An active volcano under glaciers creates ecosystems at the ice-steam interface. Thermophilic bacteria live in ice caves warmed by volcanic heat on one of Earth's most remote islands.
Astronaut photograph ISS018-E-38182 was acquired on February 28, 2009, with a Nikon D2Xs digital camera fitted with an 800 mm lens, and is provided by the ISS Crew Earth Observations experiment and the Image Science & Analysis Laboratory, Johnson Space Center. The image was taken by the Expedition 18 crew. The image in this article has been cropped and enhanced to improve contrast. Lens artifacts have been removed. The International Space Station Program supports the laboratory to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption William L. Stefanov, NASA-JSC., Public domain, via Wikimedia Commons
A land of fire and ice
Heard Island is an external territory of Australia located in the Southern Ocean, approximately 4,000 kilometers southwest of Perth. The island is dominated by Big Ben, a massive active stratovolcano that is about 25 kilometers in diameter. Its highest point, Mawson Peak, rises to 2,745 meters (9,006 feet) above sea level, making it the highest mountain in any Australian state or territory outside of the Australian Antarctic Territory. The volcano has been active for about one million years, with eruptions recorded since 1881 and as recently as 2016.
Roughly 70 percent of Heard Island is covered by permanent snow and ice. The volcanic cone of Big Ben has 14 major glaciers that flow from the summit toward the sea. This permanent ice cover, combined with ongoing volcanic activity, creates a rare natural laboratory. Geothermal heat from the volcano melts the base of the glaciers, forming a network of subglacial caves and fumaroles. These ice caves are environments where liquid water, volcanic gases, and geothermally-warmed rock coexist, creating conditions found almost nowhere else on Earth.
Warm caves and hidden life
The interaction between volcanic steam and glacial ice creates unique, warm micro-environments. While outside temperatures are sub-Antarctic, temperatures inside these geothermally heated ice caves can be surprisingly mild. Similar volcanic cave systems on Mount Erebus in Antarctica have recorded temperatures as high as 25 degrees Celsius (77 degrees Fahrenheit).
These dark, moist environments on Heard Island are believed to have chemosynthetic ecosystems. These ecosystems are not dependent on sunlight for energy. Instead, microorganisms derive energy from chemical reactions, metabolizing sulfur and other compounds released in volcanic gases. While direct biological sampling of Heard Island's ice caves is extremely limited due to the island's remoteness and protected status, studies of analogous volcanic cave systems in Antarctica have revealed the DNA of diverse bacteria and fungi. Some DNA sequences discovered in these caves do not match any known species, suggesting the potential for undiscovered life forms uniquely adapted to this subglacial volcanic world. The conditions on Heard Island show how life might exist in extreme environments, both on Earth and potentially on other planets.
💡Fun Facts
Heard Island and its neighbor, McDonald Island, are the only two active volcanic areas in Australian territory.
The island is one of the most remote places on Earth, situated about 1,700 kilometers from Antarctica and 4,100 kilometers from mainland Australia.
The glaciers on Heard Island are retreating rapidly, with their total area shrinking by 20 percent between 1947 and 2008.
The island is a UNESCO World Heritage site, recognized for its pristine ecosystem, which has an almost complete absence of non-native species.
Access is restricted to scientific expeditions with a permit from the Australian Antarctic Division. There is no tourism.
Admission
Not applicable.
Accessibility
The island is uninhabited and extremely remote. Access is by ice-strengthened expedition ship only, a journey that takes approximately two weeks from Australia.
