Theory question 308
Wind and Desert Landforms(a) Outline three differences between deflation and abrasion. (b) Using specific examples, describe the mode of formation of a deflation hollow.
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(a) Deflation is the removal (lifting and blowing away) of loose fine particles by wind, abrasion is the wearing of rock by sand carried in the wind (sand-blasting); deflation needs loose dry material, abrasion needs sand-laden wind hitting rock; deflation lowers the land surface creating hollows, abrasion carves rock features (rock pedestals, zeugen, yardangs); deflation works over wide areas, abrasion is mostly within about 1-2 m of the ground.
(b) Strong wind blows over loose, dry, unconsolidated sand and dust; fine particles are lifted and carried away (deflation); eddies deepen and widen the depression; the process continues until the water table is reached, where moisture binds the particles; the hollow may then hold water as an oasis or salt lake. Examples: Qattara Depression (Egypt), El Faiyum, depressions in the Kalahari and Sahara.
Name a real deflation hollow.