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BK

London : Longman, 1976

ISBN 0-582-48079-5

At several times during the last one million years cold non-glacial conditions have prevailed over large areas of middle latitudes. Many students will never have the opportunity to experience present day high latitude periglacial environments, but the appreciation of such conditions is nevertheless essential for a balanced interpretation of the more familiar middle latitudeJandscapes. This book therefore appraises the nature of geomorphic processes and land forms in high latitude periglacial environments and provides a guide to the recognition and interpretation of periglacial features in the now temperate regions of North America and Europe. Beginning with a general introduction to periglacial conditions, Dr French considers the extent of the periglacial domaine and the variety of periglacial climates. He then presents a systematic treatment of the various geomorphic processes operating in contemporary periglacial environments. This is followed by an introduction to Pleistocene periglacial phenomena, laying emphasis on forms rather than processes and their interpretation in the light of our understanding of similar phenomena in contemporary periglacial environments. The Pleistocene periglacial conditions of Southern England, the Western European coastal lowlands and interior Eastern Europe are dealt with in some detail. This book has been written for university students, particularly at second year level, and assumes a certain knowledge of introductory geomorphology. It will also be a useful introduction to more detailed reading at an advanced level..

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Rekat.

Preface ix // Part 1 The periglacial domaine // 1 Introduction 2 // The periglacial concept 2 Periglacial processes 3 // 2 Periglacial climates 5 // Boundary conditions 5 Periglacial climates 5 High Arctic climates 8 Continental climates 9 Alpine climates 9 // Climates of low annual temperature range 10 // Part 2 Present-day periglacial environments // 3 Frost action 12 // The significance of frost action 12 The freezing process 12 Freezing and thawing indices 13 The freezing and thawing regime of the soil 13 The long-term temperature cycle 14 Short-term temperature cycles 17 Frost-action processes 19 Thermal contraction cracking 21 Frost cracks filled with ice 21 Frost cracks filled with sand 23 Soil wedges 25 Ice segregation processes 27 Frost heaving 28 Upfreezing of objects 30 Stone tilting 32 Needle ice 33 Frost mounds 33 Frost sorting 35 // Volumetric increase in water as it freezes 37 Frost wedging 37 // Mass displacements and cryostatic pressures // 4 Permafrost 45 // Historical perspective 45 Geothermal regime of permafrost 47 Distribution of permafrost 50 Canada and Alaska 51 The USSR 53 Offshore permafrost 57 Relic permafrost 58 // Permafrost and terrain conditions 59 // Surface features of permafrost and air photo interpretation 62 Hydrologic aspects of permafrost 65 Groundwater supply 65 // Groundwater, artesian pressures and open system pingos 67 Icings 68 // Engineering aspects of permafrost and frost action 69 // 5 Ground ice 75 // Ground ice description 75 Types of ground ice 77 Massive ice and massive icy bodies 80 Nature and extent 80 Origins of massive ice 81 Ice-cored topography 82 Involuted hills 83 Ice-cored terrain 83 Ice wedges 84 Origin 85 // The development of the polygonal net 87 Climatic and palaeogeographic significance 91 Pingos and other ice-cored mounds 93 Open system pingos 95 Closed system pingos 98 Pingo-Iike features 100

Hydrolaccoliths and frost mounds 101 // 6 Thermokarst 105 // Causes of thermokarst 106 // Thermokarst subsidence and thermal erosion 110 // Thermokarst subsidence 111 // The alas thermokarst relief of central Yakutia 111 Alas relief in North America 115 Ice-wedge thermokarst relief 116 Backwearing thermokarst 119 Ground ice slumps 119 Thaw lakes and depressions 122 Fluvio-thermal erosion processes 125 Man-induced thermokarst development 128 // 7 Hillslope forms and processes 134 // Mass wasting processes 134 Solifluction 135 Slopewash 141 Solution 143 Nivation 144 Rapid mass movement 145 Periglacial slope forms 149 // The free face and debris slope profile 150 // Smooth debris mantled slopes 152 Cryopediment forms 155 // Cryoplanation terraces and stepped profiles 157 Slope evolution 161 Cryoplanation 162 Slope replacement 164 The rapidity of profile change 165 General conclusions on hillslope forms and processes 166 // 8 Fluvial processes and landforms 167 // Fluvial processes 167 // Hydrology and summer weather 168 Sediment movement 171 Thermal erosion 173 Channel forms 174 Periglacial valley sandar 176 Valley forms and slope asymmetry 178 // 9 Micro-relief features 184 // Patterned ground 184 Description 184 Origins 189 Soils 196 // The Northern Forest Zone 197 The Main Tundra Zone 197 The Polar Desert Zone 199 // 10 Wind action and coastal processes 202 // The role of wind 202 Wind erosion 203 Wind deflation 204 Coastal processes 206 // Sea ice and wave generation 207 // The effects of ice on the beach 208 // The influence of permafrost and ground ice 211 // Part 3 Pleistocene periglacial environments // 11 Pleistocene periglacial conditions 214 // Introduction 214 // The time scale and climatic fluctuations 214 // Geomorphic considerations 218 // Problems of reconstruction 221 // Extent of Late Pleistocene periglacial conditions 222 //

12 Relic periglacial phenomena 227 // Evidence for frost-action conditions 227 Frost-disturbed soils and structures 227 // Blockfields and frost weathered bedrock 229 Tors 231 // Stratified slope deposits and grezes litées 234 ’Head’ and solifluction deposits 235 Evidence for permafrost conditions 236 Ice- and sand-wedge casts 236 Pingo remnants and related forms 245 Thermokarst forms 248 Evidence for Pleistocene wind action 249 Asymmetrical valleys 253 // 13 Periglacial landscape modification 257 // The Chalk landscapes of southern England 257 Periglacial deposits 257 Landform modification 260 // Asymmetrical valley development 260 The ’rock-streams’ of Wiltshire and Dorset 262 Patterned ground features of the East Anglian Chalk Periglacial valleys and dells 266 The periglacial legacy in southern England 268 The landscape of central Poland 269 The dry valleys of the Lodž plateau 271 Gora Sw Malgorzata 272 Walewice 275 Summary 277 // References 278 // Index 303