Earth: Scientists have figured out what happens to the Earth’s crust as it erodes

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The outer shell of Earth is formed of (less-tasty) rocky rafts that constantly bump into and dive beneath one other in a process called plate tectonics, similar to a gigantic broken-up cookie whose bits float atop a sea of hot milk.

So, what happens to those hunks of vanishing crust as they plunge into the milky interior of the Earth?

According to new modeling research, they become weak and bendy, similar to a slinky snake toy, yet they do not entirely dissolve. Plate tectonics, at least in its contemporary form, appears to have only begun in the last billion years, according to the simulations.

Plate tectonics is responsible for earthquakes and volcanoes, the formation of mountain ranges and islands, and the separation of Earth’s continents, which were once supercontinent. But there’s still a lot we don’t know about plate tectonics, like what happens when one plate slips beneath another (in a region known as a subduction zone) and vanishes into the mantle, the planet’s middle layer, which is made up of scorching solid rock rather than milk.

The researchers used 2D computer models of subduction zones that were coded using known physics of how materials react, such as how rocks deform under particular forces, to figure this out. The researchers then observed the model see what happened near the subduction zone and compared their findings to real-world data.

Their simulations suggested that as one plate dipped beneath another, the descending piece, known as a slab, abruptly bent downward and fractured, with the grains on the underside of the plate becoming finer and weaker as a result of the bending. The forces mainly left the plate intact, but there were a lot of weak spots.

This means the plates don’t break apart and continue to draw on the portions behind them “for a very long period,” according to lead author Taras Gerya, a geophysics professor at the ETH Zurich in Switzerland. He claims that the plate can continue to slide beneath the other plate for hundreds of millions of years.

According to Gerya, their calculations matched observations and deep seismic imaging that showed weakened portions of a subduction zone in Japan.

Their models are “strong and useful,” according to Kent Condie, a professor emeritus of geochemistry and Earth and environmental science at the New Mexico Institute of Mining and Technology who was not engaged in the study.