The 50-million-year-old volcano cluster was found by accident about 155 miles (250 km) east of Sydney, but there’s no risk of an eruption.

As reported by the Sydney Morning Herald, the volcanoes were discovered by the CSIRO’s new research vessel, Investigator. Sonar images revealed a cluster of ancient in-line volcanoes that clearly erupted at some point in the past, likely in an explosive manner. The researchers were searching for the area for the nursery grounds of larval lobsters at the time.

The volcanoes are surprisingly large. One measures 1.5 km (1 miles) across and rises 700 meters (2,300 feet) from the sea floor. These volcanoes are now calderas, which form after an eruption and the land around it collapses, forming a crater. The researchers say these volcanoes have been “dead for a long time.”

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Volcano expert Richard Arculus, from the Australian National University, said they were at least 50 million years old and formed near the boundary of an ancient ridge separating two ocean plates.

They had never been discovered before because the sonar on Australia’s previous research vessel, Southern Surveyor, could map the sea floor only to 3000 metres, which left half of Australia’s ocean territory out of reach.

“On board the Investigator we have sonar that can map the sea floor to any depth, so all of Australia’s vast ocean territory is now within reach, and that is enormously exciting,” Professor Arculus said.

Now that scientists know about the cluster, they plan to study the feature to learn more about the geological history of Australia and New Zealand, particularly the nature of the region’s mineral deposits. Further study should also provide information about a deep sea plateau called Lord How Rise which split from Australia about 100 million years ago.

[ SMH ]


Contact the author at george@io9.com and @dvorsky. Top image CSIRO.