Tectonic action is splitting Africa apart to produce a new ocean, according to University of Southampton scientists who have investigated unusual pulses emanating from beneath the continent that are driving surface volcanism.
Far below the surface, molten rock in the Earth’s mantle in Ethiopia’s Afar region is rhythmically pulsing upwards, driven by tectonic plates above. When those tectonic plates stretch over millions of years, they eventually crack to produce a new ocean basin.
“We found that the mantle beneath Afar is not uniform or stationary – it pulses, and these pulses carry distinct chemical signatures,” said lead author Dr Emma Watts. “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.”
The Afar Region
Volatility in the Afar region comes from the convergence of three tectonic plates: the Arabian, the Nubian, and the Somalian. In turn, where these plates join, they create three currently active rifts: the Main Ethiopian Rift, the Red Sea Rift, and the Gulf of Aden Rift, which have been affecting tectonics and volcanism for millions of years.
Under this trio of rifts, geologists have hypothesized that a plume resides, involving an upsurge of molten rock from the mantle that places pressure on the nearby tectonic plates.
The region is particularly useful in studying plumes, as many are located undersea, adding an additional layer of challenge to collecting samples and observations. Of those beneath dry land, even fewer are correlated to ongoing continental rifting.
The team’s work doubled the amount of high-quality rock analyses from the area, covering many volcanoes that had never before been studied. The new work provides insight into the structure and behavior of the plume for the first time.
Investigating Africa’s Tectonics
For their study, the team utilized existing data, statistical models, and original rock samples from young volcanoes collected from Afar and the Main Ethiopian Rift.
With the rifts first becoming active across spans ranging from 11 to 35 million years ago, the researchers decided that younger rocks below about 2.5 million years old were an important focus to enable the most direct comparison. From these pieces, they investigated the structure and melt of the area’s crust and mantle.
Their findings indicate that a single asymmetric plume lies beneath the rifts, evidenced in the composition of volcanic rocks. Within the plume, specific repeating chemical bonds sit at a spacing determined by each rift arm’s unique tectonic conditions.
“The chemical striping suggests the plume is pulsing, like a heartbeat,” said co-author Tom Gernon, Professor of Earth Science at the University of Southampton. “These pulses appear to behave differently depending on the thickness of the plate and the rate at which 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,” Gernon added.
Layered Interactions
Intriguingly, the plume appears to be dynamically responding to the tectonic plates above. This creates a situation where there is a single plume, yet its behavior is asymmetrical, driven by the conditions above a particular channel through which a portion of it flows.
More quickly expanding arms generated longer wavelengths, suggesting that thinner plates and higher rifting rates are creating more rapid mantle flow channels—especially toward the Red Sea Rift—which is spreading at a rapid pace. Intriguingly, as the rifts continue to separate, they are progressing toward varying stages that include ocean formation, proto-oceanic formation, and mature continental rifting.
“We have found that the evolution of deep mantle upwellings is intimately tied to the motion of the plates above. This has profound implications for how we interpret surface volcanism, earthquake activity, and the process of continental breakup,” said co-author Dr Derek Keir, Associate Professor in Earth Science at the University of Southampton and the University of Florence.
“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,” Keir added. “Follow on research includes understanding how and at what rate mantle flow occurs beneath plates.”
Overall, the research team’s work highlights the complex geological processes at play in the region, as well as their cascading long-term effects.
“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 new paper, “Mantle Upwelling at Afar Triple Junction Shaped by Overriding Plate Dynamics,” appeared on June 25, 2025, in Nature Geoscience.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.