How many years are required for a chunk of thermally insulated granite to increase its temperature by 500 C.?

radioactive decay of isotopes in granite & other rocks in earth's interior provides sufficient energy to keep the interior molten, to heat lava & provide warmth to natural hot springs. this is due to an average release of about .03 J of energy per kilogram of granite every year. ume that the specific heat capacity of granite is 800 J per kg per Celsius degree. consider a 1 kg block of granite.