Physical Geography by Alan Arbogast Chapter 18

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Physical Geographyby Alan ArbogastChapter 18
Arid Landscapes and Eolian Processes
Lawrence McGlinn Department of Geography State
University of New York - New Paltz
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Sand Seas
Sahara Desert, North Africa
Nebraska Sand Hills
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Eolian Depositional Landforms

• Sand Dunes form based on 3 components
• Backslope windward surface, erosion
• Crest high point of the dune
• Slipface lee slope, deposition

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Sand Dune Types
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Blowout
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Loess

• Fine-grained, wind-blown silt high in calcium
  usually from alluvial deposits or glacial till
• Can be transported farther than sand

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Loess Deposits around the World
Arid Landscapes and Eolian Processes
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Loess Terraces
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Human Impact/Desertification

• Desertification transforming a vegetated
  landscape to one that is barren susceptible to
  wind erosion
• Population pressure has forced more people to
  clear marginal, semi-arid-to-arid land for
  agriculture firewood
• In wind, cleared land loses topsoil and nutrients
• Vegetation unlikely to reestablish

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Regions Prone to Desertification
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Desertification in African Sahel

• Semi-arid region in transition region from Sahara
  Desert in north to rainforest in south
• Traditionally nomadic herders small, sedentary
  farmers north-south migrations to follow rain
• Into 20th century, European borders resource
  exploitation made people more sedentary
  over-cultivation of soil, overgrazing, and tree
  removal
• Add in extended drought since late 1960s, you
  have desertification

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The Sahel
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Atmospheric Dust Storm
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Desertification in Great Plains

• Great Plains lie east of Rocky Mts in semi-arid
  climate with short grass as dominant natural
  vegetation

Dust Bowl Region
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Desertification in Great Plains

• Early 1900s Americans moved to region to farm,
  plowing and clearing native grasses unusually
  wet period
• 1930s terrible drought hits topsoil blows
  into dust storms called Dust Bowl
• Many migrated to California elsewhere
• Those who stayed have employed irrigation soil
  conservation, including windbreaks, and
  conservation tillage

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Windbreak