Thursday, May 26

Earth’s interior is cooling faster than expected: study

Since the Earth formed about 4.5 billion years ago, our planet has been slowly cooling. Over millions of years, it went from being covered by a deep ocean of magma to forming a brittle crust.

Since then, processes driven by heat from within the Earth have been extremely important in protecting our world and allowing life to thrive.

For example, the rotating and convective dynamo inside the Earth is what generates its vast magnetic field. Similarly, mantle convection, tectonic activity, and volcanism are thought to help support life by stabilizing global temperatures and the carbon cycle.

At what rate is the interior of the Earth cooling?

Despite of constant cooling of the Earth’s interior is known, the question of how fast it cools and when its interior will solidify, and therefore the end of geological activity, possibly turning our planet into a barren rock, similar to Mars or Mercury, has not yet been answered exactly.

Now, new research has revealed that this could happen sooner than previously thought. The study was carried out by the professor at the Federal Polytechnic School of Zurich (ETH), in Switzerland, Motohiko Murakami and his colleagues at the Carnegie Institution for Science, has been published in the magazine Earth and Planetary Science Letters.

Thermal conductivity of bridgmanite

These experts have developed a laboratory measurement system that makes it possible to measure the thermal conductivity of a mineral known as “bridgmanite”, located on the boundary between the Earth’s outer core of iron and nickel and the lower mantle of molten fluid that is find on him.

The measurements were made under the pressure and temperature conditions prevailing inside the Earth.

“This measurement system allowed us to show that the thermal conductivity of bridgmanite is about 1.5 times higher than previously assumed,” Murakami states in an ETH statement.

While surface and atmospheric temperatures fluctuate over the eons, Earth's molten interior has been cooling all this time.

This suggests that the heat flux from the core to the mantle is also greater than previously thought. The increased heat flux increases mantle convection and increases the cooling of the Earth.

It also causes plate tectonics to slow down faster than expected based on previous heat conduction values. Tectonics is responsible for the convective movements of the mantle. According to the researchers, these changes seem to lead to a cooling of the planet.

Postperovskite: higher thermal conductivity

And the process could be accelerating. When cooled, bridgmanite transforms into another mineral called posperovskite, which is even more thermally conductive and therefore would increase the rate of heat loss from the core to the mantle.

“Our results could give us a new perspective on the evolution of the dynamics of the EarthMurakami said. “They suggest that Earth, like the other rocky planets Mercury and Mars, is cooling and becoming inactive much faster than expected.”

However, it cannot say how long it will take, for example, for convection currents in the mantle to stop. “We still don’t know enough about this type of event to pinpoint its timing,” said the planetary scientist.

According to the statement, it would first be necessary to better understand how mantle convection works in spatial and temporal terms, among other factors.

With information from DW.

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