Image Courtesy: ScienceDaily
A vast plume of hot rock rising from deep inside Earth may be helping pull Africa apart, scientists say. New computer models suggest that the enormous upwelling of mantle material known as the African Superplume is responsible for an unusual pattern of movement beneath the East African Rift System.
The East African Rift is the largest continental rift system on the planet and represents one of the most dramatic examples of a continent slowly breaking apart. While scientists expected the land to move mainly in the direction it is being stretched, GPS measurements revealed another puzzling motion running parallel to the rift. Researchers now believe deep mantle flow may help explain the anomaly.
Continental rifting occurs when Earth’s rigid outer shell, called the lithosphere, stretches and thins. Near the surface, rocks can fracture and produce faults and earthquakes, while hotter material deeper underground deforms more gradually.
Geophysicist D. Sarah Stamps of Virginia Tech and her colleagues spent more than 12 years collecting GPS data capable of measuring movements at the millimeter scale. Their observations showed the expected deformation across the rift, but also revealed unexpected movement running along its length.
Using 3D thermomechanical models, the research team investigated what could be causing this unusual motion. The simulations pointed to northward mantle flow associated with the African Superplume, a massive region of hot, rising mantle material that extends from deep beneath southwest Africa toward the northeast.
The findings add a new layer to the debate over what drives the East African Rift. Scientists have long considered whether the process is primarily controlled by buoyancy forces within the lithosphere or by forces created by flowing material deep within the mantle.
The new models suggest that both mechanisms play important roles. Shallower buoyancy forces appear to drive much of the expected stretching across the rift, while the northward flow of mantle material may be responsible for the anomalous deformation running parallel to it.
The simulations also reproduced a matching pattern of seismic anisotropy, in which seismic waves travel differently depending on their direction through underground rock. That alignment provides further evidence that deep mantle flow is influencing the region.
“We are saying that the mantle flow is not driving the east-west, rift-perpendicular direction of some of the deformations, but that it may be causing the anomalous northward deformation parallel to the rift,” researcher Tahiry Rajaonarison said.
The findings could help scientists better understand the complex forces involved when continents begin to break apart. As the East African Rift continues to evolve over millions of years, it remains a natural laboratory for studying how processes deep within Earth can reshape the planet’s surface.
