Locations of Deserts

Most deserts lie between 15° and 35° north and south of the equator. They were created by air that rises over the equator and comes down over the Tropic of Cancer and the Tropic of Capricorn. All over the world many deserts lie in these regions. 

How subtropical deserts develop
Image: Klaus Rosmanitz

1. Land over the equator becomes very hot. The hot and wet air rises and it rains a lot in these areas.
2. The air cools down and moves north– and southwards. It gets drier.
3. The cool air sinks to the ground . It dries out over the Tropic of Cancer in the north and the Tropic of Capricorn in the south.
4. Warm air near the surface moves back to the equator. These winds are called trade winds. 

Some deserts are formed in regions that are cut off from the ocean by high mountains. Winds carry wet air from the ocean to the land. When the air climbs over high mountains it  loses most of its moisture and  when it falls down on the other side it becomes very warm and dry. Deserts on the western coast of North America were formed by such winds. 

Many areas have become dry because they are too far away from the ocean. Air loses its moisture by the time it reaches places that are thousands of kilometres from the coast.  

Deserts can also develop near the coast. Cold water moves from the Antarctic northwards along the African and South American coast. The warm air in these places cools down and mixes with the cool water.  There is a lot of fog, but no rain. That’s why the Atacama  desert in Chile and the Namib desert in Africa are among the driest deserts in the world. 

Atacama desert in Chile
Image:Valerio Pillar, CC BY-SA 2.0, via Wikimedia Commons