Location
Heard Island and McDonald Islands (HIMI) are located in the southwest Indian Ocean at about 53°S, 73°30’E.
The islands are around 4,100km south-west of Perth, Western Australia, and 1,700km north of Antarctica.
The nearest land is the French territory of Îles Kerguelen, an archipelago of islands around 450 kilometres to the north-west.
Heard Island has seen fewer visitors and fewer human disturbances compared with other sub-Antarctic islands.
The region's persistently poor weather, high seas and vast expanses of ocean meant the islands weren't discovered by Europeans until 1853.
The Heard Island and McDonald Islands (HIMI) Marine Reserve covers approximately 380,000km². The marine reserve includes Heard Island and the McDonald Islands. The boundaries and zoning were expanded in 2024 and came into effect on 24 January, 2025.
Geography
Heard Island is approximately 40km long and 20km wide and covers around 368km². The landscape is dominated by Big Ben, Australia's only active volcano and its highest mountain, at 2,745m elevation.
About 70 per cent of Heard Island is permanently covered in glaciers and volcanic activity has been detected there since the 1980s.
Recent volcanic activity has dramatically altered the McDonald Islands. The main island doubled in size and increased elevation sometime in the 1990s, resulting in the complete loss of all vegetation.
HIMI lies south of the Antarctic Convergence, where colder Antarctic waters converge with, and sink under, the slightly warmer waters of the sub-Antarctic.
The islands are home to high numbers of breeding and non-breeding seabirds and marine mammals, including penguins, petrels, elephant seals and fur seals.