INTERPRETATION OF COASTAL PHYSIOGRAPHY 427 



some late Miocene or early Pliocene episode there developed an eleva- 

 tion such that the higher hills stood between several hundred and 2,000 

 feet above the then sealevel. They are now represented by the peaks 

 4,000 to 5,000 feet above sea, which have been described as monadnocks. 

 During a long episode of constant sealevel, erosion produced a broad low- 

 land that still may be recognized in the general approximation of sum- 

 mits and spurs to a uniform height of perhaps 3,200 feet. Renewed, 

 uplift, amounting to 1,200 feet or more, led to partial dissection of the 

 lowland plain and established the upper courses of the present ravines 

 on the western slope. The streams discharging at a level which is now 

 2,000 feet above sea may have entered the ocean not far beyond, or at 

 some distance west of the present coast. The features of the upper por- 

 tion of the Santa Lucia range above 2,000 feet are apparently character- 

 istic of subaerial development only. Benches of marine'origin have not 

 been detected, and the range may not have been a coast range during 

 its earlier history. 



Farther elevation of the range to its present altitude involved an uplift 

 of 2,000 feet more. In referring to this movement as a later stage of 

 development in comparison with the earlier evolution, there is no inten- 

 tion of describing it as a simple episode, but as the topographic features 

 belonging to it are distinctly youthful, whereas those of the higher part 

 of the range are mature, there are two distinguishable movements. 



Among the features of the later stage, attention is especially drawn to 

 the great scarp which rises from the ocean. Not everywhere equally bold, 

 this scarp is most conspicuous south of the Devils canyon at Gamboa 

 point, but in many remnants, which are only a little less modified than 

 the gentler slopes, it still retains steeps of 30 to 35 degrees, and even of 

 40 degrees. On these the development of gullies and landslides gives 

 abundant evidence of the process of recession which is reducing the slope. 

 At the base sea cliffs here and there mark the opposite effect of the attack 

 of the waves. 



Among the various possible types of scarps there are but two whose 

 genetic conditions are consistent with the environment of this one. They 

 are the sea cliff and the fault scarp.* To distinguish them on this coast 

 it is desirable to describe certain types of coastal slope which appear to 

 differ in conditions of development. 



THREE TYPES OF COASTAL SLOPES 



Three types of coastal slopes may be distinguished between Santa 

 Barbara and San Francisco, according to the dominant condition of 

 modeling which determined the present aspect of the surface above the 



* Gilbert : Monograph I, U. S. Geological Survey. 



