Australian Mountains Are Still Growing, Cave Rocks Reveal

Australia is typically portrayed as an old and docile continent with little to no geological activity, but new research shows the isolated land of kangaroos remains geologically active — with several mountains still jutting up into the sky, according to a study from the University of Melbourne.

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Australia's mountains are growing strong

The study shows how parts of the Eastern Highlands of Victoria — which includes popular skiing venues like Mount Buller and Mount Baw Baw — might be only five million years old, instead of 90 million years as previously thought.

John Engel — one of the four scientists at the Isotope Geochemistry Group in the School of Earth Sciences who studied stalactites, stalagmites, and flowstones in the area — went spelunking in the nearby Buchan Caves to develop their findings.

"At least 250 meters of additional height in the East Victorian Highlands appears to have been gained in the last few million years," said Mr. Engel.

With help from Parks Victoria Rangers the team worked in 10 caves, and climbed down through ominous passages so tight they had to crawl and even squeeze through to collect the small fragments of speleothem "rubble" to bring to the laboratory. Once retrieved, the cave rubble was examined with radiometric U-Pb dating to establish geologic age.

"Our research shows a clear trend between oldest speleothem (cave age) and height in the landscape," said Engel. "The data suggests that the Buchan region has been steadily uplifting at a rate of 76 meters (roughly 250 feet) every million years, beginning at least 3.5 million years ago and continuing today. This means that some speleothems have been sitting in dark caves undisturbed for 3.5 million years."

Young geology in East Victoria Highlands

Evidence from the echoing caves suggests these Highlands initially rose from sea level roughly 90 million years ago — when the Tasman Sea between New Zealand and Australia opened.

Researchers think the cause of the more recent rise in mountain height is still debated, but a prime theory signals a friendly rivalry between New Zealand and Australia.

"The Australian and Pacific plates share a common boundary and many of the forces involved at this boundary may be propagated into the Australian plate as tectonic stress. Some of this tectonically-induced stress is then released as uplift of the mountains in South East Australia," added Engel.

"This is why East Gippsland may still feel effects related to these tectonic forces. This subtle modification of classical plate tectonic theory can help explain the frequent, small earthquakes observed along South East Australia."

Unearthing the history of mountain creation

Engel noted that while familiar mountains like the Himalaya and the Swiss Alps are beloved for their looks, unearthing the hidden stories surrounding how and when mountains come into being gives a deeper insight and sense of appreciation for something highly researched in the scientific field of geology.

"Our research showcases a new — and rather unique — method for measuring the uplift of mountains. This technique of using speleothem is likely to also work in other caves across the world for regions with 'recent' tectonic activity, offering geologists great opportunities to share more stories about these impressive and unchanging features of our landscape."

Continents like Australia and Antarctica are typically treated like quiet, idle geological sites — but with active volcanoes in the latter, and the recent discovery in the caves of Australia, we're learning that no matter where on Earth we go, the ground beneath our feet a short drop away from a wild shifting world of active tectonics.