Researchers have discovered that continents are slowly stripped from below by mantle waves, feeding volcanic activity in distant oceans. This process explains continental chemical signatures in remote ocean islands. The findings, published in Nature Geoscience, challenge traditional views on mantle dynamics.
Earth scientists from the University of Southampton and international collaborators have revealed a hidden geological process where continents peel away from their deep roots, contributing to volcanic eruptions far into the oceans.
The study, published in Nature Geoscience, shows that when continents break apart due to tectonic forces, a slow-moving 'mantle wave' forms at depths of 150 to 200 kilometers. This wave travels along the base of the continents, stripping fragments of continental material and carrying them sideways for more than 1,000 kilometers into the oceanic mantle. The process occurs at a rate roughly a millionth the speed of a snail and can sustain volcanic activity for tens of millions of years.
"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 in there," said Thomas Gernon, Professor of Earth Science at the University of Southampton and the study's lead author. "But we haven't been able to adequately explain how all that continental material got there."
To validate their model, the team analyzed data from the Indian Ocean Seamount Province, which formed after the breakup of the supercontinent Gondwana over 100 million years ago. They found that soon after the split, magma rich in continental elements erupted to the surface, with the signature fading over time. This occurred without evidence of deep mantle plumes, suggesting the peeling mechanism as a key driver.
Professor Sascha Brune of GFZ Helmholtz Centre for Geosciences in Potsdam added, "We found that the mantle is still feeling the effects of continental breakup long after the continents themselves have separated. The system doesn't switch off when a new ocean basin forms—the mantle keeps moving, reorganizing, and transporting enriched material far from where it originated."
The discovery resolves why ocean islands like Christmas Island in the northeast Indian Ocean show high concentrations of enriched continental elements, despite being far from plate boundaries. It builds on prior research linking mantle waves to inland effects like diamond eruptions.