http://www.wallpaperhi.com/Nature/Deserts/desert_sand_dunes_1920x1080_wallpaper_96960
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Dr. Ahmed Abdelhalim
Geomorphology210
Geology Dep. Cairo Univ.
Content
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Desert
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Defination
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Distribution
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Types
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Water and Desert
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Wind action (Eoilan landforms)
Geomorphology210
Geology Dep. Cairo Univ.
What is desert?
Desert: arid land with less than 250 mm (10 inches)
precipitation per year or in which evaporation exceeds
precipitation. No significant vegetation exists. It need NOT be
hot and dry.
•Most arid land lies between latitudes 10o and 30o (N. & S.)
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Geomorphology210
Geology Dep. Cairo Univ.
Atmospheric convection
Falling air creates deserts at 30° north and south latitudes.
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Geomorphology
Geology Dep. Cairo Univ.
Types of Deserts
• 1. Subtropical: Those associated with the circum-global belts
of dry, subtropical air (Sahara, Kalahari, Great Australian)
• 2. Rainshadow: Lee side of mountain ranges in the rain
shadow (Sonoran).
• 3. Continental interiors: with low rainfall (Gobi, Takla Makan
in Asia)
• 4. Coastal deserts where upwelling cold seawater cools the
air, lowering its ability to hold moisture (Peru, Chile, SW
Africa)
• 5. Polar deserts (N. Greenland, ice-free areas in Antarctica)
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Geomorphology
Geology Dep. Cairo Univ.
Desert distribution
*Includes 25% of the world's land area outside the Polar Regions.
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Geomorphology210
Geology Dep. Cairo Univ.
Mountains: Rain-Shadow Deserts
Ex. Atlas mouniatins of Morocco desert
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Geomorphology210
Geology Dep. Cairo Univ.
Coastal and Interior Deserts
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Geomorphology210
Geology Dep. Cairo Univ.
Desert landforms
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Water and Desert
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Wind action (Eoilan landforms)
http://bookcoverimgs.com/depositional-mountains/
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Geomorphology210
Geology Dep. Cairo Univ.
Water and desert landforms
Stages of Development for Desert or Arid Landscape:
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First Stage:
•Playa lakes start to dry up; evaporation > precipitation
•Alluvial fans form -- fan-shaped sediment features
2. Middle Stage:
•Lakes dry up -- playas form
•Alluvial fans dry up -- form bajadas of pediment
3. Late Stage:
•Isolated remnants of resistant rock remain -- inselbergs
•Drainage is internal -- never out of region except major storm
events
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Geomorphology210
Geology Dep. Cairo Univ.
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Geomorphology210
Geology Dep. Cairo Univ.
Pediment-bajada
Eastern Desert
Eastern Desert
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Geomorphology210
Geology Dep. Cairo Univ.
Stages of Development for Desert or Arid Landscape:
1.
First Stage:
•Playa lakes start to dry up; evaporation > precipitation
•Alluvial fans form -- fan-shaped sediment features
2. Middle Stage:
•Lakes dry up -- playas form
•Alluvial fans dry up -- form bajadas of pediment
3. Late Stage:
•Isolated remnants of resistant rock remain -- inselbergs
•Drainage is internal -- never out of region except major storm events
•Intermittent or ephemeral streams drain region
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Geomorphology210
Geology Dep. Cairo Univ.
Erosion by wind (Wind action)
•Deflation
•Deflation armor or desert pavement
•Water table control
•Ventifacts (Yardagns) rock sculpted by work of wind
(sandblasting)
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Geomorphology210
Geology Dep. Cairo Univ.
Desert deflation and pavement
Eastern Desert
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Remote sensing 1
Geology Dep. Cairo Univ.
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Geology Dep. Cairo Univ.
Spires and buttes form when streams reach a temporary
base level and erode laterally. The streams transport the
eroded sediment away from the region.
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Remote sensing 1
Geology Dep. Cairo Univ.
Yardage landforms
Transporting and abrasion
White Desert, Egypt
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Geomorphology210
Geology Dep. Cairo Univ.
Wind-transported sediments
1. Sand ripples
2. Dunes
a. Barchan (crescent-shaped); points downwind; much sand
b. Transverse -- perpendicular to wind; much sand
c. Linear (longitudinal) -- parallel to strong winds; limited sand
d. Parabolic -- crescent points upwind; much sand; vegetation
present
e. Stellate (star-shaped) -- shifting wind direction; much sand
3. Loess -- rock flour usually glacially derived
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Geomorphology210
Geology Dep. Cairo Univ.
Sand ripples
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Geomorphology210
Geology Dep. Cairo Univ.
Sand dunes
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Geomorphology210
Geology Dep. Cairo Univ.
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Geomorphology210
Geology Dep. Cairo Univ.