150 



OUTLINES 



some dislocation. It will not, however, of itM-lf he suf- 

 ficient to prove the existence of a fault, for unexpected 

 local twists and severe plication sometimes occur where, 

 though the rocks must have been subjected to intense 



FIG. 48. Shales contorted by a Ian- 



lateral compression, they have not actually been fractured. 

 On a small scale, the most tumultuous contortion of soft 

 strata may often be seen as the result of a landslip. In 

 Fig. 48, for example, a set of dark shales lying under a 

 thick sandstone have been crushed up by slips of the 

 heavy overlying rock, yet the ruin has been so well 

 concealed by vegetation that a careless observer might 

 suppose the lower twisted beds to be much older than, 



