Types

• subtropical: in the hot dry latitudes between 20 and 30°, both north and south
  
• rain shadow: on the landward side of coastal mountain ranges
  
• coastal: along coasts bordering cold ocean currents
  
• continental interior: deep within continents, far from major water sources
  
• polar: in the cold dry polar regions, both north and south
  
• Location of Deserts
  
• Mountain Rain Shadow Deserts
  
• Formation of Coastal Deserts
  

Weathering

• Weathering
  
  • Not as effective as in humid regions
    
  • Mechanical weathering forms unaltered rock and mineral fragments
    
  • Some chemical weathering does occur
    
    • caliche-rich soils
      
    • desert varnish
      
• Water Erosion
  
  • Desert rainfall
    
    • Rain often occurs as heavy showers
      
    • Causes flash floods
      
    • Poorly integrated drainage
      
  • Most erosional work in a desert is done by running water
    
    • Streams are dry most of the time
      
    • Desert streams are said to be ephemeral
      
    • Flow only during periods of rainfall
      
    • Different names are used for desert streams including wash, arroyo, wadi, donga, and nullah
      
• Wind erosion
  
  • Deflation
    
    • Lifting of loose material
      
    • Produces
      
      • Blowouts
        
      • Desert pavement
        
  • Abrasion
    
  • Loess
    
    • Deposits of windblown silt
      
    • Extensive blanket deposits
      
    • Primary sources are deserts and glacial stratified drift

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Desert Landforms

• Rocky desert areas change over time
  
  • Pediments
    
  • Mesas
    
  • Buttes
    
  • Chimneys
    
  • Hoodoos
    
  • Cuestas
    
  • Dip slopes
    
  • Inselbergs
    
  • Bornhardts
    
• Sand dunes
  
  • Mounds and ridges of sand formed from the wind's bed load
    
  • Characteristic features
    
    • Slip face – the leeward slope of the dune
      
    • Cross beds – sloping layers of sand in the dune
  • Types of sand dunes
    
    • Barchan dunes
      
    • Transverse dunes
      
    • Longitudinal dunes
      
    • Parabolic dunes
      
    • Star dunes
      

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Basin and Range

• Basin and Range: the evolution of a desert landscape
  
  • Uplifted crustal blocks
    
  • Interior drainage into basins produces:
    
    • Alluvial fans and bajadas
      
    • Playas and playa lakes
      
  • Erosion of mountain mass causes local relief to continually diminish
    
  • Eventually mountains are reduced to a few large bedrock knobs called inselbergs projecting above a sediment filled basin
    

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