The mystery of the Bermuda Triangle might not be the most puzzling aspect of the Atlantic.
A new study featured in Geophysical Research Letters suggests that scientists have unraveled the reason behind Bermuda’s survival after its volcano became inactive over 30 million years ago.
Usually, when a volcano stops erupting, tectonic plates drift away from the mantle hotspot, leading the volcano and the cooled crust to gradually sink. But researchers have found something unusual underneath Bermuda’s oceanic crust—a rock formation that appears to be pushing the island upwards.
This intriguing layer is about 19.4 miles thick, which, as it turns out, is a record for similar geological formations around the globe.
A team of seismologists, including William Fraser from the Carnegie College of Science and Jeffrey Park from Yale University, examined seismic waves from 396 distant earthquakes. These waves were strong enough to send vibrations throughout the Earth, allowing the researchers to create a vertical image of rocks extending up to 31 miles underground in Bermuda.
This analysis revealed a thick layer of rock that is less dense than the layers surrounding it.
Fraser mentioned that, typically, one would expect the oceanic crust to lie over the mantle. However, Bermuda has an additional layer beneath the Earth’s crust within the tectonic plate it’s on.
Bermuda resides on an ocean swell, making its crust about 500 meters (1,640 feet) higher than the surrounding ocean floor.
The findings imply that the last volcanic activity might have prompted mantle rocks to push through the Earth’s crust, solidifying and creating raft-like structures on the ocean floor.
The origin of this thick layer isn’t entirely clear. Park pointed out that “Some of the magma may have stagnated beneath the Moho without erupting and formed mafic plutonic bodies over time.”
Additionally, he noted, “We discovered that the volatile-rich melt rising beneath Bermuda might have effectively altered the uppermost mantle, leaving behind a lighter residue. Another possibility is a metamorphic layer where heated upwelling material cracks the crust, allowing seawater to influence parts of the mantle.”
Even after 31 million years without volcanic activity, the ocean swells haven’t diminished, and while there have been no surface eruptions, there is still debate over what’s occurring beneath.
Bermuda seems to retain material from a time of active volcanism, possibly contributing to its prominence in the Atlantic, said Sarah Mazza, a geologist at Smith College in Massachusetts, who wasn’t a part of the study. “I think being in a region that was once the heart of the last supercontinent explains some of Bermuda’s uniqueness.”
Fraser is now exploring other global islands to determine if similar geological formations exist elsewhere or if Bermuda truly stands alone.
He said, “Understanding extreme locations like Bermuda is essential for grasping the more normalized geological processes on Earth.”
