Theory question 205
Wind and Desert Landforms(a) Explain the processes of wind erosion. (b) With the aid of a diagram, describe the features of a barchan dune.
Show the model answer
(a) Deflation: wind lifts and blows away loose dry sand and dust, lowering the surface and forming hollows; abrasion (corrasion): sand grains carried by wind blast and scour rock surfaces, especially near the ground, forming rock pedestals, yardangs, zeugens; attrition: grains carried by wind knock against one another and become smaller and rounded.
(b) Crescent-shaped (moon-shaped) dune lying across the wind direction; gentle convex windward slope; steep concave leeward (slip) face; horns point downwind; up to about 30 m high; moves forward as sand is blown up the windward side and slides down the slip face; found singly or in groups on flat desert floors. Diagram (plan and section) showing wind direction, horns, windward and leeward slopes.
Label wind direction on the diagram.