Coasts 



23 



floors of the caves are as much' as 50 feet 

 below sea level, the depth being approxi- 

 mately proportional to the length of the 

 caves. A large sea cave at Marineland in 

 Palos Verdes Hills is dry and slightly above 

 sea level; it probably was abandoned by the 

 sea at the same time that a nearby low rock 

 platform emerged. Other caves have col- 

 lapsed roofs as at Point Loma or have devel- 

 oped into sea arches as at Anacapa (Fig. 

 25) and Santa Barbara Islands. 



Depositional Coasts 



In southern California depositional coasts 

 consist chiefly of sand beaches. Mud flats 



are present in estuaries and lagoons but do 

 not face the open sea and therefore are not 

 considered in this discussion as a type of de- 

 positional coast. Gravel beaches are narrow, 

 many are separated from the ocean by sand 

 beaches, and with one major exception they 

 occur at the base of sea cUfTs from which 

 they were mostly derived (Emery, 1955a). 

 Because of these facts most gravel beaches 

 in southern California are more indicative of 

 erosional coasts than depositional ones. One 

 gravel beach, however, forms a bar across 

 the half-mile width of an estuary three miles 

 north of Encinitas; thus it is part of a depo- 

 sitional coast (Fig. 157, p. 184). 



About 30 per cent of the sand beaches of 



CAVES AT SANTA 

 CRUZ ISLAND 



Figure 24. Sketch map of Painted Cave and a smaller one east of it cut through andesite and basalt near the north- 

 western end of Santa Cruz Island. The heavy straight lines mark the strike of faults along which the caves were eroded. 

 From Emery (1954a). 



