A blob of the Earth's gooey insides linked to volcanic eruptions has been detected below southern Africa.
The newly discovered blob is known to geologists as a mid-mantle plume. Mantle plumes are columns of hot, gushy gunk that flow toward the Earth's surface and are a known contributor to volcanic activity. Until now, the mid-section of a mantle plume has never been imaged.
Mid-mantle plumes are hotter and move faster — roughly 4 inches (10 centimeters) per year — than the scorching, molten rock deeper inside the Earth, which is called the Earth's mantle. The mantle buoys the sprawling rocky plates that make up the Earth's crust. When these plates collide with each other, volcanoes and mountain ranges are born. The process spans millions of years, however, since an average plate moves between 0.4 and 4 inches (1 to 10 cm) per year.
Mantle plumes form a heat pipeline from the Earth's core to the upper region of the mantle. Plumes don't directly cause volcanoes on the Earth's continents, but they are one ingredient in a volcanic eruption, said study team member Don Helmberger of Caltech. There is some evidence that mantle plumes can trigger volcanic eruptions in oceanic places such as Iceland and Hawaii, Helmberger told OurAmazingPlanet.
Mantle plumes form deep within the Earth, where they can be up to 3,100 miles (5,000 kilometers) wide. As a plume head of magma rises from deep within the Earth, it tapers to roughly 62 miles (100 km) wide near the upper mantle.
Using seismic data, the researchers were able to locate the mid-mantle plume under the Kaapvaal region of southern Africa. The researchers estimate that its width is no larger than 93 miles (150 km).
The newfound mid-mantle plume is angling up toward the East African Rift — a chasm in eastern Africa that's been growing due to the African continental plate ripping apart. The study could help scientists understand the characteristics and dynamics of structures in the lower mantle as well as the geology of the southern African region.
The study is detailed in the May 4 issue of the journal Geophysical Research Letters.
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