Potassium and the Heat of the Earth

Abstract

IT has been widely recognised that the disintegration of the uranium and thorium in rocks has exerted a profound and probably controlling influence on the earth's thermal history. Hitherto, however, it has not been realised that potassium as an emitter of radiothermal energy is in the aggregate of the same order of importance as uranium or thorium. This surprising result has emerged in the course of a joint inquiry into the geological significance of the radioactivity of potassium and rubidium. The latter element is negligible geologically on account of its extreme rarity, despite the fact that its total activity is greater than that of an equal amount of potassium. Nevertheless, we have included rubidium in our discussion, since measurements of the activity of potassium have usually been compared with those obtained with rubidium, and our preliminary estimate of the amount of heat generated by the potassium in rocks depends on that comparison.