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Earth's continents may look fixed on a globe, but they've been drifting, splitting and reforming over billions of years—and they still are. Our reveals fresh evidence of rhythmic pulses of molten rock rising beneath east Africa, reshaping our understanding of how continents break apart.

Our findings could help scientists understand more about volcanic activity and earthquakes.

There are around . Active volcanoes are those thought to have had an eruption over the last 12,000 years or so. Of these volcanoes, lie on the —the seam along which Africa is splitting apart. This weak seam of crust may even allow a to form over the next few million years.

Although ocean formation is happening around the world, and has been for several billion years, there are few places on Earth where you can study different stages of continental breakup at the same time. This is because they normally become as Earth's crust thins, and seawater eventually inundates the rift valley.

The Rift Valley is different. There is, at its northern end (in Ethiopia) a place called . These are called the Red Sea Rift, the Gulf of Aden Rift, and the Main Ethiopian Rift.

The Red Sea Rift has been spreading for the last , and the Main Ethiopian Rift for the last . There are across all three of these rifts. In Afar, all three rifts are at least partly exposed, with the Red Sea Rift and Main Ethiopian Rift having the most exposure.

Volcanic rocks that erupt when Earth's tectonic plates spread apart provide a window into the inner Earth that wouldn't otherwise be accessible. Each lava flow and volcano has its that is recorded in the rock and we can learn about that through geochemistry—the concentrations of the elements that make up the rock—and mineralogy—the minerals within the rock.

Analyzing these things can tell us about the depth at which the melting rock formed and roughly where in Earth's mantle it formed. In our new study, we analyzed over 130 new lava samples, obtained from at the University of Pisa and our own fieldwork.

We used these samples to investigate the characteristics of the mantle beneath this rifting, when tectonic plates are moving apart from each other. These samples are from eruptions (rocks younger than 11.7 thousand years old) from across Afar and the East African Rift.

Since the 1970s, that there is a mantle plume beneath the Afar region. are a portion of abnormally hot mantle (around 1,450°C) or unusual composition of the mantle (or both) below Earth's surface. Scientists think it pushed some of the mantle to Earth's surface. Our study not only confirms the presence of a mantle plume in this region, but also gives scientists details about its characteristics.

We discovered that the mantle plume beneath the region rises beneath the tectonic plates in pulses, and the pulses have slightly different chemical compositions.

There are mantle plumes around the world. They can be identified in the geological record as far back as . Each of the plumes has different characteristics—with their own unique chemical composition and shape.

One mantle plume still active today is the one lying below the Hawaiian islands. These islands are part of the Hawaiian Emperor chain, formed over the , and are still forming today. The islands originate from the Pacific tectonic plate slowly moving across the top of a mantle plume, making lava bubble up, erupt and eventually solidify as rock.

This plume melts Earth's mantle and forms magma, which over long periods results in the formation of an island chain or breaks up continents. It can also form volcanoes along a rift in Earth's crust, as we see in east Africa. The Hawaiian plume signature comes from two chemical compositions rising up through the mantle together like two vertical strands.

While scientists have long thought there probably is a plume underneath Afar, .

In our study, we created several scenarios of what the plume looks like and then used mathematical modeling to see which plume scenario best fit the sample data. Using this data-driven approach, we show that the most likely scenario is a singular plume that pulses with different chemical compositions.

The three rifts in Afar are spreading at different rates. The Red Sea Rift and Gulf of Aden Rift are moving faster (that's half the rate your fingernails grow at) compared to the Main Ethiopian Rift moving . We deduced that the pulses are flowing at different speeds along the stretched and thinner undersides of the tectonic plates.

All this shows us that the motion of tectonic plates can help focus volcanic activity to where the plate is thinner.

This finding has important implications for how we interpret volcanic and earthquake activity. It may indicate that volcanism could be more likely to occur in the faster spreading and thinner portions of the rift, as the flow beneath replenishes the magma more frequently.

However, the eruptions here may be less explosive than the slower spreading rifts. This fits that explosive eruptions occur more frequently in the Main Ethiopian Rift (which sits on a thicker part of the plate and where the volcanoes are more mature), compared to the Red Sea Rift.

Our understanding of the link between continental rifting and mantle plumes is still in its infancy but research is already providing insights into how tectonic plates affect mantle plumes and how this might be recorded in the future seafloors of Earth.

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