🦴 Africa 'splits in two' and reveals abundant human remains

The Turkana Rift (or East African Rift) in East Africa is famous for its human fossils and volcanic activity. But a recent discovery exceeds our expectations: the Earth's crust there is much thinner than previously thought, signaling an advanced continental breakup. This geological process could even explain why the region preserves such a rich fossil record.

Beneath the Turkana Rift, the Earth's crust thins dramatically: at the heart of the zone, it is only 13 kilometers (about 8 miles) thick, compared to more than 35 kilometers (about 22 miles) in the surrounding area. This contrast marks a key stage called "necking," where the crust narrows like stretched caramel. This weakness favors the continued separation of tectonic plates.


Christian Rowan and his team analyzed seismic data, collected with industrial partners and the Turkana Basin Institute, to measure this thinning. By tracking sound waves through underground layers, they mapped sedimentary structures and determined the depth of the crust. The result confirms that the rifting process is more advanced than previously assumed.

The "necking" began about 4 million years ago, after intense volcanic eruptions. As the crust thinned, it subsided, creating a basin where fine sediments accumulated rapidly. These sediments are perfect for preserving fossils, which could explain the site's richness: more than 1,200 hominin fossils have been discovered there, one-third of all those found in Africa.

These findings challenge the idea that the Turkana Rift was a single center of human evolution. Perhaps it simply offered favorable geological conditions for preserving remains. "The conditions were right to preserve a continuous fossil record," explains Rowan. Other researchers will be able to test this hypothesis using these data.

The Turkana Rift is the first active rift observed in the necking phase. It offers a rare opportunity to study a decisive stage of plate tectonics. These processes influence climate, vegetation, and environments. "We have a front-row seat to observe a stage that shaped all the rift margins of the world," adds Folarin Kolawole.

The complete evolution of the rift will take millions more years. After necking comes oceanization, where magma creates new ocean floor, and perhaps the waters of the Indian Ocean will invade the region. But this knowledge already helps reconstruct the history of Earth and its inhabitants.