262 C. A. Cotton — Block Mountains in New Zealand. 



lower parts fault-line scarps, though where the displacement 

 on the faults is considerable, they are true fault scarps in their 

 upper parts. 



When faulting occurs in a region where a weak cover over- 

 lies a resistant undermass, and the base of the resulting fault 

 scarp is at a considerable height above base-level, removal of 

 the covering strata at the base of the scarp may be going on while 

 movement is in pi ogress. If such removal is prevented bj an 

 abundant supply of waste spread out on the covering strata in 



Fig. 7. 



Fia. 7. Diagram of the deyelopmeiit of a composite fault scarp, in its 

 Tipper part a fault scarp and in its lower part a fanlt-line scarp. 



the form of fans or a piedmont alluvial plain, after movement 

 ceases degradation will soon take place. Thus a fault-line 

 scarp will be exposed below and continuous with the already 

 dissected fault scarp, the two constituting a single morphologi- 

 cal feature which may be called a composite fault scarp. 



During the early stages of stripping of the fault surface, the 

 ravines l3y which the upper portion of the composite fault 

 scarp is already dissected may have cut nearly to or perhaps 

 below the surface of the undermass on the down-throw side of 

 the fault. If so, these ravines will divide the fault-line por- 

 tion of the scarp before it is exposed into sections that will be 

 downward prolongations of the facets of the upper scarp. In 

 some cases these lower fault-line portions of facets may be 

 recognized by their steepness (see fig. 7 C) ; but the facets will 

 soon dwindle and remnants of the fault-line portion only be 

 left (see hg 7 D). 



Where there is a continuous covering of vegetation, soil 

 creep plays an important part in producing convexl}^ rounded 



