PHYSICAL CHANGES OF THE OUTER SHELL 



69 



dition. In such a fold we find a definite axis. At the sides, 

 the edges of various strata are nearly parallel to this axis. 

 These edges are outcrops, and their shapes depend on the 



FIG. 50. Diagram illustrating the difference between strike and outcrop. 

 How has the cutting of the valleys affected (1) the outcrop, and 

 (2) the strike ? What would be the effect, if the beds (1) dipped to the 

 right, (2) were vertical ? 



attitude of the underlying beds and upon the configuration of 

 the hills and valleys (Fig. 50). The strike of the beds is the 



FIG. 51. Stereogram of one end of a pitching fold, the top of which has 



been cut off. 



