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.

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 /semi-

desert region of Turkmenistan, Uzbekistan,

Kyrgyzstan, Tajikistan, and southern Kazakh-

stan. This 215,000 square mile 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

storms are very common in this area and

can form mound that reach up to 40

meters in height.

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. Only a select few have managed to adapt to the harsh habitat.

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.

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 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.

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.

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.

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.

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

PEOPLE OF HOT DESERTS

THE TUAREGS

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

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

southern Algeria, Niger, Maliand Burkina Faso.Traditionally nomadic pastoralists, small

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

languages and 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 a traditionally featured clan membership and social status. 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 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 clan structure, traditional music, poetry and dance. Urbanised Bedouins

often organise cultural festivals, usually held several times a year, in which they

gather with other Bedouins .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.

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.

.

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.

Map showing Areas vulnerable to desertification…

SOME DESERT LANDFORMS 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, 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.

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

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