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: 
16.6 X10“ calories per second per gram for sediments; and 30X10“ 
for granite. This leaves 13.410 “ 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, 0.348 calories 
per year per square centimeter per 1,000 feet of thickness (ad, 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 



Fic. 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 ad (Fig. 14), above the base- 
ment complex at E] 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 gradient is independent of the thickness 
of the sediments. 
We can estimate the magnitude of the increment in the tempera- 
ture or the gradient by comparing the value, 0.348 calories per year 
per square centimeter per 1,000 feet of thickness of granite with the 
value 3.156 calories per year per square centimeter for a thin stratum 
556 
