Radioactive decay responsible for half of Earth's geothermal heat

[Piwoslaw]

Earth's original heat store still burning strong - Nature

Radioactive decay is responsible for about half of the heat coming from the bowels of the Earth, suggesting that the remaining 50% is the primordial heat left over from when the Earth first formed.

Most of the heat given off by our planet – estimated to be about 174 petawatts (10^15 W) – first came from the Sun. But about 44 terawatts (10^12 W) of that is geothermal energy (pdf).

Shows how much we can suck up, and how fast. Gotta get that GSHP before someone else steals my heat!