Desert facts for kids

Valle de la Luna ("Valley of the Moon") in the Atacama Desert of Chile, the world's driest hot desert.

Sand dunes in the Rub' al Khali ("Empty quarter") of Saudi Arabia

A desert is an arid (very dry) biome. They get less than 25 cm (9.8 inches) of rainfall a year. Another source defines it as "any region that can have a moisture deficit over the course of a year. In other words, they can have less rainfall in a year than they give up through evaporation.

These kinds of areas can cover about 33% of the land on Earth. That includes much of Antarctica, where large areas get no snow at all. The largest hot desert is the Sahara desert, in northern Africa, covering 9 million square kilometers.

Deserts land surfaces are various – examples are stones, sand dunes and snow. They have a wide variety of animals and plants. Deserts sometimes expand (desertification), and sometimes contract.

Deserts are mostly found in the western part of the Americas, Western Asia, Central Australia, and South and North Africa. Many, such as the Sahara (the largest), are very hot during the day and have cold nights, but there are also cold deserts such as the Atacama in South America which remain frozen day and night.

Etymology

English desert comes from the ecclesiastical Latin dēsertum (originally "an abandoned place"), a participle of dēserere, "to abandon". In English before the 20th century, desert was often used in the sense of "unpopulated area", without specific reference to aridity; but today the word is most often used in its climate-science sense (an area of low precipitation).

Cold deserts

There are hot deserts and cold deserts. Cold deserts may be covered with snow or ice but some are so dry that the ice sublimates away. Some cold deserts have a short season of above-freezing temperatures. These deserts are called tundra. An ice cap can be a cold desert that remains below freezing all year-round.

Cold deserts can be found close to the poles. That is why they are also called polar deserts. Other regions of the world have cold deserts too, for instance high altitude areas like the Himalayas. These are called montane deserts. Antarctica is the world's largest cold desert.

Hot deserts

Hot deserts are mostly in the subtropics. They can be covered by sand, rock, salt lakes, stony hills and even mountains. Most non-polar deserts are hot in the day and chilly at night. The temperature in the daytime can reach 50 °C (122 °F) or higher in the summer, and dip to 0 °C (32 °F) or lower at night time in the winter.

The largest hot desert in the world is the Sahara in North Africa. It is almost as large as Europe or the United States. The Sahara desert is also the hottest desert in the world.

The driest desert in the world is the Atacama Desert in South America. The Atacama Desert had no rain for 401 years, between 1570 and 1971. This desert is caused by a cold ocean current.

Polar deserts

Polar deserts are a type of cold desert. While they do not lack water, having a persistent cover of snow and ice, this is merely due to marginal evaporation rates and low precipitation.

The McMurdo dry valleys of Antarctica, which lack water (whether rain, ice, or snow) much like a non-polar desert and even have such desert features as hypersaline lakes and intermittent streams that resemble (except for being frozen at their surfaces) hot or cold deserts for extreme aridity and lack of precipitation of any kind. Extreme winds and not seasonal heat desiccate these nearly-lifeless terrains.

Biological deserts

An animation of a year in organism density on Earth. The South Pacific Gyre is an example of a so-called "oceanic desert", visibly low (purple) in organism density. Polar deserts are visible in consistent white and arid deserts in consistent brown, with tundras oscillating between white and brown.

The concept of "biological desert" redefines the concept of desert, without the characteristic of aridity, not lacking water, but instead lacking life. Such places can be so-called "ocean deserts", which are mostly at the centers of gyres, but also hypoxic or anoxic waters such as dead zones.

Rain

It does rain in the desert, but not often. One place in the Atacama Desert had no rain for 401 years. In other deserts it may rain every year or once every few years. Rains in a desert may bring a great amount of water to the ground in a short time. Some rain passes straight into the dry soil, but the rest may form a temporary river. Wadis, stream channels that are normally dry, can quickly fill after heavy rain, causing a flash flood.

People sometimes bring water from wet places to hot deserts so plants can grow. This is called irrigation.

Sandstorm

A sandstorm or dust storm arises when wind blows loose sand and dust from a dry surface. Clouds of sand or dust are often so dense that they obscure the sun. A sandstorm can move whole sand dunes. Sandstorms are common in large, dusty deserts.

Animals and plants

There are not many animals in the desert, but some animals are able to survive. They have different ways to survive the intense conditions of the desert. Examples of animals that live in hot deserts are lizards, small rodents, snakes, and camels. Plants and animals in hot deserts must live with very little water.

Xerophytic plants which live in the desert have special adaptations. They may survive by growing roots that are very near the surface to absorb the rain that may fall before it evaporates. Plants such as the cactus have thick, fleshy stems that help them store water.

Small animals such as lizards and small rodents often escape the hot rays by digging underground burrows where they live. They only come out at night to search for food. Like the plants, desert animals must live on as little water as possible. Most of the water used by these animals comes from seeds and stems that absorb and hold water. Camels survive in hot deserts by storing water in body fat in their humps. Like other desert animals, the camel loses little water in its wastes (urine and feces).

Major deserts

The world's largest non-polar deserts

Deserts take up about one third of Earth's land surface. Bottomlands may be salt-covered flats. Eolian processes are major factors in shaping desert landscapes. Polar deserts (also seen as "cold deserts") have similar features, except the main form of precipitation is snow rather than rain. Antarctica is the world's largest cold desert (composed of about 98% thick continental ice sheet and 2% barren rock). Some of the barren rock is to be found in the so-called Dry Valleys of Antarctica that almost never get snow, which can have ice-encrusted saline lakes that suggest evaporation far greater than the rare snowfall due to the strong katabatic winds that even evaporate ice.

Deserts, both hot and cold, play a part in moderating Earth's temperature. This is because they reflect more of the incoming light and their albedo is higher than that of forests or the sea.

In culture

Marco Polo arriving in a desert land with camels. 14th-century miniature from Il milione.

The desert is generally thought of as a barren and empty landscape. It has been portrayed by writers, film-makers, philosophers, artists and critics as a place of extremes, a metaphor for anything from death, war or religion to the primitive past or the desolate future.

There is an extensive literature on the subject of deserts. An early historical account is that of Marco Polo (c. 1254–1324), who travelled through Central Asia to China, crossing a number of deserts in his twenty four year trek. Some accounts give vivid descriptions of desert conditions, though often accounts of journeys across deserts are interwoven with reflection, as is the case in Charles Montagu Doughty's major work, Travels in Arabia Deserta (1888). Antoine de Saint-Exupéry described both his flying and the desert in Wind, Sand and Stars and Gertrude Bell travelled extensively in the Arabian desert in the early part of the 20th century, becoming an expert on the subject, writing books and advising the British government on dealing with the Arabs. Another woman explorer was Freya Stark, who travelled alone in the Middle East, visiting Turkey, Arabia, Yemen, Syria, Persia and Afghanistan, writing over twenty books on her experiences. The German naturalist Uwe George spent several years living in deserts, recording his experiences and research in his book, In the Deserts of this Earth.

The American poet Robert Frost expressed his bleak thoughts in his poem, Desert Places, which ends with the stanza "They cannot scare me with their empty spaces / Between stars – on stars where no human race is. / I have it in me so much nearer home / To scare myself with my own desert places."

Deserts on other planets

View of the Martian desert seen by the robotic rover Spirit in 2004

Mars is the only other planet in the Solar System besides Earth on which deserts have been identified. Despite its low surface atmospheric pressure (only 1/100 of that of Earth), the patterns of atmospheric circulation on Mars have formed a sea of circumpolar sand more than 5 million km² (1.9 million sq mi) in the area, larger than most deserts on Earth. The Martian deserts principally consist of dunes in the form of half-moons in flat areas near the permanent polar ice caps in the north of the planet. The smaller dune fields occupy the bottom of many of the craters situated in the Martian polar regions. Examination of the surface of rocks by laser beamed from the Mars Exploration Rover have shown a surface film that resembles the desert varnish found on Earth although it might just be surface dust. The surface of Titan, a moon of Saturn, also has a desert-like surface with dune seas.

Images for kids

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  Sand and dunes of the Libyan Desert

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  The Sahara is the largest hot desert in the world

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  Cold desert: snow surface at Dome C Station, Antarctica

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  The Agasthiyamalai hills cut off Tirunelveli in India from the monsoons, creating a rainshadow region.

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  Exfoliation of weathering rocks in Texas, US

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  One square centimeter (0.16 sq in) of windblown sand from the Gobi Desert

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  Dust storm about to engulf a military camp in Iraq, 2005

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  Wind-blown particles: 1. Creep 2. Saltation 3. Suspension 4. Wind current

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  The world's largest non-polar deserts

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  Aerial view of Makhtesh Ramon, an erosion cirque of a type unique to the Negev

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  Windswept desert pavement of small, smooth, closely packed stones in the Mojave desert

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  Atacama, the world's driest non-polar desert, part of the Arid Diagonal of South America

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  Flash flood in the Gobi

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  Xerophytes: Cardón cacti in the Baja California Desert, Cataviña region, Mexico

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  The camel thorn tree (Acacia erioloba) in the Namib Desert is nearly leafless in dry periods.

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  The cream-colored courser, Cursorius cursor, is a well-camouflaged desert resident with its dusty coloration, countershading, and disruptive head markings.

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  The desert iguana (Dipsosaurus dorsalis) is well-adapted to desert life.

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  Tadpole shrimp survive dry periods as eggs, which rapidly hatch and develop after rain.

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  Shepherd near Marrakech leading his flock to new pasture

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  Salt caravan travelling between Agadez and the Bilma salt mines

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  A mining plant near Jodhpur, India

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  Mosaic of fields in Imperial Valley

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  Desertec proposed using the Saharan and Arabian deserts to produce solar energy to power Europe and the Middle East.

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  War in the desert: Battle of El Alamein, 1942

See also

In Spanish: Desierto para niños

• Desertification
• Deserts of Australia
• List of deserts