Since the Earth formed about 4.5 billion years ago, our planet has been slowly cooling. Over millions of years, the Earth has gone from being covered in a deep ocean of magma to forming a brittle crust.
Since then, processes driven by heat from within the Earth have been critically important in protecting our world and allowing life to thrive. For example, the rotating dynamo and convection within the Earth is what generates its vast magnetic field. Similarly, mantle convection, tectonic activity, and volcanic activity are thought to help support life by stabilizing global temperatures and the carbon cycle.
What is the rate of cooling of the Earth’s interior?
Although the continuous cooling of the Earth’s interior is known, the question of how quickly and when its interior will solidify, and thus the end of geological activity, and possibly the Earth’s turning, has yet to be answered exactly. Rocks similar to Mars or Mercury.
Now, new research has revealed that this could happen sooner than previously thought. The study, conducted by professor at the Federal Polytechnic School of Zurich (ETH) in Switzerland, Motohiko Murakami and colleagues at the Carnegie Institution for Science, It was published in the magazine Earth and Planetary Science Letters.
Thermal conductivity of bridgemanite
These experts developed a laboratory measurement system that makes it possible to measure the thermal conductivity of a mineral known as bridgemanite, located at the boundary between Earth’s outer iron-nickel core and the lower mantle of the molten liquid above it. The measurements were made under the conditions of pressure and temperature prevailing inside the Earth.
“This measurement system allowed us to show that the thermal conductivity of bridgemanite is about 1.5 times higher than previously assumed,” Murakami says in an ETH statement.
This indicates that the heat flow from the core into the mantle is also greater than previously thought. The increased heat flow increases convection in the mantle and further cools the Earth.
It also causes the movement of tectonic plates to slow down faster than expected based on previous thermal conductivity values. Tectonics are responsible for convective movements in the mantle. According to the researchers, these changes appear to be leading to a cooling of the planet.
Postperovskite: higher thermal conductivity
The process can be accelerated. When it cools, bridgemanite turns into another mineral called bospirovskite, which is more thermally conductive and thus increases the rate of heat loss from the core to the mantle.
“Our results can give us a new perspective on the evolution of Earth’s dynamics,” Murakami said. “They suggest that Earth, like the other rocky planets Mercury and Mars, is cooling and sleeping much faster than expected.”
However, it cannot say how long it would take, for example, for convective currents in the mantle to stop. “We still don’t know enough about these types of events to determine their timing,” the planetary scientist said. According to the statement, it will first be necessary to better understand how convection works in the mantle in spatio-temporal terms, among other factors.
Edited by Felipe Espinosa Wang.