A team of researchers has identified an unusual layer of rock, more than 20 kilometers thick, beneath the oceanic crust beneath the Bermuda Islands, which could explain why the archipelago appears “to float” over the Atlantic Ocean. This thickness has not been observed before in any other similar place in the world, notes Live Science.
“Usually under the oceanic crust you would expect the mantle to be. But in Bermuda there is this extra layer, placed under the crust, inside the tectonic plate that the archipelago sits on.”explained William Frazer, seismologist at Carnegie Science in Washington DC
The origin of this layer is not yet completely clear, but it may explain the mystery of the ocean wave on which Bermuda sits. “The islands sit on an area where the oceanic crust is higher than the surrounding area, with no current volcanic activity — the last known eruption was 31 million years ago”Frazer added. The study suggests that the last eruption injected mantle rock into the crust, where it solidified, forming a kind of “cork” which raises the ocean floor by about 500 meters.
Geologist Sarah Mazza of Smith College, who was not involved in the study, explained that “there is material left over from the period of active volcanism beneath the Bermuda Islands that probably helps maintain it as a high-altitude area in the Atlantic. The fact that we are in a region that was the core of the last supercontinent makes this a unique phenomenon.”
Frazer and his colleague Jeffrey Park of Yale University used seismic records of distant earthquakes to obtain images up to 50 kilometers deep beneath the Bermuda Islands. Their study, published Nov. 28 in Geophysical Research Letters, found that the rock layer is less dense than the rest of the surrounding rock.
Frazer pointed out that research into this extreme zone is important for understanding the normal and extreme geological processes that occur on Earth. He plans to examine other islands around the world to see if similar layers exist, or if Bermuda is truly unique.
