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Australia hosts planet's longest chain of continental volcanoes

The chain, which stretches from the Great Barrier Reef to Victoria, is nearly three times as long as the track beneath Yellowstone.

By Brooks Hays
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Australia hosts planet's longest chain of continental volcanoes
The chain helped form the volcanic plug, as seen Cape Hillsborough National Park, Queensland. Photo Mike Griinke/ANU

ACTON, Australia, Sept. 15 (UPI) -- The longest continental volcanic chain, or track, is found in Australia. The track's true size wasn't realized until recently, its effects on the landscape limited by the continent's thick upper crust.

The Earth's lithosphere, the crust and upper portions of the mantle, is especially thick Down Under, preventing volcanic activity from dramatically reshaping the landscape.

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While geologists had studied a variety of volcanic structures across Australia, the new study -- published in the journal Nature -- is the first to suggest they were all formed by the same mantle plume, a narrow upwelling of magma sourced deep from within the Earth's mantle near the core.

The chain, which stretches from the Great Barrier Reef to Victoria, is nearly three times as long as the track beneath Yellowstone. Researchers named the volcanic stretch the Cosgrove hotspot track.

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"We realized that the same hotspot had caused volcanoes in the Whitsundays and the central Victoria region, and also some rare features in New South Wales, roughly halfway between them," study author Rhodri Davies, an earth scientist at Australian National University, said in a press release.

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Though the now extinct volcanic chain has been silenced by Australia's thick crust, it was not always so bashful.

While the plume is fixed, the Earth's continental plates are in motion. Some 33 million years ago, the plume worked to form the mountainous Queensland peninsula. But as the planet's Australian Plate shifted northwards, the upward push of the plume's magma was nullified.

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New methods for detecting magmatic activity was key in connecting the dots of the newly discovered track. Researchers confirmed the chain's presence by analyzing the chemical composition of the crust in areas without obvious volcanic activity.

In areas where the crust is just thin enough to allow melting, scientists found a greater presence of leucitite -- a rock-forming mineral composed of potassium, aluminum, uranium and thorium found in low-volume magmas.

"Now that we know there is a direct relationship between the volume and chemical composition of magma and the thickness of the continent, we can go back and interpret the geological record better," said co-author Ian Campbell.

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