Table of Contents
List of Figures xi
Acknowledgements xv
Introduction 1
Part One <10 m2; <10 years 5
1 Wind and Sand 7
Wind versus Bed 7
The Law of the Wall 8
Improving the wind/bed model 9
Lift-Off 12
Holding down by gravity 12
Holding down by cohesion 12
Raising by lift 13
Raising by drag 13
Raising by bombardment 14
Thresholds 14
Grain size 16
The slope of the bed 17
The dynamics of water content 17
Crusts 19
Pellets 20
Sand in Motion 20
Saltation 20
Streamers and other medium-scale patterns of saltating sand 22Reptation 22
Creep 23
Other near-surface activity 23
Suspension 24
The vertical distribution of load and grain size 24
The saturation length 24
The fetch effect 26
The response of a loose bed to erosion by the wind 27
The Transport Rate 27
Shapes, densities and mixtures of size 29
Hard surfaces 30
Rough surfaces 30
Moisture, temperature and humidity 31
Rain 31
References 31
2 Ripples 32
Subtypes 35
Models 36
Flow response 36
Gravity wave 36
Saltation length 37
Shadow zone 37
Mathematical 37
Pattern 38
3 The Form and Behaviour of Free Dunes 39
Definitions 39
Early Stages 39
Start 39
Minimum size 40
The Profile of a Fully Grown Dune 41
Toe 41
Windward slope (or ‘stoss slope’) 43
Crest 45
Lee slope 46
Movement 53
Turnover time, bulk transport 56
Size 56
Flow-hierarchy models 57
Grain-size models 57
The time/supply model 58
References 58
Part Two 1000 to 10,000 m2; 100 to 1000 years 59
4 Pattern in Free Dunes 61
Definitions 61
Wind-Directional Regimes 62
Global winds 62
Local wind systems 62
The Classification of Wind-Directional Regimes 65
Wind-Directional Regimes and Dune Pattern 66
Transverse Dunes 66
Two-dimensional pattern: vertical and downwind 67
Two-dimensional pattern: horizontal and transverse to the wind 68
Self-organisation 69
Barchans 71
Quasi-transverse patterns 75
Linear Dunes 80
Introduction 80
Models of formation 82
Sand Sheets 88
Dunes with Distinctive Sand 90
Gravel dunes 90
Zibars 91
Clay dunes 92
Lunettes 92
Gypsum dunes 93
Diatomite sands 93
Volcanic sands 93
Snow and ice dunes 94
Niveo-aeolian deposits 94
References 94
5 Forced Dunes 96
Dunes Built around Bluff Obstacles 96
Climbing and echo dunes 96
Flanking and lee dunes 97
Cliff-top and falling dunes 99
Dunes on Gently Sloping Terrain 99
Reference 99
6 Dunes and Plants 100
Wind, Sand and Plants 100
Rigid objects 100
Spatial pattern 101
Porosity 102
Flexibility 102
Plants as living things 103
The broader time/space framework 104
Dunes among Plants 104
Nebkhas 104
Blowouts 107
Parabolic dunes 109
References 111
7 Coastal Dunes 112
Coastal Dunes and Climate 112
The Beach–Dune System 114
Exclusively Coastal Dunes 117
Embryo dunes 117
Fore-dunes (‘frontal dunes’ or ‘retention ridges’) 118
Tsunamis 120
Coastal sand sheets 120
References 121
Part Three >0.3 mm; <2,200,000,000 years 123
8 Sand Seas 125
Terms 125
Large Sand Seas 127
Growth and Development 127
Sand Seas in Tectonic Basins 129
Topographically Unconfined Sand Seas 131
Transfer between Sand Seas 133
9 A History of Dune Sand 134
Provenance 134
Recycling 137
Maturation 139
Mineralogy 139
Size characteristics 141
Shape and surface texture 141
Redness 144
Relationships between Dune Fields and the Sources of Their Sand 145
Source-bordering dune fields 145
Dune fields that have migrated away from their source 145
Sand seas that have taken sand from many local sources 146
The Australian sand seas and some aeolian sandstones 146
References 146
10 A History of Inland Dunes 147
Very Ancient Dunes: Siliceous Windblown Sandstones 147
The Emergence of Familiar Spatial and Dynamic Patterns 151
Dune Historiography 153
Dating 153
Dune-building environments 156
The long-term development of sand seas: sediment state 160
Quaternary Dune-Building Climates 160
Dunes in the Early- and Mid-Pleistocene 162
Late Pleistocene Dunes 163
The main theatres of dune formation in the Late Pleistocene 165
Dunes in the Holocene 175
The deglaciated North 176
The mid-latitudes 177
The semi-arid tropics 178
The present deserts 178
References 179
11 A History of Coastal Dunes 181
Long Sequences 181
Sea Level 181
Other Controls 182
Calcareous Aeolianite 184
Reference 185
12 Mars, Venus, Titan 186
Similarities 186
Differences 187
Sand 188
Ripples and Transverse Aeolian Ridges 190
Dunes 191
Mars 191
Venus 194
Titan 194
Reference 195
Part Four Care 197
13 Local, Short-Term Care (<1000 m2; <10 years) 199
Dunes in Deserts 199
Folk science 199
New approaches 200
Stabilised Dunes in Semi-Arid Areas 204
Coastal Dunes 204
References 207
14 Sustainability (>100,000 m2; >10 years) 208
Constraints 208
Complexity 208
Uncertainty 210
Environmental change 210
Sustainability 211
Coastal dunes 211
Stabilised inland dunes 212
References 213
Index 214
