DESERTS

DESERTS

WHAT ARE DESERTS ?

A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to the processes of denudation. About one-third of the land surface of the world is arid or semi-arid. This includes much of the polar regions where little precipitation occurs and which are sometimes called polar deserts or "cold deserts". Deserts can be classified by the amount of precipitation that falls, by the temperature that prevails, by the causes of desertification or by their geographical location. There are four types of deserts: subtropical deserts are hot and dry year-round; coastal deserts have cool winters and warm summers; cold winter deserts have long, dry summers and low rainfall in the winter; polar deserts are cold year-round.

Deserts are sometimes classified as "hot" or "cold", "semiarid" or "coastal". The characteristics of hot deserts include high temperatures in summer; greater evaporation than precipitation usually exacerbated by high temperatures, strong winds and lack of cloud cover; considerable variation in the occurrence of precipitation, its intensity and distribution; and low humidity. Winter temperatures vary considerably between different deserts and are often related to the location of the desert on the continental landmass and the latitude. Daily variations in temperature can be as great as 22 ?C (40 ?F) or more, with heat loss by radiation at night being increased by the clear skies.

PHYSICAL GEOGRAPHY

A desert is a region of land that is very dry because it receives low amounts of precipitation (usually in the form of rain, but it may be snow, mist or fog), often has little coverage by plants, and in which streams dry up unless they are supplied by water from outside the area. Deserts generally receive less than 250 mm (10 in) of precipitation each year. The potential evapotranspiration may be large but (in the absence of available water) the actual evapotranspiration may be close to zero. Semi-deserts are regions which receive between 250 and 500 mm (10 and 20 in) and when clad in grass, these are known as steppes.

Most hot deserts are found between 15-30? north and south of the equator.

DESERTS OF THE WORLD

Deserts are formed by weathering processes as large variations in temperature between day and night put strains on the rocks which consequently break in pieces. Although rain seldom occurs in deserts, there are occasional downpours that can result in flash floods. Rain falling on hot rocks can cause them to shatter and the resulting fragments and rubble strewn over the desert floor are further eroded by the wind. This picks up particles of sand and dust and wafts them aloft in sand or dust storms. Wind-blown sand grains striking any solid object in their path can abrade the surface. Rocks are smoothed down, and the wind sorts sand into uniform deposits. The grains end up as level sheets of sand or are piled high in billowing sand dunes.

COLD DESERTS.

Deserts are sometimes classified as "hot" or "cold", "semiarid" or "coastal". The characteristics of hot deserts include high temperatures in summer; greater evaporation than precipitation usually exacerbated by high temperatures, strong winds and lack of cloud cover; considerable variation in the occurrence of precipitation, its Intensity and distribution; and low humidity. Winter temperatures vary considerably between different deserts and are often related to the location of the desert on the continental landmass and the latitude. Daily variations in temperature can be as great as 22 ?C (40 ?F) or more, with heat loss by radiation at night being increased by the clear skies.

Cold deserts, sometimes known as temperate deserts, occur at higher latitudes than hot deserts, and the aridity is caused by the dryness of the air. Some cold deserts are far from the ocean and others are separated by mountain ranges from the sea, and in both cases, there is insufficient moisture in the air to cause much precipitation. The largest of these deserts are found in Central Asia. Others occur on the eastern side of the Rocky Mountains, the eastern side of the southern Andes and in southern Australia. Polar deserts are a particular class of cold desert. The air is very cold and carries little moisture so little precipitation occurs and what does fall, usually snow, is carried along in the often strong wind and may form blizzards, drifts and dunes similar to those caused by dust and sand in other desert regions. In Antarctica, for example, the annual precipitation is about 50 mm (2 in) on the central plateau and some ten times that amount on some major peninsulas.

COLD DESERTS OF THE WORLD

1. Greenland

Greenland is the world's largest non- continental and coldest desert. It is famous for having the largest national park in the world, the Northeast Greenland National Park. Temperature of Greenland remains between ?8? to -3.88? Celsius.

2. Gobi

In Asia, Gobi covers the area of Mongolia as well as southern and western part of China. Being situated on the enormous plateau, high altitude is one of the major factors for its cold temperature.

3. Arctic

The Arctic circumscribes the North Pole of the world and extends into several regions including Alaska, Canada, Greenland, Iceland, Norway, Finland, Sweden, and Russia.

4. Namib

Namib is located in southern Africa and is known for its cold temperature. The reason behind cold temperature is its location along the coast of Benguela current. The interesting fact about it is that many shipwrecks can be found up to 50 meters inland ascribed to the movement of the desert.

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