WIND AND DESERTS

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WIND AND DESERTS Deserts 1. 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
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Winds are driven by differential heating of the
Earths Surface
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Deserts 2. location is determined by patterns
of atmospheric circulation i. Coriolis
Force ii. trade winds iii. horse
latitudes iv. westerlies v. easterlies
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Deserts 3. types of deserts i. Subtropical
(10- 30N S latitude) (1) Sahara ii. Conti
nental Interior (1) Gobi Desert iii. Rainshad
ow deserts (1) Mohabbi desert
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How Does Wind Carries it Load? 1. bedload i.
saltation 2. Suspended load
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Wind Erosion 1. Deflation - removal of loose
material by wind i. deflation
basin-blowout ii. lag deposits 2. Abrasion -
near surface effect caused by impact of saltating
sand grains i. ventifact (sand blasting)
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Deposition of Material by Wind 1. sand dunes
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Deposition of Material by Wind 1. sand
dunes i. types (1) barchan (a) crescent
shaped (b) tips point downwind (c) in
areas that are flat and dry (d) little
vegetation (e) limited supply of
sand (f) constant wind direction
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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
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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
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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
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Deposition of Material by Wind 2. Loess - wind
deposited silt and clay