This discovery has important implications for our understanding of how oceanic plates and islands evolve. Photo credit: Rumidesigns/Shutterstock
Scientists have discovered an unusually thick and mysterious layer of rock deep under the sea in Bermuda. This discovery challenges traditional geological models. This layer is about 20 kilometers thick, much larger than the typical layer beneath the oceanic crust that geologists would normally expect to encounter directly in the Earth’s mantle.
The study was led by Carnegie Science seismologist William Fraser and Yale University’s Jeffrey Park. Their team analyzed seismic waves from hundreds of distant earthquakes recorded by instruments in Bermuda and other locations. Changes in the speed and direction of these waves allowed them to create images of the Earth’s subsurface beneath the archipelago, revealing previously unknown geological formations.
Under typical conditions, the oceanic crust transitions directly into the mantle, the region of the Earth below the crust that is made up of dense rock. But in Bermuda, there is a thick intermediate layer embedded within the tectonic plates themselves that is not found in similar ocean basins elsewhere.
The mystery of Bermuda’s raised seabed
Understand why islands remain elevated without active volcanic activity
Bermuda sits on a large area of raised ocean floor roughly 500 meters above the surrounding ocean floor, which geologists call an ocean swell. Such undulations are usually associated with active volcanic hotspots, where plumes of hot mantle rock rise and push up the Earth’s crust.
What makes Bermuda unusual is that there is no evidence of active volcanic activity beneath it. The last known volcanic activity in the area occurred about 31 million years ago, and scientists had expected the Earth’s crust to cool and sink since then. Still, the swell continues, a geological mystery that has intrigued researchers for years. A newly discovered rock layer may help solve this mystery. The material in this layer is less dense than the surrounding mantle, so it acts like a buoyant slab supporting the upper crust. In fact, the thick layer may help maintain Bermuda’s altitude even in the absence of ongoing volcanic activity.
Possible origins of hidden layers
How was this unusual structure formed?
The formation of this thick underground structure is still not fully explained, but scientists have proposed several hypotheses based on seismic evidence and rock chemistry. One idea is that during Bermuda’s early volcanic period, not all of the magma reached the surface. Some of this molten material may have stagnated and solidified deep within the Earth’s crust, forming thick rock bodies. Another possibility includes serpentinization, a process in which seawater penetrates deep into the mantle through cracks and reacts chemically with mantle rocks to produce hydrated, less dense minerals. This may have altered the original rock and contributed to its buoyancy.
Evidence also comes from the composition of Bermuda’s own volcanic rocks. These rocks contain high levels of carbon and other trace elements, indicating a deep mantle origin. Some researchers link these features to geological processes that date back to the breakup of the supercontinent Pangea, which began more than 200 million years ago.
Implications for geological research
What this discovery means for earth science
This discovery has important implications for our understanding of how oceanic plates and islands evolve. The discovery of similar thick, low-density layers beneath other oceanic islands could prompt a re-evaluation of the crustal structure and crust-mantle interaction models used by geologists around the world.
But Bermuda may still be unique. A combination of geological history, volcanic origins, and tectonic movements led to the formation of a structure unlike anything previously recorded. Researchers are already examining seismic data from other swells to see if comparable underplate features exist elsewhere.
Important points:
- Scientists have identified a previously unknown 20-kilometre-thick geological structure beneath the Bermuda Islands that differs from normal oceanic crust.
- This layer is located between the crust and the mantle within a tectonic plate, rather than a typical transition zone.
- Its low density and thickness may help explain why Bermuda’s sea floor remains high even though volcanic activity has long ceased.
- Possible formation mechanisms include trapped volcanic magma, chemical changes due to hydration (serpentinization), and deep mantle processes.
- The discovery challenges current understanding of ocean geological structure and could change the way scientists view tectonic movements.
Beyond myth: the real mysteries of the ocean floor
Scientific discoveries, not paranormal legends
Bermuda has long been associated with myths such as the Bermuda Triangle, but the scientific discovery of this hidden rock formation presents a well-founded mystery rooted in Earth’s geology rather than folklore. Modern seismic imaging can peer deep into the ocean floor, revealing structures that were once completely invisible.
The study highlights the region’s complex geological history and highlights that even the best-studied parts of Earth can hold surprises. Far from being explained by supernatural speculation, Bermuda’s raised ocean floor appears to be supported by concrete physical structures deep beneath the waves.
