Inside interior of the earth, in the lowermost part of the mantle and surrounding the planet’s core, there are two huge ‘patches’as if they were large additional structures, different material to those around them, and it’s something that has puzzled scientists for years. Added together, both accumulations represent 3% to 9% of the planet’s total volume.
The difficulty in revealing the nature of these structures arises from the impossibility of reaching them directly. They are too far from the surface. The deepest excavation to date reached 12,200 meters, but still failed to penetrate the earth’s crust, let alone the mantle.
But earthquakes help scientists explore what lies deep beneath our feet. Seismic tomography is the technique used to analyze structures It forms the interior of the planet.
When an earthquake occurs, energy waves spread in all directions. By measuring tremors from various points on the surface, scientists can create a map of the Earth’s interior.
Since the densities of the rocks and liquids inside the planet are different, these waves pass through them at different speedsIt allows geologists to clarify what type of material the waves are passing through.
This is how two large and unknown structures called Large Low Shear Velocity Regions (LLSVP) were discovered many years ago. In these regions, seismic waves travel slower through the surrounding mantle. One of these ‘spots’ or ‘pieces’ is known as ‘Tuzo’, it is located beneath Africa and is approximately 800 kilometers high.This is equivalent to at least 90 Mount Everests in a row.
Two main hypotheses
What these mysterious structures are and how they are formed is a subject that still does not have a clear answer, although there are some increasingly solid hypotheses. These structures are denser in the lower mantle than the material around them. So although seismic tomography cannot determine what it is or its specific density, it seems clear that they are made of a different material.
According to scientists, there are two main hypotheses. One of them thinks LLSVP is large accumulations of oceanic crust that may have sunk (as if they had sunk into the Earth) and were buried in their current location billions of years ago.
The second theory is that these giant pieces These would simply be fragments of a planet that collided with Earth while the Solar System was still forming.4.5 billion years ago. This planet, known as Theia, would be much smaller than Earth (about the size of Mars) and would collide with us, sending large amounts of debris flying into space and clumping together under the influence of gravity over time. and they would form the Moon.
Well, it is believed The ‘pieces’ of the lower mantle may actually be fragments of Tehia, parts of its mantle, which is denser than ours, mixed with the Earth. it was there during the collision and would still remain there today.
In fact, in 2021, a team modeled simulations of this catastrophic event and found that Theia’s mantle could survive today.
There is no complete certainty about either hypothesis due to limitations in research resources, but scientists believe that progressive technical advances will soon allow us to know what these huge mysterious pieces ‘buried’ in our mantle are.
Reference work: https://progearthplanetsci.springeropen.com/articles/10.1186/s40645-020-00327-1
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