TYPES OF COASTAL SLOPES 429 



Considered as a sea-cliff, this scarp must be supposed to have been 

 cut upon a gentler slope during its elevation from a submarine position. 

 The work accomplished by the waves would much exceed that recorded 

 upon the coastal front of the San Luis range, which lies nearly contigu- 

 ous and exposed to the same attack. Marked terraces might be looked 

 for as records of intermittent elevation, whereas only discontinuous and 

 very local benches occur. The execution of such a task of cliff-cutting 

 would require long time, the lapse of which should be recorded in the 

 forms of subaerial sculpture, but the youthful aspects of the scarp and 

 of the canyons traversing it do not bear out the inference. Thus the in- 

 terpretation of this coastal slope as a modified sea-cliff is in several re- 

 spects not in accord with facts. 



Considered as a fault scarp, the feature is more readily understood, 

 although' the evidence of faulting is not conclusive. Steepness is an 

 original character of a fault scarp, and may in this case be supposed to 

 have limited the effect of wave erosion and to have been favorable to 

 landslides. Thus the subordinate occurrence of marine terraces and the 

 dominant concave contour characteristic of landslip scarps are explained. 

 The canyons in which the mature ravines of the higher ranges terminate 

 seaward are cuts in a coastal margin rapidly raised above baselevel, after 

 the manner of a fault block elevated relatively to the downthrown block. 

 The uniform trend of the coast for 60 miles, coterminous with the steep 

 scarp, bears the character of a fault line. The test of this interpretation 

 of the physiographic aspects may be the determination of the fault where 

 it runs ashore. Northwestward it passes possibly east of point Sur, and 

 thence beneath the ocean. The writer did not observe the geologic rela- 

 tions near point Sur. Southeastward the trend of the supposed fault 

 strikes the shore near Piedras Blancas. The white rocks, which are de- 

 scribed by the Spanish name, are of Miocene shale, and form a small 

 area west of the Franciscan formation that extends from the coast across 

 Pine mountain. This isolated patch of Miocene, Piedras Blancas, has 

 the position of a downftulted mass. The fault, not having been traced 

 on the ground, can not, however, be said to be demonstrated. 



The weight of physiographic and geologic evidence is clearly in favor 

 of a structural origin for the bold scarp of the coast, at least from near 

 Posts to Arroyo San Carpoforo, and it is therefore considered to consti- 

 tute a third type, in the genesis of which deformation was the dominant 

 activity, while erosion and marine sculpture played subordinate roles. 



INCIDENTS IN THE SCARP-GROWTH 



The rise of this scarp from ocean level was interrupted b}' a decided 

 pause, which is marked in a group of marine terraces covering a space 



