Scientists have discovered an extraordinary geological anomaly beneath the island of Bermuda: a 12.4-mile (20-kilometer) thick rock layer embedded within the Earth’s oceanic crust. This structure is unlike any other found globally, challenging current understanding of how oceanic swells form and persist. The discovery sheds light on why Bermuda remains elevated above its surroundings despite being volcanically inactive for over 31 million years.
The Mystery of Bermuda’s Elevation
For decades, the Bermuda oceanic swell has puzzled geologists. Unlike island chains such as Hawaii, which are maintained by active mantle hotspots, Bermuda shows no recent volcanic activity. Typical swells subside as tectonic plates move away from these hotspots, but Bermuda’s elevation persists – a phenomenon now potentially explained by this newly identified subsurface layer.
The structure appears to be a remnant of ancient volcanism, with mantle rock frozen beneath the crust, acting as a buoyant base that keeps the island elevated by roughly 1,640 feet (500 meters). Seismological data revealed the layer’s presence: researchers analyzed seismic wave patterns from distant earthquakes to create a detailed image of the Earth’s subsurface down to 31 miles (50 km).
Ancient Origins in Pangea
The unusual composition of the rock further deepens the mystery. Analyses reveal low silica content and high carbon levels, suggesting the material originated from deep within the mantle – potentially dating back to the formation of the supercontinent Pangea between 900 million and 300 million years ago. This differs sharply from hotspot islands in the Pacific or Indian oceans, where mantle plumes are younger and more recent.
The Atlantic Ocean, being a relatively young basin formed during Pangea’s breakup, may have preserved this ancient geological signature. The presence of this deep carbon source suggests that the region was once at the heart of the last supercontinent, which explains why Bermuda’s geology is so unique.
Implications and Future Research
The discovery has far-reaching implications for understanding Earth’s internal processes. By studying extreme locations like Bermuda, scientists can refine their models of how more typical geological features develop and evolve. William Frazer, the study’s lead author, is now investigating other islands worldwide to determine if similar subsurface structures exist, or whether Bermuda truly stands alone as a geological outlier.
“Understanding a place like Bermuda…gives us a sense of what are the more normal processes that happen on Earth and what are the more extreme processes that happen.”
The finding underscores how much remains unknown about our planet’s interior, and suggests that deep subsurface anomalies may play a more significant role in shaping surface geology than previously thought.
