Earth’s interior is cooling faster than expected, study notes

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Studying a mineral named bridgmanite commonly found between Earth’s core and mantle, researchers have suspected that Earth’s inner heat is dissipating sooner, making it cool faster than expected.

About 4.5 billion years ago, the surface of young Earth was covered by magma and over the years, the planet’s surface has cooled to form the outer crust. However, there’s still enormous thermal energy in Earth’s core and mantle which governs plate tectonics, earthquakes, and volcanism.

Researchers are yet to find answers about the rate at which Earth cooled and whether there could be a complete cooling of the planet’s interior.

The international team measured the radioactive thermal conductivity of bridgmanite in the laboratory. The core-mantle boundary of Earth is rich in bridgmanite.

“Radiative thermal conductivity is one of the fundamental heat conduction mechanisms. Since it is strongly dependent on the colour (opaqueness), we applied optical absorption measurement of the specimen (bridgmanite) under high-pressure and high-temperature conditions corresponding to the Earth’s core-mantle boundary region,” explained lead author Motohiko Murakami from ETH Zürich, Switzerland in an email to The Indian Express.

The results showed that the thermal conductivity of bridgmanite was about 1.5 times higher than assumed. These findings also suggest that other rocky planets may be cooling and becoming inactive faster than expected.

The paper recently published in Earth and Planetary Science Letters adds that this cooling can weaken many tectonic activities.

When asked if this will lead to lesser earthquakes and volcanic eruptions in the future, Dr. Murakami said: “Yes, I believe so. Since all the tectonic activities (earthquakes, volcanism, and plate tectonics) can be ultimately driven by the thermal energy released from the deep Earth’s interior through mantle convection, the dynamics of the Earth’s mantle and the surface tectonic activity should be more or less synchronised.”

However, he adds that it is challenging to track how long it will take for the cooling to happen which will ultimately stop the convection currents in the mantle.

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