Particles are transported by winds through suspension, saltation, and creep.
Small particles may be held
in the atmosphere in suspension. Upward currents of air support the
weight of suspended particles and hold them indefinitely in the
surrounding air. Typical winds near the Earth's surface suspend particles
less than 0.2 millimeters in diameter and scatter them aloft as dust or
haze.
 Saltation moves small particles in the direction of the wind in a series of short hops or skips. |
Saltation is downwind movement of particles in a series of jumps or skips. Saltation normally lifts sand-size particles no more than one centimeter above the ground, and proceeds at one-half to one-third the speed of the wind. A saltating grain may hit other grains that jump up to continue the saltation. The grain may also hit larger grains that are too heavy to hop, but that slowly creep forward as they are pushed by saltating grains. Surface creep accounts for as much as 25 percent of grain movement in a desert.
Eolian turbidity currents are better known as dust storms. Air over deserts is cooled significantly when rain passes through it. This cooler and denser air sinks toward the desert surface. When it reaches the ground, the air is deflected forward and sweeps up surface debris in its turbulence as a dust storm.
Crops, people, villages, and possibly even climates are affected by dust storms. Some dust storms are intercontinental, a few may circle the globe, and occasionally they may engulf entire planets. When the Mariner 9 spacecraft arrived at Mars in 1971, the entire planet was enshrouded in global dust.
 Dust storm along the Mohave River near Daggett, California, October 24, 1919 (photograph by D. G. Thompson). |
Small whirlwinds, called dust devils, are common in arid lands and are thought to be related to very intense local heating of the air that results in instabilities of the air mass. Dust devils may be as much as one kilometer high.
Information provided by A . S . Walker
http://pubs.usgs.gov