doi.org/10.1038/s41561-025-01843-9
Credibility: 989
#Christmas Island
Volcanic eruptions in the middle of the oceans may be remnants of supercontinent breakups that reverberate for tens of millions of years after the reorganization of the Earth’s surface, suggests a new study
These eruptions, fueled by instabilities in the Earth’s mantle generated by continental drift, erode the base of the continental crust, releasing material that supplies oceanic volcanoes with a magma of peculiar composition.
This process may explain the existence of underwater mountain ranges, such as the Christmas Island Seamount in the Indian Ocean.
Part of this formation, Christmas Island, emerges above sea level and is known as a natural reserve of lush tropical forests and for the impressive annual migration of millions of red crabs (Gecarcoidea natalis), which cover the island with their shells.
“This discovery reveals a completely new mechanism, which also shapes the composition of the mantle,” said Thomas Gernon, professor of geology at the University of Southampton, UK, and lead author of the study.
The volcanoes of Christmas Island Seamount and other similar submarine formations produce magma with minerals that more closely resemble continental crust than oceanic crust.
Initially, scientists speculated that these volcanoes might be extracting remnants of oceanic crust that, millions of years ago, was subducted into the mantle, carrying coastal sediments from the continents.
Another hypothesis suggested that mantle plumes-upward currents of rock from deep layers-transported ancient continental material back to the surface.
However, the chemical compositions of these magmas are so distinct that a single origin may not explain all cases, as Gernon and his colleagues highlighted in the article published on November 11 in the journal *Nature Geoscience*.
The team proposes a new theory: these volcanoes are fed by continental rocks of different ages and compositions, detached from the bottom of the continents after cataclysmic ruptures.
To investigate, the researchers analyzed volcanic rocks from the Walvis Ridge, an oceanic formation extending from northern Namibia, in Africa.
They observed that older eruptions contained magma with continental characteristics, which, over time, began to exhibit compositions more typical of oceanic rocks.
Using computational models, the team discovered that, after the separation of continents, turbulent waves in the mantle propagate towards the interior of the shifting continent, scraping the continental crust from its base, like a knife peeling the skin of a potato.
This material, enriched with continental minerals, penetrates the mantle a few million years after the rupture and only returns to the surface between 5 and 15 million years later.
According to simulations, the process supplies continental rocks to the mantle for tens of millions of years, with a peak in activity about 50 million years after the separation.
To validate the model, scientists studied volcanic rocks from Christmas Island Seamount.
The results confirmed the predictions: about 116 million years ago, 10 million years after the separation of India from what would become Antarctica and Australia, the first volcanoes in the region began to erupt.
Their magmas were rich in continental minerals, a pattern that peaked between 40 and 60 million years after the breakup, gradually decreasing until resembling the typical magma of oceanic rocks.
The discovery highlights the lasting impacts of continental breakup.
“The mantle still feels the effects of continental breakup long after the continents have separated,” explained Sascha Brune, a geodynamicist at GFZ Potsdam in Germany and co-author of the study.
“The system doesn’t shut down when a new ocean basin forms-the mantle continues to move, reorganizing and transporting enriched material away from its origin.”
Published in 11/15/2025 23h55
Text adapted by AI (Grok) and translated via Google API in the English version. Images from public image libraries or credits in the caption. Information about DOI, author and institution can be found in the body of the article.
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