Cutaway Earth (image) DOE/Lawrence Berkeley National Laboratory Caption A main source of the 44 trillion watts of heat that flows from the interior of the Earth is the decay of radioactive isotopes in the mantle and crust. Scientists using the KamLAND neutrino detector in Japan have measured how much heat is generated this way by capturing geoneutrinos released during radioactive decay. Credit Lawrence Berkeley National Laboratory Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.