Australia's most remote territory is a volcanic laboratory that has doubled in size

Countries & Cities · Published 29 September 2026 Swipe more like this →

In short: Located 4000 kilometres from the Australian mainland, Heard Island and the McDonald Islands are among the most isolated places on Earth. This sub-Antarctic territory contains Australia's only active volcanoes, including the towering Mawson Peak, and has undergone dramatic geological transformations, including a massive expansion of its volcanic landmass.

The territory sits atop the Kerguelen Plateau, a vast igneous province that began forming 130 million years ago. While Heard Island itself has been developing for roughly 22 million years, the McDonald Islands are geologically younger, having formed within the last 100,000 years. The islands are products of the Kerguelen hotspot, a plume system that has driven volcanic activity for millions of years. This activity is not merely historical; Mawson Peak on Heard Island remains active, regularly emitting steam and occasional lava flows.

The McDonald Islands have experienced particularly rapid change. After roughly 75,000 years of dormancy, volcanic activity resumed in the 20th century. Eruptions during the 1990s caused the islands to rise by nearly 100 metres in elevation. Between 1994 and 2004, the main island more than doubled in size, eventually merging with the nearby Flat Island via an isthmus. These eruptions created new volcanic cones and lava domes, fundamentally altering the geography of the group.

Beyond their geology, the islands serve as a critical ecological sanctuary. Approximately 70 percent of Heard Island is covered by glaciers, and the surrounding waters are protected by a massive marine reserve covering about 380,000 square kilometres. The territory hosts vast populations of penguins and seals, though it has faced modern challenges, including the rapid melting of glaciers due to climate change and the recent confirmation that H5 bird flu has reached the islands. Despite their extreme isolation, the islands remain a site of intense scientific interest, from monitoring volcanic discharge rates to studying the unique isotopic signatures of the local lava series.

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