The world’s largest hot desert, the Sahara, is a subtropical desert in northern Africa. The descending air hinders the formation of clouds, so very little rain falls on the land below. As it approaches the tropics, the air descends and warms up again. The resulting cooler, drier air mass moves away from the Equator. As the air rises, it cools and drops its moisture as heavy tropical rains.
Hot, moist air rises into the atmosphere near the Equator. They are found along the Tropic of Cancer, between 15 and 30 degrees north of the Equator, or along the Tropic of Capricorn, between 15 and 30 degrees south of the Equator. Subtropical deserts are caused by the circulation patterns of air masses. Deserts are divided into these types according to the causes of their dryness. The world’s deserts can be divided into five types-subtropical, coastal, rain shadow, interior, and polar. Others are dry expanses of rock, sand, or salt flats. They are home to around 1 billion people-one-sixth of the Earth’s population.Īlthough the word “desert” may bring to mind a sea of shifting sand, dunes cover only about 10 percent of the world’s deserts. In all deserts, there is little water available for plants and other organisms.ĭeserts are found on every continent and cover about one-fifth of Earth’s land area. The amount of evaporation in a desert often greatly exceeds the annual rainfall. Most experts agree that a desert is an area of land that receives no more than 25 centimeters (10 inches) of precipitation a year. One thing all deserts have in common is that they are arid, or dry. People have adapted to life in the desert for thousands of years. And most deserts, far from being empty and lifeless, are home to a variety of plants, animals, and other organisms. Although some deserts are very hot, with daytime temperatures as high as 54☌ (130☏), other deserts have cold winters or are cold year-round. People often use the adjectives “hot,” “dry,” and “empty” to describe deserts, but these words do not tell the whole story. Deserts are areas that receive very little precipitation.
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