These pulses are gradually tearing the African continent apart and forming a new ocean basin, according to a study led by University of Southampton researchers.
Variation in geochemical and geophysical properties around the Afar Triangle. Image credit: Watts et al., doi: 10.1038/s41561-025-01717-0.
The Afar region is a rare place on Earth where three tectonic rifts converge: the Main Ethiopian Rift, the Red Sea Rift, and the Gulf of Aden Rift.
Geologists have long suspected that a hot upwelling of mantle, sometimes referred to as a plume, lies beneath the region, helping to drive the extension of the crust and the birth of a future ocean basin.
But until now, little was known about the structure of this upwelling, or how it behaves beneath rifting plates.
“We found that the mantle beneath Afar is not uniform or stationary — it pulses, and these pulses carry distinct chemical signatures,” said Dr. Emma Watts, who conducted the research at the University of Southampton and is now based at Swansea University.
“These ascending pulses of partially molten mantle are channelled by the rifting plates above.”
“That’s important for how we think about the interaction between Earth’s interior and its surface.”
Dr. Watts and colleagues collected more than 130 volcanic rock samples from across the Afar region and the Main Ethiopian Rift.
They used these, plus existing data and advanced statistical modeling, to investigate the structure of the crust and mantle, as well as the melts that it contains.
Their results show that underneath the Afar region is a single, asymmetric plume, with distinct chemical bands that repeat across the rift system, like geological barcodes.
These patterns vary in spacing depending on the tectonic conditions in each rift arm.
“The chemical striping suggests the plume is pulsing, like a heartbeat,” said University of Southampton’s Professor Tom Gernon.
“These pulses appear to behave differently depending on the thickness of the plate, and how fast it’s pulling apart.”
“In faster-spreading rifts like the Red Sea, the pulses travel more efficiently and regularly like a pulse through a narrow artery.”
The findings show that the mantle plume beneath the Afar region is not static, but dynamic and responsive to the tectonic plate above it.
“We have found that the evolution of deep mantle upwellings is intimately tied to the motion of the plates above,” said Dr. Derek Keir, a researcher at the University of Southampton and the University of Florence.
“This has profound implications for how we interpret surface volcanism, earthquake activity, and the process of continental breakup.”
“The work shows that deep mantle upwellings can flow beneath the base of tectonic plates and help to focus volcanic activity to where the tectonic plate is thinnest.”
“Follow on research includes understanding how and at what rate mantle flow occurs beneath plates.”
“Working with researchers with different expertise across institutions, as we did for this project, is essential to unravelling the processes that happen under Earth’s surface and relate it to recent volcanism,” Dr. Watts said.
“Without using a variety of techniques, it is hard to see the full picture, like putting a puzzle together when you don’t have all the pieces.”
The study was published in the journal Nature Geoscience.
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E.J. Watts et al. Mantle upwelling at Afar triple junction shaped by overriding plate dynamics. Nat. Geosci, published online June 25, 2025; doi: 10.1038/s41561-025-01717-0