Aus scientists discover huge and ancient underwater volcanoes

A cluster of submerged volcanoes, thought to be about 50 million years old, have been discovered around 250 kilometres off the coast of Sydney by a team of Australian scientists who were looking for lobster larvae.
The four huge underwater volcanoes were spotted through sonar mapping of the sea floor by Australia's new ocean-going research vessel Investigator last month during a search for the nursery grounds of larval lobsters.
"The voyage was enormously successful, not only did we discover a cluster of volcanoes on Sydney's doorstep, we were amazed to find that an eddy off Sydney was a hotspot for lobster larvae at a time of the year when we were not expecting them," chief scientist for the voyage Iain Suthers said.

The four extinct volcanoes in the cluster are calderas, which form after a volcano erupts and the land around them collapses, forming a crater with the largest 1.5 km across the rim and it rises 700 metres from the sea floor. The cluster is believed to be 50 million years old.
Australian National University's Richard Arculus, who is a world-leading expert on volcanoes, said these types of volcanoes are windows into the seafloor.
"They tell us part of the story of how New Zealand and Australia separated around 40 to 80 million years ago," he said, adding that "They'll now help scientists target future exploration of the sea floor to unlock the secrets of the Earth's crust."

"Previous seafloor mapping has only been possible in depths up to 3,000 metres, but the Investigator can map the seafloor at any depth. Arculus said the capability means that all of Australia's ocean territory was now in reach.