There are two giant blobs. One is under Africa and the other is under the Pacific Ocean. The two blobs are not evenly matched.
The blob under Africa is more unstable than the blob under the Pacific, according to new research. This difference could help to explain why the Africa has seen so many large supervolcano eruptions over hundreds of millions of years.
The instability can have a lot of implications for the surface tectonics, as well as earthquakes and supervolcanic eruptions, according to the graduate associate in geology who led the research.
Large low-shear-wave-velocity provinces are known as the mantle blobs. The waves slow down when they travel through the deep-mantle zones. There is something different about the mantle at this spot, such as density or temperature.
The scientists don't know why the mantle blobs exist. According to Live Science, there are two popular hypotheses. They are made up of crust that has been subducted from Earth's surface to deep inside the mantle. They are the remnants of an ocean of magma that may have existed in the lower mantle during Earth's early history. The ocean may have left behind areas that were denser than the rest of the mantle.
The two blobs may not have been created equal, but no research had used global data sets to compare the two. He and his adviser looked at 17 global data sets to determine the height of each blob.
The African blob is about 1,000 kilometers higher than the Pacific blob. That is a difference of more than 100 Mount Everests. The Pacific blob extends upward from the boundary between the core and the mantle up to 500 miles. The African blob extends upward from 980 to 1,100 miles.
The researchers used computer modeling to figure out which features of the blobs explained the differences. They found that the density of the blobs and the surrounding mantle were the most important ones. The ease with which mantle rocks can be changed is referred to as Viscosity.
The African blob must be less dense than the Pacific blob to be so tall.
The African blob is far away from the Earth's crust, but the deep structure of the mantle may have implications for the planet's surface. The hot material in the mantle may come from the LLSVPs. It is possible that these plumes will cause supervolcano eruptions, tectonic upheaval and even continental break up.
The African blob is very close to the surface, so there is a chance that a large mantle plume may rise from it and lead to more surface rising and earthquakes.
These processes have been going on in Africa for millions of years. There seems to be a connection between the African blob and major eruptions. A 2010 paper published in the journal Nature found that 80% of kimberlites, or huge eruptions of mantle rock that bring diamonds to the surface, have occurred right over the boundary of the African blob.
Their findings were published in the journal Nature Geoscience. They are researching the origins of the blobs. The researchers presented the results of their research at the 52nd lunar and planetary science conference in March of 2021.
It was originally published on Live Science.
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