Big Ben is a
volcanic massif that dominates the geography of
Heard Island in the southern
Indian Ocean. It is a composite cone with a diameter of approximately 25 kilometres. Its highest peak is
Mawson Peak, which is 2,745 m
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. A smaller volcanic headland, the
Laurens Peninsula, extends approximately 10 km to the northwest, created by a separate volcano,
Mount Dixon; its highest point is
Anzac Peak, at 715 m.