Scientific research from Bermuda has helped to inform a revelatory study of the island’s unusual geological foundations that hit the headlines after the study was published in November.

William Frazer, a seismologist at Carnegie Science in Washington and the lead author of the study, told the news website Live Science that an unexpected slab of rock almost 13 miles thick had been discovered underpinning the Earth’s crust below Bermuda.

Unusually thick and composed of lighter rock than its surroundings, the intrusion lifts the island high above its sunken surroundings.

Dr Frazer said: “Typically, you have the bottom of the oceanic crust, and then it would be expected to be the mantle.”

The mantle refers to the hot layer of rock underlying the external crust, which is the planet’s outer shell, broken into tectonic plates.

Dr Frazer told the site: “But in Bermuda, there is this other layer that is emplaced beneath the crust, within the tectonic plate that Bermuda sits on.”

Dr Frazer, who met scientists in Bermuda as part of the study, published the findings in the journalGeophysical Research Letters with Jeffrey Park, a professor of Earth and planetary sciences at Yale University.

The deep-lying rock is far beyond direct reach, but can be studied using seismological data collected in Bermuda that gives a picture of geological structures beneath the surface.

Bermuda’s volcanic origins are fairly unique compared with islands such as Hawaii, known to scientists at hotspots.

The submarine volcano far below the limestone sedimentary rock of Bermuda’s surface has been dormant for 31 million years. Its volcanic igneous rock starts on average about 150 feet below the present-day sea level.

Usually a hot plume rises from Earth’s mantle to push up volcanic islands and seamounts.

Because Bermuda shows no evidence of such a plume, or any recent volcanism, the island’s origins have presented a challenge to scientists.

The island and its surrounding seamounts such as the Challenger and Argus Banks sit on a 1,500-kilometre “swell” in the crust that has not subsided, despite the long period of inactivity.

The article suggested that the massive body of rock beneath Bermuda was forced up against the crust by one of the last bouts of volcanic activity tens of millions of years ago.

Researchers used seismic recordings obtained from Bermuda to get a picture of the geology far below the island.

Tremors from far-off earthquakes give a description of the structures they pass through — in this case, revealing a giant slab of rock that is “lighter”, or less dense, than its surroundings.

The Frazer and Park publication said the massive body of rock had not previously been reported.

The story was widely picked up by international media, including an article in the Daily Mail likening the geological mystery to the story of the Bermuda Triangle.

Martin Brewer, a former geology professor at Bermuda College and a seismologist, welcomed the paper, telling The Royal Gazette: “It’s very interesting. It explains why the swell exists — there’s no plume because there’s no heat coming out of the mantle. No heat, no hotspot.

“The rock is slightly lighter than the mantle below but thick enough to lift the island.” The phenomenon is known as isostasy, Dr Brewer added.

“Like a ship, the crust, or rather the lithosphere, sits on the mantle, which over a long period of time acts like a liquid. This thick rock right under the island causes this buoyancy.

“I’m glad to see this has been resolved, and with local data from the Bermuda Institute of Ocean Sciences.”