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Earth’s Interior Is Cooling “Much Faster Than Expected”



The evolution of our planet is a story about the cooling of the planet: It was 4.5 billion years ago that extreme temperatures prevailed on the young Earth's surface, and the entire planet was submerged beneath a thick layer of magma. Over millions of years, the planet's surface cooled, resulting in the formation of a brittle crust on the planet's surface. The enormous amount of thermal energy emitted by the Earth's interior, on the other hand, set in motion dynamic processes such as mantle convection, plate tectonics, and volcanic activity.


On the other hand, scientists are still unable to answer the questions of how quickly the Earth cooled and how long it may take for the ongoing cooling to bring the previously mentioned heat-driven processes to a halt.


The thermal conductivity of the minerals that form the Earth's core-mantle boundary is one possible explanation for this phenomenon.


In this boundary layer, the viscous rock of the Earth's mantle comes into direct contact with the hot iron-nickel melt of the planet's outer core, which is significant because it represents the first time that this has happened. A significant amount of heat could be flowing between the two layers, as indicated by the extremely steep temperature gradient between the two layers between the two layers. Bridgmanite constitutes the majority of the boundary layer's composition. Researchers, on the other hand, are having difficulty estimating how much heat this mineral conducts from the Earth's core to the mantle because of the difficulty in conducting experimental verification on it.


A sophisticated measuring system, developed by Motohiko Murakami of ETH and colleagues at the Carnegie Institution for Science, now allows them to determine the thermal conductivity of bridgmanite in the laboratory, under conditions similar to those found deep within the Earth's interior. They carried out the measurements in a pulsed laser-heated diamond unit with a newly developed optical absorption measurement system.


Using this measurement system, Murakami and his colleagues were able to demonstrate that bridgmanite has a thermal conductivity that is approximately 1.5 times greater than was previously assumed. According to this, heat transfer from the core to the mantle is greater than previously thought. Increased heat flow, in turn, promotes mantle convection and speeds up the Earth's cooling process as a result. According to previous heat conduction estimates, this could cause plate tectonics, which is propelled forward by convective motions in the mantle, to decelerate more quickly than previously anticipated.


In addition, Murakami and colleagues demonstrated that rapid cooling of the mantle alters the stable mineral phases at the core-mantle boundary, which was previously unknown. Bridgmanite cools and transforms into the mineral post-perovskite as a result of the cooling process. As a result, the researchers believe that once post-perovskite appears at the core-mantle boundary and begins to predominate, the cooling of the mantle will be accelerated even further, as this mineral conducts heat more efficiently than bridgmanite does.


"Our findings may shed new light on the evolution of the Earth's dynamics in the future, according to the researchers. They suggest that the Earth, like Mercury and Mars, is cooling and becoming inactive much more quickly than previously thought "Murakami provides an explanation.


His ability to predict how long it will take for convection currents in the mantle, for example, will be limited. "We still don't have enough information about these types of events to be able to predict when they will occur." First, it is necessary to gain a better understanding of the spatial and temporal dynamics of mantle convection in order to accomplish this goal. Additionally, scientists must understand how radioactive decay in the Earth's interior – which is one of the primary sources of heat – affects the dynamics of the mantle's composition and composition.

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