What desert is home to the Ahaggar and Tibesti Mountains?

The Tibesti Mountains are a mountain range in the central Sahara, primarily located in the extreme north of Chad, with a small extension into southern Libya. The highest peak in the range, Emi Koussi, lies to the south at a height of 3,445 meters (11,302 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 shield volcanoes topped by large craters: 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. 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 Hoggar Mountains, also known as the Ahaggar Mountains, are a highland region in the central Sahara, southern Algeria, along the Tropic of Cancer. The mountains cover an area of approximately 550,000 square km (212,000 square miles). This mountainous region is located about 1,500 km (930 mi) south of the capital, Algiers. The area is largely rocky desert with an average elevation of more than 900 m (3,000 ft) above sea level. The highest peak, Mount Tahat, is at 2,908 m (9,541 ft).