x TRACING FAULTS 1*9 



s evident thai along lines of great disloca- 

 tion there would naturally be a great deal of grinding 

 >f the Assart-walls. The broken rock m 

 the line of fault crumbles down more than the solid rock 

 ulc beyond it, or is more easily excavated and 

 removed So that whether on a cliff or on a flat 

 surface, the actual fault is apt to be concealed by 

 is. Then again, large faults often bring together 

 rocks of considerably different degrees of durability. 

 ess-lasting material decomposes, and its diMs goes 

 to cover the actual junction-line between the two forma- 



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Fio. is.-SMik of UM (X ! Nw Rd 

 (//X ou WMdMt, Britfd O 



tions. Another reason may be sought in the extensive 

 deposits of gravel, clay, or other superficial materials 

 i are spread over the surface of a country and 

 conceal the solid rocks. A line of fault is one of weak- 

 ness, presenting facilities for attack by the denuding 

 forces whereby it is hollowed out, so as to become a 

 receptacle for these superficial depc* 



I n regions where the solid rocks are not buried under 

 superficial accumulations, but come up tolerably bare to 

 the surface, examples not infrequently occur of faults 

 which, though not actually visible themselves, show their 

 presence and trend by their influence on the topography 

 of the ground. Sometimes their trend is marked by a 

 gash or hollow: at other times by a deflection in the 

 line of a valley or ravine. In many cases the rocks on 



B 



