Researchers at ETH Zurich have been able to demonstrate how well a mineral that can be found at the boundary between the Earth’s core and mantle successfully conducts heat. This discovery led to a growing body of evidence, suggesting that the Earth is cooling faster than previously believed.
In light of the findings, scientists may have a new perspective on the evolution of Earth’s dynamics. Researchers believe Earth is cooling and becoming inactive faster than expected, along with Mercury and Mars.
(Photo : Getty Images)
The Evolution of Earth
The Earth’s history and its evolution is a tale of cooling. A deep ocean of magma covered the Earth’s surface 4.5 billion years ago, when the planet was still very much in its infancy.
According to Phys.org, the planet’s surface cooled over millions of years, resulting in a brittle crust. Massive amounts of heat from deep within the Earth’s core, on the other hand, set in motion a number of dynamic processes such mantle convection, plate tectonics and volcanism.
The Earth’s cooling rate and how long it will take for the previously described heat-driven processes to come to a standstill are still open topics.
The thermal conductivity of the minerals that comprise the Earth’s core-mantle boundary may hold the key to the answer.
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Thermal Conductivity of Bridgmanite
In the Earth’s core-mantle boundary layer, the Earth’s mantle’s viscous rock meets the hot iron-nickel melt of the planet’s outer core. This area has a high potential for heat movement due to the sharp temperature difference between the two layers.
Bridgmanite is the primary mineral in the border layer. Research into how much heat this mineral conducts from the Earth’s core to its mantle is difficult because experimental verification is extremely difficult.
Since then, ETH Professor Motohiko Murakami and his colleagues from the Carnegie Institution for Science have developed a sophisticated measuring system that allows them to test the thermal conductivity of bridgmanite in a laboratory under the same pressure and temperature conditions that exist deep within the Earth itself.
An optical absorption measurement device in a diamond unit heated by pulsed laser was employed for the measurements.
Bridgmanite’s thermal conductivity was 1.5 times higher than predicted thanks to this measurement system, according to Murakami. Due to this data, the heat flow from the core to the mantle may be more than previously anticipated.
The Earth’s cooling process is accelerated by increased heat flow, which in turn enhances the convection of the Earth’s mantle. Plate tectonics, which is driven by the mantle’s convective motions, may slow down as a result, which would be a surprise given past heat conduction estimates.
(Photo : Pixabay)
Understanding How Mantle Convection Works
Rapid cooling of the mantle, as demonstrated by Murakami and colleagues, alters the stable mineral phases near the core-mantle border. Bridgmanite crystallizes into post-perovskite when allowed to cool.
Mantle cooling could speed up much more if post-perovskite begins to dominate at the core-mantle barrier, say the researchers, because it transmits heat even better than bridgmanite.
When convection currents in the mantle are no longer a problem, scientists cannot tell how long it will take. It’s difficult to pinpoint the exact timing of these kinds of events because scientists don’t know enough about them yet.
A deeper understanding of how mantle convection works spatially and temporally is required before this can be accomplished. It’s also critical that researchers figure out exactly what’s going on with radioactive decay in Earth’s interior, which is a major source for heat.
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