What makes the Sahara the largest desert in the world?

Category: Earth Science
Published: December 13, 2012

By: Christopher S. Baird, author of The Top 50 Science Questions with Surprising Answers and physics professor at West Texas A&M University

The Sahara is not the largest desert in the world. Antarctica is the largest desert in the world. Deserts are not defined by hot temperatures and sand dunes. Rather, deserts are defined by a very low amount of rain and snow. These low amounts of precipitation lead to very little liquid water on the ground. As a result, deserts are identified by significantly low amounts of animal and plant life. While Antarctica does have a lot of water in the form of ice, its cold temperatures keeps the ice from turning into liquid water even in the summer. The cold temperatures also freeze the water vapor out of the air. The end result is that Antarctica is not only a desert, it is the driest continent in the world. Because the characterizing feature of a desert is dryness and not temperature, there are cold deserts, warm deserts, and hot deserts. This dryness can be caused by a rain shadow effect where mountains block moisture-carrying clouds from reaching the desert region. The dryness of deserts can also be caused by the region simply being too far away from any source of moisture. Lastly, the low moisture characterizing desert terrain can be caused by cold temperatures locking moisture into solid form. The dangers that people associate most commonly with hot deserts; such as sunburn, cracked lips, dehydration, and barren landscapes; are also dangers faced by visitors to Antarctica.

Antarctica is the largest desert in the world. Despite the presence of water in ice form, there is very little water available as liquid to sustain life. Public Domain Image, source: NASA.

Topics: Sahara, atmosphere, desert, dry, humidity, largest desert, polar desert, precipitation, weather