English Project (DESERT)

8/8/2019 English Project (DESERT)

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Deserts are part of a wider classification of regions

that, on an average annual basis, have a moisturedeficit (i.e. they can potentially lose more than is

received). Deserts are located where vegetation

cover is sparse to almost nonexistent. Deserts take

up about one third (33%) of the Earth's land surface.


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Hot deserts usually have a large dual and seasonal temperature range, with

high daytime temperatures, and low nighttime temperatures (due to extremely

low humidity). In hot deserts the temperature in the daytime can reach 45

C/113 F or higher in the summer, and dip to 0 C/32F or lower in the winter.

Water acts to trap infrared radiation from both the sun and the ground, and drydesert air is incapable of blocking sunlight during the day or trapping heat

during the night

Thus, during daylight most of the suns heat reaches the ground, and as soon

as the sun sets the desert cools quickly by radiating its heat into space. Urban

areas in deserts lack large (more than 14C/25

F) daily temperaturevariations, partially due to the urban heat island effect.


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There are four main, interlinked causes of hot deserts:]

The formation of the subtropical high-pressure cell.

The rain shadow effect in the belt of easterly trade winds.The effect of the cold currents off the west coast of the

continents at these latitudes.

The depositing sands of a desert along its border into the

fertile land.


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Bottomlands may be salt-covered flats. Eolian processes are major

factors in shaping desert landscapes. Cold deserts (also known as

polar 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 percent thick continental ice sheet

and 2 percent 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 evaporate

even ice.

Antarctica and the Arctic.


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The 10 largest deserts

Rank Desert Area (km) Area (mi)

1 Antarctic Desert (Antarctica) 13,829,430 5,339,573

2 Arctic 13,700,000+ 5,300,000+

3 Sahara (Africa) 9,100,000+ 3,320,000+

4 Arabian Desert (Middle East) 2,330,000 900,000

5 Gobi Desert (Asia) 1,300,000 500,000

6 Kalahari Desert (Africa) 900,000 360,000

7 Patagonian Desert (South America ) 670,000 260,000

8 Great Victoria Desert (Australia) 647,000 250,000

9 Syrian Desert (Middle East) 520,000 200,000

10 Great Basin Desert (North America ) 492,000 190,000


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The largest hot desert is the Sahara in northern Africa, covering 9 million square

kilometres and 12 countries. A satellite image of the Sahara world's largest hot

desert and third largest desert after Antarctica and the Arctic.


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Thar, the great Indian desert is situated in the

western part of Rajastan.


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Rain shadow deserts form when tall mountain ranges block clouds from

reaching areas in the direction the wind is going. As the air moves over the

mountains, it cools and moisture condenses, causing precipitation on the

windward side. When that air reaches the leeward side, it is dry because it haslost the majority of its moisture, resulting in a desert. The air then warms,

expands, and blows across the desert. The warm, desiccated air takes with it

any remaining moisture in the desert.

TheAgasthiyamalai hills cut offTirunelveli in India from the monsoons, creating

a rainshadow region


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Montane deserts are arid places with a very high altitude; the

most prominent example is found north of the Himalaya especially

in Ladakh region of Jammu and Kashmir, in parts of the Kunlun

Mountains and the Tibetan Plateau. Many locations within thiscategory have elevations exceeding 3,000 meters (10,000 ft) and

the thermal regime can be hemiboreal. These places owe their

profound aridity (the average annual precipitation is often less

than 40 mm/1.5in) to being very far from the nearest available

sources of moisture. Montane deserts are normally cold.


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Deserts may contain great amount of mineral resources over their

entire surface. This occurrence in minerals also determines the

color. For example, the red color of many sanddeserts is a result

of the occurrence oflaterite.Some mineral deposits too are formed, improved, or preserved by

geologic processes that occur in arid lands as a consequence of

climate. Ground water leaches ore minerals and redeposits them

in zones near the water table. This leaching process concentrates

these minerals as ore that can be mined

Cooking in desert


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Deserts have a reputation for supporting very little life, but inreality deserts often have high biodiversity, including animals that

remain hidden during daylight hours to control body temperature

or to limit moisture needs. Some fauna includes the kangaroo rat,

coyote,jack rabbit, and many lizards. These animals adapted to

live in deserts are called xerocoles. Many desert animals (andplants) show especially clear evolutionary adaptations for water

conservation or heat tolerance, and so are often studied in

comparative physiology, ecophysiology, and evolutionary

physiology. One well-studied example is the specializations of

mammalian kidneys shown by desert-inhabiting


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Prickly pearflowerOrgan Pipe cactus in Arizona

Saguaros in the Sonoran Desert ofArizona

Flora ofBaja California Desert, Catavia region,Mexico

"Desert flower"


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Scorpion

Camels Ship of the desert

Turtles


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English Project (DESERT)