250 DISLOCATIONS OF STRATA 



strata on the two sides of the fault. The deep-seated beds, which, 

 on the upthrow side, are exposed by denudation, are, on the down- 

 throw side, carried down so far, that they do not reach the surface 

 at all, or, at least, not in the neighbourhood of the fault. Also, if 

 the hade of the fault is in the same direction as the dip of the 

 strata, repetition of outcrop may fail to occur. 



Fig. 106. — Effect of step faults in repeating outcrops. (Drawn from a model by 



Sopwith.) 



Dip faults have entirely different effects upon the outcrops from 

 those occasioned by strike faults, cutting across the strike of the 

 beds and interrupting their continuity. The outcrop of a given 

 stratum ceases abruptly at the fault line, and when found on the 

 other side, it is seen to be shifted a greater or less distance in the 

 direction followed by the fault plane. How such a horizontal 

 shifting is brought about by a vertical displacement is shown by 

 the model (Fig. 107). In I the model is shown as it was before 

 faulting, the black band representing a dipping stratum, say a coal 

 seam, seen in section on the side of the model, with the outcrop 

 appearing on its upper surface. In II the dislocation has oc- 

 curred, the upthrow side still standing as a fault scarp, while III 



