What drives the earth's crust under our feet?

Little Mohamed Western

The earth's crust swims over a partially molten scarf. But which one moves the other? According to a new scientific study, platelets and mantle form a single system, and the effect appears to be mutually exclusive.

The chicken and the egg
Researchers have been trying for decades to understand what drives the complex movements of the Earth's surface. Geologists like the mystery of the chicken and the egg appeared. Does the mantle move the plates through the rising heat currents or are the plates pushing the mantle by diving its cold limbs into it?

To solve this dilemma, a team of researchers from the French University of Grenoble and the University of Austin in the United States took the issue from a completely different angle, treating these components as a single system. For this purpose, researchers have developed three-dimensional simulation models supported by complex equations that supercomputers need to solve.

The researchers, published in the October 30 study in the journal Science Defense, say that we have looked at this question the wrong way all the time, and we should stop asking the question whether it is the diving of the ends of the cold crust inside the mantle that drives it to move. Or vice versa, both play an important role in drawing the terrain on the planet's surface.

Scientists have long believed that the movement of the outer crust results from convection currents inside the liquid and compressed rocks we call the mantle, as they rise, cool, and then descend deep into the planet.

At the same time, scientists have collected additional information since the 1950s on how the earth's crust dives in some areas and its rise in others, forming fresh new rocks as the old crust melts into the mantle.

Therefore, models attempting to describe this process have encountered considerable difficulties in trying to adapt the plate's drag and friction forces to the dynamics of the deep mantle flowing down below.

The cortex dominates the mantle
"The results indicate that the force of plate pulling dominates the mantle clouds at the base of the plates, suggesting that tectonic plates drive mantle flow," the researchers said in their study.

The picture we get now shows that we are not swimming over a flowing scarf, but sailing on the continental "sailing boats", creating swirls in the molten sea beneath us.

The team's findings allowed us to create a planet (simulated) similar to ours and watch it evolve over 1.5 billion years. By looking at the mantle and the crust as temperatures and pressure, the team was able to better understand how each changed.

The simulation results revealed a rather complex "dance" that led to the formation of the crust, the flow of the mantle and its movement that changed over millions of years.

The researchers found that about 20-40% of the surface is actually pulled by the flowing mantle, but this also means that up to 60% of the surface pushes the mantle into motion.

Scientists have found that these models also change over time, as thicker parts of continental plates are pulled by deeper currents, so that they are combined into larger continents. When supercontinents break and separate from each other, the sinking of plates in turn leads to the mantle flow.

Researchers say much of what is happening deep in the earth has serious implications for life on the surface, from earthquakes to volcanoes to the protective magnetic shield that protects us from the eruption of high-energy molecules from the sun, so we are at the mercy of the geology we are still working on.