IMAGINARY EXAMPLE OF RESEQUENT FAULT-LINE SCARPS 213 



eral hundred feet without faulting, and thereupon again eroded; the 

 northwestern district being now in early or late mature stages of the 

 cycle thus introduced, while all the southeastern district of weaker sand- 

 stones has reached a. late mature or almost old stage, as indicated by its 

 low, subdued hills, separated by broad-floored, wide-spaced, shallow val- 

 leys of typically inseqiient pattern; and the fault boundary between the 

 two districts being marked by a dissected resequent fault-line scarp along 

 the border of the crystalline uplands and by a series of resequent fault- 

 line scarps facing southeast and obliquely truncating the sandstone 

 ridges; but the fault is topographically obliterated where the subsequent 

 shale valleys open on the southeastern lowland. If such a description be 

 accompanied by a diagram, like figure 5, the essential features of the dis- 

 trict concerned may be easily conceived. 



The essence of this imagined physiographic description is that it at- 

 tempts to introduce everything that is relevant and nothing that is irrele- 

 vant to a clear comprehension of the surface features in the district con- 

 cerned. The names of geological formations are intentionally omitted, 

 because they do not aid in conceiving the visible landscape; but if the 

 physiographical description were intended as an introduction to a geo- 

 logical report, geological formation names might, of course, be men- 

 tioned at the outset. The attitude of the strata, often regarded as a 

 purely geological matter by geographers of the empirical school, is really 

 a very serviceable physiographic factor, because it enables the reader 

 easily to conceive certain systematically associated features which would 

 otherwise have to be described one by one. The fault, the two cycles of 

 erosion that have followed it, and the uplift without faulting that sepa- 

 rated them are all manifestly of service in leading the reader to picture 

 what the writer has seen ; but these factors, like all others relating to 

 past conditions and events, are not introduced with the object of narrat- 

 ing the history of the district — that would be pure geology — but with the 

 object of setting forth its present form, and that is proper physiography. 



Forms produced on faulted Structures by other than normal 



Processes 



All the foregoing discussion has been under the postulated action of 

 normal erosional processes, — that is, weather and running water. The 

 other chief processes — solvent action of water, waves and currents; gla- 

 ciers, and wind — also deserve treatment in their proper place: bill such 

 treatment may for the present he postponed until more examples of 

 faulted structures acted on by these various processes come to be known. 



