Previous volcanic activity in the area includes the Cretaceous Sinjrani volcanics, resembling those of Koh-i-Sultan, and activity which produced the Chagai monzonites. The Sinjrani volcanics, about thick, consist primarily of lava. Other rocks are agglomerates, limestone and tuff, and the Cretaceous rocks are mainly andesitic. The monzonitic Chagai intrusions are accompanied by other intrusions with additional minerals. Other formations are the mostly sedimentary Humai formation of the late Cretaceous and the probably Paleocene Jazzak formation. The Chagai topography is dominated by a sand-covered plain, rising to an altitude of . Wind-eroded rocks and dry lake beds are also present. Other tectonic objects are the Ras Koh range, the Mirjawa range and the Chagai Hills east of Koh-i-Sultan. The Sinjrani and Chagai volcanics crop out primarily west of Koh-i-Sultan, and are part of the older Chagai volcanic arc. Some geologists consider Koh-i-Sultan part of the Chagai arc. Two nearby volcanic centres are Damodin and Koh-i-Dalel, and Koh i-Kannesin is northeast of Koh-i-Sultan. The crust beneath the volcano reaches a thickness of about .