Major deserts of the world
Major deserts of the world — Sahara · Arabian · Gobi · Patagonian · Great Victoria · Kalahari · Thar · Atacama · Namib · Karakum · Sonoran
12 min read · Updated 2026-05-25
What is a desert?
A desert is a region where evaporation exceeds precipitation, formed where air sinks under the sub-tropical high, where distance from the ocean starves the interior of moisture, in the rain shadow of mountains, along coasts cooled by currents, or in polar cold. Antarctica is the largest desert at about 14.2 million square kilometres; the Sahara, at 9.2 million, is the largest hot one.
The story
14th August 1971. A weather instrument at the village of Quillagua, Chile, in the Atacama Desert, records its 412th consecutive year of no measurable rainfall. Investigators later find rain gauges from the Spanish colonial era that suggest some Atacama valleys have not seen a drop of water since the time Columbus sailed. There are stretches of the Atacama where it is statistically more likely you will see a NASA Mars rover prototype (they test there) than rainfall in your lifetime.
Compare: an hour by plane east of the Atacama lies the Amazon, the rainiest place on Earth. The same Pacific coast that grows the lushness of Costa Rica turns into the driest non-polar desert in Chile within 30° of latitude. What separates them is one of the great teaching laws of geography — that deserts are not where it's hot, deserts are where the air sinks.
One-third of Earth's land surface is some form of desert or arid land. Deserts have shaped civilisations (Egypt would not exist without the Nile cutting through Sahara), trade (camel caravans across the Sahel + Silk Route through the Gobi), and modern energy geopolitics (half the world's oil reserves sit beneath the Arabian desert).
Why this matters for UPSC
Syllabus location: GS-I — World Physical Geography (major deserts). Asked 3-4 times in Prelims over the last decade — desert-country pairings, desert types, cold vs hot deserts. Mains uses deserts as case studies for desertification, climate change, water security. High-yield factual zone with map-based recall.