|Deserts account for 33% of the world's landmass and are huge arid areas with poor soil quality, resulting in very little or nothing in the way of vegetation. Deserts are continually shifting and expanding, due to the wind's influence on the earth's sand. Deserts may be hot or cold, with temperatures often soaring to 50�C during the heat of the midday sun and dropping to below freezing during the course of the night. Rainfall is scarce within desert regions and is usually 200-250mm per year. Plant forms such as cacti that are present in the world's deserts survive because of their ability to store water within their tissue.|
Desert animals like the camel have also adapted to the harsh extremes of the desert by storing water within their 'humps'. Camels can afford to lose up to 27% of their body weight during times without drinking. Because of their inhospitable extremes, deserts are largely uninhabited, although deserts are home to a few nomadic minorities, that wander the land, grazing their cattle where they can.
The famous deserts of the world include the Sahara, Gobi, Negev, Kalahari, Rub al Khali and the Atacama. The mighty Sahara is the world's largest desert and is continually expanding with its mass of shifting sands. It occupies a large chunk of North Africa, 8 million sq km in total area and spanning ten countries. It has a population density of 0.4 people per sq km. The highest point is 3415m and the lowest point -137m. The Gobi Desert is situated in Mongolia and China. Its landmass covers 1,300,00 sq km, with a population density of 0.21 inhabitants per sq km. The highest point is 3760m, with an average height of 1200m. Unlike the Sahara, the Gobi is not a sandy desert and is comprised of just 3% of sand. The rest is comprised of barren rocks and sheer tundra. Parts of the Atacama desert in Chile go without water for years at a time.