Desert Landforms

1
Desert Landforms
2
What of land area is desert?
About 30
3
How do desert landscapes differ from humid
landscapes?
Great Basin Fault block mountains
Colorado Plateau
Humid Landscape
4
How do desert landscapes differ from humid
regions?
Humid Regions
Desert Regions

• Angular landforms
• Box-shaped canyons
• Naked landscape reveals geology
• Very little mass wasting
• Most streams are short and short-lived
• End up in internal drainage basins
• Exception exotic rivers

• Rounded hills
• V shaped valleys
• Soil and vegetation mask geology
• Mass wasting
• Streams reach ocean

5
What is the dominant process shaping the desert
landscape?

• Running water or wind?
• Running water is most important

6
Why is running water important in deserts?

• Landscape has little vegetation to absorb water
  so it quickly runs off
• Rain comes in torrential downpours
• A sudden flashflood can move tons of loose rocks
  in minutes

7
United States Deserts

• Most U.S. deserts are rocky deserts
• Colorado Plateau
• Horizontal sedimentary rock
• Basin and Range
• Fault block Mountains

8
Southwest United States
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Where is this?
Colorado Plateau Grand Canyon
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Colorado Plateau

• Alternating hard and soft rock layers
• Hard rocks form cliffs
• Soft rocks form shelves
• Grand Canyon has a stair-step appearance
• Isolated hard rocks mesas and buttes

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Butte
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Fault Block Mountains of Great Basin

• Note the fault block mountains and ranges
• Ranges are eroded by flash floods that cut box
  canyons
• Alluvial fans form at the mouth of canyons

13
Basins and Ranges

• A Alluvial fan
• B Playa
• C Pediment
• D Box Canyon

14
Alluvial fans and Playas

• Fine sands and salts accumulate in playa lakes
• Playa lakes evaporate into saltflats
• Erosion lowers the mountains until the landscape
  forms a surface of low relief called a pediplain

15
Role of Wind is Limited

• Wind erosion take two forms
• Wind abrasion
• Deflation

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Wind Abrasion

• Wind is not as important as once thought in
  carving impressive arches and rocks
• Why?
• Most abrasion is limited to the first 18-24
  inches above the ground
• Abrasion and deflation form desert pavement
• A layer of coarse rocks and pebbles

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Duststorm
Deflation the removal of fine sand and dust by
the wind Leaves behind blow-outs or deflation
hollows
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Sand Dunes

• Depositional landforms
• Sand dunes are relatively rare - 1025

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Barchan Dunes
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Deflation Blowouts