Earth’s core ‘cooling faster than thought’

The transfer of core heat to the surface can be best observed by volcanic activity, such as the eruption of Eyjafjallajockull in Iceland in 2010. Keystone / Vilhelm Gunnersson

The Earth may be losing its internal heat at a faster rate than previously estimated, according to scientists at the federal technology institute ETH Zurich.

Researchers devised a laboratory experiment for measuring the amount of heat being radiated from the planet’s core of molten iron and nickel to the surface.

The heat is conducted through a mineral in the Earth’s mantle, called bridgmanite, which comes into direct contact with the outer core. The transfer of heat powers volcanic activity and the movement of tectonic plates.

The experiment employed an “optical absorption measurement system, in a diamond unit heated with a pulsed laser”, to simulate bridgmanite’s thermal conductivity at a depth of 3,000 kilometres at temperatures of up to 6,000 degrees Celsius.

“This measurement system let us show that the thermal conductivity of bridgmanite is about 1.5 times higher than assumed,” said ETH Zurich professor Motohiko MurakamiExternal link.

“Our results could give us a new perspective on the evolution of the Earth’s dynamics. They suggest that Earth, like the other rocky planets Mercury and Mars, is cooling and becoming inactive much faster than expected.”

The process could also be magnified as bridgmanite turns into post-​perovskite when it cools – a mineral that conducts heat more efficiently than bridgmanite. The researchers believe that the cooling of the Earth will be accelerated when post-​perovskite becomes the dominant mineral in the mantle.

But the results are not enough to pinpoint when the Earth may cool to the point that tectonic plates stop moving. Other factors are also at play, such as the way radioactive elements decay in the Earth’s interior.

The research was carried out between ETH Zurich and the Carnegie Institution for Science in the United States.