Sahara

The Sahara spans roughly 9.2 million square kilometres across North Africa, close to the size of the United States. Antarctica is bigger overall, but it is a cold desert.

Sources give between 9.1 and 9.4 million km² depending on where the desert edge is drawn.

Context

The Sahara stretches from the Atlantic coast of Africa to the Red Sea and covers parts of around a dozen countries, including Algeria, Libya, Egypt, Chad, Sudan, and Mali. Its area is close to that of the United States or China. Much of it is not sand dunes at all: most of the surface is bare rock plateaus, gravel plains, salt flats, and mountain ranges, with dune fields called ergs covering only a minority.

Where the desert begins and ends is a matter of definition, which explains the range of published sizes. The southern edge borders the Sahel, a semi-arid transition zone where rainfall rises gradually, and mapmakers place the boundary using rainfall or vegetation thresholds. The desert has also grown and shrunk with climate: about 6,000 to 11,000 years ago a wetter period, called the African Humid Period, turned parts of it green.

Antarctica is larger in area, at roughly 14 million square kilometres, and counts as a desert because it receives very little precipitation. The Sahara is the largest of the hot deserts, which is why the label uses that qualifier.