Although common in the American Southwest, dust storms occur all over the world. They form when the wind in a dry sandy region – without the moisture needed to hold the earth together – is high enough to dislodge the top layers of dirt.
When the wind displaces these soil particles, silt, and sand they can be transported huge distances via a number of processes, including suspension and saltation. Suspension involves the smallest particles of dust that can literally be suspended in the air and carried on the wind. Saltation, meanwhile, occurs when larger grains bounce along the ground, picking up and dislodging more particles along the way.
In the Thirties, a series of major dust storms tore through the Great Plains of North America. Known as the Dust Bowl, these storms were caused by a combination of serious drought and high winds, as well as a more human factor. During WWI, a high demand for food led farmers to work the land intensively, doing away with crop rotation, leading to loose, dry topsoil. This, together with arid conditions and high winds, resulted in many dust storms that left the landscape unrecognisable.