19(3 W. M. DAVIS NOMENCLATURE OF SURFACE FORMS 



have taken place since and on account of submergence, just as he fails to 

 describe the landscape that existed before submergence; yet it is nearly 

 always the case that along a certain line of the pre-submergence forms — 

 namely, the new shoreline — certain post-submergence features in the 

 form of bayheacl deltas and headland cliffs have been more or less devel- 

 oped. Likewise, the explorer who describes a district as traversed by a 

 fault usually fails to make explicit statement of the changes that have 

 taken place since and on account of faulting, as well as of the prefault- 

 ing forms, in which the post-faulting changes have occurred. The estab- 

 lishment of some systematic method for the explanatory description of 

 J and forms will go far toward correcting these omissions; in my own ex- 

 perience the method of "structure, process, and stage," here outlined in 

 its relation to forms developed on faulted structures as well as on other 

 structures, has repeatedly proved helpful in field work, and it is there- 

 fore the more confidently recommended to others. 



Examples of initial and young Fault Scarps 



Various reports of the United States Geological Survey on the Great 

 Basin province furnish us with the best described examples of initial and 

 young fault scarps in this country, the initial scarps being in most or all 

 cases the result of renewed movement on earlier faults. Several strik- 

 ing cases of earlier faults are described by Russell ('84,) in southern 

 Oregon, where the prefaulting mass was a broad plain of lava flows rest- 

 ing unconformably on a floor of more or less eroded crystalline rocks, 

 and where a series of north-south faults has broken the mass into long 

 blocks which have suffered strong differential displacement, the upraised 

 block-edges being now more or less carved into mountainous ridges. 

 while the relatively depressed areas are buried under plains of alluvium. 

 Some of the scarps are "slightly scarred by erosion ;" others are elabo- 

 rately carved. The fault along the eastern base of one of the largest 

 mountain blocks is about 100 miles in length, "with a displacement 

 where the mountains are highest of not less than 5,000 or 6,000 feet;" 

 and at one point "there has been a very recent movement along the old 

 fault. The irregular scarp in alluvium formed by the recent displace- 

 ment is fresh and unclothed with vegetation, and may be traced for sev- 

 eral miles at the immediate base of the mountains, defining the boundary 

 between swampy meadows [on the east] and solid rock [on the west). 

 The hade of the recent fault is to the eastward at a high angle, while the 

 throw, as shown by the fresh scarp, is from 20 to 50 feet" (445). An- 

 other line of displacement "is marked by numerous hot springs and by 



