Topic Cover: Desert?, Climate of the Desert, Plants/Animals
and Nomads of the Desert,Minerals

What is Desert?

Deserts that are absolutely barren and where nothing grows
at all are rare and they are better known as ‘true deserts’.

Deserts are outcome of scanty precipitation/rainfall (less
than 25cm), extreme temperature and exceed evaporation.

They lie in the trade wind belt on the Western Parts of the
continents where Trade Winds are off-shore and Westerlies on-shore wind cut-off from the land.

 

Deserts

Deserts Climate Type:

(A) Tropical Deserts/Hot Desert Climate:

• A tropical desert is the hottest and driest place on earth
  where rainfall is very scanty and irregular. This biome is typically found in
  the western parts of the continents within the tropics.
• The major hot deserts of the world are located on the
  western coasts of continents between latitudes 15° and 30°N. and S.
• The hot deserts lie astride the Horse Latitudes or the
  Sub-Tropical High Pressure Belts where the air is descending, a condition least
  favourable for precipitation of any kind to take place.
• The rain- bearing Trade Winds blow off-shore and the
  Westerlies that are on-shore blow outside the desert limits.

Tropical/Hot Deserts are:

In the Northern Hemisphere:

• The Afro – Asian deserts form the longest belt which includes
  the Sahara desert, Arabian desert and the Thar deserts.
• In North America the tropical deserts cover, California,
  Arizona and New Mexico states of USA and it further extends to Mexico.

In the Southern Hemisphere:

• The South America – Atacama desert west of Andes mountains. 
• The Southern Africa – Namibian and the Kalahari deserts and
• In the central and southern parts of Australia – The Great Australian desert. 

 

(B) Mid-Latitude/Continentality Deserts Climate:

• The climatic conditions of the
  mid-latitude deserts are in many ways similar to those of the hot deserts.
  Aridity is the keynote.
• These inland basins lie
  hundreds of miles from the sea, and are sheltered by the high mountains all
  around them. As a result they are cut off from the rain-bearing winds.
• Occasionally depressions may
  penetrate the Asiatic continental mass and bring light rainfall in winter, or
  unexpected convectional storms may bless the parched lands with brief showers
  in summer.  
• Continentality accounts for
  these extremes in temperature, winters are often severe, freezing lakes and
  rivers, and strong cold winds blow all the time.
• When the ice thaws in early
  summer, floods occur in many places. The greatest inhibiting factors to
  settlement are the winter cold and the permanent aridity, besides remoteness
  from the sea.
• The annual range of temperature is much greater than that of
  the hot deserts. Continentality accounts for these extremes in temperature.

Mid-latitude Deserts/Cold Deserts are:

• Gobi Desert
• Turkestan Desert
• Patagonian Desert

 

Reasons of Aridity of Deserts:

• The major hot deserts of the world are located on the
  western coasts of continents between latitudes 15° and 30°N. and S. E.g. Sahara
  Desert.
• Amongst the mid-latitude deserts, many are found on plateaux
  and are at a considerable distance from the sea. E.g. Gobi Desert.

2. Rainfall:

• The hot deserts lie astride the Horse Latitudes or the
  Sub-Tropical High Pressure Belts where the air is descending, a condition least
  favourable for precipitation of any kind to take place.
• The rain- bearing Trade Winds blow off-shore and the
  Westerlies that are on-shore blow outside the desert limits.
• Deserts lies hundred of miles away from sea and rain shadow zone due to leeward area of wind. 

3. Temperature:

• The reasons for the high temperatures are obvious-a clear,
  cloudless sky, intense insolation, dry air and a rapid rate of evaporation.
  E.g. The highest shade temperature recorded is 136°F. on the 13 September 1922
  at Al Azizia, 25 miles south of Tripoli, Libya, in the Sahara.
• The diurnal range of temperature in the deserts is very
  great.
• The annual range of temperature is much greater than that of the hot deserts. Continentality accounts for these extremes in temperature.

Also Read : Desert Landforms & Erosion Mechanism

Desert Vegetation:

• All deserts have some form of vegetation such as grass,
  scrub, herbs, weeds, roots or bulbs.
• The predominant vegetation of both hot and mid-latitude
  deserts is xerophytic or drought-resistant scrub. This includes 
• the bulbous
  cacti, thorny bushes, long-rooted wiry grasses and scattered dwarf acacias.
• Trees are rare except where there is abundant ground water
  to support clusters of date palms.
• Plants, whether annuals or perennials must struggle for
  survival against both aridity and poor soil.
• Most desert shrubs have long roots and are well spaced out
  to gather moisture, and search for ground water.
• Plants have few or no leaves and the foliage is either waxy,
  leathery, hairy or needle-shaped to reduce the loss of water through
  transpiration.
• Some of them are entirely leafless, with pricks or thorns.
  Others like the cacti have thick succulent stems to store up water for long droughts.
  

Animals:

The desert animals are –

The camel, antelopes, fox, spotted hyena, fallow deer, cape
hare, hedgehog etc., live in the desert.

 Nomads in Deserts:

 

Minerals in Desert:

Major Facts About Deserts:

• About 1/5th of the world’s land is made up of deserts.
• They are bathed by cold currents which produce a ‘desiccating effect’ so that moisture is not easily condensed into precipitation.
• Chuquicamata (Atacama Desert) is the world’s largest copper town.
• Recently, the discovery of oil, in many parts of Saharan and Arabian deserts.
• The mean annual rainfall for the Atacama (driest place on
  earth) not more than half of inch.

Also Read : Types of Precipitation/Rainfall