Deflation Hollows and Caves

The wind does more than just carry dust. When it blows steadily in one direction for a long time, it acts like a giant broom, sweeping away the loose weathered material lying on top of rocks or on bare soil. This persistent removal of surface material by wind is called deflation, and it is the driving force behind the landforms described here.

The most direct result of deflation is the creation of deflation hollows. As the wind continuously scoops out the loose mantle of weathered rock or soil, it carves out shallow, saucer-like depressions in the ground. These hollows are generally not very deep — they are simply the low spots left behind after the wind has stripped away the surface layer.

Deflation does not only work on flat ground. It also attacks rock surfaces directly, producing numerous small pits and cavities. These tiny, pitted marks are the first stage of a different kind of landform. The rock faces themselves then suffer the impact and abrasion of wind-borne sand — the same sand that the wind is carrying acts like sandpaper, grinding against the rock. This constant battering first creates shallow depressions on the rock face, which are called blow outs. …