SECOND-CYCLE FORMS ON FAULTED STRUCTURES 207 



systematically connected with surface streams must evidently be due to 

 stream action and not to the original movement of the fault. Further, 

 it should be noted that in an advanced stage of second-cycle erosion on 

 a mass of complicated structure, newly developed fault-line scarps must 

 be discontinuously developed, according to the opportunity that the 

 weaker structures offer; they must always rise on the side of the more 

 resistant rocks and overlook the area of weaker rocks; they must there- 

 fore here be of resequent, there of obsequent aspect, as in the cases of 

 figures 2 G and 4 B, above referred to. Evidently so systematic a rela- 

 tion of scarp aspect to rock resistance must be the result of erosion, not 

 of faulting; hence if a fault-line scarp were mistaken for a fault scarp, 

 the uplift might be thought to be on the wrong side of the fault line. 



In a second cycle, fault-line valleys will be developed by the action 

 either of revived consequent streams or of subsequent streams working 

 along the shattered zone of a fault bordered on both sides by rocks of 

 significant resistance. Thus we see once more that, as far as valleys 

 following fault lines are concerned, they may be developed either by 

 revived or by new subsequent streams in a second cycle, succeeding any 

 advanced stage of the cycle introduced by faulting. If the rare occur- 

 rence of consequent fault valleys as above set forth is now recalled, it 

 will appear that most valleys associated with faults are likely to be of 

 subsequent origin. They are not due directly to faulting alone, but to 

 erosion working on a faulted structure. They are not initiated by the 

 faulting movement, but first take the form of valleys long after the fault- 

 ing has ceased. Hence they should be called by some special name, such 

 as fault-line valleys, as here suggested, and the term fault valleys should 

 be limited to valleys produced by erosion closely consequent on faulting. 



Fault-line scarps in the early stages of a second cycle following an 

 advanced stage of a previous cycle, and traversing a district of gently 

 inclined strong and weak strata, will be associated with a peculiar and 

 significant arrangement of ridges or of cuestas that deserves special men- 

 tion. The advanced erosion of the first cycle will have resulted in pro- 

 ducing offsets in corresponding ridges or cuestas, so that their ends will 

 abut against the fault line some distance apart, as in figure I B. If old 

 age he reached, the soil belts will he offset along the fault line. When 

 renewed erosion of the weaker si rain in the second cycle, introduced by 

 uplift without renewed faulting, develops discontinuous fault -line scarps 

 close along the fault line, their small retreat mighl be taken— especially 

 by observers who are not critical in distinguishing fault-line scarps from 

 fan 11 scarps — to mean thai the faull is of recent date: but the strong off- 



