Big Ben, Stratovolcano on Heard Island, Australia.

Big Ben is a stratovolcano about 25 km across that covers most of central Heard Island. Its summit, Mawson Peak, reaches 2,745 m, and 14 major glaciers descend from the ice-covered massif to the sea. Photographs show a broad, domed snow surface streaked with dark rock ridges, meeting a dark shoreline.

Big Ben formed about one million years ago, and eruptions at the cone have been recorded since 1881. Documented activity includes the 1993 eruption, satellite-detected events in 2000, and a plume seen from Atlas Cove on 2 February 2016. The summit, Mawson Peak, was first reached on 25 January 1965 by five members of the Southern Indian Ocean Expedition to Heard Island.

The name Big Ben was applied by early sealers and whalers, and the massif also appears in records as Emperor William Peak and Kaiser Wilhelm-Berg. Its summit, Mawson Peak, honours Australian polar explorer Douglas Mawson. The first ascent, on 25 January 1965, was made by five members of the Patanela expedition.

Heard Island is an Australian external territory, and access is controlled by the Australian Antarctic Division; permits are required and logistics are handled through expedition operators. There are no landing facilities, so visitors arrive by ship or helicopter, usually at Atlas Cove, 15 km northwest of Mawson Peak. Weather changes quickly, and the island has no infrastructure or shelter.

The volcano has shown regular activity since 1881 with documented eruptions that produced plumes rising about one kilometer into the air. This ongoing volcanic behavior makes it one of the active volcanoes in the southern Indian Ocean.