A new scientific study helps explain why Bermuda remains elevated in the Atlantic Ocean even after more than 30 million years of volcanic inactivity. Unlike other volcanic islands, which tend to gradually sink after the crust cools, Bermuda appears to have been “supported” by an unusual geological structure located beneath its oceanic crust.
The research was published in the scientific journal Geophysical Research Letters and conducted by a team led by seismologist William Frazer of the Carnegie Science Institute, in partnership with geophysicist Jeffrey Park of Yale University. The results were also detailed in interviews given to specialized media outlets such as Live Science.
Normally, when a volcano becomes extinct, the tectonic plate moves away from the deep hotspot in the Earth’s mantle that fed it. Over time, the crust and the volcano itself cool, become denser, and slowly sink. In Bermuda, however, this process did not occur as expected.
By analyzing seismic waves generated by 396 distant earthquakes—all strong enough to travel across large portions of the planet—researchers were able to map a vertical image of the rocks beneath Bermuda, reaching about 31 miles (approximately 50 kilometers) deep. What they found was a layer of rock about 20 kilometers thick, a type of structure never before observed in any other region of the world.
This layer, less dense than the surrounding rocks, is positioned just below the oceanic crust, within the tectonic plate itself. According to Frazer, this completely deviates from the expected pattern. “But in Bermuda, there is this other layer that is positioned under the crust, within the tectonic plate on which Bermuda sits,” he told the specialized magazine Live Science.
Bermuda is located on an oceanic rise, where the seabed is about 500 meters higher than in neighboring areas. Scientists believe that the last phase of volcanic activity may have forced material from the Earth’s mantle into the crust, where it cooled and became trapped, forming a structure similar to a geological “raft” that supports the island above the ocean floor.
The exact origin of this layer is still a subject of debate. In an interview with the Brighter Side of News website, Jeffrey Park stated that “some of the magma may have been trapped beneath the surface instead of erupting, forming a mafic pluton over time.” He added that “volatile-rich melts rising beneath Bermuda could also have efficiently depleted and modified the upper mantle, leaving behind a lighter residue.”
Another hypothesis raised by the researchers is the so-called metasomatic subplating. In this scenario, the rising hot material would have fractured the crust, allowing seawater to enter and causing partial serpentinization of the mantle, which would also reduce its density.
Although volcanism in Bermuda has been extinct for about 31 million years, there is no evidence of new eruptions on the surface. Even so, the remaining geological structure continues to exert a direct influence on the island’s stability. For geologist Sarah Mazza of Smith College, who did not participate in the study, this legacy is fundamental to understanding the phenomenon. “There is still this remnant material from the days of active volcanism beneath Bermuda that is potentially helping to sustain it as this high-relief area in the Atlantic Ocean,” she told Live Science . She also highlighted the unique geological context of the region: “The fact that we are in an area that was formerly the heart of the last supercontinent is, I believe, part of the story of why this is unique.”
Now, William Frazer intends to expand the research to other islands around the world, searching for similar formations. The goal is to discover if the structure found beneath Bermuda is truly unique or if it might exist in other parts of the planet. “Understanding a place like Bermuda, which is an extreme location, is important for understanding less extreme places and gives us an idea of what the most normal processes that occur on Earth are and what the most extreme processes that occur are,” stated the researcher.
Source: brasil247.com