IX. Deserts

A. Basics

1. definition - less than 25 cm of rain each year
2. erosion-transport-deposition
1. water is more important than wind, but wind is more important in deserts than in other areas
2. weathering is slower than in other environments - mountains more jagged and rugged
3. Distribution
1. 20-30 latitude
2. distance from ocean
3. rainshadow

B. Erosion

1. water-little vegetation makes erosion easy
2. wind -
1. abrasion can play a major role and sculpt rocks
2. deflation - desert pavement

C. Transport

1. water - ephemeral streams periodically carry large sediment load due to lack of vegetation
2. Wind has low competence but high capacity - often moves sediment through saltation

D. Deposition

1. water
1. ephemeral braided streams
2. alluvial fans
3. playa lakes (interior drainage) - evaporites playa lake photo, evaporite photo1, evaporite photo2
2. wind
1. sand dunes - cross-bedding dune photo1, dune photo2, cross-bedding photo1, cross-bedding photo2 cross-bedding photo3
1. barchan dunes
2. transverse dunes
3. longitudinal dunes
4. parabolic dunes
5. star dunes