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New research led by 911½ñÈÕºÚÁÏ has overturned a long-standing assumption about how continents split apart.

The research showed that thinned tectonic plates associated with failed rifts can actually make the Earth’s tectonic plates stronger and more resistant to future break-up.

The study, published , and led by , who completed her PhD at the Department of Earth Science and Engineering at 911½ñÈÕºÚÁÏ with , focuses on the Turkana Depression, a remote region in northern Kenya and southern Ethiopia that forms part of the East African Rift Valley.

Gaining a better understanding of how the continents have broken apart over time offers important clues about major events in Earth’s history. Prof Ian Bastow Associate Professor in Earthquake Seismology, Department of Earth Science and Engineering, 911½ñÈÕºÚÁÏ

“Gaining a better understanding of how the continents have broken apart over time – and how this process created the jigsaw-like fit we see from space today – offers important clues about major events in Earth’s history involving vast accumulations of igneous rock, such as the Deccan Traps in India, whose eruption coincided with the extinction of the dinosaurs,” said Professor Bastow.

“Our research shows that in the future, continents may not break where we expect them to, and the locations of the large igneous provinces that sometimes form during rifting will be difficult to predict as well.”

Rethinking how continents break

To the north of the Turkana Depression lie the vast “Ethiopian Traps,” formed when a huge mantle plume – a column of hot rock rising from deep within the Earth – encountered the base of the African plate around 40 million years ago.

At that time, the Turkana region had already experienced an earlier, failed attempt at rifting (the Anza rift) that thinned the crust 60 million years ago, but it did not succeed in splitting the continent and creating a new ocean.

Conventional geological wisdom held that such thinned regions should be the first to yield when a mantle plume arrives, focusing both rifting and volcanic activity.

Instead, the new study shows the opposite: the failed rift appears to have strengthened the plate, protecting it from further stretching and volcanic activity.

“Seismically speaking, the tectonic plate below the Turkana Depression looks nothing like the Ethiopian Plateau to the north, despite both being located above the same hot mantle plume,” said Dr Kounoudis, now a postdoctoral researcher at the University of Oxford.

“In fact, it behaves more like an area that hasn’t been affected by a plume at all. The rocks there are colder, stronger, and far more resistant to rifting and magmatism.”

Listening to the Earth

To investigate the hidden structure beneath the Turkana Depression, the research team – including geophysicists from the UK, USA, Ethiopia, and Kenya – deployed a network of earthquake-monitoring stations on both sides of the Ethiopian-Kenyan border as part of a major NSF–NERC-funded project.

For over two years, the stations, powered by solar panels, continuously recorded seismic waves from earthquakes around the world. 

By analysing how these waves travelled through the crust and mantle, the team built a detailed picture of the plate’s thickness and composition to depths of around 200 kilometres.

The results revealed that the Turkana region’s lithosphere acts like a cold, rigid “lid” floating above the hot, convecting mantle – with no sign of widespread magma intrusion.

“We rose to the challenges of the COVID-19 pandemic as a collaborative international team to collect critical seismic and geodetic data.  We were surprised to find that earthquakes and plate opening were absent beneath the older, failed rift zone,” said Dr Martin Musila, recent PhD at Tulane University, USA.

Strength and resilience

The researchers suggest that when the failed rift formed around 60 million years ago, small amounts of melting occurred in the plate, removing water and other volatile elements. This process left behind a dry, strong plate that was far more resistant to later melting, fracturing, and volcanism as the East African Rift developed through the Depression.

“Our findings suggest that once a rift fails, the process can actually harden the plate, making it less likely to break again,” said Dr Kounoudis. “The challenge now is to apply what we’ve learned in East Africa to ancient rift systems around the world to better understand how continents have broken apart through geological time.”

Collaboration across continents

The research involved scientists from 911½ñÈÕºÚÁÏ, Tulane University, Addis Ababa University, Dedan Kimathi University, University of Nairobi, and the University of Montana. The project was jointly funded by the UK Natural Environment Research Council (NERC) and the US National Science Foundation (NSF), with additional support from the UK Global Challenges Research Fund (GCRF).

The work went ahead with permission from the National Commission for Science, Technology, and Innovation (Kenya), and with invaluable assistance from University of Addis Ababa President, Prof. Tassew Woldehana.