Big Ben is a volcanic massif that dominates the geography of Heard Island in the southern Indian Ocean. It is a stratovolcano with a diameter of about . Its highest point is Mawson Peak, which is above sea level. Much of it is covered by ice, including 14 major glaciers which descend from Big Ben to the sea. Big Ben is the highest mountain in Australian Territory, except for those claimed in the Australian Antarctic Territory. A smaller volcanic headland, the Laurens Peninsula, extends about to the northwest, created by a separate volcano, Mount Dixon; its highest point is Anzac Peak, at .