Researchers have revealed new details about the two mysterious point structures, located roughly on either side of the planet. Officially known as the Large Low Speed Provinces (LLSVPs), these spots are massive, each the size of a continent and 100 times higher than Mount Everest. Until now, scientists knew very little about these bubbles, why they exist, and why they have strange shapes of varying heights.
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Now, researchers have analyzed the structures and have been able to determine the extreme heights that the bubbles reach, as well as how the size and density of the bubbles, as well as the viscosity in the surrounding mantle, affect their height.
Arizona State University scientists Qian Yuan and Minming Li from the School of Earth and Space Exploration used geodynamic modeling and analysis to learn more about the two points.
The results of their seismic analysis led to the surprising discovery that the point under the African continent is about 1,000 km higher than the point under the Pacific Ocean.
According to Mr. Yuan and Mr. Li, the large difference in altitude between the two is best explained by the fact that the point under the African continent is less dense (and therefore less stable) than under the Pacific Ocean.
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The lead author, Mr. Yuan, said: “Our calculations found that the initial size of the bubbles does not affect their height.
“The height of the bubbles is primarily controlled by their density and the viscosity of the surrounding mantle.”
To conduct their research, the two scientists designed and ran hundreds of mantle convection simulations.
They comprehensively tested the effects of key factors that can influence blot height, including blot size and the variation in blob density and viscosity compared to its circumference.
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The unstable nature of the point under the African continent, for example, may be related to continental changes in topography, gravity, surface volcanoes and plate movement.
Yuan said: “Our combination of seismic finding analysis and geodynamic modeling provides new insights into the nature of Earth’s largest structures in the deep interior and their interaction with the surrounding mantle.
“This work has far-reaching implications for scientists trying to understand the current state and evolution of deep mantle structure and the convective nature of the mantle.”
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