English: The broad Emi Koussi volcano is a shield volcano located in northern Chad, at the south-eastern end of the Tibesti Range. The dark volcanic rocks of the volcano provide a sharp contrast to the underlying tan and light brown sandstone exposed to the west, south, and east (image lower left, lower right, and upper right). This astronaut photograph highlights the entire volcanic structure. At 3,415 meters above sea level, Emi Koussi is the highest summit of Africa's Sahara region. The summit includes three calderas formed by powerful eruptions. Two older and overlapping calderas form a depression approximately 12 kilometres by 15 kilometres in area bounded by a distinct rim (image centre). The youngest and smallest caldera, Era Kohor, formed as a result of eruptive activity within the past 2 million years.