Blowing in the Wind: Moving Sediments without Water - Geology - page 208

Suspending particles in air
Particles that are lifted completely away from the surface and carried within the flow of
the wind current are called a suspended load. Particles suspended by wind are usually
silt or clay particles measuring less than 0.15 mm. These small particles (dust) can be
picked up and lifted high into the atmosphere by turbulent wind flow and may remain
suspended for years, traveling across great distances (thousands of kilometers) before
settling back to the earth's surface.
A wind current could not have a suspended load of particles without a bed load. The
speed of wind low close to the surface is very low — so low that even the small
particles of dust cannot be picked up without some other force instigating their move-
ment. The saltation of larger particles provides this force: The bouncing of the larger
grains unsettles the smaller grains, pushing them into the air flow where they can be lif-
ted and suspended in the wind. This is also illustrated in Figure 14-1.
Deflating and Abrading: Features of Wind
Erosion
As wind picks up and carries particles of sediment away, it creates features of aeolian
erosion. Unlike water or ice, wind cannot remove sediment grains from solid rock. But in
arid regions, there is less moisture and vegetation to anchor or hold the loose sediment
particles to the surface. This means the loose particles that have been removed from
rocks by a previous process of erosion or weathering (see Chapter 7) are available for
movement by the wind.
Removing sediments
Wind deflates a surface, lowering it as sediments are removed. This process of wind
erosion is called deflation.
The most common geologic features of deflation are blowouts. Many blowouts
are small, shallow areas, sometimes only a few meters wide and less than a meter
deep, where deflation has occurred. However, other blowouts, called deflation
basins, are much larger — sometimes many kilometers across.