Scientists have discovered the source of the abnormal deformation of Earth's largest continental rift.

Computer simulations have confirmed that unusual deformation and rift parallel seismic anisotropy detected beneath the East African Rift system are the result of an African superplume of magma. Geophysicist D. Sarah Stamps explains that continental splitting is a combination of stretching and breaking deep within the Earth. This process is related to the elongation of the lithosphere, the rigid outer layer of the Earth. As the lithosphere becomes more tight, brittle changes occur in the upper part of the lithosphere, leading to rock fractures and earthquakes.

Research led by D. Sarah Stamps used three-dimensional thermodynamic modeling to find that the African superuplift - a huge upwelling of the mantle - caused the unusual parallel rift deformation observed in the East African Great Rift system. This adds to the complexity of the debate surrounding the primary forces driving the fracture, suggesting a combination of lithospheric buoyancy and mantle traction.

Stamps, who studies these processes by using computer modeling and global positioning systems to map ground motions with millimeter-level accuracy, likens the different ways continental rifts deform to playing with "silicone mud."

"If you hit the silicone mud with a hammer, it will actually crack," said Stamps, an associate professor in the Department of Earth Sciences at Virginia Tech's College of Science. But if you pull it away slowly, the silicone will stretch. So the Earth's lithosphere behaves differently on different time scales."

Whether stretching or breaking, the deformation produced by continental fissures usually follows a predictable directional pattern associated with the fissures: the deformation tends to be perpendicular to the rift. The East African Rift system, the largest continental rift system on Earth, has this kind of deformation perpendicular to the rift. But after more than 12 years of measuring the rift system using global Positioning System instruments, Stamps also observed deformation in the opposite direction, parallel to the rift system. Her team at the Laboratory of Geodesy and Tectonophysics has been trying to find out why.

Assistant Professor D. Sarah Stamps. Source: Virginia Tech University

In a recent study published in the Journal of Geophysical Research, the team used three-dimensional thermodynamic models to explore the processes behind the East African Rift Valley system, The model was developed by Tahiry Rajaonarison, the study's first author. His models show that the unusual, rift-parallel deformations of the rift system are driven by northward mantle flows associated with the African superuplift, a huge mantle upwelling that rises from deep within the Earth beneath southwest Africa, moves northeastward across the continent, and becomes shallower as it extends northward.

Their findings, combined with insights from a study the researchers published in 2021 using Rajaonarison's modeling techniques, help clarify the scientific debate about which plate drivers dominate the East African Rift system, explaining its deformations perpendicular to and parallel to the rift: Lithospheric buoyancy, mantle traction, or both.

As a postdoctoral researcher, Stamps began observing unusual, parallel deformations in the East African Rift Valley system using data from Global Positioning System stations that measured signals from more than 30 satellites orbiting the Earth from about 25,000 kilometers away. Her observations add a layer of complexity to the debate over the drivers of rift systems.

Some scientists have suggested that the East African fault is primarily driven by lithospheric buoyancy, which is relatively shallow and largely attributable to the high topography of the fault system (i.e., the African supergulf) and density variations in the lithosphere. It has also been suggested that horizontal mantle traction, a deeper force that interacts with the horizontally flowing mantle beneath East Africa, is the main driving force.

The team's 2021 study found through three-dimensional computational simulations that the rift and its deformation may be driven by both of these forces. Their model showed that lithospheric buoyancy was responsible for the more predictable deformation perpendicular to the rift, but these forces could not explain the anomalous deformation parallel to the rift identified by Stamps' GPS measurements.

In their newly published study, Rajaonarison once again used a three-dimensional thermodynamic model, this time focusing on the source of the rift's parallel deformation. His model confirmed that the anomalous deformation and rift parallel seismic anisotropy observed under the East African Rift system were caused by the African super convolution.

Seismic anisotropy is the orientation, or alignment, of rocks in a particular direction, in response to mantle flows, frits, or pre-existing structural formations in the lithosphere, Stamps said. In this case, the rocks are arranged in the same direction as mantle flow northward from the African supercrater, suggesting that mantle flow is the source of the rocks.

Rajaonarison said, "What we mean is that mantle flow is not driving some of the east-west, vertical direction of the rift, but it may be causing anomalous northward deformation parallel to the rift." "Our study confirms the previous idea that lithospheric buoyancy is the driving force behind the rift, but we also bring new insights that abnormal deformation may have occurred in East Africa."

Learning more about the process of continental fragmentation, including these anomalous processes, will help scientists decipher the complexities behind continental fragmentation, which they have been trying to crack for decades. "We are excited by Dr. Rajaonarison's numerical modeling results because it provides new information about the complex processes that shape the Earth's surface through continental fragmentation," said Stamps.

Scientists have discovered the source of the abnormal deformation of Earth's largest continental rift.

Computer simulations have confirmed that unusual deformation and rift parallel seismic anisotropy detected beneath the East African Rift system are the result of an African superplume of magma. Geophysicist D. Sarah Stamps explains that continental splitting is a combination of stretching and breaking deep within the Earth. This process is related to the elongation of the lithosphere, the rigid outer layer of the Earth. As the lithosphere becomes more tight, brittle changes occur in the upper part of the lithosphere, leading to rock fractures and earthquakes.

Research led by D. Sarah Stamps used three-dimensional thermodynamic modeling to find that the African superuplift - a huge upwelling of the mantle - caused the unusual parallel rift deformation observed in the East African Great Rift system. This adds to the complexity of the debate surrounding the primary forces driving the fracture, suggesting a combination of lithospheric buoyancy and mantle traction.

Stamps, who studies these processes by using computer modeling and global positioning systems to map ground motions with millimeter-level accuracy, likens the different ways continental rifts deform to playing with "silicone mud."

"If you hit the silicone mud with a hammer, it will actually crack," said Stamps, an associate professor in the Department of Earth Sciences at Virginia Tech's College of Science. But if you pull it away slowly, the silicone will stretch. So the Earth's lithosphere behaves differently on different time scales."

Whether stretching or breaking, the deformation produced by continental fissures usually follows a predictable directional pattern associated with the fissures: the deformation tends to be perpendicular to the rift. The East African Rift system, the largest continental rift system on Earth, has this kind of deformation perpendicular to the rift. But after more than 12 years of measuring the rift system using global Positioning System instruments, Stamps also observed deformation in the opposite direction, parallel to the rift system. Her team at the Laboratory of Geodesy and Tectonophysics has been trying to find out why.

Assistant Professor D. Sarah Stamps. Source: Virginia Tech University

In a recent study published in the Journal of Geophysical Research, the team used three-dimensional thermodynamic models to explore the processes behind the East African Rift Valley system, The model was developed by Tahiry Rajaonarison, the study's first author. His models show that the unusual, rift-parallel deformations of the rift system are driven by northward mantle flows associated with the African superuplift, a huge mantle upwelling that rises from deep within the Earth beneath southwest Africa, moves northeastward across the continent, and becomes shallower as it extends northward.

Their findings, combined with insights from a study the researchers published in 2021 using Rajaonarison's modeling techniques, help clarify the scientific debate about which plate drivers dominate the East African Rift system, explaining its deformations perpendicular to and parallel to the rift: Lithospheric buoyancy, mantle traction, or both.

As a postdoctoral researcher, Stamps began observing unusual, parallel deformations in the East African Rift Valley system using data from Global Positioning System stations that measured signals from more than 30 satellites orbiting the Earth from about 25,000 kilometers away. Her observations add a layer of complexity to the debate over the drivers of rift systems.

Some scientists have suggested that the East African fault is primarily driven by lithospheric buoyancy, which is relatively shallow and largely attributable to the high topography of the fault system (i.e., the African supergulf) and density variations in the lithosphere. It has also been suggested that horizontal mantle traction, a deeper force that interacts with the horizontally flowing mantle beneath East Africa, is the main driving force.

The team's 2021 study found through three-dimensional computational simulations that the rift and its deformation may be driven by both of these forces. Their model showed that lithospheric buoyancy was responsible for the more predictable deformation perpendicular to the rift, but these forces could not explain the anomalous deformation parallel to the rift identified by Stamps' GPS measurements.

In their newly published study, Rajaonarison once again used a three-dimensional thermodynamic model, this time focusing on the source of the rift's parallel deformation. His model confirmed that the anomalous deformation and rift parallel seismic anisotropy observed under the East African Rift system were caused by the African super convolution.

Seismic anisotropy is the orientation, or alignment, of rocks in a particular direction, in response to mantle flows, frits, or pre-existing structural formations in the lithosphere, Stamps said. In this case, the rocks are arranged in the same direction as mantle flow northward from the African supercrater, suggesting that mantle flow is the source of the rocks.

Rajaonarison said, "What we mean is that mantle flow is not driving some of the east-west, vertical direction of the rift, but it may be causing anomalous northward deformation parallel to the rift." "Our study confirms the previous idea that lithospheric buoyancy is the driving force behind the rift, but we also bring new insights that abnormal deformation may have occurred in East Africa."

Learning more about the process of continental fragmentation, including these anomalous processes, will help scientists decipher the complexities behind continental fragmentation, which they have been trying to crack for decades. "We are excited by Dr. Rajaonarison's numerical modeling results because it provides new information about the complex processes that shape the Earth's surface through continental fragmentation," said Stamps.