Hong Kong Landscapes Shaping the Barren Rock
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Hong Kong Landscapes Shaping the Barren Rock Bernie Owen and Raynor Shaw Hong Kong University Press 14/F Hing Wai Centre 7 Tin Wan Praya Road Aberdeen Hong Kong © Hong Kong University Press 2007 ISBN 978-962-209-847-3 All rights reserved. No part of this publication may be reproduced or transmitted, in any means, electronic or mechanical, including photocopy, recording, or any information storage or retrieval system, without prior permission in writing from the publisher. British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. Secure On-line Ordering http://www.hkupress.org Cover photograph: Easterly view of Lantau Peak from Por Kai Shan, Lantau Island Title page photograph: Ngong Ping Plateau, Ma On Shan Country Park Printed and bound by Colorprint Production Co. Ltd. in Hong Kong, China Table of Contents List of Information Notes......................................................................................... viii Using this Book........................................................................................................ ix Part One: Introduction Modern and Ancient Environments......................................................................... 2 Preamble 2 The Lay of the Land 2 Reconstructing the Past 5 An Environmental History...................................................................................... 7 Part Two: Landscape Types and Origins Rugged Mountain Landscapes: A Story of Ancient Volcanic Eruptions............... 13 Rounded Hilly Landscapes: The Roots of Volcanoes............................................. 21 Ridges and Colourful Landscapes: Ancient Seas, Rivers, Lakes, and Deserts....... 25 Lowlands and Valleys: Fractured Rocks and Rivers................................................ 33 Coastal Landscapes: Cliffs, Beaches, and Mud Flats.............................................. 41 The esternW Region 41 The Central egionR 43 The Eastern egionR 45 Part Three: Hong Kong Regions The Northwestern New Territories........................................................................... 48 What Lies Beneath 50 Rivers and Floodplains 54 Human Impacts 60 The ortheasternN New Territories............................................................................ 67 Landscape Foundations 68 Streams and Waterfalls 71 Marine Inlets and Islands 74 Human Impacts 77 The esternW New Territories.................................................................................... 84 Magma Chambers and Eruptions 86 High Ground, Low Ground 88 Gullies and Badlands 90 Mountain Streams 94 Human Impacts 96 vi The Central New Territories..................................................................................... 101 An Era of Violent Eruptions 104 Human Impacts 109 The outheasternS New Territories........................................................................... 119 Geological Background 121 Sea Level Change and Islands 125 Human Impacts 127 The Eastern New Territories.................................................................................... 131 Rocks and Scenery 133 Coastal Environments 137 Human Impacts 145 Lantau Island............................................................................................................ 149 Ancient Sediments, a Caldera, and Multiple Intrusions 152 Mass Movements and Landslides 158 Coastal Landscapes 160 Human Impacts 164 Expanding Infrastructure 169 Kowloon and the Lion Rock Ridge.......................................................................... 173 Geology and Weathering 175 Human Impacts 180 Hong Kong Island and Lamma................................................................................ 189 Landscape Foundations 192 Human Impacts 195 Seas and Islands........................................................................................................ 207 Marine Environments 208 Human Impacts 214 The slandsI of Hong Kong 215 Epilogue: Landscapes, Past, Present, and Future..................................................... 230 Global Warming 232 Urbanisation and Landscape 233 Information Sources and Further Reading.............................................................. 235 Part I: Publications Referred to Extensively 235 Part II: Publications Referred to Less Extensively 235 Part III: Further Reading 239 Index...................................................................................................................... 242 vii List of Information Notes 01 Geological Time and Dating 6 44 Hong Kong Corals 145 02 Extrusive Igneous Rocks 15 45 The Lantau Dyke warmS 155 03 Escarpments and Cuestas 18 46 Mass Movements 159 04 Intrusive Igneous Rocks 22 47 Tidal Flats 162 05 Beds, Bedding Planes, and Time 26 48 Current Ripples 163 06 Sedimentary Formations 29 49 Pirates and Forts 165 07 Differential Erosion 31 50 Dolphin Habitat Problems 172 08 Types of Fault 35 51 Weathered Rock Layers 177, 178 09 Joints in Rock 37 52 Urban Geological Mapping 181 10 Boulder Fields and Joints 39 53 Urban Geology 183 11 Metamorphic Rocks 51 54 World War II 187 12 Folds 52 55 Amphibians and Reptiles 206 13 Mai Po and the Wetlands 55 56 Tides 210 14 Floodplain Sediments 57 57 Seismic Profiles 213 15 Feng Shui and Landscape 83 58 W. Brother Isl. Graphite Mine 216 16 Plate Tectonics 88 59 Vietnamese Refugees 217 17 Colluvium 91 18 Granite Weathering 92 19 Base Level and Streams 95 20 Plantation Trees 98 21 Hong Kong Minerals 100 22 The NgTung Chai Waterfalls 102 23 Migrating Volcanoes 105 24 Earthquake Risks in Hong Kong 108 25 Tea Terraces 109 26 Animal Biodiversity 110 27 Reservoirs 111 28 Country Parks 112 29 Mining and Landscape Scars 114 30 The ewN Town Programme 115 31 Tai Po Kau 116 32 Scheduled Areas 118 33 The aM On Shan Iron Mine 124 34 Valley Deltas and Progradation 126 35 Chinese Graves 128 36 Landfills 129 37 Butterflies 130 38 Hong Kong Weather 132 39 Insects 134 40 Calderas and Columnar Joints 136 41 Beach Terminology 139 42 Beach Processes 141 43 Delta Sediments 143 viii Rugged Mountain Landscapes RUGGED MOUNTAIN LANDSCAPES: A STORY OF ANCIENT VOLCANIC ERUPTIONS Long-extinct volcanoes have left relatively thin, stony soils. These rugged an indelible footprint on Hong Kong’s mountainous landscapes occur widely landscape. Large parts of the territory in the New Territories, Lantau Island, were influenced by volcanic activity that southern Hong Kong Island, eastern produced relatively hard rocks. Today, Hong Kong, and throughout most of the these commonly form the foundations of Country Parks. The influence of volcanic the most prominent peaks, including Tai rocks on the shape of the land surface can Mo Shan (Big Hat Mountain), which rises also be observed along the more dramatic to 957 m and is the highest summit in Hong coastlines, with their steep cliffs and Kong. Other high points underlain by angular, rocky shorelines. volcanic rocks include: Sunset Peak, Lantau Peak, Fei Ngo Shan, Sharp Peak, and Ma On The volcanic rocks were created, not Shan (p. 12). Although tall cliffs are rare, by slow moving lava flows, but by violent there are many steep slopes, narrow ridges, eruptions that took place mostly between and scattered rocky outcrops interspersed 165–140 million years ago. Fragments with more gentle grassy and wooded areas. thrown out of these volcanoes originated Surface boulders are common, resting on from hot sticky magma that accumulated Shenzhen Mirs Bay Deep Bay Sharp Peak Tai Mo Shan Ma On Shan Fei Ngo Shan Sunset Peak Hong Kong Island Lantau Peak Reclamation Modern silt & sand Siltstone Sandstone & conglomerate Granite & related rocks Rhyolite (dykes) Tuffs Hong Kong is dominated by volcanic rocks called tuffs (IN02, p. 15) that originated as ash thrown violently out of multiple volcanoes. Today, these igneous rocks are exposed at the surface over about 50% of the territory, mainly occurring in the eastern and northern New Territories, western Lantau, and southern Hong Kong Island. 13 Rugged Mountain Landscapes Volcanic rocks in Hong Kong were Volcanic terrain Modern China coastline originally formed as a result of subduction along a plate boundary. This occurred Hong Kong when one rigid plate was forced below Shallow seas Land another and melted as it descended into the earth’s interior, where it reached areas of Deep water higher temperature. Magma was produced, Continental which then rose through the overlying rocks Rising Oceanic plate magma plate to form magma chambers below volcanoes. Hot semi-liquid material Occasionally, this material reached the surface, giving rise to violent eruptions. Melting of plate in reservoirs deep below the surface. These volcanoes were part of an extensive volcanic terrain along, what is today, the south China coastline. The eruptions took place along a linear plate boundary (figure above). In this region, the southern plate was driven northwards, melting as it descended deeper below the northern plate, producing magma. Similar plate boundaries occur today around the edges of the Pacific Ocean and are responsible for the active volcanoes in places such as the Philippines, Japan, and New Zealand. The rate of supply of the magma controls the eruption frequency. Magmas produced in these settings are rich in silica, which makes them very viscous The photograph above shows the northern slopes of Ma (sticky). Consequently, they tend to resist On Shan viewed from a northern ridge on Buffalo Hill. movement (flowing), so that eruptions The photograph below is of Sharp Peak—the dramatic are particularly