Eolian Systems
•Arid
•No permanent streams
•Vegetation < 15% of its surface
•~24 cm/yr precipitation
Influences on a Desert
•Variations in solar radiation
•Coriolis effect
•Configuration of continents
•Location of mountain belts
Major Deserts of the World
-20oC
35oC
Gobi Desert, Central Asia
Rain Shadow Deserts
Atacama Dessert, Chile
The Eolian System
Ventifacts
Desert Varnish – coating of Fe-oxide
Ventifacts
Eolian/Desert Systems
Water Erosion
Ephemeral Streams
Arroyos
Desert Wind
The Eolian System
Dessert Pavement
Dessert Pavement
Dessert Pavement
Erosion - Deflation Basins
Deflation results in removal of ~ 10s of cm/1000 years
Dust Bowl
Wind Erosion – Abrasion (Yardangs)
Wind transport of sediment
Dust Storm
Dust Storm – 500 x 106 tons
Deposition by wind - Sand Dunes – bedload deposit
Eduard Bohlen – German Freighter ~ 1909
Migrating
Sand Dunes
Cairo, Egypt
Polar Desert - Canada
Transverse Dunes
Parabolic Dunes
•Sand supply is large
•Constant wind direction
Longitudinal Dunes
•Sand supply is abundant
•Wind direction is strong
but varies in direction
slightly
Barchan Dunes
•Sand supply is limited
•Constant wind direction
Star Dunes
•Variable wind direction
•Sand supply is limited
Loess – covers 1/10 of land surface
– Suspended load deposition
Major Loess Fields of the World
Desertification
Desertification
Desertification
Selima Sand Sheet – Sudan
Desertification
Sahara Dessert
Sahel
Lake Chad in the Sahel
Lake Chad 1963
~26,000 square km
Lake Chad 1987
~3,000 square km
1973
1987
2000
Desertification – Great Plains, U.S.A.