By recording faint blue-green twinklings in a huge subterranean detector, physicists have observed signatures of radioactivity deep within Earth. The new data enable the scientists to directly measure planet-wide quantities of the elements thorium and uranium, whose radioactive disintegrations generate about half of the planet's heat, according to previous estimates.
The power from those nuclear decays—which exceeds that of 10,000 nuclear power plants—propels many dynamic features of the planet, including crustal motions that give rise to earthquakes and volcanoes and the convection of softened rock within the planet's mantle.
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