proceeded, slivers were scraped off the Farallon plate and added to the front of the overriding North American plate. As the Farallon plate was pulled downward, it became

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Winds carrying ash eastward Eroded sedimentary material Continental crust Older granites Km Miles 200 170 0 Old oceanic crust my my Farall Granite on Pla te Movin magma g n 50 o r and s North American Plate ubduc th ting moving northwest 50 100 Mantle Mantle 114 million years ago 150

Km Miles 0 50

200 my

114 my Granite magma

170 my

50 100 150

103 million years ago

Km Miles 0

114 103 my my

Granite magma

200 170 my my

50 50 100

Sediments eroded during granite intrusion Sediments eroded during block tilting Coast Sierra Nevada Km Miles Ranges 0 114 103 90 my my my ? North America n Plate 50 San Andreas Fault 50 100 Mantle 150

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200 my

White-Inyo Mountains

90 million years ago Owens Valley

150

170 my

hot, and at a depth of about 60 mi (97 km) water and other volatile components were baked out and rose upward, causing rock above them to melt. The mantle above the downgoing slab — itself hot — began to melt, forming fluid rock that rose and melted the continental crust above. In this way, pockets of fluid rock (magma) of different compositions were formed. Some rose to the surface to be spewed out in volcanoes; others cooled to form the granitic rock of the Sierra Nevada Batholith (fig. 31). Although the batholith is exposed in patches throughout the Sierra Nevada, the exposures do not form one huge, uniform mass of cold, gray granite as you might think. Instead, the batholith is a group of individual masses or “plutons” (named for Pluto, god of the underworld) that are distinguishable from one another. Pluto is a prominent actor in the story of granite. Fluid rock that cools underground is called “plutonic rock.”

What Is Granite? Most of us recognize granite as a hard, gray rock that has a saltand-pepper appearance (pl. 25). A close look with a hand lens shows that the salt-and-pepper effect is created by the individual grains that make up the rock. Some grains are glassy (these are quartz); some are shiny pink, white, or gray (these are mica or feldspar); a few are black or brown (these are mica, amphibole, or pyroxene). In older geologic reports on the Sierra Nevada, most of the range is referred to as “granite.” In modern reports, the word Facing page: Figure 31. Granite, the heart of the matter. In these four diagrams, the dean of Sierran geologists, Paul C. Bateman, shows how the Farallon plate, in subducting, spurred the development of Sierran granite. The most widespread Sierran granites intruded into older rocks between about 114 and 85 million years ago. Hot magma, derived from partial melting of the mantle beneath the North American plate as water was released from the subducting Farallon plate, rose from the subduction zone and mixed with and melted lower crustal material, changing its chemistry. Pockets of granite (plutons) developed, spurted toward the surface, and consolidated at different times during the period of their formation. Some magma broke the surface in volcanic eruptions, but most cooled underground as granite.

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“granite” is scarcely to be found, although “granitic rock” is common, as are “granodiorite,“quartz monzonite,” and “tonalite,” accompanied by such strange words as “trondhjemite.” The reason for this is that geologists have honed the word “granite” into a technical term and have redefined it so that many more words now cover what “granite” used to mean (and still does, to those who work in the granite industry). Bear in mind that the essential feature of all plutonic rocks is that individual mineral grains can be seen by the unaided eye, and that many of the grains have sharp, straight edges. In some places of the world, evidence has led some geologists to conclude that granitic rocks are not necessarily formed from a

Plate 25. Granitic rock (granodiorite) specimen.

hot melt. They reason that granite may, instead, be formed cold, where it is, by a reorganization of its chemistry, aided by chemical ions migrating through the atoms of the rock. The process has been called “granitization” and was a radical new idea in the 1940s. Yet Professor Joseph Le Conte had some such idea in mind when he wrote in 1870: “I have seen everywhere the strongest confirmation of the view that granite and granitic rocks may be but the final term of sedimentary rocks. In Yosemite I could trace every stage of gradation from granite into gneiss, and, since leaving the Yosemite, from gneiss into impure sandstones. On Mt. Dana sandstones are easily traced into gneiss” (Le Conte 1971, 95). Confrontations between plates are so violent—even if slow—that anything might happen. On the other hand, evidence supporting the idea that most Sierran rocks cooled from a hot body is fairly convincing. One

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such piece of evidence is this: a close look along the edges of many of the plutons shows that the rock is finer grained there than in the center. This is what would be expected of crystals forming in a cooling liquid; the slower the liquid cools, the larger the crystals grow. If the hot liquid meets the cold rocks of the rest of the Earth, as it does along the pluton’s outside edges, it is rapidly cooled there, and whatever size the crystals have reached when the edges solidify is the size they will be. In the center, where the liquid does not meet the chilling edge, the crystals can go on growing until the whole pluton becomes solid rock unless something disturbs the magma. No one has seen granite form in the Earth from fluid rock, but laboratory and field deductions have given this picture of how it may happen: The liquid itself is hot and thick—perhaps like mush—and crystals continue to form until there is no more liquid, either because it is suddenly chilled to rock or totally crystallized. The thick liquid does not always have room for geometrically beautiful crystals to form; more often, the crystals are pushing one another for room to grow, so that few, if any, are allowed to form into what should be their perfect shape. When crystals do have enough room and time to grow perfectly, they are greatly admired and highly prized. By laboratory experiment and careful observation of rocks in nature, geologists have determined which minerals tend to be the first to form from the hot liquid, and which tend to be the last. Minerals that take longest to melt—that require the most heat— are those that form first as the hot liquid is cooled. Those that melt easily — at a low temperature — stay in solution longer while the liquid cools, precipitating only when the mass reaches the point at which these minerals would melt if it were being heated. In general, dark-colored, heavier minerals that are calcium, iron, and magnesium rich, including pyroxene, amphibole, and dark mica (biotite), form first, just as they melt last when heated (pl. 26a–c). They and some of the feldspars—those with the most calcium in them — are the principal constituents of the dark side of the granitic rock clan. As the melt cools, other minerals are crystallized: feldspars rich in sodium, together with the dark mica; finally, feldspar rich in potassium, followed by the clear mica, muscovite (“isinglass”), and, last of all, quartz (pl. 26d–f). Most igneous rocks contain silica (silicon dioxide; white

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a.

b.

Plate 26. Rocks are composed of minerals. Each of the rocks shown here is made up of one mineral or several. These minerals are a few of the major ones that compose igneous rocks; they were crystallized from fluid magma—the dark minerals first, the lighter ones later. When igneous rocks are weathered, these same minerals may become the ingredients of sedimentary rocks. All of these minerals are “silicates”; that is, they contain silica (SiO2), the oxide of the metallic element silicon. (a) Pyroxene, characterized by short, stout crystals. (b) Amphibole, which shows two strong cleavage directions. (c) Biotite, a dark-colored mica, scattered among lighter-colored quartz and feldspar. Biotite weathers to a golden hue, which may be mistaken for gold, but biotite is much lighter in weight. (d) Feldspar, which weathers to clay. (e) Muscovite, a light-colored mica. (f) Quartz (which is entirely SiO2) is broken into fragments by wind and weather and is the principal constituent of the sands of Earth.

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c.

d.

e.

f.

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quartz is pure silica). As the various minerals form, some silica in the fluid is used up in reactions with iron, magnesium, sodium, calcium, and aluminum in making the minerals. The remainder of the melt, which by now is almost entirely silica, cools into quartz. As the minerals form, they tend to settle toward the bottom of the liquid, if it is undisturbed. The reason is that the earliest minerals to form are also the heaviest, heavier even than the liquid itself. The next mineral in order is lighter in weight than the first (usually in color, too), but still heavier than the liquid. It, also, sinks, making a layer on top of the heavier, darker ones already at the bottom. In theory, if the liquid is never stirred or interfered with in any way, a series of plutonic rocks should form that grades from dark, heavy rocks (such as peridotite) through intermediate gray ones (such as gabbro and diorite) to granite, the lightest in color and weight. One of the last products of crystallization is likely to be granite in the technical sense: coarse-grained and composed of quartz and feldspar that is rich in sodium and potassium. Most Sierran granitic rocks are not rich enough in potassium to be called granite; instead, they contain a higher percentage of sodium- and calcium-rich feldspar and technically fall into the granodiorite or quartz monzonite or tonalite group. In geological parlance, because the liquid melt from which the rocks crystallize is called magma, this entire process of crystallization is called “magmatic differentiation.” We can think of many factors that might determine what kind of rocks (“differentiates”) and how much of them any magma will produce. The original chemistry of the liquid mass is certainly one factor; the possibility of sloshing or stirring as the crystals cool is another (pl. 27); the melting of the Earth’s rock that encloses the liquid mass surely is a third. In mapping the batholith, geologists have discovered that tonalite (formerly called quartz diorite) is the dominant rock type in the western part of the batholith, while granodiorite is dominant in the east. This is also true of the other batholiths along the western United States. James Moore, who studied this trend, called the boundary between the two rock types the “quartz diorite line” (nowadays he would call it the “tonalite line”). The study of volcanoes has revealed that there are many dissolved gases in molten rock. As these find their way to the surface through cracks in the rock or through volcanoes, the chemistry

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Plate 27. Inclusions in granitic rock. Some inclusions, like these, are closely related to the granitic rocks enclosing them. They probably were formed in the same magma chamber, the dark fragments consolidating first, but because of shaking or disruption in the chamber were broken apart and thrown into the still-fluid magma. Other inclusions may be of older rocks of any type, such as fragments of old metamorphic rock caught up in granitic plutons.

and physics of the mass are altered, and the course of crystallization may change. If volcanoes on the surface of the Earth throw out liquid magma from the pluton, such a process surely affects the chemical content of the remaining liquid; but how and to what extent is bound to be different for each magma and for each pluton.

A Throng of Plutons Although the principles that govern the history of magmas are the same for all plutons, each pluton is an individual and has an individual history and an individual name. In size, the plutons range from less than 1 mi (.6 km) in diameter to more than 500 sq mi (1,300 sq km). The very large ones are big enough to be called batholiths themselves.A few large ones have smaller ones grouped

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Plate 28. Orbicular granite. The orbicules are formed from rock fragments suspended in magma. As the fragments are buoyed upward by the hot, rising fluid, mineral material is precipitated on their surfaces. When the fragments are sloshed about and rolled, concentric layers of magma cover them.

around them. Some of the plutons are separated from one another by areas of metamorphic rock, or by thin bands of other types of igneous rock; others butt sharply against one another. As you might expect, a body as large as the Sierra Nevada Batholith includes hundreds of plutons, more than a hundred in Yosemite National Park alone. Most plutons are roughly oval, and one group of 53 that was measured averaged 7.5 mi (12 km) in length, although some were as long as 50 mi (80 km). They were about half as wide as they were long. The long dimension was oriented parallel to the long dimensions of the metamorphic roof pendants (about 30 degrees west of north), giving a directional grain to the mountains that geologists think is the result of the subduction process and reflects the position of former tectonic plate boundaries. Overall, Sierra Nevada plutons contain an average of 68.5 percent silica (SiO2), but darker ones contain less than 62 percent silica and lighter ones more, with tonalite averaging 52 to 65 percent and true granite 73 to 76 percent. In spite of this relative uniformity of size and composition, most individual plutons are distinct from one another. text continues on page 192

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THE LIFE STORY OF TUOLUMNE INTRUSIVE SUITE

he history of Sierran granite is revealed as more complex the more it is studied.The Sierra Nevada Batholith, for example, consists of hundreds of individual plutons. Many of the plutons are related to one another, either by age, by geography, by chemical composition, or all three. When a group can be shown to be related as “cousins,” probably derived from the same magma source, they are known as an “intrusive suite.” The Yosemite area has many intrusive suites, among them the Intrusive Suite of Yosemite Valley (which includes, among other plutons, the 108million-year-old El Capitan Granite) and the Intrusive Suite of Buena Vista Crest (including Bridalveil Granodiorite). The first to be identified as a suite, and one of the most thoroughly studied, is the Tuolumne Intrusive Suite, which includes four main plutons: (1) The granodiorite of Kuna Crest is 91 million years old and is exposed at Glacier and Washburn Points and the Tioga Pass entrance station. It is a dark rock, showing many stretched pebbles. (2) The Half Dome Granodiorite is 87 million years old and is exposed near the Awahnee Hotel and Mirror Lake (fig. 32). It is a medium- to coarse-

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Figure 32. The flat bottom of Yosemite Valley, once a large lake. Half Dome is in the distance; the Awahnee Hotel is visible through the trees. Today, trees cover the grass, the last stage from lake to meadow to forest.

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Plate 29. Phenocrysts (large crystals) of light-colored feldspar in Cathedral Peak Granodiorite. The shape of the boulder somewhat mirrors the shape of Cathedral Peak itself, on the skyline.

grained rock. (3) The Cathedral Peak Granodiorite (pl. 29), which is 86 million years old and the largest pluton of the suite, comprises Pothole and Lembert Domes. Cathedral Peak is noted for its large feldspar crystals, as much as 3 in. (7.6 cm) long, set in a fine-grained ground mass. (4) The Johnson Granite Porphyry is the youngest of the suite, although its exact age in years is not known. It is light colored and may be seen in Tuolumne Meadows along the Tuolumne River.The emplacement of the Johnson Granite Porphyry was not quiet; probably, volcanic detonations accompanied the event. In fig. 33, drawing A shows the initial intrusion and solidification of the granodiorite of Kuna Crest along the margin of a magma body. In B, new magma has cut the Kuna Crest rocks and solidified in its center as the even-grained portion of Half Dome Granodiorite. In C, a new surge of magma cuts into both the Kuna Crest rocks and the already

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solidified portion of Half Dome Granodiorite, this time forming the porphyritic phase of Half Dome Granodiorite. In D, a third spurt of magma cuts into the solidified rocks and cools as the Cathedral Peak Granodiorite. Finally, volcanoes erupt as the Johnson Granite Porphyry completes the picture. Figure 34 shows the final stage of the creation of the Tuolumne Intrusive Suite.The top of the volcano blew off, leaving a caldera and volcanic ash and debris (left). Most of the rocks and debris were removed by erosion, leaving today’s topography (right).

B

A Magma Magma

Magma

D a Road

Ti

og

C

N

0

15 miles

0

25 kilometers

Figure 33. Stages in the life of the Tuolumne Intrusive Suite. In A, granodiorite of the Kuna Crest solidifies around magma (center). In B, a surge of fresh magma solidifies as the even-grained part of the Half Dome Granodiorite. In C, new magma solidifies as the porphyritic part of the Half Dome Granodiorite. This part contains the big crystals. In C, a third surge of magma solidifies as the Cathedral Peak Granodiorite. Last of all, the Johnson Granite Porphyry (D) is emplaced.

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Volcanic deposit from eruption of Johnson Granite Porphyry Johnson Granite Porphyry Pre-existing rock intruded by Cathedral Peak Granodiorite Cathedral Peak Granodiorite Rocks removed by erosion during last 85 million years Today’s land surface

Magma

Tuolumne Meadows

Tuo lum

n

Tioga Road e R iv e

r

Johnson Peak

About 85 million years ago, before erosion Same area today, after erosion

Figure 34. Last stages of the birth of the Tuolumne Intrusive Suite. The Johnson Granite Porphyry intrudes the Cathedral Peak Granodiorite and erupts through a volcanic caldera, throwing out volcanic ash and debris onto the Earth’s surface. Later, the volcanic deposit and some of the underlying rock is eroded away, leaving today’s landscape. Left, The area of the Tuolumne Intrusive Suite about 85 million years ago. Right, Today’s landscape after erosion.

Some plutons are clearly zoned, with dark minerals to the outside edge, and lighter ones toward the middle. This is to be expected, as when the fluid material burps upward from the main body of the batholith to form a pluton, the outer edges cool first, and the darker minerals separate out. The center is last to cool, and by that time most of the dark minerals are gone and only light-colored, lightweight ones remain, giving a bull’s-eye effect. Because the bull’s-eye is on a scale of miles, it is most easily visible on a map. One such zoned structure is the much-studied Cartridge Pass pluton, 20 miles northwest of Independence; two oth-

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ers are the 86- to 91-million-year-old Tuolumne Intrusive Suite in Yosemite National Park and the 84-million-year-old Whitney Intrusive Suite, occupying 460 sq mi (1,191 sq km) chiefly in Kings Canyon and Sequoia National Parks. The top of Mount Whitney is in the very irregular bull’s-eye of the Whitney Suite. As a pluton cools, it shrinks and its surface and edges crack, giving the material that has not yet cooled an opportunity to slip into the cracks and cool there. These narrow bodies that fill the cracks are called “dikes,” for their fancied resemblance to water dikes (pl. 30). The face of El Capitan in Yosemite Park shows many dikes of dark, fine-grained diorite. If you look at El Capitan in summer, when climbers are attempting to make their way to the top, you may hear those around you mark the climbers’ progress by referring to the dike they are near. El Capitan itself is composed of 108-million-year-old El Capitan granite that contains larger crystals (“phenocrysts”) that obviously cooled slowly before the main body of El Capitan granite . Many dikes are fine grained and light colored (“aplite”), but a few have exceptionally large crystals half an inch or more in diameter, particularly of mica, quartz, and feldspar. Such exceptionally coarse-grained plutonic rocks sometimes contain rare elements and are known as “pegmatites.” In many of the granitic areas of the Sierra, the rock is spotted.

Plate 30. White dike cutting through dark hornfels.

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On close inspection, the spots prove to be patches of either metamorphic rock or of darker igneous rock. Certainly, many pieces of the older metamorphic rock must have been torn off and melted in the hot magma. The fragments left for us to see are those that never were fully digested, either because they were the core of a larger mass that did not get completely melted, or because they were pulled into or surrounded by the magma when it was too cold to dissolve them completely.

Batholith Biography The Sierra Nevada Batholith is far from being perfectly understood. Now that we can use radioactive clocks to place rocks within time, it is possible to begin to unravel the batholithic history (fig. 35). Most of the plutons are Cretaceous in age, emplaced between 120 and 80 million years ago, although some few are older. One near Mono Lake, emplaced in Triassic time, is 210 million years old, and a few Jurassic plutons date from 175 to 155 million years ago. Researchers who have analyzed potassiumargon ratios of the many plutons that compose the batholith have suggested that magma invaded the Sierra in distinct pulses. Each pulse lasted from 10 to 15 million years and was separated from the following one by about 30 million years. Altogether, it took 130 million years to complete the creation of the granitic rock. The first plutons were emplaced (“intruded” is the geological word) on the western side of the mountains. Later ones were formed eastward across the batholith at a rate of about 1.7 mi (2.7 km) per million years. This difference in age is reflected in the overall chemistry of the granitic rocks: the ratio of potassium oxide to calcium oxide more than doubles from west to east. Similarly, the ratio of strontium to its decay product increases west to east, enabling scientists to locate the western edge of the North American continent when the batholith was formed. Figure 35 shows rocks that cooled in these pulses as they are now understood.All California plutons are not shown on this tiny map, not even crudely. The Southern California Batholith is missing, although it is surely related. Only a few of the plutons in Nevada and eastern California are shown, although they, too, are a part of the story. Nor are the Klamath Mountains shown, though they probably should be considered as an extension of the

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Reno

130–150 million years old

Lake Tahoe

39°

160–180 million years old 195–210 million years old

80

Cretaceous

100–120 million years old

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Jurassic

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Triassic

Sierran granitic rocks 80–90 million years old

Sacramento

Ne va d lifo a rni a

Ca

49

38° 120

Bishop 37° 395

36°

Pacific Ocean

121° Bakersfield

35°

N

120°

119°

118°

Figure 35. Groups of Sierran granitic rock that formed during several stages of cooling, as interpreted from the actual ages of granitic rocks.

Sierra Nevada, separated from the main mass by a volcanic cover. Whether the pulses of igneous activity are pulses in a rhythmic sense is not known. Perhaps they are periodic, as they appear. If so, one cycle of granitic emplacement should have taken place

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in the Tertiary Period, and another could be underway now. Because such an event would be taking place far beneath our feet, we do not have a way of knowing if the periodicity is real. Probably, as the plutons found their place, they were accompanied by volcanic eruptions above them and nearby. Much of the volcanic ash and other volcanic products have been eroded away, but here and there in the Sierra Nevada are pockets of volcanic material of the same age as the plutons. In the continental interior (the Rocky Mountains, for example) are large deposits of now-consolidated volcanic ash of this age that geologist King Huber has suggested may have been derived from these noweroded Sierran Cretaceous volcanoes.

Jointing and Sheeting Two characteristics of granitic rock that have been responsible for much of the spectacular scenery of the Sierra are jointing and sheeting, both expressions of the way in which rock breaks. “Joints” are more or less even planes along which the rock cracks — generally up and down, as well as in two horizontal directions.“Sheeting” describes the cracking of a rock along curved surfaces parallel to the surface of the rock. Jointing makes sharp, steep faces like those on the eastern side of Mount Whitney; sheeting provides the magnificent domes of Yosemite. Joints are regional features, cutting across many miles and through the entire batholith. They may be identified as a faint crisscross pattern on aerial photographs, or they may be obvious in individual outcrops, where they divide granitic rock into blocks like loaves (pl. 31). Such a heap of loaves is seen along State Hwy. 108, the Sonora Pass road, at Eagle Creek near Dardanelle. A very prominent joint has cut a conspicuous slot in the mountains on the High Sierra Trail near Hamilton Lakes. On State Hwys. 88 and 89, in Alpine County, and on U.S. Hwy. 395 north of Markleeville, the mountains have ribs of granitic rock, left after erosion along adjacent joints wore down the intervening rock. In wet weather, water courses down between the ribs, etching them more deeply. Throughout the Sierra, joints influence where streams run, noticeable especially in the Alabama Hills on the eastern side of the Sierra. The Sierra has two major sets of joints, one trending north-

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Plate 31. Jointing in granitic rock. Sierran granitic rock is jointed in three directions, roughly perpendicular to one another, that allow the rock to break into squarish blocks, giving an outcrop the look of a Mayan temple. When the jointed outcrop or the blocks are buried, as they have been in the recent geologic past by fragments of rock and soil torn from the mountains, they weather underground into rounded shapes, later to be uncovered by erosion.

west with the grain of the range, the other northeast at right angles to it. Here and there they change direction slightly, but they change together so as to maintain their nearly perpendicular relationship. Where the rocks are fine grained, joints are close together; where they are coarse grained, farther apart. They pass from one pluton to another almost without deflection. Although the overall pattern is a general crisscross, the individual joints are short, several miles being the greatest length of any single one. That this is the regional pattern indicates that it developed after the batholith crystallized, or it was impressed upon the batholith as it cooled. It does not seem to be a direct result of cooling (there are cooling fractures in small bodies of igneous rock), because the masses cooled at different times. On the other hand, the pattern developed before the extensive weathering period that followed, because the joints themselves are deeply weathered. Joints have influenced the development of many of Yosemite National Park’s most striking features. The slope of the back of the Three Brothers was determined by westward-trending joints; the treads of Staircase Falls follow eastward-trending inclined joints. Vertical joints have controlled the cutting of the face of Half Dome and the cliffs of Cathedral Peaks. Indeed, Half Dome

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Figure 36. The joint system here has produced a trench about 20 ft (6 m) wide, visible from the High Sierra Trail near Hamilton Lake. The trench is a strong landscape feature, visible also on the skyline above Upper Hamilton Lake.

is not half a dome at all (pl. 32). According to geologist King Huber, whose book The Geologic Story of Yosemite National Park is a “must read” for anyone visiting the park: 80 percent of the northwest “half ” of the original dome may well still be there. What probably happened is that frost splitting of the rock at the back of a tiny glacier against Half Dome above Mirror Lake gradually quarried back the steep northwest face. As the base of the cliff was hewn away, ultimately parts of the sheets parallel to the upper surface of Half Dome were left projecting outward as the crest of the vertical cliff. Sharp angular bends in the gross form of Yosemite Valley suggest that the entire valley, as well as Tenaya Valley, may have been eroded along a complex joint system now concealed on the valley floor. (1987, 33)

El Capitan (pl. 33), in contrast, is composed of El Capitan granite and Taft granite, both largely unjointed, so its face—beloved of rock climbers — is a sheer cliff.

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Plate 32. Half Dome from the side, showing exfoliating shells mirroring the topography of the dome. Granitic rocks crystallize at depth in the Earth under many feet of older rock. When the mountains are uplifted by Earth forces and the older rock is eroded away, the granite, now exposed, expands toward the Earth’s surface. In a monolith such as Half Dome, the stress from the expansion eventually exceeds the tensile strength of the rock, and the outer, more rapidly expanding layer bursts free. As this process is repeated, monoliths such as Half Dome become covered with layers of shells. The outer layers gradually disintegrate, allowing pieces to fall off. The cables that climbers use to ascend Half Dome more easily are visible near the center of the picture.

Sheeting, however, is a local phenomenon. It can be observed on an individual outcrop, on a single mountain, or on a particular dome, but there is no regional sheeting pattern. The sheets form parallel to the topography and, where they are nearly straight, may resemble joints. It is to this tendency of granitic rock to form sheets that Half Dome, Sugarloaf, Liberty Cap, Pywiack, Lembert, Fairview, Polly, and the many other Yosemite domes owe their remarkable shape. Some of them have also been glaciated, modifying their forms somewhat. Unlike the sharp, ragged peaks of jointed rock, such as those in the High Sierra near Mount Whitney, the curious domes of Yosemite are usually formed in less-jointed rock. They are the products of exfoliation, which is the “leafing away” of layers of

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Plate 33. El Capitan, one of the sheerest cliffs in the world, is composed of El Capitan and Taft granites, plutonic rocks with more silica than most other plutons in Yosemite Valley. Because quartz-rich rocks tend to have more closely spaced joints than less siliceous ones, they are more resistant and have more massive outcrops. Thus, El Capitan has a smaller talus heap at its foot than more highly jointed features.

granite, much as layers of onion peel away from one another (pl. 34). The original form probably was rectangular, or at least much more angular, but through gradual exfoliation the sharper edges have dropped away. Just why the rock should leaf away is somewhat of a mystery. Heating by the sun has been suggested as the principal cause. The sun heats and expands the rock, then, when it cools and contracts (in winter, freezes), a split begins. But this cannot be the whole story; if it were, the process should operate very rapidly in the desert, which has more sun and more heat, yet it does not seem to. Laboratory experiments that simulated nearly a thousand years of alternate heating and cooling had very little effect on granite. On the other hand, heating and cooling combined with simulated rain began to produce shells of exfoliation within 2.5 simulated years. The reason for this seems clear enough: feldspar minerals, when water is added, in time form clay, which not only crumbles away when dry but swells when wet, shouldering other minerals aside. It is certainly true that the rounded tops of exposed granite domes do not easily break into sheets, whereas the sides do. In contrast, domes or “corestones” buried in the ground

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Plate 34. Sheeting at Matthes Crest, Yosemite National Park. Unlike most jointing, sheeting—itself a form of jointing—follows the topographic surface. Here the sheeting is nearly vertical. This process is also called “exfoliation”—the “leafing away” of rock shells. Where the ground surface is nearly level, the sheets are nearly horizontal; where granite underlies a hill, the sheets are convex upward; if beneath a valley, the sheets are concave upward. Royal Arches, high on the canyon wall below North Dome across the valley from Half Dome, is a huge example of sheet jointing in the Half Dome Granodiorite.

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weather all around into shells. It is also true that feldspar crystals are longer in one direction than in the other two; this helps to orient the direction of peeling. But true circular weathering is hard to account for completely. Perhaps, as one geologist has suggested, the original orientation of minerals in the cooling magma has partly determined that rounded forms develop. Sierran granitic rock breaks into sheets in many places where it does not produce rounded domes. Sheeting of granite in Big Arroyo, High Sierra, gives the mountainside a peeling aspect; along Tioga Road near Yosemite Creek Campground in Yosemite, and at Tragedy Springs, on State Hwy. 88, sheets of granitic rock are stacked like bricks, as if a building had been intended and forgotten.

Where to See Granite It is not hard to see granitic rocks in the Sierra Nevada. Every major pass through the mountains exposes acres of gray granite as it cuts through the mountain core. Figure 37 shows the extent of these bodies in the Sierra, divided by age rather than rock type. Each major intrusive epoch produced granitic rocks of all sorts, so that you can see granite and its relatives that are as old as 210 million years, or as young as 80 million years, and all part of the great Sierra Nevada Batholith. A hike in the Huntington Lake area, east of Fresno, reveals several different varieties and colors of granitic rock: the lighter-colored quartz monzonite of Bald Mountain, the grayer granodiorite of Dinkey Creek, and the light gray quartz monzonite of Dinkey Dome, which here and there contains smoky quartz crystals. Granite is not as popular for building stone as it once was because newer architectural materials have been developed that are cheaper and safer. But the beauty of polished granite is enough to encourage some architects to use it, despite the cost. It is still shaped into monuments, although the use of monuments, too, is declining. At one time, several quarries in the Sierra Nevada supplied stone for cities throughout California. In San Francisco, the dark granitic rock with purplish quartz and orange feldspar in the Hibernia Bank building came from Rocklin; the Bank of California, on Sansome and California Streets, the St. Francis Hotel,

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Mt. Emerson

Mt. Humphreys

Light gray granite

Old sediments

Darkest, oldest granite Lightest, youngest granite

Old volcanics

Figure 37. Bodies of Sierra granite west of Bishop. In the light of the morning sun, different plutons can be distinguished by their shades of gray.

the Dewey Monument in Union Square, the Old Custom House on Battery Street, and the Post Office on Seventh and Mission Streets are of stone from the Raymond quarries. In Sacramento, the Capitol building has two types of commercial granite: the base is of Penryn granite, and the upper part is 130-million-yearold Rocklin granite. The Sacramento City Hall has steps of Rocklin rock, as does the Cathedral of the Blessed Sacrament. The U.S. Post Office has Rocklin granite walls. In Los Angeles, the Fountain Mall in Civic Center features one large piece of Raymond granite. Although much granite in Los Angeles came from quarries in the Peninsular and Transverse Ranges, the Federal Reserve Bank contains Sierran granite. Most granite quarries are on the western side of the Sierra, partly because it is closer to large city markets, and partly because the masses of granitic rock on the western side are less jointed text continues on page 207

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FOOTSTEPS IN THE SKY The Pacific Crest and John Muir Trails through the Sierra Nevada

he Pacific Crest National Scenic Trail snakes its way 2,638 mi (4,245 km) (officially) from Mexico to Canada, through three states, 24 national forests, seven national parks, 33 wildernesses, five state parks, one national monument, one national recreation area, and county and private land. It is the second oldest long trail in the Scenic Trail system of the United States (the Appalachian Trail is older). In the Sierra Nevada (fig. 38), the highest and most spectacular portion of the Pacific Crest Trail follows the slightly older John Muir Trail, which runs from the crest of Mount Whitney to Happy Isles in Yosemite Valley. The 212-mi-long (341-km-long) John Muir Trail leads hikers along what many consider the finest high-mountain landscape in the “lower 48” (pl. 35).This is the High Sierra, a land of soaring 13,000- and 14,000-ft (4,000- and 4,300-m) peaks of mountain fastness, of glacier-created lakes by the thousands—so many that some are not even named—of canyons, some a mile deep.Although much snow falls on it in winter, summers are mild and pleasant, with only sporadic rains and glorious mountain sunshine, making the time you can walk the trail idyllic.About half the trail lies in Sequoia and Kings Canyon National Parks, a small fragment in Devils Postpile National Monument, some in the John Muir Wilderness, some in the Ansel Adams Wilderness, some in Yosemite National Park, and the rest in national forest land. The John Muir Trail runs through many granitic plutons and shows off clearly the granitic heart of the Sierra Nevada. From the summit of Mount Whitney, you can see much of the Sierra Nevada and, on a clear day, far into Nevada.You are standing on the bull’s-eye of the 84-million-yearold Whitney Intrusive Suite, a mass occupying some 460 sq mi (1,192 sq km). It is a nested sequence of granitic rock, which was molten in the Cretaceous Period.The outer portion of the molten rock began to solidify first, while the inner portions remained fluid. Because the Whitney suite is one of the larger granitic bodies in the Sierra Nevada, it took longer to cool than smaller ones.As a result, the center of the mass was able to cool slowly into very large crystals, some as much as 2.5 in. (6.4 cm)

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Facing Page: Figure 38. The Sierra Nevada portion of the Pacific Crest National Scenic Trail. The trail is one of the nation’s Long Trails, officially registered as 2,638 mi (4,245.3 km), extending from Canada to Mexico. The Sierra Nevada portion includes its most scenic parts, especially the High Sierra along the John Muir Trail.

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Susanville Quincy

SI

ER RA

Reno Truckee Lake Tahoe

Bridgeport Lee Vining

Yosemite Valley

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long. Clarence King, on his wild Sierran hike, found the crystals useful as handholds, but uncomfortable to sleep on. For 25 mi (40 km) you are in the Whitney Suite, with its stunning rocks.The trail leads you within 400 ft (120 m) of the summit of Mount Muir. Near Forester Pass, you hike through a more complex geologic area containing not only plutons, but also the Oak Creek roof pendant, which contains Jurassic metamorphic rocks largely of volcanic origin, and a swarm of dark-colored dikes called the Independence Dike Swarm.The ParPlate 35. Route of John Muir’s adise Granodiorite pluton (86 milclimb up Mount Whitney. lion years old) is the next major granitic body you pass. It has smaller crystals (phenocrysts) than the Whitney series and is darker in color. For the next 180 mi (290 km), you pass through a great many plutons. Just beyond Mather Pass, about 60 mi (97 km) from Mount Whitney, you hike close to the Palisade glacier, California’s largest.About 90 mi (148 km) from the Whitney crest, you encounter the light-colored granite (yes, true granite!) of the Evolution Basin pluton. It is dazzlingly white and about 80 million years old. Soon you will enter Evolution Basin, with its host of glacial lakes and its vivid meadows. Here the land is scoured as if the ice left it just yesterday.The high peaks around are named for nineteenth-century giants in the new science of evolution: Wallace, Darwin, Haeckel, and Huxley. At Reds Meadow, about 150 mi (241 km) from Whitney, you see the Devils Postpile, a columnar basalt flow.Also near here, the trail is underlain with pumice, whereas above are cliffs of volcanic rock, all derived from the same volcanic episodes. Another 36 mi (58 km) brings you to Tuolumne Meadows, in Yosemite National Park. Many people stop their hike here, where there is food and lodging, but some die-hards continue to where the trail ends near the stream gauging station at Happy Isles in Yosemite Valley.They are rewarded with splendid views.

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than those on the east. The domes of Yosemite, for example, have held together through time far better than the more jointed granite in the vertical gothic rock spires on the eastern side. Partly because of the way the granite on the eastern side breaks, and partly because that side is not so well clad with trees as the western side, it is an excellent place to see many different types of granitic rocks. Geologist Paul Bateman, who has worked many years in the high country west of Bishop, has suggested that from the outskirts of that town under the morning sun you can see several different bodies of granite in one view. Afternoon shadows obscure the distinction between the light gray granite of Mount Tom, the still lighter, younger granite in Mount Emerson, and the older, darker granite to the south. Or, walking up the trail from Glacier Lodge west of Big Pine to Palisade glacier, you can

Plate 36. The Lyell Fork of Merced River turns into falls over sheet granite in Yosemite National Park.

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Plate 37. The movie location for Thug Temple in Gunga Din in the Alabama Hills.

see along the trail granitic rock of all sorts and colors. At the end of the trail is a view not only of granite, but also of the largest of California’s remaining glaciers. Quite a different aspect is presented by the granite of the Alabama Hills, at the foot of the Sierra near Lone Pine. Reputed to be the oldest rocks in California (quite untrue), they have a tangled, gnarled look, as if they were weary of what they have endured. They are rounded and deeply weathered; it is easy to see how they gained their undeserved reputation for great age. A careful look at the Alabama Hills reveals that these rocks, too, are jointed and faulted. Yet their aspect is quite different from the faulted, jointed granite of the Whitney area above them. In both regions, the granite is about the same age: 80 million years. What could account for the difference in appearance? Climate? Surely the desert climate shapes a far different character than the high, cold mountains. What difference does the elevation make? And what else might change them? What has been their story through the ages? These are questions we are all free to speculate upon, and then we can test our speculations as best we can. Perched against the backdrop of the highest part of the alpine Sierra, the Alabama Hills are a lure to photographers. In fact, so

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many “westerns” were made on location in the Alabama Hills that there is now a scenic drive marked through the hills (pl. 37). Moviegoers may recognize Movie Flat, a ranch that has seen many a shootout, as well as the rocks, the road, and the mountains. The large native Indian population in the eastern Sierra often acted in these dramas. The Alabama Hills derive their name from the Confederate battleship Alabama, which for a time during the Civil War successfully attacked Union shipping. Pro-South sympathizers named their mining claims after the Alabama, and the name stuck with the hills. The Union’s U.S.S. Kearsarge sank the Alabama in a gun battle in the Atlantic Ocean in 1864. Joyous Northern supporters named a Sierran mining district, a peak, a mountain pass, and a town “Kearsarge.”

Granite Makes Grandeur The granite that we see now — the granite that is the grandeur of the Sierra Nevada— was not granite but liquid rock until it cooled deep underground, slowly, through the ages. And even after it cooled, it was not until the mountains were pushed upward and millions of years of erosion stripped away the granite’s rock cover that it became possible for us to see it as we do, to climb on it, to walk on it, to admire it. It is granitic rock as a whole that determines the shape of the mountains. It is the response of granite— the whole family of granites — to the ravages of weather, to glaciers, to streams that come down the mountains, that has given us the splendor of today’s Sierra Nevada.

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Overleaf: Waterfall in Lundy Canyon, dressed in fall foliage. Metamorphic rocks in the Sierra commonly have joints that tend to break into small blocks, so that their waterfalls do not plunge over massive cliffs (see pl. 71), but instead tend to run downhill like stair steps. Where departing glaciers have left steep cliffs in metamorphic rocks, waterfalls may plunge steeply, but this is rarely the case. Metamorphic rocks may not host steep waterfalls, but they do host many sought-after minerals, such as garnet and tungsten.

mountains are many treasures valued by humans, among them that breaker of saints and changer of history: gold. Compared with the rocks of the Earth, deposits of precious metals are very scarce. They are oddities of nature, and only human fascination with them has transformed them into treasure. More to be treasured is the water the range’s very existence pulls from the sky to make the western Sierra a well-watered breadbasket, leaving the land to the east thirsty. Gold is in the sea as well as in most rocks. In igneous rocks, the amount of gold averages about five ten-millionths of one percent (.0000005 percent). Until the last quarter of the twentieth century, most gold mines of economic value — that is, those that repaid the cost of mining— were in areas where nature had concentrated the precious metal to 20,000 times that much, yet the ore contained only one-third of an ounce of gold per ton of rock. Even then, when the cost of mining was very high compared to the price of gold, huge floating dredges, similar to those so common on California rivers until the middle of the twentieth century, could make a profit mining ore that contained only five cents’ worth of gold per cubic yard of gravel. This is a concentration of about one eight-hundredth of an ounce per yard, or about one part in 32 million. As the first edition of this book was going to press, the picture was changing. The rocks are the same, the gold is the same, the concentration is the same, but new techniques of mining and milling coupled with a meteoric rise in the price of gold transformed the picture. Because gold is so rare, and because gold is found almost everywhere in some amount, the idea has grown that “gold is where you find it.”Indeed it is; but gold in commercial quantities, like most other metals, is by no means evenly scattered throughout the Earth. Gold concentrated by nature in quantities large enough to mine is found in favored regions, generally in mountains (pl. 38). Many modern gold mines win gold that is truly invisible; ore miners call it “no-see-um gold.” Even the electron microscope cannot see some of the gold, as the particles are smaller than .1 micrometer, which is less than four one-hundred-thousandths of an inch. So, in a way, gold is indeed everywhere. The Sierra Nevada is one of those favored regions where an amazing amount of gold has been won from a small area. Some of text continues on page 216

HIDDEN WITHIN THE

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GOLD: THE CALIFORNIA STATE MINERAL

n April 23, 1965, Governor Edmund G. “Pat” Brown signed legislation designating gold as the California state mineral. Most people, if asked, would have said, “Of course, California is the Golden State.” It was gold that propelled California from a new acquisition, gotten from Mexico through war and purchase, straight into statehood, without waiting in the wings as a “territory.” It was California gold, some claim, that won the Civil War. It certainly was California gold that fueled the American Dream. People in 1848, the first year of the gold rush, picked gold from rock with pocketknives, but that gold did not last long enough for more than a handful of the hordes that poured in during 1849 to get rich. Never mind; California continued to be seen as the land of unparalleled opportunity where anyone, no matter his or her education, wealth, or station in life, could, with luck, gain wealth, and gold was its touchstone. Why gold? Through the ages, gold has exerted an attraction far beyond its natural place in Earth’s scheme. It is soft (hardness 2.5 to 3), has no cleavage, has a boiling point of 5,576 degrees F (3,080 degrees C), a melting point of 1,948 degrees F (1,064 degrees C), and an atomic number of 79. It has an atomic weight of 196.8665, making it very heavy compared to other elements. It is rarely found in crystals. One of its most important properties is its reluctance to form chemical compounds, so that gold remains gold, untarnished by “rusting” (oxidation) or corrosion. It is mixed with other metals to form alloys, but it is not changed chemically by alloying. It has many industrial uses, dependent upon its insistence upon retaining its own identity or upon its ability to carry electrical current. Automobile air bags, for example, use gold-coated electrical contacts, as do computers and much electronic and space equipment. Because gold has extraordinary reflective properties, it is used to deflect and confuse the signals of heat-seeking missiles, which is why the U.S. President’s plane is protected with gold coating. For over a century, gold has been the metal of choice for dentists, particularly for bridges and inlays. It is nontoxic, can be easily shaped, and is tough; it does not wear easily, or corrode, or tarnish. American dentists use about 13 tons a year.

O

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Because gold remains gold, except for forming a few chemical compounds with tellurium, California miners have been lucky enough to find many gold nuggets. The 25 largest gold masses found in the United States came from California, led by the Carson Hill gold mass (not a true nugget), found in the Sierra Nevada’s Carson Hill lode mine in 1854 and weighing 2,340 troy ounces. The largest gold placer nugget, stream worn, was the McClellan, found at Mokelumne Hill in 1852 and weighing 1,200 troy ounces. In the frenzy of 1848 and early 1849, many large nuggets may have been sent to the melting pot without leaving a record. For centuries, gold was the principal medium of exchange—the form of money recognized the world over. Many gold coins are being minted today, but few of them are used for money; most are collector’s items. The world is no longer on the gold standard, and much of the gold the United States had kept as gold bars in Ft. Knox, Kentucky, and several other national depositories has been sold or mortgaged, although it may still be stored there. Because we humans admire its yellow color and metallic sheen, for millennia gold has been fashioned into gold jewelry—from time before Ancient Egypt to last week. Indeed, since gold does not lose its identity, it can be refashioned over and over again, so that the gold in your wedding ring may once have graced Queen Hatshepsut, or been formed into a tiny baby llama in the “Golden Enclosure” by inspired artists of the Incan empire in Peru. Because gold is malleable, a cupful can be hammered into a sheet large enough to cover an entire football field. Most gold domes are hammered sheet gold.The California State Capitol building, however, has a golden dome made of brushed gold plating, created with an electrified paintbrush. California’s gold is not gone.When the price of gold rose to about $850 per troy ounce in 1980, and new recovery techniques made even invisible gold minable, old gold mines, some believed long dead, were opened up and new ones searched for; the whole gold mining industry took a new lease on life.The price did not stay at that high level for long, though, and only the future will tell what is in store for California’s gold.

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Plate 38. Gold in a quartz vein.

it was in enormously rich zones called “bonanzas.” For example, one single lump of gold taken from the Carson Hill mine near Melones in 1854 weighed 2,340 troy ounces (160 pounds avoirdupois) and was then worth nearly $44,000!

Hydrothermal Deposits If deeply penetrating groundwater meets a source of heat in the ground, such as might be provided by hot, fluid rock (magma), the process of ore formation is immensely speeded up; in fact, many ore deposits the world over are classed as “hydrothermal” deposits because they resulted from the action of hot water, and much of the world’s gold is ultimately hydrothermal, that is, precipitated from hot water. But the problem remains: how did gold get into the hydrothermal fluid in the first place? No one knows for certain, but some geologists who have studied this problem think the story goes like this: Gold is carried upward from the depths of the Earth, probably from the Earth’s mantle, as magma, then as part of the lava that pours out along the midocean rifts. As the lava cools, it cracks, and seawater moves downward through the crack network. The seawater is heated by the hot but cooling lava and reacts chemically with it. Chlorine from the salt of the sea (common salt is sodium chloride) aids in dissolving the metals. The hot, metalenriched seawater rises toward the seafloor, where cooling causes the metals to be precipitated (separated out of solution as a solid).

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Metals are concentrated at and below the seafloor in this way, making metal sulfides such as pyrite (iron sulfide), and forming metal-rich chimneys, mounds, and sediments, with gold ions hitchhiking within the lattices (molecular structures) of sulfide minerals. This seawater hydrothermal process keeps working on the minerals, concentrating them until the new ocean crust is cool. The minerals may become part of a plate that is subducted, going back into the mantle (as in the Ring of Fire), where the valuable metals may enter the new magmas and rise back toward the surface again, contributing metals to the new hydrothermal systems that develop in and near the subduction-related volcanism. In 1983, researchers aboard Angus, a tiny undersea research vessel, discovered fields of hot springs in the sea, most of them inactive. Then the baby submarine Alvin’s crew found a live hot spring near the Gulf of California. “Black smoke” was shooting out of hydrothermal vents. The vents were built up from chemicals recycled by the hydrothermal waters, as hot springs on land have mineral “collars” like those at Yellowstone National Park. The center of the vent was open, like a volcanic neck, and allowed the black smoke to pour out, back into the sea. The black smoke forms when the mineral-rich water is thrown out of the mouth of the vent and quickly mixes with cold seawater. The “smoke” is iron sulfide, precipitated out of solution. Much of the smoke is wafted away by the sea, but some falls back to the bottom as a metal-rich sediment. It, too, cracks and is penetrated by seawater, and hydrothermal action begins on the metal-rich sediment. Since the 1980s, many metal deposits formed by black smokers have been found along spreading seafloor volcanic ridges. Two of the deposits seen so far are especially rich in gold. One on the Mid-Atlantic Ridge is 1,900 ft (580 m) in diameter and 165 ft (50 m) high. Its large size suggests that it has been venting goldrich black smoke for a long time.

Where Mines Are But even though the black smokers in the sea throw it out, no one mines gold on the seafloor. Mines are in terrestrial mountain

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belts, such as the Sierra Nevada, within or along the margins of continents. This is where plates have collided or subducted, and where the mineral-rich rock from old central vents has been incorporated into one plate, then crashed into another. It is here that mountains are lifted up, that earthquakes take place, and new volcanoes erupt. Here again, the great pressure of large, moving plates, interacting at plate boundaries, brings with it high temperatures. Where plates are subducted, rock is melted as one of the plates plunges beneath the other and mixes with continental rock, once again changing its chemistry. Metals formed at the midocean vents and concentrated during their journey are further concentrated here. Volcanoes form, and beneath them, large bodies of granitic rock gradually solidify. This remelted hot rock once again cracks, and water enters and is heated and again reworks the metals within the rock. This time, the water is from the land — meteoric water, derived from rain and snow, sometimes mixed within the Earth with “magmatic water”—sweated out of solidifying magmas, and the process of making ore for gold lodes has begun.

Where Was California? Where was California when all this sliding and diving and docking and making of gold ore was going on? For many millions of years, California was not there at all. Certainly the latitude and longitude that California now occupies existed, but there was no fragment of the land we call California — only the deep blue sea. By 240 million years ago, North America had grown and was joined to South America and Africa, with what would be Eurasia looming to the north. Until about 160 million years ago, sediments accumulated as a wedge along the western side of North America, in a basin that included most of California’s gold country but is now bent, twisted, and faulted. Within these faulted and twisted beds is a group of rocks called by geologists the Smartville complex, or, in plate tectonics parlance, the Smartville block. (The name comes from the tiny town of Smartville, which is west of Grass Valley and east of Marysville. Former President Herbert Hoover helped make the first geologic map of the Smartville area, called “Smartsville”

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then.) The belt is as much as 25 mi (40 km) wide and lies below the high Sierra Nevada from about Auburn to Oroville, and westward beneath the Central Valley.

The Smartville Block Brings Gold The block came from the ocean depths, moved to an island arc, then found its way to future California, bringing gold with it. Off the California shore were two ocean trenches (subduction zones), one dipping eastward, the other westward. Both were destroyed by the arrival of the Smartville block. Either the trenches were stuffed so full of rock already subducted that part of the Smartville (the part we can see today) rode right over the trenches instead of diving into them, or, in the process of diving into one of the subduction zones, a piece of the Smartville was shaved off and left resting on the new continental edge. Whichever is correct, the Smartville is a piece of ocean crust, a very surprising batch of rocks to find in today’s Sierra Nevada. With the Smartville came California’s gold. To see a map of the Smartville “suture,” (the line along which the Smartville block was joined to the American continent), you need only look at a map of the Mother Lode, because the docking of the Smartville created the Mother Lode.

Granite Forms Another portion of the mountain building— aside from the deformational part—was the emplacement of granite bodies. The forces that controlled the building of the Sierra twisted and bent the layers of ancient Paleozoic and Mesozoic rocks several times, indicating that there were several episodes of mountain creation before the present Sierra took form. During this mountain making, particularly during the later episodes in the Jurassic Period (about 140 million years ago), the way was prepared for gold ore to form, for then the Mother Lode fault zone and many of the numerous related faults were born. These great tears in the Earth must have been the source of many earthquakes a hundred mil-

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lion years ago. Cardinal to the making of mountains, the faults opened avenues along which mineralizing solutions could rise from the depths. Today, the old faults are healed by quartz and other minerals, including gold and silver; it is very doubtful, but not impossible, that they will again be earthquake faults in our lifetime. The gold and silver, as well as many of the other ores, were formed by the grace of granite. For it was during the cooling of the granite magma that hot waters and gases steamed upward, penetrating the rock through joints and fractures, leaving behind telltale evidence of their passage. Nowhere was the evidence more apparent than near the fault breaks, where the mineralizing solutions left veins and vugs (holes) filled with ore-bearing minerals, as well as metal shot through the rock on either side. The orebearing solutions were not particular as to what sort of rock they left gold deposits within; nearly all of the old metamorphic rock types contain gold deposits somewhere in Sierran gold country, but much of the gold is in and near quartz. It is not true that all gold is bound in quartz, or that all quartz veins contain gold. Several generations of Sierran quartz mark different episodes of solution escape, but the gold-bearing quartz was usually the last to form. Where the veins turned, or where they split or swelled, proved to be places where gold accumulated. Experienced miners in the Alleghany district of Sierra County claimed that they could tell “live” quartz that might contain gold from “dead” quartz that never did, by its color: live quartz was milkier, less lustrous. Perhaps, indeed, they could; Henry Ferguson, a geologist who studied the veins in the 1930s, thought so. Although the microscope showed him that the live quartz was microscopically broken, he himself never gained enough experience to separate live from dead in the mine. What’s more, the miners, even though they could recognize live quartz that might contain gold, could not tell if it actually did or not. They could only separate out the kind that definitely had no gold— the dead quartz. In some places in the gold country the quartz veins have openings in which quartz crystals have grown large enough to warrant mining for use in radio equipment. We can understand quartz crystals growing large and splendid where there is room for them. But how were the strong rocks pushed aside enough for quartz crystals to grow into veins? Surely deep within the Earth

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there are no real openings, merely planes of weakness. It does not seem likely that quartz, solidifying from a hot solution, could exert enough strength to force the host rocks apart as far as the width of the vein. Neither does it seem likely that the solutions had wide avenues through which to rush unimpeded. Rather, they must have moved in molecule by molecule, in places shoving aside an earlier molecule, in other places filling a minute void. Although it is true that faults served to determine where ore deposits would be, there are areas in the gold country, particularly in the region of the northern mines, where the main fault zone is masked by a belt of serpentine and related rocks. Such rocks—the peridotite group as shown in table 3—may have come from deeper within the Earth, through plate movement, instead of separating out from magma that eventually formed granite.

Winning the Gold Plate tectonics has given geologists new ideas about where to look for gold, but whether gold is there in minable quantities still depends upon the price of gold and on the cost of procuring it. New mining and milling methods have lowered the costs of winning gold. “Heap leaching” is a newish process that obtains gold from crushed ore by pouring a solution of cyanide over heaps of ore. Environmentalists have forced miners to control the heap leaching process (fig. 39) carefully to keep the deadly cyanide from destroying wildlife, polluting rivers and groundwater, and endangering human lives and health. Heap leaching reduces the cost of mining, but it is the price of gold and the political climate that allows mines to work. Until the late 1970s, the formerly exciting Sierran gold country was a picturesque ghost. Except for recreational miners, almost no gold miners were at work. Rusting headframes, piles of rock, and abandoned machinery were poignant reminders of days gone by, days that few thought would come again. Since 1933, the price of gold mined in the United States — regardless of the cost of mining— was set by the federal government at $35 an ounce, and gold miners were required to sell their gold to government-authorized buyers. Then, in 1971, President Richard Nixon raised the price first to $38 an ounce, then 14

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Spray irrigation of cyanide solution

Add cyanide and adjust pH Collect gold-bearing solution

Ore

Gold recovery Pumps

Impermeable base (clay) Pregnant with drainage blanket (gravel) on top pond

Barren pond

Carbon-filled columns

Figure 39. How heap leaching works. Ore is placed on an impervious pad, which may be clay or some other impermeable material. A dilute solution of sodium cyanide is spread over the heap, often by sprinklers. The solution trickles through the ore, dissolving the gold and silver. The pregnant solution containing the precious metals drains from the heap and goes to a large, plastic-lined pond. From there it is pumped through tanks containing activated charcoal, which adsorbs the gold and silver on its surface. The gold-bearing charcoal is chemically stripped of its gold and silver and the strip solution treated in an electrowinning cell, where the gold and silver is plated by electrolysis on steel wool. The wool, in turn, is melted in a furnace, and a doré bar (a bar of mixed gold and silver) produced. It, in turn, is smelted, resulting a bar of nearly pure gold. The barren cyanide solution, from which he gold has been taken, is pumped back to a holding basin for reuse.

months later to $42.22. In 1974, President Gerald Ford lifted restrictions on gold, allowing U.S. citizens to sell it as they wished. The price rose rapidly, reaching a high of $850 in 1980. Such a price for gold stirred many miners and would-be miners into action. In California, many near-derelict mines sprang to new life. The Carson Hill mine in the Mother Lode opened again. The old Harvard mine right on the gleaming white quartz Mother Lode vein and five others operated by the same company leapt into action to mine the two million ounces of gold left in the ground in mines that many people thought were mined out and abandoned. These were underground mines; so was the Sixteen-to-One in the Alleghany district, which soon was producing not just gold ore, but a spectacular crystalline type called “specimen ore.” Open-pit mines, where mining is done by huge machines digging pits in the hillsides, were the most profitable but ran into

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serious opposition from residents, who did not want the noise and dust and caravans of heavy trucks in their neighborhoods. By the end of the 1990s, the price of gold had dropped to $280, and many of the resurging mines closed down again.

Prowling the Old Mines The number of deserted mines, shafts, and prospects pits in the Sierra is uncounted. Throughout the mountains you may find open holes, caving tunnels, and ruined headframes. Although by law these should be fenced or boarded, not all are. Exploring old mines is extremely dangerous. You cannot be sure that the interior is not caved, that the air is not poisonous, that there are no internal shafts (“winzes”) to fall into, or, for that matter, how much the workings may wander and branch. Even if you are reasonably certain that the workings are safe, you should never venture in without wearing a hard safety hat and carrying a light, and without leaving word as to where you have gone. In the gold country, although most of the thousands of miles of underground burrows are no longer available to us, some of the surface workings are interesting in themselves. One of the most unusual is the Kennedy gold mine, near Jackson, which has been preserved as a park. For many years, the Kennedy held the title of the deepest mine in North America (the recently closed Homestake, in South Dakota, was eventually dug deeper). Its workings explored the Earth more than a mile vertically below the surface, along a 150-mi (240-km) network. Gold in the Kennedy was contained in a quartz vein emplaced along a fault. The vein is visible in places on the surface along California Hwy. 49 but is unobtrusive and hard to find. As it dips eastward into the ground, it becomes more interesting, for from this branching, lensing quartz vein and its extensions, flanked by slate and greenstone, Kennedy miners have in the past taken nearly $60 million dollars in gold, worth many times that at today’s fluctuating prices. Underground, the workings connect with those of the Argonaut, whose headframe stood on the hill to the west. It, too, is a mile-deep mine, with 8 mi (13 km) of drifts (passageways parallel to veins) and tunnels, 4 mi (6.5 km) of raises, and 50 mi (80 km) of stope floors (steplike excavations). In

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Figure 40. The Argonaut mine and mill. This view of the Amador County gold mine, in about 1920, looks west.

1922, the Argonaut caught fire, killing 47 miners — a whole shift— while the nation waited and worried (fig. 40). The mine produced about $25 million worth of gold (when gold was $20.67 an ounce) before being shut down, like the Kennedy, in 1942. Part of the surface equipment of the Kennedy mine consisted of an unusual system of wooden wheels used to carry the waste rock—called “tailing”—from the mill (where ore was crushed and gold separated) near the mine entrance to the dump. The wheels are now picturesque ruins to be seen south of the mine along Jackson Gate Road (pl. 39). From a hill to the north of the road, you can see two of the pine wheels, and beyond, the headframe and remaining buildings of the Kennedy. On the hill to the south are the two remaining wheels —one of them reconstructed — and over the hill are the old tailing dumps. The wheels, when working, carried the tailing in the manner shown in fig. 41. Wet tailing from the mill, lifted to the top of the mill building, was pushed into a trough, or “flume,” down which it flowed toward the first wheel, where it was dropped into a well at the bottom of the wheel. The first wheel, like the other three, was equipped with 176 little redwood wells, or buckets, along its perimeter. Each bucket picked up its share of

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Plate 39. Kennedy tailing wheel along Jackson Gate Road.

wet tailing, and as the wheel was rotated by the electric motor and belt drive that powered it, the tailing was lifted to the top of the circle. There it was dumped into another flume, angled slightly downhill toward the bottom of the second, higher wheel. From there, it was again lifted to the top, where it was dumped to slide down toward the third, and similarly, to the fourth, highest wheel. Each wheel was 68 ft (20.7 m) in diameter, and lifted the

Figure 41. How waste from the Kennedy mine and mill was lifted uphill by means of the “Kennedy Wheels” to the tailing dump. Wet waste pushed into the chute from the mill at right slid downhill to the bottom of the first wheel, where buckets built into the perimeter of the wheel lifted it to the top. From there, it slid downhill to the second wheel, where it was again lifted. Each time, one of the four wheels lifted it in elevation until it was finally high enough to pour over a hill into the tailing dump (left). Not to scale.

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waste 48 ft (14.6 m) vertically. Of course, each wheel actually lifted it 68 ft (21 m), but because part of the elevation gained by the preceding wheel was lost in dumping the waste in the well, and part was lost in scooting it down the flume to the next wheel, the total amount gained was 48 ft. From the top of the fourth wheel, the ground-up rock slid down a series of long flumes to a dump, where it grew into a flat-topped, artificial hill. When the wheels were in operation, they were housed in sheet-metal buildings. The buildings are no longer there, and only the crumbling relics remain. The purpose of this complicated enterprise was to protect the environment. In order to keep the tailing from entering the local water supply, this unusual artifice was developed. It is ironic that the tailing heaps have been turned today into dams for water supply! The entire vista is far more pastoral than it was three-quarters of a century ago. Then, the 100 heavy stamps of the Kennedy mill, used for crushing the ore small enough to recover the gold, added to the 60 at the Argonaut, must have roared in a way no freeway yet in the Sierra can equal.

Hard Rock Mines In 1850 George McKnight stubbed his toe against a rock outcrop while chasing his cows near Grass Valley and broke off a piece of quartz glittering with gold. The gold McKnight found was not placer gold, as the miners had been used to, but was in veins in hard rock, and to get it out involved breaking up the rock. Because McKnight’s vein, and as it proved, many others, contained principally the mineral quartz—the same mineral that makes up most of the sand of our beaches — with gold held tightly inside the quartz, mining these veins came to be known as “quartz mining.”“Hard rock mining” and “lode mining” are other names for it. The Kennedy, the Argonaut, the Harvard, and the Carson Hill were found later, and all are hard rock mines. Early miners were not hoping to find the so-called Mother Lode; that term did not come into vogue until the 1860s. They were looking for the Great Blue Lead. “Lead” (rhymes with “need”) was the miner’s word for what geologists and professional miners call “lode.” It is synonymous with “vein,” although

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geologists recognize veins, meaning mineral-filled fissures, that may not contain ore. Veins are thin sheets, not tubes like blood vessels, and they may extend vertically into the Earth or at any angle from the horizontal.

The Grass Valley Mines McKnight’s discovery catapulted Grass Valley into becoming one of the richest and most famous of California’s mining districts. Not only was it the first of the state’s lode-mining districts to be worked, but when its mines ceased operating in the 1950s, it held title as the nation’s longest lived, at nearly 106 years of continuous operation. Gold was so plentiful at first in Grass Valley that claims were limited to 100 sq ft (9.3 sq m), for fear the price of gold would drop too rapidly. Grass Valley is in the Sierra Nevada gold belt. Although the entire belt is often called the Mother Lode, this term, according to many miners and historians, should be used only for the 120-milong (193-km-long) strip in the central part from El Dorado to Mariposa. The Grass Valley mines would lie in the Northern Mines portion. The veins of much of the Mother Lode proved rich, with gold concentrated in astounding quantities. The richest segment of the Mother Lode belt has been the 10-mi-long (16-km-long) portion between Plymouth and Jackson, in Amador County, including the Kennedy and the Argonaut. The entire Sierran gold belt extends from Plumas County, where it is nearly 70 mi (113 km) wide, southward to Tulare County, where it nearly dies out, but it reappears again briefly in Kern County. These old rocks and the veins in them are the principal sources of gold. In Grass Valley, two sets of veins cut the rocks, one set that dips gently eastward or westward from the surface outcrop into the Earth, another that dips steeply. The gently dipping veins are in granitic rock; the steeper ones are in rocks related to granite but that contain more iron and magnesium than ordinary granite. Ore was found not only in the veins but also in adjacent rocks. Most veins in the Grass Valley area were from 1 to 10 ft (.3 to 3 m) thick and filled small fault zones. The zones are cut by many

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small fractures, which have served as avenues for ore-bearing fluids and boundaries for the ore bodies. The profitable zones within the veins, the ore “shoots,” vary in size and shape. Some veins in Grass Valley have been mined to an inclined depth of 11,000 ft (3,353 m). Although miners uncovered numerous rich pockets, the average grade of ore was from one-quarter to onehalf ounce of gold per ton. Besides gold, the ore contained considerable pyrite (iron sulfide) and some galena (lead sulfide), as well as small amounts of copper- and zinc-containing minerals. If one vein can be followed for 11,000 ft (3,350 m), and there are literally hundreds of veins and mines in the Sierra Nevada gold country, imagine how thoroughly honeycombed the foothills are underground. It is not easy to count the mines, as they frequently change names and ownership, or are combined with other mines. Underground, too, they run into one another. Through the years, Grass Valley became the world leader in gold-mining know-how. Among those who learned their trade in the Grass Valley mines was President Herbert Hoover, who shoveled ore at three of the mines just after graduating from Leland Stanford Jr. University. Hoover, a geology major, was in the first Stanford graduating class. His wife, Lou Henry Hoover, was the first woman geology graduate in the world.

Cornishmen Arrive Early on, expert help was brought in from overseas. It is said that John Charles Frémont suggested the plan: use miners from Cornwall, England, who knew about deep mining from working in the Cornwall tin mines. It proved to be just what the mines needed, and just what the Cornishmen wanted. They brought with them a store of mining know-how, as well as their tasty Cornish pasties (a turnover perfect for miners’ lunches), tales of friendly mine ghosts called Tommy-Knockers, and a love of music. Cornishmen also brought with them one of the most unusual pieces of mining equipment ever devised: the Cornish pump. Many of the Grass Valley mines had Cornish pumps, including the North Star and Empire. Their purpose was to take groundwater out of the mine. An operable Cornish pump is on display at the North Star Mining Museum at the North Star mine.

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Elisabeth L. Egenhoff, in her article “The Cornish Pump”

(1967, 59), describes the machine in these words: The Cornish pump was ponderous, creaky, exasperating, and cantankerous, but essential in its day for keeping water from flooding the mines. It filled a niche somewhere between bailing with buckets and electrical pumps. It was, in actual fact, not a single pump at all, but a series of pumps strung along a shaft at intervals of 200 feet or thereabout. Each pump raised water from its own level to a cistern at the next higher pump’s level, thus eventually raising the water to the surface, or to a drainage tunnel through which it could be led from the mine. All of the pumps worked from a single pumprod, which must indeed have been a marvel to behold: huge timbers as much as 60 feet long and 14 by 14 inches in section, bolted together to make a rod perhaps half a mile in length, following the shaft through all its changes of direction and pitch, and weighing in the neighborhood of 135,000 pounds. All this clumsy mechanism was pulled up perhaps six feet, and dropped down the same distance [by gravity] every 15 seconds. It was powered by a steam engine, or by water wheels and a series of gears; at least one we know of worked thus, day and night, for some 40 years.

In 1880, Cornish pumps were installed at 15 deep mines of the Sierra Nevada. Today, except for Cornish pumps in museum exhibits, they are no more.

Grass Valley’s Empire Mine By 1900 the Empire was the showplace of all the California mines. The principal owner, W. B. Bourne Jr., had San Francisco architect Willis Polk create a “cottage”—actually a mansion—on 13 acres of lawn, complete with pools and an artificial lake. Over at the North Star, it became clear that some power beyond men’s and mules’ muscles would be needed to continue mining. Near the turn of the century the president of North Star Mines, James D. Hague, wanted something modern, perhaps an electric plant to power the mining equipment. But the engineer he hired, Arthur de W. Foote, thought electricity was not yet safe or dependable enough to run the whole mine. Instead, he devised

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a system using water to drive a metal waterwheel connected to an air pump that would produce compressed air to run the jackhammer and other machinery. The Pelton Engineering and Shipbuilding Company of San Francisco was chosen to build the wheel, but they refused to build one 30 ft (9 m) in diameter, the size Foote wanted. Fifteen feet (4.5 m), they said, was as large as would work. Foote persuaded them to build an 18 ft (5.5 m) one, which, for a time, was the largest in the world. But its distinction did not last long. By 1898 a much larger wheel was needed for the mine, and this time the Pelton company agreed to provide a 32 ft (9.8 m) one. This monster, the largest in the world, was made of steel with bronze buckets. Today the Pelton wheel is on display at the North Star Powerhouse Plate 40. Stratcor tungsten mine. on Wolf Creek, in Grass Valley, now a mining museum. Another small, now-silent mill, rescued from the Golden Center mine, also stands in the historical exhibit on Wolf Creek. Inside the old powerhouse are other mementos of mining days gone by. In 1933, when the price of an ounce of gold was raised by the government to $35, mining boomed and Grass Valley and the Empire continued to flourish until 1942. President Franklin Roosevelt, who had been responsible for the gold-mining boom in the midst of the Great Depression by raising the price of gold, now signed War Production Board Order L-208, causing all American gold mines to shut down. Many American mines, which produced gold as a by-product in the mining of lead, zinc, and other sorely needed metals (pl. 40), were ordered to stop working. That rule was soon changed, as the other metals were vital to defense. Because the North Star also produced tungsten, a part of the mine was allowed to remain open, and in 1944, the Empire-Star mines were given permission

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to run using no more than 175 men. The L-208 order was a disaster for the gold mines. Only a few with adequate capital could afford to keep the mines pumped clear of water. When the order was lifted in 1945, only gold dredges and a few California lode mines reopened. But the days of the mines in Grass Valley were numbered. The companies limped along, mining at a loss, hoping the price of gold would be adjusted, but it was not. In 1956, the North Star shut down for good, and in 1958 the machinery and equipment of the Empire-Star mines were sold at public auction. No one knows for sure how much gold the Grass Valley mines produced, but it has been estimated that the lode mines yielded nearly 13 million ounces worth $1.3 billion when gold is only $100 an ounce. Today, the Empire grounds are a state park, where you may visit the mining days of yesteryear (table 11). The mine itself, however, is still owned by Newmont Mines, one of the nation’s most aggressive and progressive mining companies, so its future may not be wholly settled.

Other Minerals Gold is not the only valuable mineral found in the Sierra Nevada. The peridotite group of rocks is host for many mineral deposits. Asbestos fibers that have grown within the serpentine were mined near Copperopolis; chromite deposits (from which the metal chromium is derived) are scattered throughout the heavy, dark rocks and are now and then mined, depending upon our national need; magnesite (an ore of magnesium), the semiprecious gemstones chrysoprase and idocrase, as well as the striking green mica mariposite are in rocks related to the serpentine belt. In the 1960s, deposits of nephrite jade were recognized in serpentine in Mariposa County, not far from Yosemite National Park. Since these deposits are in the heart of the gold country, you may wonder if the Chinese miners of yesteryear overlooked them, did not recognize them, or because they valued jade more highly than gold, simply mined and did not tell. There have never been extensive iron mines in the Sierra Nevada, but unexploited iron reserves exist. Most of them are too text continues on page 234

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TABLE 11

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Exhibits of Mines and Mining Equipment

Alleghany Mining Museum Alleghany, Sierra County

Underground museum with historic equipment Tours of Sixteen-to-One mine available

Amador County Museum Jackson, Amador County

Scale models of North Star stamp mill Kennedy mine tailing wheel and Kennedy mine headframe on museum grounds

Angels Camp Museum Angels Camp, Calaveras County

Large mining equipment

Calaveras County Museum San Andreas, Calaveras County

Geology of gold country

California State Mining and Mineral Museum Mariposa County Fairgrounds, Mariposa, Mariposa County

Large collections of minerals, gems, and rock Replicas of gold-mining tunnel, mining assay office, model stamp mill

Columbia State Historic Park Columbia, Tuolumne County

Rocky bed of ancient river exposed by hydraulic mining Townsite, historic equipment, scalemodel hydraulic monitor

Downieville Museum Downieville, Sierra County

Mining tools

El Dorado County Historical Museum Placerville, El Dorado County

Items from the gold rush

Emigrant Trail Museum Donner, Nevada County

Memorializes ill-fated Donner party

Forest City Historical Association Museum Forest City, Sierra County

Mining implements, Pelton wheel, gold scales

Forest Hill Divide Museum Foresthill, Placer County

Exhibits on mining

Gold Country Museum Auburn, Placer County

Exhibits on gold rush and history of gold mining

Gold Discovery Museum Visitor Center

Many mining exhibits, video, rangers to answer questions

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Marshall Gold Discovery State Historic Park Coloma, El Dorado County Golden Drift Museum Dutch Flat, Placer County

Focus on hydraulic mining

Gold Run Roadside Rest Gold Run, U.S. Interstate 80, Placer County

Hydraulic mining pit with gravel bed exposed (Tertiary river)

Kennedy Wheels Jackson Gate Jackson, Amador County

Tailing wheels, headframe

Malakoff Diggins State Historic Park North Bloomfield Museum in park North Bloomfield, Nevada County Hydraulic mine, townsite, mining equipment Mariposa County Museum and History Center Mariposa, Mariposa County

Mining exhibits

Marshall Gold Discovery State Historic Park

See Gold Discovery Museum

North Star Mining Museum in State Historic Park Grass Valley, Nevada County

Stamp mill Pelton waterwheel, mining equipment

Placer County Museum Auburn, Placer County

Hologram image of early miner

Placerville, El Dorado County

Underground mine open to visitors

Plumas-Eureka State Park Johnsville Star Route Blairsden, Plumas County

Stamp mill, tramway, mining equipment

Sierra County Historical Park and Museum Sierra City, Sierra County

Working stamp mill, mine tunnel, blacksmith shop

Tuolumne County Museum and History Center Sonora, Tuolumne County

Tuolumne County Gold collection

William Cavalier Museum Columbia, Tuolumne County

In Columbia State Park

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Plate 41. Cool Limestone Quarry, State Hwy. 49, El Dorado County. Limestone from here has been crushed and used to make cement for many years.

remote and in bodies too small to be economically valuable now. So long as iron can be mined more cheaply elsewhere, or can be recovered from the dumps that threaten to overwhelm us, Sierran iron should not be called upon. One small deposit, high on the slopes of the beautiful Minarets, is contained in flat-lying lenses in metamorphosed volcanic rock. The ore is magnetite, one of the few minerals that can be identified by noting its pull on the needle of a compass. Hikers exploring the sharp Minarets (although the ore bodies are flat lying, the mountains are exceedingly steep) should remember that their compasses may be deflected by the magnetite to give them false directions. Evidence that deposits of the ores of many metals are derived from hot mineral waters comes also from hot springs on land. Modern hot springs, and by inference, ancient ones as well, deposit mercury, sulfur, and even gold as they bubble out on the surface of the Earth. Steamboat Springs, a spa at the foot of the Sierra in Nevada, is one of those known to be depositing silver and gold today, in very small quantities. It probably takes its origin not from the heat of the now-cooled Sierran granitic core as seen in Yosemite, but rather from the more recent volcanic source along the eastern Sierra.

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In some places where molten granite has come in contact with the old metamorphic rocks, a host of “contact metamorphic” minerals have resulted. Many of them are interesting to collectors, some are rare and beautiful, and a few are in sufficient quantity and of sufficient value to constitute ore. Among these contact deposits are ores of the metals tungsten and molybdenum, formed along the junction of granitic and calcareous rock The largest tungsten mine in the world is in the Sierra, at 11,000 ft (3,353 m) up Pine Creek outside of Bishop. Both molybdenum and tungsten, used especially to harden steel, were derived from this presently closed mine, set in some of the most spectacular of Sierran scenery. Ore from the Pine Creek and adjacent mines is found mixed with garnet. Most of the garnet is pale to reddish brown; it has been sold as an abrasive but is not gem quality. Other tungsten mines and prospects contain garnet also, and there are superior collecting localities in the Sierra, such as Garnet Hill in Calaveras County.

Water Many times more valuable than gold is that simple and common, but extremely necessary, mineral resource: water. The bulky Sierra Nevada, standing as it does between the rest of California and the eastern deserts, interrupts much of the rain and snow generated across the Pacific Ocean. The western slopes of the mountains themselves are well watered, but the land beyond, as writer Mary Austin put it, is a “land of little rain.” California’s forty-niner gold rush began when James Marshall found a flake of gold in water. And water was the key to gold rush mining. Miners stood knee-deep in water, searching for the elusive metal, using water to prospect for it, and water to concentrate it. Without water, mining can barely work. The most prodigal form, hydraulic mining (fig. 42), required enormous amounts of water. One mine alone, the Spring Valley mine at Cherokee Flat, used 36 million gallons (136 million liters) of water every 24 hours, or about three times what the city of San Francisco needed. All of this came from the Sierra Nevada, through an expensive network of dams, reservoirs, and artificial watercourses. Dams upstream on the American, Bear, Yuba, and Feather Rivers could

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Figure 42. Hydraulic miner manning a monitor in the 1860s, Grizzly Flat, El Dorado County.

impound 50 billion gallons (190 billion liters) and supply it to miners through 7,000 mi (11,270 km) of ditches. Mining was given top priority and unusual privileges in California by law. California had been founded on gold, and many of its legislators were, or had been, gold miners. Miners could take water from the mountains and use it as they wished, with no regard for those downstream. Lawyer-historian John S. Hittell, writing in 1858 on the mineral resources of California, summed it up: There is no limit to the amount [of water] which a man may claim. He may take the largest river in the mountains; he may take a dozen of them and hold them all. He may not only take all their water, but he may take all the land necessary to use it. He may make reservoirs covering hundreds of acres. He may make ditches a hundred miles long. All that is necessary to give him a possessory title to the water and the land, is that he should drive stakes along the route of the ditch, post up notices of his intention, and commence work in building the dam and cutting the ditch. (Hittell 1858)

As California’s population grew, water supply became a concern, and engineers began to build reservoirs throughout the countryside, wherever there was a suitable canyon or valley. Finally, in 1914, in spite of desperate opposition by John Muir and

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Plate 42. Convict Lake. The lake is named for six convicts who holed up in the canyon after escaping from the Nevada State Prison in 1871. Posses cornered them in the canyon, but the convicts escaped after killing Robert Morrison, a Wells Fargo agent. Three were captured several days later; two were lynched en route back to the penitentiary. Robert Morrison is memorialized in Mount Morrison (12,277 ft [3,742 m]), which towers over Convict Lake. The lake lies in a U-shaped canyon, carved by glaciers of the Great Ice Age. In 1953, the slopes of Mount Morrison yielded a fossil graptolite nearly 500 million years old, which for a time held the record as the oldest fossil found in the Sierra Nevada. (Graptolites are colonial animals that have left only their horny organic tubes, generally squashed onto black shale. Their fossils are very common in the Paleozoic Era, especially the Ordovician Period). But science marches on. An even older fossil—570 million years old—has been found near Big Pine.

the newly created Sierra Club, a reservoir for the city of San Francisco was created in the lovely sunlit meadows and forests of Hetch Hetchy Valley in what was called the Grand Canyon of the Tuolumne, 20 mi (32 km) north of Yosemite Valley. Today the crowds that stand in line to see the priceless 1 by 7 mi (1.6 by 11.3 km) space of Yosemite Valley make it plain that the earlier choice to inundate Hetch Hetchy was an action against the long-term national interest, just as John Muir, the newly created Sierra Club,

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and many others said it was. But it will not be lost forever. Once capable of holding 100 billion gallons of water, the reservoir is silted up and probably will have to be abandoned as a storage facility. What will happen to it then is not yet known. Will it be allowed to return to meadowland? Can its beauty be cleaned and restored? We can only wait and see. On the eastern side of the Sierra Nevada, where the land is dry, there were no big hydraulic mines or large cities. Instead, water itself became a commodity to be bought and sold. Because it became a commodity available to the highest or trickiest bidder, the Eastern Sierra virtually dried up, not just for farmers, although

that was a tragedy, but for other life as well. As Genny Smith wrote in Sierra East (2000, 450– 452), Eastern Sierra creatures have far less water available than their kin on the western Sierra slope. Still, the snowpack on the Sierra’s eastern flanks gives birth to five rivers: the Susan, Truckee, Carson, Walker, and Owens. None of them reaches the ocean; instead, they terminate in desert lakes and marshes. Today many of these waters are in a sorry state, either dry or drastically shrunken. The large numbers of animals that depended on them historically are no more; some populations are extinct, a few species are near extinction. Winnemucca and Owens lakes are dry. Only a small remnant of Honey Lake remains, as a wildlife refuge. Pyramid Lake has dropped more than 70 feet (21.3 m), Walker Lake over 100 feet (30.5 m), Mono Lake over 40 feet (12.2 m). Of the Carson Desert’s once extensive wetlands, few remain. The Eastern Sierra flyway, once a major migration route for millions of ducks, geese, and other birds, has all but disappeared. The famed Lahontan Cutthroat Trout and Eagle Lake Trout can no longer reproduce naturally but are spawned and reared in fish hatcheries. “Bathtub rings” mark exposed shorelines that generate tons of polluting alkali dust. What has happened to the Eastern Sierra’s bountiful water? It’s a long, convoluted story that is believable only if you understand that in the desert farming is impossible without irrigation and because water is scarce, it is as precious as gold. In the desert water is something to covet, to buy and sell, and to get title to by stealing, treachery, or any other means. Something that still generates bitter disputes and lengthy court cases and still bestows power and wealth. Something that in the late nineteenth century

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induced extravagant dreams of converting thousands of desert acres into green fields with brimming canals. Something that stirred the imagination of dreamers and water engineers. Some of these dreamers were public-spirited; others were speculators, boosters, or at worst, con men. Some went bankrupt, borrowing money and losing all of it. Those taken in by the exaggerated claims and promises of cheap water and land often lost their money and their land.

The project that robbed most of the lakes, streams, and marshes of their water and converted them into desert was the Los Angeles Aqueduct. By stealthily buying rights to the water in the southern Sierra, using bribes and threats, Los Angeles was able to divert the mountains’ water to cities along the coast. It was a brilliant engineering project, second only, Smith says, to the construction of the Panama Canal. Using no pumps, water was carried by gravity through a series of pipes, canals, tunnels, siphons, and reservoirs all the way to Los Angeles. “During the hard times of the 1920s,” wrote Smith (2000, 460) “—with many farms mortgaged and with widespread hopelessness and bitterness over the city’s trickery and broken promises — valley feelings erupted, and peaceful farmers turned to violence. Between 1924 and 1927 valley farmers blew up the aqueduct seventeen times; at one point they . . . turned all water out of the aqueduct for five days.” Los Angeles, even then, was a large city, and it got its way. As late as 1970, the city constructed a second aqueduct, and expanded its groundwater pumping. But the times are changing. People are beginning to realize what they have lost and are still in danger of losing. There were and are many lawsuits, with many litigants, and not all are settled. Mono Lake is receiving more water to keep it from extinction, and diversions from Eagle Lake have been stopped. “Water competition in California has always been a confiict between the public interest and private gain,” wrote Verna Johnston in Sierra Nevada: The Naturalist’s Companion (1998, 144). “The latter view, blind to our role as a part of nature, is equally blind to our feel for the roar of a wild river’s cataracts, the churning of its white water, its clear pools and fellow forms of life.”And it ignores that the lives of rivers and streams affect the lives of all of us—humans included.

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CHAPTER 8 LANDSCAPES OF YESTERYEAR

Overleaf: Fall aspen at Two Teats. Two Teats (only one Teat is visible here) is the remains of a large volcanic dome erected two to three million years ago, at the time of the Great Ice Age. The dome exploded, throwing volcanic debris in the air. What we now see is what erosion has left of the ejecta catapulted out. (See also pl. 43.)

IF YOU WERE planning a hike in the Sierra of 100 million years ago (of course, you would not be, because humans did not exist yet) you might have been surprised to find you had no steep, lofty peaks to ascend, as Clarence King did. The mountains we know today do not look like those of yesteryear. About 130 million years ago, in the early part of the Cretaceous Period after the gold veins had formed, the Sierra Nevada entered a phase of deep erosion. At that time, the western sea had its shores within the Great Central Valley, as attested by remnants of beach and offshore mud now turned to stone. The mountains, much lower than the ones we know, were being ground even lower by rain and snow, the mountain fragments — including gold—washing down streams toward the sea or staying to help form soil. Although the Sierra Nevada is not a fossiliferous mountain range, enough animal and plant fossils remain for us to know that in the hills and shallow bordering seas, life flourished in abundance. Until recently, geologists have considered that there was a break in our record of Sierran history at this point (an “unconformity”), marking a period in which the Sierra and its cooled

Figure 43. The Yuba River near Downieville, flowing through old metamorphic rocks.

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granitic core were steadily eroded. New evidence, including the age of granitic rocks in actual years, points to a more complex story: even as erosion was stripping the mountains to carry their fragments to the western sea, parts of the granitic core were still hot, perhaps still moving upward. Some parts may still be rising. At any rate, erosion during the Cretaceous and part of the early Tertiary Period wore the mountains down—down far enough to lay bare the tops of the gold-bearing quartz veins formed deep within the range. Several geologists have tried to estimate the amount of rock torn from the mountains, using various types of calculations. Although they do not agree exactly, all suggest that 9 vertical miles (15 km) or more of rock was removed during this 25-million-year erosive interval, or .5 to 1.5 ft (15 to 45 cm) per thousand years.

Cenozoic Landscapes By Cenozoic time, commencing about 65 million years ago, the Sierran landscape was quite different from the deep oceans of the Paleozoic or the mountain fastness of today. A shallow, lagoonmargined sea lapped quietly against the foothills of a much lower range. The lagoons have left their mark in the remnant clay, white quartz sand, and coal beds to be seen in the foothills along the edges of the Great Central Valley, especially near the towns of Ione and Buena Vista. A substantial clay industry harvests the clay laid down in those still lagoons. Lignite coal found near Buena Vista, Ione, and Carbondale reminds us that the lagoons were probably lined with trees and plants—perhaps even choked with them—enough to form thick mats of dead and dying vegetation that turned from peat to soft coal, rather than mixing with mineral fragments to become soil. A California market for soft coal as a fuel no longer exists, but the mines are sporadically worked to recover a very hard commercial wax. Judging by the fossil remains of plants found in the old gravel beds of the rivers that fed the sea, the climate was subtropical, similar to parts of Mexico today. Temperature on land probably averaged 65 degrees F (18 degrees C), somewhat cooler than the

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Plate 43. One of Two Teats, eastern Sierra Nevada, above San Joaquin Ridge, clothed in fall foliage. Two Teats is a remnant of a large dome of two to three million years ago.

adjacent 70 degrees F (20 degrees C) of the sea. Frost was rare in lower elevations; 60 in. (150 cm) of rain fell in the warm season on the dense vegetation near the coast, perhaps as much as 80 in. (200 cm) in the uplands. This estimate of the climate was made by paleobotanists who studied the fossil remains of trees, shrubs, and vines found in mining pits. For more than a century at the Chalk Bluffs hydraulic gold mine, near You Bet, Nevada County, and at other places along the course of the Yuba River where it ran in Tertiary time, it has been possible to find fossil plant remains. That is, it was possible. You can no longer find fossils in some of the better known localities such as Remington Hill, for thoughtless collectors, many of whom have neither use for nor more than passing interest in their acquisitions, have removed them all. Those fossils that were collected for their scientific use have given us a picture of the woods of those days. Although most plants that became fossils were those that lived in lowlands, where they were quickly buried and therefore have been preserved, some idea of the forests in the hills can be derived from the winged seeds

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Figure 44. Sierran rivers of Tertiary time. The older channels, called here “Tertiary channels,” are those of about 50 million years ago. The “intervolcanic channels” are younger, dating from approximately 30 million to two million years ago (but also Tertiary).

and more durable leaves that floated into the river beds.Along the high river banks, red gums (liquidambar), laurels, figs, and woody climbers grew luxuriantly among the oaks and magnolias. Higher in the hills, oaks, laurels, witch hazels, small palms, cycads, hick-

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orys, and persimmons grew, but no conifers, indicating that this was a humid upland forest of broad-leafed hardwoods. If the underlying rock in such a tropical forest is greenstone, serpentine, peridotite, or one of their relatives, a peculiar bright red clay is likely to form as soil. This clay, called “laterite” (from the Latin word for “brick”), is rich in iron and sometimes nickel — rich enough in nickel in some places that it is an ore. Up and down the Sierran foothills, you can see this startling red soil (colored red by the iron), a reminder of the warmer, moister tropical climates of yesterday. At Camptonville and Ione, the color seems unusually bright; those who walk in it, or have small children who do, remember it long and sadly on washday.

Tertiar y Landscapes Throughout most of Tertiary times, the Sierra continued to be much lower in than it is today. Close to the shores of the subtropical sea, a belt of resistant greenstone ridges rose to elevations of 1,000 to 1,800 ft (300 to 450 m). Rivers—not where they are today—cut through the ridges in several places, flowing through narrow canyons (fig. 44). East of the greenstone belt, the area that is now the gold country was a flatland underlain by upended slate beds; into it the valleys of the Tertiary rivers were cut. These river valleys were broad, with the main course of the river in the center of the valley, its channel incised into fresh bedrock as much as 40 ft (12 m) below the general valley level. From the plain, the hills rose gently eastward, reaching an altitude of as much as 3,000 ft (900 m) along the crest. A few isolated peaks stood out from the rest: Mount Dana, in Yosemite, for one, and Pyramid Peak for another.

Life in the Tertiar y Perhaps land birds lived in those old forests, and water birds waded in the mudflats along the streams and in the ponds and oxbows. Insects must have hummed in trees, and earthworms and snails burrowed in the soil. But we have little record of them here. What fossils of Tertiary land animals we do have are chiefly

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remnants of teeth and bones of larger animals: browsers and grazers in the savannah. Near Knights Ferry, close to Tuolumne Table Mountain, paleontologists have unearthed the remains of two little horses (Nannipus and Hipparion), two camels, a pronghorn antelope, and one tooth of a mastodon. Nearby, at Oakdale, fragments of two ground squirrels and a rabbit, two other small horses (Neohipparion and Pliohippus), a small camel, and another pronghorn were buried. Since no bones of dogs, wolves, cats, or other predators were found, these burials may represent the remains of meals eaten by predators of the grasslands for which we have no fossil record. Although these particular animals did not live at the beginning of this erosive period (they lived in the Pliocene, about three million years ago), surely their ancestors lived in the same area 60 million years ago. The little horses eventually gave rise to Equus, our horse of today, but the horse vanished from North America with the Great Ice Age. When the Spanish Conquistadores came to the New World on their fine steeds, no native had seen such an animal.

Creatures of the Sea Although the dry land preserved few fossils to tell us of its inhabitants, the sea lapping at the foot of the Sierra harbored many sea creatures, some of whom left their bones and teeth for us to find. One famous place, Sharktooth Hill, has been called the most significant Miocene marine locality in the world. It lies in the low foothills of the range near Bakersfield and contains an enormous number of sharks’ teeth of Miocene age (15 million years ago). In May 1976, privately owned Sharktooth Hill was included in the United States Landmark Registry. Sharktooth Hill, as designated, includes the southern exposure of a rich fossil zone in the Sierran foothills, although other hills in the area are also fossiliferous. Many thousands of shark teeth have been found in the landmark, and because sharks have soft cartilaginous, rather than bony, skeletons, teeth are all they have left us as their legacy. Besides shark teeth, the site has provided bones of more than 47 species of extinct fishes, birds, and mammals, many of which were new to science when found.

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Their home in Miocene times was the inland Temblor Sea, probably about 200 ft (60 m) deep, lying in the San Joaquin Basin, now raised by Earth movement to be part of the Sierra Nevada foothills. The fossilized bones of sea cows indicate a tropical or semitropical climate when the sea cows were alive. Sea lions, turtles, whales, walruses, shore birds, ocean birds, porpoises, and dolphins lived there, as well as Desmostylus (an extinct hippolike mammal), rays, and skates, some of the rays reaching several hundred pounds in weight. When the sea dried, the sediments on its bottom lithified to soft rock. The richest bed, which ranges from four inches to nearly three feet thick, is extremely fossiliferous: one cubic foot may contain more than 100 individual bones and teeth. The official Sharktooth Hill is not the only fossil ground in the region; other hillsides are prolific. Bob Ernst, a nearby fossilcollecting land owner, said he once found 187 shark teeth in an 18 by 18 in. area on his property. Why should so many fossils be packed together in a fairly thin bed at Sharktooth Hill? One suggestion, advanced early in the twentieth century by a paleontologist with the California Academy of Sciences, was that volcanoes erupted violently, throwing out ash and poison gasses that quickly snuffed out the life in the Temblor Sea. Certainly, volcanoes were active at this time, and an unconformity indicates that the land was rising, cutting short normal deposition in the sea. Another suggestion was that the area of Sharktooth Hill was in an inland bay. When the topography was suddenly changed at one end of the bay— again, an uplift by Earth forces — what had been a gently sloping marine slope was transformed into a steep, nearshore submarine canyon that quickly filled up with silt and sand. When the animals died, strong sea currents pushed them into the submarine canyon, building up a tightly packed wedge of dead animals. Or, perhaps a “red tide” may have killed the animals. Red tide is caused by a marine microbe that contains a minute amount of poison. Fish that eat it die, and fish that eat contaminated fish die, until all in the area have been poisoned. The guilty microbes, according to this idea, were not fossilized. The remains of land animals, too, have been recovered at Sharktooth Hill, especially camels, tapirs, and horses, but few invertebrates and no microscopic organisms. Pyramid Hill, five text continues on page 252

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o doubt the Indians knew of Sharktooth Hill, because so many teeth weathered out of the layers of sedimentary rock that the ground was littered with them.The tooth fairy could have gone broke replacing teeth with wampum.The first white society knew of it was in 1853, when geologist William P. Blake’s report, written for the government’s Pacific railroad survey, was published. For the rest of the nineteenth century, amateur fossil collectors haunted the hill. One, Charles Morrice, a clerk for the Pacific Oil Company, dedicated himself to collecting Sharktooth Hill fossils. He amassed thousands of them—several tons—finally donating his collection to scientific institutions throughout the world. One such institution was the California Academy of Sciences, which in 1924 launched a four-month search of the fossil hill, then continued to study the fauna for several years, resulting in the naming of 18 new species and 11 new genera of extinct mammals, birds, and fish. From 1960 to 1963, the Los Angeles County Museum of Natural History undertook another scientific investigation, not simply collecting, but carefully extracting the fossils and noting the relationship of the fossils to one another and to the bed in which they lay. During the study, the museum found an almost perfect skeleton of an extinct sea lion that offered much information on the evolution of sea lions. Since then, various colleges, in California and elsewhere, have launched field investigations. In 1981, the National Science Foundation financed a large-scale study by more than 50 scientists from various institutions that yielded several hundred pounds of teeth and bones. A lot of shark teeth can come from a relatively small number of sharks. Because teeth are not permanently attached to a shark’s jaw, they can easily be broken or lost, but sharks can quickly regrow them, so one shark may leave a great number of teeth to be fossilized. Even so, many hundreds of pounds of teeth have been found (and collected) and yet many remain. Surely there must have been a substantial number of sharks in the area at the time to be so generous with their teeth. About 300 species of sharks are known in the world today, as fossils or as dwellers in the sea. Sharks have been on Earth for more than 450 million years, first as “ancestral” then as more advanced sharks.This is about three times as long as the dinosaurs, and 100 times longer than humans.All sharks have a torpedo-shaped body, a cartilaginous skeleton, and fins.As time went by, shark teeth became specialized into several different types.Those who study shark teeth can easily become confused, because teeth of the young are different from those of adults, upper jaw teeth are different from those in the lower jaw, teeth may

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change as the shark grows older, teeth of females may differ from those of males, and some sharks have teeth malformed by injury.Although a shark’s jaw may look to a frightened swimmer as if it is a mighty, curved saw, the teeth are actually of several different types (as are human teeth).“Intermediate” teeth are between the front and lateral groups, but even sharks of the same size and species may have intermediate teeth Plate 44. A tooth of 13- to 15-million-year-old fossil Carcharocles megalodon (left) from Sharktooth Hill compared with a modern Great White Shark (right). The fossil shark’s tooth is 5.5 in. in slant height, and 3.9 in. ( 9.8 cm) wide; the modern shark tooth is 2.6 in. (6.7 cm) in slant height and 1.75 in. (4.4 cm) wide.

of quite different sizes. Some shark teeth are sharp, with triangular serrated edges. Some are long and needlelike, some flat and platelike. Today’s Great White Shark (Carcharodon carcharias), also called the man-eater, was the prototype of the shark in the motion picture Jaws. In the film, the shark was only 25 ft (7.6 m) long, but great whites, judging by their jaws, can be almost 30 ft (9.1 m), probably weighing about 4 tons.The largest tooth of a great white is about 2.5 in. (6 cm) long. Great Whites are fast, extremely powerful, and very dangerous, accounting for the majority of shark attacks on people, most of which are fatal. People are not their only food; they also eat whales, sea lions, fish including marlins and tuna, elephants, sheep, pigs, horses, dogs, and just about anything else they can get their jaws around. The Great White is a smaller, perhaps less ferocious version of the monster fossil shark of Sharktooth Hill, Carcharodon megalodon. Some of C. megalodon’s teeth were 8.25 in. (21 cm) long and weighed over a pound apiece (pl. 44). In 1909, scientists at the American Museum of Natural History, using fossil teeth, calculated C. megalodon to be 90 to 120 ft (27 to 37 m) long with a mouth large enough to drive a bus through. In the 1970s, a scientist recalculated the size, this time taking into account the height of tooth enamel, making C. megalodon only 45 ft (14 m) long. However long it was, C. megalodon was the terror of the Temblor Sea and ranks as the largest predatory fish of all time. It became extinct at the end of the Great Ice Age, which is not so very long ago.

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miles away, has a rich fossil bed that is somewhat older (Oligocene) and contains many invertebrate fossils (especially gastropods and pectens), as well as sea lions, seals, and sharks. Despite over a hundred years of collecting, fossils are still left. However, nothing is bottomless; no animal is too numerous to not go extinct, as we learned from the passenger pigeons, flights of which, in the nineteenth century, darkened the sky. The last passenger pigeon died in the early twentieth century in a zoo in Cincinnati. So, too, may shark teeth vanish from Sharktooth Hill. As of this writing, plans to develop Sharktooth Hill and its environs for housing development, including a six-lane highway, could easily come to fruition, destroying the magnificent fossil source forever.

Where the Tertiar y Rivers Ran The courses of the Tertiary rivers that flowed through the mountains and plains to the sea are surprisingly well known, in comparison with the little that is known about other, more readily observable geologic features in the Sierra Nevada. But when one considers the reason they are well known, it seems less surprising: they contained a great deal of gold. It is remarkable that a record so tenuous as the course of a stream 50 million years old should be knowable at all. But through long, slow days and sudden cataclysms, nature saved enough remnants of the streams to mark their courses. Thousands of miners and dozens of geologists have toiled many years to trace the antique stream courses. Entire streambeds are not preserved, of course. Most of the gravel beds that choked the channels are long gone—erased by the forces of erosion. Only patches now remain, but from these patches, fossil landscapes can be resurrected (fig. 45). Some of the patches were preserved beneath lava flows or volcanic ash falls, and some were buried quickly under other sediments. The ash that fell from those violent volcanoes of millions of years ago lay lightly on the land in the foothills, blowing and drifting. Where it fell into water, it sank slowly to the bottom, covering and preserving the gravel in the stream channel. In

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places, it dammed the Tertiary rivers, forming lakes with layers of ash on their bottoms. The tougher, later lava flows, too, filled some of the channels, forcing streams to make new roads to the sea. In this way, a whole new set of Tertiary streams was created. In a few places, the streams followed the same courses; elsewhere, the old channels were buried, gold and all. The new streams cut through the old ones here and there, robbing them of their gold, to add it to the gravel of their own beds. The oldest channel gravel deposits—those of Eocene age— the miners called “blue gravels.” They were the deepest, richest, and most sought. Natural riffles in the bedrock in these old channels halted the gold, creating very rich gold pockets. Where the old streams flowed over limestone, the pockets were exceptionally rich. The gold rush towns of Columbia and Volcano are built on limestone. Above the deep gravel deposits were what the miners called “bench gravels,”which were the floodplain deposits of yesteryear. In places, these floodplain beds were as much as 300 ft (91 m) thick. Sometimes, revitalized streams cut through the bench deposits and left deposits of their own, deeper down than the bench gravels, although younger. In some places in the gold country where much of the story of the Tertiary rivers has been deciphered, it has proved to be very complex. At Mokelumne Hill, a series of eight channels was incised into the landscape in the 50 million years from early Eocene to late Pliocene time. At Oroville Table Mountain the whole gravel sequence is covered by basalt, while at Tuolumne Table Mountain a covering of light-colored volcanic rock fills the streams and caps the gravel beds. Last Chance, in Placer County, has three channels; because the streams here gained in power as time went by (owing to more water or a steeper gradient or both), the youngest channel is the deepest. By the 1860s, hydraulic mining was well underway, ripping the aged channels apart by a blast of water forced through the nozzles of huge hoses. This type of mining was the most rapid erosive force in the history of the Sierra Nevada (fig. 46). All through the gold country are pits dug by these water jets. At Columbia, Volcano, and at other spots in the Mother Lode, the hoses washed right down to bedrock, exposing the course of the long-vanished river. All told, 1,555 million cubic yards (1,189 cu m) of debris — text continues on page 256

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Figure 45. A stream of Early Tertiar y time (about 50 million years ago) as it meanders through the gentle western slope of the Sierra Nevada.

Upper left, In the lower foothills, the stream encounters a ridge of resistant greenstone; it has cut through the ridge to plunge over a waterfall to the region underlain by soft rock below and to the west. A cutout of the stream channel shows gravel in the bottom of the bed. Mixed with the gravel are nuggets and tiny fragments of gold, worn from the higher mountains and being carried by the stream toward the sea. Lower left, About 30 million years ago ash, falling from volcanoes erupting higher in the mountains, has clogged the stream. Where once the stream poured over the greenstone ridge in a rushing water fall, a dam of ash has ponded the water behind the ridge. In the cutout, ash may be seen covering the gravel of the river bottom. Upper right, Steaming volcanic mudflows beginning about 20 million years ago roll downhill from near the Sierran crest, covering much of the landscape. Here, the stream has been forced to seek a new route

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through the greenstone ridge; parts of the ridge and about half of the streambed in the foreground have been covered by the mud. The cutout shows a succession of deposits, including the original gravel in the bottom of the channel, followed in turn by ash, then partly covered by a mixture of volcanic mud and rock.

Lower right, The mud has cooled, and a new river has established its way through the greenstone ridge. The original route of the stream behind the ridge is now abandoned. The new stream course crosses the abandoned channel in the background; where it crosses, the stream may steal gold from the older channel. Where the channel lies buried and untouched by the new stream, gold may be locked beneath the ash and volcanic mud. The cutout shows an older, buried gravel deposit and ash bed, a volcanic mud layer, and a new gravel layer. Because the stream now has more water, and therefore more erosive vigor, the new deposit is actually lower than the older one. Part of the older gravel in the bottom of the bed and part of the covering ash have been reworked by the modern stream.

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Figure 46. Hydraulic mining, the strongest human erosive force in Sierran history, in a few years managed to wash whole hillsides into the Sierra’s rivers, silting up the rivers and devastating farmlands. In this injured landscape, a flowing stream has encountered a steep cliff cut into gravel by hydraulic monitors that have washed away much of the original hillside.

eight times as much as was dug from the Panama Canal — was sloshed away to be washed down rivers to flood farmlands and silt navigation channels. During the heyday of this fire hose mining, miners took several hundred diamonds from the same sluices they used to recover gold. They were not searching for the gems, and because diamonds were not easy to see among pebbles of rock and quartz that looked very much like them, no doubt many more were crushed in the mining process or washed down the rivers. In the 1980s, searchers found several large diamonds in the old hydraulic pits. In 1884, hydraulic mining was virtually halted by a court injunction that became one of the first legal milestones in the battle to protect our environment. Thereafter, the court ruled, hydraulic miners could mine only if they contained their waste behind suitable dams so as not to clog the navigable waters. Although this meant only the mines on streams tributary to the San Joaquin and Sacramento Rivers (the only two California rivers classed as navigable), few mines survived the ruling. It was too “expensive” to take care, and hydraulic mining essentially ceased.

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Some mines continued to operate behind dams, but they were small, in no way comparable to the giants of the 1860s. Figure 44 shows the courses of some of the ancient rivers that have been pieced together. No doubt, venerable gravel beds are still hidden in the gold country, containing rich “virgin” placers. It is also possible that if you could trace accurately the shores of the old Eocene sea, you might find deposits of no-see-um gold mixed in with the muds of the deltas of fossil rivers. But these muds are our rich soils, worth far more than a handful of gold.

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CHAPTER 9 DAYS OF FIRE

Overleaf: Base of columns, Devils Postpile. Under uniform conditions, which are rare in nature, cracks like these tend to form more or less at once in a cooling fluid mass. Here a lake of molten lava cooled suddenly into columns, fairly straight in the center of the lake, but bent where the edges of the lava lake met the ground. About half the volcanic columns are six-sided, the most structurally efficient shape. Earthquakes in 1980 shook down a few columns and broke others, but when we consider how many earthquakes the pile has probably endured in its 100,000-yearlong history, it seems remarkable that any have survived at all.

IN 1740, the Itelmen natives on the Russian Kamchatka Peninsula told naturalist Georg Steller exactly how volcanoes work. And they should know; the peninsula is one of Earth’s most volcanic regions. Gomuls—Earth ghosts who lurked in volcanic craters— caused eruptions, they said. To feed themselves, they would leave the volcano and seize ocean whales with their spear-shaped fingers and haul them back to the crater to eat. Their cooking bonfires sent up clouds of smoke and vapor, while boiling whale fat streamed down the volcano’s slopes, and whale bones flew through the air. This explanation sounds mythological to us in the twentyfirst century, but how would our own idea that colliding Earth plates caused solid rocks to melt sound to them? Yet that is exactly what we do think. Volcanoes certainly were the surface accompaniment of the granite bodies that cooled from the great Sierra batholith. The lava was the same chemical composition as the coarser-grained rocks, and as the plutons were emplaced from west to east, so the volcanoes on the Sierran slopes were oldest to the west. The earliest date from about 30 million years ago, but many of those in the eastern part of the Sierra are far from extinct. Some could erupt at any time. Violence — fire, ice, and earthquake—are the hallmarks of the past 30 million years in the Sierra Nevada. The record written in the rocks shows it to be a time of volcanic explosions, of creeping molten lava, of roaring volcanic mudflows, a time that transfigured the landscape, revised the courses of rivers, and mantled the mountains with new rock. The long, slow movements of the Earth and the wrenching paroxysms of sudden earthquakes lifted the mountains to new heights, even greater than today. Looking backward through time it seems as though one volcanic episode followed another in rapid succession, and that the Sierra Nevada must have resembled a red-hot furnace. As far as we can tell now, that was not the case. It merely appears to be so because we have records only of “happenings” and little or no record of the long quiet intervals. In our own time, for example, it took but a few months for the Mexican volcano Paricutín to rise from a level cornfield. Surtsey, in Iceland, was born and grew in the sea while we watched on television; Vesuvius, Krakatau, Mount Pelé, and other volcanoes have exploded so suddenly that there was no escape for the life at their feet. The record of such eruptions may be thousands of feet of lava solidified upon the

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Plate 45. Eroded battlements formed of volcanic agglomerate—solidified volcanic mudflow.

landscape, new islands, or ash heaps higher than skyscrapers. These are impressive records, yet they may be the work of only hours or days. Our vision of the past is compressed, like a timelapse film, by seeing only such sudden episodes. But if we consider also the quiet intervals in the past 30 million years, the times were no more violent, proportionately, than recent times in today’s Cascade Range. Within the last century and a half, Mount St. Helens, Lassen volcano, and nearby Cinder Cone have erupted; within the past 500 years, other volcanoes in the Cascades have spewed lava and cinders. Geologically speaking, this is very active, yet we do not think of ourselves as living in the heart of volcanic danger. Not all volcanoes are equally dangerous. Basaltic ones, which spew out “basic” lava (lava that has a high content of iron and magnesium), usually erupt quietly. More dangerous are those that expel rhyolitic and andesitic lava (the so-called acid volcanoes, which have more silica).

Volcanic Landforms Each of the three types of lava—basalt, andesite, and rhyolite— not only has its own characteristic style of eruption, but also forms its own characteristic landscape. The most striking landforms derived from rhyolitic rock are great plateaus of once-hot ash fragments that poured from fissures, associated, perhaps, with rhyolitic domes and collapsed areas

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called “calderas” (pl. 46). Rhyolitic landscapes were the first to be developed in the Sierra Nevada in the Tertiary volcanic episode, and rhyolitic features have also been among the newest to be formed. Andesitic landscapes, in contrast, tend to be rough and hummocky, characterized by mudflows as well as ashfalls and the debris left from explosions. Andesite dominates the volcanic landscapes of the western Sierra Nevada.

Plate 46. Long Valley and the town of Mammoth Lakes (right, with road running through). The town sits within the Long Valley Caldera. About 760,000 years ago the roof over the magma chamber in Long Valley ruptured, blasting out incandescent ash and molten lava. The explosion partially emptied the magma chamber, and its roof collapsed, allowing the chamber to sink in on itself, forming a caldera. The caldera is now a 10 by 20 mi (16 by 32 km) depression in the landscape. Few people who drive by or hike through the area realize molten rock still lies deep beneath their feet. A series of earthquakes, commencing two weeks after the May 18, 1980, eruption of Mount St. Helens, shook the Mammoth Lakes–Long Valley area. The earthquakes did not appear to be related to fault movement, but rather to the rise of magma within the Long Valley Caldera. By the summer of 1980, the central part of the caldera had risen 10 in. (25 cm) since last measured in 1975. In the 1980s and early 1990s, thousands of earthquakes were registered in the Long Valley area, all but a handful less than magnitude 3, too small to be felt by humans. Yet the dome was still rising, worrying scientists that a volcanic eruption might be pending.

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Basalt lava provides the quietest, and from the standpoint of an onlooker, the safest of eruptions. Its landscape features are low domes, lava plains, and gently sloping, gradually built volcanoes. Hawaiian volcanoes, which entertain visitors, are of the basaltic type. Two large basaltic plains cover much of the northern Sierra. Both the older plain, of which Oroville Table Mountain is a part, and the younger plain, in the extreme north, had their origin outside the Sierra Nevada proper. Most other basaltic landscapes in the mountains are smaller, consisting of small “table mountains,” cones, columns, or rough-surfaced flows. The most conspicuous of these recent basaltic features have been added to the landscape within the past million years.

Tertiar y Explosions The initial phase of the Sierran Tertiary volcanic episode was ushered in by rhyolitic explosions. During a volcanic explosion, lava in the volcano is torn into fragments of all sizes: dust, sand, blocks, and “bombs,” collectively known as “tephra.” The explosion results from the sudden release of gas (largely steam) from the liquid lava, usually in the throat of the volcano, where the lava is under lessening pressure as it rises toward the land surface. The finest material, called “ash,” is blown far and wide by the wind; coarser material is left near the volcano, where it gradually builds the cone higher and higher. Despite their name, volcanic ashes are not the remains of objects burned by fire, but are minute rock fragments, discernible as rock under a microscope. Some of the material is so fine it can travel thousands of miles: volcanic ash from the explosion of Krakatau in Southeast Asia was blown seven times around the world, changing the color of sunsets for more than two years. The sound of the explosion was heard for 3,000 mi (4,800 km). The rhyolitic explosions of the early Tertiary left ash scattered through much of the northern Sierra. Beds of ash as much as 450 ft (135 m) thick may be seen in the gold country; rhyolite near the mountain crest is in beds as much as 1,200 ft (365 m) thick. Most of the ash (called “tuff” when consolidated) and rhyolite lies north of Yosemite National Park; whether the ash was never scattered beyond, or was so easily removed as to leave no trace, is not known. Since no vestiges remain, likely little of it settled there.

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Plate 47. Wilson Butte, a rhyolite dome on the eastern side of the Sierra Nevada. The lava erupted about 500 B.C., around the time of Socrates. The dome, like others in the Mono chain, came up as a sticky, viscous mass, like toothpaste from a tube. If the “toothpaste” hardens in the neck, it may dam the fluid rock behind it. When the pressure becomes too great, the top may blow apart in a violent explosion, such as happened in what is now Long Valley and Crater Lake, Oregon. Rhyolite and other light-colored lava contain more silica than dark-colored lava, such as basalt, which has more iron and magnesium. Basalt, which is hotter than rhyolite, can flow long distances. Rhyolite tends to be less fluid, more explosive, and therefore more dangerous.

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Plate 48. Ridge of Bishop Tuff. The ash and pumice that blew out of the Long Valley volcano 760,000 years ago covered some 580 sq mi (1,500 sq km), piling up in drifts more than 600 ft (180 m) thick. Within the Long Valley Caldera itself, the ash deposits, now consolidated into Bishop Tuff, were more than 4,500 ft (1,400 m) thick. A layer of Bishop Tuff was encountered in a well drilled on Paoha Island, Mono Lake, at a depth of 1,400 ft (430 m).

Where the volcanoes were that produced this vast amount of ash is not entirely clear, but it is probable that they stood somewhere along the present Sierran crest and to the northeast. The deposits become less “ashy” to the northeast and are more consolidated, their fragments welded together, indicating that they were hot when they fell and were not cooled by a long trip in the air or in a mountain stream. Miners knew the tuff very well; they burrowed through it to get to the gold-bearing gravel beneath. In the tunnels they dug, the tuff was light gray; the same rock, exposed to air, turned to muted shades of cream, violet, yellow, and pink. The rock is very soft and can be cut with a handsaw and chisel. Many old buildings in the Mother Lode were and are built of it; after it is sawed and dressed, the blocks can be laid tightly with a minimum of mortar. Exposure to the air not only alters their color, but also forms a hard crust that protects them from rapid damage by wind and weather. Unless they are deliberately destroyed or vandalized, structures built of tuff last a long time. Ancient Rome was built largely

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of tuff. Remains of the Coliseum are blocks of tuff, and the Forum, now stripped of its marble facing, is a tuff ruin. Old structures in the gold country, built wholly or partly of tuff, can be found as far north as Dutch Flat and as far south as Angels Camp. Cornerstones, keystones, and lintels show dates ranging from the early 1850s to the 1890s; craftsmanship ranges from the most rough-and-tumble stone walls to finely tooled blocks. As the ashfalls waned, other volcanoes in the Sierra Nevada proper began to erupt. Unlike the rhyolite, which took its origin from unidentified parts of the Sierran crest and farther eastward, volcanic rocks of the next few million years had sources that can be traced to Sierran mountains of today, some of them still warm volcanoes. The first part of these last volcanic years would have been awesome, had we been alive to see them. Those were the andesitic days, a time of hot volcanic mudflows pouring from vents in the highlands and cascading down the streams and mountainsides. The mudflows were many, from different centers in the Sierra, piling on top of one another and merging to form a sea of steaming mud. Eventually the old landscape was inundated; only ridges of resistant greenstone (a dark green metamorphic rock) in the foothills, a few peaks in the middle zone, and some high country along the crest remained as islands. Volcanologists call such volcanic mudflows by their Indonesian name, lahar. Several modern lahars have resulted in disaster: in 1919, an Indonesian volcano blew out its crater lake, forming a mixture of lava and water that roared down the mountain killing 5,500 people.

Plate 49. Glass Creek, marked by vegetation, winding its way through ash flow deposits.

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Lahars can move great distances. Those that are hot, formed with water heated by the volcano, can go rapidly; cold ones, which start cooler or are mixed with melted snow or frigid mountain stream water, move more slowly. When Vesuvius erupted in a.d. 79, people living in Pompeii, where a black, flashing cloud enveloped the town, had little time for escape. Those who were in the little neighboring village of Herculaneum were luckier. Their town was buried more slowly by 60 ft (18 m) of volcanic mud, so that most of them had time to escape. As the years

Plate 50. Rainbow Falls on the Middle Fork of the San Joaquin River, eastern Sierra Nevada near Devils Postpile. Because the falls plunge more than 100 ft (30 m) over a nearly horizontal lava bed, the water surface at the top is nearly flat, unlike the helter-skelter waterfalls developed in granite. Rainbows are best seen before noon when mist rises nearly as high as the falls.

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passed, all memory of both cities vanished until they were rediscovered centuries later. There was no doubt that the mudflow that engulfed Herculaneum came from Vesuvius. We are almost as certain concerning the origin of the lava that formed the Sierran mudflows. In the area around Relief Peak and Mount Emma, many dikes and plugs of similar composition remain. These and the Dardanelles, Castle Peak, Disaster Peak, Mount Lola, Mount Lincoln, Tinker Knob, Squaw Peak, Mount Mildred, Twin Peaks, Mount Ellis, and others were no doubt vents for the many flows. In the higher country or near the volcanic vents, the lava, while still hot and liquid, was mixed with water, giving it enough mobility to travel downhill as a slurpy mud. Rain, snow, lakes, and rivers were the source of water. Sometimes the lava flowed in the stream channel itself, mingling with stream water to make a steaming brown paste (fig. 47). In some places, mudflows dammed the stream channels, forcing the water to take other routes to the sea. The mudflows poured down the mountain slopes as jumbled masses of large rocks and small, of boulders of granite and metamorphic rocks, of torn and shattered trees, mixing and churning, coming to rest when they had stiffened too much to move farther or had reached the bottom of the slope. Landscapes that developed on the mudflows have a chaotic aspect. Travelers through Sierran passes drive through andesitic terrain, sparsely populated with bushes and gray pine (Pinus sabiniana), for mile on mile. One particularly striking outcrop is at Carson Spur on State Hwy. 88. Here the mudflow remains are perched above a branch of the American River, which runs hundreds of feet below through granite. Ages of weathering have worn the face of the cliff back, carving the volcanic rock into battlements and towers that resemble a derelict fortress. The andesitic mass is sometimes called “andesitic breccia,” a term indicating that the rock has been broken apart. Why it should be broken is not entirely clear: perhaps the over-anddownhill tumble shattered it, perhaps internal pressure that built up within it caused it to break apart, or perhaps both. In the course of 15 million years, a lot of andesitic lava poured over the northern half of the Sierra. More than 12,000 sq mi (31,000 sq km) of land surface was covered, for a total volume of more than 2,000 cu mi (8,000 cu km) of new rock!

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Figure 47. Stages in the creation of Tuolumne (Stanislaus) Table Mountain.

Top left: The Tertiary Stanislaus River flowed through moderately rolling hills, flanked by subtropical vegetation. Top right: Steaming lava has followed the easiest course downhill—the bed of the river. It has filled, but not overflowed, the river valley. Bottom: This is the Tertiary Stanislaus River course as it appears today near Knights Ferry. The lava flow, being much harder than the surrounding hills, still marks the course of the ancient river. The softer rock of the enclosing hills has been eroded away, leaving a high, sinuous ridge where once there was a river valley.

Long Valley Volcanoes By the time the cold of the Great Ice Age began to settle in, the andesitic eruptions had quieted. But on the eastern side of the Sierra, volcanic fire as well as ice changed the landscape. Near the Long Valley area between 3.6 and 2.3 million years ago, volcanic

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Plate 51. View of Panum Crater as you ascend the domes. Scattered along the tuff rim are rounded “accidental” pebbles, derived from the gravel layer that the little volcano was built on. Panum is the most easily accessible of the craters.

vents and domes spewed out lava. San Joaquin Mountain and Two Teats are erosional remnants of large domes of this time. By the time the Ice Age was beginning, about two million years ago, early acts in the story of Long Valley were on stage. From vents near 11,000 ft high (3,350 m high) Glass Mountain, a series of domes and flows, surrounded by fans of volcanic block flows and ash beds as much as 3,000 ft (1,000 m) thick, testifies today to eruptions that lasted about a million years. Then, about three-quarters of a million years ago, the roof over a magma chamber in Long Valley ruptured, and about 150 cu mi (625 cu km) of incandescent ash and molten rock blasted out, which is about 2,500 times the amount blown out by Mount St. Helens in its eruption of May 18, 1980. It was a “rain of fire”: red-hot, incandescent lava particles fell from the sky—rhyolitic ash that covered and erased the existing hills and canyons. The eruption partially emptied the magma chamber and caused its roof to collapse and the chamber to sink in on itself, forming a caldera, now an oval depression 10 by 20 mi (17 by 32 km). The incandescent particles — ash and pumice— that were shot out covered 580 sq mi (1,500 sq km) of the surrounding countryside and piled up more than 600 ft (200 m) thick. Near the volcano,

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the fragments were probably expelled as a “glowing avalanche” (nuée ardente)—a roaring, flashing cloud that can travel a hundred miles an hour, sweeping over the landscape, obliterating trees and shrubs, and immolating luckless animals in its path. The ash deposits, called Bishop Tuff (fig. 48), within Long Valley Caldera are more than 4,500 ft (1,400 m) thick. The ash settled to perhaps half its original thickness as it welded and compacted. The tiny glass fragments of which it was made fused together as it cooled. Similar tuff from Hawaii, when magnified many thousands of times, resembles children’s jacks (fig. 49); no doubt the Sierra tuff did, also, before it was crushed together by its own weight. Today, three-quarters of a million years later, after the sheet has cooled and eroded, an air view still shows a remarkably even table land, cut through by a few nowdry rivers. Close inspection of the tuff shows that it contains pumice fragments and pieces of rock. The pumice no doubt was blown through the air from the volcano, but because the rock fragments resemble the bedrock beneath, they must have been picked up as the dense cloud rolled over the terrain. In the twentieth century, the Valley of 10,000 Smokes in Alaska has had such an avalanche, but no one was there to see it. Also in the twentieth century, in 1902, Mount Pelé, on Martinique in the West Indies, erupted. Although it had been giving premonitory rumblings, with ashes falling in the streets and horses suffocating in their tracks, the signs were not heeded by many for various personal and political reasons. Suddenly, at 7:50 a.m. on May 8, the volcano exploded with four deafening blasts. A nuée ardente sped down upon the city of St. Pierre, leaving but two persons alive—one a murderer awaiting execution, protected in his dungeon from the death that came to others. All of the houses in St. Pierre were destroyed. Thirty thousand people lay dead within minutes. The dull red cloud, pierced with brighter red streaks as larger incandescent rocks were tossed about in its billows, raced to the sea, where it sent up clouds of steam two miles high. Truly, in such an eruption, the volcano looks as if it were on fire. But it is not burning in the sense that it “burns up” objects, except for trees that the cascading lava may encounter. The red fiery color is even more frightening than fire: it is the color of rock heated to incandescence, to a temperature not even approached in furnaces or fireplaces when wood or coal is burned. The tem-

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Figure 48. Simplified geologic map of Long Valley Caldera. A cataclysmic eruption 760,000 years ago ejected flows of hot glowing ash, which cooled to form Bishop Tuff and Long Valley Caldera. Wind-blown ash from that ancient eruption covered most of the West (inset map).

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Figure 49. Fragments of volcanic ash, magnified many thousands of times.

perature of the explosive ash flows from Long Valley Caldera has been calculated at 1,500 degrees F (800 degrees C). The tiny, glowing glassy fragments welded together as they cooled, settling to perhaps half their original thickness as they compacted. Clouds of fine ash from the Long Valley eruption drifted with the wind, going as far as Nebraska, southern California, and the Pacific Ocean. Not all the ash was expelled in one huge belch. Incandescent ash flows followed one after another, sometimes so quickly and traveling so fast that later ones overtook earlier ones. Today these ash flows are beautifully exposed in the Owens River Gorge and on the Volcanic Tableland, as well as in road cuts along the highway. Off and on, eruptions continued. About 100,000 years after the collapse, a dome rose up in the center of the collapsed caldera. The lava accompanying the dome was glassy, cooling into obsidian, an important natural resource for Native Americans (pl. 52). While the dome was rising, the caldera filled with rainwater, making the large crater lake called Long Valley Lake. It was still icy in the Sierra, and glaciers flowed into the lake, breaking off icebergs that had on their backs rocks from thousands of feet above in the high country. When the bergs melted, the rocks were left far away from home on the flanks of the dome. Long Valley

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Plate 52. Close-up of obsidian, Panum Crater. Obsidian, Native Americans’ favorite raw material for arrowheads and other tools, is common in the Craters. Obsidian is volcanic glass, formed when fluid rock was quenched so quickly that crystals did not have time to develop. Three of the largest “craters” are actually obsidian flows called “coulees.” The coulees are young, dating from 630 and 700 years ago, and thick, 200 to 300 ft (60 to 90 m). They are one to two miles long, counting their vents. Since this is rhyolitic obsidian (despite its color), the flows are unusual because they have flowed so far, as most rhyolitic material is too stiff to move with speed or to great distances.

Lake stood until its water spilled over the caldera’s southwestern rim, rushing out to cut the Owens River Gorge into the Volcanic Tableland. Eventually, the waters cut a deep enough gash that the lake drained. A thousand centuries followed, while the volcano lay silent and the caldera stood like a mediaeval castle, complete with moat. But the volcano was merely quiet, not dead. About half a million years ago light-colored rhyolite began erupting in the moat and kept on erupting off and on for 400,000 years. While this was going on, other volcanoes in the Coso and Big Pine volcanic fields to the south erupted, leaving tidy little cinder cones that look as if they were made just yesterday. As if Big Pine and Long Valley were not enough, another volcanic center north of the caldera began to stir. The new vents, a

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Figure 50. Block diagram showing volcanic landscape features. Magma, or molten rock, rises to the surface and into the overlying sedimentary rock along planes of weakness. Within the Earth, it forms dikes and related igneous bodies; that part that poured out upon the surface creates various volcanic land forms. Among the landforms are volcanoes (left). From a vent on the opposite side of the volcano, a lava flow has spread out over the land. Lava plateaus and lava mesas are in the background; ash cones, cinder cones, and volcanic domes are in the middle ground. All have their source in the magma chamber beneath. The magma chamber itself may eventually solidify completely. When unroofed of its overlying volcanic and sedimentary rock, the solidified magma chamber probably would be a coarse-grained igneous rock, possibly a diorite or granite.

chain about 28 mi (45 km) long, extend from Mammoth Mountain to Mono Lake. We do not know whether they are tapping the same underground source as the caldera or not. About 300,000 years ago, basaltic lava poured from vents near the western moat of the caldera. It filled the moat to a depth of 800 ft (250 m), surged around the dome, and sent long tongues within the moat. Other basaltic vents in the chain erupted farther north near June Lake between 20,000 and 40,000 years ago, and at Black Point on the shore of Mono Lake about 13,000 years ago.

Mammoth Mountain Rises About 220,000 years ago, Mammoth Mountain (pl. 53) began to build, pushing its way up as a sticky mass. At least 12 domes and

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flows of light-colored lava constructed the imposing volcano that today straddles the caldera rim. New flows came up through the old ones to pour out over the sides, forming thick, stubby glass lumps. At least one flow was fluid enough to run two miles beyond the base of the mountains; however, most merely stacked another layer on top of the older ones. But the Mammoth volcano is not simply layer after layer of lava, like icing on a cake. Several times explosions blew holes in it, and at other times, ash and pumice poured out of vents. Glaciers have cut into the mountains, and streams are beginning to slice it, but there is life still in the old cone. A heap of volcanic rocks as large as this takes a long time to cool. Even though Mammoth Mountain has been erupting and cooling for a quar-

Plate 53. Mammoth Mountain, on the east slope of the Sierra Nevada. Mammoth is a large volcano on the Long Valley Caldera rim. It was active mainly between 220,000 and 50,000 years ago, although steam still rises from fumaroles along the flanks and from a vent on the northeast face, indicating that the volcano is not dead yet. The eruptions during its most active phase threw out andesite and rhyolite, as well as layers of scoria, pumice, and tuff. After the 1980 earthquake series, the water temperature as well as the flow from the fumaroles increased. The earthquakes were related to movement of magma under the ground. After 1989, carbon dioxide began to escape from the magma (see pl. 62), killing trees on the mountainside.

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ter of a million years, it has fumaroles that occasionally show steam, especially in the cold winter air, testifying to banked, not dead, volcanic fires.

Devils Postpile Southwest of Long Valley Caldera, molten basalt flowed downstream from a vent not far away, forming a pool of lava, probably ponded behind a glacial moraine. The exact date of this is not yet known, but it probably happened less than 100,000 years ago. The lava was very fluid and cooled slowly, first along the bottom where it encountered cool granite and at the top where it was exposed to air. Because it cooled from the top and bottom inward, the interior remained molten for some time. As it cooled, it shrank, causing stresses in the newly formed rock mass that were relieved by cracking, forming the basalt columns that are now the main feature of the 800-acre Devils Postpile National Monument. Basalt is a dark, fine-grained rock. Its minerals are so minute as to be hidden to the naked eye, even to the eye aided by a hand lens. Yet this rock has protean surprises: when it cools, it can resemble a black sponge, which is deceptive for it is far from soft; it can form an intensely hard wall; it can take the form of rounded pillows; it can be spun into rounded or spindle-shaped “bombs”; it can even appear to be a stony organ, with angular pipes rising upward half a hundred feet (pl. 54). No one knows how big the original flow was, but judging by the regularity of the columns and other evidence, it was 400 ft (120 m) or more thick, and probably much larger than it is today, as lava probably filled the San Joaquin River valley from side to side. Individual columns are as much as 60 ft (18 m) long. The largest columns in the Postpile are a little over 3.5 ft (1 m) in diameter, but the average is about 2 ft (.6 m) Very few other flows in the world approach the Postpile in geometric regularity (pls. 54–57). Ideally, in a cooling mass, the pattern of the cracks that initiate the columns is six sided. This is the most efficient structural form, as the honeybee knows, and where chemical and physical conditions are uniform, six-sided shapes predominate. But it is rare to find conditions uniform in nature. A geologist who has studied columnar structures has tried to discover how uniform the conditions were by measuring the percentage of six-

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Plate 54. The stony “organ” at Devils Postpile National Monument. Less than a hundred thousand years ago, the lava that formed this spectacular columnar basalt flow poured out of vents north of Pumice Flat and flowed down the Middle Fork of the San Joaquin River about 2.5 mi (4 km) until it confronted an obstacle—perhaps a glacial moraine—which caused it to form a 400-ft-deep (120-m-deep) pond. Because the lava was uniform, with almost no gas, it cooled slowly and evenly, allowing regular, six-sided cooling joints to form. Such joints form perpendicular to the cooling surface, and because the lava pond lay in a river valley, the flow was thinner along the sides, so that the columns along the sides curve toward the edge of the valley, giving the “organ” a rakish look.

Plate 55. Close-up of postpiles, showing rough hexagonal structure.

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Plate 56. Postpiles, standing behind iron supports to prevent them from breaking into fragments, as many already have. The earthquakes of 1980 and after shook down several columns, including three tall leaning ones that, although they were separated from their fellows at the top by as much as a foot, had withstood other shakes and many years of freezing and thawing.

sided columns. The Postpile ranked very high in his study. Its columns ranged from three sided to eight sided; the ratios are shown in fig. 51. Another person counting found 55 percent sixsided columns. Compare these figures with statistics from other well-known columns: Giant’s Causeway, Northern Ireland, sixsided columns, 51 percent; Devil’s Tower, Wyoming, 32.5 percent; Craters of the Moon, Idaho, 16 percent. Three-Sided Four-Sided Five-Sided Six-Sided Seven-Sided Eight-Sided

.5% 9.4% 36.9% 43.8% 9.1% .25%

Figure 51. Disposition of Postpile column forms.

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2 columns 38 columns 150 columns 178 columns 37 columns 1 column

Plate 57. Stubby ends of postpiles.

Plate 58. Top of the main postpile, showing the geometric structure of the piles.

The angles at which the sides of the columns meet also give clues to their cooling history. In piles with straight sides, like the Postpile, the angles tend to be close to 120 degrees; piles with more 90-degree angles tend to have curved faces. The piles, as you might expect, formed perpendicular to the bottom and top of the lava flow. Probably the part near, but not on, the bottom of the flow was the best place for uniform cracks to start. Where the ground surface was uneven, the piles were bent. From below, the Postpile looks like a gigantic organ; from

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above, glaciers have worn and polished the mosaic to a parquetlike surface (pl. 58). And the Postpile continues to change. Three columns that had been leaning outward since 1909 collapsed during the 1980 earthquakes, and other columns cracked.

Mono Craters A whole string of volcanic domes known as Mono Craters, south of Mono Lake, stand 9,000 ft (2,700 m) above sea level, yet are dwarfed by the Sierra west of them (pl. 59). The 10.5-mi-long (17-km-long) string of light gray rhyolite obsidian (volcanic glass) and pumice domes range in age from 1,300 to 60,000 years. Those at the southern end are oldest, dating from about 35,000 years ago; the youngest, Panum Crater, erupted between a.d. 1345 and 1445, about the time the Aztecs were founding Ten-

Plate 59. Mono Craters, near Mono Lake. Some of the 30 or so craters rise above the lake 2,000 ft (600 m), and a few have craters in the top. In any setting other than in the shadow of the High Sierra, the Craters would be considered sizeable mountains. Craters in the chain commenced erupting about 40,000 years ago, and it is possible that eruptions could continue today. The Craters form an 8-mi-long (13-km-long) arc from the south shore of Mono Lake south to the Devils Punch Bowl. The arc is the eastern margin of a 12-mi-wide (19-km-wide) ring fracture system that has subsided more than 600 ft (180 m) in 800,000 years. A magma chamber probably lies below the craters at a depth of 4 to 6 mi (6 to 10 km). Mono Craters includes three large obsidian flows, six rhyolite domes, several explosion craters, the islands in Mono Lake, and the Black Point lava flow.

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ochtitlán in the Valley of Mexico and not long before Columbus made his way to the Americas.

Inyo Craters The southern end of the chain consists of a line of domes and craters, the Inyo Craters, that expelled light-colored rhyolitic lava. Two of them, Wilson Butte and North Deadman Creek Dome, poured out lava so similar to the lava of Mono Craters that it is probable they tapped the same underground source. Geologically speaking, the Inyo Craters and the two domes are about the same age as Mono Craters: Wilson Butte is 1,350 years old, and North Deadman Creek dome is a bit older at 6,000 years. Other domes within the Inyo chain all erupted within a few years—perhaps even a few months—of one another, all in the late fourteenth and fifteenth centuries: trees felled by the eruption give dates of a.d. 1369, 1433, and 1469, about the time Panum Crater erupted. It may be that the two younger Inyo domes erupted lava from the source of magma of both Long Valley Caldera and Mono Craters. About this same time, three craters blasted out of the top and side of Deer Mountain, a rhyolite dome south of Deadman Creek. The craters are often filled with rainwater and are known as Inyo Crater Lakes (pl. 60). Cinder cones burst forth from Mono Lake itself, forming brooding Negit Island. Paoha, the other large island in the lake, is itself a light-colored rhyolite dome that pushed up from the lake bottom, probably sometime between 1720 and 1850, and is now covered by lake sediments. Recent bathymetric surveys show islands and basins on the lake floor. Near Negit, hummocks on the bottom look like submarine lava flows that escaped from Negit or from underlake sources. Oddly enough, there are freshwater springs in the depths of the bitter alkaline lake. When will the next eruption be? No one can say, but scientists are constantly monitoring for danger signals.

Long Valley Is Still Alive It is probable that at least one hot magma body still lies beneath Long Valley Caldera. The most recent eruptions are so new that it

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Figure 52. How an obsidian dome develops. Top, A low cone has formed by explosions of pumice. Middle, A volcanic dome rises in the center of the cone, pushing upward. Bottom, The dome has risen so high that part of it has pushed over the crater rim as a short, thick flow called a coulee. Blocks of obsidian dot the coulee and flow.

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Plate 60. Inyo Crater Lake. South of Mono Craters, another 6-mi-long (10-km-long) chain of craters, domes, and flows extends from Obsidian Dome south to Mammoth Mountain. Known as the Inyo Craters, the chain contains some of the youngest volcanic features in the Sierra Nevada. Three craters are in the small group that includes this lake. They formed about 600 years ago, when groundwater encountered magma and turned to steam, causing explosions—but not volcanic eruptions—that blew out the craters. The lake is about 200 ft (60 m) deep and 600 ft (180 m) in diameter, giving it a wine-glass shape.

is likely the body has not yet cooled. In addition, a bulge of the ground surface of at least 24 in. (60 cm) since 1980, the spasmodic seismic bursts of 1980 through 1983, and a peculiar seismographic pattern thought to indicate the movement of hot fluids through fractures are geophysical data pointing to a hot body down below. In 1982, persistent earthquake swarms—thousands of tiny earthquakes—in the Long Valley area and the con-

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Plate 61. Steam vents and hot springs in Long Valley show that there is still heat underground.

tinued upward bulge of the caldera floor made geologists think that an eruption was possible. The U.S. Geological Survey issued a “potential volcanic hazard” notice. Besides uplift and earthquakes, a dormant fumarole at Casa Diablo Hot Springs sprang to life, and new hot springs broke out on the southern edge of the dome (pl. 61). The possibility of eruption was particularly worrisome, as the town of Mammoth Lakes is built in the caldera. By 1984, when no volcanic eruption had taken place, the hazard notice was rescinded. Geophysicists who studied these unnerving events concluded that magma was being squeezed into fissures beneath Mammoth Mountain, but that it congealed before reaching the surface. In 1990 trees near Horseshoe Lake at the base of the mountain mysteriously began to turn brown. It was not drought, disease, or insects causing the problem. Geologists solved the mystery when they discovered carbon dioxide (CO2) seeping through the soil, killing the trees (pl. 62). By 1996, trees scattered around the mountain were dead, in a total area covering more than 150 acres (60 ha). Geochemists who analyzed the gas came to the conclusion that it was derived from magma. Apparently, large amounts of gas were trapped beneath the surface until released by magma rising along a new fault fracture in the underlying rock. Those who study volcanoes use an array of geophysical and other techniques to try to predict eruptions. It is possible that volcanoes may have regular cycles, but even Vesuvius, for which there are good records for more than 1,000 years, shows no clear pattern. If a volcano does erupt, a few things can be done to protect people and property. Some lava flows can be bombed, some di-

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Plate 62. Sign warning of potential danger of carbon dioxide. Carbon dioxide, escaping from magma beneath the surface along a new fault in the underlying rock, has killed more than 150 acres (60 ha) of trees on the slopes of Mammoth Mountain and at Horseshoe Lake. During photosynthesis, trees produce oxygen from carbon dioxide, but their roots need oxygen directly, and the large amount of carbon dioxide was denying it to them. Where the trees have died, carbon dioxide makes up 20 to 95 percent of the gas in the soil; less than 1 percent is normal. When carbon dioxide leaves the soil, it mixes with air and is no longer a danger to the tree, but because carbon dioxide is heavier than air, it can collect in low places. For humans and other animals, breathing air containing more than 30 percent carbon dioxide can cause unconsciousness and even death. Carbon dioxide is a common constituent of magma. According to measurements by the U.S. Geological Survey, Mammoth Mountain is producing 1,200 tons of carbon dioxide per day, about what Mount St. Helens produced during low-level volcanic activity.

verted, and some dammed. Lahars—mudflows—can be avoided if their paths are known. But nothing, absolutely nothing, can yet be done in a nuée ardente, except to heed early warning signs of eruption and flee. If an eruption of the magnitude of the Long Valley event of three-quarters of a million years ago, or of the 1912 eruption of Katmai, Alaska, were to take place in populous California, the disaster would be incalculable. In historical perspective, though, our astonishing luck has, so far, kept us in the U. S. from counting volcanic eruptions as major disasters. They are far, far behind wars, automobile accidents, hurricanes, floods, and earthquakes.

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CHAPTER 10 DAYS OF ICE

Overleaf: Ice-cold pool in the Sierra Nevada.

IN THE WORLDWIDE Great Ice Age that ended a few thousand years ago, glaciers pushed their way across Canada and much of eastern North America. In the West, they covered the northern parts of Washington, Idaho, and Montana. The Rocky Mountains, the Sierra Nevada, and the Cascades had, by then, become high enough barriers that the sheets did not cross them; but these ranges were also high enough and cold enough to accumulate glaciers of their own. These mountain glaciers of the West, although they existed at the same time as the great continental ice sheets to the north and east, were wholly independent of them. Nevertheless, when glaciation reached its maximum, the High Sierra must have been white both winter and summer, for the “firn line” — the line marking permanent ice—covered most of the high country, leaving only ridges and peaks projecting above it. These mountain islands, rising from a bath of ice, were frozen, barren deserts. Because of the intense winter cold, the bitter winds whipped the summits more wildly than today, removing snow from high peaks such as Whitney as fast as it fell. Below, in the canyons to the west, the snow fell thick and deep. “It is hard,” wrote John Muir, “to realize the magnitude of the work done on these mountains during the last glacial period by glaciers, which are only streams of closely compacted snowcrystals. . . . In the development [of these mountains] Nature chose for a tool . . . the tender snowflowers noiselessly falling through unnumbered centuries, the offspring of the sun and sea.”

Birth of a Glacier How the delicate, elaborate snowflake becomes the grinding blue ice of glaciers is a story in metamorphism that affords us a glimpse into this little-understood geologic process. Ice differs from most other metamorphic rocks in that it is, whenever pure, wholly made of one material. In addition, it is transformed from one physical state to another at temperatures and pressures that are very close to those of Earth’s surface. Most other minerals are transformed one into the other under conditions of high pressure or high temperature, which are difficult to

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duplicate in the laboratory, or through such long periods of time that we do not live to witness the transformation. Snowflakes, on the other hand, can be altered while we watch. First they change to tiny spheres, which become connected by minute necks that form where the spheres touch one another. Water vapor from the tiny balls migrates from the surface of the balls to the necks to form larger and larger necks, until the entire mass is sealed together. All of this takes place below the melting point, so that water is not necessarily present during the change; of course, if the temperature rises above freezing, so as to melt some of the snow, the liquid water speeds the process. As it melds together, the snow-ice mass increases in weight and strength. Fresh snowflakes have a density of no more than a quarter of a gram per cubic centimeter, about a tenth the weight of water. Within weeks, they become powder snow, about twice as dense and twice as strong; in months, they are old snow, doubling again in weight and strength; in years, they become “firn”—the material of which glaciers are made. In hundreds of years, they have consolidated into glacial ice, nine-tenths as heavy as water and a form of rock. During this process, they have increased in weight nine times and in strength 500 times. They have changed in shape from dainty snow filigrees to dense crystals of glacial ice as long as 10 in. (25 cm). Unless an entire continent is glaciated, as much of the Northern Hemisphere was in the Pleistocene glacial epoch, and Antarctica is today, glaciers are born in mountains. They abide not so much at high latitudes (although that is where most of today’s glaciers are) as at high altitudes, and where the climate is wet and

Plate 63. Granite peaks sculptured by frost action.

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cold. The bodies of rock ice that form in mountains start in mountain valleys, where the snow drifts most thickly. For this reason, “mountain glaciers” are also called “valley glaciers,” as it is in the mountain valleys that they form, grow, and move, remodeling their birthplace as they do so. Even though ice is a form of water, it is an environment quite different from one that is wholly liquid water. Ice, of course, is colder; polar ice can be very cold indeed. ProbaPlate 64. Deadman Creek, path of a bly, the mountain glaciers long-gone glacier. of California were not as cold as the continental ice sheets but rather were “temperate” glaciers, far closer to the melting point than the larger sheets. In temperate glaciers, part of the ice itself may melt, so that water may run throughout the ice, pouring out of the edges of the glacier. The glacier acts as a kettle to hold the cold rivers and lakes that are within it. While the ice remains as a barrier, water is not always free to flow down the lowest or easiest path but must skirt obstructions in the ice, creep through tunnels in the sheet, or melt the ice ahead as it flows. On the other hand, if the temperature grows colder, water in the ice may freeze, changing the texture and strength of the ice body that holds it. Like water, ice follows the easiest course—downhill—but if an ice stream meets an obstruction, such as a hard rock barrier, the ice can ride over it as a sheet (pl. 64). Water, which is not as cohesive as ice, must form a lake behind the obstruction until it can overtop the dam. As a stream of water is commonly deepest in the center and thinnest at the edges, so a glacier is thickest in the center. But, unlike water, the ice stream is usually bowed upward in the middle rather than being nearly flat. For this reason, water on the surface

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of the glacier runs toward the sides as well as toward the general downhill slope, carrying with it pieces of rock and sand from the surface of the glacier.

How Glaciers Move Unlike rivers, most of which enter other bodies of water — last of all the sea—glaciers come to an abrupt end. The ice stream is more like a lake than a river in that it has geographic limits: a definite beginning and a definite end. Rivers rise from large, undefined, irregular areas where the rains fall, and water collects bit by bit into a recognizable stream; mountain glaciers head in teardrop-shaped basins, and their limits are well marked. Both ice and water streams move downhill in response to the pull of gravity. Water moves at a quick rate of many feet per second, but solid ice must temper its flow to inches per day. Nonetheless, glaciers can occasionally move much faster than

Plate 65. Erratics on glacially polished granitic outcrop near Lake Tenaya, Yosemite National Park. “Strangers in the landscape,” erratics are fragments of rock that are out of place, many miles from where they originated. They dropped onto the glacier and took a long ride downhill. When the ice melted, they were left on top of the bedrock, far from home.

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that. One Alaskan glacier in the twentieth century surged at a clocked rate of 300 ft (90 m) per day, and a Russian glacier moved so fast in 1963 that a village at its foot had to be evacuated. Not all of a glacier’s movement is the result of melting and refreezing. Glaciers can move as solids, by plastic flow, each molecule gliding across its neighbor as the giant ice sheet shuffles along. This sort of movement takes place when the ice reaches a thickness of 100 to 150 ft (30 to 45 m). The ability of the glacier to move as a solid and to use tools as it moves makes it a unique agent of erosion. When it melts, it leaves behind sculptures of pristine beauty. The tools it uses are simple: rocks and water. By freezing to the enclosing rock, the glacier can pluck — quarry— huge blocks, particularly in such highly jointed areas as the granitic reaches of the Sierra Nevada. Using these stones as teeth in immense files, the ice body can scrape the sides and bottom of its basin. It gathers any loose rock or blocks not held firmly in place as it moves along, using the accumulation as a ball mill not only to grind the rocks in the mill, but to scour out the valley itself. Smaller fragments of rock suspended in the ice or in the water within the ice act as sandpaper to polish the sides and bottom of the valley. The sand itself may be ground to powder (glacial flour) as it moves with the ice.

Cirques When a glacier has melted from its valley home, many evidences are left of its former passage. The valley has been transformed from the sharp-pointed, V shape that it had when only a mountain stream ran through it, to a more gentle U shape, reflecting the form of the now-gone ice. At its head, an amphitheater will be left— a “cirque” — in which the only remnant of the glacier may be an ice-cold lake. In shape, this uphill glacier head (oddly enough, the terminal, downhill end of a glacier is called its “snout”) is somewhat like a tablespoon. It is generally deeper at the upper end than the lower, which is, of course, the reason why a lake is likely to remain there. The head wall above is very steep, but at the lip of the spoon there is often a ridge of bedrock, heaps of broken rock, or a mixture of rock and ice. The Sierra’s largest existing glacier, the Palisade near Bishop, has a heap of stones and

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Plate 66. Dana glacier, glacier canyon, and glacial lake on the boundary of Yosemite National Park.

Plate 67. Mount Izaak Walton. Mount Izaak Walton is a horn, with a ridge (arête) connecting it to a nearby mountain, and a cirque occupied by snow. Horns are three-sided pointed peaks left when cirques, which once held glaciers, nearly converge. One geologist, seeing the ridges and intervening erosional patches made by the vanished ice, called it “biscuit board” topography. The patches, now covered by snow, are where the “biscuits” have been removed, leaving the ridges, like biscuit dough next to where the biscuit was cut out, remaining.

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ice forming a block at the end of the cirque. There are a hundred or so tiny glaciers in the Sierra today, almost all, including the Palisade, cirque glaciers, living wholly within basins carved by the giant valley glaciers of the Great Ice Age.

Cirque Glaciers Cirques are carved by active, dynamic glaciers. They are all fairly symmetrical, no matter what their orientation or what kind of rock they are carved in. They may be deeper and wider if the rock

Plate 68. Mount Lyell, with its glacier on its side. A prominent bergschrund is near the upper end of the glacier. Lyell, having a surface area of a quarter of a square mile, is the Sierra’s second largest glacier. In 1933, hikers were surprised to see the mummified body of a furless mountain sheep upright on an ice pedestal on Lyell glacier. The Yosemite region had not had mountain sheep for 50 years. Park Naturalist M. E. Beatty, one of the discoverers, wrote that his group measured the rate of movement of the glacier and found that it moved an inch (2 cm) in four days, or seven and a half feet (2.29 m) per year. If the sheep was feeding on the top of the mountain and fell into the crevasse, assuming the rate to be reasonably constant, it would have taken the glacier 250 years to have carried the corpse of the sheep to the spot where it was found. Searching farther, the group found a mummified hairless marmot, as well as a cony.

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HOW MANY GLACIERS? LET ME COUNT THEM ALL

o one who has seen Alaska would doubt that it has glaciers.Thousands. But in the Sierra Nevada? I once took a friend up to see the Palisade glacier, the largest in the Sierra and about half a square mile (1.3 sq km) in size.“You call this a glacier?” she scoffed. If the Palisade isn’t a glacier, what is? It has crevasses, moraines, rock debris, and a bergschrund. In the warm days before the first winter snows fall, the snout of the glacier may melt a little, allowing a view of hard glacial ice carrying dirt and rock debris.What’s more, it flows— moves downhill under its own weight—at an average rate of a little less than an inch a day. Larger snow fields dot the Sierra, and some that last for years may turn into glaciers, but until then they are simply perennial snow fields. Shortly after the first edition of this book was published, Bill Raub of San Jose State University showed me a then-unpublished count he and three others were making of Sierran glaciers. Here is the definition they used in making their foot and aerial count (now published, Raub et al.

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is soluble or is easily broken or already weathered, but their outlines are the same. Because wind drift has a great deal to do with snow accumulation, cirque glaciers tend to form on the lee slopes of mountains. In most areas in the Northern Hemisphere, this means that northeast-facing slopes are favored. Palisade glacier hangs in such a niche, but a study of Sierran topography to locate cirques of the glaciers of the Great Ice Age would probably reveal many more cirques west of the main divide than east of it. They are there simply because more snow fell on the western side. The more symmetrical, larger ones are, nevertheless, those that lay longest in the shadow of the peaks rather than facing the heat of the summer sun. The head wall — that part of the cirque that provides the most spectacular scenery—can stand thousands of feet high in resistant, jointed rocks such as Sierran granite, while softer, less “competent” rocks crumble. Walcott cirque, near McMurdo Sound in the Antarctic, has a head wall nearly two miles high; Mount Everest has one almost that high. The 1,500-ft-high (450-m-high) east face of Long’s Peak, Rocky Mountain National Park, looks

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1980, 33–34): “Glaciers” were defined as “ice masses having a bergschrund or crevasses; visible snow firn or ice of different years; and/or moraines.” Nothing was said about movement, a common ingredient in most glacier definitions. Using this definition as their guide, they painstakingly tallied 497 glaciers and 847 ice patches in the Sierra.That is a great deal more than this book’s first edition gave: “about 70.” As they counted them, the glaciers ranged in elevation from 9,082 ft (2,769 m) to 11,621 ft (3,543 m).The smallest in the Raub count is only about 25 acres (.1 sq km), a very tiny glacier, but large enough for a good-sized ice-skating rink. Bill Guyton, writing in Glaciers of California (1998), subtracted from the Raub total of 497 glaciers a group he called “glacierets”—tiny masses of ice less than .25 mi (400 m) in any dimension.This left him with 99 glaciers and 398 glacierets in the Sierra Nevada—a reasonable sum. So, the Sierra Nevada has a lot of glaciers, all of them small. If you are looking for the giants of the Great Ice Age, you will have to be content with their spoor.

down on Chasm Lake, a tiny glacial tarn, resting in the cirque of an Ice Age glacier. Most cirque glaciers have a crack around the ice—a “bergschrund”—parallel to the head wall. Palisade glacier and the Mount Dana, Mount Conness, and Mount Lyell (pls. 68, 69) glaciers all have well-developed ones. Just what the relationship of these cracks is to the erosive power of the glacier is not clear. In 1904, geologist W. D. Johnson descended the bergschrund on

Plate 69. Lyell glacier bergschrund.

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Mount Lyell to its bottom, 150 ft (45 m) below. There he found the rock wall exposed and discovered that in the last twenty or thirty feet, rock replaced ice in the up-canyon wall. The schrund opened to the cliff foot. I cannot say that the floor there was of sound rock, or that it was level; but there was a floor to stand upon, and not a steeply inclined talus. It was somewhat cumbered with blocks, both of ice and of rock; and I was at the disadvantage, for close observation, of having to clamber over these, with a candle, in a dripping rain, but there seemed to be definitely presented a line of glacier base, removed from five to ten feet from the foot of what was here a literally vertical cliff. The glacier side of the crevasse presented the more clearly defined wall. The rock face, though hard and undecayed, was much riven, its fracture planes outlining sharply angular masses in all stages of displacement and dislodgment. Several blocks were tipped forward and rested against the opposite wall of ice; others, quite removed across the gap, were incorporated in the glacier mass at its base. Icicles of great size, and stalagmitic masses, were abundant; the fallen blocks in large part were icesheeted; and open seams in the cliff face held films of this clear ice. Melting was everywhere in progress, and the films or thin plates in the seams were easily removable. (1904, 574)

Ice Streams Like rivers of water, glaciers coalesce to form larger ice streams. Unlike water, ice may fill its canyon to great depths and yet come to an abrupt end. Sierran ice was as much as 4,000 ft (1,220 m) thick in some valleys at its greatest extent, and the entire ice cap was more than 100 mi (160 km) long and 40 mi (65 km) wide. Longest of the glaciers, the Tuolumne, was fully 60 mi (97 km), but it terminated 30 mi (48 km) from the foot of the range, at an elevation of about 2,000 ft (600 m). Where the ice was thick, small tributary glaciers in high mountain valleys met the main trunk at an altitude nearly that of the top of the ice sheet. While the ice was in the valley, an air view of the glacier would have looked like a wide sheet with branches. Now that the ice has melted, the difference in elevation between

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PALISADE GLACIER

alisade glacier (pl. 70) may look like a temporary snowfield, but it is a true glacier, with crevasses, moraines, and a bergschrund. Late in the summer, when snow in the mountains has largely melted, the snow covering the Palisade glacier melts, too, and you can see hard glacier ice beneath. In 1977, a drought year, the glacier sported a moulin, a vertical hole in the ice that water flows into, the water reappearing at the snout of the glacier.

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Plate 70. Palisade glacier.

Although the Palisade glacier is tiny by Alaskan standards—it has only .5 sq mi (2.6 sq km) of surface area—it is the largest in the Sierra Nevada. It lies in a cirque on the northeast flank of North Palisade Peak at an elevation between 12,000 and 13,400 ft (3,700 and 4,100 m) and is sometimes called North Palisade glacier. Palisade is a modern glacier, created in the Little Ice Age some 700 years ago, and like most true glaciers, it moves. Scientists have measured its rate of flow as a maximum of 23 ft (7 m) per year, or less than an inch a day. Between 1940 and 1980, Palisade glacier shrank a great deal. Another Sierran glacier, called Black Mountain glacier by Muir when he found it in 1871, had disappeared by 1977. (Black Mountain is now called Merced Peak.) Even Palisade could disappear if the Earth’s warming trend continues. For now, travelers along U.S. Hwy. 395 can still see the glacier from a distance. It is about 14 mi (23 km) southwest of Big Pine.

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Plate 71. Yosemite Falls. Yosemite National Park is famed for its waterfalls, especially for Yosemite Falls. Yosemite Falls plunges over two cliffs and through cascades for a total of 2,425 ft (740 m), making it second highest in the world, exceeded only by Angel Falls, Venezuela. The upper part of Yosemite Falls, which races through a chute worn in the granitic cliff, clears the rock in a high 1,430-ft (436-m) leap. The steep cliff over which Yosemite Falls plunges is controlled by two sets of widely spaced joints, one nearly vertical, trending west; the other nearly horizontal. The cliff is made of light gray El Capitan granite and younger, dark gray Sentinel granodiorite.

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the trunk bottoms and tributary bottoms is striking. The base of the tributary glacier was, in some places, more than a thousand feet higher than the base of the main trunk. Where a stream, now flowing in the glacially altered tributary, meets the main trunk, it drops breathtakingly to the main valley floor. Yosemite Falls (pl. 71), leaping in three sections over a 1,430-ft-high (436-m-high) precipice through a raceway 815 ft (248 m) high, to a final 320-ft (998-m) plunge to the floor of Yosemite Valley, for a total of 2,565 ft (782 m), is such a “hanging” waterfall. So is Ribbon Falls, 1,612 ft (491 m) high, not all in free fall; and Bridalveil, which plunges from a cliff 620 ft (189 m) high. In little-visited Hetch Hetchy Valley, Tueeulala Falls drops about 1,000 ft (300 m), of which 600 ft (180 m) is in free fall. Most of the Great Ice Age mountain glaciers in the Sierra Nevada followed the courses of streams that had flowed in canyons before the great cold settled over them. The ice itself changed the high-mountain portions of the stream valleys, and its meltwater altered the lower reaches. By the time the Ice Age chill arrived, the distribution of land and sea was close to that of today. The Sierra Nevada had become a rocky backbone; the Coast Ranges were separated from the Sierra by the Great Valley, no longer an inland sea. Because a great deal of water was locked up in ice during those times, the general level of the sea all over the world was lowered by about 300 ft (90 m). On the western side of the Sierra, glaciers extended down the river valleys as much as 15 mi (25 km), quite a distance from the mountain source but still a long way inland. None of the Sierran glaciers were close enough to the sea to enter the ocean directly, as polar glaciers do today. For this reason, and because the Coast Ranges were not ice covered, California does not have fjords as the Scandinavian countries, Canada, and Alaska do. Few of the glaciers on the eastern side of the Sierra extended beyond the mountain front. Those that did left remarkable evidence of their passing. Around Mono Lake, a shrunken remnant of one of a chain of Ice Age lakes, now-vanished glaciers left ridges of rubble more than 800 ft (245 m) high. In any setting other than between Mono Craters, at 9,000 ft (2,700 m), and the crest of the High Sierra, the ridges themselves would be regarded as mountains.

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Glaciers Tailor the Land The ice made astonishing alterations in its valley— not so much in its lengthwise appearance, where the only noticeable change was to straighten curves slightly so as to make it easier for the ice to turn, but in the cross-sectional shape, where it sculptured the valley from a V shape to a U shape. The U-shaped valley is a scenic wonder: the sharp, straight edges provide steep cliffs; the sudden drop permits spectacular waterfalls; the flattened bottom gives room for quiet lakes and marshes (pl. 72). The world’s most renowned example of such a valley is Yosemite. Its twin, Hetch Hetchy, was once equally remarkable. Today, its glory is hidden. It is occupied by a lake that is the source of some of the water for San Francisco. Yosemite’s valley has been called “nature’s textbook on glacial erosion,” for here you can see what ice, which at times filled the valley from rim to rim, can do.

Plate 72. Hikers in the Sierran high country are often relieved to see a broad valley amid the steep granitic peaks. Most high mountain stream valleys have a V shape, with the stream running in the apex of the V. In broad valleys like this one, however, the stream meanders through a flat area. Only the part where the water actually runs has a V shape. The stream does not seem to fit its valley. The reason is that the valley has undergone change since the stream flowed through it in ages past. The original V shape was filed into a U shape by the glaciers. Yosemite Valley is a world-famous example of a U-shaped valley, reshaped by glaciers in the Great Ice Age. The Merced River flows through it, as its ancestor did before the glaciers arrived.

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Plates 73, 74. Lembert Dome in Tuolumne Meadows, Yosemite National Park. Lembert is a roche moutonnée that lay in the path of the Tioga glacier, the last great glacier to top large portions of the Sierra Nevada. The stoss (downstream) side was smoothed; the lee (up-glacier) side plucked, giving the dome a teardrop shape. Although the rock mass appears smoothed by the ice, closer up (inset) climbers can easily find handholds, thanks to erosion since the Great Ice Age.

If you stand at Glacier Point and look toward Little Yosemite Valley, you can see how the valley has been cleared and reshaped. One stream of ice came from the east; it was joined by another from Tenaya Canyon just below Glacier Point. Together they created the Yosemite we see today. As the glacier moved slowly but relentlessly past Half Dome, it cleaned the dome face, carrying away pieces of granitic rock broken off along joint planes to leave a clean, steep precipice. At Glacier Point, the valley was completely filled with ice, as were the shallower side canyons feeding into it. When the ice melted, the side canyons were left stranded high above Yosemite Valley. The streams in them leap over the lip of the valley in spectacular waterfalls. In the uplands near Tuolumne Meadows, the glaciers were not confined to narrow river canyons but spread themselves out over broad reaches. Here you can see the work of “glacial moulins,” or glacial mills, which are round holes formed by glacial waterfalls and eddies armed with scouring rocks. Here, too,

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Plate 75. Close-up of chatter marks in granitic rock, Crystal Basin. Chatter marks are indentations in the bedrock made by the pressure of the glacier. Similar marks are made by humans in the process of producing an arrowhead.

you can see roches moutonnées, which are rounded rocks left on a deserted glacial floor. The uphill side of these rocks rises smoothly and gradually, while the downhill, lee glacial side is more irregular, steep, and plucked. As you can see, the direction of ice motion can be deduced from these rocks. Liberty Cap and Mount Broderick, at the mouth of Little Yosemite Valley, are two enormous roches moutonnées. They stood directly in the path of the glaciers and were overridden by them, yet they survived, each as a massive, unsubdued giant. Another roche moutonnée is 500ft-tall (152-m-tall) Lembert Dome, in Tuolumne Meadows (pls. 73, 74). The Tuolumne glacier flowed over the dome, amputating about half of the original rock. The other Yosemite domes are not roches moutonnées, as they were not overridden by ice; but the passing ice altered their shape, smoothing, polishing, and streamlining the upstream side and quarrying and steepening the downstream side. Fairview Dome and Pothole Dome, too, were well polished by ice; some of the polish has worn away, but the many remaining patches gleam in the afternoon sun.

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Other small, telltale clues to the passing glaciers are scattered through the high mountains. There are “chatter” marks, crescent-shaped gouges made by ice pressure, similar to the marks on an arrowhead fashioned by steady pressure on hard rock (pl. 75). More revealing than many larger features, these tiny tokens point to the direction of ice movement. A particularly good set is at the foot of Mount Huxley, south of Yosemite in Evolution Basin. Scratches, gouges, grooves, and other erosive indignities (pl. 76) to the rock of the valley are not the only souvenirs of the vanished glaciers. The glacier adds to the landscape, as well as subtracting from it (fig. 53). Most of what it adds is the material it has torn or worn from its enclosing valley, broken into bits and carried to a new resting place. Sometimes large boulders ride down the valley in or on the glacier. When the ice melts, they find themselves a great distance from the outcrop that was their source, perhaps left high and iceless on a ridge. Such boulders are called “erratics” because they are strangers in the landscape. One may be a boulder of metamorphic rock standing like a monument in a field of granite; another may be a granite monolith marooned in

Plate 76. Glacial polish and glacial striations on granitic rock near Lake Tenaya. The bedrock is polished when a glacier slides over it. Dust that has fallen into the glacier and migrated to the bottom forms a thin layer of mud that acts as polishing rouge under the enormous pressure of the ice. Glacial striations, too, are formed at the bottom and sides of the ice, but the tools that produced them are gravel and boulders in the ice.

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Figure 53. How glaciers sculpt the landscape. Top, Mountain landscape before glaciation. Middle, Landscape during glaciation. Bottom, Landscape after the glaciers have melted.

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Plate 77. Till near Convict Lake. Large and small rocks, clay and sand make up glacial till, of which moraines are made. Till forms from rock fragments that fall onto a glacier from surrounding cliffs, fall into the bergschrund, or are “plucked” by freezing and thawing from the bed of the glacier. The till eventually moved downstream to the terminus of the glacier, where it formed an end moraine. Till that had piled up along the sides of the glacier and had not been carried down when the glacier melted formed a lateral moraine, the till stranded on the bottom formed a ground moraine when the glacier melted.

metamorphic terrane. There are many such out-of-place boulders in the Sierra Nevada. As the ice moves forward, it pushes small and large rocks ahead of it much as a snowplow pushes snow, to form a rocky ridge called a “moraine.” Some of the material the ice can actually plow up, but most rides along on top, beneath, or within the ice until it reaches the glacier’s snout, where it joins other material being washed and pushed ahead of the glacier (pl. 77). Rock and dust of various sizes find their way to the sides, too, to form other moraines. These, like the moraine at the snout, are a mixture of large rocks and small in no particular beds or arrangement. Moraine is the French word for “hill” or “rubble heap,”indicating the unsorted arrangement of rock material in it. In the United States, the Scottish word till is used to refer to the rocky debris of which the moraine is made. The weather helps the glacier to break up the rock of the

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mountains. In the course of freezing and thawing 300 times, 10 tons of dust may be derived from five acres of granite mountainside by the breaking up of minerals in the rock. All of this, together with rock debris from avalanches, rock slides, falling boulders, and the like, drop onto the glacier to become part of the glacial moraines.

Crevasses In many glaciers, the ice surface is thoroughly scored by crevasses. Crevasses may be less than an inch or more than 50 ft (15 m) wide. They may be a few feet to hundreds of feet long, and as much as 150 ft (45 m) deep. They form where the glacier is under stress: where it turns a corner; where the central ice is traveling faster than the ice on the edge; where there are knobs in the floor of the valley. Rocks and dust fall into each of these cracks, to make their way through the ice as the glacier moves. When the glacier melts, the rock material that is still in the crevasses—that has not yet made its way downward— is left as an unsorted ridge on the valley floor, forming winding lines among the scattered boulders dropped from the ice. Glacial streams flow over the surface, along the bottom, and within the ice. They run through definite tunnels, rather than as a sheet along the bottom. Those in the tunnels within the ice form a pattern like the branches of a great tree, pulling water in toward a downhill trunk. When the confining ice collapses, the debris in the streambed, like that in the crevasses, is dropped to the drying valley floor. Former glacial streambeds make sinuous ridges that mark the old stream courses. They are the reverse of streambeds on land: the ice that supported them has vanished, so the sand and gravel once in the water are now left elevated. When a stream on land dries, the material in its bed is below the surface of the land, for the land itself, not ice, was the container.

The Glacial Dance: Advance, Retreat Despite their vastness and unrelenting erosive power, glaciers are quite sensitive. Born of climatic change, glaciers reflect the slight-

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TABLE 12

Glaciations of the Sierra Nevada

Matthes (Little Ice Age) Recess Peak Tioga Tahoe Sherwin McGee

About A.D. 1250 to 1900 About 14,000 to 15,000 years ago About 19,000 to 26,000 years ago About 70,000 to 150,000 years ago About 1 million years ago About 1.5 million years ago

Modified from Bill Guyton, Glaciers of California (1998).

est alteration in climate. When more snow falls in the winters than melts in the summers, a glacier may begin to form and to grow, pushing moraines ahead of it as it advances, traveling downhill both by growth and by movement of the ice particles. If the climate warms or the snows decrease, the glacier may have insufficient nourishment to maintain its great size. Melting faster than it is being added to, the glacier is said to “retreat,” leaving heaps of rocky debris behind it. It may abandon its end — terminal — moraine, as well as a series of “recessional” moraines that mark resting places in the general ebb. The last ice age in North America and Europe was marked by several advances and retreats of the enormous ice sheets. These have been clocked by a number of methods, but just how their timetable matches that of the Sierran valley glaciers is not yet completely known. Study of the advances and retreats of the mountain ice cap glaciers of the Sierra Nevada has shown that several advances, called “glaciations,” have taken place since the beginning of the Pleistocene’s Great Ice Age (table 12). Because many of the moraines that are the clues to the various ice advances, retreats, and hesitations may be mixed together in one area, or else are so separated from one another that it is not easy to see exactly how the moraines match from one valley to another, reading the story of the Great Ice Age in the Sierra requires the delicate unraveling of many morainal strands. The strands have not yet been completely untangled. It is rare that the age of a moraine can be measured directly. Once in a while, a splinter of wood caught in a younger moraine may be found, and the age of the wood calculated by carbon-14

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Plate 78. Glacial moraines near Laurel and Sherwin Canyons.

methods. This gives the time when the wood was buried and is a useful method for determining the age of moraines less than 40,000 years old. More circumstantial evidence must be used to decipher most of the record. The weathering of rocks in the various moraines is one criterion used. So is the development of soil—a tool that is helpful in deciphering the story of continental glaciation — but soil is scarce on most Sierran glacial deposits. As an added complication, both the depth of weathering and the amount of soil are greater on the western side of the mountains than on the eastern, as there is much more moisture the western side to aggravate weathering and contribute to the production of soil. Lava flows and faulting are also clues to the age of glaciation. For example, glacial debris lies on top of lava flows near Bishop. The flows have been dated by radiometric methods as 3.2 million years old. Because the glacial till lies above, it must therefore be less than 3.2 million years of age. Above the till, in turn, is an outcrop of the 760,000-year-old nuée ardente deposit from the Long Valley eruption. At this place, at least, we can say that this particular glacial till is more than 760,000 and less than 3.2 million years old. By tracing the till to other outcrops, it might be possible to estimate its true age more accurately. In some places, moraines have acted as barriers to lava flows,

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impounding or diverting them. Clearly, then, the till would have been in place before the lava. On the other hand, a lava flow or a volcano can be too high to be overridden by ice or covered by moraine; there is no doubt in such a case that the ice was younger than the volcano. Volcanic ash is proving to be another valuable asset in reading the story of the past “few” years of the Sierra Nevada. In Tuolumne Meadows, Yosemite, for example, searchers found a lump of charcoal in an ash bed which proved, by carbon-14 methods, to be about 1,550 years old. Because it is possible to measure the rate at which soil is accumulating on top of the ash, and because geologists have determined the age of the ash, it is possible to guess quite accurately when vegetation first began to grow in the meadow. Another indication of by-gone climates and, by inference, of glacial advances and retreats, is the fluctuation in the elevation of timberline. In the White Mountains, east of the Sierra proper, timberline in years past was determined by mapping, tree ring counts, and carbon-14 methods. The record correlates very nicely with glacial advances and retreats, thereby giving us still another check on the antiquity of past glaciers. The story of the Great Ice Age in the Sierra, as it now reads from such clues, shows that the Sierra harbored glaciers more than 1.5 million years ago (the McGee glaciation). After that, glaciers advanced about one million years ago (the Sherwin glaciation), again about 150,000 to 70,000 years ago (the Tahoe glaciation), about 26,000 to 19,000 years ago (the Tioga glaciation), and about 15,000 to 14,000 years ago (the Recess Peak glaciation). Glacial moraines are well developed on the eastern side of the Sierra, where they form low, voluptuous ridges most easily seen in the orange light of sunset. Little Walker Lake, above Mono Lake, is enclosed by moraines left by glaciers of four different glacial advances. Here, the moraines are fresh enough that you can almost see the cold, vanished giants that made them. Many moraines are visible from U.S. Hwy. 395 between Reno and Lone Pine and can be followed into the canyons from which they came. Moraines can be seen on Mount Rose, Nevada; around Lake Tahoe (Fallen Leaf Lake was formed by a morainal dam); near Bridgeport; along Lee Vining Creek, in Gibbs Canyon; and in Mammoth, Sherwin, Laurel, Convict, Rock, McGee, Hilton, Pine, and other canyons as far south as Olancha Peak.

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In some places, if you are aware of the techniques for distinguishing older moraines and know where to look, you can see those that are more than 100,000 years old (in Gibbs Canyon, for example); but for the most part, the moraines that are most visible are the long, trailing ridges of the Tahoe-Tioga glaciers (150,000 to 19,000 years ago). The mountain glaciers melted a few thousand years after that, and the continental ice sheets vanished. But we are not finished with glaciation. In the last 10,000 years, since the end of the Ice Age, the climate has cooled enough three times for small glaciers to form. Yosemite geologist François Matthes called the latest of these the “Little Ice Age,” the last spurt of which now bears his name in honor of the work he did in deciphering the story of the Sierran landscape. The story of the Little Ice Age is complex. From a time of glaciation lasting from about 8500 b.c. to 7000 b.c. (10,500 to 9,000 years before present), the climate gradually warmed to the “climatic optimum” (altithermal), a period of warmth that lasted through most of the days of Ancient Egypt to about 600 b.c. Then, as Greek and Roman civilization waxed and waned, the Earth grew colder, up to about the time of Christ, when warming commenced again. Had Hannibal been born a few centuries later, in an interglacial time, his elephants might easily have walked over the snowless Alpine passes. Rome, not Carthage, might have been forever destroyed. Warmer times continued up to a.d. 1300. The northern seas were free of ice. About 985, Eric the Red and a band of Norsemen founded colonies in Greenland that grew large and prosperous. From one of them, Leif the Lucky, Eric’s son, set forth on an expedition that led him to the American continent, landing in about the year 1000. In the twelfth century, nearly 5,000 colonists lived on Greenland, working 280 farms. Then the drab, cold days set in. Permafrost rose in the ground, freezing seeds and making even the digging of a grave for the dying impossible. Ice filled the harbor. Cattle died, and even wolves could find no food. Fog, wind, and torrential freezing rain swept the fated colony. In the gray mists that swirled over the whitening land, the last survivor perished. The colony had come to a virtual end in 1410, when the last ship left. The history of Eric the Red and his colony passed, like Pompeii, into legend, a victim of changing geology. Two hundred years later, as the cold was reaching its maximum, the Pilgrims

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TABLE 13

Some Existing Glaciers in the Sierra Nevada

Glacier (elevation of lower and upper margins in feet [meters] above sea level)

Location

Sawtooth Ridge (many) 10,600 to 11,200 (3230 to 3414)

Yosemite National Park, Matterhorn Peak quadrangle

Mount Conness (several) 11,000 to 12,000 (3353 to 3658)

Yosemite National Park, Tuolumne Meadows quadrangle

Mount Dana 11,200 to 12,300 (3414 to 3949)

Yosemite National Park, Mono Craters quadrangle

Kuna Crest (several) 11,400 to 12,600 (3475 to 3841)

Yosemite National Park, Mono Craters quadrangle

Mount Lyell (several) 11,500 to 12,800 (3505 to 3901)

Yosemite National Park, Merced Peak and Tuolumne Meadows quadrangles

Ritter Range (many) 10,500 to 12,200 (3200 to 3719)

Devils Postpile quadrangle

Mount Abbot (several) 12,000 to 13,000 (3658 to 3962)

Mount Abbot quadrangle

Mount Humphreys (several) 11,400 to 12,800 (3475 to 3901)

Mount Tom quadrangle

Glacier Divide (many) 11,400 to 13,000 (3475 to 3962)

Mount Goddard and Blackcap Mountain quadrangles

Mount Goddard (many) 11,400 to 12,800 (3475 to 3901)

Mount Goddard quadrangle

The Palisades (many; some large) 11,200 to 13,000 (3414 to 3962)

Big Pine and Mount Goddard quadrangles

came to North America. Small wonder that they gave heartfelt thanks for having lived through that first bitter, glacial winter. Little Ice Age alpine glaciers were at their height from about 1700 to 1750. Most of California’s present glacierets were as large and strong then as they ever were (table 13). They are not descen-

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Figure 54. Sheeting surface along the High Sierra Trail. This surface has been glaciated and severed, as evidenced by the light-colored band (dike) whose continuity is broken. The view is north toward Eagle Scout Peak.

dants of the Great Ice Age glaciers of 20,000 years ago but are new, infant glaciers that look small and out of place in the cirques carved by their powerful predecessors. From 1750 to about 1850, the climate warmed again, melting part of the small glaciers. Then once more it cooled, and the tiny glaciers grew a little larger. In 1883, for example, there was a glacieret in Gibbs Canyon, where only a minute patch of ice remains today. From the turn of the twentieth century until the 1960s, glaciers melted rapidly. Many small ones still hang in the cirques of the high country, or lie hidden beneath a protective rock covering. Moraines in the Sierra Nevada dam hundreds of lakes and lakelets. Besides these moraine-dammed lakes, hollows in the rock surface over which the glacier flowed also now contain lakelets called “glacial tarns.” The many glacial lakes of both types make the landscape look from a distance as if a jeweled chain had broken, scattering diamonds (fig. 55). And, they are cold. Besides the tiny alpine ice glaciers, the Sierra has many “rock glaciers,” mostly tracing their origin to the recent cold period. These are not true ice glaciers, because they are not composed principally of ice. They are made of broken rock, mixed with ice, but they move downhill as a wrinkled mass, much as a true glacier does.

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Figure 55. Three lakelets left as testimony of a former glacier. Lakes like these are called glacial step lakes, or, because they resemble beads on a rosary, paternoster lakes. The three shown here may be seen toward the south from the top of Black Rock Pass, in the Mineral King quadrangle, Tulare County. They show very distinctly the effects of altitude on temperature: the highest lake, Columbine, is still frozen and is connected to the next lake by a frozen waterfall. Below it, in the center of the drawing, is Cyclamen Lake, still frozen on its upper edges, but thawing toward the lower edge. It is connected to Spring Lake, the lowest, by a flowing waterfall. Ripples on Spring Lake show that it has completely melted. Step lakes are common in mountainous regions that have been sculptured by valley glaciers. Because the treads of the steps hold water and ice longer, they are more deeply eroded than the risers, gradually creating a lake basin.

Who Left the Door Open? Why did the Earth grow cold? Although the Great Ice Age was not the only period of glacial cold in the Earth’s four-billion-yearlong history, there were very few, if any, like it. More than 50 ideas as to why glaciers should cover so much of the Earth have been suggested, none of which has been wholly satisfactory. At least three astronomical cycles influence the amount of heat the Earth

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gets. One is a change in the Earth’s axis with respect to its plane of revolution (a cycle of 41,000 years), another is the degree of the elliptic of the Earth’s orbit around the Sun (a 95,800-year cycle), and a third is the precession of the equinoxes (the time of year the Northern Hemisphere is most tilted toward the Sun (a 21,700-year cycle). Each changes the amount of heat the Earth gets; when they act in concert, they can produce exceptional cooling or warming. Now that research vessels have recovered cores from ocean sediments dating back through the last ice age, the record, which gives information about the climate, has been compared with astronomical cycles, and they agree closely. So astronomical changes can cause climate change and influence the behavior of glaciers. But the correlation is not perfect. Probably some geologic events modify the direct cause-and-effect relationship. One such event could be the uplift of mountain ranges by plate movement, pushing the mountains upward high enough to increase the snowfall markedly. This plate movement could also trigger volcanic eruptions that would throw ash into the atmosphere, where it could remain for years, decreasing the amount of solar radiation reaching the Earth. Volcanic eruptions large enough to alter world climate have been known historically, such as the eruption of Krakatau in 1883, which caused a “year of no summer.” Prehistoric eruptions were even larger. One at Long Valley in eastern California at the foot of the Sierra Nevada 760,000 years ago and another at Valles Caldera, New Mexico, only a million years ago, and not far from the Sierra Nevada, were surely larger than Krakatau. So astronomical and geologic events together could cool the Earth enough for glaciers to form. Geologist Bill Guyton, author of Glaciers of California, offers this possible scenario: Suppose that at some particular time the astronomical circumstance is appropriate for a small cooling, but insufficient to cause a glaciation. A large volcanic eruption occurring at that time might augment the astronomical cooling enough so that glaciers begin to form. Once formed, glaciers reflect much sunlight back to space and influence weather in such a way as to tend to perpetuate themselves. The result is a major glaciation that neither the astronomical situation nor the volcanic eruption alone could

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cause. An identical volcanic eruption at a time when the astronomical circumstance called for warming would not be capable of causing a glacial advance. According to this line of reasoning, no single event, astronomical or geologic, will correlate with the glacier record perfectly. (1998, 16)

Whatever the driving force that pushed the continental glaciers over mountain ridges and formed ice caps where none are today, it was powerful. When it ceased, the glaciers waned, much of the ice sealed up in the ice caps melted, and the sea rose, filling the sea basins a little beyond their brims, separating lands that once were connected. While Asia and America were connected, people crossed to the New World through the Siberian land bridge. Some American horses, camels, tapirs, and zebras left the New World for Asia, while those that remained behind quickly became extinct. By the time the people of the New and Old Worlds were once again aware of each other’s existence, all memory of American horses, camels, and zebras had vanished, although the Americas had been their birthplace. Will the Earth cool again? Perhaps. We cannot now predict what nature will do. But we can guess what man can do. If the cloud cover, today about 31 percent of the Earth’s surface, were to be increased to 36 percent, it has been estimated that the average temperature would drop 7 degrees F, enough, according to some students of glaciation, to trigger a new ice advance. We are now fully capable of making such a change in the cloud cover, whether we intend to or not, and new glacial advance could mean worldwide catastrophe.

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CHAPTER 11 MONO LAKE: THE “DEAD SEA” OF THE WEST

Overleaf: Tufa towers on Mono Lake. Nowhere but in Mono Lake will you see these fantastic, other-worldly structures. Other drying lakes in the West—Searles and Pyramid, for example—have tufa, but tufa as pavements and domes, not pillars and towers and spires. The towers are composed of the mineral thinolite, a form of calcium carbonate. The peculiar chemistry of the lake, with an abundance of carbonates and sulfates, provides the raw material. Springs, rising through the lake waters, heated by the not-yet-dead volcanic fires beneath, provide the shape. In a way, the tufa towers are fossilized springs. High and dry on the surrounding hills are remnants of tufa towers that mark where Great Ice Age springs bubbled up through a much larger Mono Lake. Tufa is forming today in the depths of the lake at a rate of a few millimeters a year. If you put the tufa under a microscope, you may see tiny algal cells. Some scientists think that algae aided in the formation of tufa by altering the chemical equilibrium; if they did, they gave their lives for it, as they are now encased in stone. Tufa grows also in the briny sands of the lake itself. As calcium-rich groundwater wells up through the sand, it forms delicate, tufa-cemented sand tubes, sometimes within hours or days.

MONO LAKE IS one of the world’s most remarkable lakes. It is not a former lake or a prehistoric lake that no longer exists, or a “dead sea”; it is a living lake, very elderly, but living. It is a lake that has been present for at least 760,000 years without drying up. But it is in danger now. Few American lakes attain such longevity. Lake Tahoe, like Mono, is one of the few. The Great Lakes, although dating from the Great Ice Age, are comparative youngsters at only 13,000 years old, while Crater Lake, Oregon, filled with water in the crater of a volcano only some 7,000 years ago. Great Salt Lake, a contemporary of Mono, has dried many times. Mono Lake is 13 mi (21 km) long by 8 mi (13 km) wide. From a high vantage point, such as from U.S. Hwy. 395 to the north, it often appears steely gray, glassy, and quiet, but storms often worry the lake into high waves dangerous to small boats.

Mono Basin Mono Lake lies in a deep basin created by warping of the Earth’s crust and faults along the Sierran front. The basin has slipped over 11,000 ft (3,353 m) below the Sierran crest, measuring down to granitic bedrock, but erosion has cast more than 4,000 ft (1,200 m) of sediments into it. During the Great Ice Age, the basin was filled to the brim with water, 400 ft (120 m) above its present level, making a vast lake some 28 mi (45 km) long and 18 mi (29 km) wide. The lake overflowed southward. At that time, the lake was over 900 ft (270 m) deep. At the time of the Little Ice Age, around 500 years ago, Mono Lake suddenly rose to a level at least 50 ft (16 m) higher than at present. In recent years, the lake level has fluctuated, largely because of Los Angeles’s diversion of the water that sustained it. The Mono Basin has much to offer a geologist.Volcanoes, glacial deposits, and faults, as well as the ancient lake itself, were all present and operating at the same time. Because of this wealth of geologic processes and features, the Mono Basin has been one of the most studied parts of the Sierra Nevada. In 1950, William C. Putnam studied the old shorelines and moraines at Mono Lake and came to an unexpected conclusion: the lake stood highest about the same time the glaciers were

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largest. When the glaciers withdrew, the lake shrank. Common sense said that as the glaciers melted, the lake—and other pluvial lakes in the desert West—would grow when the ice reached its greatest extent and began to melt, but that was not true. The maximum height (and therefore depth) of the lake was reached 12,000 to 14,000 years ago, several thousand years after the ice reached its farthest. Why should this be? One explanation is that the increase in temperature at the end of the Great Ice Age was not accompanied by a decrease in precipitation. The humorist Mark Twain spent a week’s vacation at Mono Lake in the 1860s. He was not impressed with the scenery: Mono Lake lies in a lifeless, hideous desert, eight thousand feet above the level of the sea [the shoreline elevation is 6,362], and is guarded by mountains two [six] thousand feet higher, whose summits are always clothed in clouds. This solemn, silent, sailless sea— this lonely tenant of the loneliest spot on earth — is little graced with the picturesque. . . . Half a dozen little mountain brooks flow into Mono Lake, but not a stream of any kind flows out of it. It neither rises nor falls, apparently, and what it does with its surplus water is a dark and bloody mystery. (Twain 1913, 175)

Tastes change. Most of us today would find it wildly picturesque.

Mono’s Water Mono has no surplus water, especially now that Los Angeles has taken most of the fresh water that once flowed into it. Even though the steams that flow into it are “fresh,” they carry salts with them in solution, as all streams do. The waters of the lake evaporate, but the salts do not, making the lake more and more salty and alkaline, and giving the water a slippery feel. Through the centuries Mono has achieved a saltiness three times as great as the ocean and 80 times as alkaline. Mono contains about 280 million tons of dissolved salts — mostly sodium chloride (table salt), but also including sodium carbonates (often called washing soda) and sodium sulfates, as well as borate and potassium, making it 1,000 times as salty as Lake Tahoe. “Its sluggish waters,” Twain wrote, “are so strong with alkali that if you only dip the most hopelessly soiled garment into them once or twice, and wringing it out, it will be found as clean as if it had been through the ablest of washerwomen’s hands” (1913, 175). 324

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Tufa Towers Mono’s unusual chemistry has been responsible also for the curious and, yes, picturesque “tufa domes” or “tufa towers” scattered about the lake (pl. 79). These odd features, resembling Daliesque wedding cakes or ice-cream cones, rise from the waters, but along the shore the falling water level has left some of them stranded on land. Some writers have described them as “giant towers of cemented cauliflower,” “white columns and elaborate façades, like those of the ruined temples of Greece,” and “sciencefiction art . . . the cities of some intelligent and artistic extraterrestrial termite” (Gaines 1989, 26). The late David Gaines, author of Mono Lake Guidebook, wrote, “Marooned on shore by receding waters, they seem like the bones of the shrinking lake” (1989, 26). As Mono’s waters fall, the towers appear taller and taller as they project above the lake level. The tufa towers are made of the mineral thinolite, which is calcium carbonate (limestone). They were the sites of underwater thermal springs. Some cannot be seen at all, as their tops are below lake level. When geologist Israel C. Russell studied Mono in the nineteenth century, he found one spring still pouring out of the top of a three-foot-high tower, building its tower farther upward in the air. This spring no longer exists, having dried up because of Mono’s receding waters. As water bubbles through

Plate 79. A tufa arch at sunrise on Mono Lake.

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Mono’s brine and sand, the calcium in the spring water combines with carbonates in the lake to form tufa (not to be confused with tuff, which is consolidated volcanic ash). Other saline lakes in the desert West have tufa deposits also— Searles and Pyramid, for example—but none have towers. As the chemical-laden water burbles upward through the lake’s sand, it forms sand tubes and columns as well, sometimes within a day. Mono was one of a chain of lakes in wetter Ice Age times that derived their water from glaciers in the mountains. Indeed, much of the western United States was under water in various places that are now desert. The lakes and connecting waterways at one time formed a complex chain that carried water away from Mono via Owens Valley, Indian Wells Valley (China Lake), Searles Basin, Panamint Valley, and finally, Death Valley. Mono is one of the few ancient lakes that still contains water year round. At Mono, it is possible to correlate former shorelines with the advance and retreat of the glaciers, as water-cut terraces in moraines of Ice Age time are now hundreds of feet above the lake. One of the highest terraces is at an altitude of about 7,070 ft (2,155 m). More conspicuous than these terrace levels, which are to be seen on the Sierran mountains above Mono, are the “bathtub rings” surrounding the lake itself. They mark the lowering of the lake as its water is diverted to Los Angeles. Construction of the aqueduct to carry water to Los Angeles was an engineering marvel and an ecological disaster. But the engineers who built the aqueduct did not see it that way. They saw, like Mark Twain, a worthless “dead” sea. They were, they thought, doing a magnificent thing, a favor to civilization. To serve the “greatest good for the greatest number” they destroyed lakes and ruined farms, ranches, and towns. Owens Lake, south of Mono, was once a wide expanse of water that even boasted a steamboat, the Bessie Brady, that carried silver ore from the eastern mountains to smelters. Today the lake is totally dry, and instead of supporting wildlife it supports dangerous alkali dust storms visible from space. Mono contains two islands, Paoha and Negit, both named by Israel C. Russell, Mono’s most dedicated student. Negit is the Paiute word for “goose” (or, more likely, “gull”); paoha, Russell noted, are “diminutive spirits, having long, wavy hair, that are sometimes seen in the vapor wreaths ascending from hot springs” (1889). Negit is the black island; Paoha is the white one. Both are geologically very young. Negit was formed in several dif-

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MONO LAKE, 1982

Plate 80. Mono Lake, 1982.

ountains of the Sierra Nevada to the west provide a stunning backdrop for Mono Lake, with Negit Island visible in it.Although the lake has an average depth of only 50 ft (15 m), no other natural lake wholly within California (Tahoe is partly in Nevada) holds more water.The lake is roughly bathtub shaped, so it is no surprise to see “bathtub rings” surrounding it.The rings are chemical salts precipitated out of the water as the lake level falls as water is taken from the streams that would normally keep it full. Mono holds about 280 million tons of dissolved salts, or about three-quarters of a pound per gallon (90 grams per liter). Most of the salts are sodium salts: sodium chloride (table salt), sodium carbonate (baking soda), and sodium and magnesium sulfate (Epsom salts). Mono also is rich in borate and potassium. In the background is Black Point, a low, basaltic hill that lies on Mono Lake’s northwestern shore. Black Point is a volcano that erupted about 13,000 years ago, in the Great Ice Age.At that time, Mono Lake was 900 ft (270 m) deeper than today, so that Black Point erupted below the surface of the lake.The weight of hundreds of feet of water above the underwater volcano flattened it. Black Point has fissures— some as deep as 80 ft (24 m) and as narrow as 4 or 5 ft (1.2 or 1.5 m) across—that may be cooling fissures.

M

ferent volcanic episodes from 1,700 to 300 years ago but looks as if it were created just yesterday (pl. 81). Paoha rose from the lake in the middle of the seventeenth century. It is weathered and gullied, making it into badlands and giving it an unwarranted aspect of great age (pl. 82). It is white rather than black because its surface consists of lake-bottom sediments deposited through centuries and lifted above the water by the up-

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Plate 81. Negit Island in Mono Lake is a volcano. It erupted about 1,600 years ago, and as lately as 270 years ago. An important breeding ground for migratory birds, Negit was truly an island and therefore safe from four-legged predators until the diversion of Mono’s waters to a southern California aqueduct allowed a land bridge to form, and coyotes and others attacked the birds and their eggs. The land bridge is, however, being inundated following a recent court order, which required that some water be restored to Mono Lake.

ward push of rising volcanic flows. Only at the northern and southern ends are there visible lava flows, cinder cones, and steam vents to betray the role of volcanoes in its creation. Their eruption probably raised the lake level 5 to 8 ft (1.5 to 2.5 m). At some point, one of Paoha’s volcanoes blew a hole in its top, which is now occupied by a perfect little heart-shaped crater lake. Black Point, now on Mono’s shore, erupted underwater some 13,500 years ago during the Great Ice Age, its summit cracking as it cooled. Ebbing waters of the lake gradually exposed the volcano to view, presenting a rare on-land glimpse of an underwater volcano. Because Mono’s volcanic fires are not yet completely quenched, two deep wells were drilled to prospect for geothermal power. The first was spudded on the southern shore of the lake on September 13, 1971, and drilled directionally under the lake, where hot springs take their origin. Although the drillers found temperatures of 115 degrees F (46 degrees C) at the bottom of the well,

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Plate 82. Paoha Island, in Mono Lake. Paoha, like its sister, Negit, is a volcano, but although it did not have the strength to fully erupt above ground, it made the effort about 250 years ago. The white covering on the island’s surface is lake-bottom sediment, pushed up from the depths of the lake by the incipient, but unsuccessful, volcanic eruption. A few small lava flows on the northern end, as well as steam vents and fumaroles on the island, show it may simply be biding its time. The Long Valley eruption of 760,000 years ago was very recent (geologically speaking), but Bishop Tuff, which the eruption formed, was found in a drill hole 1,400 feet under Paoha, showing how lately the Mono Craters have been busy. Black Point, Negit, and Paoha are all part of the Mono Craters chain.

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4,056 ft (1,326 m) deep, the temperature and the geothermal gradient (the rate at which Earth gets hotter approaching the center) were considered normal for the area. Air temperature on a hot day on U.S. Hwy. 395, which runs past Mono, can reach near 115 degrees F, without having to drill holes in the ground. The second well, drilled a month later on the northwestern side of the lake, encountered bedrock at 1,740 ft (530 m) and was abandoned at 2,437 ft (743 m). Even though the Mono Basin has many clues suggesting it would be a good geothermal area, such as recent volcanism, boiling hot springs and steam vents on Paoha Island, and thermal springs as hot as 150 degrees F (65 degrees C), these tests did not prove the basin’s potential for geothermal power.

Mono’s Life Although Mono is unusual in many ways, the name does not mean “single” or “alone” as you might suspect if the word derived from Greek. Instead, it comes from the Yokut language, from a word meaning “fly people” or “alkali fly,” referring to the brine fly (Ephydra hians), whose larvae were a staple in the Mono tribe’s diet. The dried larvae were not only a food stuff for the Monos; they were a trading commodity. The Monos called themselves “kutsavi eaters”—kutsavi being their word for brine fly larvae. Twain may have thought the lake “lifeless,” but he was wrong. True, it has no fish, no seals, no crabs, even very little grass. In 1940, the California Fish and Game agency attempted to plant trout, but the poor things went belly up. “The fisherman who casts his worm-baited line into the briny water soon reels in—a dead worm,” wrote David Gaines (1989, 39). Mark Twain and his companion, who visited Paoha Island on a calm morning, were surprised by a sudden storm and quickly made for their shoreside camp, fearing the while that their boat would capsize in the billows and they “would be eaten up so quickly [by alkali waters] that we could not even be present at our own inquest” (Twain 1913, 181). But life is here in abundance. At least 900,000 birds come to feed or nest during the year. As many as 750,000 Eared Grebes (Podiceps nigricollis) come in October, following the Eastern Sierra Flyway. July brings upward of 80,000 Wilson’s Phalaropes

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(Phalaropus tricolor), and August 65,000 Red-necked Phalaropes (P. lobatus). This provides a lake full of birds, without even counting the California Gulls (Larus californicus), who come from April through July to nest on the islands. It was California Gulls, possibly from Mono Lake, that saved the pioneer Mormon farmers at Great Salt Lake by eating the invading locusts. The birds depend on animals that live in the water, particularly the brine fly and brine shrimp (Artemia monica). Brine flies and their larvae are so abundant that as William H. Brewer of the California Geological Survey observed in July of 1863: The number and quantity of these worms and flies is absolutely incredible. They drift up in heaps along the shore—hundreds of bushels could be collected. They grow only at certain seasons of the year. The Indians come far and near to gather them. The worms are dried in the sun, the shell rubbed off, when a yellowish kernel remains, like a small yellow grain of rice. This is very oily, very nutritious, and not unpleasant to the taste, and under the name of koo-chah-bee [kutsavi] forms a very important article of food. The Indians gave me some; it does not taste bad, and if one were ignorant of its origin, it would make fine soup.(1966, 417)

Besides being tasty when larvae, the flies do not land on or annoy humans. Brine flies have a peculiar ability to crawl underwater by clinging to tufa or another solid object. “You can hold them under water as long as you please— they do not mind it— they are only proud of it,” wrote Mark Twain. “When you let them go, they pop up to the surface as dry as a patent-office report, and walk off as unconcernedly as if they had been educated especially with a view to affording instructive entertainment to man in that particular way” (1913, 176). They breathe air trapped around the hairs of their bodies, like simple scuba tanks. Mark Twain said the brine shrimp was the only thing that exists under the surface of the lake (not quite true) and described it as “a feathery sort of worm, about one-half inch long, which looks like a bit of white thread frayed out at the sides. If you dip up a gallon of water, you will get about fifteen thousand of these. They give to the water a sort of grayish white appearance” (1913, 176). But they themselves are not gray. Seen close-up, they are colorful, ranging in hue from ocher to turquoise. Most of the adult shrimp die or are eaten by grebes in the fall,

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when icy-cold winds whip across the lake and algae grow and multiply. With no shrimp grazing them, the algae “bloom” turns the lake pea-soup green. From January to April, miniature shrimp hatch. By June the young shrimp attain adulthood and are grazing the algae. Slowly, as they eat the algae, the water clears so that it is possible to see as far as 30 ft (10 m) under the water, 10 times as far as allowed during the winter, and you can see plumes of shrimp near tufa towers. This species of shrimp is well adapted to Mono Lake water, which is toxic to most other brine shrimp species. About 250 tons of shrimp (over 20 billion individual shrimp) are harvested each year for fish food. Even this enormous amount does not dent the total population in the lake. Algae, shrimp, flies, and birds are the dominant species, although a small midge has been seen, and rumors mention a “Mono Monster.” All these species depend on a safe haven in Mono’s waters. The gulls that lay their eggs on Negit Island are now in great danger, as their nesting ground, once safe from predators, became connected to the mainland in 1979 because of falling water levels due to Los Angeles’s withdrawal of water. In 1976, 33,000 gulls were counted, but the disastrous land bridge allowed the coyotes and other predators to invade Negit, and in 1979 not a single gull remained. Even the flies may be prey to the falling waters. Studies at Great Salt Lake show that the greater the salt content, the fewer the flies, and as the water level falls, the salinity increases. Indians ceased their fly harvest in 1950. Even the brine shrimp cannot survive if the salinity continues to increase.

Los Angeles Takes Mono How Los Angeles gained access to the waters of the eastern Sierra is a story of political history, not natural history. Mono was not the only Sierran lake to suffer the attention of water speculators, but what happened to it was dramatic. Owens Valley, as water people could see, was a prime candidate for a federal irrigation project. But before that could happen, Los Angeles engineers began buying options to land in Long Valley, and water rights to water from the Owens River drainage, as well as farms and ranches around Mono Lake, tricking or fright-

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ening ranchers into selling. When it became apparent that Los Angeles engineers had cheated the farmers as well as making promises they did not keep, normally peaceful farmers grew violent. Between 1924 and 1927 they blew up the Los Angeles aqueduct 17 times. At one point, they turned all water out of the aqueduct for five days. In 1941, the Los Angeles Department of Water and Power began diverting Mono’s streams. As late as 1970, the department completed another aqueduct, and expanded its groundwater pumping. As the extensive marshes and wetlands dried up, farmlands returned to brush, and both Owens and Mono Lakes shrank. Owens Lake became completely dry, and in only 11 years. between 1941 and 1982, Mono Lake dropped 45 ft (13.7 m). When few nesting and resting areas remained, the flocks of migrating waterfowl stopped coming to Mono. But there is some hope. Through litigation, conservation groups, notably the Mono Lake Committee, the California Trout, and the National Audubon Society, have forced Los Angeles to release minimum flows of water, but it is only one-quarter of what is needed to maintain Mono Lake.

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Overleaf: Tenaya Lake and Mount Conness, surrounded by some of the many domes in Yosemite National Park high country. Part of the Tuolumne ice field descended through this canyon into Yosemite Valley.

EXCEPT FOR EVOLUTION, few geological controversies have engaged the American public as did the argument over the origin of Yosemite’s scenery. Certainly, Yosemite is special, but what made it so? What agencies carved its stupendous cliffs laced with spectacular waterfalls? Where is the rest of Half Dome? These are still intriguing questions, but in 1870 they were burning. On one side of the controversy was Josiah Whitney, state geologist of California and a man with a long list of scientific credentials. On the other was John Muir, with half as much college behind him as Whitney, virtually no professional scientific experience, and about half Whitney’s age. Whitney was in charge of a scientific survey and had all the headaches of dealing with politicians, while Muir lived hand to mouth, at first as a sheepherder, making only enough money to survive. These two men, Whitney and Muir, squared off in the matter of the “Yosemite problem.” Was faulting the origin of magnificent Yosemite Valley, as Whitney claimed, or was it glaciers, as Muir maintained? The two men were as opposite in upbringing and personality as their ideas were far apart. We shall see the Yosemite Problem from Whitney’s professional, scholarly point of view, then through Muir’s intuitive, hands-on approach. After their deaths, François Matthes set about resolving the controversy and found that both men were partially right. He gave us the framework of Yosemite’s own story, which is still being fleshed out.

Josiah Dwight Whitney and the California Geological Sur vey Josiah Dwight Whitney (1819–1890) (fig. 56) was born into a wealthy Massachusetts family whose ancestors came to America in 1635. He graduated from Yale College in 1839 and followed that with graduate work at mining institutes in Europe. When he came to California he was already highly respected for his work in geological surveys in New Hampshire, Iowa, Illinois, Wisconsin, and Lake Superior, as well as in the metallic resources of the country east of the Mississippi River and in the lead region of upper Missouri.

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Figure 56. Josiah Dwight Whitney.

Whitney’s mission for the California Geological Survey, which the state legislature established in 1860, naming him “State Geologist,” was admirably expressed and highly scientific. He chose his assistants well; all of them did high-quality work for the Survey and later became civic leaders as well as leaders in their fields. Throughout the life of the Survey, Whitney was hampered by a lack of funds. Many members of the legislature, who no doubt thought they had voted for a scientific dowsing rod that would pinpoint new gold bonanzas, grew restive and disillusioned when Whitney produced science, not gold. Funds from the legislature, when they came at all, were less than promised and were late. Even with volunteer unpaid help, Whitney had to foot some of the bills himself. Whitney was a New England blueblood who did not mix well with the miners in the rough-and-tumble mining camps, although the miners, despite their outward appearance, were intelligent, and some as well educated as he. He was serious about his science, and although he could have explained to the miners why he directed the Survey to do what it did, and thereby perhaps win the miners’ support, he chose instead to wear his mantle as the man of science who knows best. He was a stubborn man, and once he made up his mind, he did not deviate. Several times he was wrong, but he would seldom back down, even when confronted with facts. The top of Mount Starr King, for example, he declared “inaccessible.” It has been climbed many times since.

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Mount Lyell, too, was “inaccessible.” Half Dome, Whitney said pontifically, was “perfectly inaccessible. It will never be trodden by human foot” (Whitney 1871) Whitney was wrong too, about glaciers. California has no glaciers, he pronounced. When Clarence King, after leaving the California Geological Survey, was shown living glaciers on Mount Shasta, King announced the glaciers to the world in print and named the largest “Whitney Glacier.” Probably he meant this as an honor, but he, and perhaps Whitney, no doubt appreciated the irony, whether Whitney admitted it or not. Whitney was quite certain that there were no living glaciers in the Sierra Nevada. Even when John Muir measured the rate of glacial movement on Lyell glacier in 1871, Whitney refused to back down. As for glaciers creating the Yosemite scenery, Whitney absolutely disagreed. Although he had recognized evidence of former glaciers in Yosemite, he later repudiated it. At any rate, glaciers, he maintained, positively did not create Yosemite scenery. Whitney’s stock was lowered among his scientific colleagues in the mysterious affair of the “Calaveras skull.” The skull came to him in a roundabout way, so he did not see where it actually had rested in the ground, but nevertheless he pronounced it Pliocene in age, or about 10 million years old, which is far older than any other human artifact found anywhere, then or now. text continues on page 344

Figure 57. Yosemite Valley.

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THE CALAVERAS SKULL

hen Josiah Whitney, the state geologist of California, received the so-called Calaveras skull (fig. 58), a part of it had already been cleaned. He cleaned it further, cutting away gravel and volcanic ash that were covering it. He found, mixed with the gravel, other fragments of what had once been human bone. Chemical analysis showed that the skull

W

Figure 58. The Calaveras skull. One of several views of the skull published by Josiah Whitney after he left the California Geological Survey.

had been largely changed through the years from organic matter and phosphate (bone) into carbonate (stone); in other words, it had become fossilized. Realizing that this could be a find of paramount importance,Whitney traced the history of the skull before he received it.According to Whitney’s account of the affair, Dr.William Jones, a physician of Murphys, Calaveras County, wrote to Whitney on June 18, 1866, telling him that the skull had been found in a mine shaft on Bald Mountain, near Angels Camp, Calaveras County, 130 ft (40 m) below the surface, close to a petrified oak.The mine was a drift mine, tunneling below cemented Tertiary gravel and volcanic material. From that time on, the remains were referred to by the redundant name “Calaveras skull.” (Calaveras means “skulls” in Spanish.) Whitney found that the skull had already passed through several hands.William Mattison said that he found it in his shaft on Bald Hill in February 1866. He did not recognize it as a skull, thinking it to be part of the root of the petrified tree that lay nearby. He gave it to John C. Scribner, the Wells Fargo agent, whose clerk cleaned off some of the encrusting gravel, revealing it as a skull.When they discovered this, they passed

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it on to Dr. Jones, who was known to be interested in natural history. He kept it several months before writing to Whitney. Whitney was never able to visit the exact site of the find, as Mattison had allowed his mine shaft to fill with water.Whitney could not, therefore, verify the geologic (stratigraphic) position in which it was found. He relied on Mattison’s word. Indeed, he had no reason to doubt it, as Mattison was known to be an honest and intelligent man. Whitney then determined that the skull was that of a human essentially no different from one of today; the skull resembled the skulls of the natives of the area. Based on what Mattison told him of its position in the shaft, and on its state of preservation, he concluded that it was Pliocene in age, making it the oldest human fossil in the world known at that time.A century ago, very little was known of the antiquity and origin of humans.The story is only now being fleshed out, but even today a fossil of our own species, Homo sapiens, of undoubted Pliocene age would rate headlines throughout the world. In the nineteenth century, the Pliocene Epoch was thought to have ended about 10 million years ago. Now that we have methods of determining the actual years more precisely, the end of the Pliocene has been pushed forward to two million years ago. Nevertheless, if the skull were Pliocene, it would still have belonged to the oldest human known in the Americas and vie for the world’s record. Pliocene times in the Sierra Nevada were markedly volcanic.Vast lava flows streamed down the mountainsides, filling stream valleys and coating the landscape with a tough rind.The ancestral Stanislaus River, in a branch of which the Calaveras skull was said to have been found, had already been filled by a volcanic ashfall before Pliocene time, literally turning the river into stone.The ash was capped in some places by tougher Pliocene lava, which has withstood weathering these past millions of years, while the ground around it has been washed down into California’s Central Valley, market basket of the nation. A fossil skull did not seem strange in such a setting, where mountain tops are made up of once-flowing stream beds.This is the “Table Mountain” into which Mattison dug his drift mine. He hoped to burrow beneath the protecting lava and ash into what had been the bed of the ancient Stanislaus River, there to find deposits of virgin placer gold. Presumably, he did not; at any rate Mattison abandoned his mine before Whitney could enter it. Whitney’s assertion that the find was a Pliocene skull was immedi-

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ately attacked. Many of his scientific colleagues, especially Dr.William Blake, pointed out that Whitney had no way of knowing how old the skull was because he did not personally remove it, or even see the shaft from which it came. Most of the evidence of antiquity came from its stratigraphic position, that is, its position in the layers of rock as they are stacked in nature.All of the stratigraphic evidence was hearsay, and even Mattison, the finder, described the skull as “lying” in the shaft. It was, other scientists suggested, a previously buried skull that had gotten into the shaft by hook or by crook. Within months, the story that it was “by crook” began to circulate. The tale that it was a hoax had several variations, but the first to be published was that the skull had been placed in the shaft by some miners as a hoax to catch Whitney. More hearsay.Whether it was a joke or not, writers and miners got a lot of fun out of it, at Whitney’s expense. Near the turn of the twentieth century, both geologist Waldemar Lindgren and paleontologist J. C. Merriam reviewed the entire Calaveras skull episode and dismissed it as a hoax on Whitney.The skull, Merriam concluded, had probably been fossilized in a cave.The matter stood at this point in 1961, when the late Ian Campbell became, by legislative act, Whitney’s immediate successor as official California state geologist, even though nearly a century had gone by.The general consensus was that Whitney had been hoaxed. But were Whitney’s conclusions justified, based on what he knew? True, he seemed to be uncommonly anxious to leap to them, but unless Mattison were lying, he had no reason to think that the skull had been planted, although Mattison did say the skull was “lying” in the shaft. What’s more, the joke was not very well planned, if it was a joke. If miners had placed the skull in Mattison’s shaft as a joke to catch the state geologist, why did they not follow through at once? Why wait five months while the skull passed from hand to hand before it ended up on Whitney’s desk? Or, if another version of the hoax story is to be believed—that the joke was intended to be on Mattison—what was the joke? Mattison did not recognize the object as a skull, and neither did anyone else until it was cleaned. In fact, this is one of the stumbling blocks in the hoax version of the story. If the skull had been cleverly prepared by cementing gravel over it, why did the perpetrators cement it so well that it was unrecognizable? And where did they get a fossilized skull to use as a joke? If they did not tamper with it, how did they know it was a skull? Perhaps,

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if the miners did do it, they found a skull from a cave, not knowing it was a skull, and tossed the unknown object into Mattison’s shaft to see what he would make of it. In other words, they angled for a minnow and caught a whale. To settle the age of the Calaveras skull once for all, State Geologist Ian Campbell approached the faculty at Harvard, where Whitney had taken the skull, and found that a few months before, the eminent archaeologist Kenneth Oakley of the British Museum had taken a fragment of the skull for analysis by the fluorine method.This was, in some ways, better than having it analyzed by the carbon-14 method, as it required only a small amount of bone, whereas a carbon-14 analysis could take a large percentage of the remaining skull. The fluorine method does not, however, give an age directly in years, as radioactive methods do. It provides a comparison with other fossils that have been analyzed in the same manner.Therefore, if the skull were to contain fluorine comparable to a thousand-year-old bone, it would be of little interest; if it contained an amount comparable to a 50,000-yearold bone, or, as Whitney thought, a several-million-year-old bone, it would be of tremendous interest. Oakley’s results showed a fluorine content for the Calaveras skull that compared with bones that are only 5,000 years old.The skull contained .23 percent fluorine, while a Pliocene bone from nearby registered 5.9 percent. So it was an old skull, but not a very old skull. Oddly enough,Whitney himself knew the fluorine content of the skull, and knew how it compared with a fossil Pliocene rhinoceros jaw. The rhinoceros bone contained 4.77 percent calcium fluoride, whereas none was reported for the Calaveras skull. Part of the bone in the Calaveras skull had been replaced by calcium carbonate, the mineral that builds cave formations.At the time,Whitney did not appreciate the significance of this, as the fluorine method for dating had not yet been developed.To him, it merely meant that the skull had been fossilized. Whitney’s leap to the antiquity of the Calaveras skull was an unscientific jump, and he knew it. He did not see the skull “in place”—that is, where it was actually found—and had no way of knowing whether it was embedded in Pliocene lava or not. So the provenance—the very foundation of his claim for great antiquity—was scientifically doubtful. He was essentially relying on gossip: who gave it to whom in what condition. Whitney had been dead for more than 60 years when the age in years of the skull was determined. No doubt he died still insisting it was Pliocene.

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Other scientists pointed out that he had no way of knowing how old the skull was, but Whitney insisted that it was ancient. Rumor circulated that it was a hoax on Whitney, and his stock among the miners — and probably the legislature— plummeted. Even today we do not know if it was meant to be a hoax, but we do know it was only 5,000 years old, not 10 million. But it was not Whitney’s scientific ideas that brought the California Geological Survey down. The legislature supplied funds only now and then, and never enough. In 1874, the Survey ended. Before it completely expired with a whimper, Whitney left. The governor had demanded that Whitney put the Survey’s seal of approval on a dubious mining venture. Honorably, Whitney refused and resigned. He was right; the mining scheme was a fraud. But Whitney did not yet give up on California. He published results of the Survey’s work (including a double-page engraving of the Calaveras skull) at his own expense. His California experience left him embittered, but he recovered and went on to a successful academic life, spending most of it as a professor at Harvard. He was an original member of the National Academy of Sciences, and author of many scientific treatises. Whitney did not get the respect he desired from California, but in 1870 he was granted an honorary doctorate from Yale. After the Survey died from malnutrition, the legislature refused to fund another agency dedicated to geology. In 1880, the California Mining Bureau was created, but its head was known as the state mineralogist. For years no geologists were on the staff. It was not until the 1940s that State Mineralogist Olaf P. Jenkins, who had a Ph.D. in geology, managed to include a few geological positions, and geology became halfway respectable to the state. In 1966 his successor, Ian Campbell, contrived to add “and geology” to the agency’s title, making it the California Division of Mines and Geology, and Ian Campbell himself became only the second official state geologist.

John Muir (1838–1914) If you define a good American as one who stays out of jail, is kind to his family, and produces a taxable income, then John Muir was as good an American as any.

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If you define a great American as one who helps change the direction of this country toward more socially desirable goals, then John Muir was a greater American than all but a handful of U.S. Presidents. When Muir began his conservation career in the late 1880s, America was committed to a totally devastating attack on the environment. When Muir died in 1914, the Nation was committed in spirit, if not always in fact, to the wise use of its natural resources. That, in a nutshell, is his greatness. (Sierra Club 2003)

In 1860, the year the California Geological Survey was founded under Josiah Whitney, John Muir was winning prizes at the Wisconsin State Fair for his inventions: he had built clocks, barometers, hydrometers, table saws, and more. He was 22, which was four years older than Clarence King. Unlike Whitney and King, Muir did not come from a wealthy family. His father was a pioneer immigrant from Scotland who farmed in Wisconsin, using John and his brothers as full-time unpaid laborers. The next year, 1861, Muir enrolled at the University of Wisconsin, where he took courses in chemistry, botany, and geology and Figure 59. John Muir in his later taught school in winter. years. In 1864, while King and Cotter were having their wonderful High Sierra adventure, Muir was on a tour of his own, a walking tour through Wisconsin, Iowa, Illinois, and into Canada, the very region in which Whitney had done geology and that had given him his geological reputation. That same year President Abraham Lincoln, in the nation’s first act of wilderness preservation, signed a bill giving Yosemite Valley and the Mariposa Big Tree Grove to California as a state

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Plate 83. The southwest ridge of Cathedral Peak showing strong vertical jointing.

park. Whitney’s survey had backed the bill, and Whitney and Ashburner served on a commission to manage the park. In 1866, the year Whitney’s attention was called to the Calaveras skull, Muir was working as an engineer and foreman for a manufacturer of carriage parts in Indianapolis. The next year, while working, he was painfully blinded in a factory accident. When he recovered, he decided to set out on a thousand-mile walking tour that took him to Florida. He hoped to go to South America, but after a stopover in Cuba, he took ship for New York City and from there sailed to San Francisco, arriving on March 28, 1868. That summer he got a job herding sheep in Tuolumne Meadows. His walking experience served him well, and soon he was climbing and studying in the high mountains, making a first ascent (Cathedral Peak, in Yosemite [pl. 83]) and becoming intrigued by glaciers. From then on, he was focused on mountains and glaciers. Although he was interested in natural history in general, some acquaintances thought he cared more about the large objects he could see than the small ones. President Theodore Roosevelt, who

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camped with Muir for three days in Yosemite, wrote,“John Muir, I found, was not interested in the small things of nature unless they were unusually conspicuous. Mountains, cliffs, trees, appealed to him tremendously, but birds did not unless they possessed some very peculiar as well as conspicuous traits” (Roosevelt 1915). Certainly, mountains and glaciers are large features in the landscape. By 1871, Muir had discovered what he considered a living glacier in the Sierra: the Maclure glacier. The next year he planted stakes in the glacier to measure its rate of flow and found that it did, indeed, move. But Whitney would have none of it. “There are no glaciers at all in the Sierra Nevada” (Whitney 1882), he thundered. Clarence King, miffed by Muir’s increasing popularity, wrote (King 1878), “The absurdity of applying the word ‘glacier’ to a snow-mass which appears and reappears from year to year will be sufficiently evident. Motion alone is no proof of a true glacier.” Of course, it is not clear that King saw the same places Muir saw. King added an altogether unwarranted insult: “It is to be hoped that Mr. Muir’s vagaries will not deceive geologists who are personally unacquainted with California, and that the ambitious amateur himself may divert his evident enthusias-

Plate 84. Mounts Muir and Whitney, together in the landscape, if their namesakes were not in thought. Mount Muir is the nearby pointed peak, and Mount Whitney, behind, has a flattish top. Because Muir is nearer, it looks higher, but it is not; Muir is 14,015 ft (4,272 m); Whitney is higher at 14,496 (4,418 m).

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tic love of nature into a channel, if there is one, in which his attainments would save him from hopeless floundering.” Whitney did not help matters when he called Muir “a mere sheepherder” and declared his ideas “absurd, based on ignorance of the whole subject.” Such intemperateness dimmed the luster of the truly good work done by the California Geological Survey. No doubt Whitney’s and King’s remarks were tinged by jealousy. Muir, a relative newcomer, was being sought out. In 1870 he began guiding tours through Yosemite and met Joseph Le Conte, a professor of geology at the University of California, on a geological expedition — the University of California Excursion Party — to Yosemite. Muir and Le Conte found many points of agreement on geology and on glaciers. When Ralph Waldo Emerson came to Yosemite in April of 1871, it was Muir, not Whitney he visited. Also in 1871, King’s book, Mountaineering in the Sierra Nevada, was published, as was Muir’s first article on California,“Yosemite Glaciers” (1871). The next year Muir published “Living Glaciers of California” (1872) — glaciers Whitney claimed did not exist. Asa Gray, a prominent botanist and professor at Harvard, sought out Muir in Yosemite that year, and the artist William Keith asked Muir to accompany him into the mountains and became Muir’s lifelong friend. And, to add to King’s discomfiture, Muir made a first ascent of Mount Ritter, which King and Gardiner had failed to conquer. In the 1870s, when the Whitney-Muir controversy was at its height, the study of glaciers was youthful. Everyone knew there were living glaciers in the Alps that had been observed and studied by Louis Agassiz, Horace Benedict de Saussure, and a few others, and in 1871 geologist John Tyndall (for whom Clarence King had named a 14,000-ft peak), a professor of natural philosophy at England’s Royal Institution, gave a series of lectures at the Royal Institution on “the forms of water,” chiefly about glaciers, which was published as a popular book in 1872. It was Tyndall’s and Agassiz’s writings that informed and inspired Whitney, King, and Muir. Agassiz had been a pioneer in measuring the movement of glaciers. Here is Tyndall’s account of one way of measuring alpine glacier flow: [On the medial moraine of the Unteraar glacier in Switzerland] in 1827 an intrepid and enthusiastic Swiss professor . . . built a hut with a view to observations upon the glacier. His hut moved, and

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he measured its motion. In the three years—from 1827 to 1830—it had moved 330 feet downwards. In 1836 it had moved 2,354 feet; and in 1841 M. Agassiz found it 4,712 feet below its first position. (Tyndall 1872, 59–60)

Later, Tyndall developed a method of driving stakes into the glacier for a more accurate reading, and still later, he learned to use surveying equipment to be even more exact. But except for the use of surveying instruments, the science of glaciology rested on observation, a talent John Muir had in abundance. So enamored was Muir of glaciers that he lived for a time in a hut at the snout of an Alaskan glacier. Although his hut was right at the glacier’s snout then, the glacier has since receded, leaving the hut with a good distant view but not a close-up of the glacier. Muir was a person who “made a difference.” He had a vital part in the establishment of national parks, beginning with Yosemite (1890; it had been in state hands) and continuing with Sequoia (1890), Mount Rainier, Washington (1899), Petrified Forest, Arizona (1906), and Grand Canyon, Arizona (1908). One park, Muir Woods National Monument, near San Francisco, was named for him at the insistence of William Kent, who donated the property.

Figure 60. View down Yosemite Valley toward Cathedral Rocks.

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“It was his writings that roused presidents, congressmen, and plain Americans to action,” reads “The Importance of John Muir,” published by the John Muir Historical Site (Sierra Club 2003). Much of his writing is “true adventure,” which appealed to armchair travelers the world over. Some of it is “purple,” but his passion shows through and saves it. There is no doubt he wrote from the heart: Any fool can destroy trees. They cannot run away; and if they could, they would still be destroyed—chased and hunted down as long as fun or a dollar could be got out of their bark hides, branching horns, or magnificent bole backbones. . . . Through all the wonderful, eventful centuries since Christ’s time—and long before that—God has cared for these trees . . . but he cannot save them from fools—only Uncle Sam can do that. (Sierra Club 2003)

Muir was one of the leaders in the movement for forest preservation that culminated in the Forest Reserve Act of 1891. President Benjamin Harrison, who signed it, created 15 reserves before leaving office in 1893, including 13 million acres in the mountain West. Presidents Grover Cleveland, William McKinley, and Theodore Roosevelt added nearly 200 million acres, and during Roosevelt’s administration Congress authorized creation of the U.S. Forest Service. Muir failed in one of his major battles: the saving of Hetch Hetchy Valley (pl. 85). Despite his pleas and those of others (including the Sierra Club, which he cofounded in 1892), in 1913 the city of San Francisco got permission to turn beautiful Hetch Hetchy into a reservoir. Some say it broke his heart. He died of

Plate 85. The Hetch Hetchy Reservoir.

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pneumonia on Christmas eve, 1914. He would be pleased to know that in 1999 the new organization Restore Hetch Hetchy was formed. Muir’s life had many highlights. He was given four honorary degrees (Harvard, 1896; University of Wisconsin, 1897; Yale, 1911; University of California, 1913), but for many people, his duel with Whitney over the geological story of Yosemite is probably the best known. If it were not for Muir, we might never remember Whitney at all. True,Whitney’s name is on the highest Sierran peak, but after over a century, most people merely wonder where the name came from, whereas Muir was chosen the “Greatest Californian” by a poll of the members of the California Historical Society in 1976 and is still well known.

Yosemite Becomes a “Problem” In 1868, the year Muir arrived in California, Whitney published a book written for the general public, which he called The Yosemite Book. It was a guidebook intended to “call the attention of the public to the scenery of California, and to furnish a reliable guide to some of its most interesting features, namely, the Yosemite Valley” (Whitney 1869). Whitney decided that Yosemite Valley was the result of faulting. The valley came to be because the bottom between two blocks of the Earth’s crust dropped along faults. It was not an unlikely explanation. Such valleys are well known and are technically called “grabens” (from the German word graben for “trench”). Death Valley is a graben; so is the Dead Sea; so also, as Whitney pointed out correctly, is the valley of Lake Tahoe. Whitney was in the vanguard of science when he ascribed Earth features to faulting. “During the process of upheaval of the Sierra,” he wrote (Whitney 1869),“there was at the Yosemite a subsidence of a limited area, marked by lines of ‘fault’ or fissures crossing each other . . . nearly at right angles. . . . The bottom of the valley sank down.” In a more lively passage, he says: “This mighty chasm has been roughly hewn into its present form by the same kind of forces which have raised the crest of the Sierra. . . . The Half Dome seems, beyond a doubt to have been split asunder in the middle, the lost half having gone down in what may truly be said to have

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Plate 86. Aerial view of Half Dome, Yosemite National Park. The dome, which looks as if it had been severed in half by “a frightful amputation,” as travel writer J. Smeaton Chase suggested near the turn of the twentieth century, is not half of a larger dome. It is a whole dome, being worn by wind and weather. Both the rounded back and the 2,000-ft-high (610-mhigh) sheer front are controlled by northeast-trending master joints, and the two sides are parallel. The astonishing front was not sliced off by glaciers, as glaciers served only to carry away debris that accumulated at the cliff’s foot, and to tear off a few new sheets. Despite the rounded back, glaciers never covered Half Dome—it is not a roche moutonnée— although one early ice advance got within 500 ft (150 m) of the top. The gently rounded back is an ancient feature, dating to Tertiary times. The back is not massive, as is the front; it was sliced by parallel, steeply dipping fractures that broke it into a multitude of thin, standing sheets trending northeast. Water, percolating between the sheets, froze in winter, expanding them and breaking off fragments. In time, the north slope was weathered into a jumble of slabs and slivers. During glacial times, much of the weathered debris was borne away by the glacier. The front, in contrast, was monolithic. Although it was controlled by jointing, it was not fractured into thin sheets, but retained its massive shape.

been ‘the wreck of matter and the crush of worlds.’” It would be a century before the “forces” are taken to be the shifting of continental plates. At first, Whitney saw evidence of glacial action in Yosemite: grooves, scratches, moraines. But he refused to believe that glaciers carved the valley, and as time went by and the argument

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grew hotter, he maintained that glaciers had nothing to do with Yosemite, although he had earlier admitted that one moraine may have acted as a dam for a lake. “In his zeal to combat the glacier menace,” wrote Bill Guyton, “he even repudiated his friend Clarence King and his own earlier writing by denying that ice had ever occupied Yosemite Valley!” (1998, 72). Curiously, Whitney noted the glacial origin of Yosemite’s twin, Hetch Hetchy Valley, where he pointed out glacial polish 800 ft (240 m) and a glacial moraine 1,200 ft (370 m) above the valley floor. Certainly Muir had read Whitney’s Yosemite Book, first published the year Muir arrived in California and saw the Yosemite. No doubt he studied it carefully, but when he went into the mountains, he made up his own mind. By 1870, Muir was firmly convinced that glacial action, not faulting, was responsible for the creation of Yosemite Valley. Muir showed Professor Joseph

Plate 87. Upper Little Yosemite, Yosemite National Park.

Le Conte of the University of California much of the glacial evidence he had located, and Le Conte wrote, “I strongly incline to the belief . . . that a glacier once filled Yosemite” (1971, 64). In 1871, the New York Herald Tribune published Muir’s first article from California,“Yosemite Glaciers,” and Muir followed it the next year with “Living Glaciers of California” in the Overland Monthly. Whitney was not very successful in combating the glacier menace. Muir’s evocative writing was more convincing than facts, although he had plenty of them. Here is his conclusion in his chapter on glaciers in his book, The Yosemite: The action of flowing ice, whether in the form of river-like glaciers or broad mantles, especially the part it played in sculpturing

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the earth, is as yet but little understood. Water rivers work openly where people dwell, and so does the rain, and the sea, thundering on all the shores of the world; and the universal ocean of air, though invisible, speaks aloud in a thousand voices, and explains its modes of working and its power. But glaciers, back in their white solitudes, work apart from men, exerting their tremendous energies in silence and darkness. Outspread, spirit-like, they brood above the predestined landscapes, work on unwearied through immeasurable ages, until, in the fullness of time, the mountains and valleys are brought forth, channels furrowed for rivers, basins made for lakes and meadows, and arms of the sea, soils spread for forests and fields; then they shrink and vanish like summer clouds. (1988, 144)

Muir was so enthusiastic he often went too far, without evidence to back him up. “All California has been glaciated, the low plains and valleys well as the mountains,” is how he opened his chapter on glaciation in The Yosemite. He was quite wrong.

Matthes Tackles the Yosemite Problem But Muir was right about so much, and the controversy had been so heated, that in 1913 the U.S. Geological Survey assigned François Matthes to solve the Yosemite Problem. By then, Whitney was long dead, and Muir would die the next year, well before Matthes could produce any results. François Emile Matthes (1874–1948) (fig. 61) was born in Amsterdam, Netherlands. He came to the United States in 1891, studied at the Massachusetts Institute of Technology, then worked with the U.S. Geological Survey for most of his life. When he began his work in Yosemite, he had the advantage of a new, detailed topographic map of the valley, one he himself had made. While Matthes was pursuing the glaciers, Frank C. Calkins mapped the bedrock — the granitic rocks — so a new look at Yosemite would be complete. Alas, it was only half complete. Calkins, always a perfectionist, refused to allow his map to be published until he understood every detail thoroughly. He never did. He died without seeing the map in print, but it has recently been

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issued and is, whether perfect or not, the best map of the geology of Yosemite Valley available. After studying the Yosemite Problem, Matthes did not try to adjudicate between glaciers and no glaciers. Obviously, there had been glaciers in the valley; Muir was right about that. He decided to try to figure out just how much influence glaciers had had in the development of the features of the valley. Muir had said that Yosemite was entirely carved by glaciers, but he had been too extreme. Matthes weighed the role of glaciers and the role of streams and concluded that the erosion of Yosemite Valley is the combined result of rivers and Figure 61. François E. Matthes. glaciers (figs. 62–64). It started with a river valley that the river, now the Merced, deepened as time went by. The river eroded its bottom and sides, carrying rocks, pebbles, and sand downstream. Then came ice, which tended to transform the V-shaped river valley into one more like an inverted horseshoe. The glacier plucked large blocks of rock from the valley walls by freezing onto them, then the blocks, as well as sand and gravel, were carried down glacier by ice. Matthes pointed out that the ice had not completely filled the valley; that the crown of Half Dome, for example, stood above the ice; that the Sierra Nevada never had a “universal ice sheet”; and that the eroding glaciers were of local origin. Joints, he said, were of “supreme importance” in understanding the sculpturing of Yosemite’s walls. Half Dome never endured “a frightful amputation”—there is no missing half—the back and front have simply weathered differently. His study also revealed that the glaciers

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Figure 62. Bird’s-eye view of Yosemite Valley as it was just before being invaded by glaciers of the Great Ice Age. The valley was deep, with a V-shaped inner gorge and side valleys. The entire region, up to timberline, was covered with coniferous forests, much as it is today. In the center background is Half Dome, here a massive, cliffless mountain; in the left foreground is El Capitan, not yet a sheer face. Cloud’s Rest, left background, is only somewhat less eroded than today. Peaks on the skyline include Echo Peak to the far left, and Mounts McClure, Lyell, and Florence to the right. This reconstruction and the one following were drawn by the late François E. Matthes, student of Yosemite, who spent many years unraveling the geologic story of the valley.

now in the Sierra are not remnants of the giants of yesteryear; they belong to a new generation of glaciers he called the “Little Ice Age.” His beautifully written popular book, The Incomparable Valley, though elderly by now, is a must for all who wish to understand the Yosemite. Matthes did not live to see The Incomparable Valley published. It was carefully and lovingly edited by Fritiof Fryxell and published in 1950, after Matthes’s death. Most of the

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Figure 63. Bird’s-eye view of Yosemite Valley as it probably was immediately after the Great Ice Age. The valley had been deepened and broadened; a lake 5.5 mi (9 km) long, dammed by a glacial moraine, occupied the valley floor. Large topographic features looked very much as they do today.

words are Fryxell’s. Although he took as many words as he could from Matthes’s published work and notes, he had to add much, and to interpret much. (When the first edition of this book was published, I was touched and delighted that Dr. Fryxell sent me an autographed copy of The Incomparable Valley, from one Sierran lover to another.)

Yosemite’s Own Stor y Properly speaking, Yosemite’s story begins, just as yours and mine does, with the “big bang,” if that is truly how the Earth

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1. El Capitan 2. Three Brothers 3. Royal Arches 4. North Dome 5. Half Dome 6. Mount Lyell 7. Sentinel Dome 8. Glacier Point 9. Bridalveil Fall 10. Merced River

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5 4

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Figure 64. Bird’s-eye view of Yosemite Valley, with selected landforms identified.

began. But the creation of the valley was later than the creation of the Earth, or even the creation of the Sierra Nevada. The cutting of the valley began about 25 million years ago, when uplift and tilting of the mountains allowed the Merced River to begin to erode a deep valley. By about a million and a half years ago the climate was right, and the range had reached a height that allowed glaciers to form. Three times, perhaps more, glaciers from the crest of the range reached long fingers down into Yosemite Valley, finally coalescing into one major trunk glacier. The glaciers widened, straightened, and deepened the valley to a much greater degree than we can see today. Geophysicists have measured the depth to bedrock in the valley and find that the true rock bottom is, in some places, 1,800 ft (600 m) below the present surface. The most extensive Yosemite glaciation, as far as we know,

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Figure 65. An avalanche chute northwest of Hamilton Lake. Avalanche chutes may have been initiated in glacial times, but they are enlarged today by repeated slides of new snow and rock debris.

took place about a million years ago. Glaciers pushed their icy digits down Yosemite Valley at least twice after that, but the million-year-old one was the largest. Then ice filled Yosemite Valley completely, spilling over onto the surrounding land. In places the smaller tributary glaciers could not keep up, and if we had been there to see it, we would not have noticed the tributary glaciers at all, but instead, just one massive ice sheet, like a river in flood. When the sheet melted, the valleys of the tributary streams were far above the now-ice-free valley of the trunk glacier. They were left “hanging,” and the water streams that now ran in them plunged over the oversteepened banks of the valley of the former trunk glacier as waterfalls, plunging into a large, deep lake. The marks of that glaciation have been partly erased by later ones. The most obvious present marks are those of the glaciation of about 20,000 years ago, which left moraines, hanging waterfalls (fig. 66), and Lake Yosemite, which gradually filled with sediment, leaving a flat surface the Merced River and thousands of tourists now meander through.

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Figure 66. The Tu-lool-we-ack, or South Fork waterfall.

Yosemite’s Domes Yosemite is, of course, still in the process of creation. Rockfalls change cliffs; lakes fill; shells drop from domes, making them smaller. Many domes remain; there is even one called “Stately Pleasure Dome.” But even if we do not have another glacial episode to help create scenery, day-to-day erosion will eventually make vast changes. As domes disappear, leveled by wind and weather, others will take their places. Matthes wrote: The enormous, billowy terraces of granite that flank the Merced Canyon above Little Yosemite will at some time not far distant, geologically speaking, resolve themselves into a great herd of domes. The two promontories of Cascade Cliffs, in the Little Yosemite, are well on the way toward being detached and transformed into domes. But other masses lie still so far beneath the general level of the land that millions of years must pass before they can become surface features. Such are the huge monoliths

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that form the basement of Clouds Rest and the pedestal of Half Dome. But the most noteworthy and most colossal of these deepseated masses is that which slopes down in a smoothly rounded, spreading cone beneath the cliffs of Glacier Point. At least 1,500 feet high, as far as it is exposed to view, and more than half a mile in diameter, it bids fair, in another geologic period, to become an enormous and exceptionally beautiful dome, a worthy successor to Half Dome and its peers. (Matthes 1950, 128)

So, even if we have a good start on solving the “problem” of Yosemite’s origin and history, Yosemite itself will continue to change, so the “problem” will never be finally solved.

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CHAPTER 13 THE MOUNTAINS TREMBLE

Overleaf: Emerald Bay, Lake Tahoe. Tahoe is the third deepest lake in North America. Its basin was created by faulting between two arms of a split crest of the Sierra Nevada. During the Great Ice Age, huge glaciers developed on the western side, but on the eastern side only in shaded areas of the high peaks. The glaciers left their marks as moraines, one of which helped create Emerald Bay. (See also pl. 96.)

theories we have today may seem as ridiculous tomorrow as the idea that earthquakes are caused by a great turtle shaking the Earth on its back. Such an idea of the Earth was once held by millions of people. We call it primitive; yet our current theories may be just as far from the truth. In our present view, the Earth quakes because of the activity of Earth’s tectonic plates, particularly on plate boundaries. Yet the Sierra is a long way from any plate boundary. It is the final western range in the Basin and Range province, made up of linear mountains separated by linear valleys. The province has been and is being stretched laterally, presumably by the movement of plates, and as it is stretched, the crust of the Earth thins. Some geologists think that because the Earth is thinner there, weak zones allow magma to rise, accompanied by faulting and earthquakes. From about 210 to 80 million years ago, the granite we can now see in the Sierra was formed. Then from about 80 to 55 million years ago, great quantities of overlying rock, as well as part of the granite itself, were washed into the adjacent sea to form thick sedimentary beds in what is now the Central Valley and farther west in areas now removed from the Sierra. Many clues point to this conclusion, but two major ones are the key. First, there are no sedimentary beds 80 to 55 million years old in the mountains to show that deposition was going on throughout the Sierra; in fact, most places have deeply weathered soils, indicating that erosion, not deposition, was the order of the day. Second, the rocks that were deposited in nearby areas have a chemical and mineralogical composition—particularly the feldspar minerals—that is what we would expect from the granite of the Sierra Nevada. The mountains were worn to low hills by 55 million years ago (end of early Eocene Epoch). From that time to about 30 million years ago (Oligocene Epoch), events moved slowly. The low mountains contributed some gold to the Tertiary rivers, but little sediment to the sea. When the volcanoes began erupting in earnest in the middle Oligocene, the pace of change increased. Rhyolite flows poured over the crest, and rhyolitic ash blew into the river channels. Lava and mudflows followed, piling up as much as half a mile in thickness in the northern Sierra. Some time during the volcanic episode (which we are still in), the northern Sierra, and probably the southern as well, was uplifted and tilted to the west. Evidence for this is the abandoned stream channels lying high on the

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ridges, coupled with the deep canyons in which the present rivers run. We know that most of the canyons on the west were cut before glaciation began two million years ago, because their channels are partly glaciated and contain some debris abandoned by the glacier but not yet reworked by the streams. All of the uplift was not completed by the end of glacial times; it is still going on. In the past hundred years engineers have worked steadily at remeasuring mountains to see if they have risen. Some seem to be taller than they were, in spite of erosion; however, our measurements are so few, our instruments so crude, and our history so limited that we cannot be sure that direct measurement has been accurate. But, even if our techniques are adequate, and our time span long enough, we must remember that measurements are made relative to sea level. The sea can and does change level in response to Earth forces and in response to the quantity of water available. A change in climate that melts or increases the polar ice caps can drastically alter sea level. We know some mountains rise rapidly, in human terms. Paricutín in Mexico rose in a few months; Surtsey in Iceland was born in weeks; acres of land have been added to Hawaii while tourists watched. On February 9, 1971, the San Gabriel Mountains outside Los Angeles rose six ft (2 m) in a few moments in a moderate earthquake. The Sierra Nevada has young volcanoes that rose quickly, and numerous faults that have lifted mountains and shaken the Earth. Old faults in the Sierra, such as the Bear Mountain fault zone and the Melones fault zone in the Mother Lode, have raised the mountains in days gone by and have served as avenues for gold-bearing solutions. As far as we know, their “activity”—that is, when earthquakes were taking place along them — is long past: they seem now to be fossil earthquake faults, though this may not be true, for nature has many surprises.

Finding Faults Numerous active faults in the Sierra testify to the continuing rise of the mountains. Faults are flaws in the continuous skin of rocks in the crust of the Earth, along which the Earth has moved (pl. 88). On maps they are shown as lines; if you see a fault in

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Plate 88. Fault line scarp near the Alabama Hills.

nature, it is likely to look like a cliff (if it has not been eroded away), or a low place, perhaps studded by a series of ponds. Rivers that go in unexpected directions may mark faults; so may topography that looks out of place in the landscape, or rock strata that do not connect. The relationship between faults and earthquakes was thoroughly established only after the San Francisco earthquake of 1906, when Henry Fielding Reid suggested that the earthquake is the result of “elastic rebound.” As the Earth builds up stress—for whatever reason—in zones of weakness in the Earth’s crust, it climaxes at the point where the rock breaks suddenly. Because rock is somewhat elastic, it reacts like a rubber band that has been stretched: it breaks and “twangs.” The vibration—the twang—is the earthquake. Faults along the eastern side of the Sierra are the most active in the range (fig. 67). About 10 million years ago, faulting commenced to lift the mountains; by two million years ago, the work was essentially completed in the northern part, to make the mountains as they are today. Faulting in the southern half of the range started later and is not yet finished. Many active faults in the Sierra are potential earthquake faults. In fact, one of the most severe earthquakes in California’s history struck the east face of the Sierra Nevada, destroying every brick, stone, and adobe building in the Owens Valley town of Lone Pine, killing a tenth of the population (pl. 90), and giving us a telling lesson in earthquake engineering. The moon was just past full that Tuesday night of March 26, text continues on page 370

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THE KERN RIVER AND ITS CANYON

spectacular, several-thousand-foot-deep canyon cuts through the High Sierra in Sequoia National Park, giving the range a two-crested aspect.To the east is the main Sierra Crest; to the west is the Great Western Divide.The canyon was initiated by the Kern Canyon fault, at 80 mi (129 km) long the longest in the southern Sierra Nevada, then later enlarged by erosion.The fault is a very old one; to the south, it is covered by a lava flow that has been dated at 3.5 million years, so it is at least that old. Because the fault cuts the Whitney Intrusive Suite, which is 85 million years old, it is younger than that. So it is older than 3.5 million years and younger than 85 million years. Scientists working on the fault zone think it is probably nearer to the age of the Whitney Intrusive Suite than to the younger lava flow. Movement along the fault has pulverized the rock in a zone several hundred feet thick, and through the ages the pulverized rock has in many places been replaced by tiny tourmaline crystals that give a blue cast to the rock along the fault. In Great Ice Age times, large valley glaciers, fed from the high country of both the Sierra Crest and the Great Western Divide, flowed southward down the Kern River Canyon (pl. 89), widening and straightening the river’s course, making the upper Kern into a long, nearly straight canyon several thousand feet deep and 25 mi (40 km) long. The fault has been inactive for many millions of years, but signs of life in the form of hot mineral springs hint that the story is not yet all told. One mineral spring, active in the late nineteenth century, had a strong sulfur odor, and sulfur actually piled up on the ground so thickly that it sometimes caught fire and burned. In the geologic past, mineral-rich waters and emanations deposited gold and other minerals in the rocks near the fault. Frémont’s party found a little in 1851, but until a man named Lovely Rogers found the “Big Blue” vein in the early 1860s, no doubt in the blue tourmaline, no rush ensued. But soon there were numerous mines and several mining camps along the upper reaches of the Kern. The most important of the camps was Kernville (originally called Whiskey Flat). Mining peaked in 1879, but old Kernville lived on until the early 1950s, when the town vanished under the waters of the newly created Isabella Reservoir. The reservoir was built to help control the flow of

A

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Plate 89. The upper Kern River Canyon. Kern River is among the few Sierran rivers that flows south rather than west. It follows a fault zone that is more than 3.5 million years old, one that still has hot springs heated by underground magma.

the Kern River, which carries up to 700,000 acre-feet of water each year, enough to cover 700,000 football fields with one foot of water. The dam at Lake Isabella was barely able to contain the flood of 1966, when 598,400 gallons (2,265,183 liters) of water per second poured down Kern Canyon. Where the Kern River leaves the Sierra Nevada foothills and crosses the Kern River fault, it has formed a huge wedge-shaped alluvial fan of sand and gravel. Here the river spreads out after leaving the confines of the canyon and drops much of its load.The upper 200 ft (60 m) of this several-thousand-foot-thick mass of sand and gravel is saturated with groundwater; even so, only about 7 percent of it is actually water. Nevertheless, the amount of water contained in the fan—93 million cu ft (2.6 million cu m)—is enough to fill Lake Isabella to the spill point more than 163 times. It is enough, also, for the city of Bakersfield, which depends on this fan, to have a supply of fresh, clean groundwater for many years to come.

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Sierra Nevada Faults Faults along which the Earth has moved in the last two million years, including those active in historic time

40°

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Reno 80

Lake Tahoe

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Figure 67.

1872, when the great Owens Valley earthquake struck Owens Valley. It is one of the three huge earthquakes in California’s history, the other two being the Tejon Pass earthquake of 1857, estimated at magnitude 7.7, and the Great San Francisco earthquake of 1906, estimated at magnitude 8.3. The Loma Prieta earthquake of 1989, the second worst quake in terms of economic loss, occurred

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Plate 90. The grave of a victim of the 1872 earthquake at Lone Pine.

when seismographs were in place, so the magnitude is known exactly: 7.1 on the Richter scale. The Owens Valley quake really “struck” the western United States, as it was felt as far east as Salt Lake City, but it was sparsely populated Owens Valley at the foot of the High Sierra that was most severely damaged and where all the dead and injured had lived. Since 1872, a few moderate-sized earthquakes have shaken the Sierran front, most of them near Long Valley. The exact time of the Owens Valley earthquake is not known to the fraction of a second, as it is for earthquakes today; but Pleasant Arthur Chalfant, one of the publishers of the Inyo Independent, whose newspaper is one of the principal sources for information on the quake, looked at his watch just after he made his escape from the collapsing building that housed the newspaper’s offices and its staff. It was, according to him, 2:24 a.m. Nine-year-old Eva Lee Shepherd, who had sneaked out of her home six miles south of Independence to spend the night with two girl friends on a ranch a mile away, gave a slightly different time for the earthquake. She and her friends were asleep in a sod room. The night was frosty, and the children pulled the covers over their heads to ward off the chill. The house collapsed in the initial shock, right on top of them. “My first memory,” wrote Eva — later Mrs. Gunn — in retrospect, “is a sensation of being

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smothered. Then someone seemed to be walking right over us. As a matter of fact, someone was; the Paiute Indian who worked for Mr. Rogers [the neighbor] was searching in the piles of debris for the bodies he knew must be somewhere underneath. He fished us out, sobbing and gasping, but saved from the slightest bruise by the thick quilts.” Shivering outside in the night, she heard one of the men say, “Oh, look at the moon. It seems to be 10 miles long.” “Have you ever,” asked Mrs. Gunn,“seen a boy at a campfire pick up a brand and wave it to and fro? Well, that was just the effect we got from this lunar display except that we were moving back and forth with the ground, while the moon was standing still!” (Hill 1972). When Eva got home, she was greeted with joy instead of punishment by her mother, who feared she had been in the collapsed adobe front room of their farmhouse. The rest of the house, built of wood, was standing. She watched while her father unearthed what he could salvage of their belongings from that doomed front room. Among them was a grandfather clock, which had stopped at 2:10. Many others were not so lucky as Mrs. Gunn. The number of deaths is not entirely clear from the historic record, but 27 is the number generally given. The Inyo Independent listed the names of 19 known dead at Owens Valley immediately after the quake, with “two or three more yet to be added to

Figure 68. Headlines as they appeared in the Inyo Independent following the earthquake of 1872. Altogether, 27 people were killed in the Owens Valley area.

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the list” (fig. 68). Of these, eight were children. One child died at Camp Independence, and Henry Tregallas, superintendent of the Eclipse mill, died in his wife’s arms. Sixteen were buried in one common grave, now marked by a monument. Most of them had no known relatives within reach, as they came from Ireland, Chile, France, Mexico, and the eastern United States. This quake was, or should have been, a lesson in building construction in earthquake country. Fifty-two of the 59 buildings in the town of Lone Pine were destroyed, including every building not made of wood. Every dead or injured person was within one of the destroyed buildings. W. A. Chalfant, son of the publisher of the Independent, wrote: Every instance of personal harm was due to the character of the buildings . . . in use. The population of Lone Pine was largely composed of Mexicans, who had exercised their preference for . . . adobe as a building material. . . . Three-fourths of Lone Pine’s buildings were thus made, and about 60 of them toppled down in the shake like piles of children’s blocks. . . . The buildings at Eclipse, all adobe, and some others elsewhere shared the same fate. The courthouse at Independence was of burned bricks, and collapsed. Only one frame building in the valley was leveled, and that was an unsubstantial and cheap shed. (Hill 1972)

Revising the Mountains Damage to towns is most immediately noticeable to people, of course, but nature made many changes in the Earth that bright night. In addition to the fissures, lakes, slumps, and twisted ground common to earthquake country, the Sierra Nevada itself was severely wracked. John Muir described the fall of Eagle Rock in Yosemite, and C. Mulholand has testified, “I have seen pine trees, that must be 100 feet or more in height, still standing erect, but only their tops visible. The whole canyon where they stand is filled up with rocks, the debris from high peaks that fell during the earthquake” (Hill 1972). Owens Lake (which had water in it then) experienced a seiche (an earthquake-induced wave) a few feet high. “Fissures in the Earth are numerous and extend all over the valley,” wrote the editor of the Inyo Independent, who made his own field study. “Vast

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Plate 91. Fissures developed during the earthquakes of the 1980s in alluvial sediments on the edge of the Owens River flood plain, approximately 3 mi (5 km) north of Benton Crossing.

crevasses have been opened, new lakes formed, sinks of from ten inches to twenty feet and covering acre after acre, cracks extending miles, the [Owens] river partially dammed and turned, and the foothills are in places rent with wide cracks!” (Hill 1972). Mrs. Vernon Smith, a survivor of the quake, told of a steer being caught in an “earthquake crack.” Her father rescued it, but the animal lived only two days. Stories of “earthquake chasms” swallowing cows seem to be universal, so much so that there must be some modicum of truth in them, even though they are generally disbelieved by scientists. John Muir, the Sierra’s most eloquent lover, was living in Yosemite Valley on the other side of the Sierran crest at the time of the earthquake. Here is his description of it, perhaps the only eye-witness description of the effect of earthquakes on the mountains themselves: The shocks were so violent and varied, and succeeded one another so closely, that I had to balance myself carefully in walking as if on the deck of a ship among waves, and it seemed impossible that the high cliffs of the Valley could escape being shattered. In particular, I feared that the sheer-fronted Sentinel Rock, towering

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above my cabin, would be shaken down, and I took shelter back of a large yellow pine, hoping that it might protect me from at least the smaller outbounding boulders. For a minute or two the shocks became more and more violent— flashing horizontal thrusts mixed with a few twists and battering, explosive, upheaving jolts — as if Nature were wrecking her Yosemite temple, and getting ready to build a still better one. . . . It was a calm moonlight night, and no sound was heard for the first minute or so, save low, muffled, underground bubbling rumblings, and the whispering and rustling of the agitated trees, as if Nature were holding her breath. Then, suddenly, out of the strange silence and strange motion there came a tremendous roar. The Eagle Rock on the south wall, about a half a mile up the Valley, gave way and I saw it falling in thousands of the great boulders I had so long been studying, pouring to the Valley floor in a free curve luminous from friction, making a terribly sublime spectacle—an arc of glowing, passionate fire, fifteen hundred feet span, as true in form and as serene in beauty as a rainbow in the midst of the stupendous, roaring rock-storm. The sound was so tremendously deep and broad and earnest, the whole Earth like a living creature seemed to have at last found a voice and to be calling to her sister planets. . . . The first severe shocks were soon over, and eager to examine the new-born talus I ran up the Valley in the moonlight and climbed upon it before the huge blocks, after their fiery flight, had come to complete rest. They were slowly settling into their places, chafing, grating against one another, groaning, and whispering; but no motion was visible except in a stream of small fragments pattering down the face of the cliff. A cloud of dust particles, lighted by the moon, floated out across the whole breadth of the Valley, forming a ceiling that lasted until after sunrise, and the air was filled with the odor of crushed Douglas spruces from a grove that had been mowed down and mashed like weeds. . . . After a second startling shock, about half-past three o’clock, the ground continued to tremble gently, and smooth, hollow rumbling sounds, not always distinguishable from the rounded, bumping, explosive tones of the falls, came from deep in the mountains in a northern direction. . . . Shortly after sunrise a low, blunt, muffled rumbling, like distant thunder, was followed by another series of shocks, which, though not nearly so severe as the first, made the cliffs and domes

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tremble like jelly, and the big pines and oaks thrill and swish and wave their branches with startling effect. . . . During the third severe shock [that same morning] the trees were so violently shaken that the birds flew out with frightened cries. In particular, I noticed two robins flying in terror from a leafless oak, the branches of which swished and quivered as if struck by a heavy battering-ram. Exceedingly interesting were the flashing and quivering of the elastic needles of the pines in the sunlight and the waving up and down of the branches while the trunks stood rigid. . . . It was long before the Valley found perfect rest. The rocks trembled more or less every day for over two months, and I kept a bucket of water on my table to learn what I could of the movements. The blunt thunder in the depths of the mountains was usually followed by sudden jarring, horizontal thrusts from the northward, often succeeded by twisting, upjolting movements. More than a month after the first great shock, when I was standing on a fallen tree up the Valley . . . I heard a distinct bubbling thunder from the direction of Tenaya Canyon. . . . The air was perfectly still, not the faintest breath of wind perceptible, and a fine, mellow, sunny hush pervaded everything, in the midst of which came that subterranean thunder. Then, while we gazed and listened, came the corresponding shocks, distinct as if some mighty hand had shaken the ground. After the sharp horizontal jars died away, they were followed by a gentle rocking and undulating of the ground so distinct that [the dog] Carlo looked at the log on which he was standing to see who was shaking it. It was the season of flooded meadows and the pools about me, calm as sheets of glass, were suddenly thrown into low ruffling waves. (Muir 1901, ch. 8)

How Big Was It? The first scientist at the epicenter after the earthquake of 1872 was California State Geologist Josiah Whitney. He never wrote a scientific article on the Owens Valley earthquake; his only contribution was a paper in two parts published in the Overland Monthly, a general magazine of the times that emphasized articles of interest to the West. Both parts were reprinted later by the California state mineralogist with no added information.

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Whitney was a specialist in mineral deposits and a theoretical geologist. His articles, although they represent the most immediate observations by any geologist in the Owens Valley area, do not provide much information for present-day analysis. He devoted much of his effort in speculation as to the cause of the earthquake — as we still do — but the fundamental propositions to which he applied his field observations are not the same as those we use today. He thought the ground fractures, which are so carefully measured now after each earthquake, were of small importance, as they were the result, not the cause, of the earthquake. To him, when the Earth shakes, the ground breaks; to modern theory, when the Earth breaks, the ground shakes. After over a hundred years of field and historical reevaluation, scientists have concluded that faulting and ground rupture extended nearly 100 miles, and some of it is still visible today. The net vertical displacement—the uplift of the mountains—was 16 ft (4.9 m). The Sierra Nevada has been uplifted along faults on the eastern side of the range many thousands of feet, though not all at once, during the past two million years (Quaternary Period). Seismographs had not been invented yet, and no precise time signals existed, so no magnitude ratings exist, because they rely on accurate time and seismographic records (fig. 69). Instead, estimates of damage were translated to “intensity,” which gave a good idea of the damage done and some idea of the strength of the earthquake. Foreshocks—at least, some smaller quakes— made themselves felt from March to July 1871, and people in Lone Pine and nearby felt sizeable aftershocks. The earthquake was a big one. Although it is difficult to pinpoint the severity of the earthquake with little measured data, scientists think it to be one of the greatest on record for the western United States, excluding Alaska. General John Bidwell’s new mansion in Chico, 300 miles from the epicenter, lost plaster, and the brick walls of the new Presbyterian church cracked. Most of the Central Valley felt the quake; nearly everyone in Fresno, Stockton, Sacramento, Yuba City, and other valley towns was awakened, and many ran outside. From San Diego to Eureka, people were alerted. In Los Angeles, some were thrown from their beds and most ran into the streets. Even though most people were asleep when the shock occurred, residents of Salt Lake City who were awake could feel it. By comparing an “isoseismal” map of the damage (fig. 70)

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with that of a similar reference quake of known magnitude, scientists at first estimated its magnitude to be not less than 8.25, which is about that of the San Francisco earthquake of 1906. But a later estimate, based not on damage, but on the length and amount of offset on the fault (now known as the Lone Pine fault), gives the magnitude to be about 7.7. The eastern mountain front rose upward at least 16 ft (4.9 m) in a few moments that bright night and moved horizontally, as well. Calculations — admittedly based on far too short a historic record—indicate that an earthquake of this magnitude might be expected along the Sierran front every few hundred years. Discounting smaller ones, and assuming that this is a “500-year” earthquake (on present evidence, this seems conservative), the rate of Sierran uplift from faulting, accompanied by large earthquakes, would be 32 ft (918 m) per thousand years. At this rate, in a million years, the total uplift would be about 32,000 ft (9,754 m). True, 32,000 ft may be a great deal more than the Sierra Nevada actually rose in a million years, but it shows how much earthquakes can accomplish. It is quite likely that much of the earthquake’s energy was not translated into vertical uplift of the mountains. Owens Valley,

Figure 69. Recording of an earthquake from a standard seismograph. A is the amplitude of the incoming seismic wave, P the primary wave, and S the secondary wave. To calculate the magnitude, measure the amplitude in millimeters, and use its logarithm for the calculation. To determine how far away the source of the shake was, determine the time between the arrival of the primary wave and the secondary wave. Strength is calculated at the earthquake’s epicenter. The Richter scale is logarithmic. Between one whole number on the scale and the next, the strength increases by a factor of 10. An M 6 earthquake is 10 times as violent as an M 5. An M 8 is 1,000 times as violent as an M 5.

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perhaps, was dropped down; although this gives the same effect —making the mountains relatively taller—it does not lift them higher above sea level, which is what their altitude is based upon. Field measurements of uplift in the last two million years — since the beginning of the Great Ice Age — based upon elevation

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Figure 70. “Isoseismal” map of the Owens Valley earthquake of 1872. The earthquake was felt as far away as Salt Lake City; it damaged buildings as far away as Chico. The lines on the map are lines of equal intensity, which is a measurement of earthquakes based on damage. The center, or bull’s-eye, contains the hardest hit area. The area marked “IX” was the next most severely damaged. The Roman numerals designating the zones are based on the modified Mercalli Intensity Scale. Intensity, a measure based on subjective experience and damage, differs from “magnitude,” a measure of the power of an earthquake based directly upon mathematical measurements. Neither this scale of intensity nor scales of magnitude were developed in 1872. This map was drawn from historical accounts of the earthquake. Although it was prepared in 1972 in commemoration of the centennial of the earthquake, it was the first such map published for it.

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Plate 92. Mount Dana, Mount Lyell, and Lyell glacier.

of glacial moraines, height of cliffs (“scarps”) produced by faulting, displacement of volcanoes and volcanic deposits, elevation of volcanic flows, and geophysical measurements, indicate that in the southern Sierra Nevada the mountains have risen or the valleys have dropped by virtue of faults and earthquakes perhaps as much as 19,000 ft (5,790 m). Much of the change has taken place since the hot ashfall of 760,000 years ago. For example, Mount Dana (pl. 92), alongside Tioga Pass, has been estimated to be rising at a rate slightly less than 1.5 in. (3.8 cm) per century. This would not disturb a hiker, but if continued for 10,000 years, Mount Dana would be 12.5 ft (3.8 m) higher. In fact, the whole Sierran crest is rising more rapidly now than in the past 25 million years, a rate that exceeds the rate at which erosive processes are wearing the mountains down.

The Ner vous Sierra Most tectonic (nonvolcanic) earthquakes in the Eastern Sierra are related to large faults that bound Owens Valley. Owens Valley was not created by erosion; instead, it is a graben, a long, narrow block of land dropped down between faults. The depressed block extends from south of Olancha to north of Bishop and is bounded by the frontal faults of the Sierra Nevada on the west and the Inyo and White Mountains on the east. The graben is about 150 mi (240 km) long and 6 to 20 mi (10 to 32 km) wide. The valley floor is about 4,000 ft (1,220 m) in ele-

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Plate 93. Shattered cottonwood adjacent to McGee Creek State Pack Station, destroyed during an earthquake in the 1980s. The tree was hit by a rolling disk-shaped slate boulder propelled by earthquake motion. The boulder ended up more than 165 ft (50 m) south of the tree.

vation, whereas its bounding mountains rise from 11,000 to 14,000 ft (3,350 to 4,267 m) in elevation, with Mount Whitney on the west and White Mountain Peak on the east, both over 14,000 ft (4,267 m). Holes drilled in the valley show that granite bedrock is as much as 5,000 ft (1525 m) below the surface, so the bounding faults can have displacements of 15,000 ft (4,572 m). The fault scarp on the Sierran side, called the Sierra Nevada fault zone, is one of the most imposing in the world, both geologically and scenically. The Owens Valley earthquake, however, did not occur on any of the faults bounding the graben, but rather on the not very impressive Owens Valley fault. The southern Sierra gradually became more seismically active in the 1970s, culminating in a 5.8 magnitude earthquake beneath Wheeler Crest (called the Bishop earthquake) in October 1978. It was followed by a series of earthquakes near Mammoth Lakes in May 1980, the greatest recorded seismicity in the eastern Sierra in the twentieth century (pls. 93–95, fig. 71). From May 25 to 27, the Mammoth Lakes area was shaken by a series of earthquakes that included four of magnitude 6, two of 5, and more than 300 measuring magnitude 3.0. The larger earthquakes damaged

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Plate 94. Rhyolite block that fell during the 1980s earthquake sequence. This relic is about half a mile north of Mammoth and is plainly visible from U.S. Hwy. 395.

Plate 95. Oblique aerial photo of a rockfall avalanche about half a mile in length. The avalanche is in a cirque wall on the east flank of Mount Baldwin.

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Figure 71. Seismograms of the four largest earthquakes, May 1980. Time is Greenwich, 7 hours later than PDT. Recording stations are Berkeley, CA (BKS), and Jamestown, CA (JAS).

structures and triggered rockfalls. Taken by themselves, the earthquakes, most of which (magnitude 3.0) were barely perceptible, would not have been unnerving, but their persistence and timing—about the same time as the eruption of the Washington volcano, Mount St. Helens—worried the inhabitants as well as the scientists. The pattern of earthquakes was not typical of fault movement. It might have meant a volcano was about to erupt in or near Long Valley, and although none did, there remains the possibility that one might (see chapter 9). The Long Valley activity included long-period earthquakes, common in nearly all active volcanoes, which probably indicated fluid movement within the Earth in or near Long Valley Caldera. The dome within Long Valley has continued to rise, which is unnerving because volcanoes tend to swell before an eruption. In the past few million years in the northern part of the Sierra, faulting has not been as prominent a means of raising the mountains. Instead, the northern part appears to be lifted up and tilted to the west, with far less fault breakage. The tilting, as nearly as can be determined on present evidence, was completed before the faulting in the southern part started in earnest.

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Figure 72. Types of fault movement.

The northern mountain mass commenced to rise and to be tilted about 90 ft (28 m) per mile (1.6 km) during the period from 25 to 12 million years ago, increasing to 140 ft (43 m) per mile in the span from 12 to two million years ago. At the end of the Pliocene Epoch, two million years ago, the southern portion began to be bent and broken, a process that is still going on, perhaps more slowly, today. Looking backward into time, it is easy for us to draw arbitrary lines in history.“This is a period of uplift,” we might say,“extending for three million years.”Yet we do not yet know how many in-

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dividual episodes of uplift occurred within that time span, nor can we tell how many lifetimes might have been lived without any perceptible change in the mountains. Today, the West Coast is so shaky, with “earthquakes in diverse places,” that we do know we are living in a period of strenuous mountain making. The many shakes, terrifying though they may be to us who must live or die with them, are nevertheless creating the scenery we value so highly. Had we lived in a century with few or no earthquakes, we might have thought all activity had ceased; yet from a longer perspective, it is obvious that we live in the midst of violent times. Geologists in the first half of the twentieth century saw records of pulses in the uplift of the Sierra Nevada that were separated by periods of erosion, in which the mountains were worn down to a more or less flat plain (“peneplain”) close to sea level. Various geologists recognized three or four peneplains, and hence four or five stages of uplift, dating from the Miocene, about 20 million years ago, to the Great Ice Age. The facts they based their conclusions on were principally physiographic, dependent on the idea that large flat areas at approximately the same elevation were once continuous levels. Because continuous levels were thought to be produced only in the so-called old age of the landscape, when the mountains had been reduced to plains and there were no rushing torrents, steep canyons, sharp cliffs, or waterfalls, the flat areas represented times when the Sierra had been subdued. That three or four levels (ranging in elevation from the crest of Mount Whitney to about Yosemite Valley) existed meant that there were several periods of uplift between.

The “Up” Stair Using this kind of information, the late François Matthes was able, by 1930, to construct in drawings his interpretation of what Yosemite Valley looked like at various stages. Two of his drawings are shown in figs. 62 and 63 They give us a very clear idea of what one man saw, looking carefully and imaginatively into the past. The facts on which he based this picture are clear but, like everything else in science, can be interpreted in other ways. Recent

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Figure 73. “Pom-pom-pa-sus” or the Three Brothers, Yosemite National Park. The westward slope of the upper surface of the Brothers has been determined by joints.

work, equally careful and imaginative, has given us a new picture of the few million years just before our time. According to this later view, few, if any, of the peneplains existed. There are similar levels to be sure; Dr. Matthes was correct in that. But the similar levels are accounted for not by the wearing down of entire mountain ranges to sea level, but by the weathering out of giant steps. This later interpretation indicates that, in areas of granitic rocks, a giant staircase is produced within the mountain range by the normal processes of erosion. Where granitic rock is buried, it commences to turn to soil much more quickly than where it is exposed; the groundwater, working on the rocks, has much longer to break them down than it does where the water is shed quickly from the rock surface. Once weathering starts, it enlarges the flat areas, where still water can work, while the steeper parts, where rushing water carries the loose material away, remain steep.

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Calling it a staircase implies an evenly graded flight, which is not true at all. The stairs are surrealistic, with uneven beginnings and strange continuations. Most of the steps face the San Joaquin Valley at a variety of levels, but some lead upward from steep canyons in other directions. The mountains are lifted up by the movement of plates, and worn down by the processes of erosion. We happen to be living at a time when these Earth forces, acting together, have given us majestic Sierran peaks to give our lives mountain-top experiences.

LAKE TAHOE: THE PARK THAT ISN’T

ahoe might have been a national park. In 1912, 1913, and 1918, Lake Tahoe (then known as Lake Bigler) was proposed for a national park, but commercial and agricultural interests shot the proposal down. The Washoe Indian name for Tahoe is Da-ow-ga, which transliterates into “Tahoe,” meaning “Big Water.” For some time, it seemed unnecessary to set Tahoe aside as a national park, as the lake was so large—22 mi (57 km) long, 12 mi (31 km) wide, with 191 sq mi (495 sq km) of surface area—that it would never be overpopulated or over enjoyed.And it was not, until the 1950s, when development began in earnest and has been proceeding apace ever since. Tahoe is a high lake (pl. 96), lying at 6,225 ft (1,897 m) in average surface elevation. It is said to be the highest lake of its size in North America, but because no other lake is exactly its size, it is hard to know what that means.Tahoe is the third deepest lake in North America, exceeded in depth only by Crater Lake, Oregon, at 1,949 ft (594 m), and Great Slave Lake, Canada, at 2,010 ft (613 m), and tenth deepest in the world. Its average depth is 1,000 ft (305 m), and at its deepest spot, near Crystal Bay, it is 1,645 ft (501 m), although that measurement is not exact, as the depth fluctuates from day to day. The basin that Tahoe occupies was created by faulting, no doubt accompanied by earthquakes.The lake is cradled between the arms of a dual crest of the Sierra Nevada.The main crest trends northwestward toward Donner Summit, through Donner Lake, Squaw Valley ski area, and Myers Grade Lake; the eastern crest extends northward to become the Carson Range.Tahoe lies within the split crest, where Earth movements lifted both the western and eastern crest, leaving a boxlike depression— a graben—that filled with water.And faulting is not over.The many young faults in the Tahoe Basin—those whose ages are measured in thousands

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Plate 96. Emerald Bay in Lake Tahoe.

of years, not millions—are testimony to earthquakes that have shaken Tahoe in more recent times. Bedrock in the Tahoe Basin consists of old metamorphic rocks and granitic igneous rocks. One sequence of old metamorphic rocks, the Mount Tallac pendant, is more than 15,000 ft (4,500 m) thick and consists of metamorphosed volcanic and sedimentary rocks; since neither the top nor the bottom of the sequence can be seen, the total thickness must have been much greater before erosion stripped the top. Granitic igneous rocks dominate the bedrock landscape, mostly granodiorite with a sprinkling of tonalite, diorite, and gabbro in small bodies.A sample of the granodiorite was dated to be 106 ± 2 million years old (Cretaceous). Sheets of volcanic rock cover large areas of the granite in the northwestern part of the basin and along the lower Truckee River.The headwaters of the Upper Truckee River, at Stevens Peak, originate in a volcanic pile 2,000 ft (600 m) thick. On the northern shore of the basin, the centers of eruption were near Mount Watson and Mount Pluto.The eruptive centers sent out flows: lava flows of andesite, basalt, and latite, which, when mixed with water and loose rock and soil, became volcanic mudflows.The mudflows moved many miles over gentle slopes, leaving deposits that are massive and thickly bedded. Here and there in the Tahoe area, the volcanic rocks have been dated.At Carnelian Bay, two samples gave dates of 2.2 and 2.5 million years (late Pliocene); a younger flow near Tahoe City was dated at 1.9 ± 0.1 million years; still another in Truckee Canyon provided a date of 1.3 ± 0.1 million years. Donner Pass volcanic rocks range in age from 2.6 to 7.4 million years.The natural dam that closes the outlet of the Tahoe Basin is a pile of volcanic rock—

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andesitic mudflows and lava—that spreads from the top of Martis Peak (8,642 ft [2,634 m]) to the lake’s shore. Tahoe Basin was changed by glaciation during the Great Ice Age. Huge valley glaciers moved down the canyons along the western side of the lake, scouring away all of the loose rock and building up large moraines.When the glaciers were largest, they were as much as 1,000 ft (300 m) thick and, in some places, covered all but the highest peaks and ridges. On the eastern side of the basin, glaciers developed only on the shaded sides of the high peaks, so that part of the basin was not glaciated. For that reason, the western side has sharp, rugged alpine scenery, while the eastern side is subdued and rolling. The moraines left by the glaciers are testimony to the advance and retreat of the ice masses. Scientists have found a record of four main advances, the oldest being the largest, extending the farthest into the lowlands.At one point during the forward and back dance of the glaciers, large ice streams moved down Pole Creek and Squaw Valley into Lower Truckee Canyon, forming an ice dam that raised the level of Lake Tahoe 600 ft (183 m) higher than it is at present. Occasionally, the ice dam broke free, releasing catastrophic floods, some of them powerful enough to carry huge blocks of granitic rock down Lower Truckee Canyon and across Truckee Meadows east of Reno.As the glaciers melted, ice water carrying silt and sand poured into the lake and built thick deltas, the largest underlying the town of South Lake Tahoe. Tahoe underwater is far from flat (pl. 97). It has mountains, glacial debris, avalanches, faults, and many other features we usually call “landforms” below the surface of the lake which normally remain unseen. Sixty-three streams enter the lake, and only the Truckee River flows out.The lake holds over 39 trillion gallons (148 trillion liters) of water, enough to cover an area the size of California to a depth of 14 in. (36 cm). Enough, indeed, for everyone in the United States to have 50 gallons (189 liters) of water a year for five years. If it were somehow drained it would take 700 years to refill.The amount of water that evaporates from the surface of the lake would be enough to supply a city the size of Los Angeles for five years. The water temperature in the lake is about 40 to 50 degrees F (4.5 to 10 degrees C) in February and March, warming up to 65 to 70 degrees F (18 to 21 degrees C) in August and September. Below a depth of 600 to 700 ft (180 to 210 m), the water remains a constant 39 degrees F (4 degrees C).The lake does not freeze over, although some inlets— Emerald Bay, for example—are occasionally covered by ice.

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FPO

Plate 97. Bathymetry of Lake Tahoe. Depths are shown in color. Tans and yellows show the shallower parts; greens and blues show the deeper parts, down to more than 1,600 ft (500 m). It lies in earthquake country, and its basin was formed by faulting. In this view, long, deep faults are visible in the north end. Two major faults in the lake basin are particularly dangerous. If either of them moved during a magnitude 7 earthquake, for instance, it could generate a giant wave, a tsunami, perhaps 30 ft (9.2 m) high, that could be devastating to structures along the shore. The tsunami, in turn, could generate seiche waves that could lurch from shore to shore for hours.

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Mark Twain stayed a few weeks at the lake in the 1860s and was deeply impressed by its grandeur: The shore all along was indented with deep, curved bays and coves, bordered by narrow sand-beaches; and where the sand ended, the steep mountainsides rose right up aloft into space—rose up like a vast wall a little out of the perpendicular, and thickly wooded with tall pines. So singularly clear was the water, that where it was only twenty or thirty feet deep the bottom was so perfectly distinct that [our] boat seemed floating in the air! Yes, where it was even eighty feet deep ... down through the transparency of these great depths, the water was not merely transparent, but dazzlingly, brilliantly so.All objects seen through it had a bright, strong vividness, not only of outline, but of every minute detail, which they would not have had when seen simply through the same depth of atmosphere. So empty and airy did all spaces seem below us, and so strong was the sense of floating high aloft in mid-nothingness, that we called these boat excursions “balloon voyages.” (Twain 1913, 110)

Although Tahoe is not as clear as it was in Mark Twain’s day, it is still remarkably clear, allowing objects many feet below to be seen from the surface. One reason Tahoe is so clear is that 40 percent of the rain and snow falling into the Tahoe Basin drops directly into the lake, not picking up contaminants on the way down. In addition, much of the rest of the precipitation drains through relatively sterile granitic soil, which filters and clarifies it.And, sewage from around Lake Tahoe is now being exported elsewhere. All lakes go through a natural life cycle, eventually filling with sediment. But as development proceeds around Tahoe, natural processes are quickened by additional sediment being sent into it, bringing nutrients that promote algal growth that clouds the lake.The use of marshes and stream zones for building, as at Tahoe Keys, prevents the filtration of water coming in from the mountains and allows even more sediment to be carried into the lake. But the battle to save Lake Tahoe’s clarity may be slowly being won. Scientists at the University of California’s Davis campus reported in 2002 that in 2001, a white plate suspended from a line could be seen at a depth of 67 ft (20 m); in 2002, it could be seen from 73 ft (22 m). Even so, they warn that clarity will have to continue to improve to be certain that Tahoe’s sapphire blue waters stay blue.

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What is happening to the Sierra today? Are the everlasting hills truly everlasting? Even a brief trip into the high mountains or a drive through the gold country gives clear witness to eternal change, even in so enduring an element of creation as the bulky Sierra. Earthquakes, rockfalls, rock slides, landslides, volcanic eruptions are all fast means of changing the landscape. Gravity aids a single pebble cascading from a height, and aids landslides involving entire mountains (such as Slide Mountain, Nevada, which slid in 1842) in eroding the peaks to level ground. In winter, snow avalanches speed down the peaks’ rock ribs. In the course of years, some of the avalanches have worn channels 50 to 100 ft (15 to 30 m) deep, abraded smooth by the sliding rock, snow, and ice. The areas around Mount Whitney and Sequoia and Kings Canyon National Parks are rich in these strange landforms resembling giant children’s slides. A particularly good set can be seen across the canyon from Bearpaw Meadow on the High Sierra Trail. A process of change that takes longer, but is still within our immediate ken, is that of running water. We can see sandbars shift from year to year; we can watch gravel bars build up in a season; we can see sand, gravel, and rock being whirled along by a mountain stream or a sudden flash flood. It takes longer to observe some of the slower processes, but it is nonetheless possible. The birth and slow death of Kern Lake was nearly within one lifespan. Created in 1867 by a dam formed by a landslide, the lake had built a sandbar by 1916, which by 1928 had enlarged to cross the lower end of the lake. Gradually, the lake is being filled; soon it will be a forest. It is true that nature works on a different time scale than humans, but many human changes can be as sudden as earthquakes and volcanoes and change the face of the mountains quickly.

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Dynamiting for roads or mines causes split-second alteration. An hour’s worth of scraping the surface of one of the granite “steps” for road or housing development may allow accelerated erosion to remove all soil, so as to give us bare rock where once a forest grew. In a little more than 100 years, a network of roads has crossed and recrossed the Sierra. Sometimes it seems there is little space left that is not roadway, and it takes the concerted effort of all those who would preserve some vestige of the high country to keep even a small wilderness inviolate. Other human changes are of a slow-acting sort; we will not know all the consequences of our actions for many generations. Thoughtless forestry or mining practices may allow streams to carry sediment to the sea at a rapid rate, in that way removing the soil that supports the forest and, in turn, destroying the watershed and causing floods. There are innumerable worldwide examples of such human alterations: Greece, once forested, is now a nearly arid land; the cedars of Lebanon, which furnished lumber for millennia, are almost gone. In our own land, we have murdered animals to the last survivor. The last Eskimo curlew is gone; the passenger pigeon no longer blots out the sun; the grizzly, symbol of California, does not roam the Sierra; many other animals and plants we have driven, by our encroaching civilization or by our cruelty, to the brink of extinction. They will be fossils only, and in our day. In recent years, the problem of what to do with the nuclear waste of the world has been plaguing scientists and politicians alike. One proposal is to throw it into one of the deep ocean trenches, where one crustal plate is being forced under another. Since no one has actually seen the plates’ actions, it seems most unwise to dump dangerous waste where it cannot be closely watched. It might well be returned to us in an incalculably destructive way. By our actions we can destroy mountains, poison water, change our land to desert or ice field, or eliminate life altogether. Yet the years of our individual lives are but a flicker in the long days of Earth, and even the Earth’s eventful history is short, measured against the immensity of the universe. We are a middling planet in a small solar system in a minor galaxy. Time is all we have, and it behooves us to spend it wisely. Some say that the time spent in the mountains is not subtracted from our allotted three-score-and-ten. So cherish the Sierra, and it will generously reward you.

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GLOSSARY

Accrete In plate tectonics, to add rock material to a tectonic plate.

One plate that overrides another may scrape the plate below, accreting a great amount of material. The Philippine plate scraped the Eurasian plate, lifting up an accretionary wedge that is Taiwan. Most of the Sierra Nevada block was accreted to the continent during the Antler and Sonoma Orogenies. (See also Antler Orogeny; Sonoma Orogeny.) Acid volcano A volcano that produces lava that is more than 60

percent silica (SiO2) and generally fairly light in color and weight. Aftershock An earthquake that follows a larger one and originates from near the same source (focus). Alaskite A light-colored variety of granite. (See also granite.) Albitite A type of igneous porphyry in which both the large crystals

and the fine-grained background are of the albite variety of feldspar. (See also porphyry.) Alkali fly A fly, Ephydra hians. Also called brine fly. Altithermal A period of high temperature, especially the interval

following the Great Ice Age. Amphibole A mineral group comprising dark-colored minerals

with good cleavage in two directions, intersecting at angles of 56 degrees and 124 degrees. Hornblende is one of the more common amphibole minerals. Amphibolite A type of metamorphic rock, gneiss or schist, with dark (amphibole) minerals and feldspar but little or no quartz. (See also gneiss; schist.)

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Ancestral Sierra Nevada A mountain range that developed along the western margin of what would become North America. Its construction began about 400 million years ago. The range was 700 miles (1,120 km) wide and 3,000 miles (4,800 km) or more long, extending from Alaska into Mexico. Andesite A fine-grained, gray to dark-colored volcanic igneous

rock that has the same chemical composition as diorite. Sometimes another rock name is added to indicate texture: andesite porphyry has the same mineral composition as andesite, with the texture of porphyry; andesite tuff is tuff (volcanic ash) that has the chemical composition of andesite. Antler Orogeny A mountain-building episode that affected the Great

Basin, especially what is now Nevada, in the late Paleozoic Era. Aplite A light-colored, plutonic igneous rock having a sugary texture. Aragonite A mineral composed of calcium carbonate (CaCO3), like calcite, but differing in crystal structure. Arenite A type of sandstone. (See also sandstone.) Argillite A sedimentary rock, a hard variety of claystone. (See also claystone.) Arkose A sedimentary rock, essentially a coarse-grained sandstone, commonly pink, composed of grains of feldspar and quartz. (See also sandstone.) Asbestos A commercial term for a group of minerals that peel off

into thin, strong fibers that are chemically inert. Asbestos was considered a vital material for its fire-resistant qualities until its carcinogenic character was widely recognized. Ash Very fine particles blown from a volcano.Volcanic ash is not the remains of the burning of coal or wood, but is made up of tiny fragments of red- or white-hot natural glass or rock. Asthenosphere A layer of the Earth below the lithosphere. It extends from about 62 to 220 mi (100 to 350 km) below the surface and may be the source of magma. Avalanche chute A track worn into a mountainside by repeated

avalanches. Basalt A dark, fine-grained volcanic rock that has the same chemi-

cal composition as gabbro. Basalt was brought back from the moon. 396

GLOSSARY

Basaltic volcano A volcano that produces lava higher in iron and

magnesium and lower in silica than an acid volcano. (See also acid volcano.) Basement rocks Rocks that are stratigraphically beneath and older than the oldest unmetamorphosed rocks in an area. Basin-Ranges province A physiographic province in the western United States characterized by mountains lifted by faults and separated by sediment-filled valleys. Also called Basin and Range province. Bastite A variety of the mineral serpentine. (See also serpentine.) Batholith A plutonic igneous rock mass that covers a surface area of

more than 40 sq mi (100 sq km) and extends downward an unknown distance. Bedrock Rock that underlies soil or unconsolidated material. Belemnite A cone-shaped fossil related to squids. Both belemnites

and squids are included in the zoological subclass Coleoidea. Black smoke A mineral-rich material expelled from an undersea

chimney. It consists of sulfur gas carrying fine particles of sulfide minerals, especially pyrite, as well as copper, zinc, iron minerals, and gold. Blue gravel In early California gold mining, the oldest and richest

channel deposit miners sought. Bomb, volcanic A bleb of lava that is ejected when fluid and be-

comes rounded by turning over and over in flight. Bonanza A body of rich ore.

Brachiopod A marine invertebrate (one that lives in the sea) char-

acterized by two symmetrical valves (half shells). Brachiopods have been on Earth at least 570 million years. Breccia Rock made of sharp-edged fragments, both large and

small; consolidated rubble. Sometimes another rock name is attached to indicate composition: andesite breccia is breccia made of andesite fragments. Brine fly A fly, Ephydra hians. Also called alkalai fly. Bryozoan A marine invertebrate (one that lives in the sea), commonly called “moss animal.” It lives and grows in colonies. Bryozoans have existed since early Ordovician, about 500 million years ago. GLOSSARY

397

Calcarenite A calcareous rock made mostly of grains of calcareous

sand. (See also calcareous rock.) Calcareous rock A term that may be applied to either sedimentary or metamorphic rock. Virtually all calcareous rocks in the Sierra Nevada have been metamorphosed. Calcareous rock includes limestone, marble, dolomite, calcarenite; all are composed of an appreciable amount of calcium carbonate (CaCO3). Carbonate rock technically has more CaCO3 than calcareous rock, but in this book both carbonate and calcareous rocks are called calcareous rock. Both “fizz” when acid is placed on them. Calc-hornfels Hornfels whose chemical composition includes con-

siderable calcium carbonate (CaCO3). A variety of calcareous rock. (See also calcareous rock; hornfels.) Calcite A mineral composed of calcium carbonate (CaCO3). Cal-

cite makes up most of the cave speleothems (formations). Calc-silicate A variety of calcareous rock containing a mixture of

calcium carbonate (CaCO3) and silicate minerals rich in calcium. (See also calcareous rock.) Caldera A large, basin-shaped volcanic depression, often formed by

the collapse of the roof of a magma chamber after the magma has erupted. Camptonite A variety of diorite. (See also diorite.) Carbonate rock Rock consisting chiefly of calcium carbonate

(CaCO3). (See also calcareous rock.) Carbon-14 A heavy isotope of carbon with a half-life of 5,730 ± 40 years, used in calculating the age of rocks or artifacts that are less than 40,000 years old. Cenozoic Era Latest of the principal divisions of geologic time. (See geologic time scale in text.) Chalcedony A variety of quartz with crystals too small to be seen under an ordinary microscope; may be translucent or transparent, with a waxlike luster. Sometimes used as a gem. Chatter mark A curved scar made by chipping bedrock under a

glacier by fragments of rock carried in a glacier. A chatter mark is commonly convex toward the direction from which the ice moved.

398

GLOSSARY

Chert Very hard, dense, tough rock consisting principally of silica (SiO2). Color varies, but Sierran chert is commonly in thin red, green, or yellow beds. Usually has conchoidal fracture. Same as flint. Chromite A dark brown or black mineral, common in dark-colored

igneous rocks. Chromite is the chief ore of chromium. Chrysoprase Apple green chalcedony. Used as a gem. (See also chal-

cedony.) Chrysotile A whitish or greenish mineral of the serpentine group. It is the most commercially important type of asbestos. Cinder A fragment of volcanic rock sufficiently fine grained that its nature cannot be determined by the naked eye. It is vesicular (has many holes). Cinder cone A conical hill comprising cinders and other volcanic materials ejected from a central vent. Cirque A steep-walled, horseshoe-shaped hollow cut at the head of

a mountain glacier. Cirque glacier A glacier lying in a cirque. Cirque glaciers in the

Sierra Nevada are not remnants of the glaciers of the Great Ice Age but are relatively new ones occupying the cirques of older, larger glaciers. Clay A very fine-grained sedimentary material easily moldable

(plastic) when wet. Also the name for a family of minerals. Claystone A very fine grained rock made from clay. (See also clay.) Climatic optimum An interval of relatively high temperature fol-

lowing the melting (retreat) of the last glacier of the Great Ice Age. A warming that took place between 5,000 and 7,000 years ago. Coal A black rock, made of carbon, that will burn. Sierran coal is very soft. Cone, volcanic A conical hill comprising volcanic materials ejected from a central vent. Conglomerate Rock consisting of sand-sized fragments, together

with dominating, larger rounded rock or mineral fragments. Continental drift The idea that large plates of the Earth’s crust have

moved relative to one another. Continental drift has been absorbed,

GLOSSARY

399

in a modified way, into the theory of plate tectonics. (See also plate tectonics.) Continental plate An Earth plate carrying continental rock as well

as oceanic rock. Convection cell A pattern of movement of material of the Earth’s

mantle in which the central movement is upward, and the sides downward, as a result of heat variation. Convection is considered by some to be the driving force creating subsea trenches and island arcs and causing mountain building. Core The central part of the Earth, divided into the outer and inner

core. The smaller, inner core may be solid. Corestone The central portion of a rock mass. Weathering may remove exterior layers, leaving the center, or corestone. Cornish pump A device made of huge timbers, used to remove water from a mine. Correlate To show that geologic phenomena are of the same age or

lithology in spite of being separated geographically. Craton A part of the Earth’s continental crust that has been stable for some time. Cretaceous Period The final period of the Mesozoic Era, lasting from about 144 to 65 million years ago. (See geologic time scale in text.) Crevasse A deep crack in a glacier. Some crevasses are as much as

300 ft (91 m) deep. Crinoid A sea creature (echinoderm) characterized by a globular body with arms extending radially. Crinoids were known in seas of 500 million years ago, and their descendants are still living. Crust The outermost layer of the solid Earth. Curtain A calcite deposit formed in a cave when mineral-laden

water flows across an overhanging surface. Dacite A variety of andesite having more quartz and less feldspar than most andesite. (See also andesite.) Delta A nearly flat tract of land at the mouth of a river, commonly in a fan or triangular shape, like the Greek letter Δ (delta).

400

GLOSSARY

Diabase A variety of the igneous rock diorite, consisting of plagio-

clase feldspar (labradorite) and a dark mineral (pyroxene). (See also diorite.) Diatomite A variety of shale composed largely of the remains of diatoms (microscopic plants). Common in California, but not in the Sierra Nevada. (See also shale.) Dike A tabular body of igneous rock that cuts across the structure of adjacent rocks or cuts massive rocks. Diorite Rock composed mostly of plagioclase feldspar with less

than half dark minerals and almost no quartz. Usually gray in color. Dock In plate tectonics parlance, to attach fragments of terrane to

an Earth plate. Dolerite A synonym for diabase. (See also diabase.) Dolomite Calcareous rock consisting largely of the mineral dolomite (CaMg(CO3)2). (See also calcareous rock.) Dome A rounded landform or rock mass. Yosemite National Park has many granitic domes, including Half Dome. Dripstone A cave deposit formed by mineral-laden dripping water. Dunite A variety of peridotite consisting almost entirely of the mineral olivine. (See also peridotite.) Earthquake swarm A series of small earthquakes of similar mag-

nitude, no one shock identifiable as the main shock, occurring in a limited area and time. Elastic rebound An elastic recovery from strain. The theory of elastic rebound suggests that increasing strain on rocks on opposite sides of a fault reaches a critical point and the strain is released suddenly, resulting in an earthquake, after which the rocks return to a state of little strain. Epidote-garnet rock Rock consisting mainly of the minerals epidote and garnet. (See also gneiss; schist.) Erosion The process or processes by which rocks, soil, or other objects are worn away. Exfoliation The leafing away of concentric shells of rock.

GLOSSARY

401

Fanglomerate Coarse-grained rock, similar to conglomerate, ex-

cept that the pebbles are more angular. Originally deposited in an alluvial fan. (See also conglomerate.) Fault A fracture or fracture zone along which there has been displacement of the sides relative to one another. Feldspar A group of minerals that are pink to gray to white and

have good cleavage. Feldspars are the most abundant and widespread group of minerals in the Earth’s crust, constituting 60 percent of the crust. Very few rocks do not have feldspar, although it may not be visible to the naked eye. Felsite A general term for a light-colored igneous rock whose grains are too fine to see by the naked eye, but under the microscope is seen to consist of quartz and feldspar. Felsite is sometimes the groundmass for a rock containing larger crystals, making it felsite porphyry. Firn A material transitional between snow and glacier ice. Snow be-

comes firn if it outlasts the summer sun; firn becomes glacier ice when water no longer can percolate through it. Firn line The highest level in a glacier that is not melted by the sum-

mer sun. Fjord A long, narrow arm of the sea, usually in a steep U-shaped valley. Most fjords developed after the last ice of the Great Ice Age melted. California does not have fjords because California glaciers did not reach the sea. Flows, lava See lava. Focus The point within the Earth that is the center of an earth-

quake. Foraminifer A single-celled organism, characterized by a shell con-

taining one to many chambers. Most are very small and live in the ocean. Their ancestors have been on Earth for at least 570 million years. Foreshock A small earthquake that precedes a larger one by sec-

onds or weeks. Scientists can tell it was a foreshock when its record shows that it originated at the same spot in the Earth (focus) as the larger one. (See also aftershock.) Fumarole A vent that emits volcanic fumes.

402

GLOSSARY

Gabbro Coarse-grained, dark-colored plutonic igneous rock consisting principally of plagioclase feldspar and more than half dark minerals, without quartz. Garnet A group of minerals that come in a variety of colors but are often red, are brittle, and have a glassy luster and no cleavage. Commonly found as small crystals in metamorphic rocks. Garnet is the birthstone for January. Because it is hard, it is used as an abrasive. Geologic time scale A chronologic division of geologic time, usu-

ally presented in chart form, with the oldest unit at the bottom. The divisions are arbitrary and were based on fossils and geologic events as recorded in the rocks. Nowadays, it is possible to date many events and rocks in actual years, but nevertheless, the old divisions and names are still used. Geothermal gradient The rate at which Earth gets hotter as the

center is approached. Glacial advance The downslope and forward movement of a gla-

cier. Glacial flour Rock flour, ground up by glacial action. Glacial mill See glacial moulin. Glacial moulin A cylindrical, nearly vertical hole in glacial ice made

by swirling meltwater as it pours down from the surface of the glacier. The meltwater may reach the bottom of the glacier and carve holes in the rock beneath. Glacial polish A smooth surface developed on bedrock by glacial

abrasion. Glacial retreat or recession A decrease in the length or volume of a glacier, usually caused when the rate of melting exceeds the rate at which glacial ice is increased. Glacial tarn A small lake. Many are in the cirques of former gla-

ciers. Glacier A large mass of ice formed on land by the compaction and recrystallization of snow. Glaciers commonly show movement of the ice. California glaciers are all of the “mountain” or “valley” type, born in and restricted to mountains, as opposed to “continental” glaciers, which may cover much of a continent, as ice did the northern parts of North America in the Great Ice Age.

GLOSSARY

403

Glacieret A tiny ice mass less than a quarter of a mile (400 m) in any

dimension. Global tectonics See plate tectonics. Gneiss Coarse-grained, banded metamorphic rock in which layers

of granular minerals alternate with layers of flaky ones. Gold A soft, heavy, malleable, ductile metallic mineral, the native form of the 79th element in the periodic table of elements. It is yellow in color and much sought-after. Graben An elongate area of land bounded by faults. Granite Plutonic igneous rock consisting of visible mineral grains, chiefly quartz and feldspar, with some dark minerals. Usually has a salt-and-pepper look. Granodiorite Plutonic rock, member of the granite family. Gran-

odiorite contains more plagioclase feldspar than true granite and less than tonalite (quartz diorite). (See also granite.) Granophyre A variety of porphyry. (See also porphyry.) Grauwacke Alternate spelling of graywacke. Gravel An unconsolidated accumulation of larger rock particles

and sand. (See also conglomerate.) Gravestone schist A type of schist that may protrude from the ground in Sierran foothills. From a distance, outcrops may resemble tombstones. (See also schist.) Gravestone slate Type of slate that protrudes from the ground in

Sierran foothills. From a distance, outcrops may resemble tombstones. (See also slate.) Graywacke A variety of sandstone. Usually dark colored, with an

assortment of angular mineral and rock fragments. Common in California. (See also sandstone.) Great Ice Age The Pleistocene Epoch (see geologic time scale in text), during which ice covered much of North America. Greenstone Dark, fine-grained metamorphic rock that may be

green owing to the presence of green minerals, but may also be brown, black, or reddish. Derived from basic or ultrabasic igneous rock, particularly basalt.

404

GLOSSARY

Grinding rock A part of the “kitchen” of Native Americans. A rock

used to grind acorns or other nuts to flour. Indian Grinding Rock State Park, near Volcano, preserves a large rock with many holes that was used in this way for many years. Grit A variety of sandstone composed of angular particles. (See also

sandstone.) Hanging valley A tributary glacial valley whose mouth is high above

the floor of the main valley. Hard rock mining The mining of ores contained in igneous or meta-

morphic rock. Helictite A thin cave deposit of unusual shape.Also spelled “helectite.” Hornfels Fine-grained rock in which the grains are not oriented in

one direction. Grains may not be visible under the hand lens, but the rock will not split into thin layers, as do rocks with oriented minerals. Hydraulic giant A device with a nozzle used to direct a stream of water under high pressure. Used in “hydraulicking,” or hydraulic mining. A hydraulic giant resembles a huge fire hose but is often mounted on a swiveling base so that one person can operate it. Also called hydraulic monitor. Hydraulic mining A method of placer mining using a jet of water to wash down a gravel bank. Originally used in gold mining, also used for coal and other minerals. In the Sierra Nevada, thousands of cubic yards of gravel were washed in this way, silting farms and rivers. Hydrothermal deposit An ore deposit resulting from the action of hot water, often heated by a magmatic source. Ice age A time of glaciers. (See also Great Ice Age.) Idocrase A mineral, usually brown, yellow, or green, commonly

found in metamorphosed limestone. Also called vesuvianite. Igneous A term applied to rock or mineral solidified from molten

material (magma). One of the three classes of rock (igneous, sedimentary, metamorphic). Ignimbrite Rock formed from consolidated volcanic ash. (See also

ash.) Inconstant River The old name for California’ s Mojave River.

GLOSSARY

405

Intensity scale A standard of measurement for earthquakes based on the relative amount of destruction and on human experience. The more familiar Richter scale measures magnitude, not intensity. Intrude To emplace magma in preexisting rock. Intrusive suite A group of plutons, related to one another by age,

geography, chemical composition, or all three. Island arc A curved chain of islands near a continent, rising from the seafloor. The Aleutian Islands, Alaska, are an example. Isoseismal line A line connecting points on the Earth’s surface of

equal earthquake intensity. Isotope One of two or more versions of the same chemical element,

having the same number of protons in the nucleus, but different numbers of neutrons. Jade A hard, tough gemstone, most frequently green or white in color. Two varieties are the pyroxene mineral jadeite and the amphibole mineral nephrite. Jade may be found in the Sierra Nevada and elsewhere in California, but “California Jade” is a term for a compact variety of the mineral idocrase. (See also idocrase.) Joint A surface of parting or fracture in a rock, along which there

has been no displacement. Jurassic Period The middle division of the Mesozoic Era. The Jurassic Period is known for its dinosaurs. Because California was undersea during most of the Jurassic, dinosaur fossils are uncommon in California, particularly in the Sierra Nevada. Karst An area underlain by carbonate rocks that have been subject

to solution by groundwater. Springs, sinking streams, sinkholes, and caves are common. Named for the Karst region of eastern Europe. Common in Florida, the Yucatan of Mexico, and China. Not common in the Sierra Nevada. Keratophyre A variety of trachyte, grouped in this book under an-

desite. (See also andesite.) Lahar A mudflow originating from a volcano. Lamprophyre A dark-colored porphyry in which both the large crystals and fine-grained groundmass are dark. (See also porphyry.)

406

GLOSSARY

Lapilli Fragments of pea-sized lava blown from a volcano. (See also

lava; compare cinder.) Laterite A strongly weathered, red, earthy material high in iron and

aluminum. It develops in tropical or warm temperate climates. Bright red soil in the Sierra Nevada is laterite. Laterite hardens after wetting and drying and can be cut into bricks. Angkor Wat and other ancient buildings in Cambodia’s forests are made of laterite. Latite Latite porphyry has large feldspar crystals and a composition similar to andesite. (See also andesite; porphyry.) Lattice The regular and repeated three-dimensional arrangement

of atoms or ions in a crystal. Lava Rock cooled from a molten state on or near the surface of the ground. Lead Pronounced “leed.” A miner’s term for a lode. Lead, South Dakota, was named for the lode of the Homestake mine. (See also lode.) Leucotrondhjemite A member of the granite family. Contains quartz and plagioclase feldspar (oligoclase), with little dark mica (biotite). (See also granite.) Lherzolite A variety of peridotite. (See also peridotite.) Lignite Soft coal, slightly metamorphosed. Limestone Fine-grained calcareous rock made principally of calcium carbonate (CaCO3). Many limestone beds were derived from animal shells or reefs. Limestone in the Sierra Nevada has been metamorphosed. Line of Demarcation A treaty between Spain and Portugal, overseen by the Pope, that divided the unmapped parts of the world (chiefly the New World). Spain could claim lands to the west of the line, Portugal lands to the east. Liparite A synonym for rhyolite. (See also rhyolite.) Lithosphere In plate tectonics, a layer of the Earth that includes the crust and part of the upper mantle. Little Ice Age A time of limited glacial expansion, particularly in

mountain glaciers. The Little Ice Age reached its maximum about

GLOSSARY

407

4,000 to 2,000 years ago. Small glaciers developed not only in the Sierra Nevada, but also in the Alps, Scandinavia, and Alaska. Lizardite A magnesium silicate mineral of the serpentine group. Found as a component of the rock serpentine. Named for its presence at Lizard, Cornwall, England (not for the animal). Load Material that is being moved or carried by a stream. Lode A mineral deposit in solid rock, as opposed to placer deposits. (See also placer.) Magma Molten rock material generated within the Earth. Magma chamber A reservoir of magma within the upper part of the lithosphere, from which volcanoes take their source. Magmatic water Water derived from magma. Magnetite A black, strongly magnetic mineral. An important ore

of iron. Magnitude A measure of the strength of an earthquake, deter-

mined by seismographic methods. Mano Spanish for “hand.” The pestle in a mortar and pestle (i.e., mano and metate). Mantle The zone of Earth below the crust and above the core. The mantle is divided into upper mantle and lower mantle, determined by seismographic methods. Part of the upper mantle and crust constitute the lithosphere. Marble Crystalline, metamorphosed limestone. Because marble has been recrystallized, shiny crystals of calcium carbonate (CaCO3) may show under the hand lens. Mariposite A bright green mica. Mariposite is also a type of schist consisting largely of the mineral mariposite. (See also schist.) Marl Shale that is a mixture of clay and calcium carbonate (CaCO3). Most marl in the Sierra Nevada has been metamorphosed. (See also shale.) Meander One of a series of sinuous curves or loops produced as a stream swings from side to side. Medial moraine A long moraine developed in the middle of a gla-

cier. Often formed where two valley glaciers meet.

408

GLOSSARY

Melaphyre A dark-colored porphyry. (See also porphyry.) Mesozoic Era A range of geologic time that follows the Paleozoic and precedes the Cenozoic Era. Covers a period from about 250 to 65 million years ago. The Mesozoic is the age of the dinosaurs. Because most Mesozoic rocks in California were not deposited on land, California has few dinosaur fossils. Meta- A prefix indicating that rock has been metamorphosed. Rock

names with this prefix can be found listed under the original name, for example, meta-andesite (metamorphosed andesite), see andesite; metarhyolite (metamorphosed rhyolite), see rhyolite. The rock may not be exactly as described under its original name—it has been metamorphosed— but probably will be recognizable. The following “meta” rocks have appeared in reports on the Sierra Nevada: metaarkose, metabasalt, metabreccia, metachert, metaconglomerate, metadacite, metadiabase, metadiorite, metadolerite, metadolomite, metagabbro, metagranite, metagrauwacke, metagraywacke, metaigneous, metakeratophyre, metalamprophyre, metalava, metalimestone, metamudstone, metamelaphyre, metaporphyry, metapyroclastic, metaquartz monzonite, metarhyolite, metasandstone, metasedimentary, metaserpentine, metashale, metasiltstone, metatrap, metatuff, metatuff breccia, metavolcanic flows, metawacke. Metamorphism Literally, change of form. The chemical, mineral-

ogical, and structural adjustment of solid rock to physical and chemical conditions different from those pertaining when the rocks were originally formed. Generally, the change refers to conditions deep within the Earth. Metate New World Spanish for “grinding stone.” Mano and metate

are equivalent to English “pestle” and “mortar.” Mica A group of minerals characterized by perfect basal cleavage; that is, thin sheets will peel off, theoretically down to one molecule. Micas are common rock-forming minerals and are mined for use as insulation and in paint. Black biotite mica weathers to a golden color. Shining in a streambed, it is one of the “fool’s gold” minerals sometimes mistaken for gold, although it is very much lighter in weight. Mid-Atlantic Ridge That part of the midoceanic ridge that extends

through the North and South Atlantic Oceans. (See also midoceanic ridge.) Mid-oceanic ridge A continuous mountain range running through

GLOSSARY

409

the North and South Atlantic (where it is called the Mid-Atlantic Ridge), the Indian, and the South Pacific Oceans. The ridge is a rise, about 3,000 to 10,000 ft (1 to 3 km) high, 930 mi (1,500 km) wide, and 52,000 mi (84,000 km) long. It has a central rift valley and, in plate tectonics theory, is considered the source of new material for the crust of the Earth. Migmatite Rock containing a mixture of igneous and metamorphic rock, often streaked. Mineral A naturally occurring, generally inorganic compound or

element with an orderly internal structure and characteristic chemical composition, physical properties, and crystal form. A few “minerals” do not fit this definition, especially the part requiring crystal form, and are sometimes classed as “mineraloids,” for example, opal. Mineral family An informal designation for minerals of similar chemical composition. Mineral species A mineral with a unique chemical formula and physical properties. Molybdenum A silvery white metallic element, used for electrical and alloying purposes. Monzonite A member of the granite family containing plagioclase

feldspar, orthoclase feldspar, and dark minerals, but very little or no quartz. Commonly darker gray in color than granite, but not as dark as diorite. (See also diorite; granite.) Moraine A hill or ridge of unstratified material deposited by glacial

ice. Mount Joseph The old name for the Sierra Nevada. Mountain glacier A glacier in mountainous terrain. Also called alpine or valley glacier. Mudflow A flowing mass of volcanic ash containing as much as 60

percent water. Volcanic mudflows often start out quite hot but may be cooled by the water in them. Most of the water comes from snow, rain, or rivers. Mudstone Rock consolidated from mud. Does not break into thin layers as true shale does but is otherwise similar. (See also shale.)

410

GLOSSARY

Muscovite A member of the mica group of minerals. Muscovite is

colorless to pale brown and, like other micas, has perfect basal cleavage, splitting into thin sheets. Muscovite in thin transparent sheets is sometimes called isinglass and was formerly used for windows and in fuses. Muscovite is abundant and widespread in rocks and is especially noticeable in pegmatite (see pegmatite), where it may form very large crystals. One single crystal, 10 ft (3 m) in diameter, 15 ft (4.5 m) in length, and weighing 85 tons, came from a mine in India. Mylonite A streaky, banded, fine-grained breccia. Its texture results from pulverization in a fault zone. (See also breccia.) Nevadan Orogeny A time of mountain building, brought about by the movement of Earth plates, that resulted in the formation of the Sierra Nevada and the emplacement of its granitic rock. Norite Dark-colored coarse-grained rock, a close relative of gabbro,

but with a different type of dark mineral (hypersthene). (See also gabbro.) Nuée ardente A rapidly moving gaseous volcanic ash cloud, often incandescent, erupted from a volcano. Obsidian A dark-colored natural glass. Natural glass is formed

when fluid rock is rapidly quenched. Obsidian was the Native Americans’ material of choice for arrowheads, knives, and other sharp instruments. Oceanic plate In plate tectonics, a plate that consists chiefly of rock

formed from magma in the ocean. (Compare continental plate.) Offset The amount that rock strata have been separated from one

another across a fault, especially following an earthquake. Offset is the horizontal component measured parallel to the strike of the fault. Opdalite A member of the granite family, related to diorite. (See

also diorite; granite.) Ophiolite In plate tectonics, a series of dark-colored igneous rocks,

ranging from basalt to peridotite, including rocks rich in serpentine, as well as layers of chert and sometimes limestone. Ophiolite is formed in the deep sea. Ore Naturally occurring rock material from which valuable miner-

als or metals can be won.

GLOSSARY

411

Ore shoot An elongate mass of ore within a deposit, usually repre-

senting the more valuable part of the deposit. Orthoquartzite A variety of sandstone. Orthoquartzite in the Sierra Nevada has been metamorphosed. (See also sandstone.) Paleozoic Era A major division of geologic time, extending from about 542 to 251 million years ago. (See geologic time scale in text.) Pangea A hypothetical former supercontinent, embracing all the continents of Earth. As Pangea broke up, owing to plate movement, modern continents were formed. Pay streak In mining, an area of concentration of ore in placer de-

posits. Also, that portion of a vein that carries profitable ore. Peat Unconsolidated deposit of decomposed plant remains; the

initial stage in the development of coal. Peat is common in the Central Valley of California. Pegmatite A very coarse-grained igneous rock. Can be any compo-

sition, but most pegmatite has the same mineral composition as granite. (See also granite.) Pelton wheel A water turbine used in mining, which has buckets mounted to its periphery. The buckets were struck by a high-velocity jet of water, forcing the wheel to rotate and thereby provide power. Peneplain A surface of land made nearly level by processes of ero-

sion. Peridotite An igneous, plutonic, coarse-grained, ultramafic rock,

composed of dark minerals, with no quartz and little or no feldspar. Perlite Natural volcanic glass, usually cracked into tiny round

beads. Permafrost A soil, subsoil, or other deposit, even sometimes bedrock, at a variable depth, that in the Arctic or subarctic regions is permanently below freezing and has been frozen continuously for a long time. Thickness of the permafrost layer is from about 10 ft (3 m) in the south to more than 3,000 ft (1,000 m) in the north. About onefifth of the Earth’s land area is underlain by permafrost. Phenocryst A relatively large, conspicuous crystal set in a finergrained groundmass, as in a porphyry. (See also porphyry.) Phreatic zone The zone of saturation below the water table.

412

GLOSSARY

Phthanite An old name for chert. (See also chert.) Phyllite Silky metamorphic rock that is layered. Pillow lava Lava that has cooled into discontinuous pillow shapes. Pillow lava may form when lava flows into water. Placer A place where valuable minerals can be obtained by wash-

ing, especially alluvial or glacial deposits. Under mining law, virtually every deposit that is not a vein or lode deposit is considered placer. Plate tectonics Tectonics of the whole Earth (global tectonics)

that envisions Earth having a number of large plates and many small ones, each composed of blocks of continental and/or oceanic crust and mantle. The plates move on a viscous underlayer in the mantle. The continents are part of the plates and move with them. Plucking A process of glacial erosion by which blocks of rock are loosened by freezing and thawing and moved downhill by ice. Pluton A body of igneous rock, smaller than a batholith. Plutonic rock Igneous rock formed by crystallization of magma or

by chemical alteration. Porphyrite Same as porphyry. Porphyry An igneous rock that has large mineral crystals (pheno-

crysts) in a fine-grained matrix. Potassium-argon method A method of determining the age of a

rock in actual years by utilizing the radioactive decay rate of the isotope of potassium-40 to argon-40. Propylite Andesite that has been altered by hot water. (See also an-

desite.) Pumice Light-colored, glassy volcanic rock buoyant enough to float

on water. Pyrite A common mineral, composed of iron sulfide (FeS2). Pyrite

has a brass yellow color and bright metallic luster. It is one of the “fool’s gold” minerals, but it is lighter and harder than gold. Pyrite crystallizes in neat little cubes. Pyroclastic rock Rock made of fragments blown from a volcano. Pyroxene A group of dark, closely related minerals, common constituents in igneous rocks.

GLOSSARY

413

Pyroxenite A member of the peridotite rock family, consisting principally of the mineral pyroxene. (See also peridotite.) Quarrying A process of glacial erosion similar to plucking. Quartz An important rock-forming mineral. Quartz is colorless

and transparent when it has no impurities, has a conchoidal fracture, vitreous luster, and no cleavage, and forms tidy crystals. Other minerals have the same chemical composition (silicone dioxide), but no crystalline structure. Quartz is the principal ingredient in most sand. Quartz diorite A coarse-grained member of the granite family related to diorite but containing quartz. The name quartz diorite has been replaced by tonalite by vote of an international committee. (See also diorite; granite; tonalite.) Quartz latite Medium-gray igneous rock with a fine-grained groundmass and large crystals of quartz. A porphyry. Synonym of rhyodacite. (See also porphyry.) Quartz mining The mining of veins or ore bodies in place. Also, hard-rock mining. Called “quartz mining” because quartz is the chief mineral associated with gold in hard-rock deposits. Quartz monzonite Member of the granite family, with considerable

feldspar (both orthoclase and plagioclase) and quartz, with some dark minerals. Rock with less plagioclase feldspar is called granite; with more, granodiorite. Quartz vein A vein composed chiefly of quartz. Quartzite A metamorphosed sandstone or chert. Quaternary Period The second period of the Cenozoic Era, including the Great Ice Age (Pleistocene Epoch) and the Holocene Epoch. The Quaternary Period began about two million years ago; the Holocene Epoch commenced about 10,000 years ago. We are still in the Holocene Epoch. Radioactive dating Calculation of the age in years for geologic materials by measuring the presence of a short-life radioactive element (e.g., carbon-14) or a long-life radioactive element plus its decay product (e.g., potassium-40 to argon-40). Radiolarian A tiny organism living in the sea characterized by a

siliceous skeleton (made of silica, SiO2). Radiolarians have existed since Cambrian times (542 million years ago).

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GLOSSARY

Raise A shaft driven upward vertically, or nearly so, to connect one

level of a mine to the next above. At times raises are driven to explore the ground above and may not connect with the next level. Recessional moraine An end moraine of a glacier built during a

pause in the glacier’s final retreat. Retreat A decrease in the length of a glacier, resulting when the amount of calving and melting exceeds the speed of ice flow. Rhyodacite A variety of latite. (See also latite.) Rhyolite A fine-grained, light-colored member of the granite fam-

ily. Rhyolite tuff Consolidated volcanic ash having the chemical com-

position of rhyolite. (See also ash.) Richter scale A numerical scale of earthquake power, based on seismic records. The scale extends from 1 to 10, but there can be small earthquake events below 1, giving them a negative value, and although the upper end has no theoretical limit, the strength of Earth materials makes the practical upper limit slightly less than 9. Rift valley A valley that has developed along a long, narrow continental trough bounded by faults (rift). The central trough in the midocean ridge is a rift valley, so are the African Rift Valley and the Rio Grande Valley in New Mexico. Ring of Fire A zone of volcanoes and earthquake epicenters that

rims the Pacific Ocean. Roche moutonnée A knob of bedrock, sculpted by a glacier. The

long axis of a roche moutonnée is oriented in the direction of ice movement. The upstream (stoss) side of the knob is gently inclined, smoothly rounded, and striated; the downstream (lee) side is steep, rough, and hackly.Yosemite National Park has many roches moutonnées. Rock glacier A mass of rock rubble with interstitial ice or an ice

core. Rock glaciers move like ice glaciers and resemble small valley glaciers. Rödingite Variety of gabbro. (See also gabbro.) Roof pendant A downward projection of country (local) rock into

an igneous body. A magma “chamber” was originally conceived of as

GLOSSARY

415

essentially a large pot covered by local rock—in the Sierra Nevada, the old metamorphic rock. Where all of the old rock was not digested in the more fluid intrusion, a few chunks remain and were thought of as hanging downward into the intrusion, as on a necklace, hence the “pendant.” Rubidium-strontium method A method for determining the age of rocks in years, based on the ratio of radioactive strontium-87 and the known radioactive decay rate of rubidium-87. Sandstone Medium-grained rock consisting of particles of rock or minerals cemented together by a natural glue (iron oxide, silica, calcium carbonate). Saxonite A variety of peridotite. (See also peridotite.) Scarp A line of cliffs produced by faulting or erosion (abbreviated

from “escarpment”). Schist Metamorphosed crystalline rock that splits readily into

flakes or slabs. Most grains are large enough to be seen easily. Scoria A vesicular crust on the surface of lava flows. Heavier and

darker than pumice. (See also pumice.) Seiche An oscillation of a body of water in an enclosed basin.

Caused by changes in atmospheric pressure, but also occasionally by earthquakes. Seismic Pertaining to earthquakes or earthquake vibrations. Seismograph An instrument that records seismic waves. A seismo-

gram is the record made by a seismograph; a seismometer detects seismic waves but does not record them. Serpentine Both a rock (also called serpentinite) and a mineral.

Green to black rock, greasy appearing. May contain fibers of asbestos. Commonly formed from alteration of ultramafic igneous rock. Serpentinite See serpentine. Shale Fine-grained sedimentary rock, derived from the compaction of clay, silt, or mud, characterized by its tendency to break into thin layers. Sheeting A type of jointing produced by pressure release. Sheeting produces slabs of rock shaped like the mass from which they came. In

416

GLOSSARY

Yosemite National Park, curved rock slabs were produced by exfoliation acting on rock sheets. Shield A semicircular sheet formed by seeping water in a cave. Siltstone Sedimentary rock derived from the compaction of dust-

sized particles (silt). Similar to shale. (See also shale.) Sinkhole A funnel-shaped depression in the ground in karst regions. Sinkholes can be very large and sometimes open unexpectedly. Skarn Metamorphic rock derived from the metamorphosis of calcareous rock to which has been added considerable silica (SiO2). Slate Fine-grained metamorphic rock that commonly will split

into layers. Grains are too fine to be seen with a hand lens. Most slate has a shiny surface. Snout The lower end of a glacier. Soapstone Soft metamorphic rock with an “unctuous” feel, composed mostly of talc. May be schist, phyllite, or slate in texture. (See also phyllite; schist; slate.) Sonoma Orogeny A mountain-building episode beginning about 220 million years ago that involved the future Sierra Nevada. Sonomia A terrane that reached from the Sonoma Range in Nevada to the Sierran foothills. The Sonomia Terrane docked against western North America at the end of Permian time (about 250 million years ago). Remnants of the Sonomia Terrane are in basement rock of the eastern Klamath Mountains and northern Sierra Nevada. (See also terrane.) Speleothem A decorative deposit within a cave formed after air enters the cavern. Usually calcite, but some are aragonite or gypsum. Stalactite A cave deposit that generally grows down from the ceil-

ing. Stalagmite A cave deposit that grows upward from the cave floor

or ledge when mineral-laden water drips on it. Stamp A heavy pestle raised and dropped to crush ore. Strata Layers of rock. Strike The direction taken by a bedding plane or fault plane as it intersects the horizontal.

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417

Strike-slip fault A fault in which the movement has been parallel to

the fault’s strike. Subduction The concept that one lithospheric plate descends be-

neath another. Subduction zone A long, narrow zone where subduction takes

place. Subjacent Series All Mesozoic and Paleozoic igneous and metamorphic rocks in the Sierra Nevada. Now obsolete. Superjacent Series All sedimentary and volcanic rocks deposited on top of the granitic and metamorphic rock (Subjacent Series) in the Sierra Nevada. Now obsolete. Syenite Member of the granite family. Contains orthoclase

feldspar, some plagioclase feldspar, and dark minerals, but very little or no quartz. (See also granite.) Tactite Calcareous rock metamorphosed in a contact zone and chemically changed. (See also calcareous rock; skarn.) Tailing A pile of washed or milled ore that is too poor to be treated

further. Miners commonly call it tailings. Talus Rock fragments, usually coarse and angular, lying at the foot

of the cliff or steep slope from which they came. Tectonics Dealing with the broad architecture of the outer part of

the Earth. Tellurium A nonmetallic chemical element. One of the few elements

that combines with gold. Temperate glacier A “warm” glacier, characteristic of the temper-

ate zone. Almost all glaciers presently in the Alps, Scandinavia, and south of northern Alaska are temperate glaciers, including the small ones in the Sierra Nevada. Tephra A general term for all fragments blown from a volcano. Terminal moraine The outermost end moraine of a glacier, mark-

ing the farthest advance of the ice. Terrane A three-dimensional slice of Earth’s land, together with the underlying seafloor and a fragment of Earth’s mantle.

418

GLOSSARY

Tertiary Period The first period of the Cenozoic Era. (See geological

time scale in text.) Theodolite A surveying instrument used for measuring horizontal

and vertical angles. Thinolite A variety of calcite, found in the tufa towers of Mono

Lake. (See also calcite.) Till A mixture of boulders and fine fragments left by glaciers or gla-

cier streams. Tillite Consolidated rock formed of till. (See also till.) Time scale See geologic time scale. Tombstone rock Nearly vertical outcroppings of metamorphic rock in the foothills of the Sierra. From a distance, a group of outcroppings may resemble a cemetery. Also called gravestone slate, gravestone schist. Tonalite A variety of diorite composed of plagioclase feldspar and dark mineral — usually hornblende — with considerable quartz. Same as quartz diorite. (See also diorite.) Transform fault A strike-slip fault along which displacement sud-

denly stops or changes form. (See also strike-slip fault.) Trap Dark-colored, fine-grained volcanic rock. Generally basalt.

(See also basalt.) Trench In plate tectonics, a long, narrow, steep-sided depression in the deep-sea floor. A trench may be a mile deeper than the surrounding ocean floor, and some are thousands of miles long. Trenches are considered to be sites where subduction takes place. Troctolite A variety of gabbro. (See also gabbro.) Trondhjemite A member of granite family, similar to granite, ex-

cept that it contains plagioclase feldspar and very little or no orthoclase feldspar. (See also granite.) Tufa Calcareous rock formed around a hot spring. Early geologic re-

ports sometimes used tuff and tufa interchangeably. Modern use restricts tuff to volcanic ash and tufa to hot spring deposits. Tufaceous refers to tufa; tuffaceous to tuff.

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419

Tufa towers Calcareous spring deposits developed in a lake. Mono Lake has many. Also called tufa domes. Tuff Consolidated volcanic ash. Tuff may be mixed with clay, sand,

or pebbles. Because it is usually deposited in layers (dropping from the air onto the ground or into water bodies), it is, in a sense, sedimentary. (See also ash.) Tungsten A metallic element, white and ductile when pure. Be-

cause it has the highest melting point of any metal, it is used for lightbulb filaments, for alloying steel, and in space enterprises. Turbidity current A density current; a bottom-flowing current

laden with suspended sediment, moving swiftly down an underwater slope. Ultramafic Refers to igneous rocks composed chiefly of minerals

rich in iron and magnesium. Unconformity A break or gap in the geologic rock record. Uranium-lead method A method of determining a rock’s age in years based on the known rate of radioactive decay of uranium-238 to lead-206, or uranium-235 to lead-207. Valley glacier A mountain glacier or alpine glacier. (See also moun-

tain glacier.) Varve A layer or layers deposited in a lake in one year’s time. Varves are generally in pairs, with a light-colored summer layer and a darkcolored winter layer. Varves may be used to count years. Vein A mineral filling of a fracture in a rock. Veins are common in

igneous rock. A few are hosts for ore deposits. Vesuvianite See idocrase. Volcanic ash See ash; tuff. Volcanic dome A dome-shaped mountain formed of many lava

flows. Volcanic mudflow See mudflow. Volcano A vent in Earth’s surface that expels magma, gases, and ash. Wacke A type of sandstone. (See also sandstone.)

420

GLOSSARY

Water table The level below which the ground is saturated with

water. Below the water table is the phreatic zone, and above the vadose zone. Wehrlite A variety of peridotite. (See also peridotite.) Winze A vertical or inclined opening connecting two levels in a mine, as does a raise. When one is beneath the opening, it is called a raise; when above, a winze.

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421

SUGGESTIONS FOR FURTHER READING

General Blake, M. C., Jr., and D. S. Harwood, eds. 1989. Tectonic evolution of northern California, Sausalito to Yosemite National Park, California. 28th International Geological Congress Field Trip Guidebook T108. Washington, D.C.: American Geophysical Union. Brewer, William H. 1974. Up and down California in 1860–1864: The journal of William H. Brewer, Professor of Agriculture in the Sheffield Scientific School from 1864 to 1903. Repr., Berkeley and Los Angeles: University of California Press. (Orig. pub. 1930.) Burnett, John L. 1971. Geology of Lake Tahoe Basin. California Geology 24(7):119–127. Photos, maps. Burnett, John L., and Robert A. Matthews. 1971. Geological look at Lake Tahoe [Field-trip log]. California Geology 24(7):128–129. Calkins, F. C. 1985. Bedrock geology of the Yosemite Valley area, Yosemite National Park, California. With an accompanying pamphlet by N. King Huber and Julie A. Roller. U.S. Geological Survey Miscellaneous Investigations Series. Map I-1639. Despain, Joel. Crystal Cave: A guidebook to the underground world of Sequoia National Park. Three Rivers, Calif.: Sequoia Natural History Association. Dupras, Don L. 1985. Sharktooth Hill. California Geology 38(7): 147–154. Durrell, Cordell. 1987. Geologic history of the Feather River country, California. Berkeley and Los Angeles: University of California Press. Farquhar, Francis P. 1966. History of the Sierra Nevada. Berkeley and Los Angeles: University of California Press.

423

Gaines, David. 1989. Mono Lake guidebook. 4th ed. Rev. by Lauren Davis. Lee Vining, Calif.: Kutsavi Books. Guyton, Bill. 1998. Glaciers of California. Berkeley and Los Angeles: University of California Press. Hill, Mary. 1999. Gold: The California story. Berkeley and Los Angeles: University of California Press. Huber, N. King, and Wymond W. Eckhardt. 1985. Devils Postpile story. Three Rivers, Calif.: Sequoia Natural History Association. Huber, N. K., and C. D. Rinehart. 1965. Geologic map of the Devils Postpile quadrangle, Sierra Nevada, California. U. S. Geological Survey Quadrangle Map GQ-437. Huber, N. King, Paul C. Bateman, and Clyde Wahrhaftig. 1989. Geologic map of Yosemite National Park and vicinity, California. U.S. Geological Survey Map I-1874. Jennings, Charles W. Various dates. Geologic map of California. Compiled Charles W. Jennings. Sacramento, Calif.: California Division of Mines and Geology. These maps cover the Sierra Nevada: Westwood (Susanville), Sacramento, Walker Lake, San Jose, Mariposa, Fresno, Bakersfield, and tiny parts of Death Valley, Los Angeles, and Trona. Kious, Jacquelyne, and Robert I. Tilling. n.d. This dynamic Earth: The story of plate tectonics. U.S. Geological Survey. Konigsmark, Ted. 2002. Geologic trips: Sierra Nevada. Gualala, Calif.: GeoPress. Le Conte, Joseph. 1971. A journal of ramblings through the High Sierra of California by the University Excursion Party. New York: Sierra Club, Ballantine Books. (Orig. pub. 1875.) Matthes, François. 1950. Sequoia National Park: A geological album. Ed. Fritiof Fryxell. Berkeley and Los Angeles: University of California Press. Matthes, François. 1950. The incomparable valley. Ed. Fritiof Fryxell. Berkeley and Los Angeles: University of California Press. McPhee, John. 1992. Assembling California. New York: Farrar, Straus, and Giroux. Miller, C. D. 1989. Potential hazards from future volcanic eruptions in California. U.S. Geological Survey Bulletin 1847. Moore, James G. 2000. Exploring the highest Sierra. Stanford, Calif.: Stanford University Press. Muir, John. 1960. John Muir’s studies in the Sierra. Ed. William E. Colby. San Francisco: Sierra Club. A republication of his articles in the Overland Monthly in 1874 and 1875.

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SUGGESTIONS FOR FURTHER READING

Muir, John. 1961. The mountains of California. Garden City, N.J.: Doubleday. (Orig. pub. 1894.) The first of his work to be published as a book. Putman, Jeff, and Genny Smith, eds. 1995. Deepest valley: Guide to Owens Valley, its roadsides, and mountain trails. 2nd ed. Mammoth Lakes, Calif.: Genny Smith Books. Russell, Israel C. 1889. Quaternary history of Mono Valley, California. In U.S. Geological Survey Eighth Annual Report, 1886–1887, 267–394. Schweickert, R. A. 1985. The northern Sierra Nevada. In Guidebook to the northern Sierra Nevada and Reno–Lake Tahoe, ed. J. R. Firby. Reno: MacKay School of Mines, University of Nevada at Reno. Short, Harry W. 1975. The geology of Moaning Cave, Calaveras County, California. California Geology 28:195–201. Smith, Genny, ed. 1989. Mammoth Lakes Sierra: A handbook for roadside and trail. 5th ed. Mammoth Lakes, Calif.: Genny Smith Books. Smith, Genny, ed. 2000. Sierra east: Edge of the Great Basin. Berkeley and Los Angeles: University of California Press. Of particular interest are “Geologic Story” (pp. 37–69) and “Water” (pp. 450– 463). Solnit, Rebecca. 1999. Savage dreams: A journey into the landscape wars of the American West. Berkeley and Los Angeles: University of California Press. Tierney, Timothy. 1995. Geology of the Mono Basin. Lee Vining, Calif.: Kutsavi Press. Tilling, Robert I., Roy A. Bailey, and C. Dean Rinehart. Forthcoming. Earthquakes and young volcanoes along the eastern Sierra Nevada. Mammoth Lakes, California: Genny Smith Books. Twain, Mark. 1931. Roughing it. New York: Grosset and Dunlap. (Orig. pub. 1871.) Whitney, Josiah D. 1869. The Yosemite guide-book. Philadelphia: California Geological Survey. (Orig. pub. 1868 as The Yosemite book.) Willkins, Thurman. 1958. Clarence King: A biography. New York: Macmillan. About Long Valley Bailey, Roy A. 1989. Geologic map of the Long Valley Caldera, MonoInyo Craters volcanic chain, and vicinity, eastern California. U.S. Geological Survey Map I-1933. Bailey, Roy A. 1989. Long Valley Caldera and Mono-Inyo Craters vol-

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canic chain, eastern California. Memoir 47, Excursion 13B P 227254. Socorro, N.M.: New Mexico Bureau of Mines and Mineral Resources. Ewart, John W., and Christopher J. Harpel. 2000. Bibliography of literature pertaining to Long Valley Caldera and associated volcanic fields. U.S. Geological Survey Open File Report 00-221.

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QUOTATION REFERENCES

Adams, Henry. 1999. The education of Henry Adams. Ed. Ira B. Nadel. Oxford: Oxford University Press. Brewer, William H. 1966. Up and down California in 1860–1864: The journal of William H. Brewer. 3rd edition. Ed. Francis P. Farquhar. Berkeley and Los Angeles: University of California Press. Egenhoff, Elisabeth L. 1967. The Cornish pump. California Geology 20, 59–71, 91–97. Farquhar, Francis P. 1965. History of the Sierra Nevada. Berkeley and Los Angeles: University of California Press. Gaines, David. 1989. Mono Lake guidebook. 4th ed. Revised by Lauren Davis. Lee Vining, Calif.: Kutsavi Books. Guyton, Bill. 1998. Glaciers of California. Berkeley and Los Angeles: University of California Press. Hill, Mary. 1953. Personal communication. Hill, Mary, ed. 1972. California Geology 25(3). Hittell, John S. 1858. Mineral resources of California. San Francisco: A. L. Bancroft. Huber, N. King. 1987. The geologic story of Yosemite National Park. U.S. Geological Survey Bulletin 1595. Hutchings, J. M. 1871. Scenes of wonder and curiosity in California, illustrated with over one hundred engravings: A tourist’s guide to the Yosemite Valley. New York: A. Roman. Johnson, Willard D. 1904. The profile of maturity in alpine glacial erosion. Journal of Geology. 12:569–578. Johnston, Verna R. 1998. Sierra Nevada: The naturalist’s companion. Rev. ed. Berkeley and Los Angeles: University of California Press. King, Clarence. 1878. Systematic geology. Washington, D.C.: Government Printing Office. King, Clarence. 1970. Mountaineering in the Sierra Nevada. Lincoln: University of Nebraska Press.

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King, Thomas Starr. 1962. A vacation among the Sierras: Yosemite in 1860. Ed. John Adam Hussey. San Francisco: Book Club of California. (Orig. pub. 1860.) Available at www.yosemite.ca.us/his tory/vacation_among_the_sierras. Accessed July 2005. Le Conte, Joseph. 1971. A journal of ramblings through the High Sierra of California. New York: Sierra Club, Ballantine Books. (Orig. pub. 1875.) Matthes, François. 1950. The incomparable valley. Ed. Fritiof Fryxell. Berkeley and Los Angeles: University of California Press. Muir, John. 1871. Yosemite glaciers. New York Tribune, December 5. Muir, John. 1872. Living glaciers of California. Overland Monthly, vol. 9, 547–549. Muir, John. 1901. Our national parks. Boston: Houghton, Mifflin. Muir, John. 1961. The mountains of California. Garden City, N.Y.: Doubleday. (Orig. pub. 1894.) Muir, John. 1988. The Yosemite. San Francisco: Sierra Club Books. (Orig. pub. 1912.) Raub, W. D., Austin Post, C. S. Brown, and Mark F. Meier. 1980. Perennial ice masses of the Sierra Nevada, California, world glacier inventory. In Proceedings of the International Association of Hydrological Science, Publication No. 126, 33–34. Roosevelt, Theodore. 1915. John Muir: An appreciation. Outlook, January 16, 27–28. Russell, Israel C. 1889. The quaternary history of Mono Vally, California. In U.S. Geological Survey Eighth Annual Report, 1886– 1887, 267–394. Sierra Club. 2003. The importance of John Muir. In John Muir Exhibit. www.sierraclub.org/john_muir_exhibit/frameindex.html? http://www.sierraclub.org/john_muir_exhibit/john_muir_ national_historic_site/the_importance_of_john_muir.html. Accessed July 2005. Smith, Genny. 2000. Water. In Sierra east: Edge of the Great Basin, 450–463. Berkeley and Los Angeles: University of California Press. Twain, Mark. [1913?]. Roughing it. New York: Grosset and Dunlap. (Orig. pub. 1872.) Tyndall, John. 1872. Forms of water in clouds and rivers, ice and glaciers. New York: D. Appleton. Whitney, Josiah Dwight. 1869. Yosemite book: A description of the Yosemite Valley and the adjacent region of the Sierra Nevada, and the big trees of California. New York: J. Bien.

428

Q U O TAT I O N R E F E R E N C E S

Whitney, Josiah Dwight. 1871. The Yosemite guide-book: A description of the Yosemite Valley and the adjacent region of the Sierra Nevada, and of the big trees of California. Cambridge, Mass: University Press, Welch Bigelow. Whitney, Josiah Dwight. 1882. The climatic changes of later geologic times. In Contributions to American geology, vol. 2. Cambridge, Mass.: Museum of Comparative Geology. Wilkins, Thurman. 1958. Clarence King: A biography. New York: Macmillan.

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FIGURE REFERENCES

Fig. 1. Bill Nelson. Fig. 2. After Mary Hill, Geology of the Sierra Nevada, 1st ed. (Berkeley and Los Angeles: University of California Press, 1975), 5. Original drawing by Adrienne E. Morgan. Fig. 3. Revised from Geological Society of America, 1999 Geological Time Scale. Fig. 4. From Hill, Geology of the Sierra Nevada, 13. Original drawing by Adrienne E. Morgan. Fig. 5. After Hill, Geology of the Sierra Nevada, 14. Fig. 6. François Matthes, Geologic History of the Yosemite Valley, U.S. Geological Survey Professional Paper 160 (1930). Fig. 7. After Genny Smith, ed., Sierra East: Edge of the Great Basin (Berkeley and Los Angeles: University of California Press, 2000), 451. Original map by Annie Kook. Fig. 8. Stasia Wolfe. Courtesy of the Sacramento Archives and Museum Collection Center. Fig. 9. From J. M. Hutchings, Scenes of Wonder and Curiosity in California, Illustrated with over One Hundred Engravings: A Tourist’s Guide to the Yosemite Valley (New York: A. Roman, 1871), 175. Fig. 10. From Hutchings, Scenes of Wonder, 105. Fig. 11. Courtesy of the Bancroft Library/University of California, Berkeley. Fig. 12. From Hutchings, Scenes of Wonder, 164. Fig. 13. Courtesy of the Bancroft Library/University of California, Berkeley. Fig. 14. Courtesy of the Bancroft Library/University of California, Berkeley. Fig. 15. Courtesy of the Bancroft Library/University of California, Berkeley.

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Fig. 16. Modified from James G. Moore, Exploring the Highest Sierra (Stanford, Calif.: Stanford University Press, 2000), 26. Fig. 17. T. H. O’Sullivan. Courtesy of the Bancroft Library/University of California, Berkeley. Fig. 18. J. Georgi. Courtesy of the Alfred Wegener Institute for Polar and Marine Research. Fig. 19. After Jacquelyne W. Kious and Robert I. Tilling, This Dynamic Earth: The Story of Plate Tectonics (Washington, D.C.: U.S. Geological Survey, 1996), 4. Also available online: http://pubs .usgs.gov/publications/text/dynamic.html. Fig. 20. After Kious and Tilling, This Dynamic Earth, 2. Fig. 21. After Kious and Tilling, This Dynamic Earth, 15. Fig. 22. After Kious and Tilling, This Dynamic Earth, 18. Fig. 23. After Kious and Tilling, This Dynamic Earth, 30. Fig. 24. After Kious and Tilling, This Dynamic Earth, 38. Fig. 25. After Kious and Tilling, This Dynamic Earth, 54. Fig. 26. After Kious and Tilling, This Dynamic Earth 56. Fig. 27. After Hill, Geology of the Sierra Nevada, 50. Original drawing by Alex Eng. Fig. 29. After Hill, Geology of the Sierra Nevada, 56. Original drawing by Alex Eng. Fig. 30. After Hill, Geology of the Sierra Nevada, 57. Original drawing by Ed Foster. Fig. 31. After Jeff Putnam and Genny Smith, eds., Deepest Valley: A Guide to Owens Valley, Its Roadsides and Mountain Trails, 2nd ed. (Mammoth Lakes, Calif.: Genny Smith Books, 1995), 142–143. Original drawing by Paul Bateman. Fig. 32. Mary Hill. Fig. 33. After N. King Huber, The Geologic Story of Yosemite National Park, U.S. Geological Survey Bulletin 1595 (1987), 20. Fig. 34. After Huber, The Geologic Story, 21. Fig. 35. After Hill, Geology of the Sierra Nevada, 70. Original drawing by Ed Foster. Fig. 36. Mary Hill. Fig. 37. After Putnam and Smith, Deepest Valley, 139. Fig. 38. After Jeffrey P. Shaffer et al. 1995. The Pacific Crest Trail, vol. 1, California. (Berkeley, Calif.: Wilderness Press), frontispiece. Fig. 39. After California Geology (September 1983): 187. Fig. 40. Courtesy of the California State Library. Fig. 41. After Hill, Geology of the Sierra Nevada, 86. Original drawing by Alex Eng.

432

FIGURE REFERENCES

Fig. 42. Eleanor McClatchy. Sacramento Archives and Museum Collection Center. Fig. 43. Mary Hill. Fig. 44. Mary Hill, Gold: The California Story (Berkeley and Los Angeles: University of California Press, 1999), 107. Original map by Bill Nelson. Fig. 45. From Hill, Geology of the Sierra Nevada, 92–93. Drawing by Alex Eng. Fig. 46. Courtesy of the Oakland Museum of California. Gift of Louis L. Stein. Fig. 47. From Hill, Geology of the Sierra Nevada, 106–107. Drawing by Alex Eng. Fig. 48. After Smith, ed., Sierra East, 56. Modified by Annie Kook; after Roy Bailey, Geologic Map of the Long Valley Caldera, MonoInyo Craters Volcanic Chain, and Vicinity, Eastern California (Washington, D.C.: U.S. Geological Survey, 1989), Map I-1933. Fig. 49. From Hill, Geology of the Sierra Nevada, 110. Original drawing by Alex Eng; after G. H. Heiken, Geological Society of America Bulletin, 83 (January 1972): 96. Fig. 50. From Hill, Geology of the Sierra Nevada, 109. Drawing by Alex Eng. Fig. 52. After W. C. Putnam, The Geographical Review (1938). Fig. 53. From W. M. Davis, Scottish Geographical Magazine (1906). Fig. 54. Mary Hill. Fig. 55. After Hill, Geology of the Sierra Nevada, 132. Original drawing by Alex Eng. Fig. 56. Courtesy of the Bancroft Library, University of California, Berkeley. Fig. 57. From Hutchings, Scenes of Wonder, 144. Fig. 58. From J. D. Whitney, Geology: Report of Progress and Synopsis of Field Work from 1860 to 1864, vol. 1 (Sacramento: Geological Survey of California, 1865), plate L. Fig. 59. Courtesy of the Bancroft Library/University of California, Berkeley. Fig. 60. From Hutchings, Scenes of Wonder, 170. Fig. 61. Courtesy of the Bancroft Library/University of California, Berkeley. Fig. 62. From Matthes, Geologic History. Fig. 63. From Matthes, Geologic History. Fig. 64. After Matthes, Incomparable Valley. Fig. 65. Mary Hill.

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Fig. 66. From Hutchings, Scenes of Wonder, 140. Fig. 67. After Hill, Geology of the Sierra Nevada, 167. Original drawing by Adrienne Morgan; modified from State of California Preliminary Fault and Geologic Map, scale 1:750,000 by Charles W. Jennings, California Division of Mines and Geology, Preliminary Report 13 (1974). Fig. 68. From Inyo Independent, 1872. Fig. 69. From Dean C. Rinehart and Ward C. Smith, Earthquakes and Young Volcanoes (Palo Alto, Calif.: Genny Smith Books, 1982), 15. Fig. 70. After California Geology, 1972. Original drawing by Ron Morgan. Fig. 71. From Rinehart and Smith, Earthquakes and Young Volcanoes, 14. Fig. 72. From Doris Sloan, Geology of the San Francisco Bay Region (Berkeley and Los Angeles: University of California Press, 2006), 34. Fig. 73. From Hutchings, Scenes of Wonder, 108.

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FIGURE REFERENCES

PLATE CREDITS

STEVEN ALTER

44

R. A. BAILEY, COURTESY OF THE U.S. GEOLOGICAL SURVEY

81, 82

PETER BOSTED

14, 15, 16, 17, 18, 63

LARRY CARVER

display on pages 60–61, 76–77, 148–149, 210–211

CAROLINE W. COLEMAN

63

ED COOPER PHOTOGRAPHY MIKE DIGGLES

40, 42, 52, 58, 60

31, 72, 84

JOHN DITTLI 2, 6, 10, 12, 13, 32, 34, 36, 43, 46, 48, 49, 53, 61, 62, 67, 71, 87, 89. Also display on pages x–xi STEPHANIE S. FERGUSON WILLIAM E. FERGUSON

4

8, 20, 21, 23, 27, 28, 30, 38, 41, 54, 55, 65, 66,

76, 85, 86, 96 CHRISTOPHER TALBOT FRANK

79

EDWIN HARP, COURTESY OF THE U.S. GEOLOGICAL SURVEY

91, 93,

94, 95 MARY HILL

5, 47, 50, 56, 57, 77, 78, 88, 90

RICHARD KATTELMANN QUANG-TUAN LUONG

display on pages 288–289

display on pages ii–iii

C. D. MILLER, COURTESY OF THE U.S. GEOLOGICAL SURVEY GERALD L. MOORE SUSAN MOYER

80

9, 74. Also display on pages 334–335

3, 24, 45

435

E. G. RANGE

37

THOMAS J. STORY IAN TAIT

22, 25, 26a–f

display on pages 176–177

GAIL TAUCHUS

19, 31

U.S. GEOLOGICAL SURVEY JOHN WAKABAYASHI

11

JOSEPH WAKABAYASHI JIM WARK /AIRPHOTO STEPHEN WEAVER

97

35, 68, 69, 70, 92 7, 64

1, 29, 33, 51, 59, 73, 75, 83

CHARLES WEBBER/CALIFORNIA ACADEMY OF SCIENCES

436

P L AT E C R E D I T S

39

INDEX

accretion, 154–155 acid volcanoes, 262 acorns, in Native American diet, 97, 100, 101 (plate) Adams, Henry, 124, 127 aftershocks, of Owens Valley earthquake, 377 Agassiz, Louis, 348–349 Alabama Hills fault line scarp near, 367 (plate) granitic rock of, 208–209, 208 (plate) jointing in, 197 (plate) alkali flies, 100–101, 330, 331, 332 Alpine County jointing in, 196 snowfall in, 82 altithermal, 314 American River, 80 amphibole, 17, 74, 184 (plate) Ancestral Sierra Nevada, formation of, 157 andesite, 27 andesitic volcanoes, landscapes produced by, 263, 269 Antler Orogeny, 155 Anza, Juan Bautista, 102 aplite, 193 aragonite, 159 arêtes, 36, 296 (plate) Argonaut mine, 223–224, 224 (figure), 226, 227 Arnold, Philip, 126 Artemia monica, 331–332 asbestos, in serpentine, 173, 231

ash, 264, 313 examples of, 31–32 from Long Valley Caldera, 271–274, 273 (figure) magnified view of, 274 (figure) See also tuff Ashburner, William, 115, 118–119, 346 Asiatic clam, 91 asthenosphere, 137 Austin, Mary, 235 avalanche chutes, 36–37, 359 (figure) Bacon, Sir Francis, 144 Baldwin, Mount, 382 (plate) Banner Peak, 148–150 (photo) Bartleson, John, 105 Bartleson-Bidwell party, 105–106 basalt Devils Postpile columns of, 278–282, 279 (plates), 280 (plate), figure, 281 (plates) identifying, 27–28 magnetic stripes of, 139–141, 140 (figure), 144 pillow, 171 basaltic volcanoes, 262, 264 Basin-Ranges province, 138 Bateman, Paul C., 181 (figure), 207 batholiths, 179, 186 See also Sierra Nevada Batholith Bear River, 80 Beatty, M. E., 297 (plate) bedrock, 151 Begole, Charles D., 98 belemnites, 120

437

bench gravels, 253 bergschrunds, 32, 299–300, 299 (plate) Bidwell, John, 105, 377 Big Arroyo, sheeting of granitic rock of, 202 biotite, 18, 183, 184 (plate) Bishop earthquake, 381 Bishop Tuff, 266 (plate), 272 Black Chasm Cavern, 158 Black Divide, 165 Black Giant Peak, 165 Black Kaweah Peak, 165 Black Mountain glacier, 301 Black Point volcano, 327, 328 black smoke, 217 Blake, William P., 114, 115, 250, 342 blue gravels, 253 bombs, volcanic, 29, 264 boulders erratic, 33, 294 (plate), 308 perched, 35 Bourne, W. B. Jr., 229 Bower Cave, 158 Boyden Cavern, 158, 163 (plate), 165 brachiopods, 153 (figure), 154 breccia, 25, 175 andesitic, 269 Brewer, Mount, 120 Brewer, William H. on brine flies at Mono Lake, 331 as staff member of California Geological Survey, 115, 116, 116 (figure), 117, 118, 118 (figure), 120, 121, 123, 124 Bridalveil Fall, 303, 358 (figure) Bridalveil Granodiorite, 189 brine flies, 100–101, 330, 331, 332 brine shrimp, 331–332 bristlecone pine, counting rings of, 64 Broderick, Mount, 306 Brown, Edmund G. “Pat”, Sr., 173, 214 bryozoans, 152, 153, 153 (figure) Buena Vista, coal near, 244 Buena Vista Crest, Intrusive Suite of, 189 buildings destroyed by Owens Valley earthquake, 372

438

INDEX

granite, 202–203 stone, examples of, 31 tuff, 266–267 Cabrillo, Juan Rodriguez, 102 Calaveras River, 80 Calaveras skull, 339–344, 340 (figure) calcareous rock, 19–20 calcite cave speleothems composed of, 160–164, 160 (plate), 161 (plate), 162 (plate), 163 (plate) identifying, 17–18 California plate tectonics theory on origin of land forms in, 146, 147 (figure) Sierra Nevada, location, 4 (map) state mineral of, 73, 214–215 state rock of, 10, 73, 172–173 California Caverns (Cave City Cave), 158, 162, 164 California Division of Mines and Geology, 344 California Geological Survey, 115–120, 116 (figure), 118 (figure) Clarence King’s work with, 117, 118–120, 118 (figure), 123, 124–125 Whitney as director of, 115, 116, 117, 120, 338–339, 344 California Gulls, 331, 332 California Mining Bureau, 344 Calkins, Frank C., 354 camels, fossils of, 248, 249 Campbell, Ian, 342, 343, 344 canyons, of Sierra Nevada, 83, 86 carbon-14 dating, 64, 311, 313 Carbondale, coal near, 244 Carcharodon carcharias, 251 megalodon, 251, 251 (plate) Carlsbad Caverns (NM), 165 Carson, Christopher (“Kit”), 108 Carson Hill mine, 214, 216, 222, 226 Carson River, 80 Cartridge Pass pluton, 192 Cathedral Peak

granodiorite of, 190, 190 (plate), 191, 191 (figure), 192 (figure) jointing in, 197, 346 (plate) Cave City Cave (California Caverns), 158, 162, 164 caves (caverns), 157–164 formations in, 160–164, 160 (plate), 161 (plate), 162 (plate), 163 (plate) open to public, 158–159 (table) origin of, 157 (plate), 159–160, 161 (figure) winds in, 165 Cenozoic Era, landscape during, 244–247 cephalopods, 153 (figure), 154 chain lakes. See glacial stairways Chalfant, Pleasant Arthur, 371, 373 Chamberlain, Rollin T., 133 Chase, J. Smeaton, 352 (plate) chatter marks, 37, 306 (plate), 307 chert, 20, 169 chromite, 231 chrysotile, 172, 173 cinder cones, 30 near Lassen, 262 in Long Valley area, 275, 276 (figure) in Mono Lake, 283, 328 cinder, 28 cirque glaciers, 297–300 cirque lakes, 37–38 cirques, 37, 295, 297 clams, 91, 154 Clarence King, Mount, 98, 123 See also Starr King, Mount Clark, Lewis F., 100 Clark, William, 105 clay, 25, 244 Cleveland, Grover, 350 climatic optimum, 314 Clyde, Norman, 99, 100 coal, 244 Colorado River, 80 cols (passes), 38 combs. See arêtes cones, volcanic, 29–30 See also cinder cones conglomerate, 25–26

Conness, John, 123 Conness, Mount, 6 (plate), 299 continental drift, 132–133, 144 convection cells, 144–145, 145 (figure) convergent plate boundaries, 142–143, 142 (figure) Convict Lake, 7 (plate), 175 (plate), 237 (plate), 309 (plate) Copperopolis, 231 corals, 152, 153 (figure) Corbicula fluminea, 91 core, Earth’s, 134 (figure), 135 Cornish pumps, 228–229 correlation with glacial record, 313, 318–319, 326 principle of, 69 Cosumnes River, 80 Cotter, Richard (Dick), 127 peaks climbed by, 99, 119 (figure), 121–122, 122 (plate) as staff member of California Geological Survey, 118 (figure), 120, 125 counting dating methods, 64–65 Crater Lake (OR), 323, 387 cratons, 146 Crespi, Juan, 102 crevasses, 32–33, 310 crinoids, 152, 153–154, 153 (figure) crust, Earth’s, 134–135, 134 (figure), 137 Crystal Basin, 306 (plate) Crystal Cave (Cavern), 157 (plate), 158, 161 (plate), 162 (plate), 165 cyclopean stairs. See glacial stairways Dana, James Dwight, 116 Dana, Mount, 116, 182, 247, 380, 380 (plate) Dana Glacier, 296 (plate), 299 dating methods, 64–65 Davis, Jefferson, 114 Dawson, Glen, 100 Deadman Creek, 293 (plate) Delta, the, 88–89, 89 (figure), 90 Delta-Mendota Canal, 90–91

INDEX

439

Denali, Mount (McKinley) (AK), 85 (plate), 98 Desmostylus, 249 Devils Postpile National Monument, 258–259 (photo), 278–282, 279 (plates), 280 (plate, figure), 281 (plates) John Muir Trail and, 204, 206 diamonds in hydraulic mining pits, 256 swindle related to, 126–127 dikes, 193, 193 (plate), 206 diorite, 23–24 divergent plate boundaries, 141–142, 142 (figure) docking, 146, 154–155 domes examples of, 30 of Yosemite, 109 (figure), 199–202, 201 (plate), 207 (plate), 360–361 See also Half Dome Donner Lake, Moses Schallenberger’s stay at, 111–112 Donner party, 112 Drake, Francis, 102 Dusy basin, 76–78 (photo) DuToit, Alexander, 133 Eagle Lake, 239 Eagle Rock, 373, 375 Eared Grebes, 330 Earth interior of, 134–135, 134 (figure) tectonic plates of, 136 (figure), 137–138 earthquake waves, Earth’s interior as revealed by, 134–135, 134 (figure), 137 earthquakes, 365–391 faults and, 367, 380–385, 384 (figure) largest California, 370–371 seismograph recording of, 378 (figure) series of, in Mammoth Lakes area, 263 (plate), 285–286, 381, 381 (plate), 382 (plates), 383, 383 (figure)

440

INDEX

See also faults; Owens Valley earthquake Ebbett’s Pass, 103 Eel River, rate of erosion by, 93 Egenhoff, Elisabeth L., 229 Eichorn, Jules M., 100 El Capitan, 189, 193, 198, 200 (plate), 358 (figure) elastic rebound, 367 Emerson, Ralph Waldo, 349 Emmons, Samuel F., 126–127 Empire mine, 228, 229–231 Ephydra hians, 100–101, 330, 331, 332 Eric the Red, 314 erosion during Cretaceous and Tertiary periods, 243, 244 as force in mountain building, 5, 92–93, 365, 385, 386–387 by glaciers, 304–309 erratics, 33–34, 294 (plate), 307 Everest, Mount, 298 exfoliation, 199–202, 201 (plate) explosion pits, 30 Fages, Pedro, 102 Fairview Dome, 199, 306 Farallon plate, Sierra Nevada Batholith formation and, 179–181 Farquhar, Francis P., 99, 100 faults active in Sierras, 367, 370 (figure) defined, 366 earthquakes and, 367, 380–385 gold deposits and, 219–221 Kern River Canyon and, 368–369, 369 (plate) movement of, types, 384 (figure) as origin of Lake Tahoe, 387–388, 390 (plate) as origin of Yosemite Valley, 351–352 Feather River, 80, 92 feldspar crystallization of, from magma, 183, 185 (plate) identifying, 18 importance of recognizing, 74

felsite, 27 Ferguson, Henry, 220 firn, 292 firn line, 291 Fisherman’s Peak, 98, 124 See also Whitney, Mount Font, Pedro, 102, 103 Foote, Arthur de W., 229–230 foraminifers, 146, 153 Ford, Gerald, 222 foreshocks, of Owens Valley earthquake, 377 Forest Reserve Act (1891), 350 The Forms of Water in Cloud and Rivers, Ice and Glaciers (Tyndall), 122 (plate) fossils correlating rock layers with, 69, 146 continental drift and, 132 of Cretaceous plants and animals, 243 geologic time scale and, 65, 69 oldest, 7 (plate), 237 (plate) at Sharktooth Hill, 249–252, 251 (plate) of Tertiary land animals, 247–248, 249, 252 of Tertiary plants, 245–247 uplifting of mountains and, 120, 152 Frémont, John Charles, 107–110, 108 (figure), 112, 119, 228, 368 Fresno River, 80 Fryxell, Fritiof, 356–357 Gabb, William, 115, 116, 120 gabbro, 24 Gaines, David, 325, 330 Garcés, Francisco, 102–103 Gardiner, James T., 117, 118 (figure), 120, 121, 127 Gardiner, Mount, 123 Garlock fault, 83 garnet, 235 Garnet Hill, 235 geologic history, of Sierra Nevada, 66–67 (figure) The Geologic Story of Yosemite National Park (Huber), 198

geologic time scale, 65, 68–69, 68 (figure) geology, as scientific field, 63 giant’s kettles. See glacial moulin (mill) giant’s staircases. See glacial stairways Gibbs Canyon, glacier in, 314, 316 glacial advances, 310, 311, 311 (table) glacial features, 32–42 (table) See also specific features glacial flour, 295 glacial moulin (mill), 38–39, 301, 305 glacial polish, 39, 295, 306, 308, 308 (plate) glacial retreats (recessions), 310–311 glacial stairways, 39–40, 316, 317 (figure), 326 glacial step lakes. See glacial stairways glacial tarns, 37–38, 316 glaciations in Lake Tahoe area, 389 as mountain building process, 5–6, 291, 366 in Sierras, 311, 311 (table), 313 Glacier Point, 305, 358 (figure) glacierets, 299, 314–315, 315 (table) glaciers, 288–290 (photo), 291–319 advances and retreats of, 310–316, 311 (table) cirque, 297–300 crevasses in, 310 currently existing, 315 (table) features of, 32–42 (table) formation of, 291–294 ice streams of, 300, 302–303, 359 landscape formation by, 291, 304–309, 307 (figure) movement of, 293, 293 (plate), 294–295, 348–349 Muir’s focus on, 291, 301, 339, 346–348, 349, 353–354 number of, in Sierras, 298–299 rock, 33, 316 Whitney on, 339, 347, 352–353 See also specific features; specific glaciers Glaciers of California (Guyton), 299, 318–319

INDEX

441

Glass Creek, 267 (plate) obsidian flow, 5 (plate) global tectonics. See plate tectonics gneiss, 20–21, 182 Goddard Terrane, 146 gold, 213–231 as California state mineral, 73, 214–225 modern price of, 215, 221–222 nuggets, largest, 215, 216 origin of California deposits of, 216–221, 234 in quartz veins, 92 (plate), 216 (plate), 220–221, 226 Tertiary river deposits of, 253, 254–255 (figure) gold mining along Kern River, 368 Cornish pumps for, 228–229 exhibits of mines and equipment from, 232–233 (table) in Grass Valley mines, 227–231 hard rock, 226–227 heap leaching process for, 221, 222 (figure) hydraulic, 235–236, 236 (figure), 253, 256, 256 (figure) in Kennedy mine, 223–226, 225 (plate, figure) modern resurgence of, 213, 215, 221–223 open-pit, 222–223 stream habits and, 79–80, 86, 88, 91–92 tuff and, 266–267 grabens, 351, 380–381 granite, 179–209 age of, in Sierra, 194, 195 (figure) appearance of mountains composed of, 165, 209 formation of, 182–187, 184–185 (plate), 187 (plate), 188 (plate), 219–221 identifying, 12, 24, 181, 182 (plate) jointing in, 196–198, 197 (plate), 198 (figure), 199 (plate)

442

INDEX

sheeting of, 196, 199–202, 201 (plate) terminology for, 181–182 where to see, 23–24, 202–203, 208–209 granitic rock, 179, 182 See also granite granitization, 182 granodiorite, 182, 182 (plate), 186, 388 graptolites, 237 (plate) Grass Valley mines, 227–231 grats. See arêtes gravel, Tertiary river gold deposits and, 253, 254–255 gravestone schist, 170 (figure) gravestone slate, 170 (figure) Gray, Asa, 348 gray pine, 269 Great Ice Age animal extinctions and, 248, 251 dating, 64 glaciers of, 291, 297, 302, 303, 311–314, 311 (table) Mono Lake in, 323, 324, 326, 327, 328 theories about causes of, 317–319 See also Little Ice Age Great Lakes, 323 Great Salt Lake, 323, 332 Great Slave Lake (Canada), 387 Greenland, Norse colony in, 314 greenstone, 21, 267 grinding rocks, 97, 100, 101 (plate) grooves (scratches), 42 Gunn, Eva Lee Shepherd, 371–372 Guyton, Bill, 299, 318–319, 353 Hague, James D., 229 Half Dome, 176–179 (photo), 358 (figure) formation of granodiorite of, 189–190, 191, 191 (figure) glacial erosion of, 305, 352 (plate) jointing and sheeting of granitic rock of, 197–198, 199, 199 (plate)

Matthes on origin of, 355 Whitney on inaccessibility of, 339 Hall, A. F., 99 Hamilton Lake avalanche chute near, 359 (figure) jointing near, 196, 198 (figure) hanging valleys, 40, 359, 360 (figure) hanging waterfalls. See hanging valleys hard rock mining, 226–227 Harrison, Benjamin, 350 Harte, Brett, 158 Harvard mine, 222, 226 heap leaching process, 221, 222 (figure) helictites, 164 Herculaneum, 268–269 Hetch Hetchy Valley dam in, 236–238, 350–351, 350 (plate) glacial origin of, 304, 353 Tueeulala Falls in, 303 High Sierra Terrane, 146 High Sierra Trail, 196, 198 (figure), 316 (figure), 393 Hipparion, 248 Hittell, John S., 236 Hoffmann, Charles F., 115, 116, 117, 120 Hoffmann, Mount, 116 Hoover, Herbert, 218, 228 Hoover, Lou Henry, 228 hornfels, 21, 166, 193 (plate) horns (matterhorns), 41, 296 (plate) horses, fossils of, 248, 249 Huber, King, 196, 198 Hunter, W. L., 98 Hurricane Crawl Cave, 159 Hutchings, J. M., 106 (plate) Hutchinson, James S., 98, 99 Huxley, Mount, 307 hydraulic mining, 235–236, 236 (figure), 253, 256, 256 (figure)

categories of, 72 common, 72 (figure) defined, 70 gold in, 213 plutonic, 23–25 (table) volcanic, 27–29 The Incomparable Valley (Matthes), 356–357 Indian Grinding Rock State Historic Park, 100, 101 (plate) intrusive suites, 189 See also Tuolumne Intrusive Suite; Whitney Intrusive Suite Inyo Crater Lakes, 283, 285 (plate) Inyo Craters, 283 Inyo Domes, 5 (plate) Ione, coal near, 244 iron deposits, 231, 234 Isabella, Lake, 368–369 isinglass. See muscovite isoseismal maps, 377–378, 379 (figure) Izaak Walton, Mount, 296 (plate)

Ice Age. See Great Ice Age; Little Ice Age igneous rocks

kame terraces, 34 Kaweah Peaks, 156 (plate) Kaweah River, 80

jade, nephrite, 231 Janin, Henry, 126, 127 Jenkins, Olaf P., 344 Jewel Cave (SD), 165 John Muir Trail, 204–206, 205 (figure) John Muir Wilderness, 84, 204 Johnson, Albert H., 98 Johnson, Willard D., 150, 299–300 Johnson Granite Porphyry, 190, 191, 191 (figure), 192 (figure) Johnston, Verna, 239 jointing of granitic rock, 196–198, 197 (plate), 198 (figure), 199 (plate) sheeting as form of, 196, 199–202, 201 (plate) Jones, William, 340, 341 Jurassic Period, 120, 156–157

INDEX

443

Kearny, Stephen Watts, 109 Keith, William, 348 Kelsey, Ann, 105, 106 Kelsey, Benjamin, 105 Kelsey, Nancy, 105, 106 Kennedy mine, 223–226, 225 (plate, figure), 227 Kent, William, 349 Kern Lake, 393 Kern River Canyon, 368–369, 369 (plate) King, Clarence Rivers, 125 (figure) biography of, 124–127 California Geological Survey work by, 117, 118–120, 118 (figure), 123, 124–125 glaciers and, 339, 347–348 Mount Whitney ascent attempted by, 84, 122–123, 122 (plate), 124, 206 peaks climbed by, 84, 97, 98, 99, 119 (figure), 120–123, 122 (plate), 125 King, Mount. See Clarence King, Mount King, Thomas Starr, 179 Kings Canyon National Park, 146, 159, 204, 393 Kings River, 80, 86, 103, 109, 123 Kings Terrane, 146 Kings-Kaweah Terrane, 146, 155 knife-edged ridges. See arêtes Knight, Goodwin, 173 Knight, Virginia, 173 Knights Ferry, fossils found near, 248 Krakatau volcanic eruption, 261, 318 Kuna Crest, 189, 190, 191 (figure) lahars, 30, 262 (plate), 267–269, 270 (figure), 287 lakes chain of, from glaciers, 39–40, 316, 317 (figure), 326 cirque (tarns), 37–38, 316 moraine-dammed, 34–35, 316 varves at bottom of, 64–65 See also specific lakes Langley, Mount, 99, 123

444

INDEX

Langley, Samuel Pierpont, 99 Larus californicus, 331, 332 Lassen, Mount, 118, 143, 262 Last Chance, 253 laterite, 26 Laurel Canyon, 312 (plate) lava, pillow, 168–169, 170 (plate), 171 lava flows, examples of, 31 Le Conte, Joseph N., 98, 99, 182, 348, 353 Le Conte, Mrs. Joseph N., 99 Lembert Dome, 190, 199, 305 (plates), 306 Leonard, Zenas, 104 Lewis, Meriwether, 105 Liberty Cap, 199, 306 lignite, 26 Lilburn Cave, 159 limestone, 75, 234 (plate) See also caves (caverns) Lincoln, Abraham, 345 Lindley, C., 99 Line of Demarcation, 102 lithosphere, 137 Little Ice Age Mono Lake in, 323 overview of, 314–316 present-day glaciers formed in, 301, 311, 314–316, 356 See also Great Ice Age “Living Glaciers of California” (Muir), 348 lizardite, 172 load, carried by streams, 88 lode mining, 226–227 Loma Prieta earthquake, 370–371 Lone Pine earthquake. See Owens Valley earthquake Long Valley Caldera, 5 (plate) eruption history of, 263 (plate), 270–276, 273 (figure) eruption potential in, 283, 285–287, 286 (plate), 287 (plate), 383 See also Mammoth Lakes area Long’s Peak (Colorado), 298–299 Los Angeles, water diverted to, 80, 238–239, 323, 326, 332–333

Lucas, John, 98 Lundy Canyon, 210–212 (photo) Lyell, Mount, 94–96 (photo), 117, 117 (plate), 339, 358 (figure), 380 (plate) Lyell glacier, 297 (plate), 299–300, 299 (plate), 339, 380 (plate) Maclure glacier, 347 magma crystallization order from, 183, 184–185 (plate), 186 formation of, 141 granite formed from, 180–181 (figure), 182–183, 186–187, 187 (plate) magmatic differentiation, 186 magnesite, 231 magnetic field, Earth’s, 135 magnetic poles, 139–141, 140 (figure), 144 magnetite, 139, 234 Mammoth Lakes area earthquake series in, 263 (plate), 285–286, 381, 381 (plate), 382 (plates), 383, 383 (figure) See also Long Valley Caldera Mammoth Mountain, 276–278, 277 (plate), 286, 287 (plate) mantle, Earth’s, 134 (figure), 135 convection of, 144–145, 145 (figure) layers of, and tectonic plates, 137 maps, 43–59 marble, 7 (plate), 166 Marianas Trench, 143 Mariposa Estate, 110, 118–119 mariposite, 18 Marsh, John, 106 Marshall, James, 235 mastodons, fossil evidence of, 248 matterhorns (horns), 40–41, 296 (plate) Matthes, François E., 314, 355 (figure) biography of, 354 on origin of Yosemite, 337, 355–357, 356 (figure), 357 (figure), 358 (figure), 360–361, 385–386

Matthes Crest, 201 (plate) Matthews, Robert A., 127 Mattison, William, 340, 341, 342–343 Mauna Kea (HI), 98 Mauna Loa (HI), 85 (plate) McKinley, William, 350 McKnight, George, 226 meanders, 86–87, 87 (plate) Merced Peak, 301 Merced River, 80, 358 (figure) Mercer Caverns, 159 Merriam, J. C., 342 Mesozoic Era, 156 Mesozoic rocks, 151 metamorphosed, 165–166, 169–171 where to see, 173–175 See also metamorphic rocks metamorphic rocks, 164–170, 167 (plate) categories of, 72 color of, 165, 166 (plate), 171 danger of climbing in, 156 (plate) defined, 70 formation of, 155, 166–169 identifying, 19–23 (table), 166 minerals produced by contact with, 235 remnants of (roof pendants), 164–165, 171 (figure) where to see, 19–23 (table), 171–175 metamorphism, 166–167 of ice, 291–292 mica crystallization of, from magma, 183 identifying, 18, 168 importance of recognizing, 74 Mid-Atlantic Ridge, 138, 141–142, 217 Middle Palisade, 99 mid-ocean ridge, 138–141, 139 (figure), 140 (figure) Miller, John, 150 Minarets, 150, 234 minerals California state, 73, 214–225 crystallization of, from magma, 183–186, 184–185 (figure)

INDEX

445

minerals (cont.) defined, 72–73 identifying, 17–19 (table) important to recognize, 73–74 valuable for mining, 231, 234–235 See also gold; water mining of minerals other than gold, 231, 234–235, 234 (plate) See also gold mining Miocene age, sea animals of, 248–252, 251 (plate) Moaning Cave (Cavern), 159, 162 (plate) Moffet, James K., 98, 99 Mokelumne Hill, 215, 253 Mokelumne River, 80 molybdenum, 235 Mono Basin, 323–324 Mono Craters, 282–283, 282 (plate) in Mono Lake, 326–328, 328 (plate), 329 (plate) Mono Lake, 320–333, 327 (plate) alkaline waters of, 324, 327, 332 animal life of, 328 (plate), 330–332 “bathtub rings” of, 326, 327, 327 (plate) Black Point volcano in, 327, 328 geothermal potential of, 328, 330 glacial rubble near, 303 Negit Island, 283, 326–327, 327 (plate), 328 (plate) obsidian from near, 100 Paoha Island, 283, 326, 327–328, 329 (plate), 330 tufa towers of, 320–322 (photo), 325–326, 325 (plate) water level history of, 323–324, 326 water withdrawal from, 238, 239, 323, 326, 332–333 Mono Lake Guidebook (Gaines), 325 Moore, James G., 169, 186 moraine-dammed lakes, 34–35, 316 moraines, 34, 309, 312 (plate) determining age of, 311–314 under snow, 82 (plate) where to see, 313–314 Morrice, Charles, 250

446

INDEX

Morrison, Mount, 237 (plate) Morrison, Robert, 237 (plate) Mother Lode faults in, 219, 366 hydraulic mining in, 253 meaning of term, 226, 227 mining resurgence in, 222 origin of, 219 streams in area of, 86 tuff buildings in, 266 Mother Lode route (State Hwy. 49), 86, 172 mountain building by orogenies, 155, 157 erosion as force in, 5, 92–93, 365, 385, 386–387 from fault movements, 366, 380–385, 384 (figure) glaciation as force in, 5–6, 291, 366 overview of processes of, 5–6, 365–366 staircase effect in, 386–387 volcanism as process in, 5, 365–366 mountain glaciers, 293 mountain ranges in oceans, 138–141, 139 (figure), 140 (figure) structure of, 134–135 Mountaineering in the Sierra Nevada (King), 125, 348 mountains color of, 165, 166 (plate) Sierra Nevada’s highest, 98–100 (table) The Mountains of California (Muir), 150, 162 mudflows, volcanic, 31, 262 (plate), 267–269, 270 (figure), 287 Muir, John, 345 (figure) biography of, 344–347 caves visited by, 158, 162, 164 on Donner party, 112 on effect of earthquake on Yosemite Valley, 373, 374–376 glaciers as focus of, 291, 301, 339, 346–348, 349, 353–354 Hetch Hetchy dam opposed by, 236–237, 350–351

legacy of, 125, 349–351 on origin of Yosemite, 337, 352–354 peaks climbed by, 124, 150, 206 (plate), 348 Muir, Mount, 84, 100, 206, 347 (plate) Muir Woods National Monument, 349 Mulholland, C., 98, 373 Murphy, Elizabeth Yuba, 111 muscovite, 18, 183, 185 (plate) Nannipus, 248 National Geodetic Survey, 84 Native Americans brine flies at Mono Lake gathered by, 100–101, 330, 331 grinding rocks of, 97, 100, 101 (plate) obsidian as resource for, 100, 274, 275 (plate) Negit Island, 283, 326–327, 327 (plate), 328 (plate) Neohipparion, 248 Nevadan Orogeny, 157 Newmont Mines, 231 Nixon, Richard, 221–222 North American plate, Sierra Nevada Batholith formation and, 179–181 North Deadman Creek Dome, 283 North Dome, 358 (figure) North Palisade, 98, 301 North Palisade glacier. See Palisade glacier North Star mine, 228, 229, 230–231 nuée ardente, 31, 287, 312 Oakdale, fossils found near, 248 Oakley, Kenneth, 343 obsidian dome formation, 284 (figure) Glass Creek flow of, 5 (plate) identifying, 28 as resource for Native Americans, 100, 274, 275 (plate) Olmsted, Frederick Law, 119 open pit mines, 222–223 ophiolites, 168–169

orbicular granite, 188 (plate) Oroville Table Mountain, 253, 264 Ortelius, Abraham, 132 outwash plains, 35 Owens, Richard, 108 Owens Lake, 326, 333, 373 Owens River, 80, 87 (plate), 374 (plate) Owens River Gorge, 274, 275 Owens Valley, 380–381 Owens Valley earthquake, 367, 370–379 changes in natural features due to, 373–376, 374 (plate), 377, 378 damage to Lone Pine by, 367, 371–373, 371 (plate), 372 (figure) intensity and magnitude of, 376–379, 379 (figure) origin of, 381 Pacific Crest National Scenic Trail, 204, 205 (figure) Paleozoic rocks formation of, 151–156, 153 (figure) metamorphosed, 165–166, 169–171 where to see, 172–173 See also metamorphic rocks Palisade glacier, 206, 295, 297, 298, 301, 301 (plate) Palisade peaks, 76–78 (photo), 98, 99 Pangea, 132–133 Panum Crater, 271 (plate), 275 (plate), 282–283 Paoha Island, 283, 326, 327–328, 329 (plate), 330 Paricutín volcano (Mexico), 261, 366 passes (cols), 38 paternoster lakes. See glacial stairways pay streaks, 91 pegmatite, 24, 193 Pelé, Mount (Martinique), 261, 272 Pelton wheel, 230 peneplains, 385, 386 perched boulders, 35 peridotite, 25, 168, 231 permafrost, 314

INDEX

447

petroglyphs, 101 (plate) Phalaropus lobatus, 331 tricolor, 331 phenocrysts, 122 (plate), 193 phyllite, 21–22 Pike, Robert D., 99 pillow basalt, 171 pillow lava, 168–169, 170 (plate), 171 Pinson, Paul, 99, 123 Pinus sabiniana, 269 plate tectonics theory, 131–147 basic principles of, 135, 136 continental drift and, 132–133, 144 on Earth’s plates, 136 (figure), 137–138 on forces moving plates, 144–146, 145 (figure) on formation of Sierra Nevada Batholith, 179–181, 180 (figure) gold deposition and, 218–221 importance of, 3, 131, 133 on midoceanic ridge, 138–141, 139 (figure), 140 (figure) on movement of plates, 141–144, 142 (figure), 144 (figure) on origin of land forms, 146–147, 147 (figure), 154–157 Pliohippus, 248 plutonic igneous rocks, 23–25 (table), 181 plutons, 187–194 of Sierra Nevada Batholith, 181, 188, 192–194 size of, 187–188 of Tuolumne Intrusive Suite, 189–191, 191 (figure), 192 (figure), 193 of Whitney Intrusive Suite, 122 (plate), 193 Podiceps nigricollis, 330 Polemonium Peak, 99 polish. See glacial polish Polk, James K., 109 Polk, Willis, 229 Polly Dome, 199 Pompeii, 268–269

448

INDEX

porphyry, 25 Portolá, Gaspar de, 102 potassium-argon dating, 64 Pothole Dome, 190, 306 potholes. See glacial moulin (mill) precipitation, 81–82 Preuss, Charles, 110 pronghorn antelope, fossils of, 248 pumice, 28–29 Putnam, William C., 323–24 Pyramid Hill, 249, 252 Pyramid Lake, 107, 238, 326 Pyramid Peak, 247 pyroxene, 18–19, 74 Pywiack Dome, 199 quartz crystallization of, from magma, 185 (plate), 186 gold in veins of, 92 (plate), 216 (plate), 220–221, 226 identifying, 19 importance of recognizing, 73, 74 quartz diorite. See tonalite quartz mining, 226–227 quartz monzonite, 182 quartzite, 22, 166 Quaternary Period, 377 radioactive dating, 64 radiolaria, 153, 168, 171 Rainbow Falls, 268 (plate) Rainbow Mountain, 165 rainfall, 81–82 Rainier, Mount (WA), 98, 349 Raub, Bill, 298–299 Red-necked Phalaropes, 331 Red Spur, 156 (plate) Reid, Henry Fielding, 367 rhyolite, 29, 73 (plate), 382 (plate) rhyolitic volcanoes, 262–263, 265 (plate) Ribbon Falls, 303 Richter scale, 378 (figure) rift valleys, 138 Ring of Fire, 143, 144 (figure)

Ritter, Mount, 123, 148–150 (photo), 348 rivers draining Sierra Nevada, 80, 81 (figure) of Tertiary Period, 246 (figure), 247, 252–253, 254–255 (figure), 256–257 See also streams; specific rivers Robinson, Bestor, 100 roche moutonnée, 41, 305 (plates), 306 rock cycle, 71 (figure) rock glaciers, 33, 316 rock identification key, 7, 11–16 how to use, 9–10 rocks classes of, 69–72 dating, 64–65 naming, 7, 74–75 state, 73, 172–173 Rogers, Lovely, 368 roof pendants, 164–165, 171 (figure) Roosevelt, Franklin, 230 Roosevelt, Theodore, 346–347, 350 Royal Arches, 201 (plate), 358 (figure) rubidium-strontium dating, 64 Russell, Israel C., 99, 325, 326 Russell, Mount, 1–2 (photo), 99 Sacramento River, 80, 88–89, 89 (figure), 256 San Andreas fault, 83 plate movement along, 137, 142 (figure), 143–144, 179 San Francisco, Hetch Hetchy water for, 236–238, 350–351, 350 (plate) San Francisco earthquake, 367, 370 San Joaquin River, 80, 93, 256 delta formed by, 88–89, 89 (figure) in Devils Postpile area, 268 (plate), 278 Sánchez, José Bernardo, 103 sandstone, 12, 26 Saussure, Horace Benedict de, 348 Schallenberger, Moses, 111–112

schist, 22, 166, 168 gravestone, 170 (figure) scratches (grooves), 41–42 Scribner, John C., 340 sea lilies, 152, 153–154, 153 (figure) sea lions, fossils of, 250, 252 Searles Lake, 326 seas hydrothermal deposition of gold in, 216–217 of Paleozoic and Mesozoic eras, 151–157 shallow, of Cenozoic time, 244 Smartville block as originating in, 218–219 seaslides, 154 sedimentary rocks categories of, 70 defined, 69–70 formation of, 155–156 identifying, 25–29 (table) sedimentation, 90–91 seiches, 373 seismographs, 377, 378 (figure) Sentinel Dome, 358 (figure) Sequoia gigantea, 104 (figure), 105–106 Sequoia National Park, 349 Crystal Cave (Cavern) in, 157 (plate), 158, 161 (plate), 162 (plate), 165 Hurricane Crawl Cave in, 159 John Muir trail in, 204 Kern River Canyon in, 368–369, 369 (plate) terranes of, 146 serpentine, 172 (plate), 174 (plate) as altered peridotite, 168 asbestos in, 173, 231 as California state rock, 73, 172–173 identifying, 22–23 shale, 26, 91 sharks, fossil teeth of, 248, 250–251, 251 (plate) Sharktooth Hill, 248 –252, 251 (plate)

INDEX

449

Shasta, Mount, 98, 118, 143, 339 Sheep Rock, 123, 124 sheeting, of granitic rock, 196, 199–202, 201 (plate) Sherwin Canyon, 312 (plate) shields, 157 (plate) Sierra Club, 237, 350 Sierra East (Smith), 238–239, 332–333 Sierra Nevada: The Naturalist’s Companion (Johnston), 239 Sierra Nevada canyons of, 83, 86 general topography of, 79, 79 (figure), 83 geologic history of, 66–67 (figure) location of, 4 (figure) rivers draining, 80, 81 (figure) Sierra Nevada Batholith dominant rock types in, 186 formation of, 179–181, 180 (figure) history of, 194–196, 195 (figure) plutons of, 181, 188, 192–194 Sill, Mount, 99 Sixteen-to-One mine, 222 Slack, John, 126 slate, 23, 166 gravestone, 170 (figure) Slide Mountain (NV), 393 slides, 393 Smartville block, 169, 218–219 Smartville Terrane, 156 Smith, Genny, 238–239, 332–333 Smith, Jedediah Strong, 103, 105 Smith, Mrs. Vernon, 374 snails, 153 (figure), 154 snowfall, 81–82, 82 (plate) Sonoma Orogeny, 155 Sonomia Terrane, 155 South Palisade, 99 Spanish, sighting of Sierra Nevada by, 102–103 speleothems, 160–164, 160 (plate), 161 (figure, plate), 162 (plate), 163 (plate) Spring Valley mine, 235 St. Helens, Mount (WA), 143, 262 Staircase Falls, 197

450

INDEX

stalactites, 160–162, 161 (plate), 162 (plate), 163 (plate), 164 stalagmites, 162, 162 (plate) Stanislaus River, 80, 270 (figure), 341 Stanislaus Table Mountain. See Tuolumne Table Mountain Starlight Peak, 99 Starr King, Mount, 338 Steinmann, Gustav, 168 Steller, Georg, 261 Stephens party, 110–111 Stockton, Robert Field, 109 streams glacial, 310 habits of, and gold mining, 80, 86, 88, 91–92 of ice, 300, 303 load carried by, 88 meandering by, 86–87, 87 (plate) See also rivers subduction of Farallon plate, 179–181, 180 (figure) results of, 143 subduction zones deep-sea trenches as, 141, 143, 144 (figure) plate movement and, 145–146 subjacent series, 152 Sugar Pine Point State Park, 100 Sugarloaf, 199 Surtsey volcano (Iceland), 261, 366 Sutter, Johann Augustus, 107–108 Sutter’s Fort, 107, 111 Tahoe, Lake, 323, 387–391 Emerald Bay, 362–364 (photo), 388 (plate), 389 moraines in area of, 313 origin of basin occupied by, 351, 387–389, 390 (figure) waters of, 389, 390 (figure), 391 tailing, 224, 225, 226 Talbot, Theodore, 108–109 Tamarack, snowfall at, 82 tapirs, fossils of, 249 tarns, 37–38, 316

tectonic plates. See plate tectonics theory Tejon Pass earthquake, 370 Tenaya Lake, 6 (plate), 294 (plate) tephra, 264 terranes, 146, 147 (figure), 154–155 Tertiary Period land animals of, 247–248, 249, 252 landscape during, 247 rivers of, 246 (figure), 247, 252–253, 254–255 (figure), 256–257 sea animals of, 248–252, 251 (plate) volcanic eruptions during, 264, 266–269, 270 (figure) theodolite, 120 thinolite, 322, 325 Thompson, John A. “Showshoe,” 113–114, 113 (figure) Thousand Island Lake, 148–150 (photo) Three Brothers, 197, 358 (figure), 386 (figure) Thunderbolt Peak, 100 till, 27, 35–36, 309, 309 (plate), 312 tombstone rocks, 170 (figure) tonalite, 182, 186 Tragedy Springs, 202 transform plate boundaries, 142 (figure), 143–144 Tregallas, Henry, 373 trenches, 141, 143, 144 (figure) trondhjemite, 182 Truckee River, 80, 110 Tueeulala Falls, 303 tufa, 322, 326, 331 tufa towers, 320–322 (photo), 325–326, 325 (plate), 332 tuff, 264, 266–267, 266 (plate) examples of, 31–32 identifying, 27, 29 within Long Valley Caldera, 266 (plate), 272, 274 (figure) tungsten, 230, 230 (plate), 235 Tuolumne glacier, 300, 306 Tuolumne Intrusive Suite, 189–191, 191 (figure), 192 (figure), 193

Tuolumne Meadows, 206, 305–306, 313, 346 Tuolumne River, 80 Tuolumne Table Mountain, 248, 253, 270 (figure) turbidity currents, 154 Twain, Mark at California Caverns, 158 on Lake Tahoe, 391 on Mono Lake, 324, 330, 331 Two Teats, 240–242 (photo), 245 (plate) Tyndall, John, 99, 120, 122 (plate), 125, 348–349 Tyndall, Mount, 84, 99, 119 (figure), 121, 122 (plate) U-shaped valleys, 42, 304, 304 (plate) unconformities, 169 Underhill, Robert M. L., 100 Up and Down California in 1860–64 (Brewer), 116 (figure) uranium-lead dating, 64 U.S. Geological Survey first director of, 127 on height of Mount Whitney, 84 on Mammoth Mountain area volcanic hazard, 286, 287 (plate) rock names in reports of, 166 Yosemite Problem and, 354 Valley of 10,000 Smokes (AK), 272 valley glaciers, 293 varves, 64–65 Vesuvius, 261, 268–269 volcanic ash. See ash; tuff volcanic bombs, 29, 264 volcanic cones, 29–30 See also cinder cones volcanic features, 29–32 (table) volcanic igneous rocks identifying, 27–29 (table) in Lake Tahoe area, 388–389 metamorphosed, 170–171, 170 (figures) volcanic mudflows, 30, 262 (plate), 267–269, 270 (figure), 287 Volcanic Tableland, 274, 275

INDEX

451

volcanism, as mountain building process, 5, 365–366 volcanoes, 261–287 age of glaciers and, 312–313 eruption records of, 261–262 examples of, 32 landscapes produced by, 262–264, 276 (figure) lava types produced by, 262, 264, 265 (plate) Tertiary eruptions of, 264, 266–269, 270 (figure) Tertiary rivers and, 252–253, 254–255 (figure) See also specific volcanoes Walcott cirque (Antarctica), 298 Walker, Joseph Reddeford, 104–105, 108 Walker River, 80 water, 235–239 diverted to Los Angeles, 80, 238–239, 323, 326, 332–333 Hetch Hetchy as source of, for San Francisco, 236–238, 350–351, 350 (plate) mining’s dependence on, 235–236, 236 (figure) See also rivers; streams weathering, 167 Wegener, Alfred, 132–133, 132 (figure), 144 White Mountain Peak, 98 Whitney, Josiah Dwight, 337–344, 338 (figure) biography of, 337, 344, 346 Calaveras skull and, 339–344, 340 (figure) as first director of California Geological Survey, 115, 116, 117, 120, 338–339, 344 on glaciers, 339, 347, 352–353 Mount Whitney named for, 84, 98, 121 on origin of Yosemite, 337, 339, 351–353 on Owens Valley earthquake, 376–377

452

INDEX

Whitney, Mount, 60–62 (photo), 123 (plate), 128–130 (photo), 347 (plate) climbing, 84–85 elevation of, 83, 84, 85 (plate), 98 first climbed by, 98, 124 King’s attempts to climb, 84, 122–123, 122 (plate), 124, 206 Muir’s ascent of, 124, 206 (plate) view from, 1–2 (photo), 84 Whitney Glacier, 339 Whitney Group. See Whitney, Mount Whitney Intrusive Suite, 84, 122 (plate), 193 John Muir Trail through, 204–206, 206 (plate) Williamson, Mount, 98, 119 (figure), 122 Williamson, Robert S., 98, 114, 122 Wilson Butte, 265 (plate), 283 Wilson’s Phalaropes, 330–331 Wind Cave (SD), 165 The Yosemite (Muir), 353–354 The Yosemite Book (Whitney), 351, 353 Yosemite Falls, 302 (plate), 303 “Yosemite Glaciers” (Muir), 348 Yosemite National Park, 6 (plate), 334–336 (photo), 353 (plate), 386 (figure) domes of, 109 (figure), 199–202, 201 (plate), 207 (plate), 360–361 glacier evidence in, 294 (plate), 296 (plate), 352–353 jointing in, 197–198, 199 (plate) Native American grinding rocks in, 100 Tuolumne Intrusive Suite in, 189–191, 191 (figure), 192 (figure), 193 See also Half Dome; Yosemite Valley Yosemite Problem. See Yosemite Valley, origin of Yosemite Valley, 189 (figure), 339 (figure), 349 (figure)

Calkins’s map of, 354–355 effect of Owens Valley earthquake on, 373, 374–376 first non-Indian sighting of, 104–105, 104 (figure) glacial erosion in, 304–306, 304 (plate), 305 (plates), 359 Intrusive Suite of, 189 as state park, 345–346 See also Yosemite National Park; Yosemite Valley, origin of

Yosemite Valley, origin of current view of, 357–359 Matthes on, 37, 355–357, 356 (figure), 357 (figure), 358 (figure), 360–361, 385–386 Muir on, 337, 353–354 Whitney on, 337, 339, 351–353 Yuba River, 80, 243 (figure)

INDEX

453

ABOUT THE AUTHOR

Geologist Mary Hill has written many books and articles explaining geology to nongeologists, including popular volumes such as California Landscape: Origin and Evolution and Gold: The California Story. For most of her career, Mary served as information officer for the state of California and the United States Geological Survey, and she acted in this capacity during the 1980 eruption of Mount St. Helens. She also edited the magazine California Geology, was president of the Earth Science Editors Association, and has taught earth science at San Francisco State University. Mary enjoyed many backpacking and driving trips into the Sierra Nevada from her California home base. She presently lives in New Mexico with a dog, a cat, and a friend.

Series Design: Design Enhancements: Design Development: Photo Research:

Barbara Jellow Beth Hansen Jane Tenenbaum Stephanie Rubin

Cartographer:

Hayden Foell

Composition:

Jane Rundell

Indexer: Text: Display: Printer and Binder:

Jean Mann 9/10.5 Minion ITC Franklin Gothic Book and Demi Everbest Printing Company

Field Guides,

Sharks, Rays, and Chimaeras of California, by David A. Ebert, illustrated by Mathew D. Squillante Field Guide to Beetles of California, by Arthur V. Evans and James N. Hogue Geology of the Sierra Nevada, Revised Edition, by Mary Hill Mammals of California, Revised Edition, by E.W. Jameson, Jr., and Hans J. Peeters Field Guide to Amphibians and Reptiles of the San Diego Region, by Jeffrey M. Lemm Dragonflies and Damselflies of California, by Tim Manolis Field Guide to Freshwater Fishes of California, Revised Edition, by Samuel M. McGinnis, illustrated by Doris Alcorn Raptors of California, by Hans J. Peeters and Pam Peeters Geology of the San Francisco Bay Region, by Doris Sloan Trees and Shrubs of California, by John D. Stuart and John O. Sawyer Pests of the Native California Conifers, by David L. Wood, Thomas W. Koerber, Robert F. Scharpf, and Andrew J. Storer Introductory Guides,

Introduction to Air in California, by David Carle Introduction to Water in California, by David Carle Introduction to California Beetles, by Arthur V. Evans and James N. Hogue Introduction to California Birdlife, by Jules Evens and Ian C. Tait Weather of the San Francisco Bay Region, Second Edition, by Harold Gilliam Introduction to Trees of the San Francisco Bay Region, by Glenn Keator Introduction to California Soils and Plants: Serpentine, Vernal Pools, and Other Geobotanical Wonders, by Arthur R. Kruckeberg Introduction to Birds of the Southern California Coast, by Joan Easton Lentz Introduction to California Mountain Wildflowers, Revised Edition, by Philip A. Munz, edited by Dianne Lake and Phyllis M. Faber Introduction to California Spring Wildflowers of the Foothills, Valleys, and Coast, Revised Edition, by Philip A. Munz, edited by Dianne Lake and Phyllis M. Faber Introduction to Shore Wildflowers of California, Oregon, and Washington, Revised Edition, by Philip A. Munz, edited by Dianne Lake and Phyllis Faber

Introduction to California Desert Wildflowers, Revised Edition, by Philip A. Munz, edited by Diane L. Renshaw and Phyllis M. Faber Introduction to California Plant Life, Revised Edition, by Robert Ornduff, Phyllis M. Faber, and Todd Keeler-Wolf Introduction to California Chaparral, by Ronald D. Quinn and Sterling C. Keeley, with line drawings by Marianne Wallace Introduction to the Plant Life of Southern California: Coast to Foothills, by Philip W. Rundel and Robert Gustafson Introduction to Horned Lizards of North America, by Wade C. Sherbrooke Introduction to the California Condor, by Noel F. R. Snyder and Helen A. Snyder Regional Guides,

Sierra Nevada Natural History, Revised Edition, by Tracy I. Storer, Robert L. Usinger, and David Lukas