The Kohor pumices and two sets of ignimbrites cover the flanks of Emi Koussi, which steepen as they approach the summit. Scoria cones on the slopes are accompanied by lava flows. On the upper sectors of the volcano, lavas are crisscrossed by cracks, which are known as lappiaz. Sandstone crops out on the terrain surrounding the volcano. North of Emi Koussi lie other volcanoes, such as Tarso Ahon and Tarso Emi Chi, the former of which is connected to Emi Koussi by a narrow ridge.