While mankind is concerned about the Earth’s climate, scientists are looking farther afield and into the distant future: ETH researchers have demonstrated in the laboratory that the interior of planet Earth is probably cooling down much faster than assumed.
Experimental verification of the temperatures in the Earth’s interior is difficult for obvious reasons: the Earth’s core begins at a depth of almost 3,000 kilometers and has a temperature of plus/minus 6,000 Kelvin, which corresponds to around 5,000 to 6,000 degrees Celsius. The ETH scientists have therefore simulated the boundary layer between the Earth’s core and mantle in the laboratory.
This boundary layer is relevant because here the viscous mantle rock is in direct contact with the hot iron-nickel melt of the outer core of the earth. The temperature gradient between the two layers is very large, so that a lot of heat can potentially flow here. The boundary layer is mainly formed from the mineral bridgmanite.
ETH professor Motohiro Murakami and colleagues from the Carnegie Institution for Science have developed a sophisticated measuring system that makes it possible to measure the thermal conductivity of bridgmanite in the laboratory, under the pressure and temperature conditions that prevail inside the earth.
“With this measurement system, we were able to show that the thermal conductivity of bridgmanite is about one-and-a-half times higher than previously thought,” Murakami said. This allows the conclusion that the heat flow from the core to the mantle is higher than previously thought. This can lead to the plate tectonics, which are kept going by the convection movements of the mantle, flagging faster than previously thought.
“Our results could give us a new perspective on the evolution of Earth’s dynamics. They suggest that Earth, like the other rocky planets Mercury and Mars, is cooling and becoming inactive much faster than expected,” Murakami explained.