Experts have uncovered islands hundred times larger than Mount Everest and billions of years old
Researchers have uncovered structures more massive than Mount Everest, but the catch is that they are underneath people's feet. These structures have been explained in the journal Nature. Through seismic modeling, experts have detected two massive structures 1,200 miles beneath Earth's surface under Africa and the Pacific Ocean. These structures have been deemed as Large Low Shear Velocity Provinces (LLSVPs), and are supposedly a hundred times taller than Mount Everest. If the assertions are true, then they provide new insights into Earth's interior and the mannerisms followed by the mantle.
What is Seismic Modeling?
The seismic modeling applied in the study utilizes whole-Earth oscillations to map the proceedings underneath the surface, according to Daily Galaxy. The oscillations help experts determine how the planet vibrates after an earthquake. The evaluation maps the three-dimensional (3D) attenuation properties of the Earth's mantle. Seismic waves move differently, in accordance with the density, temperature, and composition of the material they are passing through. Under regions, such as Africa and the Pacific, researchers detected that these waves were slower compared to other places. It suggests that massive anomalous structures are located at the core-mantle boundary. These structures are the LLSVPs.
Features of the Large Low Shear Velocity Provinces (LLSVPs)
The LLSVPs are supposedly continent-sized and referred to as islands in the study, according to Earth.com. These structures are not only hotter than their surroundings but also older. Further investigations revealed that the structures dated back to around half a billion years or longer. The study cited the elevated temperature of this structure as the reason why the seismic waves slow down in this region. The presence of LLSVPs proves that the Earth's mantle is not a well-mixed and rapidly flowing system; instead, it has solid structures that act as barriers. Both of these islands supposedly measure 620 miles in height, making them longer than any mountain system and larger than any other planet in the solar system. Both of these structures were detected in the 20th century through seismic analysis.
Both of these islands made Earth resonate like a bell after large earthquakes. The oscillations produced as a result helped researchers locate subsurface anomalies they identified as LLSVPs. These LLSVPs are elusive, as experts have been unable to investigate them properly due to their remote location. "Nobody knows what they are, and whether they are only a temporary phenomenon or if they have been sitting there for millions or perhaps even billions of years," explained study senior author Arwen Deuss, a seismologist at Utrecht University. Experts detected several sunken tectonic plates around these islands. These plates came into the specific location in the mantle, apparently through subduction, a process through which one plate sinks beneath another.
Insights from Damping
Researchers also found differences in the way seismic waves behave in the islands and in the upper mantle. The team came to this conclusion after examining the damping of these seismic waves. Damping is essentially the amount of energy that the waves lose when they travel through a particular area. "Against our expectations, we found little damping in the LLSVPs, which made the tones sound very loud there," shared Duess' colleague Sujania Talavera-Soza.
"But we did find a lot of damping in the cold slab graveyard, where the tones sounded very soft." Less damping was shocking, as seismic wave behavior in the upper mantle revealed that the hotter a region is, the more damping it would cause. Researchers believe the large grain size of LLSVPs compared to the upper mantle led to this difference. If the suggestion is accurate, then the mantle may not be as uniform as past studies suggested. These findings aid experts in understanding the dynamic nature of the Earth's interior.