Shortcut Navigation:

Physical Geography and Rainfall

Dry Lands

Deserts are places that get less than 25 centimeters (10 inches) of rain a year. Why do such rain-free areas exist? For a variety of reasons, but mostly because of the wind patterns in the tropics.

Frozen Desert

Deserts aren't always hot. In the Dry Valleys of Antarctica (above), average annual temperature is -20°C (-4°F) and precipitation can be as low as 10 millimeters (0.4 inches) a year. These deserts are created by cold winds tumbling off the Antarctic plateau and roaring down the valleys.

Why are deserts where they are?

Sahara and Australian deserts: Many deserts are located at about 30° latitude north or south of the Equator. In this region, the Hadley circulation causes dry air to descend from the upper atmosphere, creating regions of little rain.

Patagonia Desert: Moist air from the Pacific drops its moisture as it crosses the Andes mountains, creating the deserts of Patagonia east of the Andes.

Atacama Desert: On some coasts, upwelling of cold water chills the air and makes prevailing winds cold and dry. In parts of Chile's Atacama Desert, no rainfall has ever been measured.

American Museum of Natural History

Central Park West at 79th Street
New York, NY 10024-5192
Phone: 212-769-5100

Open daily from 10 am-5:45 pm
except on Thanksgiving and Christmas
Maps and Directions

Enlighten Your Inbox

Stay informed about Museum news and research, events, and more!