62 



GEOLOGY 



crustal tension not pressure. They were called normal, be- 

 cause they were supposed to be the most common. The fact seems 



Fig. 33. 

 Fig. 33. A normal fault. 



Fig. 34. 



The overhanging side (to the left) has sunk; 

 a b= fault-scarp. 



Fig. 34. A thrust fault. The dotted lines at the left show the portion 

 which has been removed by erosion. The present surface is shown by the 

 line to the left of a. 



to be that. most faults of some regions are gravity faults, and most 

 of those of some other regions are thrust faults; but both types 

 may exist in the same region, though as a rule both types were not 



Fig. 35. A broken (now mended) and offset fence. That in the foreground 

 was formerly in line with the single length directly behind the man. 

 Near Stanford, Cal. (Photo, by Dudley.) 



