Thermal History of the Earth.

Abstract

As part of a discussion of thermal phenomena in the Earth when convection is taken into account, a study of core formation is made in order to ascertain whether the energy released in this process is significant at the present time. It is also a necessary preliminary to deciding whether mantle convection at the present time is thermal in origin. A new method is developed for computing the energy released by core formation, subject to certain restrictions on the changes of entropy in the Earth. Several models for the kinetics of core formation are discussed, none of which is wholly satisfactory. By considering observational evidence that indicates non-hydrostatic stresses in the Earth it is inferred that at the present time core formation is virtually complete and that the energy released by this process is hundreds of times less than the probable radioactive heat generation. From this we conclude that as a first approximation the present convection in the large scale Earth may be understood as the effect of thermally-generated buoyancy forces.