FOLDING AND CRUMPLING OF STRATA 



molten material, and on this the crust is sup- 

 ported. It cannot be said to " rest " on the 

 deeper matter, for it is always, though very, 

 very slowly, shifting and crumpling. Con- 

 sequently, according to the height and depth of 





1^: 



Fig. 35. — Strata of the cliff at Lyme Regis, 

 by Messrs. Dollnian Bros. 



Photographed 



the folds of the crust, we find that deeper, even 

 very deep-lying strata may be brought to the 

 surface, and as the upraised folds get worn away 

 by sea and rain and rivers, the deepest layers 

 may be exposed on the surface. Thus it is 

 that we are able to examine the oldest rocks 



51 



