(a) Distinguish between deflation and abrasion (b) Using specific examples, describe one landform produced by each of the processes ill (a) above (c) Give a...

Answer Details

(a) Difference between deflation and abrasion:

Deflation is the lifting and blowing away of loose, dry, fine material (dust, sand and silt) from the desert surface by the wind, so that the surface is lowered. Abrasion (corrasion) is the wearing away of rock surfaces by the wind using its load of sand grains as tools, rather like a natural sand-blasting; here the wind actively cuts and grinds solid rock. In short, deflation removes already-loose material, while abrasion erodes solid rock by rubbing sand against it.

(b) One landform produced by each process, with examples:

• Landform of deflation - a deflation hollow (blowout): where the wind repeatedly scoops away the loose sand, a shallow, saucer-shaped depression is formed. If the hollow is deepened until it reaches the water table, an oasis may develop. The Qattara Depression in Egypt is a large example.
• Landform of abrasion - a rock pedestal (mushroom rock, or zeugen/yardang): because the sand load is concentrated near the ground, the base of an upstanding rock is undercut faster than its top, leaving a mushroom-shaped rock with a narrow stem and broad cap, as seen in the Sahara.

(c) Two reasons why wind erosion is more active in arid than in humid regions:

• Scanty vegetation cover: deserts have little or no plant cover to bind the soil or shield the surface, so the wind can pick up and move material freely; in humid regions dense vegetation protects and holds the soil.
• Dry, loose surface material: the ground in arid areas is dry, so the fine particles are loose and easily lifted; in humid regions moisture binds the particles together and makes them heavy, so the wind cannot move them (strong steady winds in deserts also aid erosion).