Deserts
Deserts are regions that receive less than ten inches of rainfall in one year. Antarctica would be the largest desert in the world if the polar regions were being considered. Of the non-polar deserts, however, the Sahara Desert measures in at the largest, covering an area of 3.5 million square miles. The Sahara Desert is located in North Africa and covers one-third of the African continent. It is also the hottest of the non-polar deserts.
Deserts cover one-fifth of the Earth's surface. There are hot and dry deserts as well as cold deserts which vary in plant and animal life from desert to desert. Often, deserts are very hot during the day, but at night, the temperatures can drop forty to fifty degrees. The soil is thin and often infertile. Most view a desert as a region only covered in sand, but only 15% of the world's desert surface is actually sand. Some is small rocks or pebbles and loose gravel that form a sand-like layer in other desert regions.