Turkana Rift: Thinning Crust Accelerates Africa’s Continental Split

The crust within the Turkana Rift is thinning at a faster rate than previously estimated, according to a study published in Nature Communications. Researchers from Columbia University’s Lamont-Doherty Earth Observatory found the crust has thinned to 13 kilometers in some areas, signaling an advanced stage of continental breakup along the East African Rift System.

How fast is the African continent splitting?

The African Plate and the Somali Plate are moving apart at a rate of approximately 4.7 millimeters per year, according to the Nature Communications report. This slow separation creates fractures in the Earth’s crust, allowing magma to rise from the mantle and trigger volcanic activity across the region.

Christian Rowan, a PhD student at Columbia University’s Lamont-Doherty Earth Observatory and the study’s lead author, stated that rifting in this zone is more advanced than previously recognized. He noted that Eastern Africa has progressed further in the rifting process than scientists once thought.

What causes the crust to thin so dramatically?

Researchers attribute the thinning to a geological process called “necking.” This occurs when the crust stretches and narrows, similar to how a piece of pulled taffy behaves under tension. As the material thins, it weakens, which makes further stretching easier and increases the likelihood of a total split.

The disparity in crustal thickness is stark. High-resolution seismic data reveals that the crust along the rift’s center is only 13 kilometers thick in certain places. In contrast, the crust outside the rift zone remains more than 35 kilometers thick.

Anne Bécel, a geophysicist at Lamont-Doherty and co-author of the study, said the region has reached a “critical threshold of crustal breakdown,” which explains why the area is more prone to separate.

When will the ocean flood the Turkana Rift?

While the crustal breakdown is significant, the process remains slow. The Turkana Rift began forming roughly 45 million years ago. According to the research team, it will likely take several million more years before the region enters its next evolutionary stage.

The next phase involves the formation of new oceanic crust. Once this occurs, seawater will eventually flood into the rift, effectively turning the valley into a new sea and fully separating the Somali Plate from the main African continent.

How does tectonic thinning preserve early human fossils?

The geological instability of the region directly contributed to its status as a paleoanthropological goldmine. The Turkana Basin holds more than 1,200 hominin fossils dating back four million years, representing about one-third of all such discoveries in Africa.

The researchers suggest that widespread volcanic activity and subsequent crustal thinning caused the land to subside about four million years ago. This subsidence created deep basins where fine-grained sediments accumulated quickly.

These rapid sediment deposits created the ideal conditions for preserving bones and other organic remains, protecting them from erosion and scavengers over millions of years.

Comparison of Crustal Thickness

Frequently Asked Questions

Is the African continent splitting right now?
Yes, the African and Somali plates are separating at about 4.7 millimeters per year, according to data from Columbia University.

Will this cause immediate earthquakes or disasters?
The process is geologically slow. While rifting involves seismic activity, the total separation of the continent will take several million more years.

Why is the Turkana Basin so important for human history?
Because tectonic subsidence created basins that trapped sediments, preserving a third of Africa’s known hominin fossils, according to the study.

What do you think about the Earth’s changing geography? Does the idea of a new ocean forming in Africa surprise you? Let us know in the comments below or subscribe to our newsletter for more deep-dives into planetary science.