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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.

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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

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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.

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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 -7.78°- -

3.88° Celsius.

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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. The

seasonal temperature that changes on

the land is due to Serbian moves.

3. Arctic

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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5.Turkestan

The desert lies in the region of central Asia.

Turkish people used to live here. The cold desert

is also home to gerbils, tortoises, and gazelles.

Turkestan Desert is a desert or

semi-desert region of Turkmenistan, Uzbekistan,

Kyrgyzstan, Tajikistan, and southern Kazakhstan.

As you can guess by now, this 215,000 square

miles desert covers five different

countries. Turkestan Desert is a cold desert and

has long winters

6.Antarctica

Antarctica is considered as the driest,

windiest and coldest continent in the world.

In fact, the world’s coldest temperature was

recorded at Vostok Station in 1983 . The

reason behind its weather is landmass

elevation and ocean temperatures.

7.Atacama

Atacama desert is situated in South

America. It is considered as the driest and

non-polar desert in the world. It is also

noticed that the Atacama desert has been

described as very similar to Mars’ surface.

8.Iranian

The Iranian desert is famous for

its marshes and seasonal lakes due

to the runoff from nearby

mountains. Sand storm is very

common in this area and can form

mound that reach up to 40 meters

in height.

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ANIMAL AND PLANT LIFE IN COLD DESERTS.

Cold desert animals--even the ones that also live in hot and dry deserts--burrow into the

ground to stay warm. Dry desert animals burrow to stay cool. Animals such as badgers,

kit foxes, coyotes and lizards also burrow into the ground. Only jack rabbits tend not to.

Cold desert animals usually come out when the temperature is at its warmest.

Mammals

Temperature Adaptations

Plants

Like many cold environments, plants in cold deserts tend to be deciduous. They also have spiny

leaves, which can help prevent evaporation or protect the plant in the fight for scarce

resources. Their shallow and widely spread root systems help absorb as much water as

possible, so they tend to be widely scattered. Plant height can vary between 6 to 48

inches. Cacti, sagebrush and ocotillo are a few of the plants that make their home there.

Cold deserts are also populated by many small mammals that horde food and are stingy

about what they eat. These include kangaroo rats, kangaroo mice, pocket mice,

grasshopper mice and ground squirrels. Larger mammals such as antelopes, deer and

camels can also be found in cold deserts.

Mammals are more likely to appear in cold deserts than reptiles. With coats of fur and

warm blood (meaning that they can maintain a stable internal temperature even when

the ambient atmospheric temperature dips), mammals are well-adapted to deal with

freezing winters. However, some lizards and snakes do make their homes in certain

cold deserts.

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PEOPLE OF COLD DESERTS

THE SAMI PEOPLE...THE LAPPS.

The Sámi people (also spelled Saami) are a Finno-Ugric people inhabiting Sápmi, which

today encompasses large parts of Norwayand Sweden, northern parts of Finland, and

the Murmansk Oblast of Russia. The Sámi have historically been known in English

as Lapps or Laplanders. Sámi ancestral lands are not well-defined. Their traditional

languages are the Sámi languages and are classified as a branch of the Uralic language

family.

Traditionally, the Sámi have pursued a variety of livelihoods, including coastal fishing, fur

trapping, and sheep herding. Their best-known means of livelihood is semi-

nomadic reindeer herding. Currently about 10% of the Sámi are connected to reindeer

herding, providing them with meat, fur, and transportation. 2,800 Sámi people are actively

involved in reindeer herding on a full-time basis. For traditional, environmental, cultural, and

political reasons, reindeer herding is legally reserved for only Sami people in some regions

of the Nordic countries.

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WHAT CAUSES HOT DESERTS TO FORM ?

A. Some deserts are found on the western edges of continents. They are caused by cold

ocean currents, which run along the coast. They cool the air and make it harder for the

air to hold moisture. Most moisture falls as rain before it reaches the land, eg the

Namib Desert in Africa.

B. Some deserts form in the rain shadow of mountains, eg the Atacama Desert is located

in the rain shadow of the Andes. Air is forced to rise over mountains, air cools and

condensation occurs, rain falls over the mountains, dry air sinks down the other side of

the mountain.

C. Some deserts form in areas that lie at great distances from the sea. The air here is

much drier than on the coast.

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HOT DESERTS OF THE WORLD

1. Sahara Desert

The Sahara Desert is the world's largest

hot desert; it stretches over 3,500,000

square miles in Northern Africa.

he Sahara is a desert located on the

African continent. It is the largest

hot desert in the world, and the third

largest desert overall after Antarctica

and the Arctic.

2. The Great Victoria Desert

The Great Victoria Desert stretches across

163,900 square miles in both South

Australia and Western Australia.

3. Arabian Desert

Summers in the Arabian desert are quite

intense; temperatures can reach as high as

129 °F.

4. Syrian Desert

The Syrian Desert stretches across

200,000 square miles and only received

about five inches of rain annually.

5. Kalahari Desert

The Kalahari Desert is a large, arid, sandy

area in Southern Africa extending 350,000 square miles.

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How plants adapt to arid conditions

Eg cactus plants:

• thick, waxy skin to reduce loss of water and to reflect heat

• large, fleshy stems to store water

• thorns and thin, spiky or glossy leaves to reduce water loss

• spikes protect cacti from animals wishing to use stored water

• deep roots to tap groundwater

• long shallow roots which spread over a wide area

• plants lie dormant for years until rain falls.

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How animals adapt to extremely arid conditions

• long eye lashes, hairy ears and closing nostrils help to keep out sand

• thick eyebrows which stand out and shade eyes from the sun

• wide feet so they don't sink in the sand

• they can go without water for over a week because they can drink gallons in one

go

• they can go months without food - they store fat in their humps

• body temperature can change to avoid losing water through sweating

• they are well camouflaged

• thick fur helps to keep them warm at night

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PEOPLE OF HOT DESERTS

THE TUAREGS

The Tuareg people are a large Berber ethnic confederation. They principally inhabit

the Sahara in a vast area stretching from far southwestern Libya to south-

ern Algeria, Niger, Maliand Burkina Faso.Traditionally nomadic pastoralists, small groups

of Tuareg are also found in northern Nigeria. The Tuareg speak the Tuareg

languages (also known as Tamasheq), which belong to the Berber branch of

the Afroasiatic family.[

The Tuaregs have been called the "blue people" for the indigo-dye coloured clothes they

traditionally wear and which stains their skin.A semi-nomadic Muslim people, they are

believed to be descendants of the Berber natives of North Africa. The Tuaregs have

been one of the ethnic groups that have been historically influential in the spread of

Islam and its legacy in North Africa and the adjacent Sahel region.

Tuareg society has traditionally featured clan membership, social status and caste

hierarchies within each political confederation. The Tuareg have controlled

several trans-Saharan trade routes and have been an important party to the conflicts in

the Saharan region during the colonial and post-colonial era.

BEDOUIN ARABS

The Bedouin or Bedu are a grouping of nomadic Arab people who have historically

inhabited the desert regions in North Africa, the Arabian Peninsula, Iraq and

the Levant.The English word Bedouin comes from the Arabic badawī, which means "desert

dweller". Bedouin territory stretches from the vast deserts of North Africa to the rocky

sands of the Middle East.[15] They are traditionally divided into tribes, or clans and share

a common culture of herding camels and goats. The vast majority of Bedouin adhere

to Islam.

While many Bedouins have abandoned their nomadic and tribal traditions for a modern

urban lifestyle, many retain traditional Bedouin culture such as retaining the

traditional ʿclan structure, traditional music, poetry, dances and many other cultural

practices and concepts. Urbanised Bedouins often organise cultural festivals, usually held

several times a year, in which they gather with other Bedouins to partake in and learn

about various Bedouin traditions—from poetry recitation and traditional sword dances to

playing traditional instruments and even classes teaching traditional tent knitting.

Traditions like camel riding and camping in the deserts are still popular leisure activities

for urbanised Bedouins who live within close proximity to deserts or other wilderness

areas.

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Desertification

This is the process that sees productive

land turned into non-productive desert. It

usually affects dry areas on the edge of

deserts, eg The Sahel, south of the

Sahara Desert in Africa.

What causes desertification?

Desertification is a complex process. It is caused by physical processes and human

mismanagement. Factors which may cause desertification include:

1. Climate change - especially long dry periods, causing drought. The dry conditions

cause the vegetation to die, so the land loses the protective cover that the vegetation

provides.

2. Too many animals within the area - leads to overgrazing.

3. Population growth - traditional, less intensive, methods of farming decline. There is

more pressure on the land for growing crops. Nomadic tribes that once moved around

may start to farm in one area. Marginal land that is less suitable for farming is used.

Wood is also used for buildings, heating, and firewood, causing deforestation and soil

erosion.

What are the effects of desertification?

• Lack of vegetation cover for holding soil together and for grazing.

• Increased soil erosion.

• Crop failure, leading to famine.

• Fewer plant and animal species.

• Land is unable to support people so they are forced to migrate.

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How can desertification be solved?

• Reduce grazing - so plants have a chance to grow again.

• 'Magic stones' - circles of stones are placed on the ground to hold water on the soil

rather than let it run quickly across the surface. This reduces soil erosion.

• Planting trees - providing shelter from the wind.

• Mulching - adding layers of leaves or straw can reduce evaporation and add nutrients

to the soil when they rot.

• Terracing or contour ploughing - soil is not washed down the slope when it rains.

• Drought-resistant plants - used to stabilise sand dunes.

Recent evidence suggests that there are some areas where the process of desertification

has slowed down. However, the areas on the edge of deserts are still fragile and need

very careful management.

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S O M E D E S E R T L A N D F O R M S

Landforms shaped by Wind

Rock Pedestals

Oasis

Oasis' are found in the middle of deserts as

fertile spots containing one or more springs

surrounded by vegetation. This is caused by

a variety of different temperature

extremes causing islands of life. This

outcome is due to oasis usually been located

in parts of the desert where the elevation is

low enough meaning the water table is

underneath the surface, allowing life to grow through their roots extending into the moist

land. Water is able to run right through the sand as it is holey hence why the water can stay

underneath the surface especially when large quantities of sand is moved due to wind

erosion.

Areas where there is little or no vegetation are usually the most effected places that

experience shaping due to wind. This happens when the wind picks up weathered rock

materials and uses them to sand-blast larger rock structures on the zone closet to the

ground. The formation of rock-strewn reg surfaces has resulted in the removal of finer

material by wind. The wind also plays an important role in moving and reshaping dunes.

Examples of landforms that are obvious in deserts are rock pedestals, Yardangs, Desert

Oasis and Sand dunes.

Rock pedestals are landforms created by

abrasion in which grains cut away the base

of rock structures but leaves their tips

intact. This is due to wind-borne sand grains

following bouncing trajectories that carry

sand as high as 1m above the ground.

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Sand Dunes

Yardangs

There are two different types of sand dunes which are the barchan dunes and seif

dunes. These are differentiated as barchan dunes are produced by the action of wind

predominately convex facing from one direction forming crescent-shaped dunes ,

whereas the seif dunes are long and narrow or can be a chain of dunes. These dunes

are generally orientated in a direction parallel to the wind or in a direction in which

have been the result of two or more winds blowing at acute angles to each other. Wind

directions can also alter the series of peaks, gaps, steepness and the face of the sides.

These sand dunes are mostly found in open deserts and rest on a base of a sand

sheet. Sand dunes are a result of deposition processes.

Similarly Yardangs are also the result of sand grains pushed by persistent winds to

form low ridges of sand carved in soft rock. This is commonly found in flat deserts

where steady winds blow away dust and silt. Higher front faces of Yardangs are

undercut as erosion is concentrated in the lower areas because wind driven sand stays

near the ground. These are an example of erosional landforms