The Earth beneath east Africa is pulsing, ready to bring forth a new ocean, according to scientists.
In a new study, published in the journal Nature Geoscience, researchers have shown that molten rock from the Earth’s mantle is throbbing towards the surface in Afar, Ethiopia, in an upwelling known as a plume. As it rises, the continent is being torn apart and, eventually, a new ocean basin will appear.
The study’s findings show that the behaviour of this plume is affected by the hugechunks of the Earth’s crust – known as tectonic plates – above it.
“We found that the mantle beneath Afar is not uniform or stationary – it pulses, and these pulses carry distinct chemical signatures,” says lead author Dr Emma Watts in a statement. Currently a research officer at Swansea University, Watts was at the University of Southampton when she undertook the study.
The paper describes Afar as “a classic triple junction” of three tectonic rifts: the Main Ethiopian Rift, the Red Sea Rift, and the Gulf of Aden Rift. At each of these rifts, tectonic plates are being pulled apart.
"These ascending pulses of partially molten mantle are channelled by the rifting plates above,” Watts says. “That’s important for how we think about the interaction between Earth’s interior and its surface.”
The geography of the region affects the behaviour of these plumes. “The plume is pulsing, like a heartbeat,” says 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 how fast it’s pulling apart,” he says: “In faster-spreading rifts like the Red Sea, the pulses travel more efficiently and regularly like a pulse through a narrow artery.”
It takes millions of years for tectonic plates to separate. When they finally tear free of each other, a new ocean basin forms.
The exact size and form of this new ocean is currently unknown. “At the present rate, a sea about the size of the current Red Sea might form in about 2030 million years,” Ken Macdonald, a professor at the University of California, Santa Barbara (UCSB), told Earth.com.
To find out more about how the upwelling of molten rock affects the creation of this new ocean basin, the researchers used over 130 volcanic rock samples along with existing data and statistical modelling, to explore the structure of the Earth’s crust and mantle in Afar. Their findings suggest that below this region, there is one asymmetric plume with distinct, repeating bands that they compare to “geological barcodes.”
These new insights into the close relationship between upwellings, rifts and shifting tectonic plates could help experts understand other geological phenomena, like earthquakes and volcanoes. “We have found that the evolution of deep mantle upwellings is intimately tied to the motion of the plates above,” says co-author Dr Derek Keir, associate professor of Earth science 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,” he adds.
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Top image: Active lava flows spilling out of the Erta Ale volcano in Afar, Ethiopia. Credit: Dr Derek Keir, University of Southampton/ University of Florence
