New research led by geophysicist D. Sarah Stamps has shed light on the primary forces driving the unusual deformations observed in the East African Rift System. Using 3D thermomechanical modeling, Stamps and her team have found that the African Superplume, a massive mantle upwelling, is responsible for the rift-parallel deformations detected in the region.
Continental rifting involves the stretching and fracturing of the Earth’s lithosphere, its rigid outer layer. As the lithosphere becomes more taut, it undergoes brittle changes, leading to rock fractures and earthquakes. Typically, the deformation that occurs during continental rifting follows predictable directional patterns in relation to the rift, with the deformation being perpendicular to the rift. However, Stamps observed that the East African Rift System also exhibited deformation that went parallel to the rifts, adding complexity to the understanding of the forces driving the rift system.
To investigate this phenomenon, Stamps and her team used computer modeling and GPS measurements to map surface motions with millimeter precision. They compared the deformation styles of a rifting continent to playing with Silly Putty, noting that the lithosphere behaves differently on different time scales.
In a recent study published in the Journal of Geophysical Research, the team utilized 3D thermomechanical modeling developed by Tahiry Rajaonarison, a postdoctoral researcher at New Mexico Tech. Rajaonarison’s models revealed that the unusual, rift-parallel deformation in the East African Rift System is driven by northward mantle flow associated with the African Superplume. This massive upwelling of mantle rises from deep within the Earth beneath southwest Africa and extends northeast across the continent.
The findings of this study, combined with insights from a previous study published in 2021, could help resolve the scientific debate surrounding the dominant plate-driving forces in the East African Rift System. The researchers suggest that a combination of lithospheric buoyancy forces and mantle traction forces contribute to both the rift-perpendicular and rift-parallel deformations observed in the region.
Stamps began observing the unusual, rift-parallel deformation in the East African Rift System using data from GPS stations that measured signals from satellites orbiting Earth. Her observations have added complexity to the ongoing debate about the driving forces behind the rift system. Some scientists attribute the rifting in East Africa primarily to lithospheric buoyancy forces, while others point to horizontal mantle traction forces as the primary driver.
The team’s previous study using 3D computational simulations showed that a combination of these two forces could drive the rift and its deformation. However, the lithospheric buoyancy forces alone could not account for the anomalous, rift-parallel deformation observed in Stamps’ GPS measurements.
In their latest study, Rajaonarison’s 3D thermomechanical modeling confirmed that the African Superplume is responsible for the unusual deformations and rift-parallel seismic anisotropy observed beneath the East African Rift System. Seismic anisotropy refers to the alignment of rocks in response to mantle flow or other factors. In this case, the alignment of rocks followed the direction of the African Superplume’s northward mantle flow, suggesting mantle flow as the source of the deformations.
The researchers believe that understanding these anomalous deformations and the processes involved in continental rifting will contribute to unraveling the complexity behind the breaking of a continent. This new insight into the complex processes shaping the Earth’s surface through continental rifting is an exciting development for the field of geophysics.
The study, titled “A Geodynamic Investigation of Plume-Lithosphere Interactions Beneath the East African Rift,” was published in the Journal of Geophysical Research Solid Earth.
How does the African Superplume contribute to both perpendicular and parallel deformations in the East African Rift System?
E perpendicular and parallel deformations observed in the region.
Stamps explains that the African Superplume plays a critical role in driving the rift-parallel deformations. As the massive upwelling of mantle flows northward beneath the East African Rift System, it exerts forces on the overlying lithosphere, causing it to deform both perpendicular and parallel to the rift. This newly discovered mechanism challenges previous assumptions about the primary driving forces of continental rifting.
The team’s 3D thermomechanical models provided a detailed understanding of the complex interactions between the African Superplume and the lithosphere. By simulating the thermal and mechanical behavior of the Earth’s crust and mantle, the researchers were able to accurately recreate the observed deformations, further supporting their findings.
This research has significant implications for our understanding of rift systems worldwide. Stamps emphasizes that the East African Rift System serves as an excellent natural laboratory for studying the dynamics of continental rifting. By unraveling the forces behind its unique deformations, scientists can gain valuable insights into similar tectonic processes occurring in other regions, such as the Red Sea and the Gulf of California.
Moving forward, Stamps and her team plan to refine their models and expand their research to other rift systems around the world. They hope that their findings will contribute to a more comprehensive understanding of the forces driving continental rifting, ultimately improving our ability to predict and mitigate the seismic hazards associated with these geological processes.
This research could provide valuable insights into the dynamic geologic processes shaping the East African Rift System.