What is a desert

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What is a desert?

• An arid region that gets lt10 of rain/year

• Semi-arid regions get 10-20 of rain/year

• Can be hot (Sahara) or cold (Mars)

• May have lots of sand, a little sand, or rocky

• Generally lacks significant vegetation

• Deserts cover roughly 1/3 of the Earths land
  surface

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There are a variety of desert types
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Where do deserts form?

• Rain shadows
• Low to mid latitudes
• Polar Regions

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Mid-latitude/subtropical Deserts

• Examples Sahara, Sonora, Gobi, Australia

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Rain Shadow Deserts

• Examples Great Basin, Chihuahua, Patagonia
• Due to Sierra Nevada, Sierra Madre, Andes

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Coastal Deserts

• Land adjacent to cold ocean currents (dry air)
• Examples Atacama, Namib (Skeleton Coast)

Atacama, Chile - lt 1cm rain per year
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Polar Deserts

• Air is too cold to hold much water
• Antarctic dry valleys, Greenland, N. Canada

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Extraterrestrial Deserts

• The terrestrial planets are very dry places
• Mars, Venus, Moon

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Eolian Processes
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Erosion (Sand-blasting)
Ventifacts
Balanced Rocks
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Transportation
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Dunes

• Transportation and deposition

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Wind sorts sand!
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Deflation

• Wind can only move sand and dust
• Larger stuff is left behind

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Desert Pavement and Varnish
Desert Pavement Thin pebble rich layer Formed
through deflation Fines are winnowed away
Desert Varnish Dark coating of Oxides
Clay Formed through chemical or biological
processes