The Thermal State of the Earth's Crust

Abstract

THE product of the rate of increase of temperature with depth in the earth's crust into the thermal conductivity of the surface rocks gives the rate of loss of heat from the interior. When allowance is made for the residual effects of the original heat, this gives a most important datum concerning the rate of generation of heat below, and hence, if the radioactivity of the rocks is known, to an estimate of the thickness of the radioactive layer. Hitherto it has been good enough, in discussions of this problem, to adopt mean values of the temperature gradient, the conductivity, and the radioactivity. It has now, however, become worth while to allow for variation of conductivity with depth, and to attend more to details in the vertical distribution of radioactive matter. When this is done as well as is at present possible, the agreement of the results with those obtained from the study of near earthquakes is practically perfect (Gerlands Beitrage z. Geophysik, 18, 1-29; 1927).