People often use the adjectives “hot,” “dry,” and “empty” to describe deserts, but these words do not tell the whole story. Although some deserts are very hot, with daytime temperatures as high as 54☌ (130☏), other deserts have cold winters or are cold year-round. And most deserts, far from being empty and lifeless, are home to a variety of plants, animals, and other organisms. People have adapted to life in the desert for thou sands of years. One thing all deserts have in common is that they are arid, or dry.
Most experts agree that a desert is an area of land that receives no more than 25 centimeters (10 inches) of precipitation a year. The amount of evaporation in a desert often greatly exceeds the annual rainfall. In all deserts, there is little water available for plants and other organisms. Deserts are found on every continent and cover about one-fifth of Earth’s land area.
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They are home to around 1 billion people-one-sixth of the Earth’s population. 00:00 / 03:07 Digital Album Streaming + Download Includes unlimited streaming via the free Bandcamp app, plus high-quality download in MP3, FLAC and more. Although the word “desert” may bring to mind a sea of shifting sand, dunes cover only about 10 percent of the world’s deserts. The dunes appear bright white in the otherwise reddish. The park is situated in the Tularosa Basin and spans roughly the southern half of a 275-square-mile (712-square-kilometer) dune field. Others are dry expanses of rock, sand, or salt flats. An astronaut aboard the International Space Station took this photograph of White Sands National Park in south-central New Mexico. Kinds of Deserts The world’s deserts can be divided into five types-subtropical, coastal, rain shadow, interior, and polar. Deserts are divided into these types according to the causes of their dryness. Subtropical Deserts Subtropical deserts are caused by the circulation patterns of air masses. 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. Hot, moist air rises into the atmosphere near the Equator. As the air rises, it cools and drops its moisture as heavy tropical rains. The resulting cooler, drier air mass moves away from the Equator. As it approaches the tropics, the air descends and warms up again. The descending air hinders the formation of clouds, so very little rain falls on the land below. The world’s largest hot desert, the Sahara, is a subtropical desert in northern Africa. The Sahara Desert is almost the size of the entire continental United States.
Other subtropical deserts include the Kalahari Desert in southern Africa and the Tanami Desert in northern Australia. Coastal Deserts Cold ocean currents contribute to the formation of coastal deserts. Air blowing toward shore, chilled by contact with cold water, produces a layer of fog. Although humidity is high, the atmospheric changes that normally cause rainfall are not present.
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