Ancient underwater volcanoes have been discovered near Sydney

The Investigator's map of the previously unknown volcanoes on the sea floor. (Image credit: Marine National Facility) .
The Investigator research vessel’s map of the four previously unknown volcanoes; you can clearly see their bowl-like depressions. (Image: Marine National Facility) .



When Professor Iain Suthers and his team set sail on the Investigator research vessel on the 3rd of June this year, they were anticipating a 15 day voyage to search for sites where lobster larvae hatch and grow. Along the way they would be mapping the sea floor as a matter of routine; the new and state-of-the-art Investigator can record the sea floor at any depth, unlike its predecessor which could only ‘see’ 3km beneath the surface. The team’s mission was a success and they found the lobster nurseries they were searching for. What they didn’t expect was to discover four ancient volcanoes that until now have been completely unknown.

The sea floor in that area, approximately 250km off the eastern coast of Australia, was believed to be completely flat but the Investigator research vessel’s enhanced capabilities have shown otherwise. The four volcanoes are a type known as calderas, because their structure resembles a cauldron; this happens when a volcano forms but collapses in on itself. The largest of the group is 1.5km across and rises 700m from the sea floor. The whole group is measures about 20km long and 6km wide, and is almost 5km below the ocean’s surface.

The location of the four ancient volcanoes, 250km from Australia's east coast.
The location of the four ancient volcanoes, 250km from Australia’s east coast.


The volcanoes are thought to be about 50 million year old, and are thought to have been created when Australia and New Zealand’s tectonic plates separated. New Zealand has a number of active volcanoes but Australia’s last eruption is thought to have occurred about 5,000 years ago. Scientists hope that these calderas will teach us more about the Earth’s crust and how that part of the world was formed. As volcano expert Richard Arculus has said, “We know the surface topography of Mars better than we know our backyard because there’s no water in the way. I think every time we turn the spotlight on the sea floor we see things that we’ve never seen before”.

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