include Pic Toussidé at and the Timi on its western side, the Tarso Yega, the Tarso Tieroko, the Ehi Mousgou, the Tarso Voon, the Ehi Sunni, and the Ehi Yéy near the center of the range. The Mouskorbé is a peak notable for its height in the northeastern part of the mountain range. The Bikku Bitti, the highest point in Libya, is nearby, on the other side of the border. The average elevation of the Tibesti Mountains is about ; sixty percent of its area exceeds in elevation. The range includes five shield volcanoes with broad bases whose diameter can reach : Emi Koussi; Tarso Toon, which rises above sea level; Tarso Voon; Tarso Yega; and Tarso Toussidé, which culminates in the peak of the same name. Several of these peaks are topped with large calderas. Tarso Yega has the largest caldera, with a diameter of and a depth of approximately , while Tarso Voon has the deepest caldera, with a depth of approximately and a diameter of . They are complemented by four large lava dome complexes, high and several km wide, all located in the central part of the mountain range: Tarso Tieroko; Ehi Yéy; Ehi Mousgou; and Tarso Abeki, which rises to above sea level. These volcanic complexes are now considered inactive, but according to the Smithsonian Institution were active during the Holocene. Tarso Toussidé is an active volcano that has spewed lava over the past two millennia. Gases escaping from fumaroles on Toussidé are visible when evaporation is low. The volcano's crater, Trou au Natron, is in diameter and deep. On the northwest side of Tarso Voon is the Soborom geothermal field, which contains mud pools and fumaroles that vent sulfuric acid. The sulfur has stained the surrounding soil bright colors. Fumaroles are also present at the Yi Yerra hot springs on Emi Koussi. Tarso Tôh was an active volcano in the early Holocene. The volcanic area of the Tibesti Mountains is located entirely in Chad; it covers about a third of the total area of the Tibesti Mountains and is responsible for between of rock. The rest of the Tibesti Mountains consists of volcanic plateaus (tarsos), located between elevation, as well as lava fields and ejecta deposits. The plateaus are larger and more numerous in the east: the Tarso Emi Chi, the Tarso Aozi, the Tarso Ahon to the north of Emi Koussi, and the