Where do tectonic plates submerged in the Earth's mantle go?

The tectonic plates that we see today may be the result of processes that continued over the past billion years only, but you can imagine that the outer shell of the planet’s surface is made up of rocky plates that float above the mantle layer, collide constantly, and sink under each other in a phenomenon called “the movement of tectonic plates.” Which look like crumbs from a giant cookie floating in a sea of ​​hot milk.

Here we must ask about the fate of those submerged masses of the earth's crust when they sink into the mantle layer?

Modern computer models - developed by researchers from Switzerland and the United States - show that the masses of rocky crust that sink into the mantle do not completely disintegrate, but weaken and bend to take the shape of a slender snake, and continue their movement within the mantle layer.

Those computer models also assumed that the movement of tectonic plates we see today may have been a continuous movement that originated only in the past billion years.

The movement of these tectonic plates generates earthquakes and volcanoes, and is the reason for the emergence of mountains and islands as well, which explains the fragmentation of the great continent into 7 continents and several thousand islands separated by seas and oceans.

However, science is still unable to fully explain the mechanism of plate tectonics.

For example, science has not yet explained the fate of submerged plates under other plates in a region called the "subduction" region that disappears in the mantle layer.

Divers in a famous rift between two underwater tectonic plates in Iceland (Shutterstock)

Weak subduction zones and permanent movement that takes millions of years

On November 10, the journal Nature published a study reviewing two-dimensional computer models of subduction zones that have been programmed using known physics to describe how materials behave, describing how rocks deform under certain forces.

The results of the research showed that when one of the plates was sinking under the other, the descending plate called “the plate” suddenly bends towards the bottom and cracks, and that this bending causes the lower end of the plate to be weaker and reduces its thickness as well.

This means that the sinking plates do not disintegrate, but rather slide under each other in a continuous motion that takes hundreds of millions of years, says lead author Taras Jeriya, professor of geophysics at the Swiss Institute of Technology in Zurich (ETH Zurich) in Switzerland.

Jeriya told Live Science that their computer simulations matched observations and deep seismic imaging that showed weak areas within the subduction zone in Japan.

An approximate cross-section showing the subduction zones and the movement of tectonic plates (Shutterstock)

When did you start?

The researchers also developed a computer model that takes into account the temperature of the Earth's interior to be 150 degrees Celsius hotter than it is now, in the process of simulating the temperature that it is likely to have reached more than a billion years ago.

They found that higher temperatures resulted in a sinking plate only a few miles from the mantle being shattered, because it was not able to maintain its weight in the mantle, which has become less viscous due to hot conditions.

Thus, the study concluded that the subduction process at that time was ending relatively quickly within a few million years, unlike modern subduction, which can last for hundreds of millions of years.

Professor Gera commented that this finding suggests that modern plate tectonics may have formed sometime in the past billion years only.

He added that the primitive shape of plate tectonics, which existed during antiquity in the period between 3.5 billion and 2 billion years ago, is completely different from its shape today.

The movement of tectonic plates also experienced a quiescent period about 1.8 billion to a billion years ago, during which the plates were much less active.

Given the impossibility of knowing the exact temperatures of the Earth's core over time, scientists will not be able to provide an accurate timeline of when the plates stopped splitting to begin their long journey in the mantle.

However, the new study provides a step in the way of harnessing computer modeling to formulate different hypotheses about the debate about the timing of plate tectonics.

Researchers are seeking to develop more advanced 3D models to explore this phenomenon and its relationship to earthquakes.