A research voyage led by scientists from Australian National University (ANU) has come across what's being called a "lost world" of submerged ancient volcanic seamounts dotting a biologically-rich landscape. Despite some of the mountains rising almost 10,000 feet above the ocean floor, their peaks are still hidden under 1.2 miles of ocean in the South Pacific.

"The seamounts vary in size and shape, with some having sharp peaks while others have wide flat plateaus, dotted with small conical hills that would have been formed by ancient volcanic activity," Dr. Tara Martin, from the CSIRO mapping team, said in a statement. (CSIRO stands for Commonwealth Scientific and Industrial Research Organisation, a research arm of the Australian government.) "Having detailed maps of such areas is important to help us better manage and protect these unique marine environments, and provides a stepping stone for future research."

The previously unknown region was discovered purely by chance during a 25-day mission in the Tasman Sea to study nutrient levels in the East Australian Current. High-resolution sonar mapping the ocean floor picked up the massive underwater formations, with researchers also noticing a spike in phytoplankton activity and marine animal observations in the area.

"While we were over the chain of seamounts, the ship was visited by large numbers of humpback and long-finned pilot whales," said Dr. Eric Woehler, who called the region a biological hotspot. "We estimated that at least 28 individual humpback whales visited us on one day, followed by a pod of 60-80 long-finned pilot whales the next."

The ancient volcanic seamounts are located under more than 16,400 feet of water. The ancient volcanic seamounts are located under more than 16,400 feet of water. (Photo: CSIRO)

While further exploration of the region is already being planned, the researchers nonetheless believe they know how the massive seamounts were formed.

"We're pretty sure that these seamounts were related to the break up of Australia and Antarctica. It was about 30 million years ago," Martin told ABC. "So as Australia and Antarctica and Tasmania all broke up, a big hotspot came in under the earth's crust, made these volcanoes and then helped the earth's crust break so that all of those areas could start to drift apart."

The team plans to return during the summer months of November and December to film the seafloor around the ancient volcanoes with deep-sea, high-definition cameras, and to collect rock samples to learn more about the region's formation.

"We expect that these seamounts will be a biological hotspot year round, and the summer visit will give us another opportunity to uncover the mysteries of the marine life they support," said Woehler.

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

Ancient volcanic 'lost world' discovered deep beneath the Tasman Sea
These volcanic seamounts are rich with life and are estimated to be at least 30 million years old, formed when Australia and Antarctica broke apart.