Mount Overlord is a very large mountain which is an extinct stratovolcano, situated at the northwest limit of Deception Plateau, 50 miles inland from the Ross Sea and just east of the head of Aviator Glacier in Victoria Land. Its asymmetrical cone is on the edge of a plateau above Aviator Glacier. While most of the cone is ice-covered, Mount Overlord does have a 1.2-mile (.8 kilometer) diameter caldera. Volcanic rocks from the western slope have been dated to about seven million years, so the volcano is thought to be extinct.