Deserts

• A desert is a landscape which receives very little precipitation. These regions receive an average annual precipitation of less than 250 mm.
• The largest hot desert in the world is the Sahara desert in northern Africa which covers over 9 million square kilometres
• Exfoliation, where the outer layer of rock flakes off over time
• Abrasion: Small particles are hurled by the wind against rock surfaces, smoothing the rocks.
• Attrition: Rock particles rub against each other and wear away.
• Exogenous Rivers: Sources outside the desert.
• Ephemeral Rivers: Sources that flow for only part of the year.
• Desert lakes are generally ephemeral and are called playas (also known as dry lakes) which vary in size and are very salty.
• Arid landscapes are areas that have a severely low availability of water , to the extent where it hinders or prevents animal and plant life.
• Rock Pedestals: These are created by wind abrasion processes where the base of rock structures is cut away, leaving a wider top.
• Yardangs: These result from sand grains pushed by persistent winds to form low ridges of sand carved in soft rock.
• Desertification is where fertile land becomes dry, cracked and desert-like, leaving soils unproductive.
• Climatic variations - prolonged high temperatures with infrequent and below average rainfall prevents the growth of vegetation.