(ORDO NEWS) — Deep in the mantle of our planet, there are two spots. One is under Africa and the other is under the Pacific Ocean.
A new study has found that the patch under Africa extends much closer to the surface and is more unstable than the patch under the Pacific Ocean.
This difference may ultimately explain why the crust under Africa has risen up and why the continent has seen so many major supervolcano eruptions over hundreds of millions of years.
A 3D image of a patch in the Earth’s mantle beneath Africa is shown in red, yellow, and orange. Blue represents the boundary between the core and mantle, blue represents the surface, and transparent gray represents the continents
“This instability could have many implications for surface tectonics as well as earthquakes and supervolcano eruptions,” says Qian Yuan, an Arizona State University (ASU) scientist who led the study.
Mantle patches are known as “large areas of low shear wave velocity”. This means that when seismic waves generated by earthquakes pass through these zones, they slow down. This fact indicates that there is something different in the mantle at that location, such as density or temperature (or both).
Scientists aren’t sure why mantle spots exist. There are several popular hypotheses. For example, one is that the spots are the remnants of an ocean of magma that may have existed in the lower mantle in the early history of the Earth. As this magma ocean cooled and crystallized, it could leave regions that became denser than the rest of the mantle.
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