Carnegie Science researchers have discovered a hidden layer of rock more than 12 miles thick sitting just below Bermuda's oceanic crust. This buoyant "underplate" may explain why Bermuda still rises roughly 1,600 feet above the surrounding seafloor more than 30 million years after its last volcanic eruption — a mystery that has puzzled geologists for decades.
The finding challenges the classic mantle plume theory that explains most volcanic island chains like Hawai'i. Unlike Hawai'i, Bermuda shows no evidence of an active mantle plume beneath it today. The researchers believe the underplate formed during Bermuda's volcanic past when carbon-rich molten rock rose from the mantle, pushed into the base of the crust, and cooled there — creating a thick, permanently buoyant layer.
In February 2026, the team deployed 10 portable seismometers across Bermuda to collect more data. If confirmed as a broader geological process, underplates could reshape our understanding of how volcanic islands form and persist.