THE STRENGTH OF THE EARTH'S CRUST 



735 



lateral pressure. Fig. i6 shows that uncompensated features with 

 a wave-length up to 200 km. impose the stresses almost wholly 

 within the lithosphere, taking this as limited by a depth of 122 km. 

 The crust increases in strength to a certain maximum, perhaps 

 from 10 to 30 km. deep, as shown by the experiments of Adams. 



Surface of ihe earth 



lookm." 



Mean/depth of compensahon 



for uniform disfribufion. 



200 km. 



Scale for sfresses jaeiuh. 



Fig. 16. — Diagram showing the distribution in the crust of stress-differences 

 due to parallel uncompensated harmonic mountains and valleys: A, curve showing 

 relative magnitude and depth of stress-differences corresponding to a distance of 400 

 km. between crests of parallel mountain ranges. B, curve showing the same for a 

 distance of 200 km. between crests of parallel mountain ranges. 



At greater depth the strength, according to the theory developed in 

 Part VI, and as recognized by Love and others in treating of isos- 

 tasy, is to be regarded as decreasing and passing by transition into 

 the asthenosphere. Consequently it is seen that the distribution 

 of stress imposed by a wave-length of 200 km. conforms well to 

 the distribution of strength, the greatest strain coming on the 

 strongest part. 



