The Sahara is the world's largest hot desert and third largest desert, after Antarctica and Arctic. At over 9,400,000 square kilometres (3,600,000 sq mi), it covers most of Northern Africa,making it almost as large as China or the United States. The Sahara stretches 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 that composes the northern region of central and western Sub-Saharan Africa.
The Sahara's boundaries are the Atlantic Ocean on the west, the Atlas Mountains and the Mediterranean Sea on the north, the Red Sea and Egypt on the east, and the Sudan and the valley of the Niger River on the south. The Sahara is divided into western Sahara, the central Ahaggar Mountains, the Tibesti Mountains, the Air Mountains (a region of desert mountains and high plateaus), Ténéré desert and the Libyan desert (the most arid region). The highest peak in the Sahara is Emi Koussi (3,415 m/11,204 ft) in the Tibesti Mountains in northern Chad.
The Sahara is the largest desert on the African continent. The southern border of the Sahara is marked by a band of semiarid savanna called the Sahel; south of the Sahel lies Southern Sudan and the Congo River Basin. Most of the Sahara consists of rocky hamada; ergs (large sand dunes) form only a minor part.
Origin : Wikipedia