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The World's Great Deserts
A desert is not defined by heat or sand. It is defined by dryness: a place that receives very little precipitation, whether it is a scorching dune sea or a frozen plateau. That single fact explains a surprise most people never expect, which is that the largest desert on Earth is Antarctica.
Deserts are not scattered at random. They cluster in a few predictable situations, and once you know the four causes you can often work out why a dry place is dry, and roughly where on the globe it must sit.
Why deserts form
The first cause is the band of high pressure that rings the planet near 30 degrees north and south. Air that rose and rained at the equator sinks here, warm and dry, which is why the Sahara, the Arabian, and the Australian deserts all sit at roughly that latitude. The second is the rain shadow: mountains wring the moisture out of the air, leaving the far side parched, as the Himalaya help do for the Gobi. The third is cold ocean currents, which chill the coastal air so it cannot hold much rain; this is why the Atacama and the Namib are deserts that sit right beside the sea. The fourth is simple distance from any ocean, which leaves continental interiors dry.
The roll call
The Sahara in North Africa is the largest hot desert, roughly the size of the United States. The Arabian desert fills most of its peninsula. The Gobi, straddling Mongolia and northern China, is a cold desert that freezes in winter. Southern Africa has the Kalahari and the ancient coastal Namib. South America has the Atacama, the driest place on Earth, where some weather stations have gone years without measurable rain. And wrapped around the bottom of the world, Antarctica is technically the largest desert of all.
Reading a desert in a clue
Dryness is a strong locator. A clue that mentions a great sand sea near 30 degrees latitude points to the subtropical belt. "The driest place on Earth" is the Atacama, pinned against the Chilean coast. A cold desert with bitter winters leans toward central Asia. Even the word "coastal desert" is a giveaway, because it can only mean a shore chilled by a cold current.
Bottom Line
Deserts form from sinking subtropical air, rain shadows, cold currents, or sheer distance from the sea, and they gather in a handful of predictable places. Treat aridity as a clue, not a detail, and half the world's dry lands will announce their rough latitude and coastline the moment they come up.
At a Glance
| Sahara | North Africa — the largest hot desert (subtropical high) |
|---|---|
| Arabian | Arabian Peninsula (subtropical high) |
| Gobi | Mongolia & northern China — cold desert (rain shadow, interior) |
| Kalahari & Namib | Southern Africa; the Namib is coastal and among the oldest |
| Atacama | Northern Chile — the driest place on Earth (cold current) |
| Antarctica | The largest desert of all — a polar desert |
Frequently Asked Questions
What is the largest desert in the world?
Antarctica is the largest desert, because a desert is defined by low precipitation rather than heat. The largest hot desert is the Sahara in North Africa.
What is the driest desert on Earth?
The Atacama Desert in northern Chile is the driest, with some weather stations recording years without measurable rain, largely because of a cold offshore current.
Why do deserts form near 30 degrees latitude?
Air that rises and rains near the equator sinks back down around 30 degrees north and south, warm and dry, creating a belt of high pressure that produces the Sahara, Arabian, and Australian deserts.
Can a desert be cold?
Yes. Deserts are defined by dryness, so cold deserts exist, including the Gobi in central Asia and the vast polar desert of Antarctica.