Coastal Deserts Cold ocean currents contribute to the formation of coastal deserts. Other subtropical deserts include the Kalahari Desert in southern Africa and the Tanami Desert in northern Australia. The Sahara Desert is almost the size of the entire continental United States. 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 Subtropical deserts are caused by the circulation patterns of air masses. Deserts are divided into these types according to the causes of their dryness. Kinds of Deserts 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. Although the word “desert” may bring to mind a sea of shifting sand, dunes cover only about 10 percent of the world’s deserts. They are home to around 1 billion people-one-sixth of the Earth’s population. Deserts are found on every continent and cover about one-fifth of Earth’s land area. In all deserts, there is little water available for plants and other organisms. 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 thou sands 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. If you are interested in using an image for a publication, please visit for more information and to fill out the online Image Rights and Reproductions Request Form.Deserts are areas that receive very little precipitation. The photograph depicts an expanse of sand dunes in the morning light. Rising pyramid-like in the distance, another dune is enveloped in deep shadow, which lends a sense of ominous magnificence to the scene. The contrast of the light and dark dunes create a composition of interlocking shapes, their hard edges abutting one another. Light spills over this ridge, softly illuminating the striated patterns in the sand.
The two slopes of the dune meet at an exact point, which forms a sinuous, almost serpentine line that meanders vertically away from the viewer. The dawn illuminates the silken, windswept surface of foremost dune’s slope, while its other side remains in shadow. Taken at dawn, this photograph shows an expanse of sand dunes in the raking morning light.
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