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Slow 'Mantle Waves' Peel Continental Roots — Why Distant Oceanic Volcanoes Carry Continental Chemistry

Researchers propose that slow, rolling "mantle waves" beneath rifting continents can peel continental roots and carry fragments into the oceanic mantle. This process explains why some oceanic volcanoes show continental chemistry far from continental margins and can sustain enriched volcanism for tens of millions of years. Evidence from an Indian Ocean volcanic chain linked to Gondwana's breakup supports the model, which may also trigger diamond-rich magmas and uplift continental interiors.

01:21 PM, 11/23/2025Science
Slow 'Mantle Waves' Peel Continental Roots — Why Distant Oceanic Volcanoes Carry Continental Chemistry

Geoscientists report a new explanation for why some oceanic volcanoes carry unmistakable continental chemical signatures despite being far from continental margins. Using computer simulations and chemical analyses, researchers show that slow, rolling flows in the upper mantle — described as "mantle waves" — can shear material from continental roots and carry those fragments deep into the oceanic mantle.

How mantle waves work

When continental plates rift and begin to move apart, the hot, very slowly moving upper mantle becomes unstable beneath the lithosphere. Those instabilities propagate as mantle waves along depths of roughly 150–200 km (90–125 miles). As the waves sweep beneath continental margins, they can strip or peel continental material from the base of the continents and transport those fragments more than 1,000 km into the oceanic mantle.

Evidence and timescales

Simulations and geochemical data indicate the stripped continental material mixes into the oceanic mantle, enriching melts and sustaining volcanism for tens of millions of years. The transport is extremely slow on human timescales — the authors note it operates over millions of years — but the chemical fingerprints persist long after the continents have separated.

We have known that parts of the mantle beneath the oceans look contaminated, as if pieces of ancient continents ended up there. The mantle keeps moving and reorganizing long after a new ocean basin forms. — Thomas Gernon, University of Southampton

A tested example comes from an offshore chain in the Indian Ocean that includes Christmas Island. Once adjacent to northeastern Australia during the breakup of Gondwana more than 150 million years ago, this volcanic chain shows an early pulse of enriched volcanism within ~50 million years of rifting, then a gradual decline — a pattern consistent with the mantle-wave model and without strong evidence for classic plume activity.

Broader implications

Beyond explaining remote continental signatures in oceanic volcanism, the researchers suggest two additional consequences: mantle waves may mobilize diamond-bearing magmas from deep sources, and the slow flow can drive uplift of continental interiors by more than a kilometer, helping to form major topographic features.

The findings are based on integrated geodynamic modeling and geochemical analyses and are published in Nature Geoscience. Key contributors include Thomas Gernon (University of Southampton) and Sascha Brune (University of Potsdam).

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