Since the Earth was formed about 4 years ago, 500 million years, 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 inside the Earth have been extreme importance in protecting our world and allowing life to flourish.
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 the constant cooling of the interior of the Earth is known, the question of how fast it cools and when its interior will solidify has not yet been answered exactly, and therefore the end of the geological activity, possibly turning our planet into a barren rock, similar to Mars or Mercury.
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 journal Earth and Planetary Science Letters.
Thermal conductivity of bridgmanite
These experts have developed a laboratory measurement system that allows the thermal conductivity of a mineral known as “bridgmanite”, located in the boundary between Earth’s iron-nickel outer core and the lower mantle of molten fluid above it.
The measurements were made under the pressure and temperature conditions prevailing inside the Earth.
“This measurement system allowed us to demonstrate that the thermal conductivity of bridgmanite is about 1.5 times larger than previously thought”, says Murakami in an ETH statement.
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.
Posperovskite: 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 Earth dynamics,” Murakami said. “They suggest that the Earth, like the other rocky planets Mercury and Mars, is cooling and going dormant much faster than expected.”
However, he can’t say how long it will take, for example, in stopping convection currents in the mantle. “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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