University of Southampton researchers have uncovered a groundbreaking geological process where continents are slowly peeled from beneath, with the stripped material traveling over 1,000 km to fuel volcanic activity in the middle of oceans. The discovery, led by Professor Thomas Gernon, explains the long-standing mystery of why ocean islands far from tectonic boundaries contain continental material.
The study, published in Nature Geoscience, reveals that deep “mantle waves” triggered by continental breakup can strip slivers from a continent’s base at depths of 150 to 200 km. This material is then swept sideways into the oceanic mantle, where it feeds volcanoes for tens of millions of years. The research involved collaboration with the GFZ Helmholtz Centre for Geosciences in Potsdam, the University of Potsdam, Queen’s University Canada, and Swansea University.
For decades, geologists have been puzzled by the presence of distinctly continental elements on remote ocean islands like Christmas Island in the northeast Indian Ocean. These ‘enriched’ elements were thought to come from recycled ocean sediments or deep mantle plumes, but these explanations often fell short.
“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 Professor Thomas Gernon, Professor of Earth Science at the University of Southampton. “But we haven’t been able to adequately explain how all that continental material got there.”
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The team’s novel answer involves a process of deep peeling. When continents rift apart, tectonic forces trigger a wave of instabilities—a ‘mantle wave’—that sweeps along the continent’s base. This movement, unfolding at a pace a millionth the speed of a snail, gradually strips material from the deep roots of continents. “We found that the mantle is still feeling the effects of continental breakup long after the continents themselves have separated,” stated study co-author Professor Sascha Brune, of GFZ in Potsdam.
“The system doesn’t switch off when a new ocean basin forms – the mantle keeps moving, reorganising, and transporting enriched material far from where it originated.”
To test their theory, the scientists analyzed the Indian Ocean Seamount Province, a volcanic chain formed after the supercontinent Gondwana broke apart over 100 million years ago.
Their simulations and chemical analysis revealed a burst of enriched magma soon after the breakup, which faded over millions of years as the supply of peeled continental material waned. This pattern occurred without the need for a deep mantle plume, challenging a long-held geological assumption.
This discovery points to a completely new mechanism that shapes the composition of the Earth’s mantle. The process of deep peeling not only explains enigmatic ocean volcanoes but also builds on the team’s previous work showing that these same mantle waves can trigger diamond eruptions and reshape landscapes thousands of kilometers from plate boundaries. It seems the Earth’s interior is far more dynamic and interconnected than we ever imagined.
