The East African Rift System (EARS) is a 4,000-mile-long continent rift that stretches from Jordan in southwestern Asia into east Africa around Mozambique. This rift is the result of geologic forces pulling the Nubian and Somalian tectonic plates apart, a process which began some 25 million years ago. Scientists estimate that the rift could one day even split Africa in two and form an entirely new ocean (though that might take awhile, as the two plates are currently moving a part and the breakneck speed of 0.5 inches per year).
One of the main characteristics of rifts is that they form deformations perpendicular to plate movement. In other words, as plates move away from one another, a rift forms perpendicular to that rift. But EARS tends to flout that rule, and instead forms both perpendicular and parallel deformations in relation to the rift.
Understanding the intricate mechanics of EARS is important, as the rift is largely responsible for much of the seismic activity in East Africa. For years, scientists haven’t been able to find an answer to this geologic anomaly—but now, they may finally have one.
In a new paper—published in March of this year in the Journal of Geophysical Research—scientists from Virginia Tech explored the inner workings of EARS using GPS and 3D thermomechanical modeling. They discovered that northward mantle flow driven by the African Superplume—a massive upwelling of molten rock that transports heat from the Earth’s core—is responsible for the atypical, rift-parallel deformations.
Detailed plate movement derived from several studies as well as descriptions of two plume models.Virginia Tech
Meanwhile, another geologic force known as lithospheric buoyancy (the lithosphere being the slice of Earth that includes the crust and upper mantle) is responsible for the more perpendicular deformations.
“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,” co-author Tahiry Rajaonarison said in a press release. “We confirmed previous ideas that lithospheric buoyancy forces are driving the rift, but we’re bringing new insight that anomalous deformation can happen in East Africa.”
This discovery will play a crucial role in modeling the future activity of EARS and predicting how these geologic forces will shape the African continent.
Source: Popular Mechanics