288 ELEMENTARY GEOLOGY 
to strains and stresses, they sometimes break or 
fault, and move on one side of the plane of break- 
age, or as it is called, the fault plane (Fig. 170). 
Fic. 168. 
Section of unsymmetrical and overturned folds. 
Probably when rocks are bending and folding deep 
down below the surface of the earth, they are often 
Fic. 169. 
Photograph of crumpled rock. 
being broken and faulted at the very surface. Cer- 
tainly there are some folds which on one of their 
