A superior limit to the age of the earth's crust

Source abstract

Abstract Considerations based upon radio-activity have often been employed to obtain estimates of the ages of minerals, and of the duration of geological time; but it does not appear to have been remarked that similar arguments can be used to assign a maximum age for the existing crust of the Earth. Uranium is continually disintegrating with a “half period” of 5 x 109 years, and no process is known by which the supply can be renewed. It is probable that the proportion of this element in the Earth’s crust was greater formerly than at present—the computed amount necessary to account for the survival of that which now exists increasing exponentially with the time interval, a thousand fold in ten half periods and a million fold in twenty.