Enormous blob beneath Africa explained amid concerns of a supervolcano

Two giant blobs, sitting deep beneath the Earth's surface stretching across thousands of miles, have been discovered by scientists. One of them, which happens to be underneath Africa, is slowly growing up towards the surface.

Scientists first discovered the two giant structures through seismic observations. The anomalies are found at the base of Earth's mantle, between 400 and 1,600 miles below the surface, above the outer core.

One blob resides beneath the Pacific Ocean, while the other resides underneath Africa. They are known as Low-Shear-Velocity Provinces (LLSVPs) and can influence both core and mantle processes. These structures are thought to be composed of recycled oceanic crust or iron-rich materials and are known as "thermochemical piles."

Scientists from Arizona State University studied these structures to better understand what they are and where they are in Earth's mantle, and published their findings in the journal 'Nature Geoscience.'

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How did scientists get to know about the blobs?

Qian Yuan and Mingming Li carried out seismic simulations, performing hundreds of mantle convection simulations. Based on these results, there is a substantial difference in density between the two blobs, with the African LLSVP appearing to be less dense and, therefore, less stable.

The structure under Africa is approximately 620 miles higher than the blob under the Pacific. The African structure reaches a maximum height of approximately 990 to 1,100 miles, while the Pacific anomaly ranges between 430 and 500 miles.

The height and density differences suggest that the anomalies are composed in different ways, have different dynamics, and have evolved over time differently.

Speaking to the outlet Newsweek, Yuan said:

"We had a sense that the African LLVP is higher than the Pacific, but we were really surprised when we found the African one is much higher ... than the Pacific."

Previous studies have linked LLSVPs to volcanism. At their edges, the plumes appear to deflect the mantle flowing away from the surface. Researchers published a study in 2020 that linked this blob to volcanic activity between 155 and 95 million years ago in southeastern Africa.

Commenting on this, Li said that the African LLSVP has been rising in recent geological times, which explains the uprising of surface topography and also the severe volcanism in East Africa.

Yuan further continued that even though they have not calculated the speed of African LLVP rising, it still may take a few million years for it to creep out on the surface.

According to Yuan, if the blob continues to rise, more supervolcanoes and earthquakes may occur in Africa millions of years from now.

However, Li told the outlet that the structure is probably rising at a rate of around one to two centimeters per year.

"The top of the African LLVP is at a depth of [around] 1,000 km. Therefore, it would take about 50-100 million years for it to reach the surface, assuming it raises with a velocity of 1-2 cm per year. In fact, as the African rises, it may become cold and dense. It is not impossible for it to sink again when it becomes dense enough."

Researchers Yuan and Li said their findings, using analysis of seismic results and geodynamic modeling, could change how scientists examine LLSVPs and how they influence activity on the Earth's surface. Along with volcanic activity, the blobs have also been associated with topographic changes, magnetic fields, and the movement of tectonic plates.

They said that their findings from this study have enormous implications for scientists who are trying to understand mantle structure and convection in the deep mantle.