Study of two blobs in Earth's mantle shows unexpected differences in height, density

Earth has a thin outer crust, a thick mantle, a fluid outer core, and a solid inner core. There are two massive blob-like structures on opposite sides of the planet. The Large Low-Shear-Velocity Provinces are 100 times taller than Mt. and each is the size of a continent. Everest. The other is under the Pacific Ocean.

Despite their prominent features, scientists know that the two blobs have complicated shapes and structures, but little is known about why the blobs exist or what led to their odd shapes.

Two scientists from the School of Earth and Space Exploration at Arizona State University are studying the two blobs using seismology and modeling. Through their research, they were able to determine the maximum heights that the blobs reach and how the volume and density of the blobs, as well as the surrounding viscosity in the mantle, might control their height. Their research was published.

The blob under the African continent is over a thousand km higher than the blob under the Pacific Ocean. The best explanation for the height difference between the two is that the blob under the African continent is less dense than the one under the Pacific Ocean.

To conduct their research, Yuan and Li ran hundreds of simulations. They tested the effects of key factors that may affect the height of the blobs, including the volume of the blobs and the contrast of density and viscosity of the blobs compared with their surroundings. They found that the African blob must be of a lower density than the Pacific one in order to explain the differences in height.

The initial volume of the blobs doesn't affect their height, according to the lead author.

The co-author said that the Africa LLVP may have been rising recently.

The findings may change the way scientists think about the deep mantle processes. The blob under the African continent may be related to continental changes in topography, gravity, surface volcanism and motion plate.

This work has far-reaching implications because of the combination of the analysis of seismic results and the modeling.

More information: Qian Yuan et al, Instability of the African large low-shear-wave-velocity province due to its low intrinsic density, Nature Geoscience (2022). DOI: 10.1038/s41561-022-00908-3 Journal information: Nature Geoscience Citation: Study of two blobs in Earth's mantle shows unexpected differences in height, density (2022, March 10) retrieved 10 March 2022 from https://phys.org/news/2022-03-blobs-earth-mantle-unexpected-differences.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.