Larvae or lava? Search for lobster young unearths four volcanoes off Sydney

A cluster of submerged volcanoes has been discovered off Sydney offering the potential to help unlock the secrets of the sea floor between Australia and New Zealand, scientists said Monday. The four extinct volcanoes were found about 250km (150 miles) offshore from Australia’s biggest city last month during a search for larval lobster breeding grounds. Australian National University volcano expert Richard Arculus said the volcanoes, which are spread across 20km, were “a window into the underlying mantle” beneath the seabed. “They tell us part of the story of how New Zealand and Australia separated around 40 to 80 million years ago and they’ll now help scientists target future exploration of the sea floor to unlock the secrets of the Earth’s crust,” he said.

It’s a bit like going through somebody’s garbage bin and determining what they’ve been eating

Volcano expert Richard Arculus

Thought to be about 50 million years old, the volcanoes are at a depth of 4,900m (about 1,600ft), leaving them undetected until now despite the largest being 1.5km across the crater rim and rising 700m from the sea floor. However, a recently commissioned Australian research vessel, the Investigator, is equipped with sonar that can map the sea floor at that depth. “I think every time we turn the spotlight on the sea floor we see things that we’ve never seen before,” Mr Arculus said. “My favourite phrase to people is ‘We know the surface topography of Mars better than we know our backyard’, and that’s because there’s no water in the way.”

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.

Iain Suthers, University of New South Wales

Science sydney volcano