Deserts are very hot or very cold places that receive less than 10 inches of annual rainfall. They are vast areas of extremely dry barren, rocky or sandy landscapes that have sparse or no vegetation. Deserts are one of the planet's main types of ecosystems occupying around 20 per cent of the Earth's surface. There are approximately 20 large deserts and many other smaller ones on the planet. The exact number however, varies because there are substantial differences of opinion about desert boundaries and areas, and also because of changes in climate and landscape.
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Deserts of the Americas
The Great Basin (190,000 square miles) is the largest sand and gravel desert in North America. The Chihuahuan Desert (175,000 square miles), a high plateau, stony and mountainous desert in Mexico, is the second-largest and the Colorado Desert (130,000 square miles) is the third largest. The Sonoran Desert (120,000 square miles), covered with sand and gravel, has the most rainfall, whereas the Mojave Desert (15,000 square miles), also covered with sand and gravel plains, has salt flats. Deserts in South America include the cold-winter Patagonian (260,000 square miles) desert in Argentina and the cool-coastal Atacama (54,000 square miles) desert in Chile, the driest place on earth.
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Deserts of Africa
The Sahara Desert (3.5 million square miles) covers most countries in northern Africa -- an area stretching from the Red Sea to the Mediterranean Coast where 4 million people live. It is the largest sandy subtropical desert in the world. Farther south, the Kalahari Desert (220,000 square miles) in southwestern Africa is also a sandy subtropical desert. It spans South Africa, Botswana and Namibia. The Namib Desert, also in southwestern Africa is the oldest desert (13,000 square miles) that has the highest sand dunes on Earth. This cool-coastal desert stretches across the coastal borders of Angola, Namibia and South Africa.
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Deserts of Asia
The Arabian Desert (1 million square miles) in southwestern Asia is the largest sandy subtropical desert in the Arabian peninsula, whereas the cold-winter Iranian Desert (100,000 square miles) is the smallest in Asia. Other deserts in Asia include the Gobi (500,000 square miles), a vast plains rocky desert that stretches across China and Mongolia. The Taklamakan (105,000 square miles) is China's largest sand desert. In Central Asia, the Kara-Kum (135,000 square miles) with its black sandy plains, spans across Uzbekistan and Turkmenistan and the Kyzyl-Kum (115,000 square miles) desert stretches across Uzbekistan, Turkmenistan and Kazakhstan. Farther south, the Thar (175,000 square miles), which has sand plains and hill landforms, stretches across northern India and Pakistan.
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Deserts of Australia
Apart from the Antarctica, Australia is the driest continent on Earth. Deserts account for 18 per cent of the total land. The Great Victoria Desert is the largest Australian desert. It is a subtropical desert (250,000 square miles) that stretches across western and southern. The second largest is the Great Sandy Desert (150,000 square miles) with stretches of red plains and rock formations that span across northern Western Australia. The Gibson Desert, the smaller of the three deserts, is a subtropical desert (120,000 square miles) with sand hills that stretch across Western Australia.
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The Antarctic in the Southern Hemisphere (5.5 million square miles) is the largest (cold tundra) desert in the world. It receives very little precipitation and thus remains barren and covered in snow most of the year. Likewise, the Arctic is also considered a cold tundra desert. Slightly smaller in size (5.4 million square miles), it stretches across many countries in the Northern Hemisphere, including Alaska, Canada, Greenland, Iceland, Norway, Sweden, Finland and Russia.