The process of smaller particles being selectively transported by the wind is calleddeflation
(Figure10.26). This means the ground surface gets lower and rockier, as more and more
small particles are blown away. Eventually, most of the smaller particles will have been
removed and the rockier surface left behind is calleddesert pavement. This surface is
covered by pebbles and gravel sized particles that are not easily moved by wind. If no
disturbance from vehicles or animals disrupts the surface, deflation will stop once this rocky
surface has formed.
Figure 10.26: This desert pavement formed in the Mojave Desert as a result of deflation.
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All the particles moved by wind, whether as suspended load or by saltation as bed load,
do the work of abrasion. As one particle hits another, each grain erodes another. You may
have seen workers sandblasting the front of a building in order to remove paint or dirt.
In the natural situation, erosion by wind polishes surfaces of rock. In the desert, rocks
or boulders develop different polished flat surfaces as wind blows from different directions.
These polished stones are calledventifacts(Figure10.27).
Exposed rocks in desert areas often develop a dark brown to black coating calleddesert
varnish.This coating forms on stable rock surfaces that don’t get much precipitation. The
first part of the process is the transport of clay sized particles by wind which chemically react
with other substances at high temperatures. The coating is formed of iron and manganese
oxides. Ancient people carved into these darkened surfaces to makepetroglyphs(Figure
10.28).