The Sahara is the world's largest hot desert and the world's second largest desert after Antarctica. At over 9,000,000 square kilometers (3,500,000 sq mi), it covers most parts of Northern Africa; an area stretching from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean. To the south, it is delimited by the Sahel, a belt of semi-arid tropical savanna separating the Sahara from Sub-Saharan Africa. The Sahara is almost as large as the continental United States, and is larger than Australia. The Sahara has an intermittent history that may go back as much as 3 million years. Some of the sand dunes can reach 180 meters (600 ft) in height.
- Since there is little precipitation in Antarctica as well, except at the coasts, the interior of the continent is technically the largest desert in the world.
- MIT OpenCourseWare. (2005) "9-10 thousand Years of African Geology". Massachusetts Institute of Technology. Pages 6 and 13
- Arthur N. Strahler and Alan H. Strahler. (1987) Modern Physical Geography–Third Edition. New York: John Wiley & Sons. Page 347