Near the base of the west side of the mountain is the Silurian High Falls Formation, which is red and green shale and sandstone. The east side of the mountain near the base is of the Ordovician Martinsburg Formation which contains slate, shale and sandstone. The top of the mountain has a fairly even elevation ranging between and . There are two exceptions. One is Culver's Gap, which was created by an ancient stream which was diverted and is now a wind gap. The base of Culver's Gap is at least below the top of the mountain. Culver's Gap is located near Culver's Lake, just west of Branchville. The second is a small gap in the mountain, south of Catfish Pond, which is north of the gap. This gap is about deep.