A new plate boundary could be emerging beneath southeastern Africa – a deep break in the Earth’s crust. Geologists found evidence of this when analyzing hot springs in Zambia. The isotopes detected in the fluids suggest that the rift that is forming extends down into the Earth’s mantle. In the long term, this could create a new rift valley in southeastern Africa – perhaps even a separate continent, as the team reports.
A huge rift runs through Africa: The East African Rift stretches thousands of kilometers from the Ethiopian Afar Depression in the north to Mozambique in the south. The deep rift valley, lined with countless volcanoes, reveals that the African continent is gradually breaking apart at this point. In the distant future, a new sea could perhaps even emerge there – similar to the Red Sea millions of years ago.
A rift from Tanzania to Namibia
But East Africa is not the only region of Africa where the earth’s crust is breaking up: geologists led by Ruta Karolyte from the University of Oxford have discovered evidence that a new rift is also forming in the south of the continent. The impetus for their study was an approximately 2,500 kilometer long topographic zone that stretches from Tanzania to Namibia. It has long been noticeable due to an accumulation of faults, hot springs and geothermal anomalies – possible symptoms of a rift.
To test this, Karolyte and her team examined a part of this potential rift zone in Zambia. To do this, they took fluid samples from six geothermal sources in this so-called Kafue Rift and examined the isotope ratios of the helium and carbon contained therein. They compared these values with those from two geothermal sources outside the Kafue zone and with values from the East African Rift Valley.
Broken up into the earth’s mantle
The analyzes revealed: The samples from the potential rift zone in Zambia contain increased levels of the helium isotope 4He and also abnormalities in the carbon isotopes. However, this was not evident in the two control samples. “The helium isotope signatures suggest that the hot springs in the Kafue Rift have a direct connection to the Earth’s mantle,” explains co-author Mike Daly from the University of Oxford. This is also supported by similarities in the helium and carbon values with younger areas of the East African Rift Valley.
Accordingly, the earth’s crust in southern Africa could have already torn up into the mantle. According to geologists, this suggests that the African plate is beginning to break apart along the potential rift zone. “The fluid connection proves that the Kafue Rift faults are active and therefore the Southwest African Rift Zone,” says Daly. “This could be an early sign of a rupture in sub-Saharan Africa.”
Is a new continent break emerging?
But what does this mean for the tectonic future of the African continent? Is it losing its southern tip? Not necessarily: “A rift can become a plate boundary,” explains Karolyte. “But often the activity of a rift zone stops before the lithosphere has completely broken up and the plate boundary is formed.” In the East African Rift Valley, for example, the two edges move apart very slowly because they receive counterpressure from neighboring mid-ocean ridges.
“But this could be different for the Southwest African Rift System,” explains Daly. “This is because it has all the characteristics of a rift zone and a weakened crust, but is more favorably located in relation to the surrounding mid-ocean ridges. This could mean that there could be a lower threshold for a continental breakup there.”
However, the researchers also emphasize that further investigations are necessary to clearly demonstrate this new fracture zone. “Our study is based on just a small section of the Southwest African Rift, which is thousands of kilometers long,” says Daly. The team is already working on a more extensive study that is expected to be completed this year.
Source: Ruta Karolyte (University of Oxford) et al., Frontiers in Earth Science, 2026; doi: 10.3389/feart.2026.1799564