Macquarie Island is a rare piece of Earth's mantle pushed above the ocean surface

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

In short: Located halfway between Tasmania and Antarctica, this subantarctic island is a geological anomaly. It is the only place on Earth where rocks from the mantle are actively exposed above sea level, having been squeezed upward like toothpaste from a tube along a tectonic plate boundary.

Discovered by Frederick Hasselborough in 1810, Macquarie Island has a history defined by isolation and environmental struggle. Though once considered for a penal settlement, the island's harsh conditions and extreme weather—characterised by relentless winds and frequent cloud cover—ultimately made it unsuitable for human habitation. Instead, it became a site of intense resource extraction, where seals and penguins were hunted for oil until the early 20th century, nearly driving local populations to extinction.

Geologically, the island is a rare ophiolite, a section of oceanic crust and upper mantle uplifted by tectonic forces. Scientists believe the island emerged above the waves as recently as 80,000 to 300,000 years ago. It sits on the Macquarie Ridge, where the Australian and Pacific plates meet. This ongoing tectonic activity causes the island to rise at a rate of 0.1 to 0.5 centimetres per year, a process that has shaped its dramatic landscape of plateaus, steep cliffs, and pillow basalts.

The island's ecology has faced severe disruption from introduced species. After feral cats were eradicated by 2000 to protect seabirds, the rabbit population surged, leading to widespread vegetation loss and soil erosion. This environmental damage has been a subject of scientific debate, particularly regarding the complex interactions between introduced predators, disease, and native flora. Today, the island is a UNESCO World Heritage Site, valued for its unique geoconservation significance and its role as a critical breeding ground for millions of seabirds, including the entire royal penguin population.

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