Satellite geology and photogeomorphology : an instructional manual for data integration 9783642206085, 3642206085, 9783642206078

Table of contents :
Content: Pt. 1. Introduction --
pt. 2. The examples.

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Satellite Geology and Photogeomorphology An Instructional Manual for Data Integration

Lambert A. Rivard

Satellite Geology and Photogeomorphology An Instructional Manual for Data Integration

123

Lambert A. Rivard 201–300 St-Georges Saint-Lambert Québec J4P 3P9 Canada Email: [email protected]

Additional material to this book can be downloaded from http://extra.springer.com

ISBN 978-3-642-20607-8 e-ISBN 978-3-642-20608-5 DOI 10.1007/978-3-642-20608-5 Springer Heidelberg Dordrecht London New York Library of Congress Control Number: 2011934144 © Springer-Verlag Berlin Heidelberg 2011 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Cover design: deblik, Berlin Projektmanagement, typesetting and reproduction of the figures: Fotosatz-Service Köhler GmbH – Reinhold Schöberl, Würzburg Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com)

Preface

Satellite data analysis has now become a mainstream of much geological reconnaissance and detailed mapping. There are currently some 30 Earth Observation imaging satellites acquiring data daily, with ground resolutions ranging from 30 m to 0.5 m, with concurrent archives growing exponentially. In the author’s view satellite geology has tended to minimise, or overlook, the continuing value of archives of pre-satellite conventional vertical stereoscopic mapping air photography. This monograph is a portfolio of 97 data sets designed to demonstrate to students and workers in the fields of land geoscience and land management the value in preliminary site appraisals or mapping projects of the use of two data sources in a reciprocal combined manner – conventional stereo airphotos and 30 m ground resolution Landsat subscenes. “For every site, geomorphology is the first thing encountered”. While geotechnical knowledge is paramount, both quantitative and qualitative knowledge should be regarded as important. The initial role of the physical geologist is qualitative, to establish what geological phenomena exist in a site. “Once that is correctly decided, the subsequent investigations can readily be developed, given the requisite time and finance, to provide the degree of quantitative knowledge necessary” (Hutchinson, p38). Québec, March 2011

Lambert A. Rivard

Contents

Part I Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

1 The Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Advantages and Limitations of Airphotos for Photogeological Analysis, Interpretation and Terrain Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Airphotos Used in the Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Advantages and Limitations of Digital Satellite Imagery for Photogeological Analysis, Interpretation, and Terrain Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Acquisition of Satellite Images Used in the Book . . . . . . . . . . . . . . . . . . . . . 1.5 Resolution of Geounits in Downloaded Images . . . . . . . . . . . . . . . . . . . . . .

2

2 Classification of Photogeological Geounits . . . . . . . . . . . . . . . . . . . . . . . 2.1 Definition of Geounits and Variants as Delineation Units for Terrain Mapping . . . . . 2.2 Classification of Geounits and Variants . . . . . . . . . . . . . . . . . . . . . . . . . .

3 3 3

3 Examples of Data Integration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Principles of Analysis and Interpretation of Geounits and Variants in Airphotos and Digital Satellite Imagery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Examples of Integration of Imageries and Airphotos for Analysis and Interpretation of Geounits and Variants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Interpretative Texts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Examples with Geohazard Relations . . . . . . . . . . . . . . . . . . . . . . . . .

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5 5 5

Geological Time Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

Part II The Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Section 1 Magmatic Rocks and Structures . . . . . . . . . . . . . . . . . . . . . . . . . .

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Interpretations of Magmatic Rocks and Structures Group N Intrusive Magmas . . . . . . . . . . . . . . Group X Extrusive Magmas . . . . . . . . . . . . . Group P Pyroclastic Deposits . . . . . . . . . . . . . Group V Volcanic Structures . . . . . . . . . . . . .

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44 44 46 47 47

Section 2 Sedimentary Rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Interpretations of Sedimentary Rocks Group K Carbonates . . . . . . . . . . Group H Saline and Phosphatic Rocks . Group S Detrital Rocks . . . . . . . . . Group W Interbedded Sequences . . . .

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VIII

Contents

Section 3 Metamorphic Rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

85

Interpretations of Metamorphic Rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . Group R Cratonic Rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Group J Non-Cratonic Rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

96 96 97

Section 4 Geostructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

99

Interpretation of Geostructures . Group Diastrophic Rock Units . . Group Gravity Structures . . . . . Group Fault Line Traces . . . . . Group General Lineaments . . . .

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130 130 132 133 134

Section 5 Aeolian Deposits and Erosion Forms . . . . . . . . . . . . . . . . . . . . . . . 137 Interpretations of Aeolion Deposits and Erosion Forms Subgroup Et Inland Deposits . . . . . . . . . . . . . . . . Subgroup Ef Duneless Deposits . . . . . . . . . . . . . . . Subgroup Er Erosion Forms . . . . . . . . . . . . . . . . . Subgroup Ed Sand Dunes . . . . . . . . . . . . . . . . . .

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148 148 148 149 149

Section 6 Basinal Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 Interpretations of Basinal Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 Section 7 Fluvial System Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 Interpretations of Fluvial System Sediments . Subgroup Fu Upland Margin Units . . . . . . . Subgroup Fv Valley Fill Units . . . . . . . . . Subgroup Fw Holocene Deltas . . . . . . . . .

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178 178 179 182

Section 8 Marine Littoral Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 Interpretations of Marine Littoral Systems . . . Subgroup Br Bedrock Littorals . . . . . . . . . . . Subgroup Bw Wave and Current Formed Sediments Subgroup Bl Sea Ice Related Forms . . . . . . . . Subgroup Bf Holocene Coral Reefs . . . . . . . . . Subgroup Bt Tidal Regime Deposits . . . . . . . . Subgroup Bc Coastal Plains . . . . . . . . . . . . .

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216 216 217 219 220 221 222

Section 9 Glacial and Paraglacial Geosystems . . . . . . . . . . . . . . . . . . . . . . . . 225 Interpretation of Glacial and Paraglacial Geosystems . . . . . . . . . . . . . . . . . . . 230 Subgroup Gf Glaciofluvial Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 Subgroup Gt Paraglacial Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 Section 10 Periglacial-Related Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231 Interpretations of Periglacial-Related Forms . . . . . . . . . . . . . . . . . . . . . . . . 238 Subgroup Zm Cryoturbated Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 Section 11 Mass Movement Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 Interpretations of Mass Movement Materials Subgroup Mv Falls and Subsidences . . . . . . Subgroup Ms Slides . . . . . . . . . . . . . . . Subgroup Mf Flows . . . . . . . . . . . . . . .

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264 264 266 270

Part Introduction

I

2

1

Part I Introduction

The Data

1.1 Advantages and Limitations of Airphotos for Photogeological Analysis, Interpretation and Terrain Mapping Advantages The most familiar type of black and white airphoto film is sensitive to all visible radiation - so-called panchromatic film.

 They range in scale from 1: 3,180 to 1: 100,000, and from 1940 to 1991 in age.  24 countries are represented in six continents and five bioclimatic environments: – polar - 9 examples – tropical - 10 examples – arid - 33 examples – mid-latitude - 32 examples – alpine - 13 examples

1.3 Advantages and Limitations of Digital Satellite Imagery  The film provides excellent spatial resolution and for Photogeological Analysis, has a high information content.  Stereo cover is the most valuable aid for geological Interpretation, and Terrain Mapping interpretation.  Airphotos cost relatively little, and are readily available from numerous repositories of existing survey collections.  Multitemporal record of site changes are frequently available.

For many decades prior to the availability of digital satellite imageries the practical means of obtaining sought after “synoptic” views of terrain was by the use of assembled mosaics of air survey mapping photos numbering from a dozen to multiple hundreds.

Limitations

Advantages

 Airphotos cannot readily be processed by computer unless first digitized.  Airphotos display some radial displacement that must be corrected for topographic mapping but not for geological interpretation.

1.2 Airphotos Used in the Book The airphotos used in this monograph have been selected from the author’s archives. They are of three types:  59 stereo pairs of panchromatic black and white film. One photo is reproduced in the monograph, and both pairs are included in the extra material on the Springer website. They can be printed and viewed with pocket or mirror stereoscopes.  All the photo scales listed are nominal scales, i.e. the scale of a contact print from the air negative as flown. Reproduction in this monograph may have reduced the scale slightly.  19 mounted stereograms.  17 single photos.  2 interpretation maps

 Worldwide coverage gives access to all countries.  Long term repetitive coverage can provide cloudfree images of various seasons.  The synoptic view provides initial appreciation of a regional geological context.  Landsat data are free, in the public domain.  Digital terrain models (DTMs) at 30 m and 15 m resolution are available for many areas.  Sub-metric panchromatic resolutions are available on specific satellites.  A zoom (monoscopic) of a high resolution image can, in some instances, reveal details not resolved in the airphotos.  The ability to filter, enhance contrast and apply transformations to maximise geological information content (spectrolithologic mapping). Limitations  Images are largely monoscopic; expression of morphology is dependent on seasonal sun angle, azimuth illumination and spectral associations.  Current entry costs of off-nadir satellite programming and photogrammetric software for stereo cov-

L.A. Rivard, Satellite Geology and Photogeomorphology DOI 10.1007/978-3-642-20608-5_1, © Springer-Verlag Berlin Heidelberg 2011

2 Classification of Photogeological Geounits

erage are too high for many projects as are those for companies which offer such services.  The cost of obtaining existing higher resolution DTMs from many national mapping agencies is usually prohibitive.  The significant cost and time to acquire and operate an imagery processing system or purchasing custom-processed imagery from vendors.  The 30 m ground resolution of Landsat TMs restricts detection of some small size Geounits.

1.4 Acquisition of Satellite Images Used in the Book The Landsat scenes used in this monograph are courtesy of the U.S. Geological Survey. They were located and downloaded by Carla Hehner-Rivard using USGS Global Visualization Viewer. She cropped the selected scenes to the areas specified, enhanced the images by adjusting colour balances, brightness and contrast using the tools within Adobe Photoshop. With the exception of two MSS scenes, the images were imported from the Thematic Mapper or Enhanced Thematic Mapper satellites acquired between 1986 and 2010. The band combinations used are:  3-2-1 visible, for 70 examples.  7-4-2 middle infra-red, near infra-red, visible, for 18 examples.  4-3-2 near infra-red, visible, for 9 examples.  The area coverage of the images ranges from 170 to 25,000 km2.

1.5 Resolution of Geounits in Downloaded Images As indicated in the Table of Section 3.1, the size, shape, colour, and contrast with background determine the detectability and recognition of a Geounit in airphotos and satellite images. In the 30 m ground resolution of the downloaded TM images and the limited enhancements mentioned above, Geounits of photo scales larger than 1:15,000 are not resolved, e.g. Figures 72B, 84B, 94B.

3

Two examples, Figures 79B and 80B, illustrate the use of the associational principle of a functional relation of visible features with the presence of invisible Geounits.

2

Classification of Photogeological Geounits

2.1 Definition of Geounits and Variants as Delineation Units for Terrain Mapping Geounit - Photogeologically a Geounit, also referred to in texts simply as a Unit, is a portion of a tract of land having recognizable boundaries at given photo and imagery scales and whose overall homogeneity is a function of its genesis, composition, geologic structure and relief type. Variant – The Variant of a Geounit is a photo-distinguishable “facies” resulting from the action or occurrence of one or a number of environmental factors: genesis, topographic site, morphology, age, climatic environment, and diagenesis.

2.2 Classification of Geounits and Variants Rocks and unconsolidated sediments and structures need to be defined by standard schemes of nomenclature in order to assist in communications between geologists. The Units and their Variants in this monograph are related to the author’s teaching classifications of geohazard-related and stable Geounits. The combined classifications total 280 Units and 277 Variants: 50 Units and 47 Variants are presented in this monograph. Their relations to these typological categories are indicated by the heading of each Section. The combined classifications comprise 26 pages. Readers wishing to consult the geohazard classification are referred to Part III of the author’s text on that subject in the bibliography. The unpublished classification of “stable” geounits is available from the author on request.

4

Part I Introduction

The examples presented in Part II are organized into eleven Sections of the classifications as follows:

3

          

3.1 Principles of Analysis and Interpretation of Geounits and Variants in Airphotos and Digital Satellite Imagery

Magmatic rocks -16 examples. Sedimentary rocks -13 examples. Metamorphic rocks -5 examples. Geostructures -15 examples. Aeolian deposits -6 examples. Basinal sediments -3 examples. Fluvial sediments -8 examples. Marine littoral systems -15 examples. Glacial and paraglacial forms -2 examples. Periglacial-related forms -3 examples. Mass movement materials -11 examples.

Examples of Data Integration

The analysis and interpretation of airphotos and satellite images relies on a number of elements of terrain surfaces as they appear on hard copy reproductions or on screen. These are basic principles of classical photogeology. The following Table defines the basic attributes, contextual presence indicators of visual detection and recognition of photogeomorphic geounits which occur as an interplays of tectonic forces, denudation processes and climatic controls (see Section 2.1).

LOCATIONAL

Provides regional geological context, existing documentary and cartographic information of the regional terrain of a study area and anticipation of presence of specific geounits.

SPECTRAL

Tonal density - the direct or relative brightness of a surface aids discriminant grouping of exposed geounits, and can be an indicator of permeability or moisture status of surface materials. Colour - hue, saturation and density aid correlation to specific geounits. Texture - relative relief roughness or smoothness of an image or photo sub-area is a geounit indicator.

SPATIAL

Relief - three-dimensional stereoscopic grouping of slope steepness and orientation to sun aspect of a geounit. Shadowing relates to the geounit morphology and solar elevation and azimuth. Relief reflects the origin and composition of geounits and the erosional processes that have and are acting upon them. Drainage - variable channel densities and patterns are indicative of topographic, lithological and structural components of geounits. Geolineaments - the location, spacing, azimuth and group relationships of anomalously straight continuous or discontinuous traces of drainage channels, vegetation or relief are indicators of crustal and inter or intra-unit fracture or displacement. Pattern - spatial repetition or macro-arrangement and distribution of similar phenomena, e.g. drainages, colours, or a grouping of unlike features (e.g. lineaments and relief or colours). Similar patterns are frequent indicators of similar geounits; unlike patterns suggest unlike geounits.

ASSOCIATIONAL

Correlations of any two or more criteria that characteristically occur together in functional relationships lead to a convergence of evidence that can predict the occurrence of a specific geounit.

3 Examples of Data Integration

3.2 Examples of Integration of Imageries and Airphotos for Analysis and Interpretation of Geounits and Variants A basic concept of this monograph presents the twin sets of Figures in two-page spreads for necessary simultaneous viewing. These are examples that are intended to demonstrate how the interfacing of stereo airphotos and satellite images in visual qualitative photogeomorphology studies can yield more geospatial information than can be derived from either source independently. For example the multi temporal nature of the two data sets (up to 70 years), provides comparative information on such features as fluvial and coastal dynamics and mass movements (Figs. 62, 65, 92). Additionally, early photo sets frequently show exposed terrains of rural areas that are obscured in Landsat images by later industrial or urban developments (Figs. 37, 74, 81). The airphoto coverage in each satellite image is indicated by a frame.

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3.3 Interpretative Texts The Figure sets of each section are preceded by characterizations of their genetic classification context. The texts interpreting the Figures follow the examples of each Section. Throughout the texts specific geological terms are italicized and referred to the Figures in which they are explained.

3.4 Examples with Geohazard Relations Comments on geohazard relations are included for 44 of the examples in the monograph that have such relations. Small size Geounits such as Figs. 85, 86 and 94 are not detectable on TM images.

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Part I Introduction

Geological Time Scale The following time scale is a reference for the nomenclature used throughout the text EON

ERA

PHANEROZOIC

Cn CENOZOIC

PERIOD Q

Quaternary

EPOCH R – Holocene Pl – Pleistocene Po – Pliocene Mc – Miocene

T

Tertiary

Og – Oligocene E – Eocene Pe – Paleocene

M MESOZOIC

Pz PALEOZOIC

Pc PRECAMBRIAN Pr PROTEROZOIC Ar ARCHEAN (HADEAN)

K

Cretaceous

J

Jurassic

Tr

Triassic

Ku – Upper Kl – Lower

Pm Permian Cb

Carboniferous

D

Devonian

S

Silurian

O

Ordovician

C

Cambrian

Cbu – Upper Cbl – Lower

Bibliography

Acknowledgements As usual my indefatigable wife Carla has provided invaluable expert technical support in all phases of this monograph’s production. Without her help the book would not exist.

Bibliography Andrews JT (1972) Post glacial rebound, The National Atlas of Canada, Department of Energy, Mines and Resources, pp 35– 36 Bates RL, Jackson JA (eds) (1983) Dictionary of Geological terms. Third edition, Anchor Books, Random House, p 322 Berger Z (1994) Satellite Hydrocarbon Exploration, p 52, Springer-Verlag Breed CS et al (1989) Wind erosion forms In: ThomasSG (ed) Arid Zone Geomorphology, Belhaven Press/Halsted Press, John Wiley & Sons. pp 296-303 Brooks GR, Evans SG Clague JJ, Floods. In: BrooksGR (ed) A synthesis of geological hazards in Canada. GSC Bull.548, pp 101–125

7 DaviesJL (1977) Geographical Variation in Coastal Development. Longman, pp 172-173 GornitzV (ed) 2009) Encyclopeadia of Paleoclimatology and Ancient Environments, Springer Verlag, p 286 Hutchinson JN (2001) Reading the Ground: Morphology and Geology in Site Appraisal, Quarterly Journal of Engineering Geology and Hydrogeology, v 34, p 38 Martinez JD, Johnson KS, Neal JT (1998). Sinkholes in evaporite rocks, American Scientist, v86, pp 38-51 Medley EW (2001) Orderly Characterization of Franciscan Mélange, Felsbau 19 , No 4 pp 20-33 Mollard JD, Janes JR (1983) Airphoto Interpretation and the Canadian Landscape, Department of Energy Mines and Resources, p 21 Neal JT (1998) Playas and military operations, GAS Reviews in Engineering geology, vol. XIII: pp 166-168 Prest VK (1983) Canada’s Heritage of Glacial Features, Geological Survey of Canada Miscellaneous Report 28, pp 3943 Rivard LA (2009) Geohazard-associated Geounits, SpringerVerlag Waltham T (2002) Foundations of Engineering geology, second edition, Spon Press, pp 58–59

Part The Examples

II

Section 1 Magmatic Rocks and Structures

The variety of classified magmatic Geounits includes 24 Units and 27 Variants ordered in five Groups and six Subgroups. The Groups are:  N - Intrusive magmas are emplacements of magma in pre-existing rocks, (Figs. 1 to 5)  X - Extrusive magmas are igneous rocks that have been erupted onto the surface of the Earth (Figs. 6, 7)  P- Pyroclastic deposits are fragmental aggregates that are explosively ejected from a volcano, transported through the air and deposited downwind. (Figs. 8, 9)  V - Volcanic structures are forms built up by repeated subaerial eruptions of basic (low silica) magmas. (Figs. 10 to 16)  A - Epiclastic deposits are the result of surface processes of erosion, transportation and redeposition operating in volcanic terrains.

L.A. Rivard, Satellite Geology and Photogeomorphology DOI 10.1007/978-3-642-20608-5_2, © Springer-Verlag Berlin Heidelberg 2011

11

12

Fig. 1A

Part II The Examples

Section 1 Magmatic Rocks and Structures

Fig. 1B

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Fig. 2A

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Section 1 Magmatic Rocks and Structures

Fig. 2B

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16

Fig. 3A

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Section 1 Magmatic Rocks and Structures

Fig. 3B

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18

Fig. 4A

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Section 1 Magmatic Rocks and Structures

Fig. 4B

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Fig. 5A

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Fig. 5B

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Fig. 6A

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Fig. 6B

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Fig. 7A

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Fig. 7B

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Fig. 8A

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Fig. 8B

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Fig. 9A

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Fig. 9B

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Fig. 10A

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Fig. 10B

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Fig. 11A

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Fig. 11B

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34

Fig. 12A

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Fig. 12B

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Fig. 13A

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Fig. 13B

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Fig. 14A

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Fig. 14B

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Fig. 15A

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Fig. 15B

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Fig. 16A

Part II The Examples

Section 1 Magmatic Rocks and Structures

Fig. 16B

43

44

Interpretations of Magmatic Rocks and Structures Group N Intrusive Magmas Subgroup Np Primary Emplacement Bodies Figure 1 dykes (class. Np1.1) Characterization Dykes are vertical tabular igneous intrusions that cut across the mass or bedding of country rock. They are injected most easily along pre-existing fractures, and range in thickness from millimetres to tens of meters. They may be traced for meters to hundreds of kilometres. Their detection is related to factors explained for General Lineaments (Figs. 45 to 49). Dykes that are circular in plan are termed ring dykes. Fig. 1A (W104 50 N37 29) contact scale 1: 20,000, source USGS Late Oligocene granitic dyke sets 15 to 30 meters high and 1 to 30 m thick in these stereo photos in southern Colorado are cutting beds of lower Eocene shales and sandstones. Fig. 1B (Bands7-4-2), 05 Nov. 2010, area coverage 3,500 km2 The image shows the dykes to have emanated from two snow-capped volcano-like structures to the southwest. These are 4,000 m elevation Mid-Tertiary granitic stocks of the Sangre de Cristo Uplift on the eastern margin of the Sangre de Cristo Mountains on the left. They rise 1,800 m above the green forested and dissected surrounding rocks of the Southern Rockies piedmont to the southeast. The broad blue ridge area in the mountains marks snow-covered peaks at 4,300 m elevation. The brown lineament visible in the center of the snow ridge is a large normal fault (Fig. 42) separating Precambrian intrusive rocks on the west from folded (Fig. 36) sandstones and shales on the east. The beige terrain on the east is lightly cultivated Cretaceous sediments of the High Plains Raton Basin.

Part II The Examples

Figure 2 batholithic plutons in humid climates (class. Np3.4) Characterization Batholithic plutons are large, >100 km², irregular bodies of intrusive igneous rocks exposed by subaerial erosion, but frequently covered by forest. A surficial regolith of unconsolidated material of variable thickness developed by chemical weathering is generally greater in humid than in mechanical weathering of more arid climates (Fig. 3). Exposures < 100 km² are termed stocks. Fig. 2A (E09 30 N05 54) contact scale 1: 50,000, source IGN, France This airphoto pair is in densely forested granite (quartzitic) of the northwestern Precambrian portion of the Congo Craton in western Cameroon. Local terrain ranges from 200 to 800 m elevation, with relief ranging from 100 to 300 m. Crystalline fracture-control of the brittle rocks is evident through the dense forest cover. Stereo-detected mesoscale fracture traces, (Fig. 45) one to three kilometres long, have been drawn on one of the photos. Fig. 2B (Bands 7-4-2), 12 Dec. 1986, area coverage 1,050 km2 Sets of master joints are visible throughout this image. The local NW-SE oriented river crossing the photos may be a fault. Macroscale north-south striking lineaments (see mesoscale fracture traces of Fig. 45) in the higher terrain on the right are probable faults associated with a possible post-tectonic intrusion. Ribbons of settlement clearings in this entirely forested area are visible on the west of center of the scene. Figure 3 batholithic plutons in arid climates (class. Np3.5) Characterization In contrast with the rounded topography of humid environment occurrences, weathering of pluton outcrops in arid environments is dominated by physical processes which result in a topography of more rugged bare surfaces and associated joint systems (Fig. 45). (This Figure introduces the characteristic photogeological advantage of generally good to excellent exposures of rocks and structures in arid climate.)

Section 1 Magmatic Rocks and Structures

Fig. 3A (E04 15 N24 00), contact scale 1: 50,000, source IGN, France This photo pair is located in Upper Proterozoic crystalline rocks of the Hoggar craton (Fig. 30) in the southern Algerian Sahara. It is centered on a typically irregularly fractured (Fig. 45) granitic stock with joint systems. The fractures are sand-filled. The outcrop is flanked left and right by R1 descriptors of foliated metamorphic rocks (Fig. 30). The location is shown at the bottom of Fig. 5B. Fig. 3B (Bands 4-3-2), 17 Sept. 2010, area coverage 1,786 km2 The image shows the photos to be in a local outcrop zone of the orogenic belt depicted and described in Fig. 51B. The bordering foliated rocks are gneisses on the right and peneplaned schists on the left. The pale terrain of the rest of the image is covered in sand sheets (Fig. 51). Figure 4 plutons in Late Alpine glaciated Environments (class. Np4.2) Characterization Occurrences of plutons in high mountains are subject to the activity of surface glacial erosion processes (plucking, crushing, shearing, abrasion), and other mass wasting processes. The resultant dominant topographic forms are serrated sharp peaks, pinnacles, basins and U-shaped valleys. Fig. 4A (E013 N42 52), contact scale 1: 60,000, source IGN, France This photo pair in the central French Pyrenées covers the eastern portion of a deeply glaciated Carboniferous granite stock intruded into morphologically distinctive folded Devonian sedimentary rocks. Elevations in the stock range from 2,000 to 3,000 m a.s.l. The surrounding country rock averages 2,000 m elevation. Small solid arrows in the stock point to rock glaciers (Fig. 86A) in some of the numerous cirques. The broad open arrows north of the stock point to glaciated valleys in the sedimentary rocks with their associated marginal moraines (along the sides of a glacier, Fig. 42, a valley version of Fig. 83). Valleys on the east and south do not appear to have been glaciated. The two lakes in the southwest corner are hydroelectric power reservoirs at 1,819 and 1,856 m elevation.

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Fig. 4B (Bands 3-2-1), 05 Sept. 2007, area coverage 4,500 km2 This image shows the full extent of the photo pluton delimited by a curved valley westward. Other glaciated snow-covered plutons are at 2,500 to 3,000 m elevations. The southern occurrences are in Spain. Timberline here is at 1,500 m so much of the brownish terrain is in alpine tundra vegetation. Lower forested land is dark green. The north margin of the scene is in folded Cretaceous sedimentary rocks of the forested front ranges of the Pyrenees and the cultivated foothills at elevations of 400 to 600 m.

Subgroup Nr Residual Masses Figure 5 granitic plains (class. Nr3) Characterization Granitic plains are physically-weathered level or depressional occurrences of intrusions in arid climates whose surface is mainly covered by colluvial rubble derived from the disintegration of coarse-grained granites. The large coefficient of thermal expansion of quartz and feldspar in the granites in arid climates causes rapid crumbling of the outcrops. Fig. 5A (E04 26, N24 25), contact scale 1: 50,000, source IGN, France This stereo triplet covers 50 km2 of a granitic plain in southeast Algeria covered by a veneer of colluvial rubble and sand sheet (Fig. 51). Small parallel linear outcrops are dykes (Fig. 1). The R1 area on the right is a segment of a belt of foliated metamorphic rocks (Fig. 30). Ed2 is a small sand dune complex (Fig. 54). Fig. 5B (Bands 3-2-1), 17 July 2010, area coverage 18,125 km2 This large area subscene is centered on a 120 km long by 25 km wide occurrence of a set of merged stocks (Fig. 2) flanked by outcrops of dark, foliated metamorphic rocks in the Hoggar Craton (Fig. 51). The outcrops on the east are cut by three prominent northeast oriented strike-slip faults (Fig. 44). Locations of Figures 3 and 30 are indicated.

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Group X Extrusive Magmas Figure 6 local basalt slope flow (class. X1.1) Characterization Basalt is a fluid fine-grained basic (low silica) rock that issues from a volcano crater or fissure and solidifies by cooling. A flow of lava down a slope typically extends for long distances as a relatively narrow stream well beyond the steep slopes of stratovolcanos. The flow will channel into existing gullies and ravines and may spread out of valley margins. The morphology of young flows reflects the process of flow. Superimposed flows and gas pocket depressions combine to produce characteristic rugged flow surfaces. Geohazard relations Property damage rather than loss of life is the principal hazard associated with these flows during an eruption. If such flows come into contact with ice or snow they can generate debris-mud flows (Fig. 60). Fig. 6A (W130 32 N57 51), contact scale 1: 40,000 source Courtesy of Natural Resources Canada The stereogram show the lower 4 km of a 13 km long, 1 to 2 km wide ropy, braiding basalt slope flow on the north slope of Edziza shield (flat domical shape) Volcano, 2,590 m in north central British Columbia. The flow, which postdates the last episode of regional glaciation, descended 1,310 m in elevation through forested land into the Klastline River valley from its point of origin in the breached central crater. Relief on the flow is about 5 m. The light grey tone may be caused either by lichen or bare rock. Fig. 6B (Bands 3-2-1), 05 Aug. 1999, area coverage 1,065 km2 This image shows multiple rust-colored flows that have welled out of vents on the north slope of the volcano. These flows have remained almost unchanged since they were formed postglacially about 1300 BP. The dark deposits adjoining the lava stream on its right are airfall tephra. The dark green forested area in the Klastline valley at the north edge of the scene is a set of lavas older than the photo flow. These lavas flowed from a small 60 m high vent cone and temporarily dammed the river.

Part II The Examples

The 1.5 km diameter summit crater is filled with a flat field of stagnant ice. Alpine glaciers and rust-colored glacial morainal ridges mantle the edifice down to an elevation of 2,100 m. The forested valley north of Nattlude lake is in glacial till (Fig. 83) and alluvial gravel. Light green terrain is undivided colluvium (weathered bedrock and glacial deposits) above timberline. Figure 7 disturbed, dissected basalts (class. X1.3) Characterization The variable dissection of Pre-Cenzoic basalt successions results from their weathering, deformation and/ or metamorphism (Figs. 30 to 34). Fig. 7A (W65 43 S21 26), contact scale 1: 50,000 Source: Universidad San Andres, Bolivia. This stereogram in southern Bolivia, shows the rugged upland topography of dissected Tertiary basalts and dacites similar to rhyolite in Fig. 10. The line and arrow symbol indicates an anticline structure (Fig. 36) in a ridge of sedimentary rocks. The bright valley (Tupiza) numbered 2 is in weaker sediments. Unit 4 is a second anticlinal structure (Fig. 38). Fig. 7B (Bands 4-3-2), 20 March 2007, area coverage 1,020 km2 The image shows the photo area to be in a zone of thrust faults (faults with a dip of 45º or less) and folds flanked by disturbed and dissected basalt flows on the right below undissected flows in upper right, and eastdipping weak sediments on the west. The location is in the fold and thrust belt of the southern Cordillera Oriental of the central Andes. The lavas are associated with Mid-Tertiary sediments which were deposited on Paleozoic basement rocks at the same time (synsedimentation) as the fault lines. The western edge of the scene is a suite of interbedded highly deformed and eroded Paleozoic sandstones and shales. Valley floors are at 2,800 m elevation, uplands reach 4,000 m. Red areas in the braided river valleys (Fig. 60) are irrigated farmland.

Section 1 Magmatic Rocks and Structures

Group P Pyroclastic Deposits Figure 8 maar craters (class. Pt2) Characterization A maar is a relatively round crater less than 10 km in diameter produced by phreatomagmatic eruptions (rising magma interacting with groundwater or surfacederived water). It is surrounded by low walls of ejecta with rims dipping gently outward. The craters are often filled with water in humid climates. Fig. 8A (W116 04 N38 23), contact scale 1: 30,000, source USGS The large crater in the photo is a 1,050 m wide by 130 m deep 40 ka maar surrounded by lava flows and small, monogenetic steep-sided cinder cones in central Nevada. The crater is filled with an alluvial fan (Fig. 58) and some white evaporites (Fig. 56). The broad 600 ka flow northeast of the maar issued from vents in the cinder cone area and encroached on an evaporite-filled dry wash. Fig. 8B (Bands 4-3-2), 19 Sept. 2010, area coverage 2,250 km2 The image shows the maar photos to be in the center of the dark 40 km long by 10 km wide Lunar Craters Pleistocene volcanic field (Fig. 16) ranging from 1,600 to 2,200 m in altitude. The field contains 95 cones and other flows. The white playa in the center is Lunar Lake. Older tabular grey lava flows are on the left of the field. The volcanic upland is flanked by alluvial fans and pediments sloping down to typical regional dry washes (intermittent stream channels) and evaporite-filled playas (Fig. 56). The area is in the center of the Basin and Range physiographic province in central Nevada. Red circles are center pivot irrigation sites. Figure 9 tuff rings (class. Pt3) Characterization A tuff (consolidated pyroclastic material) ring is a hydrovolcanic eruption caused when rising magma mixes with shallow groundwater and explodes violently. The deposits of the eruption build up inward dipping rim rings of bedded tuff with steep outer slopes around the vent. The crater floor which is higher than surrounding terrain is usually filled with lava.

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Fig. 9A (W110 05 N 35 29), contact scale 1: 54,000, source USGS Four Pliocene tuff rings are circled in red in the center photo of a stereo triplet in northeast Arizona. The two bright circled structures on the right are diatremes (fragment-filled volcanic pipes). The flat rhyolite (Fig. 10) lava mesa tongue on the left is 100 m above the Pliocene sandstone of the surrounding ground at elevation 1,800 m. Fig. 9B (Bands 4-3-2), 09 Oct. 2010, area coverage 3,900 km2 The image shows that the photo triplet is located in the center of a 2,500 km2 monogenetic volcanic field of 300 scattered late Miocene volcanic centers, including scattered lava mesas, cinder cones and maars. This is the Hopi Buttes field in the Cretaceous Black Mesa Basin on the southern Colorado Plateau in northeast Arizona. The mesas are erosional remnants of volcanos. Scattered light grey areas are gypsiferous (Fig. 23) deposits.

Group V Volcanic Structures Subgroup Vs Viscous Lava Structures These Units are composed of acidic lavas such as rhyolite that have internal resistance to flow. Figure 10 autonomous domes (class. Vs1) Characterization Autonomous domes occur in isolation as relatively small-volume, circular, generally convex accumulations of rhyolitic lavas erupted at low rates, resting insitu above their source vent. Lateral flow is inhibited by the lava viscosity and quick cooling following extrusion. Dome diameters vary from a few meters to several kilometres. Heights vary from a few meters to greater than 1 kilometre. Domes grow by repeated injections of lavas which create internal foliate structures.

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Fig. 10A (W67 43 S 20 54), contact scale 1: 40,000, source Universidad San Andres, Bolivia Five terrain Units associated with this dome have been delineated on the stereogram:  Unit 1 is the 2,300 m diameter 450 m high Holocene to Miocene slightly dissected dome.  Unit 2 is a one km wide also dissected apron of sloping Miocene to Oligocene tephra.  Unit 3 occurrences are plains of Miocene to Oligocene tephra.  Unit 4 are Quaternary alluvial and aeolian deposits.  Unit 5 are saline playa deposits (Fig. 56). Fig. 10B (Bands 4-3-2), 24 May 1999, area coverage 500 km2 This view, 35 km north of Fig. 15, shows the dome to be southeast of other dark brown conical elements of the Uyuni complex of volcanic centers in the southern Altiplano morphotectonic province. The complex is a 60 km wide volcanic field on the south side of the Uyuni playa (Fig. 56) consisting of some 20 major and numerous minor volcanic centers extending at least 70 km southward. The extensive bright playa evaporite deposits surround the centers. Figure 11 domes in cones (class. Vs1.1) Characterization This dome Variant, commonly named tholoid, occurs within the craters of Vc1 stratovolcanos (Fig. 14), shield volcanos (Fig. 6) and calderas (igneous activity that results in the collapse and near destruction of strato or shield volcanos). Fig. 11A (E153 16 S28 24), contact scale 1: 38,000, source Twidale CR, Foale MR, (1969) Landforms Illustrated, Thomas Nelson (Australia), p 71, ill. 22 This quadruplet stereogram in the northern Australian Tablelands shows the 1,156 m high forested Mt Warning tholoid with ring dykes (Fig. 1). Fig. 11B (Bands 3-2-1), 10 Sept. 2010 area coverage 2,090 km2 The image shows the tholoid to be in the 30 km diameter early Miocene Mt Warning caldera which is the central complex of the 100 km wide ancient Tweed shield volcano (Fig. 6B). A semicircle of forested basalt cliffs form the western side of the structure. Erosion has been extensive forming a large cultivated erosion caldera valley around the tholoid.

Part II The Examples

Mt Warning volcano erupted when it moved over the East Australian Hotspot 23 million years ago. (Hotspots are magma conduits from the Earth’s upper mantle.) Figure 12 flow-dome complexes (class. Vs1.2) Characterization This Variant differs from the parent Unit of Fig. 10 by the presence of coulees (Fig. 13) which flow from the dome as relatively short lobes or accumulate as corrugated aprons around the base of the dome. Flow lobes lying on a sloping surface are the most extensive. Fig. 12A (W121 30 N41 36), contact scale 1: 20,000, source USGS The stereomodel shows the flow-dome complex of Glass Mountain on the Modoc volcanic plateau of northeast California. It consists of two obsidian (volcanic glass) flows from the summit dome at 3,395 m. The flows are probably less than 1000 years old. Fig. 12B (Bands 3-2-1), 01 Oct. 2010, area coverage 3,900 km2 This image shows the flow-dome complex to be on the east rim of the Medicine Lake caldera of a related larger not distinguishable shield volcano. The caldera is 7 by 12 km in extent, but is entirely buried by the dark lavas at elevations from 2,200 to 2,300 m which reach westward as far as another bright flow-dome Unit. These lavas form a highland rising to 900 m above the surrounding terrain. The light grey Units on the south and the darker grey Unit on the north are very recent basalt flows. A number of small cinder cones (tephra) are visible on the north side of the caldera area. The white saturated areas surrounding the caldera on the east and north are barren basalts of the Lava Beds National Monument. Some attempts at irrigated agriculture are visible in the light grey area on the left. The speckle pattern in the lower left is blocks of clear cutting in forest land on Tertiary lavas at lower, 1,600 m elevation. Figure 13 coulees (class. Vs2) Characterization Coulees are Units that have aspects of both lava domes of Fig. 10 and lava flows of Fig. 6. They are relatively short, flat-topped and steep-sided extrusions of viscous lava concentrated to one side of a vent.

Section 1 Magmatic Rocks and Structures

Fig. 13A (W66 29 S19 51), contact scale 1; 40,000, source Universidad San Andres, Bolivia This stereogram shows the five km long by two km wide Nuevo Mundo coulee of Holocene dacite (similar to rhyolite Fig. 10) in the central Andes volcanic zone of southwest Bolivia. The edifice height is 738 m and has the characteristic flow ridges on its surface resulting from folding during emplacement of surface layers. The small cone northeast of the lake is the source vent. Fig 13B (Bands 4-3-2), 02 Aug. 1994, area coverage 2,160 km2 This image shows the coulee to be the southern occurrence of a group of four that erupted along a northsouth trending fault on the western margin of the Cordillera Oriental. The coulees and much of the image area to the east and northeast are partly covered by white ash and pumice (tephra) from a recent eruption. The range of glaciated peaks west and southwest of the photo area are basalts that probably erupted from a fault parallel to that of the coulees. The smoother area east of the peaks eroded by a number of glacial moraines (Fig. 42) is a series of pyroclastic flows (explosive eruptions of viscous magmas which expel fragments of materials from a conduit) that antedate the coulees. Red areas are irrigated land.

Subgroup Vc Major Conical Structures Figure 14 stratovolcanos (class. Vc1) Characterization The mechanism of emplacement of a stratovolcano begins when a magma, normally less dense than surrounding rock, rises buoyantly toward the surface following a line of weakness. As the magma nears the surface, the attendant decrease in pressure permits expansion of dissolved gases which then drive the eruption vertically, the only direction in which it is free to expand. Repeated eruption of tephra (clastic materials of Group P) and lavas (Fig. 6) complement each other in building an interbedded conical landform. These structures can rise from about 400 m to as high as 5 km above their bases; their diameters can range from 1 to 60 km. Average slopes range from 15° to 30°.

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Most stratovolcanos occur near the edges of tectonic plates. In a typical year an average of 50 volcanos actually erupt. Geohazard relations The infrequency of volcanic events within the short time-scale of human history is one of their most dangerous features. Erupting volcanos can generate a variety of primary hazards including pyroclastic flows, high concentrations of gas-particles from glassy pumice to 1 to 5 m diameter blocks that travel along the ground at velocities ranging from 10 to several hundred meters per second. They bury and destroy everything in their path; airfall tephra (clasts 2 to 64 mm in size) endanger life and property by burial; and lava flows (Fig. 6) damage property. Secondary hazards are epiclastic (secondary erosion) debris avalanches that are as destructive as pyroclastic flows. Dissolved gases and acids released during eruptions can be noxious. Fig. 14A (E152 12 S04 14), contact scale 1: 15,300, source personal archive This stereogram of 500 m Mt Tavurvur volcano, a subvent of Rabaul Caldera at the northeastern tip of New Britain Island in eastern New Guinea was taken in January 1944. The volcano has been repeatedly active (15 eruptions) since 540 AD. An eruption in 1937 caused 507 deaths, and one in 1994 (Fig. 14B) forced the abandonment of the town of Rabaul. The volcano continues to erupt, depositing ash daily into the waters of the caldera (Blanche Bay). Fig. 14B (Bands 7-4-2), 11 Oct. 1994, area coverage 1,225 km2 This image, oriented 40 degrees to northwest, was acquired by the Synthetic Aperture Radar aboard the Space Shuttle Endeavour a month after the destructive eruption of 19 September. The eruption deposited 75 cm of ash, appearing as magenta in the image, on the town, nearby villages, and on the slopes of Vulcan volcano on the west side of the caldera bay. This situation is similar to that of the Medicine Lake caldera of Fig. 12B. Popcorn clouds cover other volcanic vents on the peninsula. The lineament on the land projection in the rightcenter is an airstrip. The land on the west consists of Plio-Pleistocene dissected lava flows rising to 150 m.

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Part II The Examples

Figure 15 dissected cones (class. Vc1.1)

Figure 16 volcanic fields (class. Vc4)

Characterization Because they are high topographic features, stratovolcanos are very prone to mass wastage and are being continually degraded. Erosion features include breached cones, sector breaches, collapse scars, and gullies. These result from the action of lava, tephra, debris flows (Fig. 60), and debris avalanches (extremely fast slides occurring on steep slopes) of epiclastic (secondary) erosion and glaciation.

Characterization Volcanic fields are areas containing many (10 to 100) monogenetic eruption centers. Individual eruption centers form small size structures, base diameters are generally less than 2,000 m and heights are 400-450 m. They consist of Vc1 lava cones, Vs1 domes (Fig. 10), and Vp2 maars (Fig. 8). The fields range in extent from 1,000 to 8,000 km2.

Fig. 15A (W67 36 S21 14), contact scale 1: 40,000, source Universiadad San Andres, Bolivia This stereogram shows the Tertiary/Quaternary volcano Cerro Khala Katin at San Agustin on the Altiplano of southwest Bolivia. Zone d is the breached cone. Zone y is a collapse scar. The area on the left marked Vc1 is an adventive cone visible on the Landsat image. Fig. 15B (Bands 4-3-2), 15 Sept. 2000, area coverage 3,024 km2 The image, 35 km south of Fig. 10, shows the Unit in its location in the Uyuni vent complex described in that Figure. The cone, at elevation 5,300 m is some 1,500 m high. The darker smooth appearing deposits are mainly Holocene lavas. The lava flows extend in two directions, 8 km on the left and a 12 km tongue northward from the cone. Holocene Pyroclastic deposits (tephra of Group P) lie east and northeast of the volcano and are typically much dissected. The pale beige deposits in the southwest of the scene are pyroclastic flows from vents to the west southwest of the scene. These originate when the density of an ash-laden column becomes greater than that of the atmosphere; gravitational collapse occurs, generating a flow.

Fig. 16A (E14 08 N40 50), source USGS This sketch map covers the 13 km diameter, active, monitored, Phlegrean Fields multi vent complex caldera at Naples, Italy. Fig. 16B (Bands 4-3-2), 19 Aug. 2009, area coverage 2,925km2 This image of the sketch map area shows the entire multi-vent complex which is sited on an uplifted seabed. The red depression is a post-caldera collapse. The 46 km2 island of Ischia on the left is a related volcanic complex within a caldera closely encircling the island below water. Mt Vesuvius is on the right, and Sorrento Peninsula of Mezoic limestones is in the lower right. The white zone in the lower right of the map area is the developing port of Bagnoli, Naples, with the larger of its 30 wharves and quays visible just to the right of the map edge. Red areas are forested.

Section 2 Sedimentary Rocks

Sedimentary rocks cover approximately 75% of the world’s surface comprising 20 Units and 13 Variants ordered in five Groups and three Subgroups. The Groups are:  K – Carbonates are rocks formed of the carbonates of calcium, magnesium, and/or iron (Figs. 17 to 22).  H – Saline and phosphatic rocks are composed of halite or any soluble salt – evaporites (Fig. 23).  S – Detrital rocks also termed clastic are rocks which were derived from fragments of pre-existing rocks (Figs. 24 to 26).  W – Interbedded sequences are beds lying between or alternating with others of different character (Figs. 27 to 29).  D – Duricrusts are indurated horizontal layers of silica, alumina and iron oxide in varying proportions occurring as resistant caprocks or near the surface in semi-arid and tropical wet-dry climates.

L.A. Rivard, Satellite Geology and Photogeomorphology DOI 10.1007/978-3-642-20608-5_3, © Springer-Verlag Berlin Heidelberg 2011

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Fig. 17A

Part II The Examples

Section 2 Sedimentary Rocks

Fig. 17B

53

54

Fig. 18A

Part II The Examples

Section 2 Sedimentary Rocks

Fig. 18B

55

56

Fig. 19A

Part II The Examples

Section 2 Sedimentary Rocks

Fig. 19B

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58

Fig. 20A

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Section 2 Sedimentary Rocks

Fig. 20B

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60

Fig. 21A

Part II The Examples

Section 2 Sedimentary Rocks

Fig. 21B

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Fig. 22A

Part II The Examples

Section 2 Sedimentary Rocks

Fig. 22B

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Fig. 23A

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Section 2 Sedimentary Rocks

Fig. 23B

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66

Fig. 24A

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Section 2 Sedimentary Rocks

Fig. 24B

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68

Fig. 25A

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Section 2 Sedimentary Rocks

Fig. 25B

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Fig. 26A

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Section 2 Sedimentary Rocks

Fig. 26B

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Fig. 27A

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Section 2 Sedimentary Rocks

Fig. 27B

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Fig. 28A

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Section 2 Sedimentary Rocks

Fig. 28B

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Fig. 29A

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Section 2 Sedimentary Rocks

Fig. 29B

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Part II The Examples

Interpretations of Sedimentary Rocks

Subgroup Kp Holokarst Residual Terrain

Group K Carbonates

The term Holokarst denotes Geounits where limestone solution processes dominate the entire area.

Carbonate rocks make up 20% of the worldwide sedimentary rock cover. “Limestone is the only common rock soluble in water. It dissolves in rainwater enriched by carbon dioxide derived from organic soils so solution processes and results are on a large scale on limestone plateaus in areas of warm, humid climates. Karst features are erosional forms produced by the solution on bare rock surfaces, beneath the soil at rockhead, and within the rock.’’ T. Waltham 2002.

Figure 17 pyramid/labyrinth karst terrain (class. Kp2) Characterization The forms of this Unit, which occur in humid tropical climates, include conical haystack rounded hills or isolated towers up to 150 m high with almost vertical slopes and canyon-like labyrinths of deep solution trenches at the intersections of major joint sets.

Geohazard relations Karst terrains are agents of rock falls, subsidence, and solution.

Fig. 17A (E110 48 S08 10), contact scale 1: 50,000, source Courtesy of HTh Verstappen, 1977

 Rock falls (Figs. 87, 88, 89) occur in zones of joint widening at the margins of karst plateaus.  Subsidences (Figs. 90, 91) are due to the cavernous nature of limestone.  Solution (Figs. 17 to 22) groundwater circulating along joint and bedding planes dissolves the carbonate rock which results in collapse, producing surface sinkhole depressions also termed dolines.

This infrared stereogram triplet shows six km of the characteristic pyramid morphology of the Unit terrain in Upper Miocene carbonates near the Giritontro dry valley (Fig. 20) on the southeast coast of Java, Indonesia. Fig. 17B (Bands 7-4-2), 21 June 2000, area coverage 3,750 km2 A synoptic view shows systems of regional parallel east-west striking lineaments along 75 km in this region that are only visible in two 1.5 kilometer segments in the lower right of the photo model. These have been described as bedding, but may also reflect tectonic outward sliding of the strata from 325 m elevation inland in the image coverage that were deformed by gravitational flow of the upper crust and its sedimentary cover. Land cover/land use combinations are of rust covered kampong areas (hamlets) and green natural forest. A second entrenched valley 50 km eastward is apparently dry in the image but is not. Some coastal settlements are visible just west of it. The shore is a low rock cliff (Fig. 67) 30 to 60 m high bordering the Java Outer Arc Basin with depths of 200 to 1,000 m offshore. The basin is adjacent to the 7,000 m deep Java Trench. The subduction zone of the Australian Plate boundary is 250 km to the south. There has been hydrocarbon exploration offshore of this coast.

Section 2 Sedimentary Rocks

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Figure 18 pyramid/labyrinth karst terrain (class. Kp2)

Fig. 19B (Bands 3-2-1), 14 Aug. 2010, area coverage 2,250 km2

Characterization (see Figure 17)

This image shows the polje to occur at elevation 815 m within a 1,100 m high barren limestone horst-like structure (an uplifted crustal unit bounded by faults). The mass tourism area of Malia is on the north coast, the tourist port of Agios Nikolaos is on the east coast.

Fig. 18A (W78 35 N18 25 approx.), contact scale 1: 25,000, source personal archive This stereo pair covers a 44 km2 area in Eocene limestones of northwest Jamaica. The physiography of this pyramid karst terrain is controlled by block faulting, evidenced by the local fault traces (Fig. 42) cutting the outcrop. Fig. 18B (Bands 3-2-1), 03 Feb. 2010, area coverage 1,065 km2 This image of the forested 400 km2, 400 to 500 m elevation reaching to 900 m Cockpit Country elevated in the Miocene shows a system of major north-south through-going lineaments (macro scale fracture traces of Fig. 45) suggesting that the region’s pyramid karst morphology is divided into tectonically-controlled structural blocks The area is bounded on the north by a major fault.

Subgroup Kn Holokarst Erosional Terrain Figure 19 poljes (class. Kn1) Characterization Poljes are karst Units of generally elongated, closed depressions aligned along structural trends, frequently along axes of folds or along faults. They have a flat floor generally veneered with alluvium, and surrounded by steep walls of limestone. They are caused by laterally directed corrasion (abrasion). Fig. 19A (E25 28 N35 11), contact scale 1; 30,000, source Photo Interprétation Éditions ESKA, France This stereomodel of the Lassithi polje in eastern Crete shows a 20 km2 polje in Mesozoic carbonates. The Unit is clearly delimited by topography. The polje floods regularly at the end of each winter as evidenced by the rectilinear pattern of field boundaries and drainage ditches to supplement the stream drainage in the northwest corner. Local villages (small black circles) are located around the margins of the basin.

Figure 20 fluviokarst terrains (class. Kn2) Characterization This Unit is formed by the combined action of fluvial and karst processes in limestone areas. The pattern of surface stream channels is in evidence as dry valleys and much of the drainage is underground. Fig. 20A (E02 18 N43 32), contact scale 1: 30,000, source IGN, France This stereomodel at La Brugière in the southeastern extremity of the Aquitaine Basin in southern France shows a system of dry valleys on a karst plateau. The bare appearance of the plateau (partly a military reservation) contrasts with the land use on the hilly weak sandstone terrain (Fig. 24) south of the delimited meandering (Fig. 63) Agout River terraces. Both Units are Eocene. Fig. 20B (Bands 3-2-1), 14 Nov. 2006, area coverage 1,215 km2 This image shows the photo area to be in an embayment of Tertiary carbonate and detrital rocks of the southeast Aquitaine Basin in the forested uplands of the Montagne Noire, the southern extremity of the Massif Central (also covered by Fig. 38B 60 km eastward). The western margin of the upland is a fault contact. The limited fluviokarst area is evidently reverting to forest. The larger towns of Castres to the north of the photo area and Mazamet to the south are resolved as rust zones.

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Subgroup Kc Amorphous Carbonates Figure 21 fossil reefs (class. Kc1) Characterization Fossil reefs are lens-shaped masses of coral reefs (Fig. 73) that have developed in geologically ancient basins and occur today as resistant outcrops in sedimentary rocks. They range from small-scale patch structures to formations hundreds of kilometres long and may be up to several hundred meters thick. Fossil reefs within a sequence of sedimentary rocks provide a discontinuity which may serve as a trap for fossil fuels. Fig. 21A (E05 56 N43 11), contact scale 1: 70,000, source IGN, France A 12 km long strike-slip faulted (Fig. 44) outcrop of a Lower Cretaceous fossil reef is delineated on the center photo of a triplet in southern France. The ridges to the north are Upper Jurassic dolomites. The partly cultivated depression is a faulted graben (Fig. 29) exposing Upper Triassic shales and marls. Fig. 21B (Bands 7-4-2), 25 July 1999, area coverage 1,770 km2 The image shows the photo area to be at the eastern end of a 55 km long arcuate reef tract delineated from known geology. The Unit morphology is partly detectable in the west but is not mappable in the photo area. The occurrence extends from north of Toulon in the southeast to Marseille in the west. It forms the north margin of the regional Beausset synclinal basin (of interbedded sedimentary rocks (Fig. 27). A prominent bare linear ridge of thrust faulting (Fig. 7B) off the northwest corner of the photo area is the Chaine de Baume, a structural continuation of the Pyrenees. Bright green areas are pine and scrub vegetation. Lowlands are cultivated.

Part II The Examples

Figure 22 marlstone (class. Kc2) Characterization Marlstone is an impure argillaceous limestone composed of a weakly-cohesive admixture of fine-grained calcite and clay. The rock erodes into rounded hills in humid temperate regions, and gullied, dissecting slopes in arid and humid tropical regions. Fig. 22A (W044 N41 26), contact scale 1: 33,000, source Courtesy of HTh Verstappen This stereogram depicts sub-horizontal Oligocene marls and sandstone of the Tertiary sedimentary Ebro basin of arid northeast Spain (300 mm annual rainfall). The now stabilized dissected terrain of headward erosion of valley slopes results from climatic fluctuations in the Pleistocene. White stripes in the gullies are terraced cultivation. Fig. 22B (Bands 7-4-2), 11 July 2010, area coverage 2,700 km2 This scene shows marl terrain as gray and white bare intensely dissected uncultivable areas. The undissected beige area to the southeast is mainly pasture land with some grey stripes of shallow dry gullies. Similar marl dissection occurs to the northeast across the intensely cultivated broad alluvial valley of the Ebro River.

Section 2 Sedimentary Rocks

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Group H Saline and Phosphatic Rocks

Group S Detrital Rocks

Figure 23 gypsum (class. H1)

Figure 24 weak arenacious detrital rocks (class. S1.2)

Characterization Gypsum and salt are layered water soluble chemical sedimentary rocks, chlorides and sulphates that result from an aqueous solution that has been concentrated by evaporation. They are from 150 to 7,500 times more soluble than limestone (Martinez et al, 1998). Outcrops of evaporite rocks, other than the diapirs of Fig. 39, are comparatively rare due to their solubility. Modern evaporites generally occur in warm arid climates, they include sabkhas (supratidal areas where evaporation rates are high) that occur in coastal lagoons (Fig. 69) and inland playas (Fig. 56). Geohazard relations As with carbonates, the high solubility of gypsum enables solution channels and sinkholes to develop rapidly resulting in catastrophic collapse of any overlying infrastructures. Fig. 23A (E07 54 N34 22) contact scale 1: 50,000, source Photo Interprétation Éditions ESKA, France This stereomodel shows intensely dissected Eocene gypsum in the crest of a Mid-Cretaceous anticlinal outcrop (Fig. 36). The site is at Tamerza in arid central Tunisia. The Kc2 descriptor identifies relatively more resistant marls on the south limb of the structure. The most resistant rocks are the marginal S1.2 steeply-dipping and eroded interbedded sandstones (Fig. 24). The stream cutting through the marls is described in Fig. 23B. Fig. 23B (Bands 3-2-1), 10 July 2010, area coverage 6,400 km2 This image shows that the small photo area is beyond the apex of the macroscale 35 km broad alluvial fan (Fig. 59) of the Khanga Oued (river) which drains a large basin of bare erodible Cretaceous sediments to the northeast. The Unit is sited between two east-west trending anticlinal folds of a 150 km long range of folds that parallel the margin of the Saharan Platform Boundary Fault. The occurrence is analogous to that of the structure of Fig. 37, 60 km eastward. The breached anticlinal fold east of the fan is Upper Cretaceous limestone exposing dissecting marls of Fig. 22. The larger blue area on the right margin is the phosphate mining and transformation complex of Redeyef. The black spots adjacent to the photo areas are oases plantations.

Characterization These sandstones are rocks of low compressive strength due to generally poor cementation, and have a low density of mineral packing in contrast to the stably cemented parent Unit. Geohazard relations Sheet and gully erosion can provoke rockfalls (Fig. 87) and rock slides (Fig. 92). Headward fluvial erosion on slopes and scarps can cause collapse and threaten any local structures. Fig. 24A (W64 56 S19 05), contact scale 1: 50,000, source Universidad San Andres, Bolivia This stereogram at 3,000 m elevation in the arid Cordillera Oriental of the central Andes is delineated to identify five sedimentary rock Units:  Unit 1 are characteristically dissected weak S1.2 Tertiary conglomerates.  Unit 2 are Devonian limestones.  Unit 3 is a dip slope of Cretaceous limestone.  Unit 4 are alluvium-filled structural intermont depressions.  Unit 5 is a 145 ha rock slide. Broken black lines are possible fault contacts. Fig. 24B (Bands 3-2-1), 08 Aug. 2006, area coverage 730 km2 The image shows the extension of the outcrop of photo Unit 1 northward in a succession of folded (Fig. 36) and faulted (Fig. 43), more resistant Mid Paleozoic and Cretaceous adjacent arenites and carbonates.

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Figure 25 weak arenaceous detrital rocks (class. S1.2) Characterization (see Figure 24) Fig. 25A (E05 56 N43 55), contact scale 1:25,000, source IGN, France The photo pair covers a 750 ha outcrop area of dissected, oak-forested Miocene conglomerates (coarsegrained sandstones) in a humid climate at Oraison, bottom left, in the Pre-Alps of southeastern France. The outcrop ranges in elevation from 440 m to 615 m. Cultivated terraces of the Durance River are at 385 m elevation. They are bordered by a canal, under construction, several meters above the terraces. The white notches in the gullies of the conglomerates are borrow pits for the canal construction which is part of the management of the highly fluctuating Durance River. Fig. 25B (Bands 7-4-2), 22 June 2002, area coverage 500 km2 The image shows the photo area to be in the center of the scene which is divided naturally into three sections by the Durance and the tributary Asse River. (The black line shows water in the functioning canal bypassing the flood-prone valley.)  The northeast section (550–800 m elevation) is characterized by the forested dissected relief of the photo Geounit.  The surface of the southeast section (600 m) is undissected and cultivated portion of the same unit.  The section west of the Durance is lower, 450 m, with moderate relief. All the sections are part of the 1,250 km2 Valensole Tertiary molasse depo basin (sedimentary sequences that were eroded from developing mountain chains). The basin received sediments eroded by rivers from the southern Pre-Alps. The present morphology reflects the subsequent dissection of these weak sediments. The linearity of the Durance is controlled by a major regional fault. The braided channel (Fig. 60) of the river is on the west side of the valley. All green areas are woodlands.

Part II The Examples

Figure 26 argillaceous detrital rocks (class. S2.1) Characterization Argillaceous rocks are compacted laminated-bedded clays, silts or muds. The poor permeabilty of such fine-grained clastics results in minimum rainfall infiltration, and erosion by development of surface runoff closely spaced drainage systems. Geohazard relations Hazards associated with shales are essentially related to their low resistance to mechanical weathering and erosion. Their variable strength is related largely to their water content. They are susceptible to sliding and slumping and generally provide poor subgrade support for structures due to high compaction potential. Fig. 26A (E06 17 N44 47), contact scale 1: 30,000, source IGN, France The stereo model in the French Alps delineates a smooth-appearing six km long ridge of Lower Jurassic (Liassic) shales at elevation 2,600-2,700 m in nonconformable contact (Fig. 48) with Precambrian gneisses. The characteristic surface runoff erosion of the shales contrasts strongly with the fractured terrain of the gneisses. Close examination of the south contact suggested that it may be faulted. Four rock slides (Fig. 92) associated with this contact have been drawn, as well as an earth flow (Fig. 96) within the shales. A debris slide (Fig. 97) and a rock glacier (Fig. 86) are drawn on the north side of the Unit. Fig. 26B (Bands 7-4-2), 22 June 2002, area coverage 570 km2 The shales are barely detectable as a dark brown zone in the upper right of the photo area. The image area is at the southern margin of the 160 km long crystalline Pelvoux massif of the French Alps. The red line marks the contact between the Precambrian massif and Upper Eocene folded and thrusted shaly sediments which are indistinguishable morphologically from the crystalline rocks. This situation is explained by Verstappen in Fig. 97B. Rust colored highlands are above timberline; blue is snow at over 3,000 m elevations. The river in the photo is the upper source of the braided (Fig. 60) Drac River which, via a succession of dams and reservoirs, flows 130 kilometers around the south and west sides of the Pelvoux Massif to join the Isère River at Grenoble 65 linear kilometers to the northwest.

Section 2 Sedimentary Rocks

Group W Interbedded Sequences Figure 27 interbedded sedimentary rocks (class. W1) Characterization These sequences of sedimentary rocks can occur as undisturbed flat-lying or disturbed Geounits:  Flat-lying sequences are strata lying between, or alternating with, others of different lithology, thickness, and resistance to weathering and erosion. They result from disruptions in the depositional process. The resistant strata are in ledge outcrops over or between the recessive (argillaceous) beds. They commonly show banding on aerial photographs. The banding will coincide with the contours of the land surface. Geohazard relations The main geohazard associated with these rock sequences is the risk of landslides (Fig. 92) due to the lack of support of resistant rocks underlain by weak strata.  Disturbed sequences are inclined or folded at various magnitudes of deformation and exhibit the same resistant/recessive outcrops as in flat-lying beds. Figures 35, 36 and 37 of the Geostructures Section show and explain how the identification of dips and strikes of such exposed strata are the basis of mapping deformed Geounits. Fig. 27A (W66 36 S20 57), contact scale 1: 40,000, source Universidad San Andres, Bolivia Four terrain types of disturbed interbedded Mid-Tertiary sedimentary rocks occur in the 48 km2 stereogram. These are arrayed in roughly two kilometer wide segments from southwest to northeast.  Type 1 is beyond stereo coverage but has a generally rough appearing surface of micro relief.  Type 2 has the typical stepped relief of resistant and weak strata.  Type 3 is a sequence of clearly interbedded east dipping strata.  Type 4, beyond stereo cover appears as an evidently fluvially dissected elevated plain. The contact between Types 2 and 3 rock units is marked by a prominent linear 100 m high scarp which is interpreted as a probable fault trace (Fig. 42).

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Fig. 27B (Bands 3-2-1), 20 March 2007, area coverage 1,575 km2 This image does not resolve interbedding but displays the related structures of the photo area. Types 1 and 2 are parts of two obliterating open anticlines (Fig. 36); a smaller brown Unit and a larger grey Unit just beyond the southwest corner of the photo. The area is in the southern sector of the intermontane Altiplano basin of the central Andes. The bright area in the scene center is an extension of Type 3 in the Fig. 27A. Figure 28 Interbedded sedimentary rocks (class. W1) Characterization (see Figure 27) Fig. 28A (W01 09 N42 25), contact scale 1: 30,000, source personal archive This single photo shows flat-lying strongly interbedded, differentially eroded, Lower Tertiary (Oligocene) sandstones and marls in northeast Spain at a general altitude of 900 to 1,000 m. The area is fluvially dissected in narrow valleys with steep slopes. The dark scrub-covered beds are the sandstones. The strata at the northeast edge of the photo are dipping south, the rest of the beds are near- horizontal. The interbedding is most evident in the agricultural west half of the photo. The east half is in oak forests. Fig. 28B (Bands 3-2-1), 06 Aug. 1988, area coverage 290 km2 The image shows the photo area to be at the contact of the northern edge of the Tertiary Ebro Basin (Fig. 22) with the dark folded sedimentary forested ridges of the eastern Pyrenees. The bright dissection of the marls can be seen on the left.

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Figure 29 epicratonic sediments (class. W1.2) Characterization This Variant of interbedded sequences consists of sedimentary rocks of post-Precambrian age that lie nonconformably (Fig. 48) on the surface of an ancient craton or shield. Fig. 29A (W110 45 N62 43), contact scale 1: 70,000, source Courtesy of Natural Resources Canada This photo pair covers 16 km of a five to ten km broad thick sequence of three conformable units of southerly dipping 2,400 to 1,600 Ma, 280 m high interbedded sediments (mainly sandstones and carbonates) in the northeast arm of Great Slave Lake in Canada’s Northwest Territories. One of the units contains hydrocarbons and sedimentary uranium deposits Fig. 29B (Bands 3-2-1), 10 Sept. 1979, area coverage 25,000 km2 The image shows the photo area to be in a structural graben (a depressed block bounded by faults) bordered by Shield cratons, the arcuate Slave craton on the north and Churchill craton on the south. The sedimentary belt is 140 km long. Yellow arrows indicate the Mc Donald Fault Zone of the Churchill craton boundary. This area was deglaciated 9,500 years ago.

Part II The Examples

Section 3 Metamorphic Rocks

Metamorphic rocks are any rocks that have been derived from pre-existing rocks by mineralogical, chemical, and/or structural changes in response to marked changes in temperature, pressure, shearing stress, and chemical environment, generally at depth in the earth’s crust (Dictionary of Geological Terms, AGS). In contrast to intrusive magmas metamorphic rocks are foliated or massive but contain no strong joint systems (Fig. 45). Five Units and eight Variants are ordered in contexts of two Groups:  R – Cratonic Units that occur in a continental area that has been little deformed since Precambrian time (Figs. 30 to 32)  J – Non-cratonic Units that occur in orogenic (mountain chains) belts, around the boundaries of intrusive igneous rocks, and in other tectonic terrains (Figs. 33, 34).

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Interpretations of Metamorphic Rocks Group R Cratonic Rocks Figure 30 cratonic foliated rocks (class. R1) Characterization These Units are belts of orogenically metamorphosed sedimentary or volcanic rocks that show compositional banding or planar structures (e.g. gneiss, schist, migmatite, phyllite). The laminated structure results from the flattening of the constituent grains of a rock. There are no strong joint systems. In areas of metasediments airphotos indicate bedding rather than foliation. Fig. 30A (E04 21 N24 56), contact scale 1: 50,000, source IGN, France This stereo pair shows the characteristic banding of flexural flow (folding parallel to surfaces of foliation) of a 10 km wide section of strongly foliated Proterozoic schists of the Hoggar craton of southern Algeria. Delineation on the stereo mate included in the extra material on the Springer website of this pair identifies four structurally-associated Geounits: Unit 1 are the foliated schists; Unit 2 are unfoliated younger weaker sedimentary rocks (these appear as a light grey band in the northwest of the printed photo); Unit 3 are foliated gneisses; Unit 4 are weakly foliated possible migmatites (rocks that are transitional between granites and crystalline schists). The band of coarser-grained gneisses of Unit 3 has definite but imperfect foliation compared to the schists. Fig. 30B (Bands 3-2-1), 17 July 2010, area coverage 1,890 km2 The image shows the photo pair to be at the north end of the zone of coalesced bright stocks in Fig. 5B and in the morphotectonic fold belt described in Fig. 51B. The four photo units are also distinguishable in the image.

Part II The Examples

Figure 31 massive cratonic rocks (class. R2) Characterization Rock Units of low level metamorphism such as quartzite, hornfels or marble, are composed of randomly oriented minerals that give the unit a lack of banding, i.e. massive appearance. Fig. 31A (E01 48 N11 03 57), contact scale 1: 50,000, source IGN, France The stereo pair is located in northwest Benin. The morphologic and tonality contrasts distinguish three classes of Lower Precambrian metamorphic rocks. R1 foliated gneiss, R1 unfoliated schist, and R2 non-foliated quartzites. Fig. 31B (Bands 3-2-1), 14 Jan. 2007, area coverage 750 km2 The image shows the bright R2 massive quartzites of the photo area to be near the well-displayed north end of the 600 km long Atacora morphotectonic fold belt. The dark schist area is in an upland trough about 100 m lower in the center of the belt which is at about 400 m elevation here. The relatively featureless area in the northwest quadrant is part of the Volta Basin of interbedded (Fig. 27) sandstones and shales which cover the greater part of Ghana. A prominent strike-slip fault (Fig. 44) crosses the folds just north of the photo area.

Section 3 Metamorphic Rocks

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Figure 32 glaciated cratonic foliated rocks (class. R1.1)

Group J Non-Cratonic Rocks

Characterization Areas of foliated rock belts that have been scoured of overlying deposits by moderate to heavy areal glacial erosion are as exposed as in arid environments. Minor structural features may stand out in relief.

Figure 33 non-cratonic massive rocks (class. J2)

Fig. 32A (W63 39 N57 16), contact scale 1: 100,000, source Courtesy of Natural Resources Canada The small scale stereo photo pair covers 660 km2 of terrain in north Labrador. The western half of the area is in gneisses and migmatites (Fig. 30) of Archean orogens. The terrain on the east is later Mid Proterozoic plutonic granites (Figs. 2, 3), marked Np3.1. The characteristic relief of the Units is visible monoscopically in this region. The only occurrences of surficial deposits detected in the stereo model are a small 15 km2 zone of shallow, eroded glacial till labeled Gf3.3 (Fig. 82), and a three km long esker ridge (lenses of irregularly stratified sand and gravel deposited by englacial or subglacial streams) located by red arrows. Fig. 32B (Bands 4-3-2), 17 April 2007, area coverage 10,000 km2 The image covers an area of essentially bare bedrock terrain deglaciated 10,000 years ago. The western half of the scene clearly displays the contrasting foliated metamorphic rocks of the photo area and the granite terrain on the east. A stock-like (Fig. 2) occurrence of granitic rock, with its characteristic joint sets, is visible in the lower left corner of the scene. The northeast corner of the scene touches Fig. 82 B.

Characterization With the exception of their tectonic setting the rocks of this Unit are similar to Fig. 31. Fig. 33A (E09 19 N42 08), contact scale 1: 25,000, source IGN, France The 1982 photo pair express strongly dissected Cretaceous schists with narrow ridges and deep gorges covered by (maquis) scrub in eastern Corsica. Relief range is from 300 to 650 m. The cleared areas are rough pastures. Fig. 33B (Bands 3-2-1), 16 Sept. 2003, area coverage 990 km2 This image shows the rugged wooded regional schist zone (Fig. 30) of the photos and the 10 km wide agriculturally developed Miocene-Pliocene coastal plain (Fig. 78). The arcuate white line in the center of the photo area is a fire break cut along a ridge line.

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Figure 34 peneplaned foliated rocks (class. J1.1) Characterization Peneplaned rock units are the result of subaerial degradation by erosion and mass wasting during extended geologic periods of tectonic stability. The surfaces cut across, and are essentially devoid of control by, underlying metamorphic structures. Fig. 34A (W04 42 N48 03), contact scale 1: 25,000, source IGN, France The stereo model shows the 60 m high, fracture-edged (Fig. 66) cliff bordering the Pointe du Van peninsula on the coast of western Brittany. This is an uplifted Eocene peneplane surface cut across Cambrian gneisses. A thin cover of surficial deposits conceals the bedrock (see Berger quote in discussion of Geostructures). The beach is in a bay at the mouth of a depression of weak Carboniferous schists. The intense local land use pattern is characterized by the French bocage system of field enclosure by thick hedgerows. Fig. 34B (Bands 3-2-1), 08 July 1987, area coverage 500 km2 This faintly veiled image covers 15 km of the 25 km long le Cap westernmost peninsula in France. The peninsula is composed of the gneisses of the photo area on the north and Ordovician granites of pointe du Raz on the south. The two areas are separated by the dark linear band of a two kilometer wide regional fault-associated depression eroded in Carboniferous schists and occupied by dense, hedged, horticultural land use. The general rectilinear shape of the peninsula is controlled by faults on both north and south coasts.

Part II The Examples

Section 4 Geostructures

Geostructures are bedrock Geounits that have been deformed or displaced by folding, faulting, or igneous intrusion processes. ‘‘The ability to recognize and map geological structures from remote sensing data is dependent primarily on two main factors: the level of bedrock exposure of the mapped structures and their magnitude of deformation.’’ Z. Berger 1994. 18 Units and 16 Variants are ordered in four Groups:  Diastrophic Rock Units: are the result of all movements of the crust produced by tectonic processes (Figs. 35 to 38).  Gravity Structures: are the result of gravitational forces of dense rocks causing underlying low density rocks to rise (Figs. 39 to 41).  Fault Line Traces: are strong linear features in consolidated rocks or coherent surficial material visible in airphotos or imageries possibly or probably resulting from movement reflecting tensional stress. Figures 42, 43, and 44 are examples of known faults.  General Lineaments: may be straight or irregular. They include linear arrangements of natural geomorphic or radiometric features marking fracture traces (Fig. 45) and interpreter-drawn mapping lines that mark the natural boundary lineaments of unconformable rock types (Figs. 46 to 49).

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Interpretation of Geostructures Group Diastrophic Rock Units Figure 35 homoclinal structures (class. 2.2) Characterization These Variants consist of a structural condition in which stratified rocks dip uniformly in one direction. They are classed as low, 25º. Photogeologically the stereo expression of dipping rocks is exaggerated. This property is helpful in structural interpretation but caution must be exercised because of the exaggeration. For example the moderately dipping beds in Fig. 35A with a true dip of 15° appear to be as much as 45° in the stereo model, i.e. a three times exaggeration. Fig. 35A (W66 56 S18 25) contact scale 1: 40,000, source Universidad San Andres, Bolivia The stereogram in arid western Bolivia shows a 7 km segment of a ridge of clearly interbedded sedimentary rocks (Fig. 27) with a dip symbol indicating moderate dipping to the east. The ridge crest is at elevation. 4,400 m, the footslope fans (U) are at elevation 3,700 m. The small town of Poopo is on a fan at the mouth of a creek at the north end of the Unit. The line at M indicates a possible thrust fault (Fig. 7B) Fig. 35B (Bands 3-2-1), 17 April 2009, area coverage 5,800 km2 The image shows the ridges of the photo area to be the western ranges of the folded and thrusted Paleozoic and Mesozoic sedimentary rocks of the Cordillera Oriental. The 35 km long red delineated zone contains a number of morphologically anomalous Units that are associated with the economically important belt of polymetallic vein deposits of southwest Bolivia. Two mines large enough to resolve in the 30 m image are circled. The northern mine, a tin producer, is at Morococala; the southern mine, another tin producer is at Catavi. They are both located in relatively undeformed rocks. The deposits are intimately related to intrusive rocks in a variety of host rocks. The white alluvial fans and playas are prograding into the Desaguadero River tributary of the closed

Part II The Examples

drainage salt water Lake Poopo in the southwest of the scene. The stream gorge and fan at Poopo settlement at the north edge of the photo model shows the ridge offset of a strike-slip fault (Fig. 44) along the Poopo creek. Another possible strike-slip fault is a 25 km long bright stream course oriented obliquely to the local ridges at the north end of the scene where it empties into a fan-delta (Fig. 58). The beige land on the left of the river is part of the Altiplano. Figure 36 fold structures (class. 5) Characterization This Unit consists of deformed systems that are sets of congruent anticlinal and synclinal folds in bedded rocks that are produced by a same tectonic episode (Fig. 36A). Fig. 36A (E03 03 N25 48), contact scale 1: 83,000, source IGN, France This stereo pair of airphotos covers 500 km2 (26 km by 19 km) in the central Sahara of southern Algeria. The model shows an erosional section through elongate parallel gentle open folds in Mid Paleozoic shales and sandstones that illustrate the geometric properties of the two basic types of folds. The axial hinge line of the folds has been drawn with indication of the direction of the limbs:  outward from the hinge for the arched up strata of the four kilometer wide left fold, an anticline, (author’s Variant class. 5.1). In photogeologic parlance the structure is in an obliterating stage of erosion, i.e. erosional processes have eliminated most of the structural relief.  inward toward the hinge for the limbs of the depressed strata of the five kilometer wide fold on the right, a syncline, (author’s Variant class. 5.2). This structure is in a breached erosion stage, i.e. the limbs of the structure are still preserved. Some minor features are superimposed on the structures; a 10 km long streak of complex dunes (Fig. 54) crosses the south end of the syncline and a two kilometer long strike slip fault (Fig. 44) displaces part of its north end. A six kilometer stretch of a superimposed wadi cuts through both limbs (small arrows) and crosses the center of the anticline.

Section 4 Geostructures

Fig. 36B (Bands 3-2-1), 09 Aug. 2010, area coverage 6,400 km2 The left grey, beige part of this image at elevation 330 m covers the eastern part of the Ahnet intracratonic basin. Fold structures in the basin are the result of gentle Upper Paleozoic compressional deformation. Figure 44 which is 115 km to the southwest shows a synclinal structure at the south margin of the same Basin. The bright beige area in the south is the Erg Mehedjibat, a 500 km2 field of 200 to 250 m high star dunes (develop by interaction of winds from multiple directions) of the Section 5 Aeolian Subgroup Sand Dunes. The dark rocks on the east are discussed in Fig. 43B. They are regionally faulted Lower Paleozoic sedimentary rocks at elevations of 700 to 1,000 m. The light grey area in the southeast corner is possibly downfaulted low-weathered schistose rocks at elevation 500 m of the Hoggar cratonic massif. Figure 37 single anticline (class. 5.1) Characterization An anticline is a unique fold structure that is convex upward, whose core contains the stratigraphically older rocks explained in Fig. 36A. Fig. 37A (E08 26 N34 20), contact scale 1: 50,000, source IGN, France This stereo photo is in the same tectonic suite as Fig. 23, 60 km westward in central Tunisia. The photo taken on 20 October 1952 covers the western 7 km of a 20 km long two km broad anticline in Upper Cretaceous marly limestones. The structure is in a breached stage of erosion where the crest has been completely removed but the limbs are preserved. The terrain to the north is strongly dissected Lower Tertiary phosphate rocks (Fig. 23). Fig. 37B (Bands 3-2-1), 10 July 2010, area coverage 1,400 km2 This image shows the photo anticline to be at the south border of extensive, mined (white and blue) phosphate deposits. The folds in the scene are part of a 150 km long fold range of Cretaceous sedimentary rocks at the south margin of the Tunisian Atlas. The town of Mitlawi, sited on a dark bajada fan (Fig. 59) at the western tip of the photo fold structure, is the administrative center of the mining complex. The occurrence is analogous to that of Fig. 23 which is 60 km westward.

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The terrain in the north and south of the image consists of low weak Upper Tertiary sandstones (Fig. 24). The white pit mine at the north edge of the photo area had not been developed at the time of the airphoto, 58 years earlier. Figure 38 isoclinal folds (class. 5.4) Characterization This Variant of Fig. 36 is a succession of tight, pronounced anticlinal and synclinal folds with limbs that have parallel dips formed under conditions of intense lateral compression. Fig. 38A (E03 01 N43 26), contact scale 1: 30,000, source IGN, France This delineated photo pair, 30 km inland from the Mediterranean coast, is in the Sub-Pyrenean zone of southern France, 60 km north of the main chain. The descriptor code numbers indicate four broad zones of lithology and structure:  Zone 1 on the southeast is a six km long three km wide succession of wooded 100 m high ridges of Lower Jurassic limestones at 200 m elevation that were deformed in Upper Eocene.  Zone 2 are cultivated intermont depressions of marl strata (Fig. 22).  Zone 3, in the northwest, are Ordovician sedimentary rocks, part of the Montagne Noire southernmost projection of the crystalline Central Massif.  Zone 4 is a lowland of Eocene to Holocene sediments in the valley of the Orb River at the town of Cessenon (arrow) 60 to 100 m elevation. Fig. 38B (Bands 7-4-2), 13 Aug. 2001, area coverage 390 km2 The image clearly shows a structure not evident in the photo areas. They are in isoclinally folded Jurassic strata of a well-defined 140 km2 thrust block. The structural Unit is distinguished by an arcuate linear pattern of green forested limestone ridges and brown marl depressions. The black zones adjacent to the meander (Fig. 63) Orb river on the right are abandoned and flooded borrow pits of the river gravels. The forested mass to the northwest is part of the Montagne Noire. The area to the southeast is part of the Mediterranean coast plain just west of Béziers.

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Group Gravity Structures Figure 39 evaporite diapirs (class. 11) Characterization These diapirs occur in saline and phosphatic rocks (Fig. 23). They are a distortion into cylindrical stocks of tabular saline source basins at depth that have accumulated throughout Phanerozoic time. They are driven upward by buoyant forces due to the contrast in density between the salines and the overlying strata. At outcrop the diapirs have a generally circular shape, range from nil to 500 m in height and from one to 10 km and more in diameter. Geohazard relations Saline and phosphatic rocks are weak and subject to dissolution and collapse. Anhydrite will readily combine with water to form gypsum, and in so doing will expand rapidly in volume, in some cases over 50%. Fig. 39A (E01 52 N33 39), contact scale 1: 20,000, source Photo Interprétation Éditions ESKA, France This stereomodel shows the Kef el Melah diapir of Upper Triassic salt and gypsum in northwest Algeria. The descriptor 11.1 denotes the relatively less soluble caprock. The diapir is 1,800 by 1,100 m in diameter. Ridges of uplifted and steeply dipping sediments disturbed by the diapir border its southern rim. The outcropping of this soluble material is due to its location in a dry climate where hardly any dissolving takes place. Fig. 39B (Bands 3-2-1), 06 July 2010, area coverage 400 km2 The bright blue diapir is seen in this image to lie off the west flank of a dark breached anticlinal fold (Fig. 36) in the Djebel Amour ridge of the Saharan Atlas Range. The range is a low Alpine orogenic chain that stretches 1,000 km from the Moroccan border to Tunisia. The beige terrain to the northwest is part of a post-tectonic sedimentary basin, the High Plateaux, between the Late Eocene and Saharan Atlas orogens. The river is an unnamed meander (Fig. 63) stream which dies out to the southeast in the sands and gravels of the Cretaceous/Tertiary North Sahara sedimentary Basin.

Part II The Examples

Figure 40 duplex stocks (class. 11.2) Characterization This Variant of Fig. 39 consists of stocks that are a composite of two source layers. The primary diapir material forms the core of the structure. Peripheral rings are composed of younger overlying deposits which have been dragged up during diapir formation. The combined materials upwell, mushroom out and overhang as infolded lobes. Fig. 40A (E53 45 N34 57), contact scale 1: 30,000, source Geological Society of America Memoir 177, Fig. 1.42, p 47 This single airphoto of a 7 km diameter Eocene 45 Ma diapir shows the mottled salt outcrop surrounded by finely banded cycles of younger salt and gypsum. The intruded ground is part of the strongly banded truncated (removal of a part of a Geounit by erosion) surface of folded Miocene 15 Ma saline mudstones and gyprock sediments of an extensive regional playa in northern Iran. Small normal faults are at a; b is an anticline; c is a syncline. Fig. 40B (Bands 3-2-1), 19 Oct. 2010, area coverage 2,240 km2 This image shows the diapir to be one of 22 in the image area, 10 of which, to the left, have coalesced laterally to form a single continuous salt canopy. The group is in the center of a concentration of 50 diapirs that occur in a 140 km wide diapir province in the northern part of the 50,000 km2 Great Kavir evaporite basin, Iran’s largest playa. The thicknesses of these structures vary from 600 to 2,000 m. The white zones are playa sediments. As mentioned in Fig. 40A the entire area of the scene is a level erosion surface that truncates the strong banding pattern of 15 Ma folded mudstones with interbeds of rock salt. Figure 41 elongate diapirs (class. 11.4) Characterization The form of these Variants is the result of anticlinal, synclinal (Fig. 36), and normal fault (Fig. 42) structures by which they are controlled.

Section 4 Geostructures

Fig. 41A (W67 08 S19 26), contact scale 1: 40,000, source Universidad San Andres, Bolivia This stereogram shows an elongated 2,300 m long, 900 m wide Mid-Tertiary gypsum diapir elongated by its location along the strike of a belt of isoclinally folded (Fig. 38) Cretaceous sediments in southwest Bolivia. The Unit denoted a is the rust colored Unit in Fig. 41B. F descriptors indicate strike-slip faults (Fig. 44). Fig. 41B (Bands 7-4-2), 08 July 2001, area coverage 480 km2 This image shows the diapir to be sited at the locus of a strike-slip fault and other post-orogenic diastrophic activity in a belt of isoclinal folds (Fig. 38) near the east margin of the Altiplano. The belt is the northern termination of a 70 km long range of Cretaceous sediments folded in Pliocene by west-thrusting (Fig. 7B) ranges of the Cordillera Oriental 20 km eastward. The beige members may be sandstones. The fan shaped unit on the west flank of the folds is a Pliocene alluvial fan (Fig. 59). The Recent age fans east of the folds are entrenched (partly dissected). The flat area in the east of the image is an Altiplano surface. Green areas are irrigation in stream valleys.

Group Fault Line Traces Geohazard relations of Figs. 42, 43, 44. Hazards associated with faults are related to their activity status, their occurrence near or in seismic and volcanic zones, and their groundwater conditions. Faults determined active are liable to recurrent movement. Figure 42 dip-slip faults (class. 12) Characterization These faults are also termed normal faults in that the movement is parallel to the near-vertical dip of the fault plane, typically 45º to 90º.

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Fig. 42A (W68 36 S16 02), contact scale 1: 50,000, source Universidad San Andres, Bolivia The stereogram shows 5 km of a normal fault cutting Quaternary lateral glacial moraines (Fig. 4A) at 4,100 m elevation. Prominent moraines of a one km wide glacial valley are in the north (left) of the model. Fig. 42B (Bands 7-4-2), 25 May 2000, area coverage 1,050 km2 The photo fault is visible in the glaciated foothills of the Cordillera Oriental. A second, red traced, parallel fault is visible near the stream 5 km to southwest. These structures are part of the Lake Titica structural depression and are related to the tectonic movements mentioned in Fig. 41B. The image covers part of the eastern boundary of the Altiplano (Fig. 41), the snow and ice capped Andean peaks rise to 5,500 m. The glacial moraines cut by the fault are at the lowest elevation reached by the browncolored glacial and fluvioglacial deposition in the region (Fig. 83). Green land is cultivation in the lake depression and mountain gullies, with some brighter sylvicultural development westward. Figure 43 Dip-Slip Faults (class. 12) Characterization (see Figure 42) Fig 43A (E03 16 N25 57), contact scale 1: 85,000, source IGN, France This group of three parallel normal faults are in S2 denoted Ordovician sandstones and S1 Silurian shales in southeastern Algeria. The faults have been superposed on ancient faults. The dendritic pattern of incised drainage channels on the shales is indicative of one of a series of pluvial periods that prevailed in this part of the Sahara during the Tertiary and Quaternary periods. The R3 unit is part of the basement rock. Fu1 are bajada fans (Fig. 59). The west-dipping homoclinal ridge one kilometer west of the fault set is Mid-Paleozoic shales marking the eastern edge of the Ahnet Plateau of Fig. 36B.

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Fig. 43B (Bands 3-2-1), 09 Aug. 2010, area coverage 11,875 km2 The image shows that the faults of the photo area, and others pointed to on the right, are related to the PanAfrican orogenic cycle of Fig. 51B, 50 km to the south. The faults are in the northwest segment of the Ordovician Tassili Plateaux that surround the Hoggar Craton on the north and east. The west half of the scene is part of the Ahnet Basin of Fig. 36B at elevation 330 m. The yellow area is the field of star dunes described in Fig. 36B. The grey area in the southeast is craton basement Proterozoic schists at elevation 500 m. Figure 44 strike-slip faults (class. 13) Characterization In contrast to dip-slip faults Strike-slip faults have a horizontal displacement of blocks. They do not cause scarping and rocks do not match across the fault, they are offset. Fig. 44A (E01 59 N25 28), contact scale 1: 50,000, source IGN, France The stereomodel in central Algeria has a drawn set of strike-slip faults displacing interbedded (Fig. 27) Devonian sediments of a synclinal structure (Fig. 36) whose axial hinge is drawn. The dark dissected rocks are shales, the bright rocks are sandstones. Fig. 44B (Bands 3-2-1), 29 June 2010, area coverage 1,575 km2 The image shows the synclinal structure to be a deformation similar to the other folded rocks of the Ahnet basin in Fig. 36B, 115 km to the northeast. As in the photo model the dark beds are shales and the light grey and white strata are sandstones; beige ground is alluvium.

Part II The Examples

Group General Lineaments Figure 45 mesoscale fracture traces (class. 18) Characterization Fracture traces are natural linear features expressed as alignments of drainage, vegetation, or spectral tonality and color. Brittle rocks deform by fracturing in release of stored stress or cooling contraction in igneous bodies. The term joint is used where fault displacement evidence is lacking. In geologic mapping fractures are distinguished as sets of parallel fractures and systems of intersecting fractures. The traces can be further classified by their orientations, their lengths, and their densities. (A high density is greater than 24 linear km per km2). Geohazard relations Surface patterns of joints are a reliable indication of pattern at depth. They affect the strength and stability of the rock mass, and the voids associated with their presence allow increased circulation of groundwater through them. This may be crucial in drainage of a deep excavation or in leakage through the sides or floor of a reservoir. Fig. 45A (W58 33 N51 17), contact scale 1:10,000, source personal archive This large scale photo triplet covers 920 hectares. It displays conjugate sets (related in deformational origin) of fracture traces in rugged denuded granitic terrain that has been scoured by glacial erosion and deglaciated 11,500 years ago. The fractures appear to be tension joints which control the drainage and contain the only vegetation in the area. The 500 m to 1 km wide lake-filled major joints could be local faults, a determination that can only be established in the field. Fig. 45B (Bands 7-4-2), 20 Sept. 2001, area coverage 475 km2 Fracture traces larger than those of the photo model dominate this image in Mid Proterozoic gneisses and granites of the Grenville Orogen of the Canadian Shield on the lower Gulf of St Lawrence in eastern Quebec, Canada. The braided river (Fig. 60) on the left is the St Augustin and the red arrows in the southwest corner of the scene point to the village and airstrip of the same name.

Section 4 Geostructures

Mollard 1983, p 21 commented about similar Grenville terrain 460 km to the southwest that “Even though glaciers have overridden and eroded these rocks in the past, frost shattering along the joints in postglacial time has produced a very sharp and extremely rough surface”. Figure 46 stratigraphic unconformable geolineament (class. 21.1) Characterization An unconformable geolineament is the interpreted drawn line that marks the boundary in a sequence of strata separating younger from older rocks that are not in normal succession, due to an intervening period of erosion or non-deposition. Fig. 46A (W110 37 N38 39), contact scale 1:20,000, source USGS The stereogram shows low dipping grey strata of 700 Ma (million years ago) Mid-Jurassic shales at A flanking strongly parallel-jointed more massive beds of 900 Ma Lower Jurassic sandstones at B. C is an occurrence of dissected weak sediments. D is a veneer of windblown sand. Fig. 46B (Bands 3-2-1), 30 Sept. 2010, area coverage 2,560 km2 Geolineament contacts have been drawn on this image between nine photogeologic Units. The center of the area covered is the south half of the 120 by 65 km San Raphael Swell , a broad asymmetric dome of the Colorado Plateau in central Utah. The structure was uplifted in Late Cretaceous and Lower Paleogene (Laramide Orogeny), and stands at 2,000 m elevation 500 m above surrounding terrain. Units 2 and 3 were exposed by the uplift. The San Rafael Swell is one of eight similar uplifts that occur on the Colorado Plateau.  Unit 1 are bright Lower Jurassic sandstones of the photo area with dips of 10º to 60° over Units 2 and 3 on the southeast limb of the swell.  Unit 2 are the large light grey and beige 210 Ma Triassic red beds (an undivided formation of interbedded strata) in the center of the structure.  Unit 3 is grey 260 Ma Permian limestone.  Unit 4 is dark brown Lower Jurassic sandstone and siltstone.  Unit 5 is an extensive occurrence of bright Lower Jurassic limestone on the west flank of the swell.

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 Unit 6 is beige Lower Jurassic sandstone.  Unit 7 is the narrow brown band of Mid Jurassic shale and sandstone of the photo area lying on the sandstones of Unit 1.  Unit 8 is a group of recent volcanic vents.  Unit 9 is an undivided formation of Upper Jurassic interbedded strata. The ground in the southeast corner is covered by linear dunes (Fig. 53). The ground in the light brown southeast corner is covered by linear dunes. Figure 47 angular unconformable geolineament (class. 21.2) Characterization An angular unconformable geolineament marks a drawn boundary in which younger sediments rest upon the eroded surface of deformed older rocks. Fig. 47A (W01 06 N41 02), contact scale 1: 30,000, source personal archive This stereo triplet photo model in northeast Spain includes seven numbered Units of Paleozoic and Mesozoic folded sedimentary rocks with two unconformable contacts. The first unconformity is between the Devonian schists and quartzites of Unit 2 and the high ridge of Mid-Triassic limestones of Unit 3 that are folded into several small structures – a time gap of 150 Ma. A second unconformity occurs between the Upper Triassic marls of Unit 4 and the Upper Cretaceous marls of Unit 5 a 125 Ma time gap. Both of these Units are cultivated, but with distinct field patterns. Unit 6 is a homoclinal southwest-dipping ridge (Fig. 35) of Upper Cretaceous resistant limestone. Units 1 and 7 at respective corners of the model are areas of Lower Tertiary sandstones. Local faults are traced in red. Fig. 47B (Bands 3-2-1), 24 July 1999, area coverage 1,050 km2 This image in northeast Spain shows the photo area to be in the folded ranges of the Iberian Mountains. The mountains are on the east margin of the central Hercynian (Upper Paleozoic) Meseta at the south edge of the bright Ebro Basin in the northeast part of the scene. They were reactivated by Alpine orogenic movements of the Pyrenees to the north.

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The pale-blue-colored limestone of photo Unit 6 is particularly distinctive between the cultivated bands of Units 5 and 7. The black area to the south is a zone of reforestation. Figure 48 nonconformity (class. 21.3) Characterization A nonconformity is a drawn boundary between stratified rocks and unstratified igneous or metamorphic rocks. Fig. 48A (E03 34 N44 12), contact scale 1: 75,000, source IGN, France This 17 km by 29 km stereo triplet model in central France illustrates nonconformable contacts that have been drawn between bare droughty Jurassic carbonates of a plateau, and largely forested Lower Carboniferous metamorphic rocks at 700 m general elevation Unit J2, Section 3). The carbonates comprise a sequence of four facies. Facies F1 is Upper Jurassic karst limestone with a characteristic surface pitted with small solutional dolines (Fig. 91). Facies 2 is Mid Jurassic. Outlier Facies 3 is Lower Jurassic. Facies 4 is argillaceous Lower Jurassic limestone. Fig. 48B (Bands 3-2-1), 27 Aug. 2003, area coverage 6,300 km2 The image in south central France shows the same morphologic and spectral contrasts between the two principal lithotectonic suites of the photo model. The bare, regional extent 150-190 Ma, plateau area, locally named causse (in this case Méjean), ranges from 800 to 1,200 m elevation. Its eastern margin was fault uplifted in the Tertiary. Black areas on its surface are reforestation. The grey, wooded, metamorphic terrain on the east is part of the 345 Ma, 900 to 300 m elevation Cévennes metamorphic massif (Fig. 33). Figure 49 nonconformity (class. 21.3) Characterization (see Figure 48) Fig. 49A (W63 07 N58 42), contact scale 1: 40,000, source Courtesy of National Resources Canada This stereo triplet photo model covers an area of 135 km2 on the Labrador coast of eastern Canada.

Part II The Examples

The drawn nonconformity contact in the model is between interbedded Paleo Proterozoic sedimentary and metamorphic rocks 2,100-1,800 Ma A at 750 m elevation, and massive, fractured and faulted 3,1002,500 Ma Archaean plutonic (Fig. 3) basement rocks B at elevation 370 m. The faulted area on the west is in Early Proterozoic sediments at elevation 400 m. Other local jointing or faulting (Fig. 45) is indicated in red. Fig. 49B (Bands 7-4-2), 09 Sept. 1999, area coverage 1,920 km2 This image at Bear’s Gut on the coast of the southern end of the Torngat Mountains shows some of the morphologic relief of the photo rock types. The area is 80 km north of Fig. 82. The jointing or faulting photo fracture traces are not resolved. The regional morphology is alpine type glaciation of cirques (rounded steep walled basins in the higher parts of mountains) and U-shaped valleys that were deglaciated 11,000 years ago. Blue peaks and ridges to the south and west, at 1,000 and 1,200 m elevations are snow-covered. The green areas in the sheltered valleys are alder and willow shrubs.

Section 5 Aeolian Deposits and Erosion Forms

Aeolian deposits consist of particles in the range of diameters of 0.02 to 2.00 mm. They have been transported by wind in suspension or traction from regions of sparse vegetation and a large supply of unconsolidated sediments. Aeolian sand deposits, excluding coastal dune systems, cover approximately 5% of the global land area of which 97% occur in large arid zone sand seas (dune fields of regional extent). An additional 10% is covered by silt loess (Fig. 50). 19 Units and 10 Variants are ordered in six Subgroups:  Et – Inland deposits: are unconsolidated, unstratified silt sediments (Fig. 50) that occur in the continental heartlands of North and South America, Europe, and Asia.  Ef – Duneless deposits: these consist of coarse sand which is not readily formed into dunes (Fig. 51).  Er – Erosion forms: are wind-sculpted Units in homogeneous materials (Fig. 52).  Ed – Sand dunes: are mounds, ridges or hills aerodynamically shaped by aeolian processes (Figs. 53, 54).  Eo – Obstacle dunes: these form where sand-laden wind encounters a topographic barrier.  Ec – Coastal dunes: are dunes that occur above high-water marks of sandy beaches.

L.A. Rivard, Satellite Geology and Photogeomorphology DOI 10.1007/978-3-642-20608-5_6, © Springer-Verlag Berlin Heidelberg 2011

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Part II The Examples

Section 5 Aeolian Deposits and Erosion Forms

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Fig. 51A

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Section 5 Aeolian Deposits and Erosion Forms

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Fig. 52A

Part II The Examples

Section 5 Aeolian Deposits and Erosion Forms

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Section 5 Aeolian Deposits and Erosion Forms

Fig. 53B

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Fig. 54A

Part II The Examples

Section 5 Aeolian Deposits and Erosion Forms

Fig. 54B

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Interpretations of Aeolion Deposits and Erosion Forms Subgroup Et Inland Deposits Figure 50 blanket loess (class. Et1.1) Characterization Loess is a calcareous windblown silt and clay with a modal grain size in the range 0.02–0.5 mm. Deposits have a pronounced vertical structure and range in thickness from a few centimeters to more than 200 m. The thickest deposit is 335 m on the Loess Plateau of China. The blanket Variant is a deposit thick enough to mask underlying materials. Deposits decrease in thickness and increase in fineness and cohesion (clay content) with distance from their source. The material can maintain a vertical face due to a vertical cleavage resulting from tension cracks and incorporated plant roots. Deposits are porous and vertically well drained. Loess has a distinct drainage pattern of dendritic networks of vertical-sided U-shaped gullies. Loess in the central Great Plains of the United States was derived from unglaciated terrains of Tertiary siltstones northwest of the main deposits. It is one of the most extensive surficial deposits in midcontinental North America.

Part II The Examples

Fig. 50 B (Bands 3-2-1), 15 Oct. 2010, area coverage 1,750 km2 The photo model area is seen to be at the west end of a mass of loess deposits that extend between the agricultural valleys of the North and Middle Loup Rivers. The U-shaped gullies are visible. Dark brown areas are wooded gullies. The morphologically distinct area in the north of the scene is part of the south margin of the linear dunes of 50,760 km2 Nebraska Sandhills.

Subgroup Ef Duneless Deposits Figure 51 sand sheets (class. Ef1) Characterization Sand sheets exist where grain sizes are too large or wind velocities too low for dunes to form. They are accumulations of essentially flat laminae, forming deposits with little or no topographic expression. Thicknesses are difficult to judge from airphotos or Landsat images but range from a few centimetres to a few meters. Geohazard relations Sand sheets encroach on vehicular roadways and agricultural land. Zones of persistent encroachment of roads require constant clearing activities. Abrasion can undercut structures close to ground level.

Geohazard relations Loess is susceptible to erosion by wind and water. Headward dissection develops from the drainage of infiltrated water at the footslopes. Addition of water generally destroys the internal structure and the material will collapse on saturation. External loading such as imposed by earthquakes also causes loss of strength of loess during the period of vibration.

Fig. 51A (E04 44 N23 19), contact scale 1: 50,000, source IGN, France This single photo composite covers the north half of an 8 km diameter granite plain (Fig. 5) in Algeria with a sand sheet thinly covering the disintegrated rock. The plain is the core of a Proterozoic stock-size (Fig. 2) intrusion into older granites. The stock is surrounded by a 180 m high resistant outer rim.

Fig. 50A (W 99 21 N41 44), contact scale 1: 67,000, source USGS This stereogram covers a 100 km2 area at elevation 770 m in central Nebraska in the High Plains of the central United States. The extensively dissected Upper Pleistocene, 25,000-13,000 BP, loess has 50 m relief and ranges in thickness from two to 25 m. Individual gullies are characteristically U-shaped. The limited area north of the cultivated river valley is covered by linear dunes (Fig. 53).

Fig. 51B (Bands 3-2-1), 26 July 2010, area coverage 3,900 km2 This image shows the sand sheet and granite stock to be in a tectonic belt that formed in the western Hoggar Massif of Fig. 3. The belt is a 600 km long north-south striking complex at a 1,000 m average elevation. Other white areas in the scene are sand sheet-covered granites and metamorphic rocks of different composition. This area is 100 km south of Fig. 5B.

Section 5 Aeolian Deposits and Erosion Forms

149

Subgroup Er Erosion Forms

Subgroup Ed Sand Dunes

Figure 52 erosion forms (class. Er1)

General characterization The principal sources of dune sands are from desert alluvial fans (Fig. 59), dry river valleys, playa basins (Fig. 56), and weathered desert sandstones (Fig. 43). Dunes have a wide range of forms and sizes, from a few centimeters to several kilometers and heights exceeding 250 m. They are transported close to the ground by traction and saltation (short leaps and bounces on the ground) and accumulate by deposition in sites of reduced wind velocity. They occur as eight Variants. Linear dunes and dune complexes are figured here. Three other common Variants are:

Characterization Wind-sculpted Units in fairly homogeneous materials that produce long narrow ridges 20 to 50 m high sited between two troughs are termed yardangs. They can be several kilometers in length and are three or four time longer than they are wide. (Breed, C.S. et al, 1989). Fig. 52A (E17 42 N18 42), contact scale 1: 50,000, source IGN, France This single airphoto in northern Chad shows dark yardangs oriented westward across a plateau of Lower Paleozoic sandstones at 450 m elevation. The yardangs result from deflection of winds well-armed with sand, from Libya to the northeast which blow strongly southwest and westward for eight months of the year in a 200 km broad system around the 3,400 m elevation Precambrian Tibesti Massif 120 km northeast of the photo. The dark tones of the ridges are wind polished coatings of wind-borne clay minerals and iron oxides which obscure the identity of the underlying rock. They are relatively thin, from 0.005 to 0.5 mm thick. The system of sand-filled stream channels is fossil from Tertiary and Quaternary pluvial stages in the Sahara. Ef1 are sand sheet deposits in a 600 m broad shallow depression. Fig. 52 B (Bands 3-2-1), 25 Aug. 2003, scene coverage 1,665 km2 The regional streak erosion pattern is well expressed spectrally in this satellite image. The yardangs are clearly associated with the slightly elevated outcropping sandstones. The smooth pale beige areas are slight depressions infilled with Fig. 51 sand sheets. The light grey patches are probably recently exposed sandstone outcrops that do not have wind-polished coatings. Environmentally this strong wind system transports diatomaceous dust deflated from the surface of Megachad Lake in the Bodéle Depression 100 km to the south across the tropical Atlantic to provide nutrients to the Amazonian forest.

 Transverse (ridges transverse to the dominant wind direction).  Barchan (crescentic accumulations with wings that advance downwind faster than the higher center giving the crescentic form).  Parabolic (crescentic with a convex nose which advances downwind leaving paired wings which trail the center of the dune on either side. In contrast to the barchan dune these are dune types that develop asymmetrically by movement of the sand up the gentle windward slope of the deposit toward the crest; as sand crosses the crest to the lee side it avalanches down the slipface, which is near the angle of repose for sand 33º to 35º. As avalanching continues the dune migrates in the direction of the wind. Rates of migration average 6 to 10 meters per year and can exceed 25 m per year.) Geohazard relations Wind erosion and deposition go hand in hand. Sand abrasion undercuts structures close to ground level. The directional drift of active migrating dunes buries agricultural land, overrides linear facilities such as roadways, pipelines and airfields, and clogs irrigation canals. Figure 53 linear dunes (class. Ed1.1) Characterization These dunes, also termed longitudinal, are the most common desert dune type. They are elongate, sharpcrested parallel ridges with slipfaces on both sides, and with the long axis extending in the direction of prominent winds. Individual dunes average 20 m in height with a basal width five to ten times the height. They are spaced up to one kilometer apart and can attain great lengths (more than 160 km) and heights.

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Fig. 53A (E69 34 N25 34), contact scale 1: 35,000, source USGS This stereomodel shows a group of northeast oriented linear dunes with lakes in interdune depressions. A broad depression is cultivated and partly flooded. Fig. 53B (Bands 7-4-2), 28 Sept. 2001, area coverage 4,640 km2 This image shows the photo area to be at the margin of an extensive area of linear dunes that are of the Thar Desert of northwest India and the central Sind Plain of the Indus Valley in southern Pakistan. The dunes in this scene are 2% of the 200,000 km2 Thar Desert. They are approximately 5 ka in age. The dunes are approximately 200,000 km2 in age. The dunes trend north-northeast under the influence of a regional unimodal wind regime. They average 2 km wide and are commonly 20 km long. Surface wind flow in summer is from the southwest and from northeast in winter. The dunes stabilized in Mid to late Holocene. See the same Unit in the north part of Fig. 50B. The canal-irrigated summer cotton and rice cropland of the relatively low Khipro Plain is one of the most productive of the areas that were severely flooded during the summer monsoon of August 2010. The grey areas in the valley are patches of surface salinity wasteland.

Part II The Examples

Figure 54 dune complexes (class. Ed2) Characterization These dunes are a coalescence of two or three different dune Units. Fig. 54A (E04 29 N24 15), contact scale 1: 50,000, source IGN, France This stereo triplet in southern Algeria covers a 16 km long complex linear and transverse dune belt. The belt is choking a wadi (an intermittently dry stream bed) and creating a local ponding area. Fig. 54B (Bands 3-2-1), 17 July 2010, area coverage 1,680 km2 The image shows the photo area dune belt to be part of a sinuous 25 km long deposit completely choking wadi Assouf Mellène to its junction with another wadi. The white areas are granite plains in an area of light grey low-weathering metamorphic basement rocks. The eastern third of the scene comprises units of dark grey resistant rocks of an Upper Proterozoic orogenic belt of the Hoggar Massif described in Fig. 5B.

Section 6 Basinal Sediments

Basinal sediments are lakebed deposits of extinct inland bodies of standing water. They are classified in three Units:  L1 Glaciolacustrine lakebeds (Fig. 55).  L2 Arid zone lakebeds (Fig. 56).  L3 Drained lakebeds (Fig. 57).

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Interpretations of Basinal Sediments Figure 55 glaciolacustrine lakebeds (class. L1) Characterization These lakes form when meltwater is trapped between the front of a glacier and a moraine (Fig. 83) or rock wall. The sediments are layered in varves of yearly seasonal deposition. A layer of light-colored sand and silt is deposited in summer; a darker layer of clay is deposited in quieter winter. Thicknesses range from a few to several hundred meters. Fig. 64B shows a 625 km2 area of the 465,000 km2 present extent of 11,500 Ka mega Lake Agassiz Geohazard relations Glaciolacustrine sediments are susceptible to a number of processes that constitute hazards or severe constraints on construction. Bearing capacities are poor; shear strengths are low and can decrease with depth. Susceptibility to frost in cold temperatures can be high. The soils can have high moisture contents and be difficult to handle and compact. Fig. 55A (W86 09 N42 34), contact scale 1: 25,000, source USGS. This single photo on the eastern shore of Lake Michigan in the Upper Pleistocene glaciated lowlands of the central USA shows the contrast in tonalities, land use, and micro relief between the flat, dark agricultural fields of market gardening crops on the clayey sediments, and the orchards, vineyards and woodlots on the brighter, rolling glacial till soils (Fig. 83) labeled Gt2. Fig. 55B (Bands 4-3-2), 13 July 2008, area coverage 408 km2 The delineated extension of the lakebed resolves the land use land cover patterns of the photo and also dark high-groundwater zones. Adjacent terrain is glacial till of two continental end moraines (Fig. 83). The pond pitted Unit east of the lake is hummocky and wooded. The Unit west of the lake is less rugged and cultivated as in the photo. Both are at 200 m elevation, the lake bed is at 190 m. The Lake Border End Moraine was deposited 13,800 years ago by a readvance southward of the Lake Michigan ice lobe. The eastern moraine (Valparaiso) was deposited by the earlier ice lobe retreat.

Part II The Examples

Figure 56 arid lakebeds (class. L2) Characterization These flattest of all landforms, also termed playas, are beds of clay encrusted with precipitated salts in Holocene desert lake basins, with no outlet. Pluvial lakebeds are relict basins formed in response to late Pleistocene, 1.6 million BP, and climatic conditions of enhanced rainfall. They occupy the numerous floors of inland basins with shallow water in a wet season but drying out later. Occurrences have great variations in size, ranging from a few to hundreds of square kilometers. The water in playas is derived from groundwater and precipitation in the catchment area. The mechanical and chemical deposition of evaporite minerals is controlled by the hydrology of the basin. These occur as alternations of relatively insoluble muds and clays and soluble surface efflorescent crusts of evaporite salines which do not persist as sedimentary strata. Geohazard relations Playas may support aircraft landings or be totally impassible to any vehicles. “Giant desiccation fissures up to 1 m wide and 10 m deep occur prefentially on hard, dry playa crusts, especially where long term drought has occurred, or where humans have lowered groundwater levels over protracted intervals…(elsewhere) salt ridges form from thermal expansion of salt and from the capillary rise of brine, they may be 60 cm high in places and are a clear hazard to traffic of any kind” (Neal 1998). In general, image tones suggest the condition of a playa: bright-toned areas will probably be dry crust, but the material beneath the crust may be wet. Heavy vehicles can break through such crusts. Fig. 56A (E51 06, N31 31), contact scale 1: 55,000, source personal archive This stereotriplet of photos taken circa 1955 in western Iran shows a 35 km2 playa at the low north end of an intermont basin marked Un3. The basins are infilled by alluvial successions. Local elevations are indicated. The cultivation in this basin is irrigated by streams from groundwater recharged sources in large bajada (Fig. 59) fans 5 km south of the basin. Mean annual precipitation in this part of Iran is anomalously 700 mm (average 300 mm). A dark central zone of the playa is wet, the bright areas are evaporites. Fu1.3 are coalesced bajada fans (Fig. 59).

Section 6 Basinal Sediments

Fig. 56B (Bands 3-2-1), 04 Aug. 2009, area coverage 5,330 km2 The isolation of such enclosed basins in a wilderness of barren Mid-Cretaceous/Lower Tertiary limestone Zagros fold ranges (Fig. 36) is well illustrated in the scene. Part of a similar basin can be seen 35 km northward on the center edge of the scene. The present site is at 1,840 m elevation, while surrounding ranges rise to 3,000 m. Figure 57 drained lakebeds (class. L3) Characterization Some lakes in humid climates have been artificially drained and the groundwater table lowered to produce additional areas of productive soils for agricultural uses. The surfaces are characterized by integrated systems of buried tiles and open drains. Geohazard relations (see Figure 55) Fig. 57A (E23 10 N38 20), contact scale 1: 40,000, source Photo Interprétation Éditions ESKA, France This stereomodel covers 47 km2 of the northeast extremity of the 200 km2 intermont basin Lake Copais in the Parnassos zone of Greece at Kastron. The Kp1 island in the lower right is 67 m above the lake level. The 14th-12th century BC Mycenean fortified city of Gla is in its center. Kp1 descriptors indicate enclosing karst carbonates sedimentary rocks. Fig 57B (Bands 3-2-1), 12 Aug. 2010, area coverage 875 km2 The image emphasizes the limited coverage of the photo area of this large karstic polje (Fig. 19) at 90 m elevation. The polje was drained in the period 18671887. Its canal system flows into Lake Hylice on the right. The surrounding uplands are barren.

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Section 7 Fluvial System Sediments

Fluvial system sediments are depositional Geounits that form a hydrologic continuum of 15 Units and 10 Variants from upland margin to valley fill and deltaic depo sites ordered in five Subgroups. These are part of the geomorphology of the subaerial erosional cycle of land degradation and deposition which responds to changes of climate, base level and tectonics. Sediment is transferred along stream channels by the sole force of flowing water. Erosional networks of small rills on slopes above the upland margin are unclassified. The Subgroups are:  Fu – Upland margin Units are fan-shaped deposits that issue from a confined channel at a marked break in slope (Figs. 58, 59).  Fv – Valley fill Units are the suspended and bed loads carried and deposited in river channels (Figs. 60 to 64).  Fv1/Fv2 – Composite Units are bimodal deposits that combine both high and low energy sediments.  Fw – Holocene deltas are accumulations of river sediments actively being deposited where a stream debouches into a receiving basin (Fig. 65).  Fr – Climatic deltas occur in intracratonic arid basins.

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Interpretations of Fluvial System Sediments Subgroup Fu Upland Margin Units Figure 58 fan-delta (class. Fu1.2) Characterization This Variant of the Unit alluvial fans progrades into lakes or seas. Fans are beds of unconsolidated coarse detrital sediments transported and deposited by mainly swift-flowing streams in gullies and ravines at the base of tectonically active mountain fronts. Fan surface slopes are generally less than 10º, and typically range in size from 1 to 1,000 km2, with the larger ones attaining a thickness of up to 700 m. Satellite images note occurrences up to 15,000 km2. Fig. 58A (W72 24 N18 32), contact scale 1: 40,000, source IGN, France The four kilometer broad low-dipping fan delta of this stereo model in Haiti has prograded 1.5 km into the sea. The sediment was deposited by a stream flowing down from 400 m high Tertiary limestone mountain ranges. A coral reef rim is 500 m off the west lee shore of the fan’s local ocean currents, with effluent from the city in suspension in the intervening shallow lagoon. The presence of the reef paralleling the fan shape is evidence of the age of this fan. The fan is densely populated by the town of Léogane, (population 134,000). Fig. 58B (Bands 3-2-1), 18 Sept. 2007, area coverage 600 km2 The image shows the fan to be deposited into the bay of Port au Prince, 10 km west of the city. The white channel of the tributary river indicates a high bed load high energy braided stream (Fig. 60) capable of delivering the sediments to build the delta. The limestone mountains of the Massif de la Selle to the south are covered mainly in scrub vegetation.

Part II The Examples

Figure 59 bajada fans (class. Fu1.3) Characterization The term bajada refers to alluvial fans in dry mountain environments that coalesce as an apron along the base of a mountain front from high rates of flash stream discharges of high sediment loads. Fig. 59A (E51 03 N31 22), contact scale 1: 40,000, source personal archive This stereo pair shows a delineated apron of coalescing fans in Iran that slopes down 300 m from an apex at 2,300 m elevation, a length of two km, to a cultivated basin at 2,000 m elevation. The high ridges rise to 3,000 m. Fig. 59B (Bands 3-2-1), 04 Aug. 2009, area coverage 1,400 km2 In this image the fans are seen to be on the east limb of a northwest-trending breached anticline (Fig. 36) in Cretaceous/Tertiary limestones folded 13.9 Ma at the interplay of the African and Arabian plates. The site is 15 km southwest of the basin appearing in upper right of Fig. 56. Geohazard relations of Upland margin Units Fans are hazardous environments for structures and transport lines. They are subject to unpredictable flash flooding, erosion and sedimentation. Road washouts and plugging of culverts result from flash floods.

Section 7 Fluvial System Sediments

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Subgroup Fv. Valley Fill Units

Figure 60 braided deposits, high gradient setting (class. Fv1.1)

This Subgroup consists of two basic floodplain channel pattern Units, Fv1 Braided and Fv2 Meandering that incorporate numerous distinct hydrodynamic variables. The Units are composed of sediments derived from upland sources. They are transported by traction, and in suspension, to be ultimately deposited in stretches of a valley as a result of reduction of gradients, water volumes, and velocities. Stream flow sorts sediment particles by density, grades them by size, and stratifies them in successive beds. The main characteristics of the two Units are compared as follows:

Characterization This Variant is the result of an unstable seasonal or climatic flow regime which builds horizontally bedded imbricate deposits of coarse gravels and cobbles in interlaced wide, shallow, multiple low sinuosity channels and elongate bars parallel to flow.

Characteristic

FV1

Fv2

Gradient

High

Low

Flow velocity (competence)

High

Low

Sediment size

Large

Small

Sediment load

Large

Small

Sediment transport dominant

Bed load

Suspended load

Geohazard relations Braided river floodplains are notoriously unstable and provide poor foundation conditions. They present an active depositional environment with rapid and continuous shifting of the sediment and the position of channels which are difficult for engineers to control. Fig. 60A (W130 37, N57 03), contact scale 1: 31,680, source Courtesy of Ministry of Sustainable Resources, Government of British Columbia This stereomodel covers the mid reach of More Creek at elevation 600 m in the Cordillera of northern British Columbia. Surrounding peaks are at 1,800 m. The characteristic braided floodplain is 500 m wide. The terraces, labeled k, are forested, indicating the bed has not flooded for a minimum 20 year period. The Units labeled Mf3 are old debris flow deposits. These are masses of cobbles and boulders embedded in a matrix of fine material, with a quantity of water that forms a slurry and moves downslope very rapidly. The larger deposit has constricted and displaced the channel, which, if it had been larger, would have become a landslide dam as in Fig. 94. The flows are located in gullies in Upper Triassic volcanic and sedimentary rocks. Fig. 60B (Bands 3-2-1), 14 Sept. 1990, area coverage 1,600 km² This scene shows More Creek’s alpine setting, carrying the flow of four tributary streams, some rising at glaciers of 1,600 to 2,000 m elevation. The braided channel of the lower reach continues below the debris flow constriction.

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Part II The Examples

Figure 61 braided deposits, low gradient setting (class. Fv1.2)

Figure 62 braided deposits, low gradient setting (class. Fv1.2)

Characterization Deposits of this Variant occur in broad valleys in mountainous regions or piedmont plains. Braided streams in such sites are determined by climatic conditions that produce high seasonal discharge fluctuations, e.g. low latitude monsoons, high latitude snow melt, wet-dry seasons in savannah zones and African Sahelian countries.

Characterization (see Figure 61)

Fig. 61A (E73 04 N32 30), contact scale ± 1: 40,000, source personal archive This photo pair covers a reach of the Jhellum River in Pakistan’s west Punjab plain of the upper Indus basin. The site is in the summer monsoon dry phase of the western Indian subcontinent. The pattern of stabilized (vegetated) and active bars is typical of this Variant. A dark residual high water channel is on the north bank with a high groundwater site behind the bank. The arrows indicate bare gravel deposits from flood waters of relatively small tributaries coming down from the mountains of Fig. 61B, which spread out and invaded the fields of the plain before reaching the main river. The deposits appear more extensively on the photo mate included in the extra material on the Springer website. They are relics from earlier torrential rains in the mountains. Fig. 61B (Bands 3-2-1), 18 June 2010, area coverage 500 km2 This scene of a 25 km reach of the Jhellum river shows it in a bank-full stage, covering the active bars of the photo. The image is visibly divided into distinct landscapes on either side of the river. The beige land on the northwest consists of non-irrigated, rainfed piedmont soils. The white and dark zones near the river are high groundwater and saline evaporites. The area on the southeast is canal-irrigated cropland on fertile soils of an old meander floodplain (Fig. 63). A series of grey alluvial fans are visible along the north edge of the scene. They are at the base of a mountain front north of the image.

Fig. 62A (W137 14 49 N68 46 57), contact scale 1: 68,000, source Courtesy of Natural Resources Canada This airphoto model taken in 1954 shows a seasonally high energy braided river in a northern subarctic region. The delineated components of the unit include F, the bright bare bar and channel complex of the active floodplain; L are low terraces 0.5 to 10 m above stream level; H are high terraces which stand 30 to 50 m above river level. Fig. 62B (Bands 3-2-1), 18 July 2002, area coverage 3,120 km2 This image acquired near a half century after the airphoto covers the eastern third of the 200 km long glaciomarine (Fig. 80) Yukon coastal plain. The plain, underlain by unconsolidated Quaternary sediments, is of low relief, 0 to 150 m elevation. The photo area is in a lower reach of Blow River which has a great seasonal variation in discharge. It rises 80 km inland at 1,500 m elevation in the western Richardson Mountains. Its elevation at the south edge of the image is 80 m. The terraces and braid bars are distinguishable. A zoom of the image reveals significant changes in channel bars. Due to its relatively larger drainage basin the river has built a delta that has prograded 5 km into Mackenzie Bay. The grey area on the east is the western edge of the Mackenzie Delta. The zone of lakes near the coastline are thermokarst (thawing of ground ice) basins associated with lacustrine sediments that lie behind the 30 m bluffs of the shoreline. They are inset two to six meters below the general level of the plain. The overall green color of the scene reflects the tundra vegetation cover. The area was deglaciated 18,000 years ago.

Section 7 Fluvial System Sediments

Figure 63 meandering deposits (class. Fv2) Characterization This Unit is characterized by a single, highly sinuous channel with two hydrologic discharge stages bankfull and overbank which determine the basic channel pattern:  Bank-full stage water flow velocities on the out and in sides of channel bends produce discrete sites of erosion and deposition by a complementary hydraulic cut-and-fill process. The resulting sinuosity of the channel is what has given such a stream valley the appellation meandering.  Over-bank flood stage produces discharges that exceed the channel capacity, causing floodwaters to leave the channel, and part of the suspended sediment to be deposited initially as levee banks immediately bordering the channel. The fine sediments are deposited further out onto the adjacent floodplain. Geohazard relations Flooding is the dominant geohazard of meandering rivers and their valleys. “Flooding causes loss of life and damages property and infrastructure (e.g. bridges and pipelines) can be damaged structurally or be destroyed by fast-flowing water and/or impacts from debris (ice, trees) carried by the current. Lateral bank erosion can damage or destroy buildings and infrastructure by undermining them, even when they are situated above the level of inundation. Bridge abutments or pier supports may be scoured and undermined in areas where they constrict or accelerate the flow. Bridges can also partly dam flow and be overtopped by water, causing the approaches to be washed out. Floodwaters can wash out roads, highways and railway lines. Artificial dams may be breached by overtopping flood flows.” Brooks et al 2001. Fig. 63A (W139 22 N64 02), contact scale 1: 70,000, source Courtesy of Natural Resources Canada The bright wormlike patterns in this stereomodel of the meandering Klondike River and Bonanza Creek floodplains are tailings from dredge mining of placer gold in paleochannels of the streams. These flow into the braided Yukon River at Dawson just north of the junction. The source of the placers is in uplift and erosion of gold-bearing schists in Late Tertiary time. J3.3 is schist terrain of Fig. 63B.

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Fig. 63B (Bands 3-2-1), 20 Sept. 2010, area coverage 4,200 km2 The image shows mining activity extending up to 40 km eastward up the Klondike River plain and terraces, and 60 km southeastwards up the valleys of tributary streams. Country rocks are Paleozoic schists (Fig. 33) at 800 m general elevation. The low relief land to the northeast is part of the Tintina Trench one of the great faults in western North America. The mountain terrain is forested with subalpine white spruce, and aspen in the beige areas. The image provides a good depiction of the relief of unglaciated terrain of the Ogilvie Mountains, with weathered rock and colluvium as surficial deposits on slopes (compare Fig. 92B). Figure 64 meandering deposits (class. Fv2) Characterization (see Figure 63) Fig. 64A (W97 14 N49 02), contact scale 1: 15,000, source Courtesy of Natural Resources Canada The photos taken 07 May 1950 show extensive flooding of the town of Emerson and surrounding land along a lower reach of the Red River on the border of Manitoba and the state of Minnesota in the Interior Plains. Arrows indicate the international boundary. The flood in the Red River basin in 1950 was an international natural disaster based on the number of people evacuated and affected by the flood. 2,000 km2 of land was flooded in Manitoba alone. A critical concurrence of a number of meteorological conditions contributed to exceptional runoff at the time. The peak discharge at Emerson on 13 May was 2,670 m3/sec. Fig. 64B (Bands 3-2-1), 22 April 2010, area coverage 625 km2 This scene shows a 20 km reach of the meandering Red River flowing through the cereal and mixed farming plain of glaciolacustrine (Fig. 55) Lake Agassiz. The river appears bankfull at data acquisition date. The silty clays of the lake and the younger alluvial deposits of the river form an unusually flat plain that is notorious for flooding in the spring.

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Subgroup Fw Holocene Deltas Figure 65 arcuate deltas (class. Fw1) Characterization These fan-shaped deltas occur where a large debris supply from a river debouches into a receiving basin, ocean, inland sea, or lake. The sizes and shapes of deltas vary greatly throughout the world. They consist essentially of distributary plains and distributary channels where they are unconfined, as on coastal and alluvial plains. The deltas develop chiefly by pronounced progradation of streams with large, relatively coarse sediment loads. The Subgroup includes four hydrologic and morphologic Units: arcuate, elongate, estuarine, and cuspate. Geohazard relations Fluvial flooding, tidal flooding, storm surges (Subgroup coastal plains) are geohazards common to coastal deltas. Maritime infrastructures located on distributary plains and channels are all subject to these hazards. Global climate changes and associated sea level rise are a serious threat to all deltaic environments.

Part II The Examples

Fig. 65A (E12 29 54, N47 51 28), contact scale 1: 20,000, source Selbstverlag der Bundesforschungsanstalt für Landeskunde und Raumordnung Bonn-Bad Godesberg This three photo sequence of a small 2 km2 but classic delta documents the progradation of the Tiroler Ache into the Chiemsee in eastern Bavaria over a 35 year period. Fig. 65B (Bands 3-2-1), 10 July 2010, area coverage 300 km2 The image shows the circled delta and 10 km of the lower reach of the 80 km long Ache River (mountain stream) flowing into the 80 km2 moraine-enclosed (Fig. 83) Chiemsee at 516 m elevation. A zoom shows that the delta front has prograded 500 m in the 50 year period 1960-2010. White areas at the mouths of distributaries indicate current deposition of silt and mud. The Ache River rising at 1,270 m a.s.l. in the wooded Austrian Kitzbuhel Alps at the bottom of the scene descends 750 m to 518 m at the delta. The average middischarge is 35.5 m3/sec. The mixed woodlot and agriculture landscape is typical of the glaciated alpine foreland of end moraines and glacial till plains in Europe. The land between the lake and the mountains is a glaciolacustrine plain (Fig. 55) of the larger postglacial Chiemsee. The dark zones in the plain are wooded wetlands, not woodlots.

Section 8 Marine Littoral Systems

The coast is a zone of interaction between processes of erosion and deposition in the sea and on the land. The changes which various coasts are undergoing, long term retreat and short term cliff erosion, are dependent on the character of the coasts. A classification of coastal Geounits involves the disciplines of oceanography and climatology in addition to geology. The coastal geomorphologic system, one of the largest, comprises 23 Units and nine Variants ordered in eight Subgroups:  Br – Bedrock littorals are shorelines that are at the landward limit of marine processes on a rock coast (Figs. 66, 67).  Bb – Residual shorelines are bluffs, steep banks ramping 5 to 50 m in height in unconsolidated sediments.  Bw –Wave and current formed sediments are beaches and offshore sand bars (Figs. 68 to 71).  Bl – Sea ice related forms are shore and beach materials that are moved by ice beyond the competence of other processes (Fig. 72).  Bf – Holocene coral reefs are underwater structures made by marine organisms that secrete calcium carbonate (Figs. 73 to 75).  Bt – Tidal regime deposits are tide-borne sediments that are deposited in protected bodies of coastal waters such as lagoons (Figs. 76, 77).  Bc – Coastal plains are emerged portions of continental shelves (Figs. 78 to 81).  Bp – Carbonate platforms are carbonate blankets in warm shallow waters of continental shelves in low latitudes.

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Section 8 Marine Littoral Systems

Fig. 80B

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Fig. 81B

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Interpretations of Marine Littoral Systems Subgroup Br Bedrock Littorals Figure 66 high rock cliffs (class. Br2) Characterization Lithologically cliffs occur in rock types of high mass strength. Structurally they result from sustained regional scale tectonic uplift and transitory isostatic rebound. They are the product of the combination of marine and subaerial processes. Mechanical wave action at the cliff foot during storms is the primary marine agent of erosion. This is accomplished by quarrying, abrasion and corrasion. Freeze-thaw, hydration, oxidation solution, and salt crystal growth are the principal subaerial weathering processes. They exploit the internal structural weaknesses (joints, faults, bedding) of cliffs that result in high intensity, low frequency mass movements. Fig. 66A (W119 55 N34 04), contact scale 1: 20,000, source USGS The stereogram covers two km of a 145 m high rock cliff headland in Miocene basalts, marked Br2. The Br6 Unit is a 15 m tectonic eustatic marine terrace (due to sea level changes or tectonic uplift) in Cretaceous schists. Fig. 66B (Bands 3-2-1), 21 March 2000, area coverage 700 km2 The image shows 20 km of the 35 km long 250 km2 Santa Cruz island lying 30 km off the mainland coast of southern California. The island is a composite Unit formed by the fusion of two terranes which are divided by a prominent active strike-slip fault (Fig. 44) that crosses its center. The island is an extension of the onshore Santa Monica Mountains of the Transverse Ranges. The highest peak on the northern terrain is 750 m. The southern schist terrane is typically highly dissected. The island is one of a group of five that make up the Channel Islands National Park. It is covered in scrub oak and shrubs (chapparal) and some pines. The land area on the left is the east end of Santa Rosa island.

Part II The Examples

Figure 67 weak low rock cliffs (class. Br3.1) Characterization This Unit Variant consists of rocks of low strength due to composition, poor cementation, or high density of fracturing (Figs. 24, 25, 26). Geohazard relations Rock falls (Fig. 87), rock slides (Fig. 92), and rock slumps (rotational, backward tilting slide blocks) are the mass movements to which rock cliffs are susceptible, as a function of their lithology, structure, and environmental conditions in which they occur. Fig. 67A (W121, N35 28), scale 1: 100,000, source personal archive This single color vertical photo shows turbidity in the offshore waters at Point Estero, California. The point is 120 m high with a tectonic eustatic marine terrace (Fig. 66) at its surface. It is bordered north and south by a lower 20 m terrace. Fig 67B (Bands 3-2-1), 11 Nov. 2010, area coverage 700 km2 This image shows the photo area centered on a 30 km segment of the coast of central California from Morro Bay to Cambria. The turbidity can be faintly seen to extend along the coast north and east in the same Geounit. The sediment yield in the area has been calculated as 40–60 thousands of cubic yards per 1.6 km. The source rocks are of the Late Jurassic and Cretaceous Californian Franciscan Mélange – a complex mixture of hard blocks of rock embedded in soil-like matrices. The mountains inland, the Santa Lucia Range of the Coast Mountains, 150–250 m elevation, are part of the Franciscan Unit. Parallel lineaments in the northeast third of the image reflect the San Andreas strike-slip fault (Fig. 44) system.

Section 8 Marine Littoral Systems

Subgroup Bw Wave and Current Formed Sediments Figure 68 offshore bar (class. Bw2) Characterization Offshore bars are ridges of sand that parallel shorelines of coasts other than cliffs. They are subtidal and continuously submerged. They occur singly or as multiple ridges, and can be continuous or discontinuous for several kilometers. The bars are produced by strong storm waves that rework the seabed sands. Occurrences of these bars are indicated by breaking wave patterns 50 to 300 m offshore parallel to the coastline. Geohazard relations These bars are subject to erosion by storm wave and storm surge activity (an abnormal rise of several meters in the ocean level produced by the combination of high water and high winds). These waves and surges remobilize and redistribute the bar sediment. As submerged bottom features in areas normally dominated by dynamic marine conditions, they are potentially hazardous to surface navigation and marine engineering activities if uncharted or mispositioned. Fig. 68A (W75 31 N 35 14), contact scale 1: 10,000, source US Coast and Geodetic Survey This single photo at Cape Hatteras North Carolina taken in 1958, shows 4 km of breaking waves of a bar off Hatteras Island. Fig. 68B (Bands 3-2-1), 31 Oct. 2010, area coverage 215 km2 This image, which does not resolve the offshore bar at Cape Hatteras, shows 10 km of Hatteras Island barrier beach (Fig. 69) that extends continuously 90 km northward to enclose Pamlico Sound. The image shows that Hatteras is one of two barrier islands that intersect to produce the cape. Littoral currents from the north have extended the cape southward and currents from the west extended it eastward well beyond its position in 1958. The rip current pattern off the point reflects the convergence of the currents. Note the difference in color between Atlantic water and the suspended and solution loads of the shallow waters of the Sound which receives the inland waters of the Tar and Neuse Rivers.

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Figure 69 near-shore barrier beaches (class. Bw3) Characterization A barrier beach is a sand bar parallel to the shore which has been built by upward shoaling wave action so that its crest rises above the normal high-water tide level. The stability conditions of the beaches vary according to their alignment relative to the direction of wave approach, the size of the lagoon that they enclose, and the availability of littoral sediments. The barrier encloses a lagoon and its components (Fig. 76). Geohazard relations The low height and narrow width of these bars makes them susceptible to storm surges and particularly susceptible to sea level rise. They would be subject to overwashing and breaching during storms. Human impacts are also geohazard agents of these coastal beaches. There is no greater threat to them than extensive urbanization. Fig. 69A (W64 56 N47 20), source ReinsonGE (1980), the Coastline of Canada, GSC Paper 80 -10, fig.3.14, p 33 This site map of Tabusintac Bay marked Bt1 shows the characteristic depositional environment of barrier beaches on the northeast coast of New Brunswick, Canada. The example documents the migration southward of these barriers by strong longshore drift in response to short-period wind-generated storm waves from the northeast. Fig, 69B (Bands 7-4-2), 06 Sept. 2000, area coverage 1,365 km2 The image shows the map area to be in the center of a system of barrier beaches and lagoons (Fig. 76) extending along 70 km of the New Brunswick coast. They lie along a five to ten km wide agriculturally favorable plain of glaciomarine sediments (Fig. 79). These lagoons are at river mouths that were drowned by rising post-glacial sea levels. The light blue features on the beach side of the lagoons are tidal deltas. The scattered orange areas are zones of the peat industry extraction of sphagnum moss in bogs.

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Part II The Examples

Figure 70 bay barrier beaches (class. Bw3.1)

Figure 71 raised beaches (class. Bw4.1)

Characterization This barrier beach Variant differs from the Unit by extending between headlands of a bay frequently creating a lagoon. They may develop by longshore growth of attached beach spits, or by growth of emergent beaches offshore.

Characterization This beach Variant consists of ridges, behind and above the current active beach of marine plains (Fig. 78) and post-glacial isostatic rebound of glaciomarine plains (Fig. 79). Sea level rise causes an upward shift in the reach of coastal processes and would reactivate or drown these beaches.

Fig. 70A (W71 06 N41 30), contact scale 1: 5,000, source USGS This large scale color photo shows in the center a 400 m long 70 m wide, partly sand dune covered, barrier between two headlands of glacial till of the last continental glaciation (Fig. 83) on the Buzzard’s Bay coast of southern Massachusetts, USA. Fig. 70B (Bands 3-2-1), 30 Aug. 2010, area coverage 5,200km2 A series of 20 bay barrier beaches creating lagoons at the mouths of drowned small stream valleys, similar to the indicated photo area at the eastern end, can be counted along this 70 km length of coast of southern New England from Buzzard’s Bay, Massachusetts to Long Island Sound, Connecticut. The sediment to build the barriers was derived from headlands of erodible glacial till. This coast, with its western extension of Long Island, marks the southern limit of continental glaciation in eastern North America. Block Island at the bottom of the scene is glacial till.

Fig. 71A (E138 35 S16 47), contact scale 1: 90,000, source personal archive The single photo shows a series of dark, savanna vegetation-covered, raised beaches and white saline mudflats inland. Fig. 71B (Bands 3-2-1), 08 Sept. 2010, area coverage 6,000 km2 (land + water) The image extends the raised beach complex of the photo area to cover 80 kilometers of the east end of 450 km of similar shoreline on the very flat south coast of the north Australia Gulf of Carpentaria. This coast has prograded 30 km since the Middle Holocene by deposition of low tide muds over subtidal muds during periods of increased sediment input by the rivers. It is a rare modern example of an epicontinental sea (a shallow sea on top of a continental margin). The ridges rise up to 6 m above mean sea level and were deposited by storm surge waves. The Gulf is especially prone to tropical cyclones because of its warm shallow waters that have a maximum depth of 70 m.

Section 8 Marine Littoral Systems

Subgroup Bl Sea Ice Related Forms Figure 72 sea ice related forms (class. Bl1) Characterization This is a composite Geounit that constitutes the Subgroup. It incorporates the movements and geomorphic effects of sea ice motion on high latitude coasts. Sea ice can move sediments that are beyond the competence of other processes. Various types of shorelines and beach forms are developed during the short Arctic summer when mobile sea ice and waves strike the coast.  Ice thrust ridges are composed of beach and shore material forced up from the water’s edge by ride-ups of pack ice across the beach. The process is particularly effective in shallow coastal waters. Sharpcrested or rounded ridge heights range from three to four meters.  Boulder barricades are ridges of boulders derived primarily from glacial deposits. They range from 5 to 30 m wide, 0.5 to 3 m high, and are found at the low water line of tidal flats. They originate from shoreline erosion by ice and are concentrated where, during breakup, floating ice on the tidal flats stands against the persistent ice cover offshore.  Ice-rafted boulders occur scattered randomly on intertidal flats, they are typically one to two meters in diameter. They become frozen into the ice at low tide and are then transported – rafted, in the ice and set down on the tidal flat as the ice melts. Geohazard relations Sea ice is a major seasonal hazard to structures in the Arctic. During spring breakup ice floes composed of blocks 1 to 2 m thick are driven onshore by wind and waves and can pile up into ridges by buckling up to 30 m high. They override beaches, hit fixed objects with considerable force and are destructive of near-shore installations. Such overrides can take place in less than 30 minutes and are difficult to predict. Shores with boulder barricades are difficult to approach from the sea. They offer restrictions to boat landing operations and can only be crossed at high tide.

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Fig. 72A (W65 43 37 N66 08 37), contact scale 1: 3,180, source Courtesy of Natural Resources Canada These very large scale photos taken at low tide show a 30 m wide 2 m high boulder barricade marked by arrows at Pangnirtung settlement on the eastern side of the fjord on Baffin Island’s Cumberland Peninsula. The segment pictured in the photos is 950 m long and 50 m wide. The intertidal flat marked Bt2.1 (Fig. 77) varies from 175 to 275 m wide. Its surface is strewn with ice-rafted boulders. The settlement was established as a whaling station by the Hudson’s Bay Company in 1921, 10 km up the east side of the deep and sheltered waters of the 40 km long fjord. Fig. 72B (Bands 3-2-1), 14 July 1992, area coverage 1,200 km2 The arrow locates the photo area in the fjord. Pangnirtung and Kingnait fjord to the south, are sites where boulder barricades can develop at low tides during breakup. This image, acquired at breakup time, is on the northeast side of macrotidal (6 m) Cumberland Sound. The fjords are among the more than 30 that were produced by outlet glaciers from the Penny Ice Cap to the north, and other local ice fields on the heavily glacierized Cumberland Peninsula. Baffin Island is the uplifted eastern rim of the Canadian Shield. The highest point inland is 1,500 m, to the northeast. The fjord area was deglaciated 8,700 years ago.

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Subgroup Bf Holocene Coral Reefs Holocene reefs are the source of the fossil reefs of sedimentary rocks of Fig. 21. Figure 73 fringing reef (class. Bf1) Characterization Coral reefs are marine ecosystems composed of the carbonate skeletons of attached calcium-producing bottom dwelling organisms. Fringing reefs are attached to present coastlines in shallow waters of tropical and subtropical regions; they form platforms that are exposed at low tide. Geomorphologically they are controlled by the interplay of growth and erosion processes that produce components including, from seaward to inland, a growing, widening reef front, a reef flat, and a backreef zone. Fig. 73A (E116 05 S08 53), contact scale 1: 40,000 nominal, source personal archive This single photo looking south was taken at an angle of 30º from the vertical by the right side photo of the discontinued trimetrogon camera system The photo shows a low tide exposure of seven kilometres of the 80 km of coral reef that fringe the south coast of Lombok Island, Indonesia. Blongas Bay where, unaccountably, no reefs are now visible on the satellite image is on the right (west side). The forested and partly cleared terrain in the foreground is Miocene volcanic rocks at 150 m elevation. Fig. 73B (Bands 7-4-2), 19 Aug. 2000, area coverage 1,120 km2 The appearance of the thin blue lines of the fringing reefs in this scene indicates that the image data were acquired at a higher tide level than that of the airphoto. The image is centered on the southwest coast of Lombok Island 30 km east of Bali in the magmatic, tectonically active, east-west trending Indonesian island arc. Popcorn clouds are a near-perennial occurrence in Landsat scene selection in humid tropical latitudes.

Part II The Examples

Figure 74 raised reef (class. Bf1.1) Characterization As with raised beaches of Fig. 71 this emergent reef Variant is the result of tectonic uplift or eustatic lowering of sea level. Raised reefs characteristically form tabular platforms or stepped terraces. No surface drainage occurs since rainwater infiltrates the highly permeable coral. Some reflect stepwise emergence. Among the highest are sets in eastern New Guinea at S06 04 E147 30, these sequences reach up to 700 m above sea level. Fig. 74A (E39 16 46 S06 45), contact scale 1: 15,000, source personal archive The photos taken in 1962 show the three km wide Lower Pleistocene 12 m elevation Msasasi Peninsula raised coral reef complex of north of Dar es Salaam Tanzania. Holocene reefs fringe the peninsula’s shoreline. Fig. 74B (Bands 7-4-2), 30 June 2000, area coverage 600 km2 The image shows the now urbanized platform of the Msasasi Platform peninsula as part of a coastal structural basin to north and south which was affected by a global Upper Pleistocene glacio-eustatic lowering of sea levels. Fringing reefs (Fig. 73) are visible around the peninsula, off the island to the north, and southward along the coast.

Section 8 Marine Littoral Systems

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Figure 75 barrier reef (class. Bf2)

Subgroup Bt Tidal Regime Deposits

Characterization Progressive erosion and subsidence of a fringing reef coastline leaves a reef parallel to the coastline but separated from it by a relatively shallow lagoon.

Figure 76 salt marshes and mangrove swamps (class. Bt1c)

Fig. 75A (W72 58 N18 53), contact scale 1: 40,000, source IGN, France This stereo photo pair shows 6 km of barrier reef on the north coast of Gonave Island in southern Haiti. The enclosed lagoon contains a grey zone of mangroves (Fig. 76) backed by a 20 m wide band of salt flats that fringe fan deltas (Fig. 58). Upslope terrace levels are clearly evident. Fig. 75B (Bands 3-2-1), 29 Jan. 2010, area coverage 750 km2 (island area) This image shows 65 km long Gonave island, 45 km west of Port au Prince, to be ringed by bright blue barrier reefs round its north east and south coasts, and fringing reefs on its northwestern coast. The conjunction of tectonics and a 45 ka cycle of three carbonate deposits from the Eocene to the present in the North Deformed belt of the Caribbean lithospheric Plate is illustrated by this island which was tectonically uplifted in the Quaternary along its north and south microplate margins (reduced-size lithospheric plates). The three ages of limestone are distinguishable on the island by progressively younger segments from east to west. The southeast third, which rises to 600 m, (max 778 m) is composed of Eocene marine limestone. Fracture traces (Fig. 45) in this limestone are quite distinct. The center of the island is Miocene limestone. The western end consists of a mass of raised reefs (Fig. 74) of Quaternary age rising to 320 m elevation with visible successive terrace levels. A regional dry tropical climate combined with a droughty, porous, local lithology result in a waterscarce environment. A population of 80,000 lives by subsistence agriculture and a few fishing villages. The rust-colored patches between the photo frame and the south coasts are intensely-cultivated polje-like (Fig 19) depressions. Numerous other such sites are evident west of the photo area.

Characterization Salt marshes and mangrove swamps are one of five components of Geounit Bt1 lagoons, bodies of comparatively shallow salt water separated from the deeper sea by a barrier beach (Fig. 69). Lagoons are common along gently sloping coastal plains around the world. Salt marshes are dense stands of Halophytic plants (plants which can grow in saline conditions) which develop in the wave-protected environment of a lagoon. They are a flora of reed type rushes and cordgrass that occur as low and high types. Low marshes correspond to the upper intertidal zone (Fig. 77) with a muddy substrate. High marshes are supratidal and are more influenced by terrestrial conditions, with more permeable sands substrate. Both types are drained by a typical pattern of intricately meandering creeks. Sediment carried into a marsh by the rising tide is trapped by the vegetation and retained as the tide ebbs, gradually building up the marsh. Mangroves are tropical and subtropical shrubs and trees that grow in protected saline and brackish coastal sites. They are homologous to higher latitude salt marsh ecosystems. Fig. 76A (W74 49 47 N39 02 14), contact scale 1: 46,000, source USGS The single composite photo shows the typical pattern of meandering creeks (T) of a lagoonal salt marsh. C and L indicate the cultivated coastal plain (Fig. 78). Fig. 76B (Bands 7-4-2), 10 July 2001, area coverage 7,000 km2 This synoptic image covers the Atlantic Coastal Plain (elevations of four to 10 m) of southern New Jersey. Salt marshes appear grey. The photo area, north of Cape May, which partly encloses Delaware Bay on the left, is seen to be within a 90 km segment of a 150 km long marshfilled series of barrier beach-enclosed lagoons. The arrow points to the eight km long Atlantic City barrier. These barrier coasts are exposed to the full force of East Coast hurricanes. The dominant green color is the heavily forested regional Pine Barrens on agriculturally poor sandy soils.

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Figure 77 mud/sand intertidal slope (class. Bt2.1) Characterization Mud/sand is one of two intertidal slope Variants, the other being bedrock. Intertidal slopes, also termed flats develop along gently dipping sea coasts with marked tidal rhythms where enough sediment is available and strong wave action is not present. Many large tidal flats such as in macrotidal areas (> 4m) occur where they adjoin point sources (riverine) or line sources (continental shelves) where a large volume of sediment is available. The sediments are located between the high and low water lines over a vertical range of usually 2 to 3 m and up to 10 or 15 m depending on the tidal range. The twice-daily rise and fall of tide level causes the intertidal sea bed to be exposed for moderate to long periods, up to as much as 10 hours, (DaviesJL (1977). Fig. 77A (W03 10 N47 42), contact scale 1: 22,000, source IGN, France This single photo taken at low tide on the south coast of Brittany shows an intertidal site of large white mud flats up to 1,400 m wide in a 10 km long drowned valley with a subtidal channel running through the inlet. Aquaculture is practiced locally. Fig. 77B (Bands 3-2-1), 12 May 2001, area coverage 270 km2 This pixelly image shows the blue intertidal area of the Etel River to be at a higher tide level than the photo with the mud flats partly submerged. The site is in typical peneplaned (Fig. 34) low (about 5 m elevation) granite terrain of the 5 m macrotidal coast of south Brittany 15 km east of the port of Lorient. Etel village is on the east bank just upstream from the river’s mouth, sand beaches and notorious (unresolved) offshore bar (Fig. 68) for river navigation.

Part II The Examples

Subgroup Bc Coastal Plains More than 70% of the world’s population lives on coastal plains, and 11 of the world’s largest cities are on coastal estuaries. (Greenpeace International) These plains occur on emerged portions of continental shelves. They are underlain by repetitive sequences of Cenozoic marine deposits. This Subgroup includes four Units:  Bc1 cyclic sediment plains (Fig. 78).  Bc2 passive margin sediments (on an inactive plate margin).  Bc3 glaciomarine plains (Figs. 79, 80).  Bc4 fluviomarine plains (Fig. 81). Figure 78 cyclic sediment plains (class. Bc1) Characterization The deposits of cyclic plains represent repetitive transgressive-regressive cycles of Pleistocene and Holocene marine and alluvial deposits caused by eustatic or tectonic changes in sea level. The last eustatic event was the postglacial Flandrian Transgression which affected coastal plains worldwide from 18,000 to 6,000 BP. Modern sediments are not fixed in time and space and migrate laterally and vertically. They are relatively thin with a gentle seaward dip, generally