Early geophysical papers of the Early geophysical papers of the Society of Exploration Geophysicists earlygeophysical00soci Year: 1947 34 C. E. VAN ORSTRAND flow of heat from rocks that have been displaced towards the surface of the earth. Joly's (37) values for the heat developed by radioactivity are: ~14 calories per second per gram for sediments; and 30X10-14 for granite. This leaves io~14 calories per second per gram as a source of excess heat in the granite. This estimate is based on the ac- tivity of thorium and uranium. Carrying out the calculations, we find for the exces
Early geophysical papers of the Early geophysical papers of the Society of Exploration Geophysicists earlygeophysical00soci Year: 1947 34 C. E. VAN ORSTRAND flow of heat from rocks that have been displaced towards the surface of the earth. Joly's (37) values for the heat developed by radioactivity are: ~14 calories per second per gram for sediments; and 30X10-14 for granite. This leaves io~14 calories per second per gram as a source of excess heat in the granite. This estimate is based on the ac- tivity of thorium and uranium. Carrying out the calculations, we find for the excess heat developed in the granite, the value, calories per year per square centimeter per 1,000 feet of thickness (ab, Fig. 14) of granite standing above the general level of the basement floor. To make an accurate calculation, it is necessary to assume a great num- ber of heat sources and draw the curves for each source as shown in Figure 12. The sum of all of the ordinates at any point represents the Fig. 14. -Sketch showing cross section of anticline. temperature at that point. It will suffice for our purpose to assume that all of the heat is generated in one plane, or thin stratum; and since heat has been developed in granitic rocks since their solidifica- tion, it follows that the increment in temperature is represented by the straight line oa in Figure 12. The slope of the line oa is determined by the thermal constants of the rocks and the rate of generation of heat. Hence, it is independent of the depth to the heat source. This means that a granitic mass of height ab (Fig. 14), above the base- ment complex at El Dorado, Kansas, where the depth to the granite is only 3,000 feet, produces the same change in the gradient, other conditions being the same, as at Long Beach where the granitic mass may be buried to a depth of 20,000 feet. In other words, ridges in the basement floor are reflected by increased temperature gradients at the surface, and the change in the gr
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