Why Is the Earth So Hot? Radioactivity Is Half the Answer
About half of the heat that the earth generates itself is due to radioactive decay, scientists have concluded. While a recent study published in Nature Geoscience by the Japan-based KamLAND collaboration (which runs an important radiation detector) has shed light on processes deep within the bowels of the planet, it still leaves open the question of what's generating the other half?
"One thing we can say with near certainty is that radioactive decay alone is not enough to account for Earth's heat energy," Stuart Freedman of the U.S. Department of Energy's Berkeley Lab said in a statement. "Whether the rest is primordial heat or comes from some other source is an unanswered question. This is what's called an inverse problem, where you have a lot of information but also a lot of complicated inputs and variables."
The earth continuously generates about 44 terawatts of heat, according to measurements from approximately 20,000 boreholes all over the world. It's this heat, and how it affects substances in the core and mantle, that leads to the gradual motion of continents and the creation of the earth's magnetic field. Exactly how this heat is generated has been difficult to measure, since the inner layers of the planet can't be probed directly.