In a recent study published in the Journal of Geophysical Research: Solid Earth, geophysicist D. Sarah Stamps and her team at the Geodesy and Tectonophysics Lab explored the processes behind the East African Rift System using 3D thermomechanical modeling. Stamps compared the different deformation styles of a rifting continent with playing with Silly Putty, stating that whether in stretching or breaking, the deformation that comes with continental rifting usually follows predictable directional patterns in relation to the rift, with the deformation tending to be perpendicular to the rift.
Rift-Parallel Deformation in the East African Rift System
After measuring the East African Rift System with GPS instruments for more than 12 years, Stamps observed deformation that went in the opposite direction, parallel to the system’s rifts. In a study published in 2021 using Rajaonarison’s modeling techniques, the team found through 3D computational simulations that the rift and its deformation could be driven by a combination of lithospheric buoyancy forces and horizontal mantle traction forces, accounting for both its rift-perpendicular and rift-parallel deformation.
The African Superplume
In their newly published study, Rajaonarison used 3D thermomechanical modeling to focus on the source of the rift-parallel deformations. His models confirm that the African Superplume, a massive upwelling of mantle that rises from deep within the Earth beneath southwest Africa and goes northeast across the continent, is responsible for the unusual deformations as well as rift-parallel seismic anisotropy observed beneath the East African Rift System.
New Insight into Anomalous Deformations
Seismic anisotropy is the orientation or alignment of rocks in a particular direction in response to mantle flow, melt pockets, or pre-existing structural fabrics in the lithosphere. In this case, the rocks’ alignment followed the direction of the African Superplume’s northward mantle flow, suggesting mantle flow as their source. Rajaonarison confirmed previous ideas that lithospheric buoyancy forces are driving the rift but brought new insight that anomalous deformation can happen in East Africa. Learning more about the processes involved in continental rifting, including these anomalous ones, will help scientists understand the complexity behind the breaking of a continent.
The study provides new information about the complex processes that shape the Earth’s surface through continental rifting. Stamps and her team were excited about the results from Rajaonarison’s numerical modeling, which shed light on the anomalous deformation in the East African Rift System. The findings could also help clear up scientific debate on which plate-driving forces dominate the East African Rift System, accounting for both its rift-perpendicular and rift-parallel deformation: lithospheric buoyancy forces, mantle traction forces, or both.
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