A desert

A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life.  This includes much of the polar regions, where little precipitation occurs, and which are sometimes called polar deserts or "cold deserts".  Deserts can be classified by the amount of precipitation that falls, by the temperature that prevails, by the causes of desertification or by their geographical location.   Deserts are formed by weathering processes as large variations in temperature between day and night put strains on the rocks, which consequently break in pieces. 

 Rain falling on hot rocks can cause them to shatter, and the resulting fragments and rubble strewn over the desert floor are further eroded by the wind.  Wind-blown sand grains striking any solid object in their path can abrade the surface.  Other desert features include rock outcrops, exposed bedrock and clays once deposited by flowing water.  There may be underground sources of water, in the form of springs and seepages from aquifers. 

  Plants and animals living in the desert need special adaptations to survive in the harsh environment.  Animals need to keep cool and find enough food and water to survive.  Some animals remain in a state of dormancy for long periods, ready to become active again during the rare rainfall.   People have struggled to live in deserts and the surrounding semi-arid lands for millennia. 

 The cultivation of semi-arid regions encourages erosion of soil and is one of the causes of increased desertification.