Continents peel from below, triggering oceanic volcanoes
University of Southampton
image:
A piece of the lowermost continental mantle (the crystalline roots of the continents). This represents the material that the research proposes is removed and swept sideways into the oceanic mantle
view moreCredit: Prof Tom Gernon, University of Southampton
Earth scientists have discovered how continents are slowly peeled from beneath, fuelling volcanic activity in an unexpected place: the oceans.
The research, led by the University of Southampton, shows how slivers of continents are slowly stripped from below and swept into the oceanic mantle – the hot, mostly solid layer beneath the ocean floor that slowly flows. Here, the continental material fuels volcanic activity for tens of millions of years.
The discovery solves a long-standing geological mystery: why many ocean islands far from plate tectonic boundaries contain materials that look distinctly continental, despite being found in the middle of oceans.
The study, published in Nature Geoscience, was led by the University of Southampton, and involved the GFZ Helmholtz Centre for Geosciences in Potsdam, Germany, the University of Potsdam, Queen’s University Canada, and Swansea University.
Ancient chemical trails in the mantle
Many ocean islands, such as Christmas Island in the northeast Indian Ocean, contain unusually high levels of certain so-called ‘enriched’ elements that are normally found in continents – possibly because deep Earth processes have folded in older, recycled material, much like a churning cake mixer.
It was thought these elements came from sediments that get recycled when ocean plates dive into the mantle, or by columns of hot rock, known as mantle plumes, which rise from deep within the Earth.
But these explanations fall short, as some volcanic regions show little sign of crustal recycling, while others appear too cool and shallow to be driven by mantle plumes.
“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 lead author of the study. “But we haven’t been able to adequately explain how all that continental material got there.”
The continents are peeling from below
The study proposes a novel answer: continents don’t just rift apart at the surface – they also peel away from below, and over much greater distances than previously thought possible.
The scientists developed simulations to mimic the behaviour of continents and mantle as they are stretched by tectonic forces.
Their work builds on their previous research showing that when continents break apart, deep tectonic forces trigger a wave of instabilities – a ‘mantle wave’ – that sweeps along the continents’ base, disturbing their roots at depths of 150 to 200 km.
This sweeping movement unfolds at an incredibly slow pace, just a millionth the speed of a snail, gradually stripping material from the deep roots of continents.
These peeled fragments are then swept sideways – sometimes over more than 1,000 km – into the oceanic mantle, where they feed volcanic eruptions in the ocean over tens of millions of years.
Study co-author Professor Sascha Brune, of GFZ in Potsdam, said: “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, reorganising, and transporting enriched material far from where it originated.”
Evidence from the Indian Ocean
The team analysed geochemical data from areas of the Earth including the Indian Ocean Seamount Province, a chain of volcanic features formed after the supercontinent Gondwana broke apart over 100 million years ago.
Through simulations and chemical analysis, they discovered that soon after Gondwana broke apart, a burst of unusually enriched magma rose to the surface.
Over tens of millions of years, that chemical signal faded as the flow of material from beneath the continent waned. This happened without a mantle plume coming from deep in the Earth, which geologists had long assumed must be responsible.
Professor Gernon explained: “We’re not ruling out mantle plumes, but this discovery points to a completely new mechanism that also shapes the composition of the Earth’s mantle. Mantle waves can carry blobs of continental material far into the oceanic mantle, leaving behind a chemical signature that endures long after the continents have broken apart.”
The study builds on the team’s recent discovery that mantle waves can also stir dramatic changes deep within continents. Their earlier work showed that these slow, rolling movements in the Earth’s mantle can help trigger diamond eruptions and even reshape landscapes thousands of kilometres from the edges of tectonic plates.
ENDS
Journal
Nature Geoscience
Article Publication Date
11-Nov-2025
Where does continental material on islands come from?
Continents are scraped from below. The material feeds volcanoes in the ocean.
image:
A microscopic image of a fragment of the lowermost continental mantle — the crystalline roots of the continents. This is the type of material that the authors propose is stripped away and laterally transported into the oceanic mantle. Photo: Prof Tom Gernon (University of Southampton).
view moreCredit: Prof Tom Gernon (University of Southampton).
Many oceanic islands far from active plate tectonic boundaries contain materials that clearly originate from continents, even though they are located in the middle of an oceanic plate. Where do the continental remnants come from? Are they sediments that are recycled when oceanic plates subduct into the mantle? Or do they originate from the depths of the Earth's mantle and are carried upward by hot currents, known as mantle plumes? Both explanations are being discussed, but they fall short. This is because some volcanic regions show little evidence of crustal recycling, while others are too cool to be driven by mantle plumes.
Researchers at the University of Southampton and the GFZ Helmholtz Centre for Geosciences have now proposed a new explanation. Geochemical analyses and modelling have revealed the following picture: When continents break apart, a wave of instability is created at a depth of more than a hundred kilometres. This “mantle wave” scrapes material from the underside of the continents along the base, which is then transported sideways into the Earth's mantle beneath the oceans.
There, these remnants of continental roots feed volcanic eruptions in the ocean crust over millions of years. Sometimes the material travels more than a thousand kilometres from the continental interiors before it forms oceanic islands.
Professor Sascha Brune from GFZ in Potsdam and co-author of the study, says: “We have found that the mantle continues to ‘feel’ the effects of continental rifting long after the continents have separated. The system does not shut down when a new ocean basin forms—the mantle continues to move, reorganize, and transport enriched material far away from its place of origin.”
The team analyzed geochemical data from various regions of the Earth, including the Seamount Province in the Indian Ocean, a chain of volcanic formations that formed after the breakup of the supercontinent Gondwana over 100 million years ago.
Through simulations and chemical analyses, the team discovered that shortly after Gondwana broke apart, unusually enriched material with a continental fingerprint appeared beneath the new-born ocean and generated melts that can now be found at oceanic islands and submerged seamounts. Over millions of years, this chemical signal faded as the flow of material from the interior of the continent slowed.
This happened without there having been a mantle plume. Thomas Gernon, Professor of Earth Science at the University of Southampton and lead author of the study, says: "We are not ruling out mantle plumes, but our discovery points to a completely new mechanism that also influences the composition of the Earth's mantle. Mantle waves can transport continental material far into the oceanic mantle, leaving behind a chemical signature that persists long after the continents have broken apart."
The study builds on the team's recent discovery that “mantle waves” can also cause dramatic changes deep within continents. Their previous work showed that these slow, rolling motions in the Earth's mantle can help trigger diamond eruptions and even reshape landscapes thousands of kilometres away from the edges of tectonic plates.
The study, published in Nature Geoscience, was led by the University of Southampton and conducted in collaboration with the GFZ Helmholtz Centre for Geosciences in Potsdam, the University of Potsdam, Queen's University Canada, and Swansea University.
Original study: Thomas Gernon et al.: Enriched mantle generated through persistent convective erosion of continental roots; in: Nature Geoscience https://doi.org/10.1038/s41561-025-01843-9
Journal
Nature Geoscience
Method of Research
Computational simulation/modeling
Subject of Research
Not applicable
Article Title
Enriched mantle generated through persistent convective erosion of continental roots
Article Publication Date
11-Nov-2025
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