xi xi
8 Mass Wasting: The Work
of Gravity 196
Landslides as Natural Disasters 198
Mass Wasting and Landform Development 199
The Role of Mass Wasting 199
Slopes Change through Time 200
• Controls and Triggers of Mass Wasting 200
The Role of Water 201
Oversteepened Slopes 201
Removal of Vegetation 202
Earthquakes as Triggers 202
Case Study: Landslide Hazards at La Conchita,
California 204
Landslides without Triggers? 204
The Potential for Landslides 205
Classification of Mass-Wasting Processes 205
Type of Material 205
Type of Motion 205
Rate of Movement 206
• Slump 207
• Rockslide 208
• Debris Flow 209
Debris Flows in Semiarid Regions 209
Lahars 209
• Earthflow 210
• Slow Movements 211
Creep 211
Solifluction 211
The Sensitive Permafrost Landscape 211
THE CHAPTER IN REVIEW 213 KEY TERMS 213
GIVE IT SOME THOUGHT 213 COMPANION
WEBSITE 213
9 Running Water 214
• Earth as a System: The Hydrologic Cycle 216
• Running Water 218
Drainage Basins 218
River Systems 218
• Streamflow 219
Flow Velocity 220
Gradient and Channel Characteristics 220
Discharge 221
Changes Downstream 221
The Work of Running Water 222
Stream Erosion 222
Transport of Sediment by Streams 223
Deposition of Sediment by Streams 224
Stream Channels 224
Bedrock Channels 225
Alluvial Channels 225
Base Level and Graded Streams 227
• Shaping Stream Valleys 228
Valley Deepening 228
Valley Widening 228
Incised Meanders and Stream Terraces 229
Depositional Landforms 230
Deltas 230
The Mississippi Delta 230
Natural Levees 231
Alluvial Fans 231
• Drainage Patterns 232
Floods and Flood Control 233
Types of Floods 233
Flood Control 234
THE CHAPTER IN REVIEW 236 KEY TERMS 236
GIVE IT SOME THOUGHT 236 COMPANION
WEBSITE 237