EXAMPLES OF INITIAL AND YOUNG FAULT SCARPS 197 



fresh fault scarps, from 20 to 50 feet high, that cross alluvial cones and 

 cut embankments and terraces" (449). Some of the greater fault scarps, 

 "forming the mountain faces, are in many instances nearly vertical walls, 

 hundreds of feet in height, of such recent date that they have scarcely 

 been notched by erosion, and have but small, if any, alluvial cones at 

 their bases" (436). No details are given as to the special forms devel- 

 oped in the more elaborately dissected scarps. One of my own papers 

 refers to part of the same district (h, '03, 164-). Koto ('93) has de- 

 scribed and figured an extraordinary scarp in Japan produced by the 

 earthquake of 1891. Tarr and Martin ('06) have done the same for 

 scarps in Alaska produced by the earthquake of 1899. 



Mature Forms on faulted Structures 



In the cases here figured the early post-faulting changes are, in figure 

 1 D, chiefly the retreat of the scarp by weathering and the incipient dis- 

 section of its face by short, wet-weather streams consequent on the fault- 

 ing; or, in figure 2 I), by the much more rapid incision of the scarp face 

 by the uplifted streams that flow down from it; in both these cases 

 the burial of the scarp base under alluvium; or, in a later stage of figure 

 '"'>. the concealment of parts of the scarp in the alluvial deposits of small 

 lakes ponded by the rise of the uplifted mass across the valleys of pre- 

 existent streams that flow toward the uplift. The later or mature post- 

 faulting changes will include the further retreat of the scarp, and with 

 this the development of various details in the scarp face by the subconse- 

 quent or subsequent modification of its initial form, as already men- 

 tioned ; also the deeper incision of valleys in the uplifted mass either by 

 new consequent streams or by revived pre-existent streams; but be it 

 noted that the young or submature valleys here referred to must always 

 be described as modifying the pre-faulting surface in which they are in- 

 cised, as long as the remnants of the earlier surface constitute a signifi- 

 cant part of the landscape. The pre-faulting surface must be explicitly 

 included in the description of the faulted district as long as there are 

 any manifest signs of it. 



It is evident that as long as waste is abundantly washed down from 

 the uplifted mass no continuous stream and valley are to be expected 

 along the fault line, even in the more advanced stages of the new cycle, 

 unless highly specialized initial conditions have favored their develop- 

 ment; and as such specialized conditions must he rare, the occurrence of 

 consc(pu ni streams and valleys along fault lines in a youthful or mature 

 stage of (he cycle introduced by 1 he faulting must also he rare. Heme 



