22 



GEOLOGY. 



axis of a syncline and toward it in the axis of an anticline, 

 the curvature of some of the trap ridges in New England. 



This explains 



Fig. 329. 



Fig. 330. 



Fig. 329. — Diagram illustrating the effect of a dip fault on outcrops where the struc- 

 ture is like that shown in Fig. 326, after the faulted surface has been reduced to 

 a plane. The south side was the upthrow side. 



Fig. 330.— Same as Fig. 329, except that the opposite side is the upthrow side. 



5. Where the deformed strata are affected by faults, the curved outcrops 

 maybe repeated in parallel positions (strike faults). They may be offset with- 



Fig. 331. 



Fig. 332. 



Fig. 33t. — Effect of an oblique fault on the outcrop of beds, where the structure before 

 faulting was that shown in Fig. 326. The south-southeast side was the up- 

 throw side, and the diagram represents the surface after it has been reduced to a 

 plane, subsequent to the faulting. 



Fig. 332. — Same as the last, except that the fault was greater, and the north-north- 

 west side the upthrow side. 



out gap or overlap (dip faults), or they may be offset with overlap or gap (oblique 

 faults) . 



Before base-leveling has been affected, but in an advanced stage of erosion» 

 each layer of resistant rock, such as the trap, constitutes a ridge. The ridge 



