Research ship finds ancient volcanoes off Sydney coast

In a week where a volcano has inconvenienced many, here’s a seismic discovery that has roundly delighted.

The research ship Investigator accidentally mapped the seafloor around 250km off the coast of Sydney – and found four deep-sea extinct volcanos, thought to be at least 50 million years old.

The 5km deep cluster - with one of its peaks rises 700m from the seafloor - is a valuable find for vulcanologists.

“These guys, they’re like looking through somebody’s garbage bin, and it’s the composition of these volcanoes, the lava’s on the seafloor, that tells us what used to be below this part of the world,” Professor Richard Arculus, from the Australian National University, told 9NEWS.

The vessel was searching for fish living in deep sea eddies when it came upon the find.