Seismic study reveals giant hidden rock raft beneath Bermuda

A new seismic study has revealed a giant, hidden rock layer beneath Bermuda, a finding scientists describe as unlike anything previously documented on Earth. The layer is about 12.4 miles (20 kilometers) thick and sits under the island's ocean crust, where it appears to be contributing to Bermuda's raised position above the surrounding seafloor by roughly 500 meters (1,640 feet).

Researchers traced distant earthquakes as their seismic waves moved through the crust beneath Bermuda, using data from a local seismic station. By noting where the waves unexpectedly changed direction, the team identified a thick patch of less-dense rock emplaced within the tectonic plate that Bermuda sits on, effectively forming a subterranean raft. The findings were published in Geophysical Research Letters. 'Typically, you have the bottom of the oceanic crust and then it would be expected to be the mantle,' said Dr. William Frazer, a seismologist at Carnegie Science. 'But in Bermuda, there is this other layer that is emplaced beneath the crust, within the tectonic plate that Bermuda sits on.'

Geologists say the discovery could be a major step toward solving Bermuda's biggest mystery: why its oceanic swell remains so high without recent volcanic activity. Bermuda has not erupted in more than 31 million years, so a volcanic hotspot does not explain the island’s uplift. The less-dense rock raft, by deflecting passing seismic waves and buoying the crust upward, helps account for the sustained elevation. Earlier work on Bermuda showed ancient lava that is unusually low in silicon, implying a mantle-derived origin from deep within the Earth, a heritage tied to the opening of the Atlantic during the breakup of the supercontinent Pangea about 900 to 300 million years ago. That legacy could help explain why Bermuda sits on a distinct crustal structure, unlike other hotspot islands in the Pacific or Indian oceans. The researchers say they plan to scan other islands to see whether similar layers exist or whether Bermuda is an exception.

Beyond the Bermuda Triangle lore, scientists say the row of shipwrecks and disappearances may be better explained by natural ocean dynamics. Oceanographer Dr. Simon Boxall of the University of Southampton said rogue waves—extreme, steep waves that can reach 30 meters (about 100 feet)—could explain many incidents attributed to the Triangle, especially when ships encounter a sudden, towering wall of water. While the Triangle remains a focus of popular speculation, experts emphasize that the latest geological findings address Bermuda's unique crustal architecture rather than unexplained disappearances.

Looking ahead, the team is examining other islands to see whether a similar subterranean structure exists. If such layers prove common, it would reshape understanding of crustal formation and oceanic swell formation; if Bermuda remains unique, it would underscore how exceptional combinations of mantle history and tectonic processes can create regionally distinct geologies.