A team of Earth scientists has discovered that continents are slowly peeling apart from below—sending fragments deep into the oceanic mantle, where they can spark volcanic eruptions thousands of kilometers away.
The finding, led by researchers from the University of Southampton and published in Nature Geoscience, solves a long-standing puzzle: why some volcanic islands in the middle of the oceans contain chemical traces of continental rock, even though they are far from any continental edges or tectonic plate boundaries.
Many volcanic islands, like Christmas Island in the Indian Ocean, contain elements that are normally found in continental crust rather than oceanic rock.
Until now, scientists thought these “enriched” materials came from sediments recycled when ocean plates sank into the mantle, or from columns of rising hot rock known as mantle plumes.
But these explanations didn’t fit all the evidence—especially in places where there’s no sign of deep recycling or plume activity.
“We’ve known for decades that parts of the mantle beneath the oceans look strangely contaminated, as if pieces of ancient continents somehow ended up there,” said Professor Thomas Gernon, lead author of the study.
“But we didn’t know how those fragments got there in the first place.”
The team’s new model offers a striking answer: continents don’t just split apart at the surface—they also peel away from below, like layers coming off an onion. As continents stretch and rift due to tectonic forces, their deep “roots,” located around 150 to 200 kilometers underground, are slowly destabilized.
Using computer simulations, the researchers found that these deep layers can form slow-moving mantle waves—rolling movements in the Earth’s interior that gradually strip fragments from the underside of continents. These pieces are then swept sideways into the mantle beneath the oceans at an incredibly slow rate—just a millionth the speed of a snail.
Over millions of years, these drifting fragments travel more than 1,000 kilometers, eventually melting and feeding volcanic eruptions on the ocean floor. The process can continue for tens of millions of years after the continents themselves have drifted apart.
“We found that the mantle is still feeling the effects of continental breakup long after the continents themselves have separated,” said Professor Sascha Brune from the GFZ Helmholtz Center for Geosciences in Germany. “The system doesn’t just switch off—it keeps moving and recycling material far from where it began.”
To test their theory, the researchers examined volcanic rocks from the Indian Ocean Seamount Province, formed after the breakup of the ancient supercontinent Gondwana more than 100 million years ago. These rocks showed signs of enriched material that could only have come from continental roots—without any evidence of a mantle plume.
According to Gernon, the discovery adds a new layer to our understanding of how Earth works: “Mantle waves can carry pieces of continents far beneath the oceans, leaving chemical fingerprints that last for millions of years. It’s a hidden process that helps shape both continents and ocean volcanoes.”
