Superplume Beneath Continent Is Splitting Africa Apart
Aerial view of Suguta River in the Great Rift Valley. Kenya.
Sophisticated chemical analysis of volcanic gases from Kenya have provided the first evidence that a superplume lies beneath East Africa driving active tectonics and slowly separating the Somali plate and the Horn of Africa from the rest of the continent.
An international team of scientists led by Professor Fin Stuart from the University of Glasgow, working in partnership with the Kenya Geothermal Development Company, has discovered surprising results in a new study of gases from the Menengai geothermal field in central Kenya.
The rift valleys of East Africa are some of the largest and most spectacular topographic features on Earth. They extend for 3,500 kilometers through Ethiopia, Kenya, Uganda and Malawi, and host extensive volcanic fields. The rifts are the manifestation of the African tectonic plate being split apart driven by forces in the Earth's interior. However, scientists are uncertain whether the volcanism and rifting is due to shallow processes or whether it is driven by up-welling hot material from Earth's mantle.
As countries along the rift zone are tapping into geothermal energy, scientists get access to new sampling sites. The researchers used gases collected from the Menengai geothermal field (started in 2009 and still in development) in central Kenya to reconstruct the source in Earth's mantle feeding the geothermal activity.
The team notes that the gases are chemically indistinguishable from gases present in volcanic rocks from Hawaiʻi', where volcanism is fueled by a mantle plume. Together with the common chemical 'fingerprint' between different geothermal fields— the researchers compared their results with gas samples coming from the Red Sea to the north and from Malawi to the south — this discovery supports the theory that a single "superplume" is the main source.
'Our research suggests that a giant hot blob of rock from the core-mantle boundary is present beneath East Africa," summarizes Stuart. The plume not only drives the tectonic plates apart, but also pushes up the African continent preventing the rift zone to be flooded by the Red Sea (forming the geologically spectacular landscapes of the Afar Depression).
Map of East Africa showing some of the historically active volcanoes (red triangles) and the Afar ... More Depression (shaded, center).
Seismic surveys indicate the presence of a large anomaly beneath the southern tip of the African continent. Such "Large Low Shear Velocity Provinces" are composed of hot and weak mantle material, and the only other similar anomaly lies beneath the Pacific Plate. They may be the primary source feeding the mantle plume of Hawai'i and the plume beneath Africa, explaining the identical chemical signatures as described by the researchers.
The study,"Neon Isotopes in Geothermal Gases From the Kenya Rift Reveal a Common Deep Mantle Source Beneath East Africa," was published in the journal Geophysical Research Letters.
Additional material and interviews provided by the University of Glasgow.
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