Dry Continental Crust Keeps Africa From Splitting Apart

Geological Discovery Challenges Continental Rift Theories

In a groundbreaking study that overturns long-held geological assumptions, researchers from Tulane University and an international team have discovered why some continents resist breaking apart while others split. The research, published in Nature, reveals that dry, gas-depleted continental crust is surprisingly strong and resistant to deformation - a finding that explains why Africa's continental breakup is proceeding much slower than expected.

The East African Rift Mystery

The study focused on the East African Rift System, one of the most active continental rift zones on Earth where the African plate is gradually splitting into the Somali and Nubian plates. While this process began approximately 30 million years ago, the separation has been progressing at a remarkably slow pace of less than one centimeter per year. 'We've always assumed that stretched and thinned crust would remain weak and vulnerable to further breakup,' explains Martin Musila, a PhD student who co-led the research. 'But our findings show exactly the opposite - dehydration makes the plate stronger.'

Ancient Volcanic Dehydration

The key discovery centers on the Turkana Depression, a low-lying region between Kenya and Ethiopia that experienced an earlier attempt at continental rifting between 80 and 60 million years ago. During this period, volcanic activity removed water and carbon dioxide from deep within the tectonic plate, essentially dehydrating the crust. 'About 80 million years ago, water and CO2 were extracted from the deep layers of the plate by volcanism,' Musila told EurekAlert. 'But through dehydration, the plate actually becomes stronger.'

Modern Geological Implications

The research team used sophisticated underground measurements, including earthquake monitoring and GPS data, to create detailed 3D maps of the subsurface. These maps clearly showed that current deformation and volcanic activity are actively avoiding the thin, dry sections of crust. 'Our research demonstrates that volcanism and plate stretching avoid the thin and dry parts of continental plates,' Musila emphasized. This finding has profound implications for understanding earthquake and volcanic hazards in rift zones worldwide.

Broader Scientific Significance

The discovery challenges fundamental assumptions in plate tectonics and continental rifting theory. According to Phys.org, the research overturns the long-held belief that once-thinned lithosphere remains weak and prone to reactivation. Instead, these dehydrated sections now act as barriers to deformation, with volcanic and tectonic processes bypassing these strengthened areas. The findings also provide crucial insights for locating mineral and energy resources in ancient rift zones, including potential applications along the U.S. Gulf Coast.

The international collaboration included researchers from Tulane University, University of Montana, Imperial College London, Addis Ababa University in Ethiopia, and universities in Kenya. Their work demonstrates that Earth's lithosphere carries a 'memory' of past geological events that continues to shape modern tectonic processes millions of years later.