The Sahara and North African Deserts

The Sahara is the largest hot desert on Earth, covering approximately 9.2 million square kilometers across eleven countries, an area comparable to the contiguous United States or the whole of China. Its persistent aridity is sustained by its position beneath the subtropical high-pressure belt, where descending air within the Hadley cell warms adiabatically and suppresses cloud formation across roughly 20-30 degrees latitude in both hemispheres. Geologically, the Sahara sits atop an ancient Precambrian shield overlain by sedimentary basins such as Murzuq and Kufra, and its highest point, Emi Koussi at 3,415 meters, is an extinct shield volcano in Chad's Tibesti Mountains. The Tanezrouft, a hyperarid plain in Algeria and Mali so barren it is nicknamed the "Land of Thirst," and the Great Sand Sea straddling Egypt and Libya, source of the enigmatic Libyan Desert Glass later set into one of Tutankhamun's pectoral brooches, illustrate the range of landscapes the term "Sahara" actually covers.