Maarg Manthan · Topic 15.3

Major Deserts of the World (Sahara, Gobi, Kalahari, Atacama, Thar) and Their Formation

Geography › World Physical and Regional Geography · Topic 15.3

The major deserts of the world are the Sahara, Gobi, Kalahari, Atacama and Thar. Hot deserts such as the Sahara and the Thar lie near the tropics under subtropical high pressure, the Atacama is the driest because of a cold current and a rain shadow, the Gobi is a cold desert of the continental interior, and the Kalahari is a semi-arid desert with sparse rainfall. Desert formation is explained by pressure belts, rain shadows, cold currents and distance from the sea.

5 min read · UPSC Prelims · Geography · World Physical and Regional Geography

At a Glance

Largest hot desert Sahara, about 9 million sq km
Driest desert Atacama, Chile
Cold desert Gobi, Mongolia and China
India Thar, Rajasthan
Southern Africa Kalahari, Botswana
Exam link UPSC Prelims, Geography: World Physical and Regional Geography

Where Does It Fit?

This topic follows the major rivers, since only a few, such as the Nile, cross a desert. It builds on the wind landforms in Wind (Aeolian) Erosional Landforms: Pediments, Pediplains, Playas, Deflation Hollows, Mushroom Rocks, and on the pressure belts of General Circulation of the Atmosphere: Hadley Cell, Ferrel Cell, Polar Cell. Previous topic: Major Rivers of the World (Nile, Amazon, Mississippi-Missouri, Yangtze, Volga, Danube). Next topic: Major Lakes of the World (Caspian Sea, Lake Superior, Lake Victoria, Dead Sea).

Where Are the Major Deserts and What Are Their Types?

Desert	Location and area	Type	Cause of aridity
Sahara	North Africa across 11 countries; about 9 million sq km, the largest hot desert	Hot tropical desert	Subtropical high pressure and trade winds; far from moisture
Gobi	Southern Mongolia and northern China; about 1.3 million sq km	Cold desert, with freezing winters	Rain shadow of the Himalayas and distance from the sea
Kalahari	Botswana, Namibia and South Africa; large semi-arid basin of several hundred thousand sq km	Semi-arid sandy desert	Subtropical high pressure and a rain shadow from the Drakensberg
Atacama	Northern Chile and southern Peru; about 100,000 sq km	Coastal hot-cold desert; driest non-polar place	Cold Humboldt (Peru) current and the Andes rain shadow
Thar	Rajasthan, Gujarat, Haryana in India and Sindh and Punjab in Pakistan; about 200,000 sq km	Hot desert with sand dunes	Aravalli ranges are parallel to monsoon winds; low rainfall

Deserts are lands with very low rainfall, generally below 25 cm a year, and high evaporation. Many are not hot at all; the Gobi has winter temperatures well below freezing, and deserts exist in the polar regions. Not all deserts are sandy: much of the Sahara is bare rock (hamada), gravel (reg) or sand seas (erg).

How Do Deserts Form?

Subtropical high pressure: around 20 to 30 degrees north and south, air sinks and warms, so clouds and rain are rare. The Sahara, Arabian, Thar and Australian deserts lie in these belts (see Atmospheric Pressure: Vertical and Horizontal Distribution).
Rain shadow: mountains force moist air to rain on the windward side, leaving the leeward side dry. The Gobi lies behind the Himalayas, and the Patagonian desert behind the Andes.
Cold ocean currents: cool air above a cold current holds little moisture and forms fog but no rain. The Atacama by the Humboldt Current, and the Namib by the Benguela Current, are coastal deserts of this type, as in Major Ocean Currents of the World and Their Effects.
Continentality: places far from the sea, such as the Gobi, get little moisture.
Human causes: overgrazing, deforestation and poor irrigation can extend desert conditions, which is known as desertification.

What Landforms, Life and Resources Are Found in Deserts?

Landforms: wind-formed sand dunes such as barchans and seif dunes, playas, pediments and deflation hollows, described in Wind Depositional Landforms: Barchans, Seif, Parabolic, Transverse and Longitudinal Dunes, and flash-flood wadis and canyons.
Life: xerophytic plants, such as cactus, acacia and date palm, and animals such as camels and lizards that survive on little water. Oases, fed by groundwater, support settlements and date farming.
Sahara: crossed by the Nile; has oil and gas in Algeria and Libya, phosphates in Morocco, and the Tuareg and other nomads. The Sahel on its southern edge is vulnerable to drought.
Gobi: rich in fossils, notably dinosaur eggs, and in coal and copper; the grazing of herders; the Great Green Wall is China’s tree-planting scheme to stop the desert’s spread.
Kalahari: diamonds in Botswana, cattle ranching and the San people.
Atacama: copper, nitrates and lithium; clear skies make it a site for astronomical observatories.
Thar: the most densely populated desert, with the Indira Gandhi Canal bringing irrigation, wind and solar energy, and the Jaisalmer region.

Areas are approximate and different sources give slightly different values.

Why Is This Topic Important?

Map work Location and countries
Causes Pressure, shadow, currents
Link Wind landforms and climate

What Came Next?

The next topic describes the major lakes of the world, some of which, like the Caspian, lie in arid regions. Next topic: Major Lakes of the World (Caspian Sea, Lake Superior, Lake Victoria, Dead Sea).

Key People and Terms

Desertification Spread of desert conditions
Erg Sand sea
Hamada Rocky desert plateau
Oasis Fertile spot fed by groundwater
Wadi Dry valley that floods briefly
Sahel Semi-arid belt south of the Sahara

Exam Corner

Points to Remember

The Sahara is the largest hot desert.
The Atacama is the driest, behind the Andes.
The Gobi is a cold desert.
The Kalahari lies mainly in Botswana.
The Thar is in Rajasthan and Pakistan.

Do Not Confuse With

Hot and cold deserts Sahara versus Gobi
Atacama and Namib Humboldt versus Benguela current deserts
Desert and semi-arid Kalahari receives some rain

Memory Hook

High pressure, shadow, cold stream: the three makers of a desert dream.

Mains Angle

Questions ask for the causes of deserts and their distribution. These points add depth.

Causes Pressure, shadow, currents
Types Hot, cold, coastal
Issues Desertification

A Question You May Face

An original practice question, not a past paper question.

“Explain the factors responsible for the formation of the hot and cold deserts of the world, with suitable examples.”

How to Answer

Define Aridity and rainfall limit.
Factors Pressure, rain shadow, current, distance.
Examples Sahara, Gobi, Atacama.
Conclude Human role in expansion.

GS Relevance

Prelims: location, countries, type and causes of the major deserts. GS Paper 1: world deserts and climatic regions.

Frequently Asked Questions

What is the largest hot desert in the world?

The Sahara is the largest hot desert in the world, covering about nine million square kilometres across eleven countries of North Africa. It lies under the subtropical high-pressure belt, where sinking air and dry trade winds give very little rain and high temperatures.

Which is the driest desert on Earth?

The Atacama Desert in northern Chile and southern Peru is the driest non-polar desert on Earth. It lies in the rain shadow of the Andes and beside the cold Humboldt Current, which cools the air and prevents rain, so some weather stations have recorded almost no rainfall for years.

Why is the Gobi a cold desert?

The Gobi lies in the interior of Asia in southern Mongolia and northern China, far from the sea and in the rain shadow of the Himalayas. Its high altitude and continental climate give very cold winters, while rainfall is below the desert limit, so it is a cold desert.

Where is the Kalahari Desert located?

The Kalahari lies in southern Africa, mostly in Botswana, with parts in Namibia and South Africa. It is a semi-arid sandy basin, not a true desert, since it gets more rain than the Sahara and supports grass, shrubs and wildlife, as well as diamond mining in Botswana.

Which desert of India is part of the world's major deserts?

The Thar Desert, in Rajasthan and parts of Gujarat and Haryana in India and extending into Sindh and Punjab in Pakistan, is a major hot desert of the world. It covers about two lakh square kilometres and is crossed by the Indira Gandhi Canal.

PYQ Practice — Statement Analysis

1 The Atacama Desert lies in the rain shadow of the Andes.

True

The Humboldt current also adds to its dryness.

2 The Gobi is a hot desert.

False

It is a cold desert with freezing winters.

3 The Sahara is the largest hot desert in the world.