Deserts Wallpaper, #5227

A desert is a landscape or region that receives very little precipitation. Deserts can be defined as areas that receive an average annual precipitation of less than 250 mm (10 in), or as areas in which more water is lost than falls as precipitation. In the Köppen climate classification system, Deserts are classed as BWh (hot desert) or BWk (temperate desert). In the Thornthwaite climate classification system, Deserts would be classified as arid megathermal climates.Deserts are part of a wider classification of regions that, on an average annual basis, have a moisture deficit (i.e. they can potentially lose more than is received). Deserts are located where vegetation cover is exceedingly sparse.Deserts sometimes contain valuable mineral deposits that were formed in the arid environment or that were exposed by erosion. Due to extreme and consistent dryness, some Deserts are ideal places for natural preservation of artifacts and fossils.Sand covers only about 20 percent of Earth's Deserts. Most of the sand is in sand sheets and sand seas—vast regions of undulating dunes resembling ocean waves "frozen" in an instant of time. In general, there are six forms of Deserts: