Deep in the Earth’s mantle, there two giant dots. One is located under Africa and the other is almost opposite the first, under the Pacific Ocean. But these two points are not equally congruent.
New research finds that the point under Africa extends closer to the surface, and is more stable than the point under the Pacific Ocean. Ultimately, this difference could help explain why the crust under Africa has risen to a higher level and why the continent has experienced many massive volcanic eruptions over hundreds of millions of years.
This instability could have many repercussions on surface tectonic motion, as well earthquakes Qian Yuan, a graduate fellow in geology at Arizona State University (ASU) who led the research said:
pair of dots
Mantle points are more accurately known as “Low Velocity Large Wave Perturbations,” or LLSVPs. This means that when seismic waves generated by earthquakes travel through these deep regions, the waves slow down. This hysteresis indicates that there is something different in the mantle at this location, such as density or temperature – Both.
Scientists are not sure why the mantle points exist. Yuan told WordsSideKick.com that there are two common hypotheses. One of them is that it consists of accumulations of crust from which it has slipped a landFrom the surface to the depths of the mantle. Another is that it is the remnant of a magma ocean that may have existed in the lower mantle during Earth’s early history. in this way The magma in the ocean cooled and crystallized.It may have left behind areas that were much denser than the rest of the mantle.
Yuan said previous studies have hinted that these two points may not be the same, but none of this research has used easily comparable global data sets. He and his advisor, Arizona State University associate professor of geodynamics Mingming Li, examined 17 global seismic wave datasets to determine the height of each point.
They found that African Point stretches 620 miles (1,000 kilometers) higher than Pacific Point. This is a difference of about 113 . Mount Everest. In total, the mass of the Pacific Ocean extends 435 to 500 miles (700 to 800 km) from the core mantle boundary. African Point stretches upwards from 990 to 1,100 miles (1,600 to 1,800 km).
point of instability
Then the researchers used computer models to find out which features of the points might explain these differences. They found that the most important were the density of the points themselves and the viscosity of the surrounding mantle. Viscosity refers to the ease with which mantle rocks can be deformed.
According to Yuan, for the African tip to be much longer than the tip of the Pacific Ocean, it would have to be much less dense. “Because it is less dense and unstable,” he said.
The African land mass is still far from Earth’s crust – the entire mantle is 1,800 miles (2,900 km) thick – but the instability of this deep structure could have implications for the planet’s surface. LLSVPs can be a source of hot plumes of rising mantle material. These plumes, in turn, could cause giant volcanic eruptions, tectonic disturbances, and possibly even continental breakup, Yuan said.
The African point “is very close to the surface, so there is a possibility that a large plume of mantle will rise from the African point and cause more surface uplift, earthquakes and giant volcanic eruptions,” Yuan said.
These processes occur over millions of years and have been ongoing in Africa. Yuan said there appears to be a link between African Point and major volcanic eruptions. paper 2010 Published in Nature It was found that in the last 320 million years, 80% of the kimberlite, or massive mantle rock eruptions that bring Diamante On the surface, it happened just above the African Point boundary.
Yuan Li published his findings on March 10 in the journal natural earth sciences. They are now working on point origins. Although these results have not yet been published in a peer-reviewed journal, the researchers will present the findings at the 52nd Lunar and Planetary Science Conference in March 2021; This research suggested these points It could be the remnants of an object the size of a planet who who It hit the Earth about 4.5 billion years ago.Moon formation.
Originally published in Live Science.
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