What is the Sahara Desert?
The Sahara is the largest hot desert in the world, covering about 9 million square kilometers across North Africa. It is almost as big as the United States or China.
The Sahara stretches about 4,800 kilometers from the Atlantic Ocean to the Red Sea and across parts of 11 countries, including Algeria, Egypt, Libya, Mali, Niger and Sudan. Only about a quarter of it is sand dunes, called ergs. Much of the rest is rocky plateaus, gravel plains, mountains and dry valleys.
Temperatures can exceed 45 degrees Celsius in summer, but nights can be cold, especially in winter. Some areas receive almost no rain for years. Oases, where underground water reaches the surface, support palm trees, crops and towns. Nomadic peoples such as the Tuareg have traveled the Sahara for centuries.
A once-green Sahara
Between about 11,000 and 5,000 years ago, the Sahara was much wetter, with grasslands, lakes and animals like giraffes, elephants and hippos. Ancient rock art shows this green Sahara. Shifts in Earth's orbit changed rainfall patterns and turned it back into desert.
Did You Know?
Antarctica and the Arctic are larger deserts than the Sahara, because a desert is defined by low precipitation, not by heat.