Scientists have found the Earth’s crust beneath East Africa’s Turkana Rift is only 13 kilometers thick along its axis, far thinner than the surrounding areas where it exceeds 35 kilometers.
This dramatic thinning indicates the region is undergoing “necking,” a critical phase in continental rifting where the crust stretches and weakens in the middle, making a future split more likely.
The discovery, published in Nature Communications, suggests eastern Africa is further along in the breakup process than previously understood, with the African and Somali plates drifting apart at about 4.7 millimeters per year.
How the crust thinning was measured
Researchers analyzed high-quality seismic data collected with industry partners and the Turkana Basin Institute, examining how sound waves traveled through underground layers to map sediment structures and determine crust depth.
The team combined seismic imaging with other methods to reveal the stark contrast between the thinned rift axis and the thicker crust flanking it, a signature of active necking.
Why this changes views on human fossil preservation
The same tectonic forces thinning the crust may have created ideal conditions for fossil preservation in the Turkana Basin, offering a new perspective on why the region holds such a rich record of early human remains.
Instead of being solely the birthplace of humanity, Turkana may have simply been where geological conditions best preserved the story, as rifting created low-lying basins that accumulated sediments and fossils over millions of years.
What this means for Africa’s future
While the changes unfold over immense timescales, reaching this necking threshold suggests the continent is primed for eventual breakup, potentially forming a new ocean basin millions of years from now.
The last time similar necking led to ocean formation was during the opening of the Atlantic Ocean, when rifting between Africa and South America reached a comparable stage before full separation.
What is necking in geological terms?
Necking describes how the crust stretches and thins in the middle during rifting, similar to the narrowed point that forms when a piece of taffy is pulled apart, making it weaker and more prone to continued splitting.
How fast are the African and Somali plates moving apart?
In the Turkana region, the African and Somali plates are drifting apart at a rate of about 4.7 millimeters per year.