WIND AND DESERTS 1 Deserts characterized by a

WIND AND DESERTS • 1. Deserts characterized by a lack of precipitation and high evaporation rates i. rainfall is unpredictable ii. when rain does fall, it is intense and of short duration iii. type of weathering (physical or chemical) iv. importance of running water and wind

Winds are driven by differential heating of the Earths Surface

• 2. Deserts location is determined by patterns of atmospheric circulation i. Coriolis Force ii. trade winds iii. horse latitudes iv. westerlies v. easterlies

• Deserts 3. types of deserts i. Subtropical (10°- 30°N & S latitude) (1) Sahara ii. Continental Interior (1) Gobi Desert iii. Rainshadow deserts (1) Mohabbi desert

• How Does Wind Carries it Load? 1. bedload i. saltation 2. Suspended load

• Wind Erosion 1. Deflation - removal of loose material by wind i. deflation basin-blowout ii. lag deposits 2. grains Abrasion - near surface effect caused by impact of saltating sand i. ventifact (sand blasting)

• Deposition of Material by Wind 1. sand dunes

• Deposition of Material by Wind 1. sand dunes i. types (1) barchan (a) (b) (c) (d) (e) (f) crescent shaped tips point downwind in areas that are flat and dry little vegetation limited supply of sand constant wind direction

1. sand dunes i. types (2) parabolic (a) crescent shaped (b) tips point upwind (c) commonly in coastal areas with strong onshore winds (d) abundant sand (e) partial cover of vegetation

1. sand dunes i. types (3) longitudinal (seif dunes) (a) long, parallel ridges (b) aligned parallel to the wind direction (c) winds generally converge from slightly different directions (d) 30 - 100 m high; 100 km long

1. sand dunes i. types (4) transverse (a) long ridges (b) perpendicular to the wind direction (c) sand seas (d) 200 m high; 3 km wide

• Deposition of Material by Wind 2. Loess - wind deposited silt and clay