Hamilton, Bermuda – The Bermuda archipelago, known for its stunning beaches and the legendary Bermuda Triangle, has long puzzled scientists with its geological composition. Recent research by seismologists William Frazer from Carnegie Science and Jeffrey Park of Yale University sheds new light on why these islands sit atop a bulge of the Earth’s crust that defies conventional geological understanding.
Bermuda comprises 181 islands, a formation stemming from volcanic activity approximately 33 million years ago. Typically, volcanic island chains like Hawaii are characterized by a sequence of active and inactive volcanoes, accompanied by a mantle plume—a rising column of hot material from the Earth’s interior that helps form these structures. However, the islands of Bermuda present a conundrum: there is no active volcanic activity in the area, nor is there evidence of a mantle plume that generally underpins such geological formations.
Frazer and Park’s investigation involved analyzing seismic waves generated by earthquakes as they traveled through the Earth’s mantle beneath Bermuda. These waves behave differently depending on the density of the materials they encounter, allowing researchers to glean insights about the subterranean structures.
Their findings revealed a 20-kilometer-thick layer of relatively low-density rock beneath Bermuda’s oceanic crust. This rock layer appears to be providing the buoyancy typically expected from a mantle plume, effectively supporting the geological swell that keeps the islands above sea level. “We have identified features associated with this thick layer that have not been reported before,” they stated in their research.
The presence of this underplated layer suggests that it was formed during Bermuda’s volcanic phase, which occurred around 30 to 35 million years ago. It plays a critical role in maintaining the islands’ elevation in the face of potential erosion and sea level rise. Without the support of this underlayer, experts believe the archipelago could gradually sink into the Atlantic.
While the seismic data provides a compelling explanation, it remains just one hypothesis among several potential models. The researchers emphasize that understanding this geological phenomenon could have wider implications for the study of other volcanic islands and their vulnerabilities to environmental changes.
The findings, published in the journal Geophysical Research Letters, not only answer some longstanding questions about Bermuda’s formation but also highlight the complex interplay between geological forces and the stability of landmasses in ocean-heavy regions. As climate change continues to rise, the future of islands like Bermuda may hinge on the mysteries hidden beneath their surfaces.