WIND AND DESERTS

• Deserts
• characterized by a lack of precipitation and high evaporation rates
• rainfall is unpredictable
• when rain does fall, it is intense and of short duration
• type of weathering (physical or chemical)
• importance of running water and wind

• location is determined by patterns of atmospheric circulation
• Coriolis Force
• trade winds
• horse latitudes
• westerlies
• easterlies

• types of deserts
• Subtropical (10- 30N & S latitude)
• Sahara

• Continental Interior
• Gobi Desert

• Rainshadow deserts
• Mohabbi desert

• How Does Wind Carries it Load?
• bedload
• saltation

• Suspended load

• Wind Erosion
• Deflation - removal of loose material by wind
• deflation basin-blowout
• lag deposits

• Abrasion - near surface effect caused by impact of saltating sand grains
• ventifact (sand blasting)

• Deposition of Material by Wind
• sand dunes
• types
• barchan
• crescent shaped
• tips point downwind
• in areas that are flat and dry
• little vegetation
• limited supply of sand
• constant wind direction

• parabolic
• crescent shaped
• tips point upwind
• commonly in coastal areas with strong onshore winds
• abundant sand
• partial cover of vegetation

• longitudinal (seif dunes)
• long, parallel ridges
• aligned parallel to the wind direction
• winds generally converge from slightly different directions
• 30 - 100 m high; 100 km long

• transverse
• long ridges
• perpendicular to the wind direction
• sand seas
• 200 m high; 3 km wide

• Loess - wind deposited silt and clay