Oceanographers find underwater mountain bigger than Mount Olympus

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Imagine four skyscrapers the height of Burj Khalifa, the world’s tallest building, stacked on top of one another.

That’s almost the height of an underwater mountain newly discovered and mapped by oceanographers led by the Schmidt Ocean Institute in California.

Located in the Pacific Ocean 900 miles (1,448 kilometers) off the coast of Chile, the seamount is 1.9 miles (3,109 meters) tall and part of an underwater mountain range that is home to sponge gardens, ancient corals and rare marine species — including a type of squid that was filmed for the first time.

A team led by the Schmidt Ocean Institute explored the region using the R/V Falkor (too) research vessel during a 28-day expedition that wrapped up this month. The researchers mapped the mountain using a sonar system under the ship’s hull.

“Sound waves go down and they bounce back off the surface, and we measure the time it takes to come back and get measured. From that we get a really good idea (of the seabed topography),” said Jyotika Virmani, the institute’s executive director.

“It’s important because at the moment only about 26% of the seafloor has been mapped to this kind of resolution. And the seafloor covers 71% of our planet’s surface.”

Oceanographers estimate that there are at least 100,000 seamounts higher than 1,000 meters (3,280 feet) around the world. They provide important habitats for a variety of species. The newly mapped underwater mountain is bigger than Mount Olympus in Greece, which is 2,917 meters (9,570 feet) high; smaller than Japan’s Mount Fuji, which stands 3,776 meters (12,388 feet) tall; and almost quadruple the 830-meter (2,723-foot) height of Burj Khalifa, the Dubai tower.

Spaghetti monsters, a ghostly octopus and a rare squid

Using an underwater robot, the team explored one of the mountain’s ridges, finding a region rich in marine biodiversity.

The researchers documented a ghostly white Casper octopus, marking the first time this deep-dwelling cephalopod has been seen in the southern Pacific. They also spotted two rare Bathyphysa siphonophores, sometimes known as flying spaghetti monsters for their stringlike appearance.

“The (Casper) octopus has never been captured, so it doesn’t actually have a scientific name yet,” Virmani said.

The team also recorded the first footage of a live Promachoteuthis squid, known only from a few collected specimens.

The discoveries were highlights of the research vessel’s third expedition this year to the Nazca Ridge, which is in international waters. The region could be a contender for the world’s first high seas marine protected area under a new UN treaty adopted in 2023 that is being ratified by states, Virmani said.

“Across the three expeditions, we managed to map and explore 25 seamounts, which is quite a number to explore,” she said. “I think we’ve got some good data as a community that could be put forward to make the case that this is a really interesting region for protection.”

The two previous expeditions in January and February cataloged 150 previously unknown species. An additional 20 potential news species were collected during the most recent expedition.

Details of the newly discovered species will be shared with the Ocean Census, an ambitious international collaboration to record marine life hidden in the world’s oceans. It aims to identify 100,000 unknown species in the next 10 years, allowing scientists to better understand and protect the deep-sea ecosystem.