Major Deserts of the World

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Major Deserts of the World
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Locations of deserts

• 23 S. and N. Capricorn Cancer
• Center of continent
• Rain shadow
• Ocean currents e.g., Atacama Desert (Peru and
  Chile). Air moves from cold ocean waters to warm
  land and expands, absorbing moisture.

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Erosion and deserts

• Rain often violent
• No vegetation
• Massive run-off
• Debris flow
• Interior drainage
• Evaporation- playa lake
• Evaporites

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Wind Direction
Fig. 14.4
Tom Bean
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Rate of Sand Movement as a Function of Wind
Velocity
Fig. 14.5
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Wind

• Transportation of fine sand and silt (clay too
  cohesive).
• Saltation (sand) or suspension (dust)
• Dust from the Sahara in Switzerland
• Dust from western US in Iceland

ventefact barchan dune blowouts draa a desert
of hills of sand erg a vast region of sand
(2X Colorado) desert varnish loess playa, playa
- lake, wadi
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Kansas 1937
1000 tons of dust per cubic km _at_100 km/hr
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Frosted and Rounded Wind-blown Sand
Sand blasted sand grains indicate Aeolian
transport.
Fig. 15.6
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Deflation in deserts
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Formation of Desert Pavement
Fig. 14.9b
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Desert Pavement
Fig. 15.8a
David Muench
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Ventifact
Fig. 14.9
E.R.Degginger
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Dune Migration and the Formation of Cross Bedding
Fig. 14.15
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Types of Dunes
Fig. 14.17
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Yardang, Iran
"a keel-shaped crest or ridge of rock, formed
parallel to the prevailing wind direction
Comstock
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Linear Dunes in Saudi Arabia
Prevailing Winds
Fig. 14.11
ERIM
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Coastal Dunes, Peru
Loren McIntyre
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Pleistocene Loess -product of the ice ages
Fig. 14.18
E.R.Degginger
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Loess in China
Fig. 15.19
Stephen C. Porter
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Desert varnish

• Surface coating of Fe and Mn oxides
• Thickness can be used to date age of surface

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Petroglyphs N.Indian Budhists
Peter Kresan
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Dry wash in Flood
Fig. 14.22a
Peter Kresan
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The Day After
Fig. 14.22b
Peter Kresan
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Playa Lake
Fig. 14.23
David Muench
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Evolution of a Mesa
Fig. 14.26b
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Evolution of a MesaLong-continued Erosion
Fig. 14.26c
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Plateau 10-1000 km
Mesa 0.1-5 km
Butte
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1. If a 100 year river flood occurred in Estes
park in 1912 when will it recur? A in 2012 B at
any time C either in 2012, or 2112 or 2212
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2 Deserts occur mostly at what latitudes? A
10-20 degrees north and south B 20-30 degrees
north and south C 30-40 degrees north and south D
40-50 degrees north and south E 50-60 degrees
north and south
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3. A rock layer that slows the passage of
subsurface water is known as an A aquiclude B
aquifer C aquitard D artesian channel E arterial
blockage
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4. What kind of drainage surrounds Mt. Rainier?
A dendritic B trellis C radial D rectangular E
circular
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Clicker time 5. The units of stream discharge
are A cubic meters per second B square meters per
second C meters per second D seconds per cu
meter E seconds per square meter