A giant structure found deep beneath Bermuda is unlike anything else on Earth

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Move aside, the Bermuda Triangle: The newest North Atlantic mystery lies beneath this mysterious archipelago. Scientists have discovered a unique, 12.4-mile-thick (20 km) layer of rock beneath the oceanic crust under Bermuda. This level of thickness has never been seen in any other similar layer around the world.

“Typically, you have the bottom of the oceanic crust and then you would expect it to be mantled,” said the study’s lead author. William Fraser“But in Bermuda, there’s this other layer that sits beneath the crust, within the tectonic plate that Bermuda sits on,” said a seismologist at Carnegie Science in Washington, DC.

Although the origin of this layer is not entirely clear, it could explain an ongoing mystery about Bermuda, Fraser told Live Science. The island sits on a seafloor, where the oceanic crust is higher than its surroundings. But there’s no evidence of any ongoing volcanic activity fueling that eruption—the island’s last known volcanic eruption was 31 million years ago.

The discovery of a new giant “structure” suggests that the last eruption may have injected mantle rock into the crust, where it froze, creating something like a raft that lifts the ocean floor about 1,640 feet (500 meters).

Bermuda has long had a reputation for mystery, mainly due to the Bermuda Triangle, an area between the archipelago, Florida and Puerto Rico where an unusual number of ships and planes have reportedly gone missing. (However, it has reputation Hugely exaggerated.) The real mystery, though, is why the Bermuda ocean bloom exists.

Island chains like Hawaii are thought to exist because of mantle hotspots, which are places in the mantle where hot matter rises, creating volcanic activity. At the point where the hotspot meets the crust, the ocean floor often rises. But when tectonic movement moves the crust away from that hotspot, ocean blooms typically subside.

Despite 31 million years of volcanic inactivity, Bermuda’s swelling hasn’t subsided, Fraser said. There is some debate about what is happening in the mantle beneath the island, but there have been no surface eruptions.

Fraser and study co-authors Geoffrey ParkA professor of earth and planetary sciences at Yale University used recordings from a seismic station in Bermuda of large earthquakes from around the world to get an image of the Earth about 31 miles (50 km) below Bermuda. They examined the places where the seismic waves from these earthquakes changed abruptly. It revealed an unusually thick layer of rock, which is less thick than the other rock around it.

Their findings were published Nov. 28 in the journal Geophysical Research Papers.

“There’s still this material left over from days of active volcanism under Bermuda that is potentially helping to hold it up as an area of ​​high relief in the Atlantic Ocean.” all the funA geologist at Smith College in Massachusetts who was not involved in the work told Live Science.

Mazza’s own research into Bermuda’s volcanic history found that there are lava types low in the mineral silica, indicating they come from high-carbon rocks. Mazza’s test of variations in zinc molecules in samples from Bermuda, published in the journal September GeologyIt was found that this carbon came from deep in the mantle. It was probably first pushed there when the supercontinent Pangea formed between 900 million and 300 million years ago, Mazza said. This is different from what is seen on hotspot-formed islands in the Pacific or Indian Oceans, he added. This difference may be because the Atlantic, which opened up when Pangea split, is a young ocean compared to the Pacific or Indian Oceans, which flanked Pangea.

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“We’re in an area that was once the heart of the last supercontinent, which, I think, is part of the story of why it’s unique,” she said.

Fraser is now examining other islands around the world to see if there are any similar layers found beneath Bermuda or if the archipelago is truly one of a kind.

“Understanding a place like Bermuda, which is an extreme place, is important for understanding less extreme places,” Fraser said, “and gives us a sense of what are the normal processes on Earth and what are the more extreme processes.”