Landscapes and Landforms of the Maltese Islands [1st ed. 2019] 978-3-030-15454-7, 978-3-030-15456-1

Table of contents :
Front Matter ....Pages i-xxv
Introduction to Landscapes and Landforms of the Maltese Islands (Ritienne Gauci, John A. Schembri)....Pages 1-5
Front Matter ....Pages 7-7
The Geographical Context of the Maltese Islands (John A. Schembri)....Pages 9-17
Central Mediterranean Tectonics—A Key Player in the Geomorphology of the Maltese Islands (Pauline Galea)....Pages 19-30
Sedimentary Evolution and Resultant Geological Landscapes (Saviour Scerri)....Pages 31-47
A Synthesis of Different Geomorphological Landscapes on the Maltese Islands (Ritienne Gauci, Saviour Scerri)....Pages 49-65
Front Matter ....Pages 67-67
By Gentlemen for Gentlemen—Ria Coastal Landforms and the Fortified Imprints of Valletta and Its Harbours (John A. Schembri, Stephen C. Spiteri)....Pages 69-78
Landscapes, Landforms and Monuments in Neolithic Malta (Reuben Grima, Simon Farrugia)....Pages 79-90
Cave Dwellers at Għar il-Kbir: Malta’s Best Documented Troglodytic Community (Keith Buhagiar)....Pages 91-101
Humans as Agents of Geomorphological Change: The Case of the Maltese Cart-Ruts at Misraħ Għar Il-Kbir, San Ġwann, San Pawl Tat-Tarġa and Imtaħleb (Derek Mottershead, Alastair Pearson, Paul Farres, Martin Schaefer)....Pages 103-116
Malta’s Submerged Landscapes and Landforms (Mariacristina Prampolini, Federica Foglini, Aaron Micallef, Mauro Soldati, Marco Taviani)....Pages 117-128
Dwejra and Maqluba: Emblematic Sinkholes in the Maltese Islands (Ivan Calleja, Chiara Tonelli)....Pages 129-139
Palaeosoils: Legacies of Past Landscapes, with a Series of Contrasting Examples from Malta (Paul Farres)....Pages 141-152
The Terraced Character of the Maltese Rural Landscape: A Case Study of Buskett Area (Stephan Micallef)....Pages 153-165
The Spectacular Landslide-Controlled Landscape of the Northwestern Coast of Malta (Mauro Soldati, Stefano Devoto, Mariacristina Prampolini, Alessandro Pasuto)....Pages 167-178
Limestone Dissolution and Temporary Freshwater Rockpools of the Maltese Islands (Sandro Lanfranco, Kelly Briffa)....Pages 179-191
Fomm Ir-Riħ and the Vigorous Nature of Its Shingle Beaches (Sephora Sammut)....Pages 193-202
A Coastal Enclave Worth Conserving: Xatt L-Aħmar (the ‘Red Coast’, Gozo) (Alan Deidun, Arnold Sciberras, Adrian Ciantar)....Pages 203-212
The Beaches of the Maltese Islands: A Valuable but Threatened Resource? (Marie Louise Zammit Pace, Malcolm Bray, Jonathan Potts, Brian Baily)....Pages 213-227
Ras il-Ġebel: An Extreme Wave-Generated Bouldered Coast at Xgħajra (Malta) (Joanna Causon Deguara, Saviour Scerri)....Pages 229-243
Saline Marshlands of the Maltese Islands (Sandro Lanfranco, Lara Galea, Talitha Van Colen)....Pages 245-259
Filfla: A Case Study of the Effect of Target Practice on Coastal Landforms (Stefano Furlani, Ritienne Gauci, Stefano Devoto, John A. Schembri)....Pages 261-271
Tsunamigenic Landscapes in the Maltese Islands: The Comino Channel Coasts (Derek Mottershead, Malcolm Bray, Joanna Causon Deguara)....Pages 273-288
Landform Loss and Its Effect on Health and Well-being: The Collapse of the Azure Window (Gozo) and the Resultant Reactions of the Media and the Maltese Community (Bernadine Satariano, Ritienne Gauci)....Pages 289-303
Landforms and Processes at II-Majjistral Park and Its Environs (Avertano Rolé)....Pages 305-316
Sea Caves and Coastal Karst Scenery along the Maltese Coasts: The Case Study of Blue Grotto (Stefano Furlani, Ritienne Gauci, Sara Biolchi)....Pages 317-324
Selmun: A Coastal Limestone Landscape Enriched by Scenic Landforms, Conservation Status and Religious Significance (Sephora Sammut, Ritienne Gauci, Robert Inkpen, Jessica Jade Lewis, Andy Gibson)....Pages 325-341
The Physical Characteristics of Limestone Shore Platforms on the Maltese Islands and Their Neglected Contribution to Coastal Land Use Development (Ritienne Gauci, Robert Inkpen)....Pages 343-356
Front Matter ....Pages 357-357
Landscape Diversity and Protection in Malta (Louise Spiteri, Darrin T. Stevens)....Pages 359-372
The Sustainability of Landforms and Landscapes (Maria Attard)....Pages 373-380
Back Matter ....Pages 381-385

Citation preview

World Geomorphological Landscapes

Ritienne Gauci John A. Schembri Editors

Landscapes and Landforms of the Maltese Islands

World Geomorphological Landscapes Series Editor Piotr Migoń, Department of Geography, Faculty of Law, University of Wrocław, Wrocław, Poland

More information about this series at http://www.springer.com/series/10852

Ritienne Gauci • John A. Schembri Editors

Landscapes and Landforms of the Maltese Islands

123

Editors Ritienne Gauci Department of Geography Faculty of Arts University of Malta Msida, Malta

John A. Schembri Department of Geography Faculty of Arts University of Malta Msida, Malta

ISSN 2213-2090 ISSN 2213-2104 (electronic) World Geomorphological Landscapes ISBN 978-3-030-15454-7 ISBN 978-3-030-15456-1 (eBook) https://doi.org/10.1007/978-3-030-15456-1 Library of Congress Control Number: 2019934533 © Springer Nature Switzerland AG 2019 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, 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. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

This volume is dedicated to all those esteemed individuals who over the years have contributed to the success of the Department of Geography at the University of Malta. A special mention goes to late Mrs. Marlene Schembri and late Mrs. Mary Abela.

Foreword

With a population of over 470,000 people in 2017 and an area of 316 km2, Malta is the most densely populated country in the European Union and yet has a wide variety of landscapes, which makes the country a fascinating natural laboratory for the geographer and environment specialist. Indeed, one of the strong themes in both the landscape history of the islands and the contemporary study of its landforms is the impact people have made over millennia and are making on the natural environment some, but by no means all of it, being deleterious. Human impact is heightened by seasonal flows of tourists, with the islands hosting 2.3 million in 2017, a number which has doubled since 2009. Malta is an archipelago of three main islands and a number of islets located in the central Mediterranean. Formed predominantly of limestone, it has been worked into its distinctive landscapes by a combination of physical processes. These include tectonic, karstic, marine and subaerial processes, with the latter influenced by high summer temperatures with pronounced drought conditions, cooler climatic episodes punctuated by periods of intense rainfall and flooding. As a result, coastal features of the islands include a number of landforms, with landslides and other erosional systems being conspicuous. Often generated under conditions of intense rainfall and exploiting underlying features of the sedimentary geology, landslides create distinctive landscapes and present a hazard threat to people and their activities. As far as marine environments are concerned, the Maltese Islands have a rich variety of coastal landscapes which include inter alia: high cliffs; rias; boulder beaches; coastal wetlands; coastal karst; sandy beaches and shore platforms, landscapes that have been shaped by a variety of marine processes and which include storms and possible tsunamis generated by distant earthquakes. Contemporary processes of economic development, many of which relate both to marine servicing industries in the harbours and to tourism in all areas, are also concentrated at the coast and are major forcing factors of human-induced landscape change. This volume represents a considerable academic achievement on the part of its editors, and they are fully justified in taking considerable pride in the achievements of their writing team in producing a valuable addition to the international series on World Geomorphological Landscapes. As external reviewer of this volume, I have read and commented on every chapter and have been impressed, not just by how many individual scholars have been involved in producing high-level contributions, but also by the quality of the research upon which the chapters are based. Much of the writing and all of the editing has been expertly handled by the academic staff of the Department of Geography at the University of Malta. Alumni from this department, many of whom have been awarded Masters and Ph.D. degrees by research, have also contributed chapters. In contrast to many other volumes in the series, the Landscapes and Landforms of the Maltese Islands has its origin within a department of just four full-time academic staff, but which has clearly established itself a leading centre for the study of Mediterranean geomorphology. Maltese landscapes and landforms are explored in twenty-nine chapters divided into three parts. The first part, entitled Background, deals with: the geographical context; central Mediterranean tectonics; the evolution of the sedimentary geology and key geomorphological features. The bulk of the volume comprises twenty-two local case studies, which explore and vii

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Foreword

critically review a wide array of detailed investigations encompassing: ria coastal landforms and their fortified imprints; landforms of the Neolithic; Malta’s submerged landscapes; cave dwellers and their impacts; rural terraced terrains; sinkholes and solutions subsidence; palaeosoils; landslides; freshwater rock pools; the sandy cove of Xatt l-Aħmar; an intriguing study of Filfla islet and the impact of aerial bombing and naval bombardment on its morphology; a detailed study of an extreme wave-generated boulder beach at Xgħajra coast; the Il-Majjistral Nature Park and saline marshlands and coastal wetlands. An interesting discussion on the collapse of the world-famous sea arch, the Azure Window, on Gozo and its effect on health and well-being is followed by chapters on: sea caves and coastal karst; shingle beaches; threats to beach environments; shore platforms; tsunamigenic landscapes and the geomorphological impacts of ancient cart-ruts. The book concludes with a comprehensive review of landscape diversity and protection polices and a fine conclusion on the important theme of sustainability. It is a pleasure to have been invited to write this foreword, and I have no hesitation in commending Landscapes and Landforms of the Maltese Islands without reservation to a wide audience. This should not only include academic readers, but also others who like me have been awestruck by the beauty and uniqueness of Maltese landscapes. Liverpool, UK

Prof. David K. Chester

Series Editor’s Preface

Landforms and landscapes vary enormously across the Earth, from high mountains to endless plains. At a smaller scale, nature often surprises us creating shapes which look improbable. Many physical landscapes are so immensely beautiful that they received the highest possible recognition—they hold the status of World Heritage Sites. Apart from often being immensely scenic, landscapes tell stories which not uncommonly can be traced back in time for tens of millions of years and include unique geological events such as meteorite impacts. In addition, many landscapes owe their appearance and harmony not solely to the natural forces. For centuries, and even millennia, they have been shaped by humans who have modified hillslopes, river courses, and coastlines, and erected structures which often blend with the natural landforms to form inseparable entities. These landscapes are studied by Geomorphology—‘the Science of Scenery’—a part of Earth Sciences that focuses on landforms, their assemblages, surface and subsurface processes that moulded them in the past and that change them today. Shapes of landforms and regularities of their spatial distribution, their origin, evolution and ages are the subject of research. Geomorphology is also a science of considerable practical importance since many geomorphic processes occur so suddenly and unexpectedly, and with such a force, that they pose significant hazards to human populations and not uncommonly result in considerable damage or even casualties. To show the importance of geomorphology in understanding the landscape, and to present the beauty and diversity of the geomorphological sceneries across the world, we have launched a book series World Geomorphological Landscapes. It aims to be a scientific library of monographs that present and explain physical landscapes, focusing on both representative and uniquely spectacular examples. Each book will contain details on geomorphology of a particular country or a geographically coherent region. This volume presents the geomorphology of Malta—a European country in the heart of the Mediterranean realm. Malta, comprising an archipelago of 316 km2 in total, may seem too small to afford a separate volume in the series. The authors of the book show us, however, that such a view would not do justice to the geomorphic landscape of Malta which represents striking diversity, especially along the coastline. Malta is a textbook of rock coast geomorphology and structural relief of limestone plateaus, but many other facets of the islands are revealed here, including spectacular geoarchaeology associated with megalithic temples. In fact, the multiple interrelationships between geomorphology and humans can be hardly better displayed than in Malta. The World Geomorphological Landscapes series is produced under the scientific patronage of the International Association of Geomorphologists (IAG)—a society that brings together geomorphologists from all around the world. The IAG was established in 1989 and is an independent scientific association affiliated with the International Geographical Union (IGU) and the International Union of Geological Sciences (IUGS). Among its main aims are to promote geomorphology and to foster dissemination of geomorphological knowledge. I believe that this lavishly illustrated series, which keeps to the scientific rigour, is the most appropriate means to fulfil these aims and to serve the geoscientific community. To this end, my great thanks go to Dr. Ritienne Gauci and Prof. John A. Schembri for adding this book to ix

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their busy agendas, successfully coordinating the large, multinational team of authors, and delivering such an exciting illustrated story to read and enjoy. I also acknowledge the excellent work of all individual authors who share their expert knowledge of Malta with the global geomorphological community. Finally, I thank Prof. David K. Chester for accepting the role of an external reviewer and ensuring that the final product is of the highest quality. On a more personal note, I had twice the privilege to visit Malta, to enjoy its natural scenery and to admire its cultural landscapes. The Maltese landslides, visited in the company of Prof. Mauro Soldati and his research group, are an unforgettable experience. I am sure that this book, through accessible storytelling and great images, will provide a stimulus to many geoscientists, who have not yet seen Malta, to add the islands to their planned geomorphological itineraries. Piotr Migoń Series Editor

Contents

1

Introduction to Landscapes and Landforms of the Maltese Islands . . . . . . . . Ritienne Gauci and John A. Schembri

Part I

Background

2

The Geographical Context of the Maltese Islands . . . . . . . . . . . . . . . . . . . . . John A. Schembri

3

Central Mediterranean Tectonics—A Key Player in the Geomorphology of the Maltese Islands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pauline Galea

4

Sedimentary Evolution and Resultant Geological Landscapes . . . . . . . . . . . . Saviour Scerri

5

A Synthesis of Different Geomorphological Landscapes on the Maltese Islands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ritienne Gauci and Saviour Scerri

Part II 6

9

19 31

49

Selected Geomorphological Landscapes

By Gentlemen for Gentlemen—Ria Coastal Landforms and the Fortified Imprints of Valletta and Its Harbours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . John A. Schembri and Stephen C. Spiteri

7

Landscapes, Landforms and Monuments in Neolithic Malta . . . . . . . . . . . . . Reuben Grima and Simon Farrugia

8

Cave Dwellers at Għar il-Kbir: Malta’s Best Documented Troglodytic Community . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Keith Buhagiar

9

1

69 79

91

Humans as Agents of Geomorphological Change: The Case of the Maltese Cart-Ruts at Misraħ Għar Il-Kbir, San Ġwann, San Pawl Tat-Tarġa and Imtaħleb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 Derek Mottershead, Alastair Pearson, Paul Farres, and Martin Schaefer

10 Malta’s Submerged Landscapes and Landforms . . . . . . . . . . . . . . . . . . . . . . 117 Mariacristina Prampolini, Federica Foglini, Aaron Micallef, Mauro Soldati, and Marco Taviani 11 Dwejra and Maqluba: Emblematic Sinkholes in the Maltese Islands . . . . . . . 129 Ivan Calleja and Chiara Tonelli

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12 Palaeosoils: Legacies of Past Landscapes, with a Series of Contrasting Examples from Malta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 Paul Farres 13 The Terraced Character of the Maltese Rural Landscape: A Case Study of Buskett Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 Stephan Micallef 14 The Spectacular Landslide-Controlled Landscape of the Northwestern Coast of Malta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 Mauro Soldati, Stefano Devoto, Mariacristina Prampolini, and Alessandro Pasuto 15 Limestone Dissolution and Temporary Freshwater Rockpools of the Maltese Islands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 Sandro Lanfranco and Kelly Briffa 16 Fomm Ir-Riħ and the Vigorous Nature of Its Shingle Beaches . . . . . . . . . . . . 193 Sephora Sammut 17 A Coastal Enclave Worth Conserving: Xatt L-Aħmar (the ‘Red Coast’, Gozo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 Alan Deidun, Arnold Sciberras, and Adrian Ciantar 18 The Beaches of the Maltese Islands: A Valuable but Threatened Resource? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 Marie Louise Zammit Pace, Malcolm Bray, Jonathan Potts, and Brian Baily 19 Ras il-Ġebel: An Extreme Wave-Generated Bouldered Coast at Xgħajra (Malta) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 Joanna Causon Deguara and Saviour Scerri 20 Saline Marshlands of the Maltese Islands . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 Sandro Lanfranco, Lara Galea, and Talitha Van Colen 21 Filfla: A Case Study of the Effect of Target Practice on Coastal Landforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261 Stefano Furlani, Ritienne Gauci, Stefano Devoto, and John A. Schembri 22 Tsunamigenic Landscapes in the Maltese Islands: The Comino Channel Coasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 Derek Mottershead, Malcolm Bray, and Joanna Causon Deguara 23 Landform Loss and Its Effect on Health and Well-being: The Collapse of the Azure Window (Gozo) and the Resultant Reactions of the Media and the Maltese Community . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 Bernadine Satariano and Ritienne Gauci 24 Landforms and Processes at II-Majjistral Park and Its Environs . . . . . . . . . 305 Avertano Rolé 25 Sea Caves and Coastal Karst Scenery along the Maltese Coasts: The Case Study of Blue Grotto . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317 Stefano Furlani, Ritienne Gauci, and Sara Biolchi 26 Selmun: A Coastal Limestone Landscape Enriched by Scenic Landforms, Conservation Status and Religious Significance . . . . . . . . . . . . . . . . . . . . . . . 325 Sephora Sammut, Ritienne Gauci, Robert Inkpen, Jessica Jade Lewis, and Andy Gibson

Contents

Contents

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27 The Physical Characteristics of Limestone Shore Platforms on the Maltese Islands and Their Neglected Contribution to Coastal Land Use Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 Ritienne Gauci and Robert Inkpen Part III

Conclusion

28 Landscape Diversity and Protection in Malta . . . . . . . . . . . . . . . . . . . . . . . . . 359 Louise Spiteri and Darrin T. Stevens 29 The Sustainability of Landforms and Landscapes . . . . . . . . . . . . . . . . . . . . . 373 Maria Attard Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381

Editors and Contributors

About the Editors Ritienne Gauci is a Lecturer in Physical Geography at the Department of Geography of the University of Malta. Her research interests are mainly in coastal geomorphic processes and resultant landforms, rocky coasts, geoheritage and melitensia cartography. She holds a B.A. (Hons) and M.A. in Geography from the University of Malta and a Ph.D. from the Department of Geography of the University of Portsmouth, UK. Ritienne is currently the national scientific representative for the International Association of Geomorphology (IAG), member of the British Society of Geomorphology (BSG) and the Royal Geographical Society (RGS-IBG). She is also on the committee board of the Malta Map Society and acts as consultant editor for the Malta Map Society Journal. She has authored and co-authored a number of papers, also in collaboration with European universities such as the University of Portsmouth, Liverpool Hope University, University of Trieste and University of Modena and Reggio Emilia. John A. Schembri is a Professor at the Department of Geography of the University of Malta. He read Contemporary Mediterranean Studies and History as an undergraduate at the University of Malta. This was followed by post-graduate studies at Durham University from where he obtained an M.A. in the Geography of the Middle East and the Mediterranean and later a Ph.D. through the Department of Geography at Durham. In 2016 he was conferred D. Educ. (Honoris Causa) by Liverpool Hope University, UK, for his contribution to Geography. John lectures in Geography at the University of Malta and his publications range from coastal land use, historical geography to cartography. John is a Chartered Geographer and a Fellow of The Royal Geographical Society (with IGB). He contributes regularly to lectures at the International Ocean Institute.

Contributors Maria Attard is an Associate Professor, Head of Geography and Director of the Institute for Climate Change and Sustainable Development at the University of Malta. She studied at the University of Malta and completed her Ph.D. in 2006 at UCL (London). Maria is active in NECTAR and Steering Committee Member of the World Conference on Transport Research. She is Co-editor of the journal Research in Transportation Business and Management, Associate Editor of the journal Case Studies in Transport Policy and Co-editor of the Emerald Book Series on Transport and Sustainability. Brian Baily is a Senior Lecturer in environmental geography and GIS within the Geography Department at the University of Portsmouth, UK. His research interests are coastal change, GIS for monitoring change, environment foot printing and land utilization mapping.

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Sara Biolchi is research fellow at the University of Trieste (Italy), where she works as geologist and geomorphologist in coastal and karst areas. She collaborates in several international projects, co-funded by the European Union, which deal with water management and natural heritage of the karst environment. She obtained her Ph.D. in Geomorphology at the University of Modena and Reggio Emilia (Italy). She is author or co-author of more than 20 international and national papers and of about 40 contributions in national and international congresses. Malcolm Bray is a Visiting Research Fellow in the Department of Geography at the University of Portsmouth, UK. He gained a Ph.D. in coastal geomorphology from the London School of Economics in 1996. His research interests include coastal sediment budgets, gravel beaches and reconstruction studies of high energy wave impacts. He has provided guidance to local and national authorities on sediment transport, beach erosion problems, shoreline management and coastal conservation. Kelly Briffa was born in Ta’ l-Ibraġ, Malta, in 1992. She holds a Bachelor of Science (Hons) degree in Biology and Chemistry from the University of Malta, and is currently studying Medical and Pharmaceutical Biotechnology at the IMC University of Applied Sciences, Krems, Austria. She has carried out extensive research on the effect of rockpool morphometry on the species richness of aquatic plants, and has recently co-authored papers and posters at the International Congress of the European Pond Conservation Network (EPCN). Keith Buhagiar is a Ph.D. graduate in archaeology from the University of Malta specialising in Maltese Medieval and Early Modern cave-settlements, rural landscape development and related water management systems. Dr. Buhagiar is a visiting lecturer in Palaeochristian, Byzantine and Medieval archaeology with the Department of Classics and Archaeology and the Faculty of Theology, both at the University of Malta. Research interests include central Mediterranean, North African and Near Eastern water management systems, troglodytism and Mediterranean settlement location and distribution as well as scientific rural landscape investigation. Ivan Calleja is a geographer and holds a B.A. (Hons) (Melit.) and an M.A. (Melit.) from the Geography Department of the University of Malta. He currently teaches Geography at secondary and tertiary levels. He is also Visiting Lecturer at the Department of Geography of the University of Malta. His research interests are in karstic processes and landforms, geosites and geotourism, soil erosion and land degradation processes in Mediterranean environments. Joanna Causon Deguara is a geographer, with a B.A. (Hons) (Melit.) and an M.A. (Melit.) from the Geography Department of the University of Malta. Her research interests are in coastal processes, geomorphology of bouldered beaches and geomorphological mapping. In collaboration with the Geography Department of the University of Malta, she has published on coastal boulder geomorphology of the Maltese Islands, and was involved in similar research with other European universities such as the University of Portsmouth, UK and the University of Trieste, Italy. Presently, Joanna lectures and carries out fieldwork sessions in physical geography for the Department of Geography at the University of Malta. David K. Chester is a graduate of the Universities of Durham (1973) and Aberdeen (1978) and has been involved in research on natural hazards (especially volcanic eruptions and earthquakes), landscape change in the Holocene and geomorphology, for over forty years. Employed for most of his career at the University of Liverpool, where he still holds an honorary fellowship, he is currently Professor of Environmental Science at Liverpool Hope University. Professor Chester is a priest in the Church of England.

Editors and Contributors

Editors and Contributors

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Adrian Ciantar is a geographer and holds a B.A. (Hons) (Melit.) from the Department of Geography of the University of Malta. He is Gozitan and has researched extensively on Xatt l-Aħmar for his undergraduate thesis, under the supervision of Dr. Saviour Scerri. He presently lives in Canada. Alan Deidun is an Associate Professor within the Department of Geosciences at the University of Malta. He is currently involved in several areas of coastal and marine biology, oceanographic research and is Project Manager on a number of EU-funded projects, including: PANACEA (www.panaceaproject.net); BIODIVALUE (www.biodivalue.com); PERSEUS (www.perseus-net.eu), MED-JELLYRISK (www.jellyrisk.eu) and SeaofSkills (http://www. seaofskills.eu). Through the PANACEA project, the first ever marine environmental education centre in the Maltese Islands was opened at Dwejra (Gozo) in March 2013. He has authored over 100 peer-reviewed papers published on various thematics relating to coastal and marine biology, although he still retains an interest in sandy beach ecology, which he first addressed during his Ph.D. studies. Professor Deidun is also deeply involved in environmental advocacy, having penned a newspaper column for the past 15 years which has received journalism awards on three occasions. In total, he has written over 450 popular science and environmental advocacy articles in local newspapers and magazines. Stefano Devoto obtained his Ph.D. in Geomorphology at the University of Modena and Reggio Emilia (Italy). His Ph.D. research was focused on the study of coastal landslides of NW Malta. He currently works at the University of Trieste (Italy) with a research grant. He has published more than 40 contributions in international journals and congresses and has been involved in national and international projects. Paul Farres is currently a Visiting Research Fellow in the Department of Geography at the University of Portsmouth, having previously taught and researched in the Department from 1974 to 2014. Major activities focused on earth surface materials and processes and main publications concern soil erosion, specifically rainsplash mechanisms and soil crusting. Simon Farrugia is a geography graduate from the University of Malta who completed a dissertation project on aeolian geomorphological processes at Ħaġar Qim. He also holds an M.Sc. in Environmental Monitoring and Assessment from the University of Southampton, UK. His research interests include aeolian processes, geographic information systems and quantitative tools for environmental monitoring. Simon’s contributions include several peer-reviewed publications, local radio productions and public lectures on environmental monitoring and aeolian processes. Federica Foglini is a researcher at the Institute of Marine Sciences—CNR in Bologna, Italy, and her main interests are focused in seafloor geomorphological mapping, design and management of Marine Geodatabase, development and implementation of WebGIS systems and digital cartography in the framework of European and National projects. She is involved in seafloor habitat mapping, high-resolution reflection seismic and stratigraphic interpretation, multibeam swath bathymetry acquisition and processing. She is co-author of international scientific papers and wrote several technical reports about implementation and design of Marine Geodatabase and GIS mapping. She often boards oceanographic expeditions as party chief, to supervise data collection and processing.

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Stefano Furlani is an Associate Professor at the Department of Mathematics and Geosciences of the University of Trieste, Italy. His research deals with coastal geomorphology and sea level change with special emphasis on coastal karst and climatic change. He leads the Geoswim project for the snorkel surveying of the Mediterranean coasts. He is assistant editor of the Editorial Board of Alpine and Mediterranean Quaternary. He is author or co-author of about 100 papers. Lara Galea was born in Żurrieq, Malta, in 1993 and holds a B.Sc. in Biology and Chemistry and an M.Sc. in Biology. She has co-authored papers and posters in refereed journals and conferences. She has also pursued further research on wetland biota at the Catholic University of Leuven, in Belgium. Pauline Galea graduated with a B.Sc. in Mathematics and Physics from the University of Malta in 1977 and M.Sc. in Physics in 1979. She obtained her Ph.D. in Geophysics from the University of Wellington, New Zealand in 1994, after which she took responsibility of seismic recording and monitoring at the University of Malta. She is now Head of the Department of Geosciences and coordinates the Seismic Monitoring and Research Group, which manages the Malta Seismic Network and several geophysical applications. Her research interests are mainly the seismicity, tectonics and seismic hazard in the Central Mediterranean, and geophysical studies of the shallow subsurface. Andy Gibson is Principal Lecturer and Leader of the Centre for Applied Geosciences within the Faculty of Science of the University of Portsmouth, UK. He is an engineering geomorphologist involved in the investigation and management of geological hazards and adaptation to the impacts of climate change. Andy is involved in numerous research projects including landslides in China, the geotechnical properties of the Hampshire Basin, and the impacts of geohazards on the UK economy and tourism industry. He is currently collaborating with the Department of Geography of the University of Malta on the geo-material properties of shore platforms. Reuben Grima is a Senior Lecturer in cultural heritage management in the Department of Conservation and Built Heritage at the University of Malta. He studied archaeology at the Universities of Malta and Reading, and read for his Ph.D. at the Institute of Archaeology, University College London. From 2003 to 2011 he served with Heritage Malta as Senior Curator responsible for prehistoric World Heritage Sites. His research interests include archaeology of landscapes, cultural landscapes, and engagement of the public with the past. Robert Inkpen is a Reader in Physical Geography at the University of Portsmouth, UK. He has published on a diverse range of research including the erosion of shore platforms, the decay and conservation of heritage materials, bacterial decay of stone and the philosophy of physical geography. He views academic research as having a key role to play in the practical conservation of environments as well as in the informing decision makers and the public of the social and cultural value of these underrated assets. Sandro Lanfranco was born in Sliema, Malta, in 1966, and holds a Ph.D. in vegetation ecology. He lectures in Biology at the Department of Biology of the University of Malta. His main research interests are the ecology and systematics of plants. He has carried out or directed several studies, including long-term ones, on freshwater pools and their biota. He has authored or co-authored several scientific studies, technical reports, book chapters and books.

Editors and Contributors

Editors and Contributors

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Jessica Jade Lewis is a Geotechnical Engineer for Fugro, UK. She previously completed her B.Sc. Geology at the University of Leicester, before going on to study M.Sc. Geological and Environmental Hazards at the University of Portsmouth. Her M.Sc. thesis was part of the Erasmus programme with the Geography Department of the University of Malta concerning landslide hazards in Xemxija. Aaron Micallef is a Marie Curie Fellow and an Associate Professor at the Department of Geosciences, University of Malta. His expertise is in marine geology and geomorphology, in particular submarine canyons and landslides, fluid flow processes, and geomorphometry. He has co-published 27 papers and book sections, and contributed to 30 international conference communications, on these research topics. Aaron is also chairman of the International Association of Geomorphologists’ Submarine Geomorphology working group. Stephan Micallef is a geographer, and holds a B.A. (Hons) from the Department of Geography at the University of Malta. During his undergraduate studies, he researched on the perspectives of agritourism development on the Maltese Islands. In 2015, he was awarded an M.A. (Summa cum Laude) for his research on the effectiveness of rubble walls in retaining soil particles and water. His research interests are vested in the relationships of anthropogenic processes with the environment, with focus on sustainable development, agriculture, soil resources, water processes, culture, ecology and human adaptations to changing land-uses. Derek Mottershead is currently Visiting Research Fellow in the Department of Geography, University of Portsmouth, UK. He gained a Ph.D. in geomorphology from University of London King’s College in 1972 and has studied landforms in varied environments in Norway, Spain, Malta, Mallorca, New Zealand, Canada and USA, in addition to his long-term association with Southwest England. He has published a significant number of geomorphic studies in coastal geomorphology and is also a co-author of a systems-based undergraduate text on physical geography. He has been a longstanding executive committee member of the British Geomorphological Research Group (now British Society for Geomorphology). Alessandro Pasuto is Research Director at the Research Institute for Geo-Hydrological Protection of National Research Council in Padova, Italy. His expertise mainly deals with applied geomorphology and engineering geology with special reference to landslide hazard assessment and monitoring. He is founder and director of GRJL, Italy–Japan joint laboratory on Hydro-Geological risks, foundation member of TellNet, International Disasters Transfer Live Lesson Network. He is also member of the Executive Committee of the CERG, European Centre on Geomorphological Hazard of the European Council. He is author or co-author of more than 170 scientific papers and has been guest-editor of two special issues of Geomorphology. Alastair Pearson graduated from the University of Leeds in 1982 in Geography/History and completed a postgraduate Diploma in Cartography at University College of Swansea in 1983. He then joined the staff at Portsmouth as Map Librarian and became Head of the Geographical Information Services Unit in 1987 before appointment as lecturer in 1991. He was awarded a Ph.D. in 1996 and promoted to Principal Lecturer in 1997. He teaches GIS at undergraduate and postgraduate levels and leads field courses to Malta and Sicily. His other recent publications have concentrated on the history of cartography in the twentieth century. Jonathan Potts is a Principal Lecturer in coastal management in the Department of Geography at the University of Portsmouth, UK. He leads its long established M.Sc. course in Coastal and Marine Resource Management. His research interests within coastal management include institutional and policy frameworks, spatial planning, public participation, education and interpretation.

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Mariacristina Prampolini is a post-doctoral grant holder at CNR-ISMAR of Bologna and at the University of Modena and Reggio Emilia (Italy) carrying out research on the geomorphological evolution of the Maltese coasts since the Last Glacial Maximum to better understand the kinematics of active processes along the shorelines and on the seafloors. She is also expert in benthic habitat mapping. She is Member of the Associazione Italiana di Geografia Fisica e Geomorfologia (AIGeo). Avertano Rolé lectures in Physical Geography at the University of Malta within the Geography Department. His main interests are geomorphology, soil erosion, and land degradation, and he has published several papers and official reports related to these fields. Other main academic interests include integrated coastal zone management. He participated, and led a number of EU and UNEP projects which addressed environmental issues related to this field. Mr. Rolé is very active in the field of environmental and geographic education and often leads groups of students, teachers, and other interested persons in guided field trips around various places within the Maltese Islands and abroad. Sephora Sammut holds a B.A. (Hons) (Melit.) and an M.A. (Melit.) from the Department of Geography at the University of Malta and is a visiting lecturer within the same department. Her main area of interest is coastal geomorphology, in particular the morpho-sedimentary dynamics of shingle beaches. She has participated in conferences in both the local and foreign scenes, and published her research in international journals. Bernadine Satariano is a Lecturer in Geography, with a B.A. (Hons) (Melit.), P.G.C.E. (Melit.), M.A. (Melit.) from the University of Malta and a Ph.D. (Dunelm). Her main area of interest explores how important place is for human health and wellbeing. She focuses on the socio-geographical processes related to inequalities in health and wellbeing within a Maltese context. Her recently published work explores: the social determinants of health within Maltese neighbourhood communities; the intergenerational processes and their impact on the health and wellbeing of adults and children; and the impact of neighbourhood social and cultural norms on child wellbeing. She is also involved in a research project focusing on children’s geographies. She presented some of her research studies at the University of Portsmouth, Durham University, Paris Nanterre University, University of San Francisco, University of Angers and Cardiff University. She is a Fellow of the Royal Geographical Society (F.R.G.S.). Saviour Scerri studied at the University of Malta and graduated as B.Sc. in Physics and Chemistry in 1972. He furthered his studies at the University of Milan where he graduated in Geology in 1976. He started his career as a ground engineer with Soil Mechanics. After four years he joined the Oil Exploration Department of the Government of Malta as a petroleum geologist where he specialised in seismic data interpretation and prospect generation. Presently he is working as a Consulting Geologist. His work includes mineral resource assessments, geo-environmental impact assessment and subsurface ground investigations. He is also engaged as a part time visiting senior lecturer (Geology) at the University of Malta. Martin Schaefer graduated in Geography from Sheffield University. He obtained an M.Sc. in GIS (2001) and a PGC in Learning and Teaching in Higher Education (2006), both from University of Portsmouth. His current role is GIS Manager in the Department of Geography at Portsmouth, and he also teaches on undergraduate and postgraduate programmes as a part-time lecturer. He contributes to research projects in Spatial Data Management, Surveying and Data Capture, Arctic & Alpine Climate and Historical GIS & Cartography and has co-authored several publications in these fields.

Editors and Contributors

Editors and Contributors

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Arnold Sciberras is an active Maltese naturalist and has contributed to the description of numerous novel faunal species in the Maltese Islands, especially of insect, arachnid and reptile taxa. Observation of animal behaviour is one of his key specialisations, especially that of lizards, and he was a founder member in 2012 of the Malta Herpetological Society. He sat for a number of years on the editorial board of The Central Mediterranean Naturalist, a Maltese peer-reviewed journal, and has participated in numerous sampling expeditions on small islands and islets, having documented for the first time the fauna and flora colonising all the islets which are to be found around the coastline of the Maltese Islands. Mauro Soldati is Full Professor of Geomorphology at the Department of Chemical and Geological Sciences of the University of Modena and Reggio Emilia, Italy. His research deals with geomorphology and slope instability, with special emphasis on landslides and climatic change. He is President of the International Association of Geomorphologists (IAG) for the period 2017–2021. He is a member of the Editorial Board of the Geomorphology, as well as of other international journals, and has been guest-editor of special issues of the journal dealing with landslides. He is author or co-author of about 150 papers. Louise Spiteri is a lawyer by profession, and currently she is the Chief Executive Officer of the Environment and Resource Authority of Malta. She obtained a LL.D. at the University of Malta in 1999 and a Magister Juris Degree in Public International Law in 2001. Dr. Spiteri has extensive working experience in the legal arm of environmental regulations, and in international and EU legal negotiations. She was also a lawyer linguist at the European Court of Justice and dealt with EU infringement cases, on behalf of Malta in front of European Court of Justice. She currently lectures on environmental and resource law at the University of Malta, and is working on a Ph.D. research on climate change law and the insurance market, at Imperial College London, UK. She has published articles mainly on environmental legislation and Malta’s international environmental obligations, and a monograph on environmental law in Malta with Kluwer publishers. Stephen C. Spiteri was born in Malta, 15 September 1963 and holds a Dipl. (Int. Des.) RI, B.A. (Hons) and Ph.D. Educated at St Aloysius College, B’Kara and later at the University of Malta, Dr. Spiteri specializes in the military architecture of the Hospitaller Knights of St John and the fortifications of the Maltese Islands. He is the author of a number of books and studies on the military history and fortifications of Malta, the Knights of St John, and British Colonial defences. He is a founding member of the Sacra Militia Foundation for the Study of Hospitaller Military and Naval History. Dr. Spiteri is also a part-time Senior Lecturer at the International Institute of Baroque Studies at the University of Malta, where he lectures and undertakes research on the history and development of military architecture, and on the art and science of fortification. Darrin T. Stevens is currently occupying the post of Deputy Director Environment and Resources within the Environment and Resources Authority (ERA), where he is handling various issues related to Strategic International and National Affairs, Information Resources Management, Biodiversity and Nature Protection, Water (including Marine issues), Desertification and Land Degradation, and issues linked with Genetically-Modified Organisms and the environment, with particular reference to the implementation and coordination of the National Biodiversity Strategy and Action Plan, the development of the State of the Environment Report, as well coordination on various international commitments, including the EU Habitats Directive and Natura 2000, the EU Marine Framework Directive and selected aspects within the EU Water Framework Directive, the EU Biodiversity Strategy to 2020, the EU Regulation on Invasive Alien Species and the UN Convention on Biological Diversity. He is

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also the Maltese national focal point for a number of international multilateral biodiversity treaties under the European Union, Council of Europe and United Nations, and is also author of a number of peer-reviewed scientific and popular articles and other publications, and was actively involved with various environmental NGOs. Marco Taviani is a marine geologist and paleobiologist at the Institute of Marine Sciences— CNR in Bologna as Research Director, and has worked on many projects in the Mediterranean basin, Red Sea, Atlantic Ocean, Indian Ocean and Antarctica. His main research interests focus on biogenic carbonate factories, hydrocarbon-imprinted carbonates, deep water coral ecosystems, habitat mapping and paleoceanography. Has carried out over 40 oceanographic missions on board Italian, German, French and US research vessels; his expertise includes ROV operations, manned submersibles, drill coring, and SCUBA diving. He is active in popularizing Science in scientific documentaries, TV and radio. Chiara Tonelli is a natural scientist and has a Ph.D. in earth system sciences. Her field of research is in geomorphology and her research interests are karst processes and landforms and their relationships to gravity and sea-level change. Talitha Van Colen was born in Malta in 1995 and holds a B.Sc. (Hons) (Melit.) in Biology from the University of Malta, where she carried out research on the flora of saline marshlands of the Maltese Islands. Marie Louise Zammit Pace is a geography graduate of the University of Malta and currently a part-time Ph.D. student in the Department of Geography at the University of Portsmouth, UK. Her research concerns beach management in both urban and rural environments, in small islands and with particular reference to the Maltese Islands. She is also an Assistant Environment Protection Officer at the Environment and Resources Authority (ERA), Malta. Her research interests are beach management, marine spatial planning, and public participation.

Editors and Contributors

Abbreviations

ACM AEI AHLS AHLV asl BC BCE BP C1 C2 ca. COE EAFRD EC eNGO EPD ERA FFNHPR GL GN GPS LCL LGLM LGM MCA MEPA MGLM MRRA MTA NBSAP NEN ODZ SAC SCI SCRZ SDS SL SPA SPED SSI TLGLHg

Archivum Cathedralis Melitae Area of ecological importance Area of high landscape sensitivity Area of high landscape value Above sea level Blue Clay Before Common Era Before Present Lower Phosphorite Conglomerate Bed Upper Phosphorite Conglomerate Bed Circa Council of Europe European Agricultural Fund for Rural Development European Commission Environmental Non-governmental Organisation Environment Protection Department Environment and Resource Authority Flora, Fauna and Natural Habitats Protection Regulations Globigerina Limestone Government notice Global positioning system Lower Coralline Limestone Lower Globigerina Limestone Member Last glacial maxima Malta Communications Authority Malta Environment and Planning Authority Middle Globigerina Limestone Member Malta Resources and Rural Authority Malta Tourism Authority National Biodiversity Strategy and Action Plan National Ecological Network Outside development zone Special Area of Conservation Site of Community Importance Sicily Channel Rift Zone Sustainable development strategy Subsidiary legislation Special protected area Strategic Plan for the Environment and Development Site of Scientific Importance Terminal lower Globigerina Limestone hardground xxiii

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TPA UCL UGLM VO WFD

Abbreviations

Tree protection areas Upper Coralline Limestone Upper Globigerina Limestone Member Voluntary organisation Water Framework Directive

Units of Measurement

cm g ha ka kg km km2 km h−1 m m2 m3 m/s µS cm−1 mi mm mS cm−1 mya nmi s

centimetres grams hectares kilo-annum (i.e. one thousand years) kilograms kilometres kilometres squared kilometres per hour metres metres squared metres cube metres per second microsiemens per centimetre miles millimetres millisiemens per centimetre million years ago nautical miles seconds

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1

Introduction to Landscapes and Landforms of the Maltese Islands Ritienne Gauci and John A. Schembri

Lil din l-art ħelwa, l-Omm li tatna isimha, Ħares, Mulej, kif dejjem Int ħarist: Ftakar li lilha bil-oħla dawl libbist. To this sweet land, the Mother whose name we bear, Look after it, O Lord, as Thou hast always done: Remember Thou hast dressed her with the brightest light. Dun Karm Psaila - Malta’s National Poet, 1922. Innu Malti (National Anthem of Malta) Verses 1–3.

Abstract

The Maltese Islands consist of an archipelago of three main islands—Malta, Gozo and Comino—and a group of islets. Centrally located in the Mediterranean Sea over a surface area of 316 km2, they have long represented a landscape reality which trascends their size and encompass the evolving dynamics of the Mediterranean region in terms of its geology, geomorphology and long history of human interactions with the physical environment. The small geographical setting of the Maltese Islands helped to closely connect these landscapes with Maltese society and, as exemplified in the islands' literary and cartographic heritage, landforms acted as important backdrops of Maltese cultural identity. The chapter highlights how this volume is the result of a strong collaborative spirit between local and foreign researchers, nurtured for decades within the Department of Geography of the Faculty of Arts at the University of Malta. Keyword





Island Geomorphology Islandscape Maltese Islands Mediterranean




Geography




R. Gauci (&)
J. A. Schembri Department of Geography, University of Malta, Tal-Qroqq, Msida, MSD 2080, Malta e-mail: [email protected] J. A. Schembri e-mail: [email protected] © Springer Nature Switzerland AG 2019 R. Gauci and J. A. Schembri (eds.), Landscapes and Landforms of the Maltese Islands, World Geomorphological Landscapes, https://doi.org/10.1007/978-3-030-15456-1_1

1.1

Introduction

The study of geomorphology, geography and islands enjoy, on their own terms, a wide fora of international recognition. This volume represents a unifying account of these three fields of study, weaved together in what we trust is a coherent compilation of scholarly contributions about the geomorphological landscapes of the Maltese Islands.1 Island geomorphology is best understood when the study of landscape realities which govern such small territories extends beyond their land borders and geographic size. The conventional notion of islands being remote and isolated cannot be further away from the truth for the Maltese Islands. These islands have nurtured their own insular identity, expressed in their cultural milieu, ecological refugia and linguistic characteristics; but the evolution of both their landforms and the long history of human interactions with the physical landscape bears witness to a wide and deeply connected journey, carried out in tandem with the story of the Mediterranean region.

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The Maltese Islands is an archipelago of three main islands, MALTA, GOZO and COMINO, and a number of islets. The name of the country is MALTA. In this volume, in order to maintain a clear distinction, the terms ‘Maltese Islands’ and ‘Malta’ are used, respectively, to refer to the archipelago and its largest island. 1

2

R. Gauci and J. A. Schembri

The structure of the islands is the result of active tectonic processes that shaped the central Mediterranean over 23 million years ago. The lithostratigraphy originates from the marine sedimentary processes that operated in the pre-Pleistocene waters of the Mediterranean, whereas many of their palaeosoils were formed by highly dynamic fluvial deposits during the Quaternary period.

1.2

Island Geomorphology, Meaningful Landscapes

The relationship between early island settlers and their landscapes, which dates back to early Eneolithic Age (i.e. fourth millennium BC), was also the direct result of a complex network of communications between the Maltese Islands and the Mediterranean basin: mainly from Sicily and South Italy, to the south-western Balkans, the Ionian Islands and the Levant (Cultraro 2008). The influence of geology and geomorphology shaped the ways in which the Neolithic islanders inhabited the landscape and transformed their temple culture into a meaningful space which today is recognized as being of UNESCO World Heritage status. In many ways, an island can be considered both paradise and prison, both heaven and hell (Baldacchino 2006). The geomorphological landscapes of the Maltese Islands represent a similar paradox for their inhabitants: a paradox which sways from one extreme to another as geopolitical and socio-economic events unfold on the islands, in the Mediterranean region and beyond. The coast with its accessible harbours, bays and shore platforms was very much feared due to piracy before the arrival of the Knights of St John in 1530 and in the decades thereafter. With the arrival of the Knights and the subsequent strengthening of coastal military defence, the coast was transformed into a place of growing socio-economic opportunities. This led to the gradual abandonment of cavernous landscapes from the islands’ interior, which for millenia had ensured shelter and survival to troglodytic communities. Beaches and shore platforms, once considered as dangerous access points for invaders, are today highly sought-after meccas for tourists. Landslides not only display a spectacular manifestation of geomorphological processes but also represent a geo-hazard requiring monitoring, technical scrutiny and preventive care. Deep faults running through the islands have created contrasting topographies of horsts, grabens and rias with breathtaking views, deep harbours and fertile valleys. And yet, they are also a sharp reminder of the powerful presence of active tectonism in central Mediterranean. The geomophological story of the Maltese Islands is therefore a story of many bridges, which span multiple spatio-temporal dimensions. What started as an editorial

endeavour aimed to illustrate the geomorphological qualities of the Maltese Islands soon grew into a showcase of the meaningful connections between the islandscape, its landforms and society through the centuries. The blending of these themes has been resonating for centuries in traditional Maltese texts, including the first literary text ever written in the Maltese language: Il-Kantilena by Pietru Caxaro (pre-1485).2 In his twenty-verse poem, Caxaro fused the islands’ semitic-based linguistic culture with the Latin script, to create the Maltese script. The poem is the sad lament of a houseowner who witnessed his property collapse by land subsidence due to unstable geological foundations made of weak clays. The poem closes with a reflective tone on the variety of landforms, their colourful attributes and fruit-bearing blessings: Huakit by mirammiti Nizlit hi li sisen Mectatilix li mihallimin ma kitatili li gebel fen tumayt insib il gebel sib tafal morchi Huakit thi mirammiti lili zimen nibni Huec ucakit hi mirammiti vargia ibnie biddilihe inte il miken illi yeutihe Min ibidill il miken ibidil i vintura haliex liradi 'al col xibir sura hemme ard bayad v hemme ard seude et hamyra Hactar min hedann heme tred mine tamara. It (she) fell, my building, its foundations collapsed It was not the builders’ fault, but the rock gave way Where I had hoped to find rock, I found loose clay It (she) fell, my edifice, (that) which I had been building for so long, And so, my edifice subsided, and I shall have to build it up again, change the site that caused its downfall Who changes his place, changes his luck! for each (piece of land) has its own shape (features) there is white land and there is black land, and red But above all, (what) you want from it is [to bear] fruit. Il-Kantilena, Pietru Caxaro, pre-1485, Verses 11-20.

1.3

An Overview of this Volume

Following an introduction, Landscapes and Landforms of the Maltese Islands is divided into three main parts. Part I provides the background to the main geomorphological aspects responsible for the physical and geographic development of the Maltese Islands. Part II presents a selection of 22 contributions which describe the diverse geomorphological landscape of the islands. The location of the themes discussed in each contribution is illustrated in Fig. 1.1. It is worth noting how the small size of the islands 2

The poem was discovered by Prof. Godfrey Wettinger and Patri Mikiel Fsadni in 1966. The original document can be viewed at the Notarial Archives in Valletta.

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Introduction to Landscapes and Landforms of the Maltese Islands

3

Fig. 1.1 Location of selected geomorphological landscapes, indicated by volume chapter number. Source DEM map from ERDF LIDAR data (2012)

favoured the exploration of specific themes in more than one site across the archipelago. Such themes included palaeosoils, sinkholes, cart ruts, saline marshlands, freshwater rock pools and archaeological landscapes. This explains why some chapter numbers appear repetitively across the Maltese Islands in Fig. 1.1. Part III closes the volume with two important (and inter-linked) themes which determine the future of our landscapes and landforms: the regulatory framework and the concept of sustainability. Some of the themes penned in this volume have never been researched before and reflect a dynamic and emerging community of researchers who are responding to new opportunities in island geomorphology research. In March 2017, research resilience for this volume was further put to test when the Maltese Islands experienced the sudden loss of one of their most iconic landforms: the Azure Window in Gozo. The intense societal response to such a loss reaffirmed the strong significance that landforms continue to project on to Maltese society. It encouraged our resolve to build further on this theme, with an additional contribution about the loss of the Azure Window which is to be found in this volume.

The volume was produced through an international collaborative set-up of 46 contributors, led by the Department of Geography of the Faculty of Arts at the University of Malta. The Department owes its origins to a multidisciplinary programme entitled Contemporary Mediterranean Studies, in which geography was introduced within the Mediterranean Institute and subsequently within the Faculty of Arts. The study of geography evolved into a fully fledged undergraduate and postgraduate degree programme which maintained contacts with foreign departments through research and publications, the Erasmus Student and Staff Exchange programme, and cooperation in joint field studies. To date, about 500 geography graduates are contributing to the environmental, socio-economic and cultural development of Malta, a number of whom continued their postgraduate studies in British and other European universities. The Department of Geography has also been actively contributing in the International Association of Geomorphologists (IAG) as national scientific representative for the Maltese Islands. This editorial initiative, published under the

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patronage of the IAG, aimed to bring together numerous local and foreign specialists, which included 22 geographers (many with field expertise in geomorphology) but also geologists, GIS specialists, biologists, geoscientists, archaeologists and environmental lawyers. Academic staff members from another four departments and two institutes within the University of Malta have contributed to this volume, mainly from the Department of Classics and Archaeology, the Department of Geosciences, the Department of Conservation and Built Heritage, the Department of Biology, the International Institute of Baroque Studies and the Institute of Climate Change and Sustainable Development. We are extremely grateful to have received the most helpful joint contribution of the Chief Executive Officer of Environmental Resource Authority (ERA) and the Deputy Director for Environment and Resources within the same national agency. Out of 46 contributors, 19 contributors hailed from four foreign universities and two research institutes in Europe: University of Portsmouth (UK), Liverpool Hope University (UK), University of Modena and Reggio Emilia (Italy), University of Trieste (Italy), the Institute of Marine Science-CNR (Bologna) and the Research Institute for the Geo-Hydrological Protection of National Research Council (Padova). This multinational venture draws on the collaborative efforts sustained by the Department of Geography over many years, in order to establish an international Fig. 1.2 The first printed separate map of the Maltese Islands, produced by Jean Quintin d’Autun. This wood-cut map was drawn in 1533 and printed in Lyons in 1536. Source The National Library of Malta

R. Gauci and J. A. Schembri

presence in the geographical and geomorphological research community. Each chapter has undergone a rigorous process of peer review made up of experts who acted as external or independent reviewers. Central in this review process has been the precious contribution of David K. Chester (Liverpool Hope University) whose experience and thorough external review of all chapters guided the authors and substantially enhanced the quality of the manuscripts. Thanks are also due to internal reviewers Reuben Grima (University of Malta) and Angus Duncan (University of Liverpool) for generously providing their specific expertise. We remain extremely grateful for the unwavering support received from Piotr Migoń, Series Editor, who entrusted us with the editorial responsibility of this volume as part of the successful series of World Geomorphological Landscapes. Special mention is owed to Mauro Soldati, President of the International Association of Geomorphologists (IAG), for his research interests in landslide geomorphology of the Maltese Islands. The editors would like to thank Dominic Fenech, Dean of the Faculty of Arts, and Maria Attard, HoD Geography, for their ongoing support at the University of Malta. Our gratitude goes also to Candida Gerada, for her unfailing patience shown towards us in the administration work for our department.

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Introduction to Landscapes and Landforms of the Maltese Islands

We would also like to acknowledge the kind availability of Robert K. Doe, Springer Senior Publisher, in the early stages of this volume preparation and the assistance provided by Springer Book Project Coordinator, Manjula Saravanan and Springer Book Project Manager, Madanagopal Deenadayalan, in the final production stages. The final and most important merit goes to all contributors who with patient dedication and rigorous commitment to research have made possible the production of this edited volume. We feel truly honoured to have received the collaboration of such a comprehensive community of esteemed scholars, especially on the occasion of the 250th anniversary of the founding of the University of Malta.

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to draw a separate printed map of the Maltese Islands (Fig. 1.2). His description of the islands left a lasting influence on writers with numerous re-editions and translations. Across a time span of almost five centuries, we hope that this volume will become another addition which honours the pioneering work of Jean Quintin d’Autun. Acknowledgements The editors would like to thank Sephora Sammut for her help with a DEM image to complete Fig. 1.1. and the National Library of Malta for permission of reproduction of the Jean Quintin d’Autun map (1536) as Fig. 1.2.

References 1.4

Conclusion

As geographers, we wish to conclude this chapter with a short anecdote. The earliest geographical treatise on the Maltese Islands is credited to Jean Quintin d’Autun in 1536. His Insulae Melitae Descriptio Ex Commentariis Rerum Quotidianarum is the earliest surviving printed description of the islands, which he wrote during his stay from 1530 to 1536 (Vella 1991). Well versed in cosmography and prolific in writing, Quintin is also credited with having been the first

Baldacchino G (2006) Islands, Island Studies, Island Studies Journal. Island Stud J 1(1):3–18 Cultraro M (2008) Domesticating islandscapes: Sicily and the Maltese Islands in the Later Neolithic and Eneolithic Ages (IV-III millennium BC. In: Bonnano A, Militello P (eds) Interconnections in the central Mediterranean: the Maltese Islands and Sicily in history, Progetto KASA. Sapiente Antichità, Koinè Archaeological, pp 5–16 ERDF LIDAR data (2012) ERDF156 Developing National Environmental Monitoring Infrastructure and Capacity. Malta Environment and Planning Authority Vella HCR (1991) Quintinus’ Insulae Melitae Descriptio (1536) and later writers. Hyphen 6(5):197–203

Part I Background

2

The Geographical Context of the Maltese Islands John A. Schembri

Abstract

This chapter provides the background to the broad geomorphological properties of the Maltese Islands through a geographical lens. Principally it aims to provide a large-scale view of the integration of the landscape to the landform as applied to a small archipelago. The main themes identified in this endeavour are location, the broader Mediterranean environment, climate, cohesion of the island mass and the human element that occupies it.





Keywords







Maltese Islands Mediterranean Sea Clustering and cohesion Geohistorical Land use

2.1

Introduction

Geographical context is a term that refers to the human and physical characteristics of places and environments in terms and ‘parts that they can be fully understood, precede or follow a passage and fix its meaning’ (Fowler et al. 1976, p. 219). Within a physical geographical context, the natural environment is prominent whilst communications, human use and habitat make up the human environment. These five branches are not mutually exclusive but interact with one another at a range of times and spatial scales that place the context in constant evolution and change. The 1976 edition of the Concise Oxford Dictionary defines [land]scape as a ‘representation of view’ (Fowler et al. 1976) and in more detail in its use as a noun as ‘all the visible features of an area of land’ (Soanes and Stevenson 2004). The dictionary identifies the origin of the word to sixteenth-century Middle Dutch etymology where ‘land’ is combined to scap [‘scape’] to denote a specific type of J. A. Schembri (&) Department of Geography, University of Malta, Tal-Qroqq, Msida, MSD 2080, Malta e-mail: [email protected] © Springer Nature Switzerland AG 2019 R. Gauci and J. A. Schembri (eds.), Landscapes and Landforms of the Maltese Islands, World Geomorphological Landscapes, https://doi.org/10.1007/978-3-030-15456-1_2

scene, i.e. landscape (Soanes and Stevenson 2004, p. 1283). When used as a verb, it is identified with ‘improv[ing] the aesthetic appearance (by changing the contours, planting trees and shrubs, etc. of a piece of land)’ (Soanes and Stevenson 2004, p. 801). In geomorphology literature, the description of landscape as a representation of surface view resonates on other levels as well. It extends beyond the surface space and time, to include other layers in the landscape, often not seen by naked eye or across a human lifespan. Goudie and Viles (2010), for example, include the subsurface properties of the landscape (such as rocks and soils) that have underpinned the nature of landscape change for millions of years of geological history and the role of human agency, responsible for landscape change beyond just the elements of ‘landscaping’. To this end, Goudie and Viles (2010) describe landscape as a multilayered ‘palimpsest’, i.e. a spatiotemporal dimension made up of layers of physical and anthropogenic systems that operate in complex and often interconnected ways. The prime media in representing these layers and thus help in interpreting landscapes and their associated landforms were maps drawn on various media such as clay, papyrus, canvas, paper and electronically. Generally, geomorphological features influence the build-up of a layered landscape, frequently over various stages, with each layer of human endeavour either forming the basis of the subsequent layer or being buried by it. However, a palimpsest of landscapes normally identifies the sequence of occupancy of a region. As a result, maps became a representation of landforms and their associated landscape (Robinson et al. 1984; MacEachren 2004). Other considerations that help identify the geographical context are scale and resolution, or the detail to which the spatial element can be presented on the map and then appraised both from its surrounding environment and also through its inherent characteristics. Fortunately for the Maltese Islands, the mapping of the land (and waters) has a long history that dates back to the early sixteenth century (Gauci and Schembri 2019a, Chap. 1; 9

10

Gauci and Schembri 2017, 2019b). From the nineteenth century onwards, surveying and mapping have been repeated fairly regularly by the British Directorate of Overseas Surveys and recently by the French Geographical Bureau. Thus, reliable baseline cartographic representation of the land surface is readily available in Ordnance Survey sheets. These sheets give the topographic outline at 25-foot contour intervals (ca. 7.62 m), identify the main geomorphological features such as cliffs and steep slopes, indicate the names of the localities and show all built-up areas. In this chapter, following the etymological derivatives of ‘context’, and association between ‘landform’ and ‘landscape’, sections dealing with the Mediterranean region and its climate, the importance of islands and the context of the Maltese Islands themselves within the ambit of their location, geomorphology, degree of clustering and inherent cohesion will be reviewed. The setting of human endeavour and character forms the second major part of the chapter through the maritime jurisdictional areas, the sequence of successive occupiers who have used and modified the local landforms into a landscape to suit their socio-cultural and economic needs and finally contemporary land uses. The association between landforms and landscapes emerges from the broad number of elements that collectively produce the shapes and formations that make up the natural environment. Geographers and geomorphologists have

J. A. Schembri

painstakingly grouped these elements into recognisable facets known as landscapes by developing a nomenclature to ease classification and, in their association with cartographers and later photographers and satellite imagery, presented these at various scales, resolutions and hues, from different angles and levels of detail. At the academic level, observers of the landscape also parcel out sections of the environment into different geographies that make up a range of metrics such as cells, patches, strips, corridors and edges (Leitao et al. 2006). Landscape functions can have different meanings and interpretations. For example, ecologists view it as the movement of plants and animals within the complex of energies and dissolved minerals (Forman and Godron 1986; Forman 1997).

2.2

The Mediterranean and the Maltese Islands

The Maltese Islands lie in the centre of the Mediterranean geographically equidistant from either end, but with a geographic proximity to Europe which has conditioned their cultural development (Fig. 2.1). Although the isolation of the Maltese Islands within the Mediterranean can be gauged through the broad expanse of the eastern Mediterranean, its closeness to Sicily, at about 93 km, and the compactness of

Fig. 2.1 Relief map of the Mediterranean lands with main islands. Source Wikimedia Commons, Mediterranean Relief.jpg, under CCO Public Domain

2

The Geographical Context of the Maltese Islands

the western Mediterranean marginally decreased this isolation. The Mediterranean Sea itself is 3600 km in length from the Straits of Gibraltar in the west to the Lebanese shores in the east and has an area of about 2.5 million km2. The comparative north–south distance between the continent of Africa and Europe is 1600 km if measured from the Gulf of Sirte to the North Adriatic. Of the two basins, the western basin is one third the size of the whole sea. The remaining two thirds constitute the eastern basin and comprise the broad Central and Ionian seas. The flushing of the Mediterranean waters from the Atlantic, although taking a century to circulate around, is aided by the narrow straits throughout the sea basin, upwelling of deep water currents and river water flow from the Nile and other rivers and practically throughout the northern lands. However, despite high solar radiation and evaporation, the waters maintain a salinity of 36–38‰. The high salinity and the warm weather in summer are ideal conditions for the production of sea salt. The air masses that influence the Mediterranean in general affect the climate of the Maltese Islands in particular. The Continental Tropical Air Mass that originates in Africa is associated with a dry, warm atmosphere and is generally responsible for giving the long-term stability associated with the summer months providing calm waters and clear skies. However, the passage of dry air from the desert over the Mediterranean waters increases the humidity levels on the islands and produces the notorious hot and humid summer environment. The Maritime Tropical Air Mass traces its origins from the mid-Atlantic Ocean and contains a substantial amount of humidity before it reaches the Mediterranean. However, it is these two air masses that allow for the warm temperatures experienced on the islands. The two other principal air masses that originate from the northern

Table 2.1 Area of selected Mediterranean islands and archipelagos. Source List of rock islets compiled from Sciberras and Sciberras (2010)

Islands and archipelagos

11

areas are the dry Continental Polar Air Mass from mainland Asia and the Maritime Polar Air Mass from the North Atlantic. Both air masses reach into the central Mediterranean especially during the winter and spring seasons, cooling the temperatures and augmenting the autumn rainfall. Of particular importance is the Mediterranean Front that results from the confluence of the warm and cold air masses. This brings flash floods typical of early autumn and encourages soil erosion and gullying. The interplay of these air masses conditions the average range of temperatures for the whole Mediterranean as being between 6.1 and 10.0 °C in winter with high temperatures in summer ranging between a coastal 23.9 and 32.2 °C inland (Branigan and Jarrett 1975).

2.3

Islands

As indicated above, the Mediterranean has numerous islands, about 3000, of various sizes, with the Aegean and Adriatic seas having a large number of small islands whilst the larger islands are to be found in both the western and eastern basins. Table 2.1 shows the names and respective areas of principal Mediterranean islands shown in order of size. Of particular importance, only Cyprus and Malta were British colonies, with independence granted in 1960 and 1964, respectively.

2.4

Location

The location of the Maltese Islands (35° 55′ 4.7028″N and 14° 24′ 35.7948″E) is positioned in the Sicilian channel that connects the eastern and western basins of the Mediterranean

Area in km2

Aegean Islands

25,610

Sicily

25,460

Sardinia

23,813

Cyprus

9,251

Corsica

8,618

Crete

8,261

Balearic Islands

5,014

Euboea

3,655

Rhodes

1,398

Corfu

592

Djerba

510

Maltese Islands

316

Elba

223

12

J. A. Schembri

Fig. 2.2 Bathymetric map of the Mediterranean with main straits. Source Ikonact, Wikimedia Commons, under CC BY-SA 4.0 for Mediterranean Sea Bathymetry map; Regional sea entities redrawn from Kuwabara (1984)

and gave them a geostrategic value far greater than their size. This situation is similar to a number of islands and archipelagos that command waterways or narrow channels, thus holding a position that influences wider areas or possess a significant political clout irrespective of their small size. Other locations from the Mediterranean include the Straits of Gibraltar and the Suez Canal (Fig. 2.2). Within the wider Middle East, one finds the Turkish Straits, the Gulf of Aqaba, Bab el Mandeb and the Straits of Hormuz, and within the broader global geopolitical scenarios, the Straits of Malacca (Drysdale and Blake 1985). As a result of their geographies, the lands bordering these waterways attract attention from the broader socio-economic and cultural factors of other lands and, consequently, their landscapes and the way their landforms influenced the spatial distribution of land uses together with their changes over time that modified their landscape. The utilisation of the landscape in the Maltese Islands and its change over time is partly the result of their strategic importance due to the attraction afforded by successive political and cultural entities that sought to control the central Mediterranean. The islands are essentially a central Mediterranean continental archipelago, being the emerged remnant of the post-Miocene Pantelleria Graben system and trending NW–SE along the Pantelleria Rift system (Galea 2019, Chap. 3). As an island group, they are clustered over a 45 km length at 90 km from Sicily and 290 km from the North African coast. The islands consist of three main inhabited islands, with Malta at 27.3 km in length and 14.5 km in width, Gozo at 14 km by 7.5 km and Comino at

2.5 km by 1.5 km, and a number of islets, skerries1, and groups of rocks and boulders some of which are at a significant distance from the shoreline. Table 2.2 shows a list of these islands with their relevant areas in addition to other rock outcrops located around the 200-km coastline. As a result, the coastal landscape at least provides a visual treat where islets and outcropping rocks dot the coastline.

2.5

Clustering and Cohesion

One basic physical characteristic of the Maltese Islands is their lack of significant fragmentation as they are clustered over a relatively short distance (of 45 km). The length of the channels between the two main islands at 5 km provides fairly quick communications that also assisted in the political and administrative integration of the smaller island of Gozo into the larger one of Malta. The ferry crossing between the islands promotes a particular landscape value, with views of Comino and the approaches to the picturesque Mġarr Harbour on Gozo. However, as a separate island, Gozo allows for a more pristine environment given its lack of urban and industrial development and as a consequence enhances the collective landscape value of all the islands. Its promotional tag of ‘sister island’ gives connotations of pleasant, calm and

1

A skerry (plur. skerries) is a low, rugged rocky reef or scatter of reefs, situated off a hard rocky coast. They are generally intertidal but may sometimes extend above high tide level (Goudie 2014).

2

The Geographical Context of the Maltese Islands

Table 2.2 The Maltese Islands: main islands, islets and other rock islets. Source List of rock islets compiled from Sciberras and Sciberras (2010)

13

Name of main islands and islets

Area (km2)

Malta

245.8

Gozo

67.1

Comino

2.8

Manoel Island

0.3

St Paul’s Islands

0.1

Cominotto

0.1

Filfla

0.02 (2 ha)

Other rock islets Ħalfa Rock, Old Battery’s Rock, Lantern Point Rock, Large Blue Lagoon Rock, Small Blue Lagoon Rocks, Devil’s End Rock, Għallis Rocks, Taċ-Ċawl Rocks, Cheirolopus Rock, Barbaġanni Rock, Crocodile Rock & Bear Rocks, (Orsijiet), Qawra Point, Comino Cliff Face Rock, Xrobb l-Għaġin Rock, Fessej Rock, Għemieri Rocks, Ħnejja Rocks, White Rocks, Blue Islets (Rocks)

female dimensions that augment the archipelago’s landscape ‘act’. The smaller islands, formed as a result of local tectonic forces, provide an additional landscape value that is today judged by the lack of easy accessibility, as in the case of St Paul’s Islands (Sammut et al. 2019, Chap. 26) and Filfla (Furlani et al. 2019, Chap. 21) and coastal rural psychological remoteness in the case of Comino and Cominotto. However, the channel between these two latter islands, popularly known as ‘Blue Lagoon’, is a very popular spot for yacht mooring and swimming in summer, its landscape value enhanced by the pristine blue nature of the waters in the channel. On the other hand, in the case of Manoel Island, although connected by a short land bridge and located within one of the two main harbours, and separated naturally as a result of marine invasion, its former use in housing a quarantine and infectious diseases hospital accounts for its ‘remoteness’ in local psyche. The spread of rocks located around other parts of the islands are generally smaller in size, with most of them just fragments of Upper Coralline

Table 2.3 Stratigraphic data of the Maltese Islands in terms of maximum thickness, percentage surface area and coastal length for each formation and resultant landforms. Source Compiled from Zammit-Maempel (1977), Schembri (2003)

Limestone outcrops some metres off the shoreline from where they were cut off as a result of weak geological strata and faults. The larger fragments such as Il-Ġebla tal-Ħalfa and Il-Ġebla tal-Ġeneral are cases in point, whilst it-Taqtiegħa ta’ Delimara and Xrobb l-Għaġin Rock, fragments of Globigerina Limestone, are all the result of tectonic forces that isolated them from the main islands. The landscape value of these outcrops is appreciated through touristic promotional material and local folklore associated with them. Some of these rocks are popular dive sites. In addition to the smallness of the islands, the undulating landscape, represented by almost one-half of the surface area of Malta, as a percentage surface area of Globigerina Limestone (Table 2.3), has traditionally sited the main towns, villages and road networks. About eighty per cent of the population lives, works and commutes in this area south of the Great Fault (Gauci and Scerri 2019, Chap. 5). This situation compacts the main socio-economic functions of the main island of Malta into even smaller areas. Table 2.4 identifies the soft geological formation of Globigerina

Upper Coralline Limestone

Greensand/Blue Clay

Globigerina Limestone

Lower Coralline Limestone

Maximum thickness below surface (m)

160

70

25–200

140

Percentage surface area outcropping (Malta)a

22.6

12.3

44.5

20.6

Percentage of coastal lengthb

16.4

9.4

35.1

36.0

Main geomorphological features

Low sloping rock/rdum

Beach/rdum/talus

Low sloping rock/shore platform

Plunging cliff, shore platform

a

Estimated by author Measured on 1:25,000 scale maps at 25 m intercept intervals. The remainder 3.1% is covered by beaches and other coastal deposits

b

14

J. A. Schembri

Table 2.4 Maltese Islands shoreline geology: percentage distribution of shoreline rock type of the Maltese Islands, Malta, Gozo and Cominoa

Category

Maltese Islands

Malta

Gozo

Comino

Alluvium

0.9

1.3

–

–

Sand

2.2

1.9

2.6

0.2

Lower Coralline Limestone

16.4

15.3

1.5

99.8

Greensand/Blue Clay

9.4

8.6

14.2

–

Upper Globigerina Limestone

8.4

6.0

17.8

–

Middle Globigerina Limestone

7.7

10.7

–

–

Lower Globigerina Limestone

19.0

25.8

2.1

–

Lower Coralline Limestone

36.0

30.4

61.8

–

a

Author’s calculation presented in synoptic form compiled from 1:2500 scale sheets measured using 1 cm divider width

Table 2.5 Marine jurisdiction of the Maltese Islands with linear dimensions in nautical miles, kilometres and statute miles together with areal extent of each zone

a

Type

Linear extent (offshore)

Area (km2)

Notes

Territorial sea

12 nmi (22.2 km; 13.8 mi)

4440a

A belt of coastal waters from the baseline (usually the mean low-water mark) of a coastal state

Contiguous zone

24 nmi (44.4 km; 27.6 mi)

8880a

A maritime zone adjacent to the territorial sea that may not extend beyond 24 nautical miles from the baselines from which the breadth of the territorial sea is measured

Continental shelf

200 m depth

Fisheries management zone

25 nmi (46.3 km; 28.8 mi)

The area of seabed around a large land mass where the sea is relatively shallow compared with the open ocean. The continental shelf is geologically part of the continental crust. Much of the shelves were exposed during glacial and interglacial periods 9,260a/12,000

Previously called the exclusive fishing zone

Exclusive economic zone

55,556/69,000

2% of the Mediterranean

Search and rescue area

250,000

10% of the Mediterranean

Estimate based on a 200-km coastline length

Limestone at a quarter of the coastal length. The latter formation provides easy access due to its overall low sloping topography and shore platforms, especially around the three harbours. One particular geographic property that small islands possess is the ease of connecting all the points along the perimeter to each other. Besides, this property can be applied to all peripheral zones due, in part, to the smallness of the islands. It can also be identified in connections with the interior of the land, especially in areas where the flat topography permits easy communications. Traversal was the main factor used by the Knights of St John to erect a series of coastal watch towers for defensive purposes. The ease of

circumnavigating the islands was another factor that contributed to maintaining cohesion. Besides the relative short span to navigate around, the presence of an indented coast with a number of inlets, bays and harbours affording shelter was a principal attribute to seamen.

2.6

Maritime Jurisdiction

The main theme of this book is the landscape; therefore, the introduction deals with the overall physical features as they condition the landscape, essentially the solid surface of the land. However, the marine area especially deserves attention

2

The Geographical Context of the Maltese Islands

both to enhance the island nature of the Maltese archipelago and to do justice to the medium that shapes the character of the islands. The spatial extent of the Maltese maritime jurisdiction expands over the adjacent waters of the Mediterranean with a series of zones over which the legal framework of international law operates. Table 2.5 identifies these zones and areas, giving also their respective dimensions.

2.7

The Maltese Landscape: A Brief Geohistorical Overview

Earliest accounts attributed to visitors to Malta over the last centuries all refer to predominantly a rocky, stony and arid landscape. These include Jean Quintin d’Autun who visited Malta in 1536 (Vella 1980), Camillo Spreti, a Knight of St John (1764), who provided an overall view of Malta, and Lord Byron with his poetic account of “ye cursed streets of stairs”, in his poem ‘Farewell To Malta’, when describing the stepped inclines of the typical urban environment of Valletta in 1811. The local landscape was affected by persistent urbanisation especially over the last half-century and, in parallel, the change and growth of the local economy (Harrison and Hubbard 1945; Morris 1952). Further considerations regarding the local landscape and the problems associated with the semi-arid environment are provided by successive British colonial and Maltese government reports to enhance the landscape and also essentially change the economy from one dependent on spending by the British Armed Services and primary and secondary industries to tertiary ones. Notable reports, studies and papers are in chronological order: Harrison and Hubbard (1945); Morris (1952); Blouet (1965), Robens (1967); Brincat (2009) and Grech (2015). In addition, successive five-year and seven-year plans were presented in order to boost the economy, the annual budgetary allocations and indirectly, to safeguard the landscape. However, the fragility of the coast was at least identified by Europa Nostra through a local conference, with the proceedings published by the forerunner of local environmental and heritage organisations (Agius-Muscat 1968).

2.8

Land Use

Land constitutes about 30% of the earth’s surface and is essential to the sustenance of life (Clark 1995), with a limited carrying capacity (Yunlong 1990) and is basic to all aspects of development (Okpala 1982). Malta, with over

15

1300 persons per km2, is the country with the highest population density in Europe and one of the highest in the world. The situation in Malta can best be summarised from data showing that only 4.1% of the land was built up in 1910 (Cilia 1995), with this figure rising to about a third of the land surface by 2012 (European Commission 2012). This involved the extension of the residential areas, especially around the harbours, the growth of other towns and villages and the needs of industry with a number of industrial estates around the periphery of the harbours and at a distance from urban areas. A network of connecting roads to accommodate the growing number of vehicles further absorbed rural areas. In addition, the development of tourism and allied activities, both along the coast and inland, occupied more land, including shore platforms (Gauci and Inkpen 2019, Chap. 27), low sloping shorelines and at times even areas where land subsidence and instability were apparent. Parallel to this land use development, the demographic situation of the islands also saw a huge increase in the population from 184,742 enumerated in the 1901 census to 475,701 for 2017 (National Statistics Office 2019). The latter figure includes about 14.1% foreigners (67,145) engaged in various economic activities hailing from Western and Eastern Europe, mainly EU countries, North and sub-Saharan Africa and the Far East. Other immigrants occupy prestigious residential blocks along selected seafront properties and mark out the top range of property development in Malta. Following the building of Valletta, the urban population around the harbours swelled and a large number of small villages and hamlets were abandoned in preference to finding residence within the walls of the harbour fortifications (Schembri and Spiteri 2019, Chap. 6). The arrival of the British saw the enhancement of coastal and inland defences and, with the opening of the Suez Canal in 1869, Malta with excellent deep and all-weather ports became an important link in the chain that connected different parts of the British Empire. This situation caused the population to swell even further, and land used for military garrison and residential purposes increased. As a result of economic decline immediately after each of both World Wars, mass emigration to English-speaking countries occurred, with the overall population remaining static or declining. With changes affecting the general economy and the attention given to touristic development and manufacturing industry in textiles and leather, the emigration flow was stemmed and Malta replaced its dependence on British military spending with diversification of its industrial base. As a result, the span of urban development encroached further on to the rural and coastal areas. More recently, with

16

J. A. Schembri

membership of the European Union, further diversification occurred with the intensification of the tourist product, financial and call centres and e-gaming, to name a few changes based on IT technology. Although these initiatives require more urban space, it is the high-rise buildings that are now affecting the visual aspect of the landscape.

2.9

Conclusion

Geographers and geomorphologists have persistently attempted to interpret landscapes and landforms. Within the milieu of a small, clustered archipelago such as the Maltese Islands at the crossroads of the central Mediterranean, interpretation ranged from maps, reports and the physical overlap between various marks left by successive occupiers of the land. For the Maltese Islands, this has been a typical case where as a general view the landform has encouraged the overall emergence of a landscape affected by the central Mediterranean location, their lack of fragmentation, effective cohesion and excellent ports and harbours on the eastern seaboard of the larger island.

References Blouet BW (1965) Malta’s first five-year development plan 1959–64. Geography 50(1):73–75 Branigan JJ, Jarrett HR (1975) The Mediterranean Lands, 2nd edn. Macdonald and Evans Ltd London, 609p Brincat M (2009) The birth of the ‘Maltese Model’ of development 1945–1959. J Maltese Hist 1(2):34–52 Cilia G (1995) Sustainable development:land use in Malta. Friends of the Earth - Malta. Mimeo Report 32p Clark JR (1995) Coastal zone management handbook. New York, Lewis Publishers 694p Drysdale A, Blake GH (1985) The Middle East and North Africa: A Political Geography. Oxford University Press, New York, 380p European Commission, Eurostat (2012) LUCAS - Land Survey and Land Cover Survey. Available at: https://ec.europa.eu/eurostat/web/ lucas/data/primary-data/2012. Last accessed 2nd Apr 2019 Forman R (1997) Land mosaics: the ecology of landscapes and regions. Cambridge University Press, Cambridge, 656p Forman RTT, Godron M (1986) Landscape ecology. John Wiley and Sons, New York, 619p Furlani S, Gauci R, Devoto S, Schembri JA (2019a) Filfla: a case study of the effect of target practice on coastal landforms. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 261–271 Fowler HW, Fowler FG, Sykes JB (eds) (1976) The concise Oxford dictionary of current English (new edition): based on The Oxford English dictionary and its supplements. Oxford University Press, Oxford, 1368p

Galea P (2019) Central Mediterranean tectonics—a key player in the geomorphology of the Maltese Islands. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 19–30 Gauci R, Inkpen R (2019) The physical characteristics of limestone shore platforms on the Maltese Islands and their neglected contribution to coastal land use development In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 343–356 Gauci R, Scerri S (2019) A synthesis of different geomorphological landscapes on the Maltese Islands. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 49–65 Gauci R, Schembri JA (2017) From outcrops to maps: the birth of geological maps of the Maltese Islands in the 19th century - Part I. Malta Map Soc J 1(2):16–26 Gauci R, Schembri JA (2019a) An introduction to Landscapes and Landforms of the Maltese Islands In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 1–5 Gauci R, Schembri JA (2019b) From outcrops to maps: the birth of geological maps of the Maltese Islands in the 19th century - Part 2. Malta Map Soc J 1(4):48–47 Goudie A (2014) Alphabetical glossary of geomorphology, Version 1.0. International Association of Geomorphologists, 84p Goudie A, Viles H (2010) Landscapes and geomorphology: a very short introduction, vol. 240. Oxford University Press, 152p Grech AG (2015) The evolution of the Maltese economy since Independence. Central Bank of Malta, Valletta, 39p Harrison ASB, Hubbard RPS (1945) Valletta: a report to accompany the outline plan for the region of Valletta and the Three Cities. Government of Malta, Valletta, 109p Kuwabara S (1984) The legal regime of the protection of Mediterranean against pollution from land based sources. Tycooly Publishing International Limited, Dublin, pp 5–19 Leitao AB, Miller J, Ahren J and McGarigal K (2006) Measuring landscapes: a planner's handbook. Island Press, Washington, 245p MacEachren AM (2004) How maps work: representation, visualisation, and design. The Guildford Press, New York, 526p Morris TO (1952) The water supply resources of Malta. Government of Malta, 125p Muscat AA (ed) (1968) Malta and Europe: the defence of the coast. Din l-Art Ħelwa, Malta, 93p National Statistics Offfice (2019) Regional Statistics Malta 2019 Edition. Valletta, 158p Okpala DCI (1982) The Nigerian land-use decree revisited. Habitat Int 6(5–6):573–584 Robens A (1967) Report of the Joint Mission for Malta. Department of Information, Malta, 903p Robinson AH, Sale RD, Morrison JL, Muehrcke PC (1984) Elements of cartography, 5th edn. John Wiley and Sons, New York, 541p Sammut S, Gauci R, Inkpen R, Lewis JJ, Gibson A (2019) Selmun: a coastal limestone landscape enriched by scenic landforms, conservation status and religious significance. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 325–341 Schembri JA (2003) Coastal land use in the Maltese Islands: a description and appraisal. Unpublished PhD thesis, University of Durham 394p

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The Geographical Context of the Maltese Islands

Schembri JA, Spiteri SC (2019) By gentlemen for gentlemen—Ria coastal landforms and the fortified imprints of Valletta and its harbours. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 69–78 Sciberras J, Sciberras A (2010) Topography and Flora of the Satellite Islets surrounding the Maltese Archipelago. Cent Mediterr Nat 5 (2):31–42 Soanes C, Stevenson A (eds) (2004) Concise Oxford English dictionary: book and CD-Rom, 11th edn. Oxford University Press, Oxford, 1682p

17 Spreti C (1764) Description of the Island of Malta and a Brief Treatise on Knightly Behaviour. Published by The Order of St. John of Jerusalem, Printing Press S. Austen, Historical Pamphlets No 10, London (1949), 40p Vella HCR (1980) The earliest description of Malta, Lyons 1536 by Jean Quintin d’Autun. Interprint Ltd, Malta, 102p Yunlong C (1990) Land use management in PR China:problems and strategies. Land Use Policy 7:337–351 Zammit-Maempel G (1977) An outline of Maltese geology and guide to the geology hall of the national museum of natural history, Mdina. Malta, Malta, 44p

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Central Mediterranean Tectonics—A Key Player in the Geomorphology of the Maltese Islands Pauline Galea

Abstract

Spectacular landforms, both coastal and inland, on the Maltese Islands, are directly related to mainly vertical tectonic movements that mostly occurred within the past 10 million years. These movements form part of complex geodynamical processes that have shaped the Central Mediterranean and are still active today. A simple stratigraphic sequence of limestones and marls, that emerged above sea level around 10 million years ago (mya), has been intensely faulted, tilted, weathered and sculpted over these periods, with differing lithostratigraphic properties giving rise to a large variety of landforms, making the Maltese Islands a natural and easily accessible laboratory for studying neotectonic processes and the resulting geomorphology. Keywords




Central Mediterranean stress fields Faulting

3.1





Maltese Islands Landforms




Regional

Introduction

The geomorphology of the Maltese Islands has been shaped by two major elements: regional tectonics of the past 30 million years and sedimentary geology. The latter plays a fundamental role in guiding differential erosion and the sculpting of characteristic landforms (Scerri 2019, Chap. 4). The former is, however, the reason why the islands exist at all and has provided the first rough topographical shape of the archipelago, on which the finer details were later (or sometimes contemporaneously) sculpted.

P. Galea (&) Department of Geosciences, University of Malta, Tal-Qroqq, Msida, MSD 2080, Malta e-mail: [email protected] © Springer Nature Switzerland AG 2019 R. Gauci and J. A. Schembri (eds.), Landscapes and Landforms of the Maltese Islands, World Geomorphological Landscapes, https://doi.org/10.1007/978-3-030-15456-1_3

At the time when Africa was still part of the supercontinent of Pangaea (up until 200 million years ago), the crust which today underlies the Maltese Islands formed part of the northern African continental margin—the Pelagian Spur. As Africa separated from South America to form the southern Atlantic Ocean, it rotated anticlockwise towards Europe, while when Europe started to separate from North America about 100 mya, a relative right-lateral motion between Europe and Africa set in. The Mediterranean region, which went on to take shape in between these two large continental plates, subsequently underwent huge stresses, fracturing and displacement of continental crustal blocks (Pedley et al. 2002). The rocks of the Maltese Islands were formed as a Late Oligocene—Miocene marine depositional sequence in the midst of a complex reorganization of plate boundaries, plate motions and stress regimes taking place in the Mediterranean during the Tertiary (Illies 1981; Reuther 1984; Biju-duval et al. 1977; Dewey et al. 1989; Faccenna et al. 2001; Carminati and Doglioni 2004; Scerri 2019, Chap. 4). The Central Mediterranean is situated in the broadly convergent setting of the African plate pushing north-westwards relative to the Eurasian plate, with part of the plate boundary presently running through Sicily about 200 km north of the Maltese Islands. The present rate of convergence is relatively slow, averaging less than 1 cm per year (Catalano et al. 2008). However, the present position of the plate boundary appears to represent the last stages of a large-scale and rapid process of subduction rollback, which has probably been the most influential process affecting the Western and Central Mediterranean during the past 30 million years (Fig. 3.1). Rollback is the process by which the subduction front of the African plate beneath the European plate has moved backwards from the position of today’s Iberian Peninsula to the present-day tightly curved Calabrian Arc. This process is calculated to have progressed at an average rate of a few cm per year (Faccenna et al. 2001). One effect of this retreat was to bring about stretching of the overlying crust and the subsequent opening of two basins in the Western Mediterranean: first the Provencal Basin and later the Tyrrhenian 19

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Basin with its associated volcanism. Faccenna et al. (2001) list four main phases of this process: 80–30 mya, during which the westward subduction of the African plate and back-arc extension was initiated; 30–16 million years ago when first rifting and later ocean crust belonging to the Liguro-Provencal Basin appeared, accompanied by the anticlockwise rotation of the Sardinia–Corsica–Calabria block and eastward migration of the trench system; 16– 10 mya, characterised by very slow surface processes and continuation of subduction and 10 million years ago–present, during which accelerated extension and opening of the Tyrrhenian Basin took place, accompanied by the detachment and rotation of the Calabria block and the continued deformation of the subduction front into the present Calabrian Arc. The subduction process in this region is believed to have slowed down considerably at present, although the presence of earthquakes down to 700 km depth in the Tyrrhenian Basin, together with tomographic imaging, indicates a still-active Benioff zone and a cold lithospheric slab dipping north-westward at about 70° and levelling off to a horizontal configuration at about 600 km depth (Faccenna et al. 2001).

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The constant shifting of processes and boundaries has resulted in dramatic changes of the regional stress field in the Central Mediterranean and, in particular, in the Sicily Channel (Illies 1981). This influenced the Maltese Islands which were being gradually laid down at the time as mostly marine sediments at the bottom of a shallow sea covering the Pelagian Spur of the African continental shelf. These stress fields and their changes have resulted in the dramatic fault-controlled topography of the archipelago.

3.2

Geotectonics of the Central Mediterranean

3.2.1 Rifting in the Sicily Channel Geologically, the Maltese Islands are considered to form part of the African continental margin. The Pelagian platform on which they lie extends from the south-east corner of Sicily (Ragusa Plateau) to the Tripolitanian and eastern Tunisian margins. It consists of a thick sequence of Mesozoic– Cenozoic carbonate sediments lying over a continental crust

Fig. 3.1 Present-day tectonic configuration in the Western and Eastern Mediterranean. Source After Pedley et al. (2002)

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basement. The Maltese Islands represent an emerged part of this platform consisting of limestones and marls of Oligocene–Miocene age. Apart from the extensional faulting mostly active since the Miocene, the Pelagian platform is a relatively stable block, bordered on the east by the steeply dipping and spectacular Sicily–Malta escarpment, where the sea depth increases sharply to around 3000 m in the Ionian Basin. To the west, it is bordered by the Sicilian–Maghrebian thrust front. Starting in the Miocene Period, the Sicily Channel was subjected to extensional strains that resulted in two, almost orthogonal, rifting systems (Fig. 3.2). These

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affected the newly deposited and later consolidated sediments of the islands, with an onshore expression in the form of steeply dipping faults, block faulted landscapes and interesting interplay between two generations of faulting. The first extensional regime affecting the islands came into effect during the early Miocene (23–16 mya) with the development of NE-SW trending fractures that grew into a spectacular block faulting system and produced the horst-and-graben topography characterizing South Gozo, the Comino Channel and the north-west of Malta. This extensional regime was caused by a regional stress field having a

Fig. 3.2 Major fault lines crossing the Maltese Islands. The Victoria Lines Fault (alternatively known as the Great Fault) and the South Gozo Fault bound the main region of block faulting in the central archipelago. Source After Reuther (1984)

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horizontal minimum stress component in a 140°–160° direction. As shown by the clearly shifted layer sequences in various parts of the archipelago, the main vertical displacements of the block faulting system took place after the deposition of the Upper Coralline Limestone formation, the youngest marine sedimentary layer making up the islands (Scerri 2019, Chap. 4). A gradual decrease in the thickness of the Lower Globigerina Limestone formation near the central part of the archipelago implies that rifting may have been preceded by an uparching of the crust and structural shoulder upwarping, evident as the high points on each side of the block faulting (Illies 1981). The two onshore master faults bounding the block-fault system are the Great Fault (also known as the Victoria Lines Fault), crossing Malta from Madliena on the north coast to Fomm ir-Riħ Bay on the southern coast (Sammut 2019, Chap. 16), and the South Gozo Fault in southern Gozo (Gauci and Scerri 2019, Chap. 5). In between these two boundaries, separated by about 15 km, the whole region has foundered by means of a series of relative vertical movements along steep or sub-vertical faults. This has produced the North and South Comino Channels separating the island of Comino from South Gozo and North Malta, and with Comino being made up entirely of Upper Coralline Limestone (Fig. 3.3a, b). Similarly, the north-western region of Malta is characterised by a series of ridges and low-lying flat-floored valleys, the latter meeting the coastline to produce a number of sandy or rocky beaches and bays. The vertical throw on the Great Fault increases from 90 m in the east to about 120 m at its western end, whereas the South Gozo Fault has a vertical throw of around 100 m. It is likely that any downdip movement along these faults has now ceased, although the complex South Gozo Fault is said to have been reactivated into a dextral shear fault by a later extensional stress regime, as is described below. The idea that such faulting may still be active is corroborated by the occasional microearthquakes close to the island of Gozo, and presumably along the offshore extension of this fault complex, that are measured by a seismic network on the archipelago. This fault reactivation into a shear fault has apparently extended also to the fault on the north-western tip of Malta which forms the southern flank of the South Comino Channel. The second fault system is associated with extension in the Sicily Channel in an approximately NE-SW direction, roughly orthogonal to the previous direction. Dart et al. (1993) describe the two rifting systems as approximately coeval, reaching their maximum faulting activity in the Pliocene. The NE–SW-directed extension led to an incipient rift system, accompanied by uparching of the seafloor as well as magmatic activity, evident in the volcanic centres of Pantelleria and Linosa. The resulting sea floor topography is characterised by a series of deep, elongated basins between Sicily and Tunisia, filled with a thick Plio-Quaternary

P. Galea

sequence of sediments, and trending roughly 120° (Fig. 3.4). Collectively, this extensional system is variously known as the Pantelleria Rift, Strait of Sicily Rift Zone or Sicily Channel Rift Zone (SCRZ). The latter term is used in this chapter. The three main basins, or grabens, making up the system are the Pantelleria graben, the Linosa graben and the Malta graben. Sea depths exceeding 1500 m have been recorded in the centres of the grabens, which are infilled with rift-synchronous and post-rift marine sediments more than 400 m thick (Jongsma et al. 1985). Heat flow measurements over the grabens indicate values consistent with young rift regions (Cello 1987). The Malta graben passes very close to the southern coastline of Malta, about 15 km to the south. Bathymetric and seismic reflection studies have revealed that the grabens have steep sides, which are themselves normal faults, along which rapid vertical subsidence occurred reaching its peak during the Quaternary. Activity along the graben sides is apparently still ongoing, and GPS measurements show a relative displacement between the islands of Malta and Lampedusa, indicating ongoing crustal extension (Catalano et al. 2008).

3.2.2 Mechanisms of Rifting A spate of studies and publications concerning the Sicily Channel Rift Zone, proposing models and mechanisms for its formation and ongoing development appeared in the 1980s and early 1990s. In spite of the numerous hypotheses about the nature of the grabens and related geodynamical processes, the primary mechanisms behind the SCRZ are still under debate. In particular, an interesting question is whether the rifting is active or passive. The former involves mantle updoming and volcanism followed by extension and subsidence, whereas the latter is initiated by fault-controlled stretching and crustal thinning, followed by mantle intrusion and volcanism. In any case, an underlying concept that is common to practically all models is that two diverse geodynamic processes are simultaneously active in the present day, i.e. that of a Central Mediterranean region where extensional processes are orthogonal to and superimposed on a broadly compressional regime representing the convergence of Africa towards Europe (Corti et al. 2006; Reuther and Eisbacher 1985). In situ stress measurements on Malta, Sicily and Lampedusa reveal a consistent NE–SW direction for the minimum horizontal shear, corroborating the model of crustal stretching in that direction (Grasso et al. 1986). To explain the actual formation of the grabens, most models invoke the presence of a wide area of dextral shear, which accommodates the oblique component of the Africa– Europe convergence and is related to recent extensional tectonics. A popular explanation of the graben formation is that they are pull-apart grabens formed between staggered,

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Central Mediterranean Tectonics …

Fig. 3.3 a Cartoon showing the topographical effect of block faulting (after Pedley et al. 2002); b A labelled Google Earth view of the block faulted region in the centre of the archipelago and a simplified

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representation of the South Gozo and Great Fault. Source After Pedley et al. (2002) Google Earth Image© 2016 Terra Metrics

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P. Galea

Fig. 3.4 Bathymetry of the Central Mediterranean region, showing the grabens created by the Sicily Channel Rift, and the Malta Escarpment. Source After Pedley et al. (2002)

approximately east–west-oriented dextral strike-slip faults (Grasso et al. 1986; Cello 1987; Reuther 1990). A small, similarly formed pull-apart basin lies just off the north-west tip of Gozo, the North Gozo Basin (Gardiner et al. 1995). It is bounded by approximately east–west trending dextral strike-slip faults. On the other hand, a number of north-south-oriented sinistral strike-slip faults are believed to act as transform faults along which extension is taking place (Reuther et al. 1993). The Scicli Line, extending from Ragusa to the coast of southern Sicily and presumably south towards the Maltese archipelago, is interpreted by Catalano et al. (2008) and others to be one such transform fault, reactivated in a sinistral motion during the past 1 million years. Jongsma et al. (1987) relate the boundary faults of the grabens to a larger-scale wrench zone (the Medina Wrench) extending over more than 800 km and which is situated at around 35° latitude south of the Maltese Islands. The present-day recording of seismicity at these latitudes would be consistent with such a model, which is also linked to the formation of pull-apart grabens. Argnani (1990) on the other hand, by studying seismic profiles across the graben sections, fails to directly observe any strike-slip motion directly on the boundary faults. The NE-SW extension in the Sicily Channel has also been linked to crustal stretching resulting from the steep subduction of the African plate beneath the Tyrrhenian Sea, offshore northern Sicily (Argnani 1990), as well as to the north-eastward-

directed subduction of the Ionian crust below the Hellenic Arc (Belguith et al. 2011). Dart et al. (1993) describe both NEand NW-directed rift trends as being generated in response to N-S stretching in the Sicily Channel.

3.2.3 The Consequences of Rifting The presence of this rift system makes the Sicily Channel and the Maltese Islands a fascinating natural laboratory to study active or recent tectonic and depositional processes and presents a number of puzzling challenges. The Maltese archipelago presents an especially interesting case study since it is practically the only onshore area where associated faults of the SCRZ are clearly and spectacularly displayed and can be studied in detail. Moreover, this whole intricate web of fault systems and transform/transfer mechanisms is characterised by small magnitude (generally smaller than 4.0) but constant seismic activity that is currently being studied in greater detail and which can give more insight into the origin of these features and the mechanisms of the ongoing processes. Seismic networks have recorded hundreds of events over recent years, mostly associated with the bounding faults of the grabens and interconnecting transform faults. Seismic monitoring also reveals a cluster of activity about 80 km to the south of Malta which is not directly associated with the grabens, but which is probably linked to

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Central Mediterranean Tectonics …

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a dextral shear fault, as well as earthquake clusters in areas where no bathymetric fault expressions are observed, probably indicating the presence of buried fault systems. Unfortunately, the small magnitude of most of this seismic activity makes it quite a challenge to infer precise locations and focal mechanisms except for the more energetic events. Further progress on this count, mainly from recently improved seismic monitoring, should yield more definitive conclusions about the present-day motions within the Sicily Channel. Nonetheless, the presence of this seismic activity indicates that crustal deformation associated with the Sicily Channel Rift is still occurring. The onset of the most intense stage of graben formation in the Pliocene was preceded by shoulder upwarping on the two sides of the incipient rift, a mechanism reminiscent of the upwarping associated with the previous NW- SE extension during the Miocene. This shoulder upwarping has been described as the reason for the uplift of the Maltese Islands, which are consequently gently tilted to the north-east. The island of Lampedusa, on the opposite side of the SCRZ, is correspondingly tilted to the south-west. The clearest expression of the SCRZ onshore on Malta is the Magħlaq Fault, which can be traced for around 4 km along the south-east coast of Malta forming a stepped scarp with large blocks that have undergone sliding down steeply dipping fault surfaces together with rotation (Gauci and Scerri 2019, Chap. 5). The landward side of the fault is made up of the Lower Coralline Limestone formation, exposed to a height of more than 100 m, while on the seaward side, the whole sedimentary package has been brought down to sea level, where the subaerial land mass has mostly been eroded away, leaving a few slivers of Upper Coralline Limestone abutting the shoreline. At places along the fault, the fault

scarp is still very fresh. Figure 3.5a, b shows two examples of exposures of this fault along the southern coastline, where vertical slickensides are easily visible. The vertical downthrow of the fault has been measured at around 240 m, with remnants of the Upper Coralline Limestone formation, having subsided down to sea level, still visible adjacent to the Lower Coralline Limestone formation forming the foot wall (Illies 1981; Pedley et al. 2002). This vertical downthrow was responsible for the isolation of Filfla Island (Furlani et al. 2019, Chap. 21), made entirely out of Upper Coralline Limestone, being the highest point of the downthrown block and situated around 5 km offshore. The Magħlaq Fault is said to be the northernmost master fault of the graben system of the SCRZ. About 15 km south of the coastline, the sea depth drops sharply to about 1000 m at the base of the Malta graben. Since 2015, an ongoing sequence of microearthquake activity (magnitudes smaller than 3.5) has been recorded by seismic stations in the south-east of Malta, with epicentres located on, or very close to shore. This may imply some continued activity on or reactivation of the Maghlaq Fault or connected onshore faults. A more detailed interpretation of the Magħlaq Fault is given in Gauci and Scerri (2019, Chap. 5). An interesting case of neotectonic fault remodelling occurs on the south-eastern tip of the island of Gozo and to a lesser extent on the north-westernmost tip of Malta. The South Gozo Fault is the north-western master fault of the NE-SW trending fault system, its normal faulting nature evidenced by the remnants of Upper Coralline Limestone lying against the Globigerina and Lower Coralline Limestone shore rocks. In south-east Gozo, the region enclosed between the Qala Fault and the South Gozo Fault (the latter passing along the coastline) presently exhibits a dense

Fig. 3.5 a Fault scarp at ix-Xaqqa, along the southern coastline of Malta. b A further section of the Magħlaq Fault along the same coastline (photograph Andreas Neumann). In both cases, the Upper

Coralline Limestone is the downthrown block on the seaward side, and the scarp face is in Lower Coralline Limestone

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pattern of splay faults induced by a dextral shear regime (Reuther 1990). This is taken as evidence that the South Gozo Fault was reactivated during the Quaternary from an extinct normal fault to a strike-slip fault. Moreover, this dextral shear, oriented roughly east–west, is interpreted by Reuther and Eisbacher (1985) to be one of the strike-slip features facilitating the formation of pull-apart grabens and related to the broader dextral wrench zone characterizing the Central Mediterranean. Evidence for this remodeling is provided by the overprinting of horizontal or oblique slickensides on to older vertical ones in southern Gozo.

3.3

by the vertical tectonic movements that have brought different strata into juxtaposition, exposed whole stratigraphic sequences and caused marine and rainwater erosive action to act along lines of weakness representing faults and to produce differing erosive styles on various layers that are brought side by side. The importance of vertical tectonic movements on the landscape is best seen at coastal locations where the coastal rocks may change suddenly according to the extent of downward block shifts, resulting in very different erosion patterns adjacent to one another. There are a number of ways in which tectonic activity has played a major role in the formation of geomorphological features:

Tectonics and Landforms

The landforms and landscapes of the Maltese Islands are a direct result of both extensional phases described above (Illies 1981). Superimposed on these large-scale processes were differential weathering and erosion acting on the component rock layers of the stratigraphic package, each of which is characterised by differing geotechnical properties and a varying mechanical resistance to weathering (Scerri 2019, Chap. 4). The lowest exposed and oldest layer and the topmost layer, the Lower Coralline Limestone (LCL) and the Upper Coralline Limestone (UCL), respectively, are of similar lithology. Both are algal reef shallow water limestones and relatively hard, brittle and mechanically competent rocks. The LCL forms vertical cliffs when exposed along the coast, while the UCL is usually found as the capping layer of flat-topped plateaux in the western half of the archipelago. Both form karstic surfaces, with solution cavities and channels. The Globigerina Limestone formation (GL), on top of the LCL, is a fine-grained foraminiferal limestone and is more easily weathered, forming smooth rolling landscapes and gentle slopes except for two thin hard-wearing conglomerate beds within it, which normally stand proud or form steps in the slope (Gauci and Inkpen 2019, Chap. 27). The Blue Clay is the softest and mechanically weakest layer. It is easily weathered and becomes plastic when wet, flowing out above the underlying strata where exposed, and forming taluses or slopes. Where the whole stratigraphic sequence is exposed, such as along fault scarps or along the coast, the Blue Clay layer tends to destabilize the overlying UCL capping layer because it is much more easily eroded, leading to stresses and fracturing in the UCL, which breaks up along cliff-parallel fractures into progressively smaller blocks that topple or slide down the clay slopes. Rainwater percolates through the fractured UCL and stops flowing downwards when meeting the impervious Blue Clay beneath. Given the above differences in mechanical properties, the finer forms of the land surface have been determined mostly

a. Tilting approximately to the north-east as a result of upwarping associated with the SCRZ has ensured that south of the Great Fault, as well as to the north of the South Gozo Fault—where the land has not been particularly affected by vertical movements of block faulting, the LCL rises from sea level forming majestic sheer cliffs along the southern coastline of the islands. The highest point of the islands, ultimately determined by phases of uparching, occurs on the Rabat Plateau at 253 m asl. Conversely, the north-east coast of Malta takes the form of gentle slopes of Globigerina or Lower Coralline Limestone towards the shoreline. Tilting has produced a drainage pattern with preferential flow from the high points in the south-west to the north-eastern coastline. During wetter times in the Pleistocene, this drainage produced important river valleys, often following existing fault lines and enlarged by the action of water. A number of these river valleys may be followed offshore from the northern coast, indicating the one-time larger subaerial extent of the islands (Micallef et al. 2013; Prampolini et al. 2019, Chap. 10). Following subsidence of the northern coastline, the flooding of the river valley mouths produced, in particular, the Grand Harbour complex around Valletta (Schembri and Spiteri 2019, Chap. 6), which is itself defined by bordering faults. b. North of the Great Fault the dominant landscape is one of a sequence of ridges and valleys extending from coast to coast (i.e. horst-and-graben topography). This makes Malta an ideal place where block faulting can be observed very clearly and on an accessible scale. The eastern half of the Great Fault presents an evident scarp. Following erosion and denudation, the scarp face in this region is mostly in the Lower Coralline Limestone, with the downthrown Globigerina Limestone forming the flat plain of the hanging wall side (Fig. 3.6). This fault was used by the British military as a natural line of defence, along which a defensive wall was built

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Fig. 3.6 Part of the Great Fault, towards the eastern end, showing the fault scarp in Lower Coralline Limestone, and the downthrown plain in Globigerina Limestone. A section of the Victoria Lines can also be seen

(hence the alternative name Victoria Lines Fault). Further west, the fault gives way to a more gentle and smoothed slope, with the whole stratigraphy conserved but vertically displaced. Moving northwards, five main ridges (horst blocks) are encountered—Wardija Ridge, Bajda Ridge, Mellieħa Ridge, Marfa Ridge and Comino—the latter separated from the mainland by the South and North Comino Channels (Fig. 3.3b). The Pwales Valley is an example of a graben formed between two horst blocks of Bajda Ridge and Wardija Ridge, being a wide, flat-bottomed valley, floored by the Upper Coralline Limestone. Its surface lies mostly close to sea level and connects Xemxija Bay on the east coast to Għajn Tuffieha Bay (Zammit Pace et al. 2019, Chap. 18) on the west. The valley is intensively used for agriculture, being filled with a deposit of alluvial soils which thickens to the east and is mostly derived from weathering of rocks making up the sides of the horsts. c. Where the downfaulted blocks support low-lying plains sloping down to sea level, they form wide bays and sandy beaches closed in by fault-generated escarpments bounding the horsts, such as Mellieħa Bay, Xemxija Bay

and Għajn Tuffieħa Bay (Fig. 3.7 a, b). In other cases, the shape of the bay is more directly determined by the varying weathering styles of the two adjacent blocks at points where a fault line intersects the coast. For example, at Fomm ir-Riħ Bay (Sammut 2019, Chap. 16), where the Great Fault meets the coast on the west, the resistant LCL makes up the vertical cliffs forming the south side of the bay, while the northern side of the fault consists of downthrown Globigerina Limestone and Blue Clay, topped by the Upper Coralline Limestone (Fig. 3.8). This situation has favoured an accelerated marine erosion starting at the line of weakness of the fault and eroding away the softer downthrown side, forming an asymmetrical embayment, containing a small beach. The northern side of the bay also typifies a coastal landscape known as rdum. Here, the downthrow and direct exposure of the Blue Clay to marine action and other weathering agents cause rapid erosion of this layer. This induces stresses in the overlying UCL and fracturing of this layer into large blocks, having dimensions of several tens of metres, which ultimately detach, break up and slide down to the coast, further fragmenting into boulders of various sizes

28

P. Galea

Fig. 3.7 A view of Mellieħa Bay, occupying a downthrown block (graben) between two horst blocks, from the top of the northern horst bounding the bay, with the southern bounding horst in the background. Source Google Earth Image© 2016 Terra Metrics

Fig. 3.8 Fomm ir-Riħ Bay, on the south-western coast of Malta, where the Great Fault intersects the coast. The bay is formed along the fault line and enlarges through differential erosion of the two sides. The cliffs are in the Lower Coralline Limestone

3

Central Mediterranean Tectonics …

29

Fig. 3.9 A Google Earth view of Anchor Bay, a fault-controlled bay on the north-western coast of Malta. Source Google Earth Image© 2016 Terra Metrics

(Soldati et al. 2019, Chap. 14). The whole process results in a boulder-strewn, and often inaccessible coast, which is the typical form of headlands along the north-west coast (Devoto et al. 2013; Biolchi et al. 2016; Chaps. 17 and 24; Soldati et al. 2019, Chap 14; Rolé 2019, Chap. 24). These coastal features are described in detail elsewhere in this book. Another example of this type of fault-controlled bay is Anchor Bay (Soldati et al. 2019, Chap. 14), also on the north-western coast (Fig. 3.9). At both the northern and southern sides of the fault, the surface outcrop is the Upper Coralline Limestone. However, the southern side is relatively downfaulted so that the UCL is at sea level, whereas at the northern side, it is the Blue Clay which is at sea level, with resulting rapid erosion, and destabilization of the Upper Coralline Limestone and spectacular examples of fracturing, block sliding, toppling and a boulder-filled shoreline.

3.4

Conclusion

Although the sedimentary geology of the Maltese Islands is a relatively simple layer-cake of limestones, clays and marls, its setting in a complex and rapidly changing tectonic environment has resulted in intense faulting and mainly vertical block movements. This has produced a variety of situations that have fundamentally controlled the geomorphological development of the islands. Other major processes, such as the effects of surface and sub-surface water have, over the years, continued further to sculpt the resulting landforms and are discussed in other chapters of this book. Ultimately, however, it is the regional tectonic processes, powered by the Earth’s internal energy, which have provided the large-scale vertical mass movements, and established the setting for the sculpting of impressive landscapes.

30

References Argnani A (1990) The Strait of Sicily rift zone: foreland deformation related to the evolution of a back-arc basin. J Geodyn 12(2):311– 331 Belguith Y, Geoffroy L, Rigane A, Gourmelen C, Dhia HB (2011) Neogene extensional deformation and related stress regimes in central Tunisia. Tectonophysics 509(3):198–207 Biju-duval B, Dercourt J, Le Pichon X (1977) From the Tethys ocean to the Mediterranean seas: a plate tectonic model of the evolution of the western Alpine system. In: Histoire structurale des bassins méditerranéens, 143 Biolchi S, Furlani S, Devoto S, Gauci R, Castaldini D, Soldati M (2016) Geomorphological identification, classification and spatial distribution of coastal landforms of Malta (Mediterranean Sea). J Maps 12(1):87–99 Carminati E, Doglioni C (2004) Mediterranean tectonics. Encycl Geol 1:135–146 Catalano S, De Guidi G, Romagnoli G, Torrisi S, Tortorici G, Tortorici L (2008) The migration of plate boundaries in SE Sicily: influence on the large-scale kinematic model of the African promontory in southern Italy. Tectonophysics 449(1):41–62 Cello G (1987) Structure and deformation processes in the strait of Sicily “rift zone”. Tectonophysics 141(1):237–247 Corti G, Cuffaro M, Doglioni C, Innocenti F, Manetti P (2006) Coexisting geodynamic processes in the Sicily channel. Geol Soc Am Spec Pap 409:83–96 Dart CJ, Bosence DWJ, McClay KR (1993) Stratigraphy and structure of the Maltese graben system. J Geol Soc 150(6):1153–1166 Devoto S, Biolchi S, Bruschi VM, Díez AG, Mantovani M, Pasuto A, Soldati M (2013) Landslides along the north-west coast of the Island of Malta. In: Margottini C, Canuti P, Sassa K (eds) Landslide science and practice, vol 1. Landslide inventory and susceptibility and hazard zoning. Springer, Berlin, Heidelberg, pp 57–63 Dewey JF, Helman M, Knott SD, Turco E, Hutton DHW (1989) Kinematics of the western Mediterranean. Geol Soc Lond Spec Publ 45(1):265–283 Faccenna CT, Lucente F, Jolivet L, Rossetti F (2001) History of subduction and back arc extension in the Central Mediterranean. Geophys J Int 145(3):809–820 Furlani S, Gauci R, Devoto R, Schembri JA (2019) Filfla: a case study of the effect of target practice on coastal landforms. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 261–271 Gardiner W, Grasso M, Sedgeley D (1995) Plio-pleistocene fault movement as evidence for mega-block kinematics within the Hyblean-Malta Plateau, Central Mediterranean. J Geodyn 19 (1):35–51 Gauci R, Scerri S (2019) A synthesis of different geomorphological landscapes on the Maltese Islands. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 49–65 Gauci R, Inkpen R (2019) The physical characteristics of limestone shore platforms on the Maltese Islands and their neglected contribution to coastal land use development. In: Gauci R,

P. Galea Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 343–356 Grasso M, Reuther C-D, Baumann H, Becker A (1986) Shallow crustal stress and neotectonic framework of the Malta Platform and the southeastern Pantelleria Rift (Central Mediterranean). Geol Romana 25:191–212 Illies JH (1981) Graben formation—the Maltese Islands—a case history. Tectonophysics 73(1):151–168 Jongsma D, van Hinte JE, Woodside JM (1985) Geologic structure and neotectonics of the North African continental margin south of Sicily. Mar Pet Geol 2(2):156–179 Jongsma D, Woodside JM, King GCP, Van Hinte JE (1987) The Medina Wrench: a key to the kinematics of the central and eastern Mediterranean over the past 5 Ma. Earth Planet Sci Lett 82(1):87–106 Micallef A, Foglini F, Le Bas T, Angeletti L, Maselli, V, Pasuto A, Taviani M (2013). The submerged paleolandscape of the Maltese Islands: Morphology, evolution and relation to Quaternary environmental change. Mar Geol 335:129–147 Pedley M, Clarke MH, Galea P (2002) Limestone isles in a crystal sea: the geology of the Maltese Islands. Publishers Enterprises Group (PEG), San Gwann, Malta, 109p Prampolini M, Foglini F, Micallef A, Soldati M, Taviani M (2019) Malta’s submerged landscapes and landforms. In: Gauci R, Schembri JA (eds), Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 117–128 Reuther CD (1984) Tectonics of the Maltese Islands. Centro 1(1):1–20 Reuther CD (1990) Strike-slip generated rifting and recent tectonic stresses on the African foreland (Central Mediterranean region). Ann Tectonicae 4(2):120–130 Reuther CD, Eisbacher GH (1985) Pantelleria Rift—crustal extension in a convergent intraplate setting. Geol Rundsch 74(3):585–597 Reuther CD, Ben-Avraham Z, Grasso M (1993) Origin and role of major strike-slip transfers during plate collision in the central Mediterranean. Terra Nova 5(3):249–257 Rolé A (2019) Landforms and processes at Il-Majjistral park and its environs. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 305–316 Sammut S (2019) Fomm ir-Riħ and the vigorous nature of its shingle beaches. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 193–202 Scerri S (2019) Sedimentary evolution and resultant geological landscapes. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 31–47 Schembri JA, Spiteri SC (2019) By Gentlemen for Gentlemen—Ria coastal landforms and the fortified imprints of Valletta and its harbours. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 69–78 Soldati M, Devoto S, Prampolini M, Pasuto A (2019) The spectacular landslide-controlled landscape of the northwestern coast of Malta. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 167–178 Zammit Pace ML, Bray M, Potts J, Baily B (2019) The beaches of the Maltese Islands: a valuable but threatened resource? In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 213–227

4

Sedimentary Evolution and Resultant Geological Landscapes Saviour Scerri

Abstract

Details of the subsurface geology are scarce but in Late Palaeozoic times, the Maltese Islands lay close to the Equator in the Tethys Ocean, that extended between the continents of Gondwana and Laurasia. The oldest subsurface rocks recorded offshore in southeast Sicily are Late Triassic intertidal dolomites (Gela Formation), overlain by Jurassic Black shales (Streppenosa Formation) and platform carbonate of the Siracusa Formation. The exposed geology of the Maltese Islands comprises a marine sedimentary rock sequence about 250 m in thickness, composed of limestones, marls and clays. Ages range from the Upper Oligocene to the Holocene. The stratigraphy consists of the five principal pre-Pliocene Formations: the Lower Coralline Limestone (Oligocene); the Globigerina Limestone (Miocene); the Blue Clay (Miocene); Greensand (Miocene) and the Upper Coralline Limestone (Miocene). The Quaternary is represented by a variety of marine and freshwater deposits (i.e. raised beaches and deposits from freshwater lakes and marine high stands), whereas continental sedimentation is evidenced by fluvial conglomerates; fanglomerates; slope talus; sand-dunes; cave and fissure fills; caliche and speleothems. Keywords








Sedimentary limestone Oligo-Miocene Stratigraphy Members Beds




S. Scerri (&) Department of Geography, University of Malta, Tal-Qroqq, Msida, MSD 2080, Malta e-mail: [email protected] © Springer Nature Switzerland AG 2019 R. Gauci and J. A. Schembri (eds.), Landscapes and Landforms of the Maltese Islands, World Geomorphological Landscapes, https://doi.org/10.1007/978-3-030-15456-1_4

4.1

Introduction

The Maltese Islands lie at the northern margin of the Pelagian Platform and in part owe their importance to the fact that they form emergent land in the central Mediterranean (Galea 2019, Chap. 3), on a ridge separating the eastern and the western Mediterranean where Europe and Africa come closest together, exposing rocks ranging in age from the Late Oligocene to the Pleistocene. The oldest rocks known to occur in the subsurface of southeast Sicily and the Maltese Islands, both of which are situated on the undeformed Pelagian foreland (Catalano et al. 1995), are Late Triassic intertidal dolomites of the Gela Formation (Scandone et al. 1981). The geological history of the Maltese Islands from the Jurassic times onwards belongs to that of a prevailing shallow carbonate platform interrupted from time to time by submarine volcanic events which are associated with the opening of the Ionian Basin from early Jurassic to Late Cretaceous times (Scandone et al. 1981). The Maltese archipelago is composed of a marine sedimentary rock sequence, which is ca. 250 m thick and consists of limestones, marls and clays ranging in age from Upper Oligocene to Pleistocene (Pedley et al. 1976; Pedley 2011). The stratigraphy of this rock sequence was first described in the 19th century by a number of British geologists such as by Frederick Wollaston Hutton in 1866 and Andrew Leith Adams in 1870 (Gauci and Schembri 2019). The stratigraphy was sub-divided into the five formations using similar divisions which are currently in use: Upper Coralline Limestone (youngest); Greensand; Blue Clay; Globigerina Limestone and Lower Coralline Limestone (oldest). Interpretation of the stratigraphy has been further refined since then (Felix 1973; Pedley 1974, 1978, 2011; Dart 1991). The stratigraphic sequence is summarised in Table 4.1, and Fig. 4.1 shows the simplified geological map of the archipelago.

31

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S. Scerri

Table 4.1 Stratigraphic sequence of Maltese sedimentary rock units from the oldest formation (bottom) to the youngest (top) EPOCH (Stage)

Formation

Member

PLEISTOCENE (Calabrian) MIOCENE (Messinian)

Notes San Leonardo Beds

Ġebel Imbark

Upper Coralline Limestone

(Tortonian/Messinian)

Tal-Pitkal

(Tortonian)

Mtarfa Għajn Melel

MIOCENE (Lhangian/Tortonian)

Greensand

MIOCENE (Lhangian/Tortonian)

Blue Clay

MIOCENE (Burdigalian/Lhangian)

Globigerina Limestone

Upper Globigerina Limestone

(Aquitanian/Burdigalian)

Middle Globigerina Limestone

(Aquitanian) OLIGOCENE (Chattian)

Lower Globigerina Limestone Lower Coralline Limestone

Il-Mara Xlendi

(Chattian)

Attard

(Chattian)

Wied Magħlaq

4.2

Lithostratigraphic Description of the Rock Units

4.2.1 Lower Coralline Limestone (LCL) This is the oldest (Upper Oligocene) rock unit exposed in the Maltese archipelago and is composed of massive and resistant grey to light brown limestones. Due to the regional dip of the islands to the northeast, this formation dominates the steep, mostly inaccessible sea cliffs along the southwest coast of Malta from Bengħisa to Fomm ir-Riħ (Fig. 4.2). The formation exhibits its maximum exposed thickness in sea cliff sections at Ta’ Ċenċ, in Gozo, where it is 140 m thick and at Għar Bittija on Malta, where the exposed section is 120 m thick (Gauci and Scerri 2019, Chap. 5). On the north-eastern coastline, exposures are generally limited to the uppermost beds of the formation, which are exposed almost uninterruptedly from Madliena Tower (Dragut Point) at Tigné and il-Kalanka tal-Patrijiet to Marsaskala Bay. Inland exposures are restricted to locally faulted inliers and deeply incised valleys such as Wied Inċita, Wied Qirda and Wied Ħanżir, Wied iz-Ziju, Wied Dalam, Wied Ħas-Saptan and Wied tal-Isperanza. On the footwall of the Great Fault, the formation is exposed from Torri Falka to Naxxar and Għargħur area, and further on to Madliena Tower on the north-eastern coastline.

Pedley (1978) subdivided this rock formation into four members. In eastern Malta, it is represented by the il-Mara Member that is about 20 m thick and the Attard Member which is about 35 m in thickness. In central Malta up to the Great Fault, Magħtab and Għallis area further to the west, the Lower Coralline Limestone is represented by the Magħlaq Member: the Attard Member (about 35 m thick) and the Xlendi Member (about 15 m thick). The contact with the overlying Globigerina Limestone Formation is sharp and is represented by a hardground (Bennet 1980) and is often accompanied by a 5-cm-thick phosphatic conglomerate bed. In most of the literature, this contact is termed the ‘Scutella transition bed’.

4.2.1.1 Magħlaq Member This member takes its name from the Wied Magħlaq locality, where the section exposed above sea level in the Magħlaq quarry is estimated to be about 38 m in thickness. The limestone is a medium- to fine-grained calcarenite, comprising mudstones and wackestones1 that are cream or chalky white in colour and are often soft and highly porous. In cliff sections, where it is best exposed, this member consists of a sequence of parallel bedded limestones often

1

Wackestone is a matrix-supported carbonate rock with over 10% of recognisable grains (or allochems) set in a carbonate mud matrix.

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Sedimentary Evolution and Resultant Geological Landscapes

33

Fig. 4.1 Simplified geological map of the Maltese Islands. Source Redrawn and modified after Oil Exploration Directorate (1993a, b)

over 3 m in thickness (Fig. 4.3a). Apart from the regular parallel bedding, sedimentary structures are otherwise absent. The member is generally characterised by its scarce fossil content. The macrofauna is represented by echinoids and marine bivalve molluscs. The abundance of micritic sediment and the sparse fauna represented mainly by miliolids2 suggests a lagoonal or back reef environment, deposition taking place in channels between beds of sea grasses (Felix 1973). Echinoid biofacies within the member

2

Miliolids are foraminifera that are abundant in shallow waters, especially in estuaries and along coasts.

have living analogues which show preferences for coarse-grained substrates. As the facies appear to be quite extensive, the unit could have formed part of an extensive shallow platform at a few metres in depth (Felix 1973). The strata at Wied Inċita are observed to pass transitionally upwards into the Attard Member, the transition being marked by a rapid change from miliolid mudstones and wackestones to algal wackestones. On Gozo, the transition is marked by a red bed.

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S. Scerri

Fig. 4.2 Topographic map of the Maltese Islands showing the relief, valleys and places referred to in the text. Source DEM map from ERDF LIDAR data (2012)

4.2.1.2 Attard Member This member was first described at the Attard quarries by Pedley (1978), where 10 m of pale grey ‘biosparites’ associated with abundant algal rhodoliths3 are exposed in a quarry section. Throughout the area of its distribution, especially in eastern Malta, the Attard Member is mainly represented by white limestone composed of detrital coralline algae with scattered, variably developed algal rhodoliths. Excellent exposures of this member occur in quarries at

3

Rhodoliths are coloured, marine red algae which resemble coral.

Wied iz-Ziju, Wied Moqbol, Wied Fulija, Wied Inċita and Salina. Coral reef facies within the member are restricted to a belt along the palaeo-highs of Għar Lapsi, Attard and Naxxar. It is also known to occur in the galleries of Ta’ Kandja and Wied Moqbol quarries (Fig. 4.3a, b). Examination of numerous sections both in Malta and in Gozo has permitted four distinctive sub-facies within the Attard Member to be defined, of which the most widely developed are: a. detrital coralline algal sub-facies (about 25 m thick) (Fig. 4.3b). b. an algal rhodolith sub-facies (about 10 m thick).

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Sedimentary Evolution and Resultant Geological Landscapes

35

Fig. 4.3 Exposures of the Lower Coralline Limestone: a The quarry at Wied Moqbol exposes the Wied Magħlaq Member at the base, succeeded by massive beds of the Attard Member, il-Mara Member and Lower Globigerina Limestone Member capping the sequence. b A

cutting at Mosta exposing white fragmental algal limestone of the Attard Member. c Cliff face exposing a 20 m thick section of the Xlendi Member at Għar il-Qamħ (Gozo). Contact is seen at the base. d Exposed facies of il-Mara Member with thick beds of biocalcarenites

The most widespread and distinctive feature of this member is the white detrital coralline algal sub-facies, which is very well represented and replaces the algal rhodolith sub-facies east of a direction line from Wied Inċita to Għar Lapsi. The algal rhodolith sub-facies (together with the Xlendi Member) produces the best concrete aggregate and in the past has been widely used for curbstones and road surfacing. In the absence of asphalt, it was also frequently used as a replacement for damp-proofing in building construction. The light brown to brown or grey variety also takes a high polish and in the past has been quarried to produce an ornamental stone that is known locally as ‘Gozo or Malta Marble’. The best exposures of this unit are those at Ħondoq ir-Rummien and Qala in Gozo. Unfortunately, the unit is not hard and is easily pitted. The Attard Member is characterised by a series of sub-facies which are indicative of widely

varying sedimentary conditions that ranged from calm lagoonal to high energy environments where coral patch reefs developed.

4.2.1.3 Xlendi Member This member is composed of well-indurated, thick to very thickly bedded brown, pale grey biocalcarenites and biocalcirudites. Large-scale cross-stratification is characteristic of this member (Fig. 4.3c). The unit is widespread, but its thickness is highly variable ranging from 10 to 15 m. At the type section at Xlendi, it is about 10 m thick. Other typical sections of this unit, where the underlying Attard Member is present, are found at Wied Qirda and Wied Fulija. It is absent from exposures at Xgħajra, Wied iz-Ziju and Wied Ħas-Saptan in eastern Malta. Fragments of the echinoid Scutella are dispersed in the rock, with higher concentrations

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S. Scerri

Table 4.2 The Dunham classification system for carbonate sedimentary rocks (Dunham 1962) and refined by Embry and Klovan (1971) to include sediments that were organically bound during deposition Grains (size: 2–0.063 mm) not bound during deposition Matrix composed of clay and fine silt particles Mud-supported

Lacks mud Grain-supported

Less than 10% grains

More than 10% grains

Grains bound by micrite

Grains bound by crystalline calcite

Mudstone

Wackestone

Packstone

Grainstone

of whole and/or fragmented shells at the top, producing the Scutella breccias. This member is also generally missing or thinly developed on the southwest coastline from Rdum Qammieħ to Buxiħ, as well as in south Malta where the overlying il-Mara Member facies is better developed. The coarse cross-bedded packstones (Table 4.2) and grainstones of the Xlendi Member are succeeded by laterally continuous beds of yellow fine limestones of the il-Mara Member, the contact being particularly sharp where the latter is not well developed.

4.2.1.4 Il-Mara Member This facies is composed of yellow to pale yellow, or brown massive or laminated and laterally continuous thick to very thick beds of biocalcarenites which are rich in giant Lepidocyclina, Bryozoans and echinoid spines and plates (Fig. 4.3 d). The name il-Mara derives from the locality of il-Mara in eastern Malta, where this member is best developed and was formerly accessible in a quarry, cut in the cliff face. This quarry was renowned among palaeontologists for the presence of giant Lepidocyclinae, that are also found in Wied Babu where there is a representative and accessible section. Il-Mara Member was deposited in open marine conditions in a fore-slope environment, in water with depths ranging from 5 to 20 m. The orientation of large echinoid spines and macrofossils indicates west-directed submarine currents in an easterly deepening basin, and transgression over the underlying shallow platform deposits of the Xlendi Member. The member is best developed in eastern Malta: from Wied Fulija to il-Mara on the southwest coastline; from San Rocco to Wied iz-Ziju; in Wied Dalam and at Wied Ħas-Saptan where it is over 20 m thick. It thins to 1 m at Bengħisa in the southwest (Fig. 4.2). In eastern Malta, where the unit is best developed and in southeast Gozo, where it is moderately developed, the contact with the overlying Lower Globigerina Limestone is

Original components have been bound together during deposition as in algal and coral reefs

Boundstone

usually sharp, particularly along the Xgħajra and Żonqor coastline. The top of the il-Mara Member is marked by the hardground with a phosphatic and iron-impregnated surface bored by polychaetes and, to a lesser extent, by bivalves and clionid sponges. It is encrusted by oysters, sponges and bryozoa, which are often associated with a phosphate conglomerate bed. Although generally not well exposed, the phosphatic conglomerate that caps the Lower Coralline Limestone formation is clearly visible at many localities, including il-Kalanka tal-Patrijiet and Xgħajra. One of the best exposures of this bed is located at Żonqor point, where it is also designated as a Site of Scientific Importance.

4.2.2 Globigerina Limestone (GL) The Globigerina Limestone, so named because of the abundance of planktonic foraminifera, crops out extensively in Malta and Gozo (Pedley 1978). The formation comprises three members: the Lower Globigerina Limestone (LGLM), the Middle Globigerina Limestone (MGLM) and the Upper Globigerina Limestone (UGLM). The Lower and Middle Globigerina Limestone Members are separated by a phosphatic conglomerate bed (the Lower Phosphorite Conglomerate Bed C1), and the Middle and Upper Globigerina Limestone Members are separated by another phosphatic conglomerate bed (the Upper Phosphorite Conglomerate Bed C2) (Oil Exploration Directorate 1993a, b).

4.2.2.1 Lower Globigerina Limestone Member (LGLM) The Lower Globigerina Limestone Member represents the unit most frequently cropping out across the low-lying plains of central and eastern Malta. This unit is the best represented rock type in southern Malta. The best exposures are to be found in the deep quarries of Tad-Dawl, Siġġiewi, tal-

4

Sedimentary Evolution and Resultant Geological Landscapes

Ħandaq, Mqabba and Qrendi. Other exposures are mostly limited to field terraces, road side cuttings and numerous minor exposures. Reclaimed abandoned quarries are common in the region around Żebbuġ and have now mostly been excavated for new development. Of the three members comprising the Globigerina Limestone, this member shows the most widely varying facies. It thins markedly in the area of Attard and Żabbar and thickens to over 40 m at Santa Luċija and in the area of tad-Dawl. In the Mqabba and Qrendi area, its maximum thickness is of the order of 40 m. Within the Maltese Islands, LGLM may be further subdivided into two principal beds from the base to the top as follows: a. Sub-facies A (Maltese: ‘Soll Ikħal’): The base of the LGLM is characterised by a typically grey or yellow globigerinid clayey limestone with parallel banded laminations and rust-coloured burrows (bioturbations). This clayey limestone makes up about half the thickness of the entire Lower Globigerina Limestone Member and is characterised by heavily iron mineralised, rust-coloured burrows, which in recent cuttings often reveal frequent lenses and beds of bluish grey clayey or marly limestone (Fig. 4.4a). Burrowing is generally of the straight type and is not as intense as thalassinoidean burrow systems, and bedding planes are frequently preserved. Iron mineralisation of the burrow systems impart its yellow colour which, in some local facies variation, is particularly well developed and imparts a rust mottled colour to it (in Maltese: ‘Soll Aħmar’). b. Sub-facies B (Maltese: ‘Tal-Franka’) (Fig. 4.4b): This bed is composed of soft white, cream to yellow mediumto fine-grained, intensely bioturbated calcarenite. Although apparently massive when freshly excavated, differential weathering reveals an originally well-bedded limestone, with parallel bedding or cross-laminations. Owing to intense bioturbation, this bedding has been almost totally obliterated, particularly in the lower sections. Petrographic examination reveals that the microfaunal content is dominated by globigerinids which account for its lighter colour, and the rock can be defined as a globigerinid wackestone. Macrofauna are represented by variably oriented often disarticulated, pectinid bivalves, echinoids and vertebrate debris. Its lighter colour, as compared to the darker colour of underlying beds, is noteworthy and is attributed to the particular abundance of mostly fragmented and badly preserved fossil tests of planktonic foraminifera. Benthonic foraminifera are also common. ‘Tal-Franka’ stone is the principal mineral resource of the LGLM as a building stone. This

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rock unit shows a highly variable thickness of up to about 8 m on the SW coastline such as at il-Qammieħ, Ġnejna, Fomm ir-Riħ (Fig. 4.4c) to Għar Bittija and Ta’ Ċenċ on Gozo while, in contrast, it is about 120 m thick at Valletta in the NE. It may be regarded as a wedge deposited on a pre-existing block tilted to the NE. Evidently the island had already acquired its tilt to the NE at this time. Some of the horizons/beds are occasionally separated by local pebble beds, the most prominent of which is a scour surface and a thin phosphatic pebble bed that marks the boundary between the two principal sub-divisions of the LGLM: the cream/yellow lithofacies sub-facies B; and the underlying yellow/blue grey lithofacies sub-facies A. The top of the member is marked by a hardground, and this is overlain by C1, the Lower Phosphorite Conglomerate Bed (Oil Exploration Directorate 1993a). This phosphatic conglomerate bed contains nodules formed in situ on the sea floor and similar to the phosphatic nodules dredged from modern seabeds. In 2019, the International Union of Geological Sciences designated the Maltese Lower Globigerina Limestone as a Global Heritage Stone Resource in recognition of its widespread historic use and resultant cultural heritage.

4.2.2.2 Middle Globigerina Limestone Member (MGLM) Middle Globigerina Limestone Member (Maltese: ‘Kaħla’ or ‘Turbazz’) lies unconformably on the underlying Lower Globigerina Limestone Member (Oil Exploration Directorate 1993a).The MGLM is best preserved where it has been protected by the Upper Globigerina Limestone Member and other overlying formations. It is, for instance, extensively developed on the southwest slopes of the Rabat-Dingli Plateau from il-Fawwara to Fomm ir-Riħ. Exposures of the marl beds of the MGLM are usually white and highly fractured with anastomosing cracks which render the beds highly vulnerable to weathering and erosion and, in contrast to bounding members, they form a more gently sloping landscape (Fig. 4.5a). When freshly excavated, beds are bluish grey in colour. The basal 0.5–1 m usually consists of a competent white, greyish white or yellow limestone rich in foraminifera and phospho-glauconitic clasts that pass upwards into foram-coccolith marly limestone and marl interbeds. Several phosphoglauconitic chert-rich layers occur, ranging from 2 to 100 cm thick within this bed. The MGLM attains a thickness of 30 m at Fomm ir-Riħ where Bennett (1980) has established its type section. Giannelli and Salvatorini (1972) record a maximum thickness of over 40 m at this locality (Fig. 4.5b). It attains its maximum thickness at Delimara where over 100 m has been drilled.

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Fig. 4.4 Exposures of the Lower Globigerina Limestone Member: a Cutting at Tigné showing Facies A of with characteristic bluish grey patches. b Thin (2 m) development of cross-bedded Lower Globigerina Limestone Member at Fomm ir-Riħ terminating in a brown phosphate

conglomerate bed, at the top of a shore platform. c Quarry at Siġġiewi (Malta) cut in Lower Globigerina Limestone Member Facies B —'Tal-Franka' stone. Quarry face is about 30 m high

4.2.2.3 Upper Globigerina Limestone Member (UGLM) Outcrops of this member are mostly restricted to areas protected by the Upper Coralline Limestone where it crops out on slopes of the deeper valleys. Owing to the underlying Middle Globigerina Limestone Member marls on the southwest coastline, it forms near-vertical scarps, whereas in exposures northeast of the Rabat-Dingli Plateau, owing to its dip slope attitude and the intervening middle marly unit, it forms two very conspicuous broad steps. On Gozo, exposures are more common and it usually forms a type of flat-topped landform known in Maltese language as ‘il-Mejda’ (meaning tableland). The best exposures of this sequence may be observed at Wied tal-Qlegħa, Rdum

il-Qammieħ and Delimara. Its thickness is generally quite uniform and is of the order of 14–18 m, but drops to 8 m along the SW coastline. At the base of the Upper Globigerina Limestone Member there is one (sometimes two) phosphate conglomerate beds, about 20 cm thick. This is the Upper Phosphorite Conglomerate Bed (C2) according to Oil Exploration Directorate (1993a, b). The clasts never exceed 5 cm in diameter, and fish teeth are common. Owing to the support by a marly lime mud, this bed erodes very easily and does not stand out as a prominent ledge and is often masked by weathered material from the overlying grey marl facies bed (Gauci and Inkpen 2019, Chap. 27). The contacts with the bounding units are sharp.

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Sedimentary Evolution and Resultant Geological Landscapes

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Fig. 4.5 Outcrops of Globigerina Limestone: a Shoreline slope marls of the Middle Globigerina Limestone Member and yellow Upper Globigerina Limestone Member at the top. b Middle Globigerina Limestone Member exposure at Delimara (Malta). c Yellow Upper

Globigerina Limestone Member at Fomm ir-Riħ (Malta) showing two yellow beds each about 5 m thick, and a grey marl interbed covered by vegetation

This member represents the uppermost subdivision of the Globigerina Limestone Formation and is subdivided by Felix (1973) as follows:

On Gozo, the lower limestone layer is known in the Maltese language as ‘ġebla tal-kwiener’. It is very resistant to heat and is quarried in Tal-Imgħajjen near Xewkija, in Ta’ Ħamet and other localities. It is used for building ovens and small stoves. At the top of the member, there is a rapid transition (over about 1 m) to the Blue Clay formation, characterised by increase in clay content of the bed. It is interesting to note that at Ras il-Pellegrin, this boundary has been proposed as the Global Stratotype Section for the base of the Serravallian Stage (Lirer and Iaccarino 2011). This section also records a major Middle Miocene global cooling event (Abels et al. 2005).

a. Phosphate pebble bed (at the base, C2 or Upper Phosphate Conglomerate Bed of Pedley 1978). b. Yellow/orange mottled limestone (foraminiferal wackestone facies). c. Dark grey middle bed (foram-coccolith grey marly facies). d. Yellow/orange mottled foraminiferal wackestone facies at the top.

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4.2.3 Blue Clay (BC) The Blue Clay formation is a marly unit of alternating light to dark layers spanning the Serravalian (CN4 to CN6, after Kienel et al. 1995) that follows the Globigerina Limestone. The carbonate content in the Blue Clay is relatively low (*25%), and the formation represents the only terrigenous sediment of the Maltese rock succession. It is composed of bluish grey coloured banded kaolinitic marls and clays, or olive green marls and clays with no apparent banding. In some places, such as near il-Ġordan and Ramla (Gozo) and Fomm ir-Riħ (Malta), the Blue Clay is exposed as a sequence of alternating dark and light grey layers (Fig. 4.6a, b). The Blue Clay occurs throughout eastern Gozo and western Malta and exhibits considerable thickness variation. It attains its maximum development at Xagħra, Gozo. In the eastern sector of the Rabat-Dingli Plateau, it is about 30 m thick. The Maltese name for the Blue Clay is ‘tafal’, and since prehistoric times, its pure clay layers have provided an important source of raw material for the manufacture of local pottery and sculpture models. Colour banding derives from the varying concentrations of calcium carbonate in the form of fossil tests of planktonic and benthonic foraminifera. The light coloured layers correspond to higher calcium carbonate content, mostly in the form of planktonic and benthonic foraminifera with lower kaolinite content. The clay content of the dark, almost pure clay bands, ranges from 90 to 94%, and these are best described as marly clays, while in the lighter coloured bands it ranges from 80 to 60%. The Blue Clay contains a rich assemblage of macrofauna represented by molluscs,

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echinoids, and solitary corals, fish remains and marine mammals, though most of the larger fossils have been crushed during consolidation. Sediments of the Globigerina Limestone and Blue Clay were deposited in a low-energy, open marine environment with paleobathymetric estimates ranging from depths of around 150–600 m (Bellanca et al. 2002, John et al. 2003). Studies on benthic foraminifera (Bellanca et al. 2002) and clay mineral (John et al. 2003) of both the Globigerina Limestone and Blue Clay, suggest that the transition in deposition times from the Upper Globigerina Limestone Member to Blue Clay were associated with overall lower bottom water oxygen levels, more humid climate conditions and more intense continental weathering with increased influx of terrigenous sediment.

4.2.4 Greensand The overlying Greensand and Upper Coralline Limestone rest on the Blue Clay formation, above a slight angular unconformity. This boundary is rarely visible, however, as most of the Greensand being usually thin, is buried under talus deposits derived from the overlying Upper Coralline Limestone. The Greensand formation consists of a glauconitic sand bed ranging from 0.5 to 11 m in thickness. On the island of Malta, the thickness of the Greensand is usually less than 0.5 m or is absent. Its exposure is limited because it is frequently buried under talus. The Greensand is best developed on Gozo where it exhibits its maximum thickness of 11 m. It

Fig. 4.6 Blue Clay exposures: a Blue Clay slopes at Fomm ir-Riħ (Malta) exposing colour banded clays and marls. b Exposure of the basal beds of Blue Clay at Ramla Bay (Gozo) also showing the contact with the underlying Upper Globigerina Limestone Member

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Sedimentary Evolution and Resultant Geological Landscapes

consists of massive bedded friable, poorly cemented intensely burrowed greyish green, sometimes almost black glauconitic marly limestone. The dark colour is imparted by glauconite which at times, due to oxidation and release of iron oxides, gives a pale yellow spotted appearance to the exposed sections. Unexposed sections are dark grey to black in colour. The presence of glauconite indicates basin starvation and a very low rate of sedimentation in a shallow marine environment. Due to its thin exposure conditions on the island of Malta, the Oil Exploration Directorate incorporated the mapping of the Greensand unit within the lowermost unit of the Upper Coralline Limestone, the Għajn Melel Member, on the Geological Map of Malta (Sheet 1) (1993a). A thicker sequence of the Greensand is present on Gozo, and the Greensand formation is represented separately on the Geological Map of Gozo and Comino (Sheet 2) (Oil Exploration Directorate 1993b).

4.2.5 Upper Coralline Limestone (UCL) The characteristics of this formation show similarity with the Lower Coralline Limestone formation, particularly with regard to colour and coralline algal content (Pedley et al. 1976). The Upper Coralline Limestone is exposed on the three main islands of the Malta archipelago and often supports karst topography. Pedley (1978) subdivided the Upper Coralline Limestone formation into four members as explained in the following sub-sections.

4.2.5.1 Għajn Melel Member This member forms the base of the Upper Coralline Limestone. It is best developed on Gozo where it attains a maximum thickness of 13 m and comprises brown and ginger coloured coarse limestone, mostly resistant to weathering (Fig. 4.7a). It is composed of massive brown to light brown glauconitic limestone rich in Heterostegina, a benthic foraminiferid. 4.2.5.2 Mtarfa Member This member is characterised by light yellow cream or white limestones and marls with beds of algal nodules or rhodoliths or their derived sediments. It is underlain by Greensand or the Għajn Melel Member and is overlain by patch reefs and calcirudites (rudstones) of the Tal-Pitkal Member. The name derives from the village of Mtarfa where the type section has been established. A distinctive coralline algal biostrome up to 16 m in thickness is developed (Fig. 4.7b) to the west of a line drawn from Rdum il-Ħmar on the north coast to Rdum Dikkiena on the south coast.

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The chalky facies of the rock, which may account for 40% of the total volume, does not produce suitable aggregate. In northern Malta, at tal-Palma, Mġarr and at L-Aħrax tal-Mellieħa, this rock used to be extracted in small quantities for the production of lime.

4.2.5.3 Tal-Pitkal Member This member overlies the Mtarfa Member and caps the local rock sequence on the Rabat-Dingli Plateau, and the horsts and troughs of Northern Malta (Gauci and Scerri 2019, Chap. 5). The cream to yellow, marly and badly weathered limestone and marly limestone of the Mtarfa Member often passes rapidly and abruptly into pale grey or very light brown limestone (Fig. 4.7c, d). This is a pure limestone, often highly indurated, resistant to weathering and coarse in texture. Massive local patch reefs thrived on the highs, with well bedded, often chalky calcarenites being deposited in deeper water. Away from these magnificent exposures, facies relationships are often difficult to discern due to the karstic nature of surface exposures which are uniform in appearance. Pedley (1978) further subdivided the Tal-Pitkal Member as follows: a. Rabat Plateau Beds (oldest) which are limestones predominantly composed of coralline algal fragments and large recrystallised algal rhodoliths that form local limestone conglomerate beds (Fig. 4.7d), and these are overlain by the Depiru Beds that include patch reefs and biostromes (forereef deposits). b. Għadira Beds are youngest and include abundant oolitic limestone beds, although frequently the composition of the limestone is identical to the Depiru Beds. They are characterised by large-scale northeast prograding foresets. c. Għar Lapsi Beds are exposed locally on the hanging wall of the Magħlaq Fault and do not occur anywhere else on the island. A sequence of Upper Coralline Limestone beds is exposed on Filfla Island (about 4.5 km SSW of Ras Ħanzir) which is developed only locally (Furlani et al. 2019, Chap. 21). This may be a consequence of the ‘highly variable nature of the complex facies (that) confuses correlation’(Pedley et al. 1976, p. 334). The chalky limestones of the Tal-Pitkal Member are extracted for the production of aggregate at Ta’ Żuta (Fig. 4.7c). This limestone contains recrystallised patches and layers which yield first-class aggregate.

4.2.5.4 Ġebel Imbark Member The Gebel Imbark Member is interpreted as a shallow water to intertidal deposit, with subaerial events being represented

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Fig. 4.7 Exposures of Upper Coralline Limestone: a Upper Coralline Limestone exposed in a magnificent cliff section at Dingli (Malta), showing ginger coloured massive calcarenites of the Għajn Melel Member. The overlying rock members can also be seen. b Cliff section at Tal-Pitkal, Dingli, showing thinly bedded yellow algal limestone of

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the Mtarfa Member at the base succeeded by massive coarse limestone the Tal-Pitkal Member. c Hard stone Quarry at Ta’ Żuta (Siġġiewi, Malta) showing bedded tal-Pitkal Member. d Detail of the coarse massive limestone of the Tal-Pitkal Member (Rdum Depiru). e Thinly bedded limestone of the Ġebel Imbark at Baħrija (Malta)

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Sedimentary Evolution and Resultant Geological Landscapes

by white terrigenous clay beds. This member is only preserved as a thin unit sequence and is better preserved and protected from erosion on the downthrown blocks or hanging walls of grabens. Its base is marked by an erosion surface which is often deeply incised into the underlying tal-Pitkal Member. This unconformity is well exposed along the Dingli Cliffs at San Pawl tal-Pitkal and Imtaħleb (Fig. 4.7e), although the unit here is particularly thin. Inland, the exposure is limited but wherever it occurs, it often forms low conical hills which rise above the general level of the Upper Coralline Limestone plateau. This member is subdivided into two beds: the Tat-Tomna Beds and the Qammieħ Beds (Oil Exploration Directorate 1993a, b). The Tat-Tomna Beds are best preserved within the hanging wall of the major graben; however, a thin veneer also caps the culminations of the Rabat-Dingli plateau such as the Dingli Cliffs, showing that prior to post-Miocene erosion, it was likely to have been much more widespread. The overlying Qammieħ Beds are only preserved within hanging wall successions of major faults such as that at Qammieħ. They consist of an alternation of bioturbated beds up to 3 m thick and composed of wackestones, packstones and grainstones (Table 4.2) and 50 cm thick beds of pale grey to greenish yellow clays that contain plant debris. The unit is capped by a thick (over 1 m) stromatolite bed composed of laminated domes up to 60 cm high, suggesting intertidal or even supratidal conditions (Pedley 1978; Oil Exploration Directorate 1993a, b).

4.3

Quaternary Deposits

The Quaternary deposits of the Maltese Islands lie unconformably over older marine strata of Oligo-Miocene age and are usually easily distinguished by their brick-red colour. The deposits are fragmentary, mostly of continental origin, and tie in with the Quaternary record of SE Sicily (Pedley 2011). They are notable for their fossil mammalian fauna. These fauna migrated along the Malta–Sicily Plateau, which formed a land bridge between Malta and Sicily during the time of Pleistocene glaciations when sea level was lowered by around 120 m. Localities that contain substantial exposures of Quaternary deposits are found along the coastline of Marfa in locations such as Ċirkewwa; Wied Musa; Ta’ L-Imgħarrqa; Pwales Valley; Fiddien Valley; Wied Magħlaq; the Marsa Plain; St. Thomas Bay and Fort San Leonardo. Determining the topographic relief of the pre-Quaternary terrain of Malta is difficult as the youngest preceding marine deposits are almost 6 million years old (Pedley 2011). Tectonic activity led to the breakdown of the Late Miocene carbonate platform and development of a horst and graben

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structure in the Malta area and subaerial karstification (Galea 2019, Chap. 3). The Ġebel Imbark Member was virtually removed from the top of horsts by erosion (Pedley 2011).

4.3.1 Marine and Freshwater Lake Deposits 4.3.1.1 Raised beach deposits Marine Quaternary deposits are rare, and the only two known exposures are found at Ċirkewwa and Ta` L-Imgħarrqa (Fig. 4.8a) (Farres 2019, Chap. 12). The deposit at Ċirkewwa consists of 3 m of brick-red lithified coarse, well-graded calcareous sand with cross-laminations. Rhizoliths (calcification of soil around plant roots) are common, witnessing periods of emergence accompanied by the establishment of vegetation. It is underlain by about 2.5 m of thick brick-red continental deposits that contain land gastropods at the top, demonstrating a period of emergence and weathering prior to submergence when the beach deposit was generated. 4.3.1.2 Freshwater lake deposits The only deposit of freshwater origin is a highly porous travertine (i.e. tufa or calcareous tufa) which occurs in the Fiddien Valley (Fig. 4.8b) (Newberry 1968). Travertine, a freshwater limestone, is produced by precipitation of limestone from solution through the action of freshwater microscopic algae which, through photosynthesis, extract CO2, thereby enhancing the precipitation of CaCO3 (calcium carbonate). Due to the presence of leaves and stems during deposition, travertine is frequently rendered extremely porous and is often known as calcareous tufa, although the present-day convention is to designate all calcium carbonate on plant remains as travertine without reference to the porosity of the rock (Ford and Pedley 1996). The older fossil travertines that are used in the building industry are harder, more compact and much less porous because the original pores and cavities have been largely filled with calcite. The deposit is composed of lens-shaped beds at the base. These beds are rich in leaf imprints, stem moulds and thinly bedded leaf and gastropod bearing travertine. The abundance of leaf imprints and stem moulds indicate a freshwater palaeoenvironment of deposition. In common with the incision of deep gorges that are found in the Lower Coralline Limestone, the presence of this tufa demonstrates that the Maltese Islands once had a climatic regime which was characterised by much more abundant rainfall than occurs at the present day. The stream that runs along this valley is one of the few on Malta that is almost perennial, and the tufa could have formed in a freshwater lake made possible by the damming of the stream.

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Fig. 4.8 Examples of Quaternary deposits in the Maltese archipelago: a Bedded red beach deposits at tal-Imgħarrqa (Malta). b Bedded lake deposits at Fiddien. c Thick fanglomerate deposit at Wied Magħlaq (Malta) reported to contain extinct fossil Mammalian fauna. d Slope breccias on the southern slopes of Wied tal-Pwales (Malta). e Fossil sand dunes at Ramla Bay, (Gozo). f Għar Dalam solution cave at Birżebbuġa, containing a rich assemblage of extinct fossil mammals such as dwarf elephant, bear and deer

4.3.2 Continental Quaternary Deposits 4.3.2.1 Fluvial Conglomerates Fluvial conglomerates, together with other terrigenous sediments, presently fill the major channels of the Maltese drainage network mainly near to their points of discharge at the coastline. For example, conglomerates about 22 m in thickness have been recorded in the is-Simar–Pwales valley, where they are associated with a red terra rossa matrix, indicating deep incision of the underlying rock during marine regression. These fluvial sediments also fill the drowned river valley segments beyond the coastline.

4.3.2.2 Fanglomerates The alluvial fan deposits at il-Magħlaq are composed of poorly sorted gravel cobble and boulder conglomerates about 4 m thick, composed of Lower Coralline Limestone clasts and black limestone pebbles/cobbles, set in a red clay matrix (Fig. 4.8c). The source of the detritus is the Lower Coralline Limestone scarp situated at a short-distance inland. The deposits thicken seaward from an apex lying at the mouth of the il-Magħlaq valley. The alluvial deposits contain numerous gravel-filled channels with imbricated pebbles and calcified roots that are set in a palaeosol matrix (Farres 2019, Chap. 12).

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Sedimentary Evolution and Resultant Geological Landscapes

4.3.2.3 Slope talus agglomerates and breccias Slope talus agglomerates and breccias occur primarily in the Pwales and Mistra valleys and are associated with NE-SW faults that define the horst and graben structures (Fig. 4.8d). The best developed deposits are associated with fault segments exposing Blue Clay in contact with the Upper Coralline Limestone. 4.3.2.4 Aeolian deposits (sand dunes) The best examples of fossil Quaternary sand dunes in the Maltese Islands occur on the backshore of Ramla Bay, at the mouth of the Ramla Valley (Gozo) just behind the present beach (Fig. 4.8e). They attain a maximum height of several metres and cover much of the low-lying part of the valley. The dunes have been fixed by vegetation and support an endemic flora. They are composed of red-brown loose calcareous sand derived from the Għajn Melel Member of the Upper Coralline Limestone which caps the uplands of the valley. Blocks of this limestone have slid down the steep Blue Clay slopes into the sea at the southern promontory and are seen to be eroded by wave action. Long-shore currents carry the ample sand supply to the bay. As the supply of sand-sized grains remains abundant, dune building under the action of the prevailing north-westerly winds is still active. The dune morphology suggests transport towards the southeast and may reflect aeolian transportation during a lower sea level episode. 4.3.2.5 Cave and fissure fills The Quaternary cave and fissure deposits of the Maltese Islands are the most studied Quaternary deposits of Malta, because they yield a rich collection of mammals, birds and aquatic fauna, some species of which are extinct, while others are unknown among the present-day indigenous fauna

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of the islands (Cooke and Woodward 1893). The best known cave, the only one that has been preserved and which contains Quaternary continental deposits, is at Għar Dalam some 500 m from St. George’s Bay in Birżebbuġa (Despott 1916, 1923; Edwards 1935) (Fig. 4.8f). It is situated in a gorge cut in Lower Coralline Limestone. The cave consists of a main, almost straight gallery which runs at right angles to the gorge of Wied Dalam. It is about 120 m in length, about 18 m wide and 5 m high, with walls lined by stalactites and stalagmites. The deposits within the cavern owe their origin to periodic flooding, during which faunal remains were washed in and buried in muds deposited in the cave under climatic conditions which must have been very different from those of today. The fact that the entrance to the cave presently lies high above the stream channel shows that climatic episodes with higher rainfall than today occurred after the Pleistocene deposits were emplaced. Independent of any fluvial transport, however, the bone and sediment deposits could have easily been transported through open fissures and vents that connected the cave to the surface and not necessarily from the stream that flowed through the present-day gorge. The oldest cave deposits are of Lower Pleistocene age and contain Hippopotamus petlandii, Elephas melitensis and Elephas mnaidrae. Mammals dominated by Cervus sp and Myoxus melitensis are found in younger deposits (Cooke and Woodward 1893). From the St. Paul’s Bay Quaternary deposits, Cooke (1896) reports considerable quantities of land shells comprising: Helix aspersa, H. melitensis, H. vermicularis, Clausilia bidens, C. sulcatum, Rumina decollata and Cyclostoma melitensis. The Bengħisa and Magħlaq deposits have yielded Elephas falconeri, E. mnaidriensis and Hippopotamus pentlandi. Others sites have yielded limb bones of ruminants and horn cores of Cervus.

Fig. 4.9 Generalised cross section at San Leonardo showing the field relations of the Quaternary deposits with the underlying Globigerina Limestone

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4.3.2.6 Calcrete Calcrete crusts cover most of the limestone pavements and are associated with capillary rise and carbonate deposition during arid climatic episodes. Caliche crusts and globules are often associated with palaeosols such as those at Ċirkewwa (Farres 2019, Chap. 12). 4.3.2.7 Speleothems These commonly occur as stalactites and stalagmites in solution caverns. They are also common at the top of the Xlendi Member and the Ġebel Imbark Member in the form of lenses or strata of recrystallised limestone. 4.3.2.8 Marine high-stand deposits A thick limestone outlier, the San Leonardo beds, exposed at Fort San Leonardo were formerly attributed to the Ġebel Imbark Member of the Upper Coralline Limestone (Pedley 1978). However, Pedley (2011) has argued that in view of the lack of Miocene fauna in these beds and similarity with a similar-aged carbonate succession developed in the Syracuse area of Sicily, these deposits should be redefined as marine high-stand brackish and marine limestones deposited during the Calabrian Stage of the Pleistocene (defined as *1.8 Ma.–781,000 years ago ±5000 years) (Fig. 4.9). The San Leonardo Beds are underlain by an unconformity which though highly dissected is interpreted by Pedley (2011) as a marine abrasion surface. The San Leonardo Marine Abrasion surface extends westwards from beneath the limited outcrop of the San Leonardo Beds across Malta and Gozo. Pedley (2011) interprets this surface as marking an important early Quaternary marine high stand, currently at 70–80 m elevation, which occurred during the Calabrian Stage. Acknowledgments The author would like to thank Ms Sandra Mather for her cartographic assistance to produce the maps and profile drawings in this chapter.

References Abels HA, Hilgen FJ, Krijgsman W, Kruk RW, Raffi I, Turco E. Zachariasse WJ (2005) Long-period orbital control on middle Miocene global cooling: integrated stratigraphy and astronomical tuning of the Blue Clay Formation on Malta. Paleoceanography 20:4 Bellanca A, Sgarrella F, Neri R, Russo B, Sprovieri M, Bonaduce G, Rocca D (2002) Evolution of the Mediterranean basin during late Langhian—early Serravallian: an integrated paleoceanographic approach. Rivista Italiana di Paleontologia Stratigrafia 108 (2):223–239 Bennett SM (1980) Palaeoenvironmental studies in Maltese Mid– Tertiary Carbonates. Unpublished Ph.D. thesis, Univ. Lond. (Bedford College) 347p Catalano R, Infuso S, Sulli A (1995) Tectonic history of the submerged Maghrebian chain from the Southern Tyrrhenian sea to the Pelagian foreland. Terra Nova 7:179–188

S. Scerri Cooke JH (1896) Notes on the 'Pleistocene Beds' of the Maltese Islands. Geol Mag 32:201–210 Cooke JH, Smith-Woodward A (1893) The Għar Dalam cavern Malta. Proceed Royal Soc London 54:273–283 Dart CJ (1991) Carbonate sedimentation and extensional tectonics in the Maltese graben system. Unpublished Ph.D. thesis, University of London Despott G (1916) The excavations conducted at Għar Dalam (Malta) in July 1916. In: Report of the committee, Archaeological Investigations in Malta, Section H, British Association, Newcastle: 249–302 Despott G (1923) Excavations at Għar Dalam (Dalam Cave, Malta). Jl Roy Anthrop Inst 53:18–35 Dunham RJ (1962) Classification of carbonate rocks according to depositional texture. In: Ham WE Classification of carbonate rocks. American Association of Petroleum Geologists 1:108–121 Edwards WM (1935) In: Baldacchino JG (ed) Baldacchino JG Excavations at Għar Dalam. Ann Rpt Wkng Mus Dept, (for the year 1934–35) Malta Govt. Printing Office, Malta:17–19 Embry AF III, Klovan JS (1971) A Late Devonian reef tract on northeastern Banks Island, N.W.T. Bull Can Pet Geol 4:730–781 ERDF LIDAR data (2012) ERDF156 Developing national environmental monitoring infrastructure and capacity. Malta Environment & Planning Authority Farres P (2019) Palaeosoils: legacies of past landscapes, with a series of contrasting examples from Malta. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 141–152 Felix R (1973) Oligo-Miocene stratigraphy of Malta and Gozo. Meded. Landbouwhogesch. Wageningen 73(20):1–103 Ford TD, Pedley HM (1996) A review of tufa and travertine deposits of the world. Earth Sci Rev 41:117–175 Furlani S, Gauci R, Devoto S, Schembri JA (2019) Filfla: a case study of the effect of target practice on coastal landforms Stefano Furlani, Ritienne Gauci, Stefano Devoto, and John A Schembri. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 261–271 Galea p (2019) Central Mediterranean tectonics—a key player in the geomorphology of the Maltese Islands. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 19–30 Gauci R, Inkpen R (2019) The physical characteristics of limestone shore platforms on the Maltese Islands and their neglected contribution to coastal land use development. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 343–356 Gauci R, Scerri S (2019) A synthesis of different geomorphological landscapes on the Maltese Islands. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 49–65 Gauci R, Schembri JA (2019) From outcrops to maps: the birth of geological maps of the Maltese Islands in the 19th century - Part 2. Malta Map Soc J 1(4):40–47 Gianelli L, Salvatorini G (1972) I foraminiferi planctonici dei sedimenti Tertiari dell’arcipelago Maltese. Atti della Societa Toscana di Scienze Naturali, Memorie, Serie A 79:49–74 John CM, Mutti M, Adatte T (2003) Mixed carbonate-siliciclastic record on the North African margin (Malta). Coupling of weathering processes and mid Miocene climate. Geol Soc Am Bull 115 (2):217–229 Kienel U, Rehfeld U, Bellas S, Kohring R (1995) The Miocene Blue Clay Formation of the Maltese Islands: Sequence-stratigraphic and paleoceanographic implications based on calcareous nannofossil stratigraphy and calcareous dinoflagellate cysts. Berliner geowissenschaftliche Abhandlungen, Gundolf-Ernst-Festschrift E16:533– 557

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Sedimentary Evolution and Resultant Geological Landscapes

Lirer F, Iaccarino S (2011) Mediterranean Neogene historical stratotype sections and Global Stratotype Section and Points (GSSP). Annalen des Naturhistorischen Museums in Wien Serie A 113:67–144 Newbery J (1968) The perched water table in the Upper Limestone aquifer of Malta. J Inst Water Eng 22:551–570 Oil Exploration Directorate, Office of the Prime Minister (1993a) Geological map of the Maltese Islands, sheet 1 - Malta, scale: 1:25,000, resurveyed by Pedley HM, revised by Debono G, Scerri S, cartographer Simpson C. British Geological Survey, Keyworth Oil Exploration Directorate, Office of the Prime Minister (1993b) Geological Map of the Maltese Islands, sheet 2 – Gozo and Comino, scale: 1:25,000, resurveyed by Pedley HM, revised by Debono G, Scerri S, cartographer Simpson C. British Geological Survey, Keyworth

47 Pedley HM (1974) The Oligo-Miocene sediments of the Maltese Islands. Unpublished Ph.D. thesis University of Hull Pedley HM (2011) The Calabrian stage, Pleistocene highstand in Malta: a new marker for unravelling the late Neogene and quaternary history of the islands. J Geol Soc London 168:913–926 Pedley HM (HMSO, 1978) A new lithostratigraphical and palaeoenvironmental interpretation for the coralline limestone formations (Miocene) of the Maltese Islands. Overseas geology and mineral resources, H.M.S.O:54 Pedley HM, House MR, Waugh B (1976) The geology of Malta and Gozo. Proceed Geol Assoc 87:325–341 Scandone P, Patacca E, Radoicic R, Ryan WB, Cita MB, Rawson M, Chezar H, Miller E, McKenzie J, Rossi S (1981) Mesozoic and Cenozoic rocks from Malta escarpment (central mediterranean). AAPG Bulletin 65(7):1299–1319

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A Synthesis of Different Geomorphological Landscapes on the Maltese Islands Ritienne Gauci and Saviour Scerri

Abstract

The landscapes of the Maltese Islands owe much of their distinctive nature to their gentle dip to the NE. Imparted by tectonic uplift activity along the Medina Wrench Fault during the Pliocene, and accompanied by a breakup into a set of fault systems striking perpendicularly in a NE-SW direction, these landscapes are some of the most aesthetically striking landforms on the islands. Following this phase of major tectonic activity which gave birth to the Maltese Islands in the form of a tilted block, the onset of a NE-SW fault system broke northern Malta into a system of horst and graben features bounded by two master faults termed the Great Fault and the South Gozo Fault. A drainage pattern from NW to SE remodelled the horsts and graben into a ridge and trough system. At the coastline, the horsts gave rise to plateaux and headlands while the graben developed into rias and bays. Contrasting rock strata developed into the modern landscape which is characterised by gentle stepped slopes capped by a limestone plateau. The lowermost and uppermost exposed formations are composed of chemically pure limestone and gave rise to a well-developed surface and subsurface karst system. The former is composed of rugged limestone pavements and deep narrow gorges, while the subsurface drainage produced magnificent solution subsidence structures and a subsurface cavern system best developed in south Malta where it is rich in Quaternary fossil fauna.




Keywords

Horst Graben Maltese Islands




Fault




Limestone




Karst




R. Gauci (&)
S. Scerri Department of Geography, University of Malta, Tal-Qroqq, Msida, MSD 2080, Malta e-mail: [email protected] S. Scerri e-mail: [email protected] © Springer Nature Switzerland AG 2019 R. Gauci and J. A. Schembri (eds.), Landscapes and Landforms of the Maltese Islands, World Geomorphological Landscapes, https://doi.org/10.1007/978-3-030-15456-1_5

5.1

Introduction

Although they cover an area of only 316 km2 and reach a maximum height of little more than 250 m, the Maltese Islands show great diversity of relief and landforms. A detailed description of the geomorphology of the islands starts with the identification of a large number of regional divisions and numerous minor relief features which, though apparently insignificant when viewed on a map, have had decisive impacts on the human occupation of the islands. The landforms of the Maltese Islands are classical examples of landscape evolution in horizontal and sub-horizontal strata in semi-arid regions. In arid climates, where vegetation is sparse and the action of overland water flow especially effective, sharply defined landforms develop on horizontal sedimentary strata. A detailed description of the geology of the Maltese Islands has been provided in the previous chapter of this volume (Scerri 2019, Chap. 4). The Maltese Islands form the only late Cenozoic rock exposures in the central Mediterranean. For this reason, they are of particular interest for studies of late Tertiary plate tectonic movements as well as palaeoclimatic evolution and carbonate stratigraphy, making the islands of great interest to geologists and geomorphologists. In many ways, there is a close connection between the presence and type of lithology and resulting evolution of surface landforms. Table 5.1 summarises the key events which have shaped the present geomorphological landscapes of the Maltese Islands.

5.2

Structural Regions of the Maltese Islands

In terms of structural geology, the Maltese Islands are usually divided into three main structural regions (House et al. 1961; Pedley et al. 1976, 1978): a. The North Malta Graben: this region is characterised by a distinctive sequence of ridge-trough morphology, north 49

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Table 5.1 Landscapes and landforms of the Maltese Islands: a tectonic and geological timeline Time

Event

Resultant landscape development

Late Oligocene 25MA

Deposition of the Lower Coralline Limestone

This is a pure limestone and forms magnificent sheer vertical cliffs that make up the SW coastline of Malta, and about 75% of the coastline of Gozo. Amongst these, the Ta’ Ċenċ Cliffs are the highest at 140 m. Drainage incision has formed deep spectacular entrenched meanders like Wied Mġarr ix-Xini on Gozo, Wied il-Qirda and Wied Dalam on Malta. Within this formation are the largest solution caverns in South Malta such as Għar Dalam and Għar Ħasan which contain diverse extinct Quaternary mammalian fauna. This formation also hosts the spectacular solution subsidence structure at Dwejra and Qawra on Gozo and il-Maqluba on Malta

First evidence of tectonic activity on the Maltese Islands

Thin development of Lower Globigerina Limestone Member on the SW coast of Malta, in Northern Malta in general and at Ta’ Ċenċ (along the southern coast of Gozo). Subsidence and thick development of the Lower Globigerina Limestone Member south of the Great Fault. Extensive subsidence in the Valletta Basin and south of the Great Fault more generally

Burdigalian

Closure of the Mediterranean

No longer connected to the Indian Ocean and from this time seawater circulation was from the west

Langhian

Deposition of the Lower Globigerina Limestone Member

Deepening of the marine environment and the start of a new marine sedimentary cycle. Deposition of semi-homogeneous rock producing a undulating landscape which characterises Malta south of the Great Fault and western Gozo

Deposition of Middle Globigerina Limestone Member

Production of large circular bays in south Malta

Serravallian

Deposition of Blue Clay

Exposures of Blue Clay at sea level give rise to accelerated marine and gravitational-induced erosion which leads to undermining of the margin of the Upper Coralline Limestone plateau causing collapse and giving rise to a boulder scree which fringes the coastline. Hydraulic wave erosion of these boulders produces abundant calcareous sand supply which is transported to bays, so generating the most extensive sandy beaches in the Maltese Islands. Examples include: Ramla Bay on Gozo and Għajn Tuffieħa Bay on Malta

Early Messinian

Deposition of the Upper Coralline Limestone

Forms spectacular limestone cliffs on the south-west coastline of Malta

Messinian salinity crisis

Intensification of subaerial karst processes on exposed sea bed surfaces

The Mediterranean sea dries up repeatedly. Emergence of the Maltese Islands. Connected repeatedly to both Europe and North Africa during the desiccation events

Late Messinian Early Pliocene

Early rifting phase and break up of the Malta Horst

Formation of the North Malta Graben bounded in the south by the Great Fault and in the North by the North Gozo Fault. Accompanied by break up into a system of troughs (grabens) and ridges (horsts) oriented NE/SW, with drainage to the north-east. Generation of the sequence of horst and graben systems: Binġemma Syncline, Wardija Ridge, Pwales Trough, Bajda Ridge, Miżieb Syncline, Mellieha Ridge, Għadira Trough (isthmus), Marfa Ridge, South Comino Trough, Comino Horst and North Comino Graben

Middle Pliocene

Continued subsidence of the Pantelleria-Malta Trough System

Formation of the Magħlaq Fault: a NW-SE trending fault system with a throw of over 200 m By this time most of the Maltese geomorphic features are in existence, suggesting that much the present geomorphology is relict and generated under different climatic regimes than those obtaining at the present time

Quaternary late rifting phase

Glacial stades—connection of the Maltese Islands to southeast Sicily along a land bridge at least on two occasions during past glacial times (20 kya)

Formation of fossiliferous cave deposits. Formation of red continental deposits, sand dunes and limited freshwater lake deposits. Red continental Quaternary deposits are formed and cover pre-existing landforms. Final sea level rise and flooding of the river system (Micallef et al. 2013)

of the Great Fault and bounded by parallel ENE trending normal faults. The islands of Comino is included in this region (Fig. 5.1). b. The Malta Horst: this region is characterised by the presence of structural highs (such as plateaux and hills)

close to the Great Fault. To the centre, south and east, the Malta Horst is characterised by less structural deformations and faulting is generally much less pronounced. Valleys converge into the low-lying shores on the northeast. The dominant rock unit in these three areas of

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Fig. 5.1 Main structural regions of the Maltese Islands (inset map) and the location of the main sites discussed in this chapter. Map also shows the location of the line of topographic cross sections A-A’,

B-B’, C-C’, D-D’ and E-E’ and F-F’ which are illustrated respectively in Figs. 5.2, 5.5, 5.6 and 5.7 and discussed in the chapter. Source DEM map from ERDF LIDAR data (2012)

the Malta Horst is Globigerina Limestone. Along the lower sections of the valleys and closer to sea level, Lower Coralline Limestone is exposed (Fig. 5.1). c. The Gozo Horst: this region bounds the entire island of Gozo (Fig. 5.1).

cut into Lower Coralline Limestone (Fig. 5.2) in the east and Upper Coralline Limestone in the west. The scarp is best known for the Victoria Infantry Lines, which extend for about 12.5 km along the Great Fault and were strategically constructed around 120 years ago (Fig. 5.3). The height of the escarpment decreases towards the north-east where it places the Lower Coralline Limestone in structural contact with the Lower Globigerina Limestone Member (Fig. 5.2). In the area to the south of the Great Fault, the major topographic divisions are clearly marked. To the west, the Coralline Limestone plateaux stand at a height of between 200 and 240 m. These landforms give way eastwards— through an irregular Upper Coralline Limestone escarpment —and change into undulating low hills and plains,

The principal structural feature of the island of Malta is a well-defined corrugated escarpment, the Great Fault, which runs across the island from Fomm ir-Riħ to Madliena Tower in the north-east of Għargħur (Fig. 5.1). This precipitous escarpment, of up to 50 m high, separates the north and northwest region of Malta from the rest of its central and southern region (see Fig. 4.1 in Scerri 2019, Chap. 4). The scarp is interrupted by a number of deep valleys and gorges

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Fig. 5.2 Geological cross section A-A’, in a SE direction across the great faults, from Magħtab to Ġebel San Pietru Fig. 5.3 View of a segment of the Victoria Infantry Lines built during the British Period (1800– 1965) running along the Great Fault

developed on the less resistant Globigerina Limestone and, thus, lying for the most part below 150 m (Fig. 5.1).

5.2.1 The North Malta Graben The area north of the Great Fault shows the greatest topographic contrast in relief and landforms of the island,

containing both the steepest slopes and largest flat basins in Malta (Fig. 5.4). In this area, a major subdivision occurs along an irregular line running from St. Paul’s Bay to Mosta. This separates a western zone, where the Upper Coralline Limestone cap rock has been preserved almost intact, from a smaller eastern area from which it has been entirely removed. The eastern area is divided into two sections of roughly equal size. One comprises the low swell of the Għallis Hills

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Fig. 5.4 Horst and graben system in the northern part of Malta. Source Re-drawn and modified from Oil Exploration Directorate (1993)

and the Qawra peninsula with their summits standing at less than 80 m above sea level (Fig. 5.1). These topographic features are clearly defined and quite distinct from the broad, flat-floored, alluvial lowland of Wied il-Għasel and its tributary, the Wied ta’ Għajn Riħana (see Fig. 4.2 in Scerri 2019, Chap. 4). The latter region stretches nearly 3 km inland from Salina Bay and lies for the most part at heights below 15 m, being abruptly terminated at its southern end by the escarpment of the Great Fault. The remainder of northern Malta consists of a series of fault blocks and troughs which contrasts with the hummocky low-lying appearance of the southern part of the island (Fig. 5.1). From north to south, the major divisions are as follows: a. The Marfa Ridge and Peninsula: The Marfa Peninsula, which reaches a maximum height of 120 m in the west

(Figs. 5.1 and 5.4), has its steepest slope on the southern margin where it overlooks the Mellieħa Isthmus and Mellieħa Bay in an abrupt fault-line scarp, the height of which decreases from 120 m in the west to a little over 30 m at its eastern extremity. It is in fact a tilted fault block that slopes gently northwards to the Comino Channel. It is dissected by numerous small valleys all discharging to the north along the Marfa coastline. The island of Comino probably represents an exposed part of an otherwise submerged graben to the north of Marfa Ridge (Pedley et al. 1976). Comino has no marked watercourses because, in common with other karstic areas, drainage is subsurface. The eastern and western coastlines of the Marfa Peninsula expose Blue Clay and are marked by boulder fields and scree slopes, the latter produced by differential erosion and landslide processes (Soldati et al. 2019, Chap. 14).

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b. Mellieħa Valley (isthmus): The Mellieħa Isthmus is a compound feature in which northern and southern alluvial depressions—the l-Għadira and il-Ħofra, respectively—are separated by a low ridge of the Upper Coralline Limestone that reaches an altitude of 60 m near Ras in-Niexfa. Here two striking conical hills expose the Ġebel Imbark Member at the top, which is the youngest rock unit of the Upper Coralline Limestone. Bedding gives rise to stepped morphology. Narrow dry watercourses discharge northward into l-Għadira, a site where alluvial fans have been produced by discharge across the alluvial plain. This ridge/trough system extends to the Great Fault. c. Mellieħa Ridge: The Mellieħa Ridge is a north-dipping block (Fig. 5.5). Its major escarpment, in which the Blue Clay crops out, faces north over the isthmus and is breached by a series of narrow steep-sided valleys. These form deep incisions in the scarp face. The ridge is a limestone plateau with a summit level of 120–135 m, declining eastwards to 100 m or less in the Selmun tal-Blata region. The ridge is also notable for a number of sinkholes, the largest of which is found at Ġnien Ingraw. It is filled with terra rossa and limestone breccia. d. Miżieb Valley: This valley is a narrow plain some 550 m across and 3.5 km in length, with its lowest point about 30 m above sea level. It narrows to the east and gives way to the Wied tal-Mistra (Fig. 5.4; also Fig. 4.2 in Scerri 2019, Chap. 4), where headward erosion from the Qala tal-Mistra has exposed the Globigerina Limestone and Blue Clay and so produced a valley whose floor lies less than 15 m above sea level over a distance of 2 km.

R. Gauci and S. Scerri

The Miżieb depression is synclinal in structure and the southern limb forms the gentler, northern side of the Bajda Ridge (Sammut et al. 2019, Chap. 26). Typical of broad karst valleys, its margins are barren limestone pavements and its central part is covered by terra Rossa soils. e. Bajda Ridge: This is another Upper Coralline Limestone upland and stands at heights of between 60 and 80 m (Fig. 5.6). The ridge runs in E-W direction extending almost uninterruptedly from Ix-Xemxija to Ras il-Waħx and is marked by a number of low conical hills strikingly similar to those of the Mellieħa Isthmus and in the north and the Wardija Ridge further south, all of which expose the last remnants of the Gebel Imbark Member (Scerri 2019, Chap. 4). f. Pwales Valley: A minor escarpment 15–30 m high separates Bajda Ridge from the Wied tal-Pwales (Fig. 5.6c), which is a flat-floored depression—a graben—of about 1 km wide running right across the island from Għajn Tuffieħa to St. Paul’s Bay. The highest point in this area is only ca. 25 m above sea level and the greater part of the valley is below 15 m. With the exception of Burmarrad, this is the largest area of true lowland on the island. There is a marked contrast in geomorphic expression between the northern and southern border of this lowland. Whereas the former is a minor escarpment rising directly to a limestone upland, the slopes on the southern margin are longer and less steep, passing through a zone in which patches of Blue Clay occur before attaining the summit of the Wardija Uplands. In the east, the limestone pavement dips below sea level and is buried by thick red Quaternary

Fig. 5.5 Geological cross-section D-D’ in a SE direction, from Mellieħa ridge across Miżieb Basin to Pwales Valley illustrating the horst and graben sequence

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Fig. 5.6 a and b. Geological cross section E-E’ along Bajda Ridge illustrating the chain of low hills that characterise the ridges from Rdum Majjiesa to Dar il-Bajda. c N-S Geological cross-section F-F’, running

NW, across Wied tal-Pwales and Bajda Ridge illustrating the ridge-trough morphology of the North Malta Graben

alluvial and colluvial deposits with interbedding of thin black (peat) organic deposits. g. Wardija Ridge: The Wardija uplands are the largest area of limestone plateau north of the Great Fault and are more complex in detail than those already described (Fig. 5.4). They are bounded by two major strike-slip faults. They are tilted from north to south so that their northern face is fretted by a series of north–flowing valleys, which discharge into the Pwales valley, forming alluvial fans at the discharge points. These are now mostly masked by rubble wall terracing which bears

witness to intensive agricultural activity. They have also been vigorously dissected along their eastern edges where the deeply incised Wied Qannotta drainage system extends nearly to the Salina crossroads and divides the eastern part of the uplands into a northern and a southern ridge (see Fig. 4.2 in Scerri 2019, Chap. 4). The gently rolling landscape of these uplands is striking. A chain of low conical hills rises from these ridges with an aspect which is identical to those of Bajda Ridge, the highest of which reaches a height of 12 m above the average height of the ridge surface.

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h. Binġemma Valley: The dip slope of the Wardija Ridge leads southward to the Binġemma Basin: a flat-floored depression with a height of between 75 and 80 m. The axis of the Binġemma Basin, or syncline, can be traced from Ta’ L-Abatija in the west to Għajn Qattus in the east. It follows a course roughly parallel to the Great Fault and is considered to represent a solution subsidence structure. i. Ġnejna Valley: The Ġnejna valley forms an outlier of the western cliff regions, the main body of which lies south of the Great Fault on the seaward side of the coralline plateaux. In Ġnejna, vigorous erosion by two streams has exposed the Lower Globigerina Limestone Member to give a deep embayment in the western margin of the Upper Coralline Limestone. Due to faulting, part of the coastline exposes marls of the Middle Globigerina Limestone Member and marks the place where a sandy/shingle beach has developed.

5.2.2 The Malta Horst 5.2.2.1 Rabat-Dingli Plateau This plateau extends almost uninterruptedly in Upper Coralline Limestone from Is-Salib tal-Għolja in the east to the Great Fault in the west (Fig. 5.7). Beneath the seaward margins of the plateau lie the gentle Blue Clay slopes. On the surface, it is characterised by an almost barren and karstified limestone pavement rich in karren, solution caverns, shallow troughs and speleothems, bounded by a continuous sheer vertical cliffs. Drainage is mainly subterranean and true watercourses are not developed. The western edge of the plateau is fretted on all sides by deeply incised valleys which have cut into the uplands to give it an extremely irregular outline. The south-western margin has been least affected by such action as surface drainage is absent because of the general tilt to the NE. On the northeast margin of the Rabat-Dingli Plateau, there is a series of valleys carved by streams that descend to the central undulating plains such as Wied tal-Isqof and Wied is-Sewda (see Fig. 4.2 in Scerri 2019, Chap. 4). These valleys form deep depressions, their floors lying some 60 m below the plateax spurs which separate them. Spurs and valleys floors are connected by sweeping slopes developed on the Blue Clay and Upper Globigerina Limestone Member (Fig. 5.7b). The plateau itself is divided into two parts by a Blue Clay basin. The main lithologies exposed on the UCL surface of the Rabat-Dingli Plateau are Ġebel Imbark Member, tal-Pitkal Member and Mtarfa Member (Scerri 2019, Chap. 4).

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5.2.2.2 The Naxxar-Ghargħur Hills The Naxxar-Għargħur Hills are an important structural high (Fig. 5.1). Though forming part of the Globigerina Limestone area of Malta, they are sufficiently distinctive to warrant their inclusion as a major subdivision of the island in their own right. From their smooth and rounded summits at heights of 130–140 m, the land falls away in convex slope eastwards and southwards, to the coast and to the Lija-Msida valley, respectively. Several small valleys cut sharply into the surface and fan out to form a radial drainage pattern (see Fig. 4.2 in Scerri 2019, Chap. 4). 5.2.2.3 The Central, Southern and Eastern Areas The central, southern and eastern regions of the Malta are mostly areas of low relief and gentle structural folding. It is a landscape carved primarily where Globigerina Limestone crops out, to produce low ridges and valleys. Level land is very limited in extent and occurs only around the head of Marsa Creek, at Ta’ Qali and at Luqa airport. The terrain is, however, far from being featureless and steep slopes occur in a number of places. A series of ridges and valleys leave the coralline plateaux of the west and the hilly lands of the south to converge towards the drowned valleys of Marsamxett and Grand Harbour (Fig. 5.1; Schembri and Spiteri 2019, Chap. 6). The Naxxar-Għargħur Hills are, thus, succeeded southwards by the Lija-Msida Valley which in turn gives way to the low upswelling of the Attard-Ħamrun Ridge. In turn, this falls away to the open valley of the Wied is-Sewda, bounded in the south by the Żebbuġ Ridge. In their upper courses, these valleys form gentle depressions rather than well-marked troughs but, where they converge in Wied il-Kbir complex in Lower Coralline Limestone, they are sharply incised to depths of 30 m or more below the general level before they open out into the alluvial Marsa lowland (see Fig. 4.2 in Scerri 2019, Chap. 4). It is again notable that the change in relief generated by the river system in passing from Globigerina Limestone to Lower Coralline Limestone is remarkable. It produces broad valleys in the Globigerina Limestone and deep gorges and entrenched meanders in the Lower Coralline Limestone. In the south, Wied il-Għajn and Wied Sant’ Antnin converge towards Marsaskala Bay (see Fig. 4.2 in Scerri 2019, Chap. 4). Further south, ridges and valleys also converge towards Marsaxlokk. This arrangement gives an undulating character to the area, and steep slopes are confined to the coasts of Żonqor and Delimara, and the Wied Ħas-Saptan and Għar Dalam (see Fig. 4.2 of Scerri 2019, Chap. 4). The latter valleys are both deeply incised into the Lower Coralline Limestone and form spectacular incised meanders. A second fault trend can be seen in the south-western regions of Malta and exposes the Magħlaq Fault system

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Fig. 5.7 a Geological cross section B-B’ in NE direction from Rabat-Dingli Plateau showing steep high cliffs. Note the decrease in thickness of the plateau in a NE direction b Geological cross-section

C-C’ across the NE margin of the Rabat-Dingli Plateau showing low cliff blending into the gently rolling hills of the Globigerina Limestone

that consists in part of two closely spaced parallel faults and which run WNW-ESE along Malta’s south-west littoral (see Fig. 4.2 of Scerri 2019, Chap. 4). The rifting is associated with the NW-SE-trending Pantelleria Rift system which created the Magħlaq Fault and caused the western side of Malta thrust upwards (Galea 2019, Chap. 3). The result is a striking contrast between the south-west coast featuring sheer cliffs of a rectilinear aspect over 200 m in height near Dingli and low-sloping rocky coasts on the north-east shores of the island. The same fault is also responsible for the plunging cliffs from Bengħisa up to Fawwara in Malta and

for disconnecting the islet of Filfla from the mainland due to land subsidence (Furlani et al. 2019a, Chap. 21).

5.2.3 The Gozo Horst The island of Gozo is characterised by a gentle regional dip to the north, which caused the Lower Coralline Limestone to develop into vertical cliffs over 120 m high along the south-west coast falling to just over 20 m above sea level on the northern coast between Marsalforn and San Blas Bay (Pedley et al. 1976, 1978). The two main faults in Gozo are

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Fig. 5.8 Geological map of Gozo, showing the gradual E-W decrease in size of the Upper Coralline Limestone Plateaus. Source Re-drawn and modified from Oil Exploration Directorate (1993)

the Sannat Faults and Qala Faults and which are located close to Mġarr ix-Xini in southern Gozo (Fig. 5.8). Structurally, they separate south-eastern Gozo from the rest of the island (House et al. 1961). Though covering little more than one-third of the area of the main Island, Gozo, is topographically more varied than Malta (Fig. 5.1). Three main features dominate the landscape as follows: a. Fragmented mesas of the Upper Coralline Limestone (Fig. 5.8). b. Low-lying plains and hills that have developed on the Globigerina Limestone. Between the two there are sweeping slopes which mark outcrops of the Blue Clay. c. Low-lying flat-topped hills, locally known as il-Mejda, where complete erosion of the Blue Clay exposed the planar top of the Upper Globigerina Limestone Member.

In the northern half of the island, erosion has divided the Upper Coralline Limestone plateaux into a series of disconnected fragments which diminish in size, but increase in height from east to west (Fig. 5.8). The largest of these, the Nadur and Xagħra plateaux, each cover an area of more than 6.5 km2 and rise to heights of 120–135 m, thus occupying the bulk of the north-eastern part of the island. These uplands, like their counterparts in Malta, are penetrated by numerous, sharply incised valleys, with slopes and floors developed on the Blue Clay. Whereas drainage is predominantly to the north in Malta, on Gozo relatively large watercourses drain to the east, south and west and, therefore, the drainage assumes a roughly parallel pattern in the north and a radial pattern in the south (Fig. 5.1; Fig. 4.2 in Scerri 2019, Chap. 4). These streams include: the Wied ta’ Daħlet Qorrot; San Blas and the eastern tributaries of the Wied ir-Ramla, in the

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case of the Nadur plateau. The Xagħra plateau is cut into two by Wied tal-Pergla and the eastern tributaries of the Wied ta’ Marsalforn (see Fig. 4.2 in Scerri 2019, Chap. 4). Where these two uplands reach the coast, ‘rdum’ areas develop and Blue Clay slopes descend steeply to the sea from beneath bluffs that mark the edge of the limestone outcrop. In the far north-east, however, between Daħlet Qorrot and Ras il-Qala, the slope down to the sea is less steep and a rocky platform has developed where the Lower Coralline Limestone is exposed in a narrow belt along the coast. The Wied ir-Ramla, which separates the Nadur and Xagħra Uplands, is a wide-open valley whose gently sloping floor contrasts with the steeper slopes which mark its upper edge and the narrow enclosed valleys mentioned above (see Fig. 4.2 in Scerri 2019, Chap. 4). This valley terminates at the coastline by an extensive sandy beach that has been produced by accelerated erosion of Blue Clay slopes and overlying brown Għajn Melel Limestone Member large boulders which can be seen at the head of the bay. These friable boulders produce an abundant source of lime sand at the coastline which is transported to the bay by longshore currents. The rock sequence is marked by the absence of the Middle Globigerina Limestone Member marls and the characteristic stepped morphology of the Upper Globigerina Limestone Member in the valley’s interior. West of Wied ta’ Marsalforn, small and scattered fragments are all that remain of the Upper Coralline Limestone plateau. The north-western part of Gozo is essentially an undulating plain of Globigerina Limestone into which the valleys are for the most part not sharply cut and above which clay slopes lead to the numerous mesas. These, though small in surface area, are an impressive feature of the landscape, standing as they do 45 m or more above the general level of the surrounding plains. The largest plateau is in Żebbuġ, about 1.6 km long and 120 m across at its widest point. The Żebbuġ upland stands more than 150 m above sea level and is bounded on its east by the Wied tal-Qlejgħa and on its west by the Wied il-Għasri, the two largest valleys of north-western Gozo (see Fig. 4.2 in Scerri 2019, Chap. 4) West and north of Żebbuġ-Kercem-Ras id-Dwejra area, the Globigerina Limestone plains rise gently to heights of 90–120 m along the western coast where cliffs descend to the sea in a sheer drop close to 100 m. In this region, numerous mesas such as Ġordan and Għammar occur, all standing more than 150 m above sea level. The valleys of the Wied il-Għasri, Wied il-Mielaħ and Wied ir-Raħeb (see Fig. 4.2 in Scerri 2019, Chap. 4) are broad, open and gently sloping exposing the Globigerina Limestone, with the exception of the lower courses where over short distances, streams have exposed and cut deeply into the Lower Coralline Limestone to form spectacular deep gorges. In the Qawra-id-Dwejra area, solution subsidence has led to the formation of a deep trough which separates

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north-western Gozo from the hills of the south-west. The latter reaches a maximum height of 160 m near Ras il-Wardija and fall away eastwards to the outskirts of Kerċem. The southern coastal area between the last-named valley and the Wied Mġarr ix–Xini (see Fig. 4.2 in Scerri 2019, Chap. 4) is a second region in which uplands, in this case rising a little above 150 m, are bounded on the south by a line of cliffs that fall away gently northwards to the central plains. East of Sannat, however, Ta’ Ċenċ is a well-marked fault-line scarp of ca. 15 m high, along which a narrow outcrop of the Lower Coralline Limestone occurs and overlooks the central plains. East of Mġarr ix-Xini, the morphology of the southern coast changes. Inland, faulting has preserved a large area of the Upper Coralline Limestone, beneath which the Blue Clay outcrops to form the seaward slopes. The Żebbuġ-Rabat basin west of Rabat (Gozo) is drained by the upper reaches of the Wied ta’ Marsalforn from the Qasam San Ġorġ basin to the Wied ix-Xlendi (see Fig. 4.2 in Scerri 2019, Chap. 4). These basins, whose lowest points are 75 m and 50 m, respectively, rise gently to low cols on which the villages of Għasri and Santa Luċija stand. Rabat is sited on a low elevation of the Upper Coralline Limestone, flanked on its eastern side by a minor escarpment beneath which unusually gentle clay slopes occur. The area between Rabat and Għajnsielem is an undulating region lying at heights between 80 and 100 m. The Xewkija-Għajnsielem ridge, which is fault-bounded on its southerly steeper side, is a recognisable topographic feature which slightly rises above the general level of the area (Fig. 5.4). The ridge is flanked on either side by plains of which the one to the north is more uniform. No topographic break occurs where, to the east, faulting has preserved the Upper Coralline Limestone. The central plains continue unchanged across the structural boundary until they come to sea level close to Mġarr Bay.

5.3

Main Landforms

The connection between geological formation and geomorphological processes has resulted in the creation of the following main landforms: a. Upper Coralline Limestone (UCL) plateaux (Fig. 5.9a) and cliffs: these landforms form the highest and most prominent areas and are bounded by well-marked sheer vertical cliffs or escarpments up to ca. 40 m in height. These uplands range in size from the massive triangular Rabat–Dingli plateau to the tiny pinnacles of north-western Gozo. Landforms on UCL are similar to those on the oldest limestone stratigraphy, the Lower Coralline Limestone (LCL) because it forms high

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Fig. 5.9 Major geomorphological landscapes across the Maltese Islands: a Upper Coralline Limestone plateau, with scree slopes at the sea level at Marfa Ridge (Malta). b Globigerina conical hills cut from Rabat-Dingli Plateau by Wied ir-Rum and Wied Miġra Ferħa,

R. Gauci and S. Scerri

locally known as Ras id-Dawwara (Malta). c Lower Coralline Limestone cliffs along Maghlaq south-west coastline (Malta). d Flat foor-basin at Pwales (Malta). e Circular solution subsidence at Dwejra (Gozo). f Meandering valley gorges of Wied il-Għasri (Gozo)

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b.

c.

d.

e. f.

g.

h.

i.

A Synthesis of Different Geomorphological Landscapes …

plunging coastal cliffs in western Malta and inland karst topography such as that found in east-central Gozo. Globigerina Limestone (GL) hills and plains: this stratigraphy forms large areas of gently sloping land, which on Malta take the form of a series of low ridges and relatively broad shallow valleys, but have a more varied, though none-the-less subdued, topography on Gozo (Fig. 5.9b). The softer GL which overlies the Lower Coralline Limestone forms a broad gentle topography in central parts of Malta. High coastal limestone cliffs in Lower Coralline Limestone: they form the south-west coastline (Fig. 5.9c) of Malta. As the oldest rock formation, the LCL responsible for the sheer cliffs on the west coasts that rise up to 140 m, and deep valley gorges and entrenched meanders further inland. Blue Clay inliers or interior depressions: these are produced by extensive karstification of the central region of the UCL plateau. This region is drained by the upper Wied Qlejgħa and its tributaries: Wied Għomor; Wied Għemieri; Wied il-Busbies and Wied Liemu which converge towards the narrow outlet north-east of Fiddien Bridge (see Fig. 4.2 in Scerri 2019, Chap. 4). These streams are also accompanied by subsurface drainage. Blue Clay slopes: these slopes separate the plateau surfaces from the surrounding lowland areas. ‘Rdum’ or scree slopes: ‘Rdum’ (in Maltese language) occur where the Upper Coralline Limestone plateaux meet the underlying Blue Clay (Fig. 5.9a). The impervious Blue Clay is evident in the scree-slope areas of western Malta and eastern Gozo. The softening and resultant downslope movement of the Blue Clay undermines the margins of the overlying Upper Coralline Limestone. Deep cracks and disconnected slabs are created through shear failure of the UCL. UCL slabs subsequently slide downhill over the Blue Clay slopes in a gravitational-induced process and come to rest on the Upper Globigerina Limestone or else deposited at the shoreline (Soldati et al. 2019, Chap. 14). Flat-floored basins: These basins are, in most cases, the result of faulting (e.g. Wied tal-Pwales Fig. 5.9d) or solution subsidence (e.g. Binġemma Basin), but which are sometimes due to erosion and subsequent alluvial deposition (e.g. Burmarrad-Wied il-Għasel). A considerable number of circular or elliptic solution subsidence structures (Fig. 5.9e) such as il-Maqluba (Malta) and Dwejra (Gozo) (Calleja and Tonelli 2019, Chap. 11). Deep meandering gorges cut into the Lower Coralline Limestone (Fig. 5.9f): In contrast to the overlying Globigerina Limestone where weathering and mass movements generate broad valleys and gentle relief watercourses, the Lower Coralline Limestone drainage

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has produced deep entrenched meanders and gorges. The Lower Coralline Limestone is chemically pure and the predominant geomorphological process is solution which acts predominantly along watercourses. The coast exhibits a great variation in relief in response to the hydraulic wave action, but cliffs are predominantly high south of the Great Fault and reach a maximum height of 120 m at Dingli. The same rock formation marks the predominantly high coastline of Gozo where sea cliffs reach a height of 140 m.

5.4

Coastal Landforms

Amongst the most representative and scenic landscapes of the islands, many are primarily coastal. Faulting, tectonism, geology and sea level change have determined the configuration of the coastlines of the Maltese Islands (Galea 2019, Chap. 3; Scerri 2019, Chap. 4; Schembri and Spiteri, Chap. 6; Prampolini et al. 2019, Chap. 10). Despite their small size, the Maltese Islands exhibit coastlines which are diverse and complex in their evolution and display a myriad of structural, gravitational, aeolian, fluvial, marine and karstic landforms. The coastal landforms of the Maltese Islands may be subdivided into the following seven geomorphic types: a. Low-rocky coast: Low-sloping rocky shores, with features such as pools and pinnacles may be found mainly along the north-eastern margin of Malta and that of northern Gozo. Chemical and biological weathering of the Lower Coralline Limestone create a highly rugged irregular topography such as at Baħar iċ-Ċaghaq (Malta). Additionally sloping coasts, in the highly fractured Lower Globigerina Limestone, provide the best geo-dynamic setting from where large boulders get dislodged during storms to create coastal boulder fields. Boulder coasts may be found interspersed in various places along the north-eastern coasts of Malta such as at L-Aħrax (Mottershead et al. 2019, Chap. 22), Buġibba, Pembroke, Qawra, Żonqor (Fig. 5.10a), and Xgħajra (Causon Deguara and Gauci 2017; Causon Deguara and Scerri 2019, Chap. 19). b. Rias or drowned valleys: during the late Pleistocene, sea level was ca. 120 m below the present level. The river system generated at that time extended four kilometres out on to the continental shelf (Prampolini et al. 2019, Chap. 10). Following the melting of the ice, sea level rose and the valleys extending across the continental shelves were drowned. Drowned valleys now form natural harbours (i.e. they are ‘ria’ coastlines) and are best exemplified by the Grand and Marsamxett Harbours (Schembri and Spiteri 2019, Chap. 6), Marsaskala and

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Fig. 5.10 Diverse coastal landforms on the Maltese Islands: a Low-sloping bouldered rocky beach at Żonqor (Malta). b Għadira saline marshland at Mellieħa Bay (Malta). c Blue Clay slopes with an Upper Coralline Limestone plateau at Ġnejna Bay (Malta). d Ramla

R. Gauci and S. Scerri

Bay in Gozo. e Upper Globigerina Limestone Member cliffs at Ħofra il-Kbira in Xrobb l-Għaġin (Malta). f Dragonara blowhole at L-Aħrax (Malta)

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Marsaxlokk Bay in the south-east and Wied Babu at Żurrieq in the south-west. Good examples in Gozo are Mġarr ix-Xini, Xlendi and Wied il-Għasri (see Fig. 4.2 in Scerri 2019, Chap. 4). In a restricted number of locations, drowned valleys provided an additional setting for saline marshlands to develop. Encouraged by the presence of both sheltered water and a large and continuous supply of fine material (which could be alluvial deposits or simply mud and silt brought onshore by waves), these landforms thrived in a unique endemic ecological landscape (Lanfranco et al. 2019, Chap. 20). Examples include Għadira in Mellieħa Bay (Malta) (Fig. 5.10b) and il-Magħluq in Marsaskala (Malta). c. ‘Rdum’ (or scree slopes): From Fomm ir-Riħ to Ċirkewwa (Malta), the coastline consists of ‘rdum’ morphology, where Lower Coralline Limestone boulders break off from overlying plateaux and then topple and slide down over the Blue Clay and Upper Globigerina Limestone to reach shoreline levels along the coastline (Fig. 5.10c). In addition, rainwater percolates through fissures in the limestone and reaches underlying clay. This causes the Blue Clay to become unstable. Jointing and faulting in the Upper Coralline Limestone cause the latter to dislodge and eventually break up, falling on to the clay slopes (Devoto et al. 2012; Soldati et al. 2019, Chap. 14). The result is a coastline fringed with boulder fields detached from the Upper Coralline Limestone uplands, and larger landslides at the foot of the scarp faces such as those of Rdum id-Delli, Ras il-Waħx and il-Qarraba (Malta). d. Beaches (sandy, shingle and bouldered beaches: Depositional beaches represent a minor proportion of the coastline (2.4%) and are typified by a ‘pocket’ morphology. Sandy beaches are more abundant than shingle beaches, making up, respectively, 2.2 and 0.2% of the total coastline (Gauci et al. 2005; Sammut et al. 2017, 2019, Chap. 16; Zammit Pace et al. 2019, Chap. 18). Maltese beaches are mostly located in sheltered areas between boulder-strewn coastlines, where marine longshore currents deposit sufficient material to form sandy or shingle beaches. Examples of such beaches are Ramla Bay (Gozo) (Fig. 5.10d) and Għajn Tuffieħa Bay (Malta) (Zammit Pace et al. 2019, Chap. 18). Partly submerged graben has also produced shallow bays in north-east Malta that are bounded by promontories which correspond to the horsts. The sequence of ridges-troughs in the North Malta Graben has frequently placed the Blue Clay within reach of wave action, producing fine silted sandy bays at the graben (e.g. Għadira Bay, Malta). Interestingly, in Gozo only one beach (Ramla Bay) interrupts the stretch of ‘rdum’ coastline from the eastern promontory of Marsalforn Bay to Daħlet Qorrot, and it is also the location where the contact between the Blue Clay/Upper

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Globigerina Limestone Member is at or close to sea level. On a restricted number of these beaches, mainly in northern and north-western Malta, Gozo and Comino, remnants of aeolian landforms such as sand dunes may be found. Beaches in Malta include: Għadira (Mellieħa Bay); Ramla tat-Torri; Little Armier; Ramla ta’ l-Armier; Ramla tal-Bir; Ramla tal-Mixquqa and Ġnejna Bay (Zammit Pace et al. 2019, Chap. 18). On Comino, sand dunes are found at Santa Maria Bay and in Gozo the largest sand dune system in the Maltese Islands is at ir-Ramla l-Ħamra. e. Cliffs: Steep cliffs, ranging between 30 and 120 m in height represent almost half of the length of the Maltese coastline (Paskoff and Sanlaville 1978). They characterise western and south-western Malta, eastern Comino and most of the coast of Gozo. Vertical plunging cliffs in Malta are generally cut into the Lower Coralline Limestone and they are found from Wied ix-Xaqqa in the south east to Fomm ir-Riħ in the south-west. At Għar Lapsi, the Magħlaq Fault exhibits a slickensided fault plane which downthrows the Upper Coralline Limestone to the south by at least 230 m (Pedley et al. 1976, 1978). Thus, this stretch of high relief coast is interrupted by low-lying coastlines at Għar Lapsi and at il-Magħlaq, where the Magħlaq Fault has downthrown the Upper Coralline Limestone to sea level. The southern edge of this region falls to the sea in a line of cliffs only slightly less impressive than those further to the west. While the cliffs themselves are rarely more than 30 m in height, they are backed by steep slopes rising to a crest line which runs parallel to—and less than 2 km from—the coast. The height of this crest line descends eastwards from a maximum of 140 m to about 50 m at Bengħisa Point (Malta). On Gozo, the major part of the coastline from Mġarr ix-Xini in the east, going clockwise to Ta’ Ċenċ, Pinu Point and Wied il-Għasri, is mostly made up of shear vertical cliffs exposing the Lower Coralline Limestone. f. Semicircular coves: Karst processes play an important role in the Maltese archipelago due to the extensive presence of limestones. This has favoured the development of an interesting karstic system on the islands and the surrounding submarine area. The Maltese coastline is indented by numerous features; some of the most remarkable are the semicircular coves which, according to their origin, fall into four groups (Paskoff and Sanlaville 1978): i Solution subsidence structures—karstic solution subsidence structures invaded by the sea such as the Dwejra and Qawra circular structures (Gozo) (Calleja and Tonelli 2019, Chap. 11) and the Blue Grotto on Malta (Furlani et al. 2019b, Chap. 25); ii Boulder ‘amphitheatres’—Elliptic coves formed by wave action and accelerated erosion of the Blue

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Clay overlain by the Upper Coralline Limestone. The result is an elliptic structure formed by boulder fields which glide down over the Blue Clay and evolve in the shape of an ellipse such as at Paradise Bay on Malta; iii Erosional circular coves—These coves are formed by differential erosion of monoclinal structures such as il-Ħofra l-Kbira and il-Ħofra ż-Żgħira, located along the Delimara (Malta). Their origin is due to the combined effects of wave action on gently dipping Middle Globigerina Limestone marls at sea level overlain by more competent limestone of the Upper Globigerina Limestone Member. The carving of the coves is initiated by wave action at a fracture normal to the coastline; and iv Fault-bound circular coves—Some structural conditions at the coastline may also lead to the formation of small circular coves. At Tal-Imgħarrqa in Għadira Bay, the Upper Coralline Limestone at the coastline is juxtaposed against the soft Globigerina Limestone. Wave action breaking through fractures in the Upper Coralline Limestone erodes easily the in-lying Globigerina Limestone which is then enlarged in the form of a circular cove. g. Shore platforms: Where cliffs are cut in the Globigerina Limestone, such as the cliff line between Marsaxlokk Bay (Malta) and St. Thomas Bay (Malta), shore platforms have developed as a result of differential erosion at the contact between different lithologies. The shore platform at Miġnuna Point (Marsaskala, Malta) corresponds to the Lower Globigerina Limestone Member (LGLM) overlain by relatively more resistant beds in hardground and conglomerate and above these beds; there is the softer Middle Globigerina Limestone Member (MGLM) (Gauci 2018; Gauci and Inkpen 2019, Chap. 27). Wave action eroded the marls of the MGLM at a relatively faster rate. The resultant recession of the MGLM marls produced a shore platform corresponding to the underlying lithological units in hardgrounds, conglomerate and LGLM (Gauci and Inkpen 2019, Chap. 27). Similar shore platforms are located at Xwejni Bay (Gozo) (Gauci et al. 2017) and at Qammieħ Point (Malta). Shore platforms also evolve in Upper Globigerina Limestone Member (UGLM), with the relatively more resistant yellow bed of the UGLM left exposed after the retreats of the overlying yellow marl layer from the same member. Examples of shore platforms in UGLM can be found in Delimara, Selmun (Sammut et al. 2019, Chap. 26) in Malta and Għar Qawqla in Gozo (Gauci and Inkpen 2019, Chap. 27). Less common are shore platforms at the foot of the high coastal cliff in the Lower Coralline Limestone (LCL) such as at Maddalena and Buxieħ at Dingli, at Għar Ħasan in Birżebbuġa and Żonqor in Xgħajra. These LCL platforms are

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associated with a gently dipping soft bed in LCL and in the case of Żonqor, with also the recession of overlying Lower Globigerina Limestone Member (LGLM) (Causon Deguara and Scerri 2019, Chap. 19; Gauci and Inkpen 2019, Chap. 27). Wave action in the softer LCL beds easily produces undermining and collapse of the overlying LGLM producing a shore platform as the cliff face recedes. LCL platforms extend to the point where the soft bed is high enough and no longer within reach of storm waves. Beyond this point, there is no undermining and shore platform development comes to an end. h. Sea caves: Sea caves are very common along the coastline wherever there is a steeply dipping fracture or a fault. Wave action on the rock weakened along the joint or fault plane enlarges the feature until it forms a large circular cave. In the presence of horizontal bedding, the cave may reach 30–40 m in width. In some instances, the roof of the cave has collapsed producing a large blowhole, which is known locally as ‘dragonara’. The most spectacular one lies at L-Aħrax on the eastern coast of Marfa Ridge (Fig. 5.10f). Other well-known sea caves are to be found along the coast Blue Grotto near the village of Żurrieq in the south of Malta (Furlani et al. 2019b, Chap. 25).

5.5

Conclusion

Despite the small size of the islands, the Maltese Islands not only have a distinctive topography, but also a rich variety of contrasting landscapes. In addition, the physiography of the islands is enhanced by irregular surface features, which lend character to an otherwise monotonic environment. On the same note, but at a different measure, the coastal features provide a wide range of morphologies at various scales offering again a high density and diversity of landforms. Combined together, the coastal features present the perfect foil for the appreciation, use and utilisation of the geomorphological landscape. Acknowledgements The authors would like to thank Ms. Sandra Mather for her assistance to redraw the maps and profile drawings in this chapter.

References Calleja I, Tonelli C (2019) Dwejra and Maqluba: emblematic sinkholes in the Maltese Islands. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 129–139 Causon Deguara J, Gauci R (2017) Evidence of extreme wave events from boulder deposits on the south-east coast of Malta (Central Mediterranean). Nat Hazards 86(Suppl 2):543–568

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Causon Deguara J, Scerri S (2019) Ras il-Ġebel: an extreme wave-generated bouldered coast at Xgħajra. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 229–243 ERDF LIDAR data (2012) ERDF156 Developing National Environmental Monitoring Infrastructure and Capacity. Malta Environment & Planning Authority Devoto S, Biolchi S, Bruschi VM, Furlani S, Mantovani M, Piacentini D, Pasuto A, Soldati M (2012) Geomorphological map of the NW coast of the Island of Malta. J Maps 8:33–40 Furlani S, Gauci R, Devoto S, Schembri JA (2019a) Filfla: a case study of the effect of target practice on coastal landforms. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 261–271 Furlani S, Gauci R, Biolchi S (2019b) Sea caves and coastal karst scenery along the Maltese coasts: the case study of Blue Grotto. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 317–324 Galea P (2019) Central Mediterranean tectonics—a key player in the geomorphology of the Maltese Islands. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 19–30 Gauci R (2018) The identification and quantification of surface change on limestone shore platforms of the Maltese Islands. Unpublished Ph.D. thesis, University of Portsmouth, United Kingdom Gauci R, Schembri JA, Inkpen R (2017) Traditional use of shore platforms: a study of the artisanal management of salinas on the Maltese Islands (Central Mediterranean). SAGE Open 7(2):1–16 Gauci R, Inkpen R (2019) The physical characteristics of limestone shore platforms on the Maltese Islands and their neglected contribution to coastal land use development. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 343–356 Gauci MJ, Deidun A, Schembri PJ (2005) Faunistic diversity of Maltese pocket sandy and shingle beaches: are these of conservation value? Oceanologia 47(2):219–241 House MR, Dunham KC, Wigglesworth JC (1961) Geology and structure of the Maltese Islands. In: Bowen-Jones H, Dewdney JC and Fisher WB (eds) Malta: background for development, University of Durham, pp 24–33 Lanfranco S, Galea L, Colen TV (2019) Saline marshlands of the Maltese Islands. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 245–259 Micallef A, Foglini F, Le Bas T, Angeletti L, Maselli V, Pasuto A, Taviani M (2013) The submerged paleolandscape of the Maltese Islands: morphology, evolution and relation to Quaternary environmental change. Marine Geology 335:129–147

65 Mottershead D, Bray M, Causon Deguara J (2019) Tsunamigenic Landscapes in the Maltese Islands: The Comino Channel Coasts. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 273–288 Oil Exploration Directorate, Office of the Prime Minister (1993) Geological Map of the Maltese Islands, Sheet 1 and 2 –Malta, Gozo and Comino, scale: 1:25,000, resurveyed by Pedley HM, revised by Debono G, Scerri S, cartographer Simpson C. British Geological Survey, Keyworth Paskoff R, Sanlaville P (1978) Observations géomorphologiques sur les côtes de l’archipel Maltais. Zeitschrift für Geomorphologie 22:310– 328 Pedley HM, House MR, Waugh B (1976) The geology of Malta and Gozo. Proceed Geol Assoc 87:325–341 Pedley HM, House MR, Waugh B (1978) The geology of the Pelagian block: The Maltese Islands. In: Nairn AEM, Kanes WH, Stehli FG (eds) The ocean basins and margins, vol 4B. The Western Mediterranean. Plenum Press, London, pp 417–433 Prampolini M, Foglini F, Micallef A, Soldati M, Taviani M (2019) Malta’s submerged landscapes and landforms. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 117–128 Sammut S, Gauci R, Drago A, Gauci A, Azzopardi J (2017) Pocket beach sediment: a field investigation of the geodynamic processes of coarse-clastic beaches on the Maltese Islands (Central Mediterranean). Mar Geol 387:58–73 Sammut S, Gauci R, Inkpen R, Lewis JJ, Gibson A (2019) Selmun: a coastal limestone landscape enriched by scenic landforms, conservation status and religious significance. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 325–341 Scerri S (2019) Sedimentary evolution and resultant geological landscapes. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 31–47 Schembri JA, Spiteri SC (2019) By Gentlemen for Gentlemen—Ria coastal landforms and the fortified imprints of Valletta and its harbours. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 69–78 Soldati M, Devoto S, Prampolini M, Pasuto A (2019) The spectacular landslide-controlled landscape of the northwestern coast of Malta. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 167–178 Zammit Pace ML, Bray M, Potts J, Baily B (2019) The beaches of the Maltese Islands: a valuable but threatened resource? In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 213–227

Part II Selected Geomorphological Landscapes

6

By Gentlemen for Gentlemen—Ria Coastal Landforms and the Fortified Imprints of Valletta and Its Harbours John A. Schembri and Stephen C. Spiteri

Abstract

Ria coastal landforms are important geomorphological features because they provide a highly irregular coastline and, if sited on important channels and waterways, can be transformed from harbours, due to their features, to ports, as a result of human activities. Thus, their landscape is a reflection of two geographies: the natural indentation into the landmass and the human changes made especially to their littoral. This chapter first gives a brief account of the importance of coastal classification within geomorphology; and, secondly, a detailed definition of rias together with an account showing their importance to the Maltese Islands. The highly indented coast gives the Maltese Islands a relatively long coastline with respect to its landmass thus allowing the possibility of intense human interaction along the littoral. The second part of the chapter integrates the geographical features of the Harbours’ ria coastline with the building of the fortifications by the Order of St. John for the defence of the islands. By the end of their rule, which lasted more than two centuries, the Knights finally succeeded in defending the whole shoreline with structural changes along all the promontories of the harbours and the rectilinear parts of the coast.




Keywords

Rias Grand Harbour Maltese Islands




Creeks




Fortifications




J. A. Schembri (&) Department of Geography, University of Malta, Tal-Qroqq, Msida, MSD 2080, Malta e-mail: [email protected] S. C. Spiteri International Institute of Baroque Studies, University of Malta, Tal-Qroqq, Msida, MSD 2080, Malta e-mail: [email protected] © Springer Nature Switzerland AG 2019 R. Gauci and J. A. Schembri (eds.), Landscapes and Landforms of the Maltese Islands, World Geomorphological Landscapes, https://doi.org/10.1007/978-3-030-15456-1_6

6.1

Introduction

Coastal classifications are one of the activities that coastal geomorphologists embarked upon over a century ago to bring order to the complex nature of coasts with: Gulliver (1899) submergent and emergent coasts; Suess (1904) Atlantic and Pacific types and Johnson (1919) submergence, emergence, neutral and compound shorelines, being among the first. Especially, when not all parts of the coast have the same genetic history, Valentin’s (1952) classification was based on the complex list of coastal types and categorized into a simple classification involving emergent, submergent, erosional and depositional coasts. The addition of a time axis gives a three-dimensional view of the processes involved over unspecified timescales as Valentin took into account sea level change over the long term, which is important because ria coasts are the direct result of sea level changes. Following the acceptance of the plate tectonic theory, Inman and Nordstrom (1971) based their classification on four coastal types: coasts on diverging plate boundaries; coasts on converging plates; on major transform faults and, finally, those that developed on stable plate zones. With regard to the Maltese Islands, ria coastlines are one of the dominant geomorphological factors of local coasts particularly of the eastern and southeastern coasts of Malta where ports and harbours became the hub of the socio-economic strength of the islands. Notwithstanding the small-island scale of Malta, a range of landscapes are present along the coast (Said and Schembri 2010) with ria coastlines being dominant and with cliffs and shore platforms being additional elements.

6.2

Rias

“A city of palaces by gentlemen for gentlemen”, Benjamin Disraeli, British Prime Minister (1804–1881), is quoted to have said these words on one of his visits to Malta. 69

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However, the city and its surrounding areas would not have had its fame had it not been for its physical geographies where the sea envelopes a highly indented coastline generally identified as a ria. Rias refer to indented coastlines, that, as a result of the rising sea levels, generally through deglaciation, cause flooding of the valley floor and part of its sides. Normally, rias are funnel shaped decreasing in width and depth as they penetrate inland and their sides are a reflection of both the degree of slope of the former valley and also their height above its floor. Steep-sided rias are generally topped by a plateau and are often identified as peninsulas should two former valleys be separated by high ground. Long rias often meander inland whilst short rias are generally rectilinear. The geographical importance of rias can be assessed through Cape Finisterre where its location in Spain was for long, up to Roman times at least, considered to be the end of the known world. In addition, although its pilgrim origins date from pre-Christian times it was the final destination for pilgrims to Santiago de Compostela (Monkhouse 1990). The term ria was first derived from the area to the south of Cape Finisterre in northwestern Spain where river valleys reach the coastline at right angles (Monkhouse 1990, p. 305). A ria is a submerged coastal landform often known as a drowned valley or drowned river valley. In general, rias host estuarine river mouths. They form an irregular and indented coastline with parallel inlets separated by hills and ridges normally extending a distance inland. They form where sea levels rise relative to the land either as a result of eustatic sea level change (where the global sea levels rise) and/or isostatic sea level change (where the land sinks). When the latter occurs, valleys, which were previously above sea level, become submerged resulting in a large estuary from the river mouth to a distance inland. The short inland incision of local estuaries and the small catchment area caused minimal silting in the harbours. Rias are also formed where sea level changes create new landforms especially those associated with eustatic rises that follow the melting of ice sheets and caps (Goudie 2018). This process causes the drowning of a number of low-lying coastal areas especially river mouths, their immediate hinterlands and up-river areas. The latter includes incised valleys and their tributaries. The result is generally the formation of winding inlets and embayments that gave rise to these sheltered areas. These branch-shaped inlets are the remnants of larger valleys that were incised during intense pluvial activity that etched the valleys with steep-sided lateral cliffs, produced valley bottoms that consisted of thick sediments at their mouths and estuaries which stretched towards the limits of the flat or low-sloping hinterland. The above explains why the location of ria coasts is an important dimension in the development of harbours into ports throughout the world especially if located on important sea

J. A. Schembri and S. C. Spiteri

routes. Notable rias are located in Aveiro and Eastern Algarve in Portugal, Milford Haven in Wales, Kilindini Harbour in Kenya, the Sanriku Coast in Japan and the east coast of Australia.

6.3

The Rias of Malta

In Malta, ria landforms constitute a substantial part of the coastline (Marriner et al. 2012), providing the spatial patterns necessary for the transformation of the natural harbours into ports and their subsequent socio-economic development. As coastal inlets, they are formed by the partial submergence of river valleys that remain open to the sea and usually have a finger-like overall structure. The development of local rias may be traced to the Holocene that spans the last 20,000 years and which saw Malta being isolated from mainland Europe and especially Sicily as a result of sea level rise following the melting of the ice caps at the poles (Prampolini et al. 2019, Chap. 10). The intricate submarine relief around Malta indicates the presence of valleys that are now submerged but form a continuous pattern with the main dry land valleys. The main harbours of Malta, Grand Harbour and Marsamxett Harbour, are the result of this process. Sea level changes which affected the central Mediterranean and the Maltese Islands occurred in two major intervals. The first is known as the desiccation of the Mediterranean Basin when, as a result of tectonic movements, the Straits of Gibraltar closed leading to drying up the Mediterranean and leaving saltwater lakes to the east and west of the central Mediterranean, together with deep saline deposits on the ocean floor. The Strait was tectonically reopened with the Mediterranean Basin filling again and maintaining largely the shape and characteristics that it has today. The second series of events occurred periodically during the Quaternary and were the result of melting of the ice caps with the latest event being followed by marine transgression which commenced ca. 20,000 years ago. The melting of the ice caps at the end of the last glacial maximum increased sea levels in Malta by about 70 m (Furlani et al. 2013) and in the process drowned the system of valleys that characterised the eastern coast of Malta. In addition, further tectonic forces assisted in shaping the harbours and the surface topography of the Maltese Islands as a result of their tilting to the NE by about 4° (Galea 2019, Chap. 3). The end result of this transgression was that the islands had smaller areas of dry land and the eastern coast of Malta especially was affected and produced the’glove-finger’ and multi-finger creeks (Fig. 6.1). This left the island of Malta smaller in size but having highly indented harbours. Thus, the harbours took the overall shape that is recognized today, with a dendritic ria-type of coastline and the peninsulas between the creeks exhibiting cliffs topped with plateaux and

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By Gentlemen for Gentlemen—Ria Coastal Landforms …

71

Fig. 6.1 Maltese Islands—the results of marine transgression. Source Pedley et al. (2002)

shore platforms at their base. Table 6.1 details the various creeks on Malta and Gozo. Of particular importance are the rias that developed on Lower Coralline Limestone being short and exhibit a rectilinear pattern, whereas those developed on the softer Globigerina Limestone are dendritic and reach farther into the land mass. Guilcher and Paskoff (1975) and Paskoff and Sanlaville (1978) categorized the dendritic geographies of rias on the Maltese eastern coast into two types according to their geology and the length of their incision inland (Table 6.1). The Harbours’ ‘multi-finger’ creeks (Table 6.2) possess a longer inland incision than their ‘glove-finger’ (Table 6.3) counterparts further to the north. Of particular importance is the distinction between ‘glove-finger’ and ‘multi-finger’ creeks, where the overall shape determines terminology. Glove-finger refers to a ‘palm and thumb’ glove whilst the other refers to a ‘five-finger glove’, the fingers being separate. The distinction is helpful within the macro-landform classification for local rias. Of particular note are the channels separating Malta from Gozo and isolating Comino, which Paskoff and Sanlaville (1978) identify as ‘creeks of karstic sinking’. In addition, in areas where the softer Globigerina Limestone formation prevails, such as to the southeastern coast of Malta, the rias were identified as ‘fossil’ creeks that have since been completely eroded giving the broad expanse of Marsaxlokk Bay. Rias in the Maltese Islands are generally fault-controlled and a dry valley marks the continuation of this feature inland and

also being the partially sediment-filled portion of the incision. Table 6.1 also provides a classification of the different types of rias identified by their extent inland, degree of karstification, shape and erosion history. Following this, Tables 6.2, 6.3 and 6.4 summarise the morphological characteristics of various types of rias, and also show details of individual creeks, according to the following categories: the ‘multi-finger’ creeks (Table 6.2); the ‘glove-finger’ creeks (Table 6.3), and the vanished and fossil creeks where soft geological formations have been responsible for their morphology (Table 6.4). The numerical value shown in the last column indicates the degree of openness of the mouth to the length of the ria: the smaller the value, the wider is the mouth in relation to the length of the landform. In Malta, the complex of incisions that comprise Grand Harbour and Marsamxett Harbour (Fig. 6.2) is the result of the development of a unique ria coast having a shore platform as its rim, making practically the whole length of the shoreline accessible, and with backing cliffs that provide shelter from prevailing winds (Gauci and Inkpen 2019, Chap. 27). Inlets were formed by partial submergence of unglaciated river valleys that were drowned by marine invasion and cut transversally into the geological strike between ridge promontories. The valley mouth remains open to the sea. Their overall configuration resembles a dendritic or tree-like outline. Rias are usually underlained by alluvial deposits in buried channels (Bird 1984) that were cut when the rivers flowed down to lower sea levels in glacial phases and also exhibit various stages of sedimentary infilling with the ria upper reaches having salt marshes and dry

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Table 6.1 Classification of ria-creeks in the Maltese Islands. Type

Geologya

Landscape structural control

Terrestrial topography/marine bathymetry

Typical sites

Inland length (m)

Width at mouth, (m)

Creek-ria

LCL

Fault controlled and alluviation completely lacking at Wied iż-Żurrieq and Għasri, but partially filled at Mġarr ix-Xini and Xlendi Bay

Steep/deep marine area, short incision inland

Wied izŻurrieq Mġarr ix-Xini, Xlendi Bay, inlet at Għasri Valley

200 420

100 120

Sinking karstic creeks

UCL

Fault controlled

Cave collapse, deep karstification, western slope reduced to islets

Channel between Comino and Cominotto

360

n/a

Creeks of a complex origin

LCL

Fault controlled

Exposing of a valley

Wied ix-Xoqqa

230

100

‘Glove-finger’ creeks

LCL/Glob

Valley/subsidence valleys are long and broad/‘transversal’ with large catchment area

Low topography/shallow marine area. Bell-shaped side face, probably due to the effects of the valley system

Salina Bay St. George’s Bay St. Julian’s Bay

1600 520 400 1300

650

‘Multi-finger’ creeks

Glob (Lower)

Well developed valley/subsidence. Tilt of islands induced by the late Pleistocene and Holocene transgression (ca. 20,000 ya)

Long, low slope/shallow

Grand Harbour and Marsamxett Harbour

3500

‘Fossi’ (vanished) creeks

UCL/BC

Valley

Clay outcrops at sea level with UCL topples over and clay swept away leaving a “chaos of blocks”

Ramla Bay San Blas Bay

500 180

850 280

a UCL—Upper Coralline Limestone; Glob—Globigerina Limestone; BC—Blue Clay; LCL—Lower Coralline Limestone Source Compiled from Guilcher and Paskoff (1975), Paskoff and Sanlaville (1978)

Table 6.2 Geomorphometric data for Grand Harbour and Marsamxett Harbour ‘multi-finger’ (dendritic) creeks

Name

Inland length, metres (a)

Width at mouth, metres (b)

a/b

Grand Harbour, main channel

3500

500

19.4

Rinella Creek

280

180

1.6

Kalkara Creek

600

290

2.1

Dockyard Creek

1100

270

4.1

Senglea Creek

800

340

2.4

Menqa (Marsa)

490

400

1.2

Marsa Creek

600

180

3.3

Marsamxett Harbour, main channel Msida Creek Pieta Creek Sliema Creek Lazzaretto Creek

land further inland. Rias formed in deep marine inlets have loose unconsolidated material at the shoreline. A smaller catchment area affecting the local harbours made the latter relatively free of rapid sedimentation and thus the whole length of the accessible coast could be used.

1700

400

4.3

850

200

4.3

350

300

1.2

1450

350

4.1

800

280

3.2

The fortifications around Grand Harbour were built using the morphology and geometries provided by the cliffs with their natural height being the first attribute to be utilized (Fig. 6.3). The shore platforms at the base were identified as the zones where the connection between land and sea was

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Table 6.3 Glove-finger complexes of ria-creeks

a

Name

Geologya

Landscape structural control

Terrestrial topography/marine bathymetry

Inland length, metres (a)

Width at mouth, metres (b)

a/b

St. George’s Bay

LCL

Fault

Low sloping/shallow marine area

620

350

1.8

Il-Qaliet

LCL

Fault

Low sloping/shallow marine area

350

330

1.1

St. Julian’s Bay

LCL

Fault

Low sloping/shallow marine area

400

220

1.8

Balluta Bay

LCL

Fault

Low sloping/shallow marine area

220

150

1.5

UCL—Upper Coralline Limestone; Glob—Globigerina Limestone; LCL—Lower Coralline Limestone

Table 6.4 Vanished/Fossil rias Name

Geologya

Landscape structural control

Terrestrial topography/marine bathymetry

San Blas Bay

UCL/BC

Unstable UCL boulder fields underlain by clay stratum

Low sloping/shallow marine area

180

280

0.6

Ir-Ramla Bay

UCL/BC

Unstable UCL boulder fields underlain by clay stratum

Low sloping/shallow marine area

500

850

0.6

Unstable UCL boulder fields underlain by clay stratum

Low sloping/shallow marine area

500

375

1.3

Marsalforn Bay

Inland length, metres (a)

Width at mouth, metres (b)

a/b

Xwejni Bay

U/M/L Glob.

LCL

Low sloping

160

100

1.6

Inlet at Għar il-Qamħ

LCL

LCL

Steep/moderate to deep marine areas

300

75

4.0

Xlendi Bay

LCL

LCL

Steep/moderate to deep marine areas

375

125

3.0

Marsaxlokk Bay

U/M/L Glob

Erosion and Subsidence

Low sloping/hallow to deep marine areas

2500

1750

1.4

a UCL—Upper Coralline Limestone; BC—Blue Clay; U/M/L Glob—Upper/Middle/Lower Globigerina Limestone; LCL—Lower Coralline Limestone

efficient (Gauci and Inkpen 2019, Chap. 27). The shore platforms located all along the periphery of Grand Harbour, parts of Marsamxett Harbour and Marsaxlokk Bay gave the rias the necessary accessible edge to enable an efficient communication between land and sea. These shore platforms, normally found at the cliff base, have been turned into multifunctional areas servicing the harbours and being crucial elements in the exchange of goods and services.

6.4

Defensive Qualities of the Coastal Areas —Valletta and Its Harbours

The same geographical features which defined the landscape of the Grand Harbour and Marsamxett areas held great military advantages from a defensive point of view. None sought to exploit these geographical features for defensive purposes more effectively than the Hospitaller Knights of the Order of St. John during a period of some two-and-a-half centuries in which they ruled over the island (1530–1798). Apart from the geo-strategic importance of the location of

the Maltese Islands in the struggle for control over the region, the Grand Harbour provided the warring Hospitaller Knights with one of the finest first-class anchorages to be found anywhere around the shores of the Mediterranean, big enough to accommodate the Order’s naval fleet of galleys and warships—its prime instruments of war. The following is penned by Giovanni Rudolfo Vertmiller in 1639: “It is little wonder that the position of Malta [in the Mediterranean], and more importantly, the excellence of its harbour, had persuaded the Order of St. John to establish itself there [in Malta], as it is an ideal position capable of serving the Knights’ [military] intentions”1 (Archives of the Order of St. John 1639a). From the fifteenth to the seventeenth centuries, Malta lay directly along the frontier between the two superpowers of

1

English translation by SC Spiteri of the following original Italian text: ‘Non è meraviglia se la situazione di Malta, e quel che più importa la bonta del porto, abbino inviato, è persuaso nei tempi che la Religione si ricorero in quell Isola d’essegenze come luogo proprio alle loro intenzioni ed ivi stabilir la sua sede’.

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J. A. Schembri and S. C. Spiteri

Fig. 6.2 Ria creek geographies of the Maltese Islands, Grand Harbour and Marsamxett Harbour. Source DEM map from ERDF LIDAR data (2012)

the age—the Spanish and Ottoman empires—and, as a military and naval base, was well placed to allow the knights the opportunity to continue their war against the Turks in the eastern Mediterranean and along the shores of North Africa (Cassar and Cutajar 1984). The Knights of St. John were quick to recognize and systematically exploit these features, setting off a process of militarization which was to result in the widespread fortification of the Maltese Islands. This Hospitaller process of fortifications centred around the need to secure the harbour and its naval facilities from both landward attack and seaward bombardment. The location of the individual defensive components was determined by a series of narrow tongues of land, or peninsulas, the largest, highest and centre-most of which was then known as the Sceberras peninsula (Spiteri 2001). The latter was immediately recognized as the ideal location for the Order’s new fortified convent as it offered both command and defensibility. As the highest ground in the harbour area, it commanded all the surrounding terrain as well as the entrance to both anchorages (i.e. the Grand Harbour and

Marsamxett Harbour). The site was eventually fortified in 1566 with the creation of the formidable bastioned fortress of Valletta, named in honour of Grand Master Jean de Valette, the hero of the valiant defence against a mighty Ottoman armada sent to capture the island in 1565 (Hughes 1985). Radiating outwards from Valletta, in subsequent years, an impressive network of forts, fortified enceintes and coastal watch-posts and batteries were built, all designed by some of the leading military engineers of the day, effectively transporting the best in European military architecture directly to the shores of the Maltese Islands. By the end of their rule, the knights had enveloped the two harbours within a network of defensive lines and forts with a combined perimeter length of some 25 km of ramparts, occupying five promontories and an islet (Manoel Island) with solid fortifications built to the fortifications of the bastioned trace (Hoppen 1979). The very strength of these fortifications, however, did not rest solely upon their location and design, but also on the solid manner of their construction. For geography had furnished the island with an easily worked stone ideal (see

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75

Fig. 6.3 Valletta and its two harbours. Source Wikimedia Commons, Prelucrare 3D pentru La Valletta Harbour.jpg, Public Domain

below) for realizing extensive building programmes. Fashioned out of the local limestone by the incessant toil and skills of Maltese capo maestri (in Italian language, meaning master masons) and picconieri (also in Italian language, meaning pickmen), the Hospitaller defences were a direct product of the combination of the local landscape and the building materials that it provided. Indeed, the dry and rocky Maltese terrain was to prove an important defensive and economic asset. It provided the knights and their military engineers with practically all of the ingredients necessary for the construction of a work of fortification—stone, earth and lime—thereby ensuring that the works could be built relatively quick and cheaply without any dependence on imported materials and supplies (Spiteri 2008). Primarily, the rocky landscape enabled the walls and ditches of the fortifications, however, to be carved from the bedrock, imprinting the fortresses indelibly into the ground and endowing their ramparts with a great solidity and a tremendous power of resistance (Archives of the Order of

St. John 1639b).The process also had the added advantage of serving as an important source of building material. In other words, the ditches of the fortifications became the principal quarries supplying all the necessary stone, earth and rubble required to fashion the ramparts, where these could not be formed directly out of the bedrock as well as that required for the construction of the buildings within the perimeter (Spiteri 2008). The rock formations most suitable for providing building material for the fortifications were the Coralline and Globigerina limestones, the other sedimentary formations (i.e. Blue Clay and Greensand) being either too soft or fragile (Scerri 2019, Chap. 4). The Lower Globigerina Limestone, known locally as Tal-Franka, was the more dominant layer in the Grand Harbour area where most of the Hospitaller fortifications were located (Figs. 6.4 and 6.5). As a rule, it was the ‘pietra globigerina che viene tolta dai fossati’ (in Italian language, meaning the Globigerina Limestone extracted from the ditch) which was employed in the formation of the

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J. A. Schembri and S. C. Spiteri

Fig. 6.4 Fort St Elmo: Buttressed cliff wall and shore platform at the base. The original bastioned rampart built by the Knights of St. John in the 1680s with hardstone brought over from Corradino (in Sicily) is topped by concrete gunposts and fire control towers dating from the defence of Malta in the Second World War. Photo S. Spiteri

Fig. 6.5 Shore platform at base of Fort St Elmo. Note the rock-hewn ditch (fossato). The heavy seas have long since carried away the masonry glacis and counterscarp wall which the Knights of St. John had erected on the outer seaward side of the ditch. Photo S. Spiteri

ramparts (Archives of the Order of St. John 1639b). The TalFranka limestone, was considered “ideal for building, white in colour, easy to cut, and specially suitable for use in the erection of fortress walls as it [was] not easily crushed by artillery” (Archives of the Order of St. John 1568). On the other hand, the 1568 archives report that the Tal-Franka did not stand up very well to humidity and was rather soft.

However, the importance of Globigerina Limestone can be gauged through its spread on the island of Malta (See Table 2.3 in Schembri 2019, Chap. 2; Scerri 2019, Chap. 4). A number of uses spread over millennia (Grima and Farrugia 2019, Chap. 7). In addition, its use has provided a substantial number of employment opportunities to locals and foreigners.

6

By Gentlemen for Gentlemen—Ria Coastal Landforms …

In recognition of this, the International Union of Geological Sciences2 approved in 2019 the designation of the Maltese Globigerina Limestone as a Global Heritage Stone Resource for its role in having “achieved widespread utilization in human culture”. The broad use of Globigerina Limestone in the erection of monumental and residential buildings, artistic icons, defensive works, and other applications has depleted substantially the resource. The input of scientific research in evaluating both the properties of its surface erosion (Gauci 2018) and the geoheritage aspects of Globigerina landforms (Gauci et al. 2017; Gauci and Inkpen 2019, Chap. 27) throw further light on the importance of Globigerina Limestone in academic geomorphology research.

6.5

Conclusion

The geographical configuration of the Maltese coast gives the islands a longer coastline that is normally associated with islands of similar size and which, together with their strategic location, gives them a vital geopolitical importance for the overall security of the Mediterranean. Few places around the shores of the Mediterranean can better attest to the adage that fortifications are a direct product of geography better than the stone built defences of the Maltese Islands, erected by the Hospitaller knights of the Order of St. John in the period 1530–1798. Indeed, three things stand out from a study of the Maltese Islands and their long process of fortification: the strategic importance of the geographical position of Malta in the centre of the Mediterranean sea; the dendritic form of the harbours’ geographic configuration that provides them with an all-weather capability and the massive fortifications which were built to defend these harbours, as well as the rest of the island, from seaborne attacks and invasions. Turning harbours into ports with their urban, industrial and socio-economic activities entails a multitude of people with a range of expertise, skills and knowledge applied to fashion out a cultural unit from the geomorphological character of the environment. Partly, as a result of the importance of the Harbours to Malta, the Mediterranean and southern Europe in general, in October 2012, Valletta was declared to be a European Capital of Culture for 2018 by the European Union.

2

The proposal to the Global Heritage Stone Resource was a project under the auspices of Heritage Stone Task Group of the International Union of Geological Sciences, and its subcommittee Heritage Stones, and the International Association for Engineering Geology and the Environment, together with the Commission C-10 Building Stone and Ornamental Rock. The University of Malta was represented by the Department of Geosciences (of the Faculty of Science) and the Department of Built Heritage (of the Faculty of the Built Environment).

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References Archives of the Order of St. John in Malta (1639a) Giovanni Rudolfo Vertmiller, Italian original: ‘Non è meraviglia se la situazione di Malta, e quel che più importa la bonta del porto, abbino inviato, è persuaso nei tempi che la Religione si ricorero in quell Isola d’essegenze come luogo proprio alle loro intenzioni ed ivi stabilir la sua sede’, AOM, Malta 6554:64 Archives of the Order of St. John in Malta (1639b) ‘Lavori alla Floriana al rivellino di Auvergne: il taglio della pietra globigerina che viene tolta dai fossati e la loro misurazione in trinche fatta da parte dei perreatori; Havendo misurato questi giorni le trinche da sottoscritti perreatori tagliate ne fossi della fortificazione Floriana,’ AOM, Malta 1016 (7.07.1691) Archives of the Order of St. John in Malta (1568) Vatican Archives, URB. LAT. Ms 833, Relazione dell’Isola di Malta dal primo di Giugno fino al primo di Decembre 1568. In: de Giorgio R (1985) A city by an order. Progress Press, Malta, p 109 Bird ECF (1984) Coasts: an introduction to coastal geomorphology. Basil Blackwell, Oxford, 320p Cassar C, Cutajar D (1984) Malta’s role in Mediterranean Affairs: 1530-1699. Mid-Med Bank Report, Malta, pp 23–26 ERDF LIDAR data (2012) ERDF156 Developing National Environmental Monitoring Infrastructure and Capacity. Malta Environment and Planning Authority Furlani S, Antonioli F, Biolchi S, Gambin T, Gauci R, Presti VL, Anzidei M, Devoto S, Palombo M, Sulli A (2013) Holocene sea level change in Malta. Quatern Int 288:146–157 Galea P (2019) Central Mediterranean tectonics—a key player in the geomorphology of the Maltese Islands. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 19–30 Gauci R (2018) The identification and quantification of surface change on the limestone shore platforms of the Maltese Islands. Unpub lished Ph.D. thesis, University of Portsmouth, United Kingdom Gauci R, Schembri JA, Inkpen R (2017) Traditional use of shore platforms: a study of the artisanal management of salinas on the Maltese Islands (Central Mediterranean). SAGE Open 7(2):1–16 Gauci R, Inkpen R (2019) The physical characteristics of limestone shore platforms on the Maltese Islands and their neglected contribution to coastal land use development In: Gauci R, Schembri JA (eds), Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 343–356 Goudie A (2018) Rias: Global distribution and causes. Earth Sci Rev. 177:425–435 Grima R, Farrugia S (2019) Landscapes, landforms and monuments in Neolithic Malta. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 79–90 Guilcher A, Paskoff R (1975) Remarques sur la geomorphologie littoral de l‘archipel Maltais. Bull Assoc Geogr Franc 427:226–231 Gulliver FP (1899) Shoreline topography. Proc A Acad Arts Sci 34:151–258 Hoppen A (1979) The fortification of Malta by the knights of the order of St. John. association for Scottish literary studies, vol 9. Edinburgh, p 164 Hughes Q (1985) Malta: a guide to the fortifications. Said International Ltd, Malta, pp 12–15 Inman DL, Nordstrom CE (1971) On the tectonic and morphological classification of coasts. J Geol 79:1–21 Johnson DW (1919) Shore processes and shoreline development. Wiley, New York, 584p Marriner N, Gambin T, Djamali M, Morhange C, Spiteri M (2012) Geoarchaeology of the Burmarrad ria and early Holocene human impacts in western Malta. Palaeogeogr Palaeoclimatol Palaeoecol 339–341:52–65

78 Monkhouse F (1990) Principles of physical geography. Hodder Education, London, 580p Prampolini M, Foglini F, Micallef A, Soldati M, Taviani M (2019) Malta’s submerged landscapes and landforms. In: Gauci R, Schem bri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 117–128 Paskoff R, Sanlaville P (1978) Observations géomorphologiques sur les côtes de l’archipel maltais. Zeitschrift für Geomorphologie 22 (3):310–328 Pedley HM, Hughes-Clarke M, Galea P (2002) Limestone isles in a crystal sea: the geology of the Maltese Islands. Publishers Enterprises Group (PEG Ltd), San Ġwann, Malta, 109p Said G, Schembri J (2010) Malta. In: Bird ECF (ed) Encylopedia of the world’s coastal landforms. Springer, pp 751–759

J. A. Schembri and S. C. Spiteri Scerri S (2019) Sedimentary evolution and resultant geological landscapes. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands, Springer, Switzerland, pp 31–47 Schembri JA (2019) The geographical context of the Maltese Islands. In: Gauci R, Schembri JA (eds) Landscapes and landforms of the Maltese Islands. Springer, Switzerland, pp 9–17 Spiteri SC (2001) Fortresses of the knights. BDL Books, Malta, pp 268–280 Spiteri SC (2008) The art of fortress building in hospitaller Malta. BDL Books, Malta, pp 396–400 Suess E (1904) The face of the earth (Das Antlitz der Erde), translated by Sollas HBC under the direction of Sollas WJ. Clarendon Press, Oxford, 686p Valentin H (1952) Die Kusten der Erde. Petermanns Geografische Mitteilungen Erganzungsheft, 246. Gotha, Justus Perthes, 118p

7

Landscapes, Landforms and Monuments in Neolithic Malta Reuben Grima and Simon Farrugia

Abstract

During the Late Neolithic period, Malta witnessed an extraordinary flowering of monumental architecture, and the creation of buildings that are considered to be the earliest known stone monuments to achieve such architectural complexity and sophistication, anywhere in the world. The influence of geology and geomorphology on the culture that created these monuments is discussed, with reference to two case studies, representing the two principal types of monument known, namely megalithic buildings raised above the ground and the largely rock-cut funerary complexes. It is argued that geology and geomorphology shaped the ways the Neolithic islanders inhabited the landscape and transformed it into a culturally meaningful space, and even shaped their worldviews and lifeways. Keywords




Neolithic Megalith Landscape

7.1




Temple




Monument




Introduction

The remote location, restricted size and rugged terrain of the Maltese archipelago might make it seem an unlikely place to find a thriving Neolithic culture. Nevertheless, between the fourth and third millennium BCE, not only did a remarkable and distinctive Neolithic culture flourish on the archipelago, but it also developed an unprecedented tradition of

R. Grima (&) Department of Conservation and Built Heritage, University of Malta, Tal-Qroqq, Msida, Msida, 2080, Malta e-mail: [email protected] S. Farrugia Santa Luċija, Malta e-mail: [email protected] © Springer Nature Switzerland AG 2019 R. Gauci and J. A. Schembri (eds.), Landscapes and Landforms of the Maltese Islands, World Geomorphological Landscapes, https://doi.org/10.1007/978-3-030-15456-1_7

monumental architecture, leaving a legacy of megalithic buildings that still astound us today. The landscapes and landforms of the Maltese Islands shaped the realities and everyday lives of the Neolithic inhabitants, their demographic distribution, their social organisation, and arguably, even their perceptions and beliefs about the world (Tilley 2004). In spite of the miniscule size of the archipelago, dramatic faulting and erosion processes have created a highly fragmented and varied landscape (Pedley et al. 2002; Gauci and Scerri 2019, Chap. 5). As a result, the opportunities afforded by different parts of the landscape varied dramatically according to the availability of varying resources in different areas. Factors such as availability of freshwater, suitability for crop cultivation or pasture and connectivity with the sea may change sharply even over short distances. The range of viable strategies for the exploitation of the landscape was heavily influenced by these factors, as was the demographic distribution of the inhabitants in different communities across the archipelago, and their attitudes towards the organisation of the landscape into territories (Gauci and Schembri 2019, Chap. 1). Perhaps the most eloquent testimony to the intimate relationship between geomorphology and the lives of the Neolithic inhabitants is that of the two classes of monumental sites that they created. The first consists of megalithic structures built above ground, of which over 30 examples are known across the archipelago. Although the purpose of these buildings is still poorly understood, they are often referred to as ‘temples’ in the literature. The second class of monuments consists of funerary sites, hewn into the rock to create chambers for the burial of the dead. One thing that both classes of monuments certainly had in common was that they are both the result of an unparalleled mastery of the different types of stone available, the subtleties of variation in their properties and the opportunities that they offered for adaptation and use. Monumental sites must have played a key role in defining, articulating and mediating the cultural transformation and ordering of the landscape into social space, and in 79

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perpetuating and legitimising the relationship of different communities to the land, across successive generations (Bradley 1993). The beliefs, norms, attitudes and worldviews that were prevalent when this process of cultural appropriation of the landscape unfolded in Neolithic Malta are largely lost. Of the sparse and fragmented archaeological evidence that has come down to us, one of the strands that may give some glimpse into this lost world is the location and positioning of monumental sites in the landscape, this being the main focus of the chapter. In order to take a closer look at the ways geomorphology and topography were appropriated, exploited and given cultural significance in Neolithic Malta, the chapter will focus on two case study sites, one of them very well-known, the other rather less so. Of the megalithic monuments that are preserved on Malta, the most extensive and most visited are the four complexes of Ġgantija (on Gozo) and Ħaġar Qim, Mnajdra and Tarxien (on Malta). The first case study considers the landscape setting of two of these, namely Ħaġar Qim and Mnajdra, along the Magħlaq Fault on the south-western coast of Malta. The second, rather less well-known, case study is Xemxija, where a cluster of rock-cut tombs occupies a hilltop on one of the parallel ridges in northwest Malta, while a megalithic temple stands a short-distance downhill. Each of these case studies sheds light on the attitudes of the Neolithic islanders to the landscapes and landforms that surrounded them.

7.2

Malta (Fig. 7.1). They stand about two kilometres from Qrendi, the nearest modern-day village, and about 200 m from the nearest shoreline to the southwest of Mnajdra. Ħaġar Qim lies about 130 m above mean sea level, overlooking both Mnajdra and the surrounding stretch of coastline. Mnajdra is located on a south-facing slope, while Ħaġar Qim stands on the crest of a hill. The stretch of coastline where these two monuments are located is one of the few points on Malta’s south-western coast which allow access to the sea. For about ten km to the north and the same distance to the south, the coast consists mostly of sheer cliffs. In the immediate vicinity of this cluster of megalithic monuments, however, the Magħlaq Fault has created a down-thrown coastal shelf that slopes more gradually to the present-day sea level (Gauci and Scerri 2019, Chap. 5).

7.2.2 Xemxija Tombs Xemxija Bay forms the innermost end of Saint Paul’s Bay, which is effectively the submerged part of the Pwales valley or graben (Fig. 7.2). Immediately north of this valley rises the Bajda Ridge, stretching across the width of Malta. The eastern end of this ridge rises to form a relatively circular hillock. This hillock is today the highest part of the Xemxija Heritage Trail, which includes several cave dwellings, an apiary, several Neolithic and Punic tombs, and a Neolithic building (Panzera et al. 2012). The Neolithic tombs and megalithic building will be discussed in this chapter.

Geographical Setting of the Case Study Sites 7.3

The three principal geomorphological regions of the island of Malta are as follows: the Rabat-Dingli plateau to the west; the parallel ridges and valleys, also known as horsts and grabens, which characterise the northwest end of the island; and the gently rolling central plain that stretches across southeast Malta (Bruce 1965; Gauci and Scerri 2019, Chap. 5). Hardly any Neolithic monuments are known from the Rabat-Dingli uplands. The two case studies discussed below are located in the other two geographical regions. The first is located on the south-western coast along the southern boundary of the central plain. The second is located on the Bajda Ridge, which is one of the parallel ridges and valleys in northwest Malta.

7.2.1 Ħaġar Qim and Mnajdra The two groups of megalithic buildings known, respectively, as Ħaġar Qim and Mnajdra lie on the south-western coast of

Distribution of Neolithic Monuments

The geographical regions of Malta present a range of contrasting environments, each of which present very different possibilities for human exploitation. While these environments are understood to have evolved considerably since the Neolithic, some fundamental characteristics are unlikely to have changed significantly. Foremost among these is the highly fragmented nature of the landscape, presenting very different environments within short distances of each other. These contrasting environments must have heavily conditioned the range of possible forms of exploitation across the landscape, which in turn conditioned the distribution of the population, and the appropriation and ordering of the landscape into social space. In northwest Malta, for example, the parallel ridges and valleys presented a series of sheltered valleys surrounded by freshwater springs, which were probably ideal for crop cultivation, alternating with windswept and craggy ridges where the soil cover was vulnerable to rapid erosion (See also Soldati et al. 2019, Chap. 14; Rolé

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Fig. 7.1 Orthophoto of the landscape around Ħaġar Qim and Mnajdra. The position of the two monuments is clearly marked by the protective shelters. The Magħlaq Fault runs diagonally along the shoreline. Source MEPA

2019, Chap. 24). Such natural divisions in the landscape lent themselves to the creation of socially significant boundaries and territories. Monuments often play a key role in the appropriation and ordering of a landscape, and the Maltese Neolithic was no exception. The two main classes of monumental site, namely megalithic buildings and rock-cut funerary sites, appear to have done this in different ways. The distribution of megalithic buildings across the archipelago shows a number of recurring patterns in the relationship of individual sites with their landscape setting. A GIS-based study has statistically demonstrated that there was a preference to locate megalithic buildings near to freshwater springs and to more level areas that were suitable for crop cultivation, and near to places that permitted access to the sea (Grima 2007). The rather smaller sample of funerary sites available is less suitable for reliable statistical analysis of the characteristics of the locations where they are found. However, inspection of funerary sites suggests that their position too followed a number of norms. In contrast to megalithic buildings, which are often located on the slopes of hillsides, funerary sites are usually located

on the crest of a ridge or the summit of a hilltop, which often dominated views of the surrounding landscape.

7.4

Geological and Geomorphic Setting of Different Classes of Neolithic Monuments

7.4.1 The Geological and Geomorphic Setting of Megalithic Monuments: The Case of Ħaġar Qim and Mnajdra The scatter of megalithic monuments that are known across the archipelago each have their own idiosyncrasies and variations in form, scale and positioning in the landscape. As observed in the previous section, some useful generalisations may be made about their relationship to other features in the landscape. In order further to explore such patterns, this section focusses on one specific cluster of megalithic monuments, composed of Ħaġar Qim and Mnajdra, which are perched along the Magħlaq Fault, on the southwest coast of

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Fig. 7.2 Orthophoto of the landscape around the Xemxija Tombs. The larger white square shows the position of the hillock which the tombs are dug into. The smaller square to its left marks the position of the megalithic building. Source MEPA

Malta. This group of buildings was chosen for two main reasons. First, it represents one of the most remarkable, extensive and well-preserved concentrations of megalithic architecture in the archipelago. Second, the remoteness of the area has meant that it has sustained fewer modifications under the pressures of modern development, permitting the relationship between monument and landscape to remain legible to the modern observer. The group of megalithic buildings at Ħaġar Qim stands on the spine of a ridge that dominates much of the surrounding landscape. It is comprised of three distinct structures, usually referred to as the ‘Main Temple’, the ‘North Temple’ and the ‘East Remains’. Like most of the megalithic temples of Malta, the buildings at Ħaġar Qim were not built as a single project, but evolved over a succession of building episodes. Considered collectively, the creation of the structures at Ħaġar Qim spans the millennium or so when Malta was characterised by megalithic building activity, roughly from 3600 to 2400 BCE. About 500-m downhill and to the west lies Mnajdra, another, equally astounding group of megalithic buildings

which are nestled into the hillside. This group also appears to have developed over a long period of time, and must have been in use throughout the period when megalithic construction flourished in Malta. The group consists of four distinct buildings, namely the South, Central and East Temples, and a less discernible ruin a short distance further east. Although only 500 m apart, the sites of Ħaġar Qim and Mnajdra present different geological characteristics. This is explained by the fact that since Malta forms part of the Pantelleria rift system, its geology is characterised by a series of fault swarms (Pedley et al. 2002). This faulting brings different stratigraphic layers of rock, which were deposited sequentially, to the same surface level. A case in point is the Magħlaq Fault, to the west of Ħaġar Qim, where Lower Coralline Limestone (LCL) crops out at a higher level than the Upper Coralline Limestone (UCL). Ħaġar Qim is built on a Lower Globigerina Limestone (LGL) outcrop, while the terrain around Mnajdra is mainly composed of LCL. In several temple sites around Malta, both the harder Coralline Limestone and the softer LGL are available nearby, and both materials are used (Grima 2004). For example, although

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Fig. 7.3 Mnajdra. Interior view of the South Temple

Mnajdra is closer to the Coralline Limestone outcrops, only its outer walls are built using this material, making them more resistant to erosion, while the more smoothly finished inner walls are made of LGL probably originating from near Ħaġar Qim (Fig. 7.3). The latter is entirely built of Lower Globigerina Limestone, which permitted the smooth finish and elaborate carvings that characterise the interior of the ‘Main Temple’. The softer structure of Globigerina Limestone makes it more easily workable than Coralline, but also makes it more prone to weathering and erosion. Both materials have been widely used in Malta as building materials since the Neolithic period (Cassar 2010).

7.4.2 The Geological and Geomorphic Setting of Funerary Monuments: The Case of the Xemxija Tombs Apart from the megalithic monuments built above ground, such as the ones that have just been considered, Malta’s Neolithic landscape was characterised by another type of monument, the funerary sites carved into rock. As already noted, fewer examples of this type are known. Funerary sites display an even wider range of variation in scale and form than do the megalithic buildings. Neolithic sites in Malta may range from single tombs, intended to hold a few individuals, to the astounding complexity of the Ħal Saflieni Hypogeum, which is designated as a UNESCO World Heritage Site. This variation makes it more difficult to make

useful generalisations about the geological and topographic settings of funerary sites. Close examination of the relationship between individual sites and their local landscape, however, may shed some light on the matter. The present discussion will focus on the specific case of the Xemxija Tombs, which has been chosen primarily because the landscape context around it is still readily discernible. In terms of complexity, the site stands roughly midway along the spectrum between the individual tomb on the one hand and the complexity of the Ħal Saflieni Hypogeum, or the Xagħra Circle on Gozo, on the other. The Neolithic funerary site of Xemxija consists of a series of individual tombs carved into the rock near the summit of a hilltop that rises at the northeast end of Bajda Ridge. Each has its own entrance, through a shaft which leads in turn to the burial chamber. Six tombs were excavated by Professor John Evans in 1955, yielding pottery datable to the Ġgantija Phase (c. 3600—c. 3000 BCE) (Evans 1971). Eight features classed as ‘Late Neolithic Tombs’ were plotted in this location and scheduled for protection by the Planning Authority in October 1998 through Government Notice 763/98 (Malta Government Gazette 1998). The Xemxija tombs stand on a hillock which rises to a height of almost 70 m above mean sea level (Fig. 7.4). The hillock forms part of one of the ridges or horsts that form part of the horst and graben topography which characterises northwest Malta. Xemxija is surrounded by WSW–ENE trending normal faults and is characterised by three lithotypes: (1) clay from

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Fig. 7.4 Xemxija Bay viewed from the south. The Xemxija hillock is visible on the skyline in the centre of the picture

the Blue Clay (BC) formation; (2) the hard and pitted Tal-Pitkal Member, forming part of the UCL; and (3), the softer and more erodible Mtarfa Member, also forming part of the UCL (Scerri 2019, Chap. 4). As with most of the rest of the northern coast of Malta, the edges of the Bajda Ridge are characterised by lateral spreading and rock-fall phenomena which occur when the harder, more brittle UCL is undercut by the erosion and slumping of the softer, unconsolidated BC formation (Panzera et al. 2012).

7.5

Landforms and Prehistoric Landscapes

Each of the two sites described above allows us some insight into the priorities, worldviews and attitudes to the landscape that prevailed in Neolithic Malta. The two megalithic complexes of Ħaġar Qim and Mnajdra are located at a very specific point of Malta’s southwest coastline. The southwest coast is characterised by steep, sometimes precipitous cliffs, which characterise the 20 km of coastline between Marsaxlokk Bay and Ġnejna Bay (Gauci and Scerri 2019, Chap. 5). One of the very few points along this stretch where the coastline is accessible is the downthrown coastal shelf along the Magħlaq Fault, stretching for around two km between Wied iż-Żurrieq and Għar Lapsi. The megalithic complexes of Ħaġar Qim and Mnajdra are located on this part of the coast, overlooking the coastal shelf. It is clearly not coincidental that the next megalithic monuments that are known along this coast occur near Ġnejna Bay to the north and in Marsaxlokk Bay to the south. Access to the sea and maritime connectivity appears

to have been important considerations in the choice of location of these megalithic complexes. Another factor which seems to have influenced the location of megalithic buildings appears to be the availability of cultivable soil. A short distance north of the two megalithic buildings, a gently rolling plain begins, stretching across southeast Malta. The preference for areas more likely to permit crop cultivation is also suggested by the position of megalithic monuments elsewhere in the archipelago. These are generally located near to the edges of more level areas where soil is less prone to erosion (Grima 2004, 2007). A further factor that appears to have influenced the location of megalithic sites is the availability of a perennial source of freshwater. A freshwater spring is reported near the shore below Mnajdra. To the north of Mnajdra, a cluster of rock-cut cisterns known as the Misqa Tanks collect surface run-off from rainwater (Fig. 7.5). Their date is difficult to determine; however, their form suggests that their origin may date from the Neolithic. The location of the cisterns appears to have been very carefully selected, as they are cut into a small outcrop of the lowermost layers of LGL, which lies immediately over the LCL. These lowermost layers of LGL tend to have a higher clay content than the rest of the formation and are relatively impervious to water (Dr. Saviour Scerri, personal communication, 11 January 2012). This was confirmed by a farmer whose family has worked the land in the immediate vicinity for several generations, who explained to one of the authors (RG) that the cisterns did not need any lining because they were naturally impervious. The concern with a perennial water supply is also evident on other megalithic sites, which show a strong

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Fig. 7.5 Misqa Tanks, north of Mnajdra. One of the tanks in winter

preference for locations near to freshwater springs (Grima 2004, 2007). One more observation that may be made is the preference for south-facing slopes. The known sample of megalithic sites across the archipelago shows a distinct preference for sites with a southern or south-western aspect, suggesting a preference for the longer hours of sunlight and the relative shelter from the northern winds that they afforded.

Fig. 7.6 View of the Xemxija hillock from the southwest, as seen from the megalithic building

The position of Ħaġar Qim and Mnajdra, as in the case of most of the other known megalithic buildings on the archipelago, suggests a strong preference for sites that had access to all the resources that an agricultural community needed to thrive. Several of these sites have yielded evidence that the megalithic monuments were raised in places that were already inhabited for centuries, sometimes a millennium or more, before the advent of megalithic construction (Grima

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2004). All the evidence therefore suggests that megalithic buildings were located very much at the centre of daily life of the community, and that it is not unreasonable to think of these monuments as useful proxy indicators of the distribution of the population. To continue to fill in this rapid and tentative sketch of the way the landscape was perceived and appropriated by the Neolithic inhabitants, we now turn to the evidence of the funerary sites, which present some interesting contrasts to the megalithic monuments built above ground. The spatial ordering of a funerary site may allow insight into a society’s attitudes to the dead. In a major study of another Neolithic funerary site, namely the Xagħra Circle on Gozo, it has been argued that, in the belief-system of the Neolithic inhabitants,

the realm of the living was distinct from an underworld or realm of the dead (Malone and Stoddart 2009, particularly p. 376, Fig. 14.14). Another study, this time of the Hypogeum at Ħal Saflieni, has argued that geological structure was also exploited to articulate the separation between the realm of the living and the nether realm of the dead (Grima 2016). The choice of site for the Xemxija Tombs was arguably influenced by its geomorphological distinctness. The dome-like regularity of the conical hillock that rises from the summit of the Bajda Ridge is quite uncommon in the Maltese landscape. Viewed in plan, the contours of this feature are a series of perfectly regular concentric circles. As a result, whatever the direction from which it is approached,

Fig. 7.7 Orthophoto of Xemxija hill, showing the tombs clustered on its NE flank. Source Planning Authority. Contour data ASL derived from 1968 1:2500 survey sheet. Tomb planimetry based on laser scan

by John Meneely, School of Natural & Built Environment, Queen’s University Belfast

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this feature presents the same low, conical appearance (Figs. 7.6 and 7.7). The regularity of this feature appears to have attracted the attention of the Neolithic inhabitants, who chose it as the site of one of their more elaborate funerary sites. Yet in spite of its regularity, the tombs are located neither at the centre, nor the summit of the feature. Instead they are located on its slopes, below its highest contours. Furthermore, the tombs are not uniformly distributed across the different aspects of the hillock, but are practically all concentrated in the northeast quadrant of its slopes. This apparently idiosyncratic pattern, in a site which is so regular and symmetrical in its natural characteristics, offers the tantalising possibility of a glimpse into some cultural preferences or biases at work. Looking at the wider landscape around the hillock, the remains of a megalithic temple stand about 200 m to the southwest, at a lower point of the crest of the ridge. Recalling the earlier discussion about the relationship between megalithic buildings and land that is more favourable for crop cultivation, here it may be noted that this windswept ridge is anything but favourable. The valley bottoms of the two grabens that flank it are, however, sheltered and well-watered (Fig. 7.2). The larger of the two valleys is Pwales Valley to the south. The floor of this valley is about half a kilometre wide, and stretches about 3 km to the west coast. To the northwest, the graben between Bajda and Mellieħa Ridges shelters the smaller but equally fertile Miżieb Valley, which has an area about a third of that of the Pwales Valley (Gauci and Scerri 2019, Chap. 5). The position of the megalithic building, and of any associated settlement, astride the ridge between these two valleys may have been chosen as the optimal position from which to exploit and manage the resources of both valleys, while also being within easy reach of embarkation points in Xemxija Bay and Mistra Bay. This brings us back to the question of how the Xemxija Tombs were positioned in relation to the productive and ritual landscape. Approaching or observing the hillock where the Xemxija Tombs are located from the direction of the megalithic building, the tombs appear to be located on the further side of the hillock. This monumental building was evidently an important focus of communal activity. Furthermore, the evidence from comparable sites, particularly Skorba, suggests that such monumental buildings were located in the immediate vicinity of settlements. The corollary here is that at Xemxija, the tombs appear to be placed on the further side of the hillock from any such settlement. Arguably, the tombs are also positioned on the far side from the land in the valley bottoms that, it is suggested here, was most highly prized. The hypothesis that the asymmetrical positioning of the tombs in relation to the conical hillock that they are carved into is both intentional and meaningful, is reinforced by the

87

orientation of the tombs themselves. The tombs consist of a vertical shaft, with a lateral opening that leads into the burial chamber. The tombs known at Xemxija demonstrate a distinct preference for the aperture into the tomb chamber to be oriented in a generally north-easterly direction: that is facing away from the centre of the conical hillock (Figs. 7.7 and 7.8). While the evidence is admittedly tenuous, it goes some way in explaining the ways in which topography and landform may have been imbued with cultural significance in Late Neolithic Malta. There is, for instance, a preference to place funerary sites on or near distinctive and conspicuous features in the landscape. The site of the Xemxija Tombs is conspicuous, because it dominates much of the surrounding landscape. Before modern building had taken place on the northeast end of Bajda Ridge, it would also have been visible from a large part of Xemxija Bay. It was also distinctive in form and, therefore, immediately recognisable even from a distance. The dead were therefore laid to rest in places that could be seen and recognised from afar: natural landmarks that dominated the landscape, and in this case, even the

Fig. 7.8 The entrances to Xemxija Tomb 1 and Tomb 2, in relation to the summit of the hillock behind them

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seascape. On the other hand, the evidence also seems to suggest that the tombs were placed away from the parts of the landscape most frequently used in daily life, which are also known as the ‘taskscapes’ of everyday life (Ingold 1993). The positioning of the tombs on the side of the hillock away from where most daily activities would have taken place suggests that they were considered to belong to a nether realm, which also needed to be kept distant and apart from the routines of daily life. The intervisibility of the tombs with the bay also suggests an association between death, the sea and maritime travel. This suggests a paradoxical relationship with the realm of the dead. On the one hand, the ancestors are considered to be a potent force, and perhaps one which legitimised a community’s claims to the land. Depositing ancestors in a dominant and conspicuous location that announced their presence may have been a way of culturally appropriating and assimilating landforms and even territories. On the other hand, the distancing of the dead from the pathways of daily life suggests a healthy respect, perhaps even fear, of the power of the ancestors, who were

R. Grima and S. Farrugia

only to be visited in pre-ordained ways, rather than merely stumbled upon in the course of daily tasks. We may reconsider some of the other known funerary sites in the light of the above observations. The preference for conspicuous and distinctive landforms is certainly borne out by a number of other examples. The funerary complex known as the Xagħra Circle on Gozo is located on a similar eminence, which is the highest point in the vicinity. The Ħal Saflieni Hypogeum is located at the break between the hillside that slopes down to the inner end of the Grand Harbour, and the gently rolling plain that extends across southeast Malta. The Żebbuġ tombs were cut into a Globigerina Limestone outcrop that rose above the surrounding landscape. The tomb at San Pawl Milqi was likewise cut into Globigerina Limestone at the foot of the Wardija hills, conspicuous because its pale yellow colour contrasts with the surrounding landscape. Yet another feature that may be a Neolithic tomb is cut into a precipitous rocky outcrop between two deep gorges which converge to form the Xlendi valley on Gozo (Fig. 7.9).

Fig. 7.9 Xlendi Valley (Gozo). A rock-cut feature, believed to be a Neolithic tomb, is positioned on a spur of rock between two gorges that converge to form Xlendi Valley. The white square marks the position of the feature

7

Landscapes, Landforms and Monuments …

The relationship between these sites and the taskscapes of everyday life is somewhat more difficult to determine. In the case of Saflieni, San Pawl Milqi, and Xlendi, but not at Xagħra or Żebbuġ, a possible association with the sea may also be noted. The tomb at San Pawl Milqi is suggestively placed across what would have been the inner reaches of a bay from the megalithic building at Tal-Qadi. The tomb noted in Xlendi Valley, though conspicuous from across the valley, is on an isolated ridge and is extremely difficult to reach, once again suggesting a preference for visually prominent but physically remote locations. Debate over these questions is likely to continue given that the evidence is so fragmentary. However, there are enough clues to begin to suggest a way of looking at the world, of inscribing meaning into the landscape and its landforms, which is far removed from our own.

7.6

Conclusion

This chapter has considered two examples of how the local landscape was appropriated during the Neolithic period. Reinterpretations and new appropriations of these same landscapes have continued to take place since, often putting new pressures on their conservation. Ħaġar Qim and Mnajdra have since 1992 been included in the UNESCO World Heritage List. They are among the most visited cultural heritage sites on Malta, and their immediate surroundings are designated an Archaeological Park. The principal conservation threat to these monuments is their progressive erosion due to their exposure to the elements. In 2009, protective shelters were installed over the two sites, designed to slow down the rate of erosion (Cassar et al. 2011; Farrugia and Schembri 2013). At Xemxija, indiscriminate building poses the most acute threat to the Xemxija tombs. The encroachment to date of modern buildings on the Bajda Ridge pales into insignificance when compared to a new high-rise development on the summit of the ridge that was granted planning permission in 2014. This development is symptomatic of the ever-mounting pressures being placed on the landscape by intensified building activity, posing fresh challenges to the conservation of Malta’s cultural landscapes. An improved understanding of past attitudes to the geology, landscapes and landforms of the archipelago may help raise awareness of their importance and value and should help inform their sustainable stewardship. Acknowledgements The authors are indebted to the editors and anonymous reviewers for their most helpful advice and suggestions. The orthophotos in Figs. 7.1, 7.2 and 7.7 were kindly made available by the Malta Environment and Planning Authority (ERDF156: Developing National Environmental Monitoring Infrastructure and

89 Capacity) through an agreement signed with the University of Malta in 2013.

References Bradley R (1993) Altering the Earth: the origins of monuments in Britain and continental Europe. Society of Antiquaries of Scotland, Edinburgh, 150p Bruce MW (1965) Malta: a geographical monograph. Progress Press, Malta, 75p Calleja, Tonelli (2019) Dwejra and Maqluba: emblematic sinkholes in the Maltese Islands. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 129– 139 Cassar J (2010) The use of limestone in a historic context—the experience of Malta. In: Smith BJ, Gomez-Heras M, Viles HA, Cassar J (eds) Limestones in the built environment: present-day challenges for the preservation of the past. Geological Society, London, Special Publications 331(1):13–25 Cassar J, Galea M, Grima R, Stroud K, Torpiano A (2011) Shelters over the megalithic temples of Malta: debate, design and implementation. Environ Earth Sci 63:1849–1860 Evans JD (1971) The prehistoric antiquities of the Maltese Islands: a survey. Athlone, London, 260p Farrugia S, Schembri JA (2013) Wind funnelling underneath the Ħaġar Qim protective shelter. Malta Archaeol Rev 9:51–59 Gauci R, Scerri S (2019) A synthesis of different geomorphological landscapes on the Maltese Islands. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 49–65 Gauci R, Schembri JA (2019) Introduction to landscapes and landforms of the Maltese Islands. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 1–5 Grima R (2004) The landscape context of megalithic architecture. In: Cilia D (ed) Malta before history: the world’s oldest freestanding stone architecture. Miranda Publishers, Malta, pp 326–345 Grima R (2007) Landscape and ritual in Late Neolithic Malta. In: Barrowclough D, Malone C (eds) Cult in context: reconsidering ritual in archaeology. Oxbow Books, Oxford, pp 35–41 Grima R (2016) Journeys through the underworld in Late Neolithic Malta. In: Nash G, Townsend A (eds) Decoding Neolithic Atlantic and Mediterranean island ritual. Oxbow Books, Oxford, pp 202– 213 Ingold T (1993) The temporality of the landscape. World Archaeol 25 (2):152–174 Malone C, Stoddart S (2009) Conclusions. In: Malone C, Stoddart S, Bonanno A, Trump D, Gouder T, Pace A (eds) Mortuary customs in prehistoric Malta: excavations at the Brochtorff Circle at Xagħra (1987–1994). McDonald Institute, Cambridge, pp 361–384 Malta Government Gazette (1998) Government Notice 763/98: scheduling of property. In: Malta Government Gazette 16 October 1998: pp 7858–7860 Panzera F, D’Amico S, Lotteri A, Galea P, Lombardo G (2012) Seismic site response of unstable steep slope using noise measurements: the case study of Xemxija Bay area, Malta. Nat Hazards Earth Syst Sci 12:3421–3431 Pedley HM, Hughes-Clarke M, Galea P (2002) Limestone isles in a crystal sea: the geology of the Maltese Islands. Publishers Enterprises Group (PEG Ltd.), San Ġwann, Malta, 109p Rolé A (2019) Landforms and processes at Il-Majjistral park and its environs. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 305–316

90 Scerri S (2019) Sedimentary evolution and resultant geological landscapes. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 31–47 Soldati M, Devoto S, Prampolini M, Pasuto A (2019) The spectacular landslide-controlled landscape of the northwestern coast of Malta.

R. Grima and S. Farrugia In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 167–178 Tilley C (2004) The materiality of stone: explorations in landscape phenomenology. Berg, Oxford, 244p

8

Cave Dwellers at Għar il-Kbir: Malta’s Best Documented Troglodytic Community Keith Buhagiar

Abstract

During the medieval and Early Modern periods, countryside areas in northwest and northern Malta commonly provided shelter to troglodytic (cave-dwelling) communities. The adoption of a troglodytic lifestyle was made possible due to the prevailing geographies that provided shelter in the cavernous landscape within the Upper Coralline Limestone stratum, as well as the presence of adequate hydrological resources. Jean Quintin d’Autun is the first known author to have described this lifestyle in his Insulae Melitae Descriptio of 1536. Widespread disinterest in troglodytic habitations prevailed until recently, and it was only during the past three decades that a determined effort was made to document, interpret and contextualise the significance of Malta’s troglodytic past. Għar il-Kbir remains Malta’s best known troglodytic settlement, but knowledge on its inhabitants is scant. It is only through the Early Modern period writings of Athanasius Kircher, Gian Francesco Abela and Carlo Castone Della Torre Di Rezzonico that aspects relating to the customs, beliefs and traditions of the Għar il-Kbir dwellers became better known. Keywords

Troglodytism development management

8.1









Cave dwellers Rural landscape Hydrology Water

Introduction

The adaptation of caves into houses and cultic shrines represents an ancient Mediterranean practice. The profuse diffusion of troglodytic settlements in Granada (Spain), Matera K. Buhagiar (&) Department of Classics and Archaeology, University of Malta, Tal-Qroqq, Msida, MSD 2080, Malta e-mail: [email protected] © Springer Nature Switzerland AG 2019 R. Gauci and J. A. Schembri (eds.), Landscapes and Landforms of the Maltese Islands, World Geomorphological Landscapes, https://doi.org/10.1007/978-3-030-15456-1_8

in Basilicata (Italy), Pantalica, Cava d’Ispica, Scicli and other areas in south-east Sicily, and Matmata in Tunisia show that “Mediterranean people have always chosen caves and grottoes, natural and excavated, as providing convenient, cool and often defensible dwellings, stores, stalls, cisterns, churches, burial places and catacombs” (Luttrell 1979, p 461). The troglodytic phenomenon was widespread in the Mediterranean region throughout the middle ages whenever environmental conditions proved favourable. Arid and semi-arid areas which suffered from a lack of timber, but which on the other hand provided plentiful natural rock shelters and an abundance of easily quarried stone, were instrumental in conditioning a type of architecture which was entirely stone oriented besides encouraging cave dwelling. Malta was no exception (Vella 1980), and the local archaeological record gives testimony to the widespread use of caves for dwelling, burial and cultic purposes since prehistoric times. For a chronological list of pre-medieval period Maltese troglodytic sites see Buhagiar (2012). This chapter concentrates exclusively on the High and Late Medieval period cave-dwelling sites of Malta, placing particular emphasis on the Għar il-Kbir settlement, located in the proximity of the rural village of Dingli. As the timeframe covered by the ‘Early’, ‘High’ and ‘Late Medieval’ terminology employed in this chapter lacks standardisation, an explanation of these, within the context of the Maltese medieval historical framework, is necessary. ‘Early Medieval’ encompasses the mid-sixth to the tenth centuries AD and includes the Byzantine and the early Muslim periods. ‘High Medieval’ comprises the late tenth until the early thirteenth centuries AD and, in a local chronological framework, involved the late Muslim and Norman periods. ‘Late Medieval’ encompasses the late thirteenth century until the arrival of the Hospitaller Knights of the Order of St John in Malta in 1530. ‘Early Modern’ refers to the post-1530 period and ends in 1798 with the capitulation of Malta by the Hospitaller Knights to the French forces. 91

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K. Buhagiar

The Roots of High and Late Medieval Troglodytism

The roots of Maltese Late Medieval troglodytism probably lie in the twelfth and thirteenth centuries and are the result of new attitudes adopted following the Norman reconquest of 1127 (Buhagiar 2005). It has been observed by Wettinger that the north and north-west sector of Malta is ‘strangely bare’ of settlement sites known as ‘raħal’ (Maltese word meaning village), either due to a defect in the surviving documentation, or because the Maltese countryside had been depopulated for so long that the surviving place-names dropped their ‘raħal’ prefix (Wettinger 1975; Fiorini 1993). On the other hand, personal non-invasive field research carried out in north and north-west Malta during the past two decades was in many ways an eye-opener and shows that it was the ‘Għar’-type settlements which prevailed in these areas. ‘Għar’ in Maltese language means cave. Sicilian cave sites were often distinguished by the ‘għar’ prefix, and Maltese place-name evidence similarly shows this to be the case with a limited number of cave settlements (Wettinger 2000), Għar il-Kbir being a typical case in point (Fig. 8.1). Furthermore, it is frequent for Maltese caves to derive their names from Muslim personal nomenclature. A translation of ‘Għar Dalam’, for example, is not ‘Cave of Darkness’—‘Dalam’ being a surname which survived right into the fifteenth century (Fiorini 1988). The emergence of a strong troglodytic tradition during the High Medieval period probably reflects coordinated attempts at increasing the agricultural output of specifically designated countryside areas of Malta and Gozo. There is no direct archaeological evidence for any major settlement outside Mdina and its suburb of Rabat throughout most of the Norman and early post-Norman period, but it is probable that several rock-cut settlements in the north and north-west areas of Malta associated with viridaria or giardini-type cultivations might have already made their appearance during this period. Giardini are best defined as specifically designated agricultural areas inside which intensive cultivation took place. There is a widespread reference to giardini (sing. giardino, in Italian language) cultivations in Late Medieval and Early Modern literary sources, but the lack of an English equivalent term poses a problem of translation. Possible but inexact modern equivalents include orchards, plantations, gardens, market gardens and even small holdings. The study of Maltese rural landscape development during the High and Late Medieval periods has established how generally the life source of giardini was a series of man-excavated subterranean galleries which tapped perched aquifers in order to yield a perennial water supply (Buhagiar 2014). Both perched aquifer galleries and the giardino

framework in which these are contained, have been recently subjected to a retrogressive analytical investigation (Buhagiar 2014), which involves the removal of known dated features within a landscape in order to gain better knowledge of its components at an earlier period (Rippon 2012; Vermeulen 2004; Oosthuizen 2006; Cousins 2010). Such an exercise does not come without its limitations, but it has permitted the association of a number of perched aquifer galleries with the Late Medieval period (Buhagiar 2014). Perched aquifer gallery-water-capture technology was probably introduced locally from neighbouring Sicily around the twelfth century AD (Buhagiar 2014). In view of this fact, it is likely therefore that a number of fertile valleys in the north-west sector of Malta, such as Wied ir-Rum, Wied Ħażrun, Mtaħleb, Ġnien is-Sultan and Wied Liemu, which contain extensive field terraces, water galleries and rock-cut settlements, all formed part of a post-1127 process of intensification (Figs. 8.1 and 8.2). Field terracing construction coupled with the hydrological intensification of an area entails a labour intensive input, and it may take decades to completely transform a previously uncultivated landscape into an agriculturally productive one. The Gumerin (Gomerino) and Deir Ilbniet (Dejr il-Bniet) estates, both in the territory of Rabat (Malta), were already listed as giardini in 1317 and 1351, respectively (Bresc 1975). Due to the availability of perennial water springs, giardini still are capable of producing a summer crop in an otherwise arid season, thus increasing the economic value of such land (Fig. 8.3).

8.3

Cave-Dwelling Typologies and Their Geological and Geographical Setting

The majority of the Maltese troglodytic settlement sites were abandoned in the opening decades of the twentieth century and still survive to a fair degree of preservation. Nonetheless, the study of Malta’s cave settlements does not come without its difficulties. Past cave re-occupation and enlargement often involved the destruction of previous occupational phases, and in the absence of stratified deposits, dating is difficult. Caves frequently cluster together into units, but isolated caves containing evidence of human or animal habitation are fairly frequent. Dry- and wet-stone walls commonly screen a large section of the caves’ entrance, leaving an arched or square-headed doorway as the only means of access. Dry-stone constructions frequently partition cave interiors into a series of individual spaces. The exterior screening wall and sections of the caves’ interior were occasionally plastered and whitewashed, but the widespread nature of this practice is not known. Deeds dating to the fourteenth and fifteenth centuries that describe

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Fig. 8.1 Map of the Maltese archipelago showing the spatial distribution of place-names mentioned in the text

the furniture content of Maltese Late Medieval aboveground houses lead us to believe that habitable caves also contained few items of furniture, perhaps a table, door and a couple of other wooden furnishings. Maltese cave settlements were sometimes spread out on two different levels, making the best possible use of the limited space available. There are two distinct types of medieval cave-settlement sites in Malta. The first shows an adaptation of natural

depressions or solution subsidence structures, whereas the second includes cliff-face settlements. Cave usage varies from cultic worship to human habitation, animal pens or storage spaces often connected to agricultural usage, animal-driven mills (in Italian language, centimoli) and apiaries (Buhagiar 2012). Għar il-Kbir is a typical example of a karst feature settlement. Karst topography is locally restricted to regions containing Upper Coralline deposits and

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K. Buhagiar

Fig. 8.2 General view of the Tal-Callus giardino at Wied ir-Rum in the territory of Rabat (Malta). Lush vegetation and reed growth is indicative of perched aquifer springs which originate from a series of rock-excavated galleries

Fig. 8.3 The Dejr il-Bniet perched aquifer gallery at Dingli. This provides the Dejr il-Bniet giardino with a perennial water source

is characterised by thick limestone outcrops containing sinkholes and, often, a network of caves. Karst subsidence structures form due to erosion of calcium carbonate deposits, which readily dissolve by the action of rainwater, and gradually lead to the formation of subterranean caves

(Dolgoff 1996; Skinner et al. 1997; Ford and Williams 2007). Collapse of a cave’s roof leaves a large crater-like depression in the ground, which in the case of Għar il-Kbir and other settlements has been utilised for troglodytic purposes (see Sect. 8.4). Because karst feature settlements occur

8

Cave Dwellers at Għar il-Kbir: Malta’s …

in hard Upper Coralline Limestone, geological formations frequently restrict cave enlargement. Cliff-face settlements are located within the sides of ridges and valleys and involve the occupation of a series of natural or artificially enlarged caves (Fig. 8.4). The majority of the Maltese troglodytic units fall within this category and are often hewn into a brittle Upper Coralline Limestone stratum, locally referred to as the Mtarfa Member (Scerri 2019, Chap. 4). This rock formation is easy to excavate and does not make the process of cave excavation and enlargement as labour-intensive or as time-consuming as is commonly argued. Indeed, the location of most cliff-face settlements suggests that their occupants possessed a sound knowledge of the local geology and hydrology. Mtarfa Member deposits are commonly located only a few metres above the perched aquifer, often successfully tapped by means of underground galleries, ensuring therefore that the rock-excavated settlements and the underlying fields had a perennial water source (Buhagiar 2007). Cliff-face settlements are frequently fronted by a rock terrace, which apart from functioning as an outdoor extension to the limited space offered by the cave interior, also links two or more adjoining caves together. Most Maltese cliff-face settlements were intimately connected to the above described giardino framework and formed part of a series of well-established medieval fiefs, the lifeline of which was determined by the presence of perennial water capture and distribution systems. That a number of giardini were during the Late Medieval period already

Fig. 8.4 General view of the Tal-Merħla cliff-face settlement at Mtaħleb. All caves at Tal-Merħla are excavated into the brittle Mtarfa Member, Upper Coralline Limestone deposit

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engaged in the cultivation of various crops, including fruit production, as revealed by a Cancelleria Regia entry dating to 7 June 1393, wherein the rights of the landholder over the acquired giardini, including the fruit produced by the land, are indicated (Fiorini 2004). Furthermore, seventeenthcentury documentation on the Saqqajja and Għariexem perched aquifer galleries, both at Rabat (Malta), clearly indicates that these predate the Knights period and can therefore be considered as being medieval water-related interventions in an agrarian landscape (Univ. 187 manuscript ff. 1-14).

8.4

The Għar il-Kbir Settlement

Għar il-Kbir is located close to the modern settlement of Dingli (Malta) in an area of high ground known as Misraħ Għar il-Kbir and commands views of Verdala Palace and the Buskett woodland to its north (Figs. 8.5 and 8.6). Adjoining the Għar il-Kbir site are earlier period cart-ruts, Phoenician/Punic shaft and chamber tombs as well as a surprising concentration of ancient surface quarries (Bonanno 2005; Trump 2000). Upper Coralline Limestone of the Tal-Pitkal Member is the predominant geological outcrop, and a garigue-type landscape is prevalent in the surrounding area. The formation of Għar il-Kbir is due to the dissolution of carboniferous limestone by water action, forming karst hollows and depressions. Flanking the east side of Għar il-Kbir is another smaller solution subsidence

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K. Buhagiar

Fig. 8.5 Plan of the Misraħ Għar il-Kbir area showing the location of the Għar il-Kbir troglodytic settlement

Fig. 8.6 General view of the central karst cavity at Għar il-Kbir, around which eight human-excavated caves are located

structure which still awaits proper scientific investigation. Large quantities of rubble infill covered by a terra rossa soil deposit make a substantial portion of this natural cavity inaccessible, but it is probable that this was originally physically linked to the Għar il-Kbir settlement and similarly contained a number of cave-dwelling units (Figs. 8.7 and 8.8).

8.5

Hydrology and Water Management

The hydrology-related infrastructure which provided the inhabitants of Għar il-Kbir with a supply of water still needs to be ascertained. As the perched aquifer underlying the Għar il-Kbir settlement is probably located at a depth of over

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Fig. 8.7 Plan showing the interior of one of the caves at Għar il-Kbir. Dry-stone walls screen the cave entrance and partition the interior into a series of individual spaces, utilised for purpose of human habitation

Fig. 8.8 This section of the solution subsidence structure at Għar il-Kbir has been reclaimed for agricultural usage at an unknown date. Large quantities of rubble infill covered by a terra rossa soil deposit make a substantial portion of this natural cavity inaccessible, but it is likely that this was an extension of the Għar il-Kbir site and similarly contained a number of cave-dwelling units

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30 m below surface level, it is unlikely that this was tapped by means of shaft wells. The option of a water cistern makes more sense, and its presence is confirmed by a 1793 description of the site by Carlo Castone Della Torre, who nonetheless fails to give any details of its exact whereabouts (Eynaud 1989). An extensive field survey of the surrounding area failed to locate this water tank, and there is the possibility that this was destroyed by nearby quarrying works, which at a distance of only 40 m from the western boundary of the cave complex have encroached dangerously onto the site. The remnants of a rock-hewn water canal located in the western section of the Għar il-Kbir site also seem to confirm this hypothesis. Alternatively, the Għar il-Kbir inhabitants could have secured a perennial water supply from a series of springs, both natural and human-excavated, found within a 1 km radius of the Għar il-Kbir site. The springs closest to Għar il-Kbir are located in Buskett valley, and with the exception of a spring flowing through Buskett valley, the remaining three water sources originate from within a series of perched aquifer galleries known as Tas-Sienja, Tas-Sala and Ta’ Rapa (Zammit 1924). These are excavated into the sides of Buskett valley and probably already dominated the hydraulic and agrarian landscape of the Buskett territory in the Late Medieval period.

8.6

Seventeenth and Eighteenth-Century Descriptions of Għar Il-Kbir

Għar il-Kbir is the result of an intelligent adaptation of naturally occurring features made suitable for the needs of a more complex community. The utilisation of a series of caves for human and animal habitation in the Medieval and the Early Modern period was probably encouraged by a long succession of occupational phases which aided the development of a communal way of life (Luttrell 1979). The date for the earliest settlement of the Għar il-Kbir caves is unknown but probably has a long history. Troglodytes were certainly well established by 1544, when a Simone Camilleri di Ghar il-Kbir was mentioned in a notarial act of Notary Brandon de Caxaro (Wettinger 1975). Abela (1647) includes Għar il-Kbir in his list of inhabited areas in Malta and describes the cave settlement as being a grotta vasta e grande (in Italian language, a vast and big cave). Abela gives the number of troglodytes inhabiting Għar il-Kbir as amounting to 117 individuals and describes them as being pastori e pecorai (in Italian language, shepherds and goat herders) and grouped into 27 families. The idyllic setting of the caves and the quaintness of the inhabitant’s life became an attraction for various foreign visitors to the island. The most famous of these was

Athanasius Kircher, a distinguished Dutch Jesuit and mathematician. Kircher reached Malta on the 31 May 1637 and stayed for eight months. Between 8th and 9th June, he was the guest of Fra’ Jean-Paul de Lascaris-Castellar, the then Grand Master of the Order of St John, at Verdala Palace. It was during this stay at Verdala that Kircher was taken to nearby Għar il-Kbir. He was so impressed by the Għar il-Kbir community that he included a vivid description of it in his Mundus Subterraneus published in Amsterdam in 1665 (Kircher 1665). Kircher described the inhabitants of Għar il-Kbir as living a communal life. Għar il-Kbir was accessed through a main entrance, but it was divided into a series of separate caves inhabited by individual families. The caves were provided with sleeping recesses, store rooms and animal pens and were ventilated by shafts which were devised to exclude wind and rain. Large earthenware pitchers were used for the storage of drinking water, and rock-cut shelves and cupboards were used for the storage of food. Long strings of onions and clusters of garlic also hung from the ceiling. At the entrance to the settlement, he was greeted by simply dressed men, women and children. They were tall and strong and reputedly lived to a ripe old age. Kircher also noted that the women were remarkable for their good looks. The cave dwellers were strict vegetarians and lived principally on home-baked bread, cheese and vegetables. Quite interestingly, they refused to touch the fine food that the Grand Master had sent them from his table. It appears that apart from arable agriculture, the troglodytes were also engaged in pastoral activity and cheese production. The women did the house chores and tended to their young. Furthermore, the Għar il-Kbir inhabitants are described as remarkably devout and are reported to have decorated their caves with crosses and holy pictures. Their religious obligations were fulfilled in a nearby settlement, possibly Dingli or the lost village of Ħal Tartarni. The troglodytes appear to have been attached to their settlement and left it very rarely. This might have aided their retaining a linguâ Arabicâ purâ sine ulla italicælinguæ alteriusive mixtura, untur (Kircher 1665).1 Kircher was also informed that when Maronite monks visited Għar il-Kbir, they found that the troglodytes understood their language and could follow mass in Arabic (Fletcher 2011; Borg 1967; Luttrell 1979). Kircher’s description of Għar il-Kbir also apparently served as an inspiration for an early eighteenth-century engraving, printed and published in Leiden by Peter Van der Aa, showing a romanticised scene of everyday life in the settlement (Luttrell 1979; Zammit Ciantar 2000). Another description of Għar il-Kbir by E. Veryard dates to the

An approximate translation of this reads: ‘[…] a pure Arabic language with a mix of Italianate words […]’.

1

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Cave Dwellers at Għar il-Kbir: Malta’s …

closing decades of the seventeenth century, but is largely uninformative. Apart from a reference to the various caves out of which the Għar il-Kbir settlement is composed, Veryard mentions light shafts piercing the caves’ ceiling and the fact that its inhabitants lived there due to custom, not poverty (Veryard 1701). Another visitor to the Għar il-Kbir cave compound was Carlo Castone Della Torre Di Rezzonico. His interest in the site was probably stirred by Kircher’s internationally acclaimed publication, but on visiting Għar il-Kbir in 1793, he was disappointed to find only one inhabitant named Diodoro who was probably over eighty years old (Eynaud 1989). Carlo Castone nonetheless acknowledged that the caves could have housed a larger number of inhabitants. Quite interestingly, Diodoro only inhabited one of the caves at Għar il-Kbir. This was simply furnished and contained a small oven. Grain and cotton provisions were also stacked within. All the other caves apparently fell under the jurisdiction of the Grand Master and were securely locked with wooden doors. Carlo Castone appears to have been fascinated by the cave complex, but describes the descent to the settlement’s entrance as an arduous task. The mention of light filtering into the interior of the central cave by means of a light shaft confirms Kircher’s description of the site. Even more significant is Carlo Castone’s mention of a cistern, which appears to have been located close to the cave-settlement site. The fact that the only inhabitant of Għar il-Kbir near to the end of the eighteenth century was still engaged in some sort of pastoral activity can perhaps be confirmed because Dain offered Carlo Castone ricotta cheese, which the latter refused to consume (Eynaud 1989). Carlo Castone’s account goes against the popular belief that troglodytes continued to reside in this cave complex until the early nineteenth century, when its inhabitants were forcibly expelled by the British administration and were resettled in the nearby villages of Dingli and Siġġiewi. The German artist, Charles de Brochtorff, reportedly painted a scene of this settlement shortly before the troglodyte’s dispersal (Trump 2000; Lewis 1977), but efforts by the present author to locate this painting proved futile.

8.7

The Present-Day Remains at Għar Il-Kbir and the Status Animarum Registers

A flight of badly weathered rock-excavated steps facilitates access to Għar il-Kbir’s principal access point and is flanked on either side by two massive rock boulders, which probably formed part of the roof of the central cavern. Resting against a natural rock outcrop adjoining the cave’s entrance are the remains of a square-shaped building of unknown antiquity. Large irregular masonry of Upper Coralline Limestone was

99

employed in its construction. The building’s connection to the settlement remains unclear, but as a section of the central cave extended beneath this masonry-built structure, it appears to have been internally connected to the cave complex. A series of eight human-enlarged caves are spread over two levels and perimeter the subsidence structure at Għar il-Kbir. The lowermost level houses five caves, all of which are accessed through the central karst cavity (Fig. 8.7). The remaining three caves are located at an upper level and can most easily be accessed from the garigue plain surrounding the Għar il-Kbir cave site. Dry-stone walls not only enclosed the access points to most caves, but also partitioned their interiors into a series of separate units. A detailed analysis of the Għar il-Kbir site revealed that the architectural typology of two upper-level cave units is appreciably different from that of the remaining and could have originally been utilised as Phoenician-Punic tombs, or housed a small Punico-Roman period burial chamber, which was at a later date partially re-cut and re-utilised for the purpose of human habitation (Buhagiar 2003). The circular depression around which most of the Għar il-Kbir caves are arranged was originally covered over. On the other hand, our current state of knowledge cannot help determine which segments of the cavity were roofed over in the Late Medieval and Early Modern periods. According to popular tradition, the ceiling of the central cavity was destroyed because of British period on-site intervention aimed at forcibly expelling the troglodytes from Għar il-Kbir because of poor sanitary conditions (Trump 2000). Nevertheless, it is this author’s suspicion that this area experienced a roof collapse prior to the annexation of Malta by the British forces. Archival research undertaken by the author also helped substantiate this belief (Buhagiar 2003). Demographic records indicate that in the opening decade of the nineteenth century, Għar il-Kbir was already a largely depopulated settlement and the emergent picture discredits the aforementioned eviction theory. On-site field research revealed that the visible material infill in the northern section of the central cave where most cave-dwelling units were located cannot possibly account for a roof collapse. There is, on the other hand, ample proof of roof structural collapse in the southern section of the central cave. In an attempt to better understand demographic trends at Għar il-Kbir, Status Animarum registers dating between 1699 and 1803 were consulted (ACM Status Animarum registers; Buhagiar 1997). The majority of these were compiled by parish priests serving at Dingli and, either listed all family members, or merely the male head for each family. An analysis of these Status Animarum registers reveals that the heyday of the Għar il-Kbir settlement did not extend beyond the closing decades of the seventeenth century. For the whole of the eighteenth century, documentary evidence at no stage records more than a maximum of fifteen

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K. Buhagiar

individuals, amounting to three families, being resident in the caves. This downward trend appears to have set-in even earlier, because the 1699 register only lists one family unit composed of five members as residing within the complex. A slight increase in population was documented in the 1702 register, for which there is the mention of three families residing at Għar il-Kbir. The number of cave inhabitants remained stable until 1728, but Status Animarum entries for 1730 and 1732 only list two families as residing there. A further demographic decline occurred between 1735 and 1736 when only one family unit is recorded. For the years following 1740, Status Animarum records only account for a certain Petrus Galea aged 74 as being resident at Għar il-Kbir. Unless the Dingli Parish Priest responsible for drawing up of the registers was following the practice adopted in 1708, where only the male head for each family was recorded, the Għar il-Kbir community between 1740 and 1776 had practically disappeared. Another slight population increase is recorded in 1796, where mention is made of one couple and a single man described as a separatus, as the only inhabitants of the cave complex. The entries for 1797 and 1803 are somewhat dubious because records refer to individuals living in the regione di Għar il-Kbir. It could be possible that these couples were living in the surrounding countryside and were not actually troglodytes (Buhagiar 1997). Whilst the data in Status Animarum registers on the Għar il-Kbir settlement about the close of the eighteenth century is in conformity with Carlo Castone’s account, an analysis of the remaining data reveals unstable population trends. The emerging scenario seemingly indicates that throughout the eighteenth and nineteenth centuries, most families residing at Għar il-Kbir were only resorting to a troglodytic lifestyle on a temporary basis, until more desirable accommodation became available.

8.8

Conclusion

For centuries, the rural inhabitants of Malta lived at an almost subsistence level. Cave settlements, like other rural structures, portray a marked absence of unnecessary ornamentation and were conceived to be practical rather than fashionable. Troglodytic settlements and any adjoining aboveground vernacular architectural elements are often the result of successful human interaction with the landscape. Their builders did not try to conquer or crush nature, but rather attuned to the challenge posed by topography, landscape and geology. Għar il-Kbir is no exception, and apart from being Malta’s best historically documented settlement, the presence of a substantial infill in sections of the central cavity might preserve stratified deposits, which, if confirmed, would undoubtedly warrant subsurface investigation. In the 1960s and 1970s, several caves at Għar il-Kbir site

were utilised as animal pens, an activity that exposed the cave complex to immeasurable harm. This is fortunately no longer the case, but considering that Għar il-Kbir is Malta’s most frequented troglodytic site, any immediate short-term action plan should ensure the site’s preservation against any further unwarranted disturbance caused by visitors and occasional weekend campers. A long-term action plan aimed at securing the preservation of the geological, archaeological and historical heritage of Għar il-Kbir is essential. Apart from assessing the structural integrity of particularly vulnerable sections of the site, visitor accessibility and safety and safety has to be addressed. Essential future research must include the carrying out of ground penetrating radar surveys in order to enable a better assessment of Għar il-Kbir’s geological and archaeological potential to be made and to possibly pave the way for future scientific excavation of selected areas of the site which would allow better interpretation.

References Unpublished Registers)

Sources

(Manuscripts

and

Univ. 187 manuscript ACM Status Animarum registers for Dingli Parish for the years: 1699, 1702-1703, 1708, 1710, 1715, 1717, 1722, 1728, 1730, 1731, 1732, 1735, 1736, 1740, 1742-1743, 1745, 1758, 1776, 1796, 1797, 1803

Published Sources Abela GF (1647) Della descrittione di Malta Isola nel Mare Siciliano con le sue antichita, ed altre notitie (Facsimile edition by the Melitensia Book Club 1984, originally published in Malta by Bonacota P in 1647. Valletta, Midsea Books Ltd, 242p Bresc H (1975) The secrezia and the royal patrimony in Malta: 1240-1450. In: Luttrell AT (ed) Medieval Malta: studies on Malta before the knights. The British School at Rome, London, pp 126–62 Bonanno A (2005) Malta: Phoenician, Punic and Roman. Midsea Books Ltd, Valletta, 359p Borg V (1967) Fabio Chigi: apostolic delegate in Malta (1634–1639). Vatican City, 528p Buhagiar K (1997) The Għar il-Kbir settlement and the cave-dwelling phenomenon in Malta. Unpublished BA Hons dissertation, University of Malta, Malta Buhagiar K (2003) Medieval and early modern cave-settlements and water galleries in North-West Malta South of the great fault: a field survey and gazetteer. Unpublished MA thesis, University of Malta, Malta Buhagiar K (2007) Water management strategies and the cave-dwelling phenomenon in late-medieval Malta. Med Archaeol 51:103–131 Buhagiar K (2012) Caves in context: the late medieval Maltese scenario. In: Bergsvik KA, Skeates R (eds) Caves in context: the cultural significance of caves and rock shelters in Europe. Oxbow Books, Oxford, pp 153–165

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Buhagiar K (2014) Water management technology as a contributing factor in the development of the rural landscape of the Maltese archipelago: making a case for the late medieval period. Unpublished Ph.D. thesis, University of Malta, Malta Buhagiar M (2005) The late medieval art and architecture of the Maltese islands. Fondazzjoni Patrimonju Malti, Malta, 278p Cousins SM (2010) The Prudhoe landscape history project: a retrogressive study of the landscape history of part of Southern Northumberland. In: Faulkner T, Berry H, Gregory J (eds) Northern landscapes: representations and realities of North-East England. Oxford University Press, Woodbridge, pp 25–39 Dolgoff A (1996) Physical geography. Houghton Mifflin, New York Eynaud J (1989) Carlo Castone Della Torre di Rezzonico: Viaggio di Malta Anno 1793. Midsea Books Ltd, Malta, 72p Fiorini S (1988) Sicilian connections of some medieval Maltese surnames. In: Brincat G (ed) Incontri Siculo-Maltese. Malta University Press, Malta, pp 104–138 Fiorini S (1993) Malta in 1530. In: Mallia-Milanes V (ed) Hospitaller Malta 1530-1798: studies on early modern Malta and the Order of St John of Jerusalem. Mireva, Malta, pp 111–198 Fiorini S (ed) (2004) Documentary sources of Maltese History: part ii documents in the state archives Palermo, No 2 Cancelleria Regia: 1400–1459. University of Malta, Malta, 840p Fletcher JE (2011) A study of the life and works of Athanasius Kircher, ‘Germanus Incredibilis’. Aries book series, vol 12, Leiden, Brill, 7p Ford D, Williams P (2007) Karst hydrogeology and geomorphology. Wiley, Chichester, 562p Kircher A (1665) Mundus Subterraneus, vol 2. Joannes Jansson, Elizeus Weyerstraet, Amsterdam, 322p Lewis H (1977) Ancient Malta: a study of its antiquities. Collin Smythe, England, 168p Luttrell AT (1979) Malta Troglodytica: Għar il-Kbir. Heritage, vol 2. Midsea Books Ltd, Malta, pp 461–465

101 Oosthuizen S (2006) Landscapes decoded—the origins and development of Cambridgeshire’s medieval fields. University of Herfordshire, Hatfield, 192p Rippon S (2012) Historic landscape analysis: deciphering the countryside. Council for British Archaeology, Oxford, p 166 Scerri S (2019) Sedimentary evolution and resultant geological landscapes. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 31–47 Skinner M, Redfern D, Farmer G (1997) The complete A-Z geography handbook. Hodder and Stoughton, London, 352p Trump DH (2000) Malta: an archaeological guide. Progress Press, Malta, 167p Vella HCR (1980) The earliest description of Malta (Lyons 1536) by d’Autun JQ (Translation and notes). DeBono Enterprises, Malta, 102p Vermeulen F (2004) Roads for soldiers and civilians in the Civitas Menapiorum. In: Vermeulen F, Sas F, Dhaeze W (eds) Archaeology in confrontation: aspects of Roman military presence in the Northwest. Academia Press, Ghent, pp 125–42 Veryard E (1701) An account of divers choice remarks, as well geographical, as historical, political, mathematical, physical, and moral: taken in a journey through the low-countries, France, Italy, and part of Spain; with the Isles of Sicily and Malta, and also to the voyage to the Levant. S. Smith and B. Walford, London, 360p Wettinger G (1975) The lost villages and hamlets of Malta. In: Luttrell AT (ed) Medieval Malta—studies on Malta before the knights. The British School at Rome, London, pp 181–216 Wettinger G (2000) Place-names of the Maltese Islands ca. 1300-1800, Malta. Publications Enterprise Group, San Gwann, Malta, 645p Zammit T (1924) The water supply resources of the Maltese islands. Government Printing Office, Malta, 49p Zammit Ciantar J (2000) Life in Għar il-Kbir: a seventeenth-century account by Athanasius Kircher SJ and an engraving depicting it published by Pieter Van der Aa. Dingli Local Council, Malta, 44p

9

Humans as Agents of Geomorphological Change: The Case of the Maltese Cart-Ruts at Misraħ Għar Il-Kbir, San Ġwann, San Pawl Tat-Tarġa and Imtaħleb Derek Mottershead, Alastair Pearson, Paul Farres, and Martin Schaefer

Abstract

Most people will be familiar with wheel ruts caused by the passage of farm vehicles in the muddy fields of soil-covered farming landscapes. However, significantly fewer will have observed ruts of similar dimensions in solid rock. Such features are an enigmatic part of the Maltese landscape. Archaeologists have understandably focused on such issues as the date, purpose and cultural context of the features. However, to the geomorphologist, their field characteristics as described here at four key sites provide a range of evidence for their mode of formation and indeed their role as indicators of environmental change. An experimental geomorphological approach has established that two-wheeled carts could readily have inadvertently formed the ruts in the local limestones of low to medium mechanical strength. Once created, they are indicative of a very effective means of transporting significant loads around Malta. The cart-ruts are discussed in the contexts of both archaeological history and Holocene environmental chronology, and their formation is put forward as indicative of significant and irreversible landscape change.





Keywords

Cart-ruts Geomorphology Anthropogenic Holocene




Erosion




D. Mottershead (&)
A. Pearson
P. Farres
M. Schaefer Department of Geography, University of Portsmouth, Lion Terrace, Portsmouth, PO1 3HE, UK e-mail: [email protected] A. Pearson e-mail: [email protected] P. Farres e-mail: [email protected] M. Schaefer e-mail: [email protected] © Springer Nature Switzerland AG 2019 R. Gauci and J. A. Schembri (eds.), Landscapes and Landforms of the Maltese Islands, World Geomorphological Landscapes, https://doi.org/10.1007/978-3-030-15456-1_9

9.1

Introduction

9.1.1 Geomorphology or Archaeology? The cart-ruts, so widely distributed across Malta and Gozo (Fig. 9.1), have long excited archaeologists. So why might they be studied by geomorphologists? Are they a part of archaeology or a part of geomorphology? Where does their study really belong? The answers to these questions really lie in the focus of the reader’s interest, whether it be on the history of ancient peoples or that of the physical landscape. It is a fact that the ruts are created by the actions of humans; they are also erosional landforms. They may therefore be defined as landforms of human origin, that is, anthropogenic landforms.

9.1.2 Previous Studies Numerous studies have demonstrated the impact of human activity on the Mediterranean landscape and how it can affect natural landscape processes in various ways (Grove and Rackham 2002; Sadori and Narcisi 2001). For example, poorly managed tree clearance for fuel or arable and livestock farming can irreversibly diminish natural vegetation cover. This in turn modifies the interaction between erosional agents and the land surface and leads in particular to soil erosion, subsequent downslope sediment accumulation in river valleys (Farres 2019, Chap. 12) and, in due course, stripping of the entire soil cover to expose the bedrock beneath. If solid bedrock emerges at the surface, then it too can be exposed to erosive forces of human action leading to the creation of more durable landforms in solid rock. The cart-ruts of Malta are a prime example of this set of processes. Cart-ruts are not unique to Malta. They have been reported widely from Europe, North America, western Asia and North Africa (Magro Conti and Saliba 2005). Malta, 103

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Fig. 9.1 Location of key sites (in black star symbol) and distribution of known cart-rut sites (in black dot symbol) according to Magro Conti and Saliba (2005). Note that the sites are concentrated on the higher

ground associated with Upper Coralline Limestone in North and West Malta and south Gozo

however, appears to have the greatest concentration of cart-ruts known to date. Contemporary descriptions of the cart-ruts of Malta were recorded by the Maltese historian Abela (1647) and in 1761 by the Swedish botanist Forsskål (1951). The latter wrote: “The country roads are of pure rock. The ruts for the wheels are mostly deep, but at some spots filled in and even” (Translation by Salto 2004). This is a clear implication that Forskåll observed roads in the form of bedrock surfaces with incised tracks that were utilised by horse-drawn wheeled vehicles such as carriages and light carts, and that they were repaired in places with backfill. There is an implicit assumption that road and ruts are causally related, and no suggestion that this association is in any way remarkable. Archaeological descriptions have since been published by numerous authors (Zammit 1928; Evans 1934; Gracie 1954; Parker and Rubinstein 1984; Ventura and Tanti 1994; Trump 1993, 2000), culminating in a review by Hughes (1999) and

the Culture 2000-sponsored project report edited by Magro Conti and Saliba (2005). Little experimental work has been undertaken with the exception of that undertaken on behalf of the BBC in 1955 (BBC 1955) in which various reconstructed vehicles were hauled along the cart-ruts. However, a clear and definitive conclusion did not emerge. The principal questions regarding the type of vehicle involved, whether wheeled cart, sled or travois (animal-drawn trailing shafts), and their age still remain.

9.1.3 The Cart-Ruts: Their Characteristics, Formation and Vehicular Capacity In this volume, it is appropriate to adopt an explicitly geomorphological approach, and in this context, erosional forms such as cart-ruts are interpreted on the basis of their geomorphology alone. This embraces their geomorphic form

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Humans as Agents of Geomorphological Change …

and their relationships to local geomaterials and topography. Drew (1996) and more recently, using a geotechnical approach, Mottershead et al. (2008, 2010) present studies of this kind. The latter consider the balance between the resistance properties of the local rock and the force required to overcome them, before designing a vehicle capable of exceeding the resistance of the rock and eroding it. A fundamental starting point in addressing the question of how the ruts might have been formed is to define their field characteristics, summarised as follows (Mottershead et al. 2008): a. They occur as paired parallel grooves incised into bedrock and extending up to several hundred metres in length. b. Each rut pair possesses a constant gauge (distance apart) of ca. 1.40 m, although this may vary slightly between rut pairs. c. The width of a rut ranges from 0.04 to 0.25 m, with depth variable up to a maximum of 0.675 m (Gracie 1954). d. In cross section, they are commonly V-shaped channels with a rounded floor; the largest ruts tend to have a rectangular box cross section. e. Some rut cross sections show multiple grooves with two or three channel floors, always replicated in both members of the rut pair. f. Locally, they may divert in order to avoid local obstacles. The cross section form of the ruts represents the footprint of the vehicle and provides significant clues regarding the morphology of the wheel or runner which carved them. Cross section form throughout the rut sites varies substantially, especially with respect to width. The most precise evidence of wheel or runner form is provided by the most restricted cross sections, which most closely represent those of the cutting agent incising into the rock. The cross section form of such ruts is that of a canyon narrowing downwards with linear sides which grade into a slightly rounded floor, approximately 40 mm in width (Fig. 9.2a). Observations of several sections confirm this as a fair representative value of minimum rut basal width. The simplest form of wheeled vehicle is the two-wheeled cart, which was traditional in Malta in historic times (Forsskål 1951) and may even have dated from much earlier. The dimensions of the narrowest ruts therefore indicate a maximum wheel tread (breadth) responsible for their formation of 40 mm, and an axle clearance (wheel radius) of at least 70 cm. On the basis of this information, the materials required to construct a vehicle with a gauge of 1.4 m can readily be estimated and quantified, a process termed reverse

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engineering. Mottershead et al. (2008) show that a two-wheeled cart constructed of timber, a material readily available to humans from Neolithic and later times, would weigh about 0.25 ton. By taking account of the mechanical strength of the local rocks, they showed that such a vehicle would, even unladen, be capable of causing erosion of the weakest rocks when they are wet. In dry conditions, even the strongest rocks in which ruts are formed, the Xlendi Formation rocks at San Pawl tat-Tarġa, would be eroded by the passage of a two-wheeled cart with a load of just one tonne. This is a clear demonstration of the ability of a two-wheeled wooden cart to erode the mechanically weak limestone rocks of Malta. Such a cart would, depending on the robustness of its construction, be able to carry a load of perhaps a few tonnes, a very valuable asset in the circumstance. A sled, however, would be ruled out by such mechanical considerations, since any significant load spread across the area of its runners would create so much friction that it would require an inordinate amount to energy to move it. With respect to the travois hypothesis, there is simply a lack of evidence throughout the Central Mediterranean that such vehicles were known. Wheels, however, have a known history extending back more than 5000 years in southern Europe; they fit the historical context, the geometric and geotechnical facts evident in the field, and they are capable of doing a very effective job of transporting significant loads with great efficiency.

9.2

Geographical Setting

9.2.1 Distribution The Maltese cart-ruts are distributed in isolated fragments throughout the islands on exposed surfaces of the prevalent limestones. In their gazetteer, Magro Conti and Saliba (2005) document the occurrence of some 35 km of ruts across 186 sites (Fig. 9.1). The rutted trackways are widely distributed across both Malta and Gozo, with particular concentrations on the uplands formed by the Upper Coralline Limestone. They continue to be discovered in urban areas, and such finds strongly imply that others may formerly have existed in such areas and remain buried by later urban development.

9.2.2 Topographic Relations In view of urban development, the relationship of the surviving cart-ruts to topography may not be wholly representative of their original distribution. They may, however,

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Fig. 9.2 Rut cross sections: San Pawl tat-Tarġa a The rut is transverse to the 12° slope; hence, its vertical axis is tilted to the same degree. Note V-shaped cross section with linear walls and rounded floor at the cut. Subsequent to the abandonment of the rut, calcite has crystallised on the floor to form a horizontal surface. Source Photograph reproduced

provide potentially instructive indicators of their purpose, as follows: a. In the broader context, ruts are often clearly related to major landscape features, such as cols or scarp slopes. b. Concentrations may occur at regional route nodes, especially crossing points of high ground. c. They may incorporate diversions around a hollow or shaft in the bedrock in the form of a bypass (Mottershead et al. 2008, 2010). These observations suggest a network of routeways designed to minimise difficulties posed by relief barriers and locally steep slopes. It is not unreasonable to suggest that the cart-ruts represent fragments of a formerly extensive regional pattern of routeways which enabled the transport of relatively heavy loads of many kinds across the Maltese Islands. Whilst the relations between ruts and topography at the regional scale are clearly explicable, their local relationships with terrain pose interesting questions about rut development. They may: a. incorporate duplicate routes which diverge and rejoin, sometimes forming complex anastomosing patterns, and b. unnecessarily ascend a steep scarp when a nearby easier line is ignored. These questions are explored through the field evidence in the key site descriptions.

D. Mottershead et al.

from Mottershead et al. (2008) by kind permission of Cambridge University Press. b Misraħ Għar il-Kbir: Rectangular box cross section. Enlargement of rut below confluence, suggesting that rut width is a function of traffic frequency

9.3

Geological and Geomorphic Setting

The Maltese cart-ruts are concentrated on outcrops of Upper Coralline Limestone which tend to form the more elevated and exposed terrains of north and west Malta (Scerri 2019, Chap. 4). A limited number of ruts occur also on the Globigerina and Lower Coralline Limestone outcrops. These rocks are composed of CaCO3 and are vulnerable to solution by rainwater falling on the exposed rock surface or percolating through overlying soil, and to groundwater penetrating the rock itself. As the limestone surface weathers away, any insoluble residue will accumulate at the rock surface to form an overlying soil. Water penetrating into the rock through joints will, over time, create solution joints and shafts. These processes will determine the nature of the surface and subsurface terrain over which any vehicles may later pass. Any resistant limestone exposed for an extended time in a Mediterranean climate would have become covered by terra rossa material (Durn 2003), reddish in colour and composed of silt and clay. These soils are formed by the accumulated insoluble residue from the dissolution of the soluble limestone, augmented by air fall deposition of windborne material of desert and volcanic origin. Once the surface vegetation cover was broken by the passage offeet, hooves and wheels, the silty soils would be directly exposed to erosional agents, and it is likely that their textural and other properties allowed them to be readily eroded. They would readily slurry and be carried away by overland flow during rainstorms, to be washed down joints, fissures and shafts

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Humans as Agents of Geomorphological Change …

in the limestone surface or deposited on lower slopes. When dry, the small soil particles would be readily transported away by winds. Erosion of such materials takes place far more rapidly than their replacement by the slow soil-forming processes of limestone solution (Farres 2019, Chap. 12). Whilst geotechnics can explain the incision of ruts into solid bedrock, they do not explain the sometimes incongruent relationships between the ruts and the rockhead relief (the buried topography of the bedrock surface). They do not necessarily explain their sometimes curious and discordant relationship with local topography. These questions are explored at key sites below.

9.4

Key Landforms (and Landscapes)

It is worth noting that the imagery dated 2017 (15 June) and 2013 (15 April) available on Google Earth Pro shows the rut patterns very clearly (at 300-m eye height and below). It is recommended that these images are viewed as an accompaniment to this section.

9.4.1 Key Site: San Ġwann The site (approach from junction of Il-Ġjaċinti/ Mensija Road; 35.911°N, 14.478°E) is located in Mensija, St Julian’s Heights, and is also referred to as Minsia (Zammit 1928). In contrast to its appearance on aerial photography flown in 1923 (Fig. 9.3), this site, some 150 m by 45 m in area, is now hemmed in by urbanisation. It offers two features of interest. First, it possesses a perfect example of a simple straight cart-rut. Secondly, its planform provides a key insight into the way in which cart-ruts developed. This site is located on Lower Globigerina Limestone. At the north end, bedrock forms a smooth surface devoid of obstacles across the summit of a gentle rise. A single continuous and very well-defined rutted trackway incises this surface (Fig. 9.4), forming a north/south routeway. Closer inspection shows a second parallel (but faint) rut pair, overlapping but independent of the former. Both are visible, one clearly and the other faintly, on Google Earth 2013 imagery. As with so many interpretations of these features, one can only speculate as to why the carters did not confine themselves to one single route across this section. This raises the question of why the initial route (presumably the deeper one) was overlooked by those who preferred the alternative. Maybe the deeper and wider rut was becoming unsatisfactory in some way that can only be surmised. In marked contrast, the surface form of the slightly lower ground to the south shown in the aerial image (Fig. 9.3) is irregular, pitted by a dense pattern of roughly circular depressions.

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Now rather less visible at ground level due to the vegetation growth, these are karstic solution hollows typically formed in limestone terrain beneath a soil cover now removed by surface erosion. In this area, the single rut pair, in contrast to its singular form on the summit plateau, bifurcates and rejoins. It is pertinent to consider whether one branch might have been an original routeway, with the loop as a later development. Consideration of the planform alone suggests that the western branch is (slightly) more direct in connecting the two trackway junctions and, therefore, the more likely to be an initial route. Evidence which throws further light on this is the nature of the southern junction at 35.91095°N, 14.47788°E (Fig. 9.5). Close examination shows this to be a trifurcation in which the original single trackway splits into three separate rut pairs. It implies a stepwise lateral shifting of the routeway (eastwards; to the R in photo) away from the original line. Two inferences follow from these observations. First, a problem had become apparent with the initial route, which was not detected by the carters when they first established it, and, secondly, the problem continued to get worse despite and during their attempts to bypass it. Close investigation of the terrain carrying the western branch, however, reveals a substantial depression in the ground surface up to one metre in depth. This is visible on the historic aerial photograph. It is now occupied by a large fig tree, visible on the 2013 Google Earth image. This is interpreted as a karstic depression, a solution doline which in its initial condition would have been buried by a soil infill. The inferences above suggest that it was not visible at the time the route was initiated. Field evidence from a second key site (San Pawl tat-Tarġa) makes a major contribution to explaining these observations.

9.4.2 Key Site: San Pawl tat-Tarġa (Naxxar) This site (approach from 35.926°N, 14.438°E) is also known as T’Alla w’Ommu (Maltese: Of God and His Mother) (Magro Conti and Saliba 2005). It lies below a col breaching the crest of the Victoria Lines escarpment. On the lower part of the escarpment, an exposure of the Xlendi Member of the Lower Coralline forms a subsidiary scarp and a sloping topographic shelf (Fig. 9.6). The absence of any previous soil cover exposes the Lower Coralline Limestone rock surface. A number of rutted trackways cross the shelf en route for the col towards Naxxar. Figure 9.6 shows the remarkable symmetry between the trackway and the modern road which both utilise a hairpin bend in ascending the Xlendi scarp, presenting a mirror image in planform. From 35.92552°N,

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Fig. 9.3 San Ġwann site (N at top). The roughly circular dark areas in the SE corner are solution hollows in the exposed limestone surface. The dark area covering the western rut is a fig tree rooted in a solution hollow. The bifurcation is some 60 m long. Source Base photograph reproduced from Zammit (1928); copyright Antiquity Publications Ltd.

14.43699°E the hairpin trackway joins others from the SW in adopting a climbing course oblique to the contours and ascending the shelf. On the shelf itself, the trackways form freely wandering patterns in which they bifurcate and rejoin. In a zone 25–35 m north of a WW2 anti-aircraft tower, trackways from both NE and NW converge towards the col, confirming this as a routeway of regional significance between the lowlands to the north and the region to the south of the escarpment. This site offers a rare opportunity to study a rut in cross section, where an incised footway intercepts a rut pair at 35.92650°N, 14.43911°E. Here, the cross section is shown as a V-form (Fig. 9.2a) with a rounded floor, the width of which provides a critical value for the modelling of a wheel

rim conforming to the rut specifications and thereby capable of creating the ruts. The centre line of the rut cross section is tilted some 12° in the downslope direction according to the slope across which the trackway traverses. Additionally, the rut floor in cross section is in part horizontal, creating an asymmetry. This is created by the crystallisation of calcite from rainwater ponded in the base of the rut and represents a post-formation modification of the rut. Considerable variations exist across the site in both rut cross section shape and basal width. Some authors have speculated that V-form and rectangular ruts were created by different wheel types, solid wooden or metal-shod, respectively. There is currently no supporting evidence for the latter. From a modelling viewpoint, it is safest to assume a

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Fig. 9.4 San Ġwann site, looking south. A clean-cut linear rut crosses the plateau surface, faint traces of a second rut pair on the baulk and at L. Source Photo reproduced from Mottershead et al. (2010) by permission of Geological Society of London

Fig. 9.5 San Ġwann. The trifurcation at the southern junction. Rut 1 heads towards the fig tree marking the solution hollow which is the obstacle to traffic; two further rut pairs can be identified which show an incremental shift to the R in attempting to avoid the obstacle. Source Photo reproduced from Mottershead et al. (2010) by permission of Geological Society of London

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Fig. 9.6 San Pawl tat-Tarġa (East at Top). Remarkable symmetry of the track starting centre L and the hairpin of the modern road, which form a mirror planform image as they both ascend the lower scarp and turn up towards the col. On the structural bench formed by the Lower Coralline beds tracks appear to roam freely, bifurcating and rejoining. Source Base photograph reproduced from Zammit (1928); copyright Antiquity Publications Ltd.

wooden wheel which is likely to become worn through traversing the rock and develop a rounded rim in cross section, consistent with a rounded rut cross section. It is then entirely possible that carts with a wheel gauge varying slightly from the norm, or slightly loose and wobbling wheels, will widen the ruts over time, leading to a wider basal cross section. For modelling purposes, however, the narrowest ruts provide a minimum value for the wheel footprint. This site is also notable for good examples of discordant relationships between the rut routeway and the local terrain. These can be either topographic or structural discordances. Topographic discordance occurs when a rut traverses a topographic obstacle, causing unnecessary difficulty for the vehicular passage when there is a much easier alternative routeway nearby. An example to this is where a rut traverses a local scarp of up to 0.5 m, when adjacent to it is a ramp of far less taxing gradient (Fig. 9.7). Structural discordance occurs when a rut encounters a geological structure which obstructs its path. This occurs, for instance, when a rut is found to pursue a route directly over a karstic shaft within the limestone. This occurs at 35.92590° N, 14.43805°E where a shaft of unknown depth but at least several metres, in which large shrubs are now rooting, interrupts the trackway of one of a pair of ruts. Duplicate and

even triplicate rut pairs are developed diverting the trackway aside from the shaft. This double diversion can be interpreted similarly to that at San Ġwann, where instead of a vertical shaft, it was a broad solution depression that presented the obstacle to progress. An explanation of these discordances is provided by the nature of the relationship between rockhead relief and soil cover as displayed locally in the section exposed above the quarry at 35.925036 N, 14.438077 E (Fig. 9.8). Here, a remnant of a formerly more extensive soil cover can be found covering the rockhead relief below. When the rockhead relief is covered by soil, it would be invisible to anyone traversing the surface above. If the soil were stripped away in thin layers, the rock surface would be revealed only incrementally as it emerged through the gradually thinning soils. On first exposure of the bedrock surface following thinning, the high parts of the rockhead relief would be first exposed. These are shown in the section generally to be rock plateaux, punctuated by pits and shafts filled by soil. Cart-ruts that developed in the soil above would become superimposed on to the plateau surfaces in which the soil-filled hollows would appear as minor soft depressions. At this stage, the true magnitude and nature of these obstacles would not be identifiable, and there would be

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Fig. 9.7 Incongruent relationship between trackway and topography. The ruts here ascend a 0.5 m scarp when an alternative gentle gradient is available nearby (San Pawl tat-Tarġa). Source Photograph reproduced from Mottershead et al. (2010) by permission of Geological Society of London

Fig. 9.8 Modelled sequence of soil stripping showing the progressive emergence at the surface of the rockhead relief through times t0–t2. The section is approximately 2 m high. San Pawl tat-Tarġa. Source Image reproduced from Mottershead et al. (2010) by permission of Geological Society of London

no apparent need for substantial route change. In wet conditions, however, the sticky silt and clay would be walked out by feet, hooves and wheels, leading to rapid erosion and deepening of the hollows and a need for consequent avoidance with a bypass. Only with further stripping of the soil and consequent increasing exposure of the vertical shaft would its true magnitude and nature become apparent, as an obstacle to wheeled vehicles. Thus, by linking inferences made from observation of cart-rut planform, their geomorphological relations and a geological cross section, an explanation emerges for their origin, development and relationship with environmental

change. The diversion of the ruts around the shaft at Naxxar appears to duplicate that at San Ġwann and thus confirms its interpretation.

9.4.3 Key Site: Misraħ Għar il-Kbir Misraħ Għar il-Kbir (approach from 35.853°N, 14.398°E) is a broad col across a watershed ridge trending NE from the Dingli cliffs. The surface is formed by Tal-Pitkal strata of the Upper Coralline Limestone, a chalky limestone of low mechanical strength (Scerri 2019, Chap. 4). In the previous

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Fig. 9.9 Major ruts, quarries and the Punic rock tomb at Misraħ Għar il-Kbir. Note the quarries believed to be of Roman age in the north-east corner of the map, and the Punic rock tomb in the west. The map was produced through a combination of field survey and photogrammetry. Source Map is reproduced (with amendments) from Mottershead et al. (2008) by kind permission of Cambridge University Press

chapter (Buhagiar 2019, Chap. 8), it was shown that the area of Għar il-Kbir is the best-documented site associated with troglodytic communities. With specific reference to the presence of cart-ruts at this site, these are present across an area extending for ca. 0.8 km along the ridge, and 0.3 km laterally (Fig. 9.9). The ruts here offer a number of more widely applicable insights into rut formation, variation and age. Rut tracks lead away from the site in at least five directions suggesting that this was a place of considerable significance. Whilst its topographic position at a col may have conferred importance on it as a nodal point where regional routeways converged, the presence of multiple quarries shows that it was also a source of a valuable resource, in this case building stone. A notable feature of the overall rut pattern is the existence of swarms of quasi-parallel rut pairs, several running approximately N–S, but others trending away towards E. They appear to lack the anastomosis of the San Pawl ruts (above) but possess a discernible pattern of their own. The tracks trending E disappear close to a farm building

(Fig. 9.9) which sits within a compound of soil retained by stonewalling. Significantly perhaps, at the opposite side of the enclosure some 150 m distant, ruts leading towards an ancient quarry also disappear beneath the same enclosure, suggesting a direct link between the quarry and the northern exit. A swarm of ruts approaches both N and S boundaries of the site, each converging on an exit towards a valley routeway. The prominence of the ruts may simply be a measure of the amount of traffic across this site, or the high erodibility of the mechanically weak rock, under a heavy weight of traffic. The convergence of the ruts towards this zone of quarries and dispersal therefrom towards surrounding valley routeways suggests a vigorous trade in a high demand commodity, in this case building stone. A notable feature at the scale of the individual rut is the trackway junction at 35.85268°N, 14.39712°E, a feature so reminiscent of a railway that archaeologists dignified it with the title of “Clapham Junction” (a British railway location with a complex pattern of multiple tracks). Here, two sets of multiple tracks converge into a single track. The tracks below the junction carrying the combined traffic have a

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trapezoidal cross section with a flat floor up to 250 mm wide. The marked widening of the rut below the junction suggests that it is due to the weight of traffic rather than the wheel cross section. Just a slight wobble of a wheel would be sufficient to cause increased lateral abrasion and, once initially widened, then scope rapidly increases for further lateral wheel movement. A tomb, believed to be of Punic age (Trump 2000), intersects a pair of ruts at 35.85149°N, 14.39649°E (Fig. 9.9). The cross-cutting of the ruts by the excavation of this tomb indicates that these particular ruts predate the tomb and therefore must be >2700 years in age. This is one of the few directly quantifiable clues to the age of the ruts. Furthermore, the quarries on Fig. 9.9 show partially excavated dimension stones of a characteristic Roman size, 1.5  0.5  0.5 m, suggesting that quarrying took place in Roman times (2400–1460 BP) (Magro Conti and Saliba 2005). These two features provide strong evidence for carting activity both prior to and during the Roman period.

9.4.4 Key Site: Imtaħleb This site (approach from 35.8769°N, 14.3613°E) is also known as Għar Żerrieq (Trump 2000) and Għar Ilma (Magro Conti and Saliba 2005).

Fig. 9.10 Toppling failure at the clifftop has detached a rock mass subsequent to the formation of the rut. In this way the ruts can be used as a geomorphic marker, indicating that clifftop failure has taken place probably within the last 2500 years, and may also be a contemporaneous process. It is unclear where the ruts were heading, and any

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The longest continuous set of cart-ruts in the Maltese archipelago (approx. 450 m) survives at Imtaħleb and in one of the most spectacular settings. The ruts are mostly very well preserved and are easily observed using Google Earth Pro skirting a 30-m cliff of Upper Coralline Limestone. Collapse of the cliff has truncated one pair of ruts (Fig. 9.10) the debris from which has long been consolidated into the cultivation plots at the base of the cliff. The ruts here show very similar characteristics to those at the preceding key sites above in planform and dimensions. A particular feature of the ruts at this site, however, is the sharply defined quasi-rectangular rut cross section (Fig. 9.11), which several authors have argued was caused by a metal tyre bonded to the wheel rim. A major implication of this is that the wheel must postdate the acquisition of metalworking technology. A further significant feature at Imtaħleb lies in the existence of rectangular hollows (typical length = 50 cm, width = 35 cm and depth = 25 cm) within the raised baulk between a pair of ruts running for some 43 m, akin to a ladder laid horizontally. This feature is given added significance by its close proximity to and likely association with the quarries at the site as the cart-ruts slope gently upwards from the quarry floor. As noted above, the Upper Coralline Limestone was a valuable building material. However, the flatness of the Imtaħleb site offered no natural benches from which cut

evidence from the rockfall debris below is now lost. It is notable, however, that other ruts to the immediate north of this location trend dangerously close to the clifftop, suggesting that rockfall may also have affected other parts of this cliff

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Fig. 9.11 Rut features at Imtaħleb: Rectangular hollows with separating rock bars in the baulk between the ruts. a Their regular form makes it clear that they have been deliberately cut using some kind of tool. This track climbs a gradient at the quarry exit. It is surmised that the bars afford greater traction required to move loaded carts leaving the quarry, and these forms are perhaps more likely to be of benefit human feet rather than hooves. Road and car park visible in background.

blocks could be loaded readily on to carts and transported downslope as at Misraħ Għar il-Kbir. It would appear that transport of the material from the quarries at Imtaħleb would require the pulling of a stone-laden cart up from the quarry floor to the level of the surrounding land surface for transport elsewhere. Such an operation would require considerable effort and rely on having sufficient grip to negotiate the slope. Evidence of parallel transverse grooves providing grip for some form of traction has also been observed by other authors at several sites including Fuq il-Qawra, Dwejra on Gozo and Misraħ Għar il-Kbir. Trump (2000) observed that there was no evidence of wear between the cart-ruts which would be expected if the means of traction of the carts was a draught animal. Imtaħleb demonstrates that the means of traction was located ahead of and aligned central to the direction of travel. It can feasibly be argued that the regular and pronounced nature of the rectangular hollows would have presented more hindrance than help to four-legged draught animals but would have provided suitable assistance to humans. The uniqueness of the Imtaħleb site demonstrates how difficult it is to draw broad conclusions regarding the cart-ruts. It suggests that their age postdates the start of the Iron Age in Malta and allows the possibility of rut formation from pre-Roman time until the modern historic era. The type of cart and its means of traction and wheel characteristics may have varied over time with technological development and also, as in this case, with its local function.

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b A sharply featured rut cross section, showing several abrasion levels. It is difficult to see how such forms could have been created by wooden wheels, thus many authors interpret these as having been formed by sharp-edged metalled wheels, in which case they cannot predate the Iron Age and neither can their usage in recent historic time be excluded. (Steel tape is 5 cm in diameter)

9.5

Conclusion

9.5.1 A Model of Cart-Rut Evolution It is now evident that humans were responsible for major contributions to Holocene environmental change in causing both bedrock erosion in the form of cart-ruts and also the soil erosion which preceded it (Carroll et al. 2012; Marriner et al. 2012). A simple tabular model of their contribution to cart-rut formation is presented in Table 9.1. Here, it is shown how the changing nature of the surface is likely to influence local route selection as the formerly buried obstacles to traffic gradually become apparent and then increase in severity. At to, when the rockhead relief was covered by soils, it would be invisible to anyone traversing the surface above. The choice of local route over the landscape would be independent of the underlying buried rockhead relief. Local routing decisions would necessarily be guided by visible features such as local topographic or vegetational constraints. On first exposure of the bedrock surface following a general thinning of the overlying soil (t1), the roughly planar surface of the plateau areas of rockhead relief would appear, upon which the wheels would impinge and begin to incise the rock surface during their passage, thus initiating the rut patterns visible today.

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Table 9.1 Model of environmental change, and the consequent development of ruts in bedrock (t0 = initial state; t1 = intermediate state; t2 = current state)

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Time

Nature of surface

Route selection

Surface development

t0

Smooth ground surface over soil; occasional rises and depressions. Vegetation cover of varying density

Ease of trafficability strongly determined by vegetation cover. Route selection favours less densely vegetated areas on a uniform ground surface

Ruts develop in the silt/clay soil, with graded floors, and will attract subsequent traffic by easing its passage

t1

Knolls and plateaux of bedrock begin to appear, separated by soil-filled hollows carrying rutted trackways

Traffic will tend to follow existing ruts on to the intermittent bedrock outcrops

The bedrock outcrops themselves start to become rutted. The hollows gradually deepen as the sticky clay is walked out by passing feet, hooves and wheels

t2

Irregular surface of bedrock widely exposed, revealing sharp hollows and deep shafts

Rutted tracks become laterally uneven; deep shafts require by-passing

Bedrock surface hardens, preserving the rutted form

With continuing use and deepening of the rutted trackway, shafts would become increasingly exposed and the infilling soil further eroded until the hollows become too deep to be traversable by vehicles. By this stage (t2), it would be necessary to bypass such obstacles. Further deepening of a shaft by erosion would render the first bypass impassable and lead to the creation of a second bypass. This sequence implies that the initial land surface form of the rutted areas at San Pawl tat-Tarġa and San Ġwann was very different to that visible today and, furthermore, that the local environment underwent continuing change during, and probably because of, the continued usage of the rutted trackways. On the exposed slope at San Pawl tat-Tarġa, it is very possible that intense accelerated erosion by human and vehicular traffic could cause the loss of most of the soil material within tens to hundreds, rather than thousands of years following which the thin hillslope soils would become replaced by the current bare limestone topography (Mottershead et al. 2010). The evidence presented here confirms the conclusions of previous authors in respect of erosion of a former soil cover (Fenton 1918; Gracie 1954; Trump 1993).

9.5.2 Dating the Cart-ruts A fundamental problem in dating the formation (and abandonment) of the cart-ruts is that they contain so little information regarding their age. This circumstance has led to much speculative conjecture in the archaeological literature. Clues must therefore be sought by inference from contextual evidence of early human activity in Malta, such as environmental proxies in sediment cores, archaeology and documented history. An indicative upper age limit for the Maltese cart-ruts may be defined by the age of the earliest currently known

wheeled vehicle. This is recorded from Slovenia, on the fringe of the Mediterranean domain, and dated to 5350–5150 BP (Velušček 2009). This, however, is not an absolute date for the origin of the wheel for two reasons. First, future investigations may unearth an even older wheel in Europe or elsewhere, and secondly, given the advanced nature of the Maltese Temple culture with the largest megalithic structures in the known world of that time, it is not inconceivable that the early Maltese may independently have discovered the wheel, only for a subsequent culture to lose it. The Slovenian date, therefore, is not an immutable signifier of the origin of the wheel but is at least the best one currently available. The pollen record (Carroll et al. 2012) shows the impact of humans in forest clearance from 7500 BP and the spread of cereal cultivation from 6800 to 4300 BP. The combination of these activities would have created conditions conducive to the initiation of soil erosion (a factor associated with rut creation). Marriner et al. (2012) show that the relatively humid climate and soil disturbance associated with agriculture combined to flush large volumes of eroded soil from river basin catchments to form sediments within the Burmarrad marine embayment in the period 7500– 4500 BP. This environmental evidence overlaps with the earliest-known phase of the wheel in prehistory, and if wheeled vehicles were in use in Malta as early as the late Neolithic age, then they would have contributed to that particular phase of land surface erosion. A further temporal marker is provided by the cross-cutting relationship between cart-ruts and some vertical shafts of Punic tombs of known age (2700–2218 BP). Where the vertical shaft of the tomb is cut cleanly through a rock surface bearing cart-ruts, intersecting the rut bed cleanly at 90°, then the ruts must predate the shaft. (In contrast where a rut encounters a pre-existing vertical solution shaft, the rut wears downwards into the margin of the soil-filled shaft declining into it before being abandoned by

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the carters). Thus, at least some ruts evidently predate the end of the Punic period and would have been formed by 2218 BP at the latest. There is contemporary written evidence dating from Punic/Roman times of a prominent quarrying industry in the Maltese islands (Magro Conti and Saliba 2005). This provides support for the interpretation of the association between the cart-ruts and the ancient quarries such as Misraħ Għar il-Kbir with their dimension stones as indicating a Roman age. It is quite possible that subsequent historical periods have seen the initiation of new cart-ruts according to local circumstance and need. Forsskål (1951) records that the cart-ruts were utilised in the eighteenth century and were subject to erosional wear and subsequent repair by backfilling in order to maintain a usable routeway. This does not, however, imply that the ruts were initiated during that period, for they may have been of considerably greater vintage. Unless and until archaeological or other evidence can be found in direct association with ruts themselves, however, then they are perhaps better interpreted as having formed in association with a phase of rapid soil erosion, sometime between the late Neolithic and the late Roman periods. The concentration of these uncommon and intriguing landforms, in addition to their archaeological significance, their role in contributing to environmental change and the threat to their preservation posed by urban, agricultural and industrial development strongly suggests that their conservation should be a priority. These factors underpin Schneider’s (2001) claim that these sites merit World Heritage Status. Acknowledgements The authors would like to thank the staff of the Malta Environment and Planning Authority (MEPA), in particular Carol Agius and Gino Debono, for their support in the provision of control point data of the cart-rut sites. Thanks are also due to the students of the Department of Geography, University of Portsmouth, for their hard work and endeavour during the surveying and GIS field trips between 2004 and 2014. DM acknowledges financial support for fieldwork costs from the Department of Geography, University of Portsmouth.

References Abela GF (1647) Della descrittione di Malta Isola nel Mare Siciliano con le sue antichita, ed altre notitie (Facsimile edition by the Melitensia Book Club 1984, originally published in Malta by Bonacota P in 1647. Valletta, Midsea Books, 242p BBC (1955) Buried treasure: 2. two maltese mysteries; 13.06.1955. BBC Inf Arch CC:052379 Buhagiar K (2019) Cave dwellers at Għar il-Kbir: Malta’s best documented troglodytic community. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 91–101

D. Mottershead et al. Carroll FA, Hunt CO, Schembri PJ, Bonanno A (2012) Holocene climate change, vegetation history and human impact in the Central Mediterranean: evidence from the Maltese Islands. Quatern Sci Rev 52:24–40 Drew DP (1996) Cart-ruts and karren: karstification and human impacts in Malta. In: Fornòs JJ, Ginès À (eds) Karren landforms (International symposium, Soller 1995) Universitat de les Illes Balear, Palma de Mallorca, pp 403–420 Durn D (2003) Terra rossa in the Mediterranean region: parent materials, composition and origin. Geol Croat 56(1):83–100 Evans EMP (1934) Maltese cart-ruts. Antiquity 8:339–342 Farres P (2019) Palaeosoils: legacies of past landscapes, with a series of contrasting examples from Malta. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Switzerland, pp 141–152 Fenton EG (1918) The maltese cart-ruts. Man 18:67–72 Forsskål P (1951) Resa till lycklige: petrus forsskals dagbok 1761– 1763. Svenska Linné Sällskape, Uppsala, 209p Gracie HS (1954) The ancient cart-tracks of Malta. Antiquity 28:91–98 Grove AT, Rackham O (2002) The nature of mediterranean Europe. An ecological history. Yale University Press, New Haven and London, 384p Hughes KJ (1999) Persistent features from a palaeo-landscape: the ancient tracks of the Maltese Islands. Geogr J 165(1):62–78 Magro Conti J, Saliba PC (eds) (2005) The Significance of cart-ruts in ancient landscapes. Midsea Books, Valletta, 408p Marriner N, Gambin T, Djmali M, Morhange C, Spiteri M (2012) Geoarchaeology of the Burmarrad ria and early Holocene human impacts in western Malta. Palaeogeogr Palaeoclimatol Palaeoecol 339–341:52–65 Mottershead D, Pearson A, Schaefer M (2008) The cart-ruts of Malta: an applied geomorphology approach. Antiquity 82(318):1065–1079 Mottershead DN, Farres PJ, Pearson A (2010) The changing Maltese soil environment: evidence from the ancient cart-tracks at San Pawl tat-Tarġa, Naxxar. In: Smith BJ, Gomez-Heras M, Viles HA, Cassar J (eds) Limestone in the built environment: Present-day challenges for the preservation of the past, vol 331, Geological Society of London Special Publications, pp 219–229 Parker R, Rubinstein M (1984) The cart-ruts on Malta and Gozo. Gozo Press, Malta Sadori L, Narcisi B (2001) The postglacial record of environmental history from Lago di Pergusa (Sicily). Holocene 11:655–671 Salto D (2004) Use of cart ruts. The Times of Malta 22/08/2004. Available at: http://www.timesofmalta.com/articles/view/20040822/ letters/use-of-cart-ruts.114537. Last Accessed 27/03/2019 Schneider G (2001) Investigating historical traffic routes and cart-ruts in Switzerland, Elsass (France) and Aosta Valley (Italy). Oracle J Grupp Arkeologiku Malti 2:12–22 Scerri S (2019) Sedimentary evolution and resultant geological landscapes. In: Gauci R, Schembri JA (eds) Landscapes and Landforms of the Maltese Islands. Springer, Cham, pp 31–47 Trump DH (1993) Malta: an archaeological guide. Progress Press, Valletta, 191p Trump DH (2000) Malta prehistory and temples. Midsea Books, Santa Venera, 319p Velušček A (ed) (2009) Stare Gmajne pile-dwelling settlement and its era. Ljubljana, Založba ZRC, 330p Ventura F, Tanti T (1994) The cart tracks at San Pawl tat-Tarġa. Naxxar. Melita Historica 11(3):219–240 Zammit T (1928) Prehistoric cart-tracks in Malta. Antiquity 2(5):18–25

Malta’s Submerged Landscapes and Landforms

10

Mariacristina Prampolini, Federica Foglini, Aaron Micallef, Mauro Soldati, and Marco Taviani

Abstract

The application of acoustic techniques, such as multibeam echosounders, has permitted the identification of Maltese submarine landscapes and landforms that were progressively inundated during the postglacial sea-level rise. Remarkably, geomorphological features due to fluvial, gravity-induced and karst processes that took place under former subaerial conditions can be clearly recognised on the present seafloor around the Maltese archipelago, and they were only slightly modified by sea action during the postglacial transgression phases. The analysis of the submerged landforms described in this chapter is crucial for understanding the evolution of the Maltese Islands during the last ca. 20,000 years.




Keywords




Seafloor Submerged landforms Palaeogeography Malta




Sea-level rise




M. Prampolini (&)
F. Foglini
M. Taviani CNR-ISMAR Bologna, Via Gobetti 101, 40129 Bologna, Italy e-mail: [email protected] F. Foglini e-mail: [email protected] A. Micallef Department of Geosciences, University of Malta, Tal-Qroqq, Msida, MSD 2080, Malta e-mail: [email protected] M. Soldati Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 103, 41125 Modena, Italy e-mail: [email protected] M. Taviani Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Napoli, Italy

10.1

Introduction

During the last glacial cycle, sea levels were substantially lower than at present (Siddall et al. 2003). When sea-level fell by ca. 130 m at the peak of the Last Glacial Maximum (LGM, ca. 20,000 years ago), the European terrestrial landmass was ca. 40% larger by area and shaped by a range of subaerial and coastal geomorphic processes. Most of this terrestrial landscape is now submerged, having been drowned by the rapid rise in sea level that accompanied deglaciation. Recent advances in seafloor mapping technologies have allowed scientists to reconstruct submerged palaeo-landscapes in detail (Bailey and Flemming 2008; Chu and McDonough 2014). Well-preserved and diverse-submerged palaeo-landforms have recently been documented in the Maltese offshore zone (Micallef et al. 2013; Foglini et al. 2016; Prampolini et al. 2017). Here, a combination of a semi-arid climate, prevalent carbonate lithology (Baldassini and Di Stefano 2017), neotectonic stability (Pedley 2011), limited terrigenous supply (Emelyanov and Shimkus 1986), and a limited tidal amplitude (*12 cm: Drago 1997), have ensured that 450 km2 of submerged palaeo-landscapes (equivalent to 1.5 times the present Maltese terrestrial area) have been little modified by the postglacial marine transgression. Like their counterparts presently observable on-land, these now-submerged palaeo-landscapes have been shaped by fluvial, coastal, gravity-induced and karst processes, with type of lithology and tectonics exerting a dominant control. Their evolution has been regulated by climatic and sea-level oscillations. Submerged palaeo-landscapes constitute valuable geological archives of Quaternary environmental change, and they potentially provide evidence of archaeological and palaeontological interest. The aim of this chapter is to provide an overview of these poorly known yet important seascapes surrounding the Maltese archipelago.

Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, MA 02543, USA e-mail: [email protected] © Springer Nature Switzerland AG 2019 R. Gauci and J. A. Schembri (eds.), Landscapes and Landforms of the Maltese Islands, World Geomorphological Landscapes, https://doi.org/10.1007/978-3-030-15456-1_10

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10.2

M. Prampolini et al.

Geotectonic Setting

The Maltese Islands comprise one of the few emergent parts of the Pelagian Platform, which forms part of the African Plate. It represents the foreland of the Sicilian sector of the Neogene Apennine-Maghrebian fold-and-thrust belt, the front of which can be followed offshore in the northern part of the Sicily Channel in association with a complex fore-deep system (e.g. the Gela Nappe) (Fig. 10.1a). The Maltese Islands are located in the south-western part of the Malta Plateau, an asymmetric, north– Fig. 10.1 a Tectonic setting of the Maltese archipelago (indicated by the red arrow). b Palaeogeography of the Sicily Channel during the Last Glacial Maximum (LGM)

south striking carbonate ridge located between Sicily and the archipelago. To the east, the Plateau is bordered by the Malta Escarpment, which trends NNW-SSE and extends 250 km from the south-eastern coast of Sicily towards the African coast and has a vertical relief of 3 km (Micallef et al. 2019). This lineament is an expression of a passive continental margin linking the Malta Plateau to the west with the deep Ionian basin to the east. The structural setting of the Maltese archipelago is related to the tectonic evolution of the Sicily Channel Rift Zone, a complex array of elongated, fault-controlled rift basins of

10

Malta’s Submerged Landscapes and Landforms

Miocene-to-Pliocene age (Reuther and Eisbacher 1985— Fig. 10.1a). The geology of Malta is characterised by sub-horizontal tertiary carbonate successions deposited in shallow marine environments (Scerri 2019, Chap. 4) and intersected by high-angle fault systems (Gauci and Scerri 2019, Chap. 5). From oldest to youngest, the formations are: the Lower Coralline Limestone Formation (Chattian); the Globigerina Limestone Formation (Aquitanian–Lower Langhian); the Blue Clay Formation (Upper Langhian–Lower Tortonian) and the Upper Coralline Limestone Formation (Upper Tortonian–Lower Messinian). The archipelago lies on the north-eastern margin of the Malta Graben (or trough), the formation of which coincides with the late Tortonian (Baldassini and Di Stefano 2017). At that time, the Maltese archipelago underwent an uplift that is responsible for the tilting of the whole succession by 4° towards NE. The sedimentary sequence of Malta is intersected by two fault systems, which have distinct influence on the geomorphology of the islands. The ENE-WSW-oriented system is the older (early Miocene), and its major lineament is the Great Fault with a vertical displacement of 195 m (Gauci and Scerri 2019, Chap. 5). It divides the archipelago in a horst and graben structure both at a small scale (i.e. South Malta Horst, North Malta Graben and Gozo Horst; Putz-Perrier and Sanderson 2010) and at a large scale (i.e. the northern area of Malta; Alexander 1988). The more recent fault system is NW-SE oriented and parallel to the Sicily Channel Rift Zone (Galea 2019, Chap. 3). It developed during the late Miocene and early Pliocene and controls the trend of the southern and

Fig. 10.2 Schematic illustration of multibeam echosounder data acquisition. Source Image provided and copyrighted by NIWA

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north-eastern coasts of the archipelago. The Magħlaq Fault is the major expression of this system, has a vertical displacement of 210 m and is located along the southern coast of Malta (Gauci and Scerri 2019, Chap. 5). The archipelago emerged during the early Messinian (ca. 6 Ma ago) and since then subaerial geomorphological processes have modelled the landscape in various ways according to changing climatic conditions and sea-level variations. Recent studies have defined the structural features that have influenced the landscape (Micallef et al. 2013) as well as local and regional sea-level changes for the last 125 ka (Siddall et al. 2003; Lambeck et al. 2011; Marriner et al. 2012; Furlani et al. 2013). The sea level reached a minimum of 130 m below its present level 20 ka ago during the LGM (Fig. 10.1b). As a consequence, the Maltese archipelago was connected to Sicily via a land bridge that was 38 km wide and 105 km long, and which allowed the migration of megafauna from Europe towards Malta (Furlani et al. 2013; Foglini et al. 2016). As a result, seafloors down to 130 m depth emerged and were influenced by subaerial processes during the last glaciation.

10.3

Exploration of Submerged Landscapes

Geophysical methods are required to investigate the seafloor surface in detail. In marine environments, acoustic methods are preferred to electromagnetic methods, which are traditionally used in subaerial remote sensing, because acoustic signals are less attenuated by the water column, especially at low frequencies.

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The devices used to acquire seafloor topographic data are multibeam bathymetric echosounders and interferometric echosounders (Fig. 10.2). The Multibeam echosounders are active sonars that comprise transmitting and receiving transducers. They send several beams of acoustic pulses towards the seafloor and calculate the time necessary for the reflected wave to return to the receiving transducers. The interferometric echosounders differ from the multibeam because they send a unique and very wide acoustic swath towards the seafloor. Generally, interferometric echosounders are preferred to multibeam echosounders to investigate shallow or very shallow water. For both techniques, time is converted to depth according to the sound velocity profile of the water column. Echosounders are integrated into both a differential GPS system for accurate positioning and a Motion Reference Unit (MRU) to correct the data for the movements of the vessel. Backscatter data of the seabed are acquired simultaneously with bathymetric data. Backscatter is the intensity of the reflected acoustic pulse, which gives information on the composition of the type of sediments covering the seafloor: high backscatter intensity is generally correlated with the presence of coarse sediments or rocky outcrops, while low backscatter intensity is linked to the presence of fine sediments. Seafloor mapping around the Maltese Islands was started by British Admiralty in mid-nineteenth century, initially through the use of traditional methods such as sounding weights, as part of intensive hydrographic surveys in central Mediterranean. The use of Malta as a British military base ensured that the area around the islands was continually surveyed by Royal Navy British hydrographers such as by Captains Smyth, Graves and Spratt during the middle and latter half of the nineteenth century. Their work pioneered Admiralty charts of the Mediterranean Sea. In 1957-58, the traditional method of seafloor surveying was replaced with that of single-beam echosounder. Nautical charts for the archipelago were generated using these data and were subsequently updated through a number of localised single-beam echosounder surveys. The most recent nautical chart of the seafloors surrounding the Maltese Islands was published by Admiral Haslam in 1983 at a scale of 1:50,000. In the last five years, extensive areas of seafloor, offshore of eastern Maltese Islands (from north Gozo to south-east Malta) and the western side of Maltese Islands (from Marfa Ridge to the north and Ras Il-Pellegrin to the south), have been mapped at high-resolution using both multibeam and interferometric echosounders (Micallef et al. 2013; Foglini et al. 2016).

M. Prampolini et al.

10.4

Submerged Landscapes and Landforms

Sea-level changes have greatly influenced the Maltese landscapes, especially the areas closest to the present coastline. The latter have experienced several fluctuations of the sea level and have been affected by coastal processes. In particular, the areas shallower than −130 m emerged during sea-level lowstands and were also affected by subaerial processes. Because of sea-level rise in the last 20,000 years, these features were ‘hidden’, although they are still easily recognisable in geophysical data because they were not significantly modified by marine transgression. The combination of alternating subaerial and submarine processes with tectonic processes has given rise to diverse seafloor landforms that are significantly different on the eastern and western seafloors of Malta (Fig. 10.3).

10.4.1 The ‘gentle’ Landscape off the Eastern Coasts The Maltese seafloor on the eastern side of the archipelago comprises an almost flat continental shelf that extends for 1.5 km from the present shoreline offshore north-eastern Gozo, and extends up to 10 km from St. Paul’s Bay in Malta. From this point southwards, the shelf turns landward close to St. Julian’s Bay. The sedimentary cover of the shelf is heterogeneous and varies from medium to fine sand offshore the eastern coast of Gozo and Comino to an alternation of sand, gravel and outcrops of bedrock off the eastern coast of Malta (Micallef et al. 2013; Foglini et al. 2016; Prampolini et al. 2017, 2018). The continental shelf is bounded offshore by a shelf break, varying in depth between a minimum of 50 m (area north-east of Gozo) to a maximum of 95 m (north-east of Malta). It is the upper limit of an escarpment sloping 35° and linking the continental shelf with a basin mostly covered by fine sand. The escarpment runs from the north-eastern area off the shore of Gozo to St. Paul’s Bay (Malta)—where its base is located at a depth of 130 m, and from St. Paul’s Bay to St. Julian’s Bay Malta), where the base of the escarpment reaches a maximum depth of 126 m. Along with its length, the shelf is dissected by numerous channels that follow the trend (SW-NE and SSW-NNE) of the terrestrial river valleys (‘wied’ in Maltese; plur. ‘widien’). Occasionally in the upper part of the submerged portion of the channels, there are areas characterised by a relatively smooth seabed, which is currently covered by fine sediment ripples (Angeletti et al. 2012; Micallef et al. 2013; Prampolini et al. 2017). In Fig. 10.4, an example from the channel located off the shore of the island of Comino is provided: it is about 3.4 km long and its bed shows

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Malta’s Submerged Landscapes and Landforms

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Fig. 10.3 Palaeogeography and main geomorphological features of Malta during the LGM. The quadrats indicate the location of the features shown in the following figures. Source DEM map from ERDF LIDAR data (2012)

variations in sediment coverage. Some of these submarine channels represent a prolongation of present terrestrial ‘wied’, and it is likely that the entire network of incised valleys and related alluvial plains originated when the continental shelf emerged during the past sea-level lowstands. A spectacular example of ria coastline is located in the area of Valletta, specifically the two inlets that surround the capital city (i.e. the Grand Harbour and the Marsamxett Harbour) (Schembri and Spiteri 2019, Chap. 6). The former corresponds to the most important harbour of the archipelago and is bounded by the city of Valletta to the northwest and by the headlands of Senglea, Cospicua and Vittoriosa to the southeast. A number of fluvial valleys, with a large catchment area on land, converge in the Grand Harbour. The second inlet is located on the western side of Valletta where two ‘widien’ converge into the Marsamxett Harbour. These two inlets represent drowned valley mouths and here the seafloor reaches a depth of up to 25 m at its centre. Offshore of the two harbours, the seabed is intensely disturbed because of various human activities, such as bottom trawling, dredging, and dumping construction spoil. Traces of these activities are observable in the acoustic backscatter data as scattered

circular mounds with high reflectivity in a flat seabed covered by fine sediment (Fig. 10.5b) and the areas dedicated to these works are identified in the bathymetric chart compiled by Admiral Haslam in 1983 (Fig. 10.5a). In offshore areas from St. Paul’s Bay to Marsaskala, marine terraces and ridges characterise the seafloor at depths ranging from 30 to 130 m (Fig. 10.6a). Eight levels of marine terraces were recognised and interpreted as palaeo-shore platforms (see also Micallef et al. 2013), like those now observable along the stretch of Selmun coast facing St. Paul’s Island (Sammut et al. 2019, Chap. 26) and in correspondence to Qawra Point (Fig. 10.6b; Biolchi et al. 2016). The ridges, located mainly offshore the Grand Harbour, have a very gentle slope (