Scientists discovered four 50 million-year-old extinct volcanoes off the coast of Sydney, Australia using a groundbreaking research vessel. 

The fascinating objects were stumbled upon during a hunt for nursery grounds for larval lobsters, the University of New South Wales reported. The research vessel that discovered the volcanoes routinely mapping the seafloor, allowing it to spot strange features. The largest volcano proved to be about 5,000 feet high.

"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," said UNSW Australia marine biologist Professor Iain Suthers.

The volcanoes are calderas, which form when an eruption causes the land around them to collapse and form a crater.

"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," said Professor Richard Arculus from the Australian National University. "They haven't been found before now because the sonar on the previous Marine National Facility (MNF) research vessel, Southern Surveyor, could only map the sea floor to 3,000 [meters], which left half of Australia's ocean territory out of reach. On board the new MNF vessel, 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."

The ship allows scientists to send and receive data while out at sea so researchers back on shore can analyze the data and share their results. This is the first time the researchers will be able to directly respond the changing dynamics of the ocean. The vessel also allowed the scientists to chase eddies as they formed.

"It was astounding to find juvenile commercial fish species like bream and tailor 150 [kilometers] offshore, as we had thought that once they were swept out to sea that was end of them. But in fact these eddies are nursery grounds along the east coast of Australia," Suthers said.