On the estimation of temperatures at moderate depths in the crust of the Earth

The modern deep well makes it possible to determine the temperatures of the rocks to depths exceeding two miles, and the rock‐samples obtained at these great depths enable the geologist to estimate the depths to the deeply buried basement‐rocks to a rather high degree of precision. The latter estimates are now being supplemented to a certain extent by the precision‐measurements of geophysicist, so that reliable data seem to be assured even in those areas in which the basement rocks are not reached by the drill. With these two sources of information at our disposal—accurate temperature‐measurements and reliable estimates or measurements of depths to bed‐rock—it should be possible to construct a rather accurate subsurface map showing the temperatures on the boundary‐surface between the sedimentaries and the basement floor. In this paper it is proposed chiefly to outline the method of procedure by making some rough calculations of the temperatures at great depths for a few locations in the United States and for one location near Carnarvon, Cape Province, South Africa.