10.1. Mechanism of wind Action in deserts

Attrition: When wind borne particles roll against one another in collision they wear each other so that their sizes are greatly reduced and converted into finer materials.

Deflation: The complete blowing away of fine dust, leaving coarse and heavier materials, is known as deflation. As a result of deflation, larger hollows known as blow-outs are formed. Deflation also exposes bedrock to wind abrasion (corrasion). There are numerous blow-outs (deflation hollows) in the valley of the Nile.

Abrasion or Corrosion: In the process of abrasion, winds pick up dust and sand and drive them with tremendous force against the rocks. In fact, in the desert and semi-desert areas, winds carry with them enormous quantities of sand, dust and small angular fragments which act as tools of erosion as they strike against the rock surfaces. By this process, the less resistant rocks

are eroded and in time completely worn away, while the hard and very resistant rocks are polished and smoothed to a remarkable degree.