Desert
A desert is an ecosystem that receives few rainfalls. They have reputation of having life small, but it depends on the class of desert; in many abundant life exists, the vegetation adapts to small dampness and the fauna usually one hides during the day to preserve dampness, which means that a desert ecosystem is arid, his major characteristic and for ende, not even the technologies of the present they make sustainable the establishment of social groups. The deserts form the most extensive emerged zone of the planet: his total surface is 50 million square, kilometres approximately a third of the terrestrial surface. The deserts have some characteristics jointly. The soil of the desert is composed often of sand, and there can be dunes. The rocky area is typical (a desert which soil is of rocks or pebbles calls itself with the Arabic word hamada)