Alid is an isolated, dissected volcano in the central Danakil depression. Elongated in an E-W direction perpendicular to the orientation of the Alid graben, it consists of a structural dome of uplifted sedimentary rocks rising 700 m above the graben floor, which was produced by intrusion of a silicic magma body. The dome is capped by steep-sided basaltic-to-rhyolitic lava flows. Late-stage eruptions during the late Pleistocene ejected rhyolitic pumice. A 2 x 3 km graben cuts the top of the dome, and the crater that produced the Plinian eruption occupies the western third of the summit depression. Vast lava fields of probable Holocene age originating from fissure vents bank up against the flanks to the NW and SE. Small cones and craters that were the source of the flows are localized along NNW-trending fissures. Fumarolic activity continues from broad areas on the northern summit and flank.