Experimental study of the interior of the planet is difficult for quite obvious reasons: the core begins at a depth of about 3000 km, with a temperature of 5-6 thousand degrees Celsius. So ETH experts simulated the layer between the core and the mantle under laboratory conditions.
This boundary layer is important because the viscous sheath here comes in direct contact with the hot iron and melts the nickel on the outside of the core. The temperature gradient is very large between the two layers, so there is a high heat flux here. The boundary layer consists mainly of a mineral called bridgemanite (a very dense magnesium ferric silicate).
ETH Professor Motohiro Murakami and colleagues at the Carnegie Institution for Science have developed a sophisticated measurement system that allows bridgemanite to measure the thermal conductivity of bridgemanite in the laboratory at the pressure and temperature prevailing deep in the Earth.
“Using this measurement system, we were able to show that the thermal conductivity of bridgemanite is one and a half times higher than previously assumed,” Murakami said. From this it can be concluded that the heat flow from the core to the shell is higher than previously thought.
This could lead to the movement of tectonic plates, which is maintained by convective mantle movements, to weaken faster and slower than previously assumed.
“Our results shed new light on the changing dynamics of the Earth. They indicate that Earth, like other rocky planets such as Mercury and Mars, is cooling and becoming inactive much faster than expected,” Murakami said.
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