New Studies Detail Active Rifting Across Eastern and Southern Africa

Two separate studies published in recent weeks provide new data on the tectonic processes occurring within the African continent, detailing thinning crust in the East African Rift System and evidence of active rifting in Zambia.

Turkana Rift Crust Thinner Than Previously Understood

A study published in Nature Communications reports that the crust beneath the Turkana Rift, a 500-kilometer segment of the East African Rift System spanning Kenya and Ethiopia, is significantly thinner than previous estimates.

Seismic data analysis shows the crust at the center of the rift is approximately 13 kilometers thick. In comparison, the crust in the surrounding areas is over 35 kilometers thick. This thinning is described as "necking," a process where the crust stretches and weakens.

The Turkana Rift is considered the first known active continental rift currently undergoing this phase, providing a natural laboratory to study the process.

The study was led by Christian Rowan, a Ph.D. student at Columbia University's Lamont-Doherty Earth Observatory, with co-authors Anne Bécel, Folarin Kolawole, Paul Betka, and John Rowan. Data were collected with industry partners and the Turkana Basin Institute.

The plate separation that drives the rifting began approximately 45 million years ago. The African Plate is splitting into the Nubian and Somali plates at a rate of about 4.7 millimeters per year.

The study's authors note that the necking phase began after widespread volcanism around 4 million years ago, following an earlier failed rifting episode. The full continental breakup and formation of new seafloor, a process known as oceanization, is estimated to take several million more years.

The Turkana Rift is a significant site for ancient human fossils, including the Turkana boy and over 1,200 hominin specimens from the past 4 million years. The study authors propose that the crustal thinning and subsequent subsidence created conditions for rapid accumulation of fine sediments, which are ideal for preserving fossils.

They hypothesize that the region's fossil abundance may reflect these favorable geological conditions rather than the region being a uniquely important center of human evolution.

The authors state this remains a hypothesis for further research.

Helium Isotope Evidence Suggests Active Rifting in Zambia

A separate study, published in Frontiers in Earth Science, provides geochemical evidence suggesting the Kafue Rift in Zambia is an active tectonic boundary. The Kafue Rift is part of a 2,500-kilometer rift system across central Africa, potentially connecting to the Mid-Atlantic Ridge.

Researchers led by geologists at the University of Oxford analyzed gas samples from eight geothermal springs and wells. Six were within the suspected rift zone and two were outside it. Laboratory analysis of the gases from within the rift zone found elevated ratios of helium-3 to helium-4, indicating mantle-derived fluids are reaching the surface.

Samples taken approximately 60 miles away from the suspected rift did not show this signal. Mantle-derived carbon dioxide was also detected in the samples. Recent satellite and seismic data from the region have recorded faint earthquakes, increased underground temperatures, and ground elevation changes.

The authors of the study note that the research is preliminary and based on samples from one area. More extensive studies along the entire proposed boundary are needed to confirm whether the helium signal is continuous. Results from further studies are expected later this year.

If the Kafue Rift is confirmed to be active and developing into a new plate boundary, it could eventually create a new sea in the southern part of Africa, though this process is estimated to take millions of years.

Michael Daly of the University of Oxford, a co-author, noted that the region's basement fabrics are favorably aligned with surrounding mid-ocean ridges, which may lower the threshold for continental break-up.

The findings also suggest potential resources in the region, including geothermal energy, hydrogen, and helium. The study was partly funded by Kalahari GeoEnergy Ltd, a company with interests in geothermal resources.