Tarso Yega ("well", tedaga[2]) is a stratovolcano in Tibesti, with a summit caldera[3] that is 19 by 20 kilometres (12 mi × 12 mi) wide and 300 metres (980 ft) deep.

The Enneri Yega river drains the caldera westward and then south, before joining the Enneri Debarsar; in the past (Holocene) the rivers reached Lake Chad[5] and lakes formed in Tarso Yega.

[6] The history of the volcano is characterized by the emission of tephras,[7] with the downsagging of the caldera floor generating a depression.

[8] Basaltic vents[9] and lava domes were emplaced within this caldera,[10] and an intrusion named Ehi Yodéï developed 3 kilometres (1.9 mi) farther south.

[11] The caldera is heavily eroded, with almost the entire southern side eroded away,[4] and the younger Voon ignimbrite has been emplaced inside of it; it belongs to a different volcano, Tarso Voon.