Tibesti Mountains

The Tibesti Mountains straddle the border of Chad and Libya in the central Sahara, spanning roughly 480 kilometers long and 350 kilometers wide over an area of about 100,000 square kilometers. Their central portion is dominated by five broad shield volcanoes, Emi Koussi, Tarso Toon, Tarso Voon, Tarso Yega and Toussidé, with bases reaching up to 80 kilometers across; Emi Koussi, the highest point, reaches 3,415 meters, and average elevations across the range exceed 2,000 meters. The volcanic rock spans a wide compositional range, from basalt and andesite to dacite, rhyolite, ignimbrite, trachyte and trachyandesite, sitting atop a basement of granite, diorite and schist overlain by Paleozoic sandstone. Volcanic activity began during the Oligocene as part of a Saharan hotspot system, with most of the exposed rock dating from the Lower Miocene through the Pleistocene, and eruptions continuing in places into the Holocene. The range holds some of the largest calderas in the world, including Trou au Natron at 8 kilometers across and 768 meters deep, and Tarso Voon, 12 to 13 kilometers across and roughly 1,000 meters deep. This entity documents the Tibesti Mountains specifically as a geological formation built by shield-volcano construction over tens of millions of years.