CHAPTER 18 Focus Points
18.1 Desert Landforms and Processes
Weathering: Physical weathering is more prominent than chemical weathering in deserts.
Aeolian erosion: Erosion by wind is a significant factor in desert environments.
Sand dunes: Sand dune type is determined mostly by the amount of sand available and the direction of the prevailing wind.
Fluvial erosion: Fluvial erosion is more important than aeolian erosion in deserts. Fluvial erosion occurs mostly after heavy rainfall, when the channels of ephemeral streams are filled.
Fluvial deposition: Streams deposit sediments on alluvial fans and playas.
18.2 Desert Landscapes
Desert landscapes: Landscapes found in deserts include regs, ergs, mesa-
18.3 Geographic Perspectives: Shrinking Desert Lakes
Human diversions: Water diversions by people have caused desert lakes to shrink.
Hydrologic balance: The levels of desert lakes in internal drainage basins represent a balance between water flow into the lakes and water losses by evaporation and infiltration.
Shrinking lakes: The Aral Sea and the lakes of the Great Basin are examples of desert lakes that are shrinking due to water diversions.