(a) Name three processes of wind transportation in an arid region. (b) With the aid of a diagram, describe the characteristics and mode of formation of a de...

(a) The three processes of wind transportation in an arid region are:

1. Suspension: very fine particles, such as dust and silt, are lifted and carried within the air for long distances.
2. Saltation: sand-sized particles are lifted briefly and moved in a series of short hops or bounces.
3. Surface creep (traction): coarse sand grains and small pebbles are rolled or pushed along the ground by the impact of saltating grains and by the wind.

(b) Deflation hollow

A deflation hollow, also called a blow-out, is a broad, shallow, saucer-shaped depression produced when wind removes loose, dry, fine materials from an area of desert surface.

Characteristics

• It is a wide, shallow basin or depression with a concave floor.
• Its sides are generally gently sloping, though the margins may become steep where wind undercuts loose material.
• The floor is commonly covered by coarse pebbles and stones left behind after finer particles have been removed. This residual stony layer is called desert pavement.
• Where deflation continues to the water table, the floor may become damp or contain water, producing an oasis or marshy patch.
• Deflation hollows vary greatly in size, from small blow-outs to very large basins.

Mode of formation

1. In an arid region, a surface of loose, dry sand, silt and dust is exposed because vegetation is sparse.
2. Strong winds pick up and carry away the finest particles by suspension and saltation.
3. Continued removal of material lowers the ground surface and produces a slight depression.
4. The depression traps and concentrates the wind, so that more loose material is removed from it and the hollow becomes wider and deeper.
5. Coarse pebbles, which are too heavy for the wind to carry, remain on the floor as desert pavement. Deepening may cease when moist material or the water table is reached.