Wind erodes the Earth’s surface by deflation, the removal of loose,
fine-grained particles by the turbulent eddy action of the wind, and by
abrasion, the wearing down of surfaces by the grinding action and sand
blasting of windborne particles.
Most eolian deflation zones are composed of _desert pavement_, a
sheetlike surface of rock fragments that remains after wind and water
have removed the fine particles. Almost half of the Earth’s desert
surfaces are stony deflation zones. The rock mantle in desert pavements
protects the underlying material from deflation.
[Illustration: The sand and rock of China’s Turpan Depression resemble
closely those in the view of the Martian surface on page 21.]
[Illustration: The arrow points to shiny black desert varnish on these
rocks of Egypt’s southwest desert (photograph by Carol Breed).]
A dark, shiny stain, called _desert varnish_ or rock varnish, is often
found on surfaces of some desert rocks that have been exposed at the
surface for a long period of time. Manganese, iron oxides, hydroxides,
and clay minerals form most varnishes and provide the shine.
Deflation basins, called _blowouts_, are hollows formed by the removal
of particles by wind. Blowouts are generally small, but may be up to
several kilometers in diameter.
Wind-driven grains abrade landforms. Grinding by particles carried in
the wind creates grooves or small depressions. _Ventifacts_ are rocks
which have been cut, and sometimes polished, by the abrasive action of
wind.
Sculpted landforms, called _yardangs_, are up to tens of meters high and
kilometers long and are forms that have been streamlined by desert
winds. The famous sphinx at Giza in Egypt may be a modified yardang.
Yardangs of the Lut Desert of Iran. These yardangs are among the
largest on Earth, with almost 100 meters of relief.
[Illustration: View from Landsat.]
[Illustration: View from high-altitude photograph (photograph by U.S.
Air Force).]
[Illustration: View from low-altitude photograph (photograph by J.T.
Daniels).]