File:Big Ben - Volcanic Massif on Heard Island.jpg

Satellite image of Cape Arkona on Heard Island. Big Ben Volcano and Mawson Peak are in the lower right hand corner of the picture.

English: Heard Island is located in the southern Indian Ocean, approximately 1,550 kilometers (963 miles) north of Antarctica. The island is a visible part of the Kerguelen Plateau, a submerged feature on the seafloor. The plateau was formed when large amounts of volcanic rock erupted over a geologically short time period. (When large amounts of volcanic rock erupt beneath the ocean from processes other than seafloor spreading, geologists refer to them as large igneous provinces.) Most of Heard Island is formed from volcanic rocks associated with the Big Ben stratovolcano. The northeastern slopes of the volcano are visible in shadow at the lower right of this detailed astronaut photograph. Recent volcanic activity at Heard Island has occurred at 2,745-meter (9,006-foot) Mawson Peak, which sits within a breached caldera on the southwestern side of the Big Ben Volcano. Calderas form when a magma chamber beneath a volcano empties and collapses. The shadow cast by Mawson Peak points directly to the crescent-shaped caldera rim. Detailed geologic study of Big Ben Volcano is complicated by the presence of several glaciers, including Gotley and Lied Glaciers on the southwestern slopes. This image, taken during Southern Hemisphere summer, also reveals non-glaciated volcanic rock (light to dark brown) on either side of Gotley Glacier. Caption William L. Stefanov, NASA-JSC.

Source:NASA, 28 February 2009