Periglacial Geomorphology

A FASCINATING AND INFORMATIVE EXPLORATION OF PERIGLACIAL PROCESSES, PAST AND PRESENT, AND THEIR ROLE IN LANDSCAPE EVOLUTION

Periglacial Geomorphology presents a comprehensive introduction to the processes that operate in present periglacial environments and discusses the inferences that can be drawn about former periglacial environments from those processes. Organized into six parts, the book opens with the historical and scientific context of periglacial geomorphology and the nature of periglacial environments. Following chapters provide systematic coverage of the full range of topics germane to a thorough understanding of periglacial geomorphology, including:

• The physics of ground freezing and thawing, characteristics of permafrost, and the nature and origin of underground ice
• Characteristics, formation and significance of landforms, sediments, and structures associated with permafrost, permafrost degradation, and seasonal ground freezing and thawing
• Rock weathering in periglacial environments, periglacial processes operating on hillslopes, and the characteristic landforms produced by rock breakdown and slope processes in cold environments
• The operation of fluvial, aeolian and coastal processes in cold environments, and the resulting distinctive landforms and sediments
• The use of relict periglacial features to reconstruct past cold environments in midlatitude regions and the responses of periglacial environments to recent and predicted climate change

Periglacial Geomorphology is an important resource for undergraduate and graduate students studying geomorphology or Quaternary science within the context of geography and geology degree programs. It will be of use to all scientists whose research involves an understanding of cold environments, whether from a geographical, geological, ecological, climatological, pedological, hydrological, or engineering perspective.

Preface xi

Acknowledgement xiii

1 Introduction 1

1.1 The Periglacial Concept: Definitions and Scope 1

1.2 The Periglacial Realm 5

1.3 The Development of Periglacial Geomorphology 5

1.4 Periglacial Geomorphology: The Quaternary Context 7

2 Periglacial Environments 11

2.1 Introduction 11

2.2 Periglacial Climates 11

2.3 Soils in Periglacial Environments 17

2.4 Vegetation Cover in Periglacial Environments 18

2.5 Synthesis 20

3 Ground Freezing and Thawing 23

3.1 Introduction 23

3.2 Ground Heating and Cooling 23

3.3 Soil Freezing 28

3.4 Ice Segregation in Freezing Soils 32

3.5 Thaw Consolidation 37

3.6 Synthesis 38

4 Permafrost 39

4.1 Introduction 39

4.2 Permafrost Thermal Regime 40

4.3 Classification of Permafrost 43

4.4 Detection, Mapping and Modelling of Permafrost 44

4.5 Permafrost Distribution 46

4.6 Permafrost–glacier Interactions 53

4.7 The Geomorphic Importance of Permafrost 54

5 Ground Ice and Cryostratigraphy 57

5.1 Introduction 57

5.2 Genetic Classification of Ground Ice 57

5.3 Description of Ground Ice 62

5.4 Ice Contacts 66

5.5 Cryostratigraphy 67

5.6 The Transition Zone 69

5.7 Massive Ground Ice 72

5.8 Yedoma 76

6 Thermal Contraction Cracking: Ice Wedges and Related Landforms 81

6.1 Introduction 81

6.2 Thermal Contraction Cracking and Polygon Evolution 81

6.3 Ice Veins and Ice Wedges 84

6.4 Ice]wedge Polygons 87

6.5 Sand Veins and Sand Wedges 89

6.6 Composite Veins and Composite Wedges 90

6.7 Sand]wedge Polygons 90

6.8 Frost Cracking of Seasonally Frozen Ground 91

6.9 Thaw Modification of Frost Wedges 91

6.10 Frost]Wedge Pseudomorphs and Frost Polygons in Areas of Past Permafrost 92

7 Pingos, Palsas and other Frost Mounds 97

7.1 Introduction 97

7.2 Characteristics of Pingos 97

7.3 Hydrostatic Pingos 99

7.4 Hydraulic Pingos 101

7.5 Pingo Problems and Problem Pingos 104

7.6 Segregation Ice Mounds: Palsas, Lithalsas and Related Landforms 105

7.7 Palsas 106

7.8 Peat Plateaus 109

7.9 Lithalsas 109

7.10 Permafrost Plateaus 111

7.11 Other Permafrost Mounds 111

7.12 Ephemeral Frost Mounds 112

7.13 Relict Permafrost Mounds 113

8 Thermokarst 117

8.1 Introduction 117

8.2 Thermokarst Lakes and Drained Lake Basins 118

8.3 Thermokarst Pits, Bogs and Fens 131

8.4 Retrogressive Thaw Slumps 132

8.5 Small]scale Thermokarst Features: Beaded Streams, Sinkholes and Thermokarst Gullies 136

8.6 Sediment Structures associated with Thermokarst 138

8.7 Relict Thermokarst Phenomena 139

9 Seasonally Frozen Ground Phenomena 143

9.1 Introduction 143

9.2 Upfreezing of Clasts 143

9.3 Frost Heave of Bedrock 145

9.4 Patterned Ground: The Embroidery on the Landscape 145

9.5 Patterned Ground Processes 147

9.6 Sorted Patterned Ground 148

9.7 Nonsorted Patterned Ground 155

9.8 Cryoturbations 161

9.9 Pedogenic Effects of Freezing and Thawing 164

9.10 Fragipans 166

9.11 Synthesis 167

10 Rock Weathering and Associated Landforms 169

10.1 Introduction 169

10.2 Physical Weathering Processes 169

10.3 Chemical Weathering Processes 177

10.4 Biotic Weathering Processes 180

10.5 Weathering Processes in Periglacial Environments 180

10.6 Cold]climate Karst 181

10.7 Tors 182

10.8 Blockfields and Related Periglacial Regolith Covers 185

10.9 Brecciated Bedrocks 192

11 Periglacial Mass Movement and Hillslope Evolution 195

11.1 Introduction 195

11.2 Solifluction Processes 195

11.3 Solifluction Landforms 204

11.4 Pleistocene Solifluction Landforms and Slope Deposits 210

11.5 Active]layer Failures 213

11.6 Permafrost Creep 215

11.7 Nivation 217

11.8 Cryoplanation 220

11.9 Slope Form and Slope Evolution 222

12 Talus Slopes and Related Landforms 225

12.1 Introduction 225

12.2 Rockfall Talus 225

12.3 The Geomorphic Role of Snow Avalanches 234

12.4 Debris]flow Activity 237

12.5 Rock Glaciers 240

12.6 Pronival (Protalus) Ramparts 248

12.7 Synthesis 250

13 Fluvial Processes and Landforms 253

13.1 Introduction 253

13.2 Periglacial Hydrology 253

13.3 Slopewash 259

13.4 Slushflows 261

13.5 Sediment Transport in Periglacial Rivers 261

13.6 Bank and Channel Erosion 263

13.7 River Channels 266

13.8 Alluvial Landforms in Periglacial Environments 268

13.9 Valley Form 270

13.10 Pleistocene Periglacial Rivers 271

13.11 Synthesis 273

14 Wind Action 275

14.1 Introduction 275

14.2 Aeolian Processes 275

14.3 Wind Erosion in Present Periglacial Environments 276

14.4 Aeolian Deposits in Present Periglacial Environments 279

14.5 Quaternary Aeolian Deposits 288

14.6 Synthesis 297

15 Periglacial Coasts 299

15.1 Introduction 299

15.2 The Nature of Periglacial Coasts 299

15.3 The Role of Ice in Shoreline Evolution 301

15.4 Ice]rich Permafrost Coasts 303

15.5 Thermokarst Coasts 305

15.6 Barrier Coasts 306

15.7 Salt Marshes and Tidal Flats 308

15.8 Rock Coasts 308

15.9 Raised and Inherited Shorelines 309

15.10 Lake Shorelines 310

15.11 Synthesis 311

16 Past Periglacial Environments 313

16.1 Introduction 313

16.2 Palaeoenvironmental Reconstruction Based on Periglacial Features 314

16.3 Past Periglacial Environments of the British Isles 322

16.4 Pre]Late Devensian Periglacial Features in the British Isles 323

16.5 The Dimlington Stade in the British Isles 325

16.6 The Younger Dryas (Loch Lomond) Stade in the British Isles 329

16.7 Past Periglacial Environments of the British Isles: Commentary 332

16.8 Late Weichselian Periglacial Environments in Continental Europe 332

16.9 Late Wisconsinan Periglacial Environments in North America 341

16.10 Permafrost Extent in the Northern Hemisphere During the Last Glacial Stage 344

16.11 Concluding Comments 346

17 Climate Change and Periglacial Environments 349

17.1 Introduction 349

17.2 Permafrost Degradation 352

17.3 Geomorphological Implications of Climate Change in the Circumpolar North 356

17.4 Geomorphological Implications of Climate Change in High Mountain Environments 363

17.5 Climate Change, Permafrost Degradation and Greenhouse Gas Emissions 369

17.6 Conclusion 371

Appendix: Text Abbreviations, Units and Symbols Employed in Equations 373

References 375

Index 441

COLIN K. BALLANTYNE, PhD DSC FRSE FRSGS FGS FBSG is Emeritus Professor in Physical Geography, University of St Andrews, St. Andrews, Fife, Scotland, UK.