Desert

A desert is an arid (dry) biome. They get less than 25 cm (9.8 inches) of rainfall a year.

It is "any region that can have a moisture deficit over the course of a year". In other words, they can have less rainfall in a year than they give up through evaporation".^[5][6]

Including the semi-arid regions, deserts cover about 33% of the land on Earth.^[7] That includes much of Antarctica, where large areas get no snow at all. The largest hot desert is the Sahara desert, in northern Africa, covering nine million square kilometres.

Deserts land surfaces are varied. Examples are stones, sand dunes and snow. They may have some animals and plants. Deserts sometimes expand (desertification), and sometimes contract.

Deserts are mostly in the western part of the Americas, Western Asia, Central and western Australia, Namibia and North Africa. Some, such as the Sahara, are very hot during the day and have cold nights, but there are also cold deserts such as the Atacama in South America which are frozen day and night.^[8]

1. ↑ Vesilind, Priit J. (August 2003). "The driest place on Earth". National Geographic Magazine. Retrieved 2 April 2013. (Excerpt)
2. ↑ "Even the driest place on Earth has water". Extreme Science.
3. ↑ Mckay, Christopher P. (2002). "Two dry for life: the Atacama Desert and Mars" (PDF). AdAstra: 30–33. Archived from the original (PDF) on 2012-06-06. Retrieved 2016-11-02.
4. ↑ Jonathan Amos (2005). "Chile desert's super-dry history". BBC News. Retrieved 29 December 2009.
5. ↑ Universe Today
6. ↑ Marshak 2009. Essentials of Geology, 3rd ed. W.W. Norton. p452. ISBN 978-0-393-19656-6
7. ↑ "What Is a Desert?". pubs.usgs.gov. December 18, 2001. Retrieved April 9, 2011.
8. ↑ "Desert". Encyclopædia Britannica online. Retrieved 2008-02-09.