The Tibesti Mountains are a mountain range in the central Sahara, primarily located in the extreme north of Chad, with a small portion located in southern Libya. The highest peak in the range, Emi Koussi, lies to the south at a height of 3,415 meters (11,204 ft) and is the highest point in both Chad and the Sahara. Bikku Bitti, the highest peak in Libya, is located in the north of the range. The central third of the Tibesti is of volcanic origin and consists of five volcanoes topped by large depressions: Emi Koussi, Tarso Toon, Tarso Voon, Tarso Yega and Toussidé. Major lava flows have formed vast plateaus that overlie Paleozoic sandstone. The volcanic activity was the result of a continental hotspot that arose during the Oligocene and continued in some places until the Holocene, creating fumaroles, hot springs, mud pools and deposits of natron and sulfur. Erosion has shaped volcanic spires and carved an extensive network of canyons through which run rivers subject to highly irregular flows that are rapidly lost to the desert sands.
The Tibesti east of Bardaï
False-color, exaggerated-relief satellite image of the Tibesti Mountains viewed from the south
Satellite image of Emi Koussi
Satellite image of Tarso Toon (top right) and Ehi Yéy (bottom left)
The Sahara is a desert spanning across North Africa. With an area of 9,200,000 square kilometres (3,600,000 sq mi), it is the largest hot desert in the world and the third-largest desert overall, smaller only than the deserts of Antarctica and the northern Arctic.
The Sahara taken by Apollo 17 astronauts, 1972
A satellite image of the Sahara by NASA WorldWind
An oasis in the Ahaggar Mountains. Oases support some life forms in extremely arid deserts.
Sand dunes in the Algerian Sahara