34 



Physiography 



Figure 34. Profiles of sea floor 

 near Santa Barbara showing 

 masking of submerged wave- 

 cut terrace by sedimentary fill. 

 Adapted from W. C. Thomp- 

 son (in Dietz and Menard, 

 1951. Fig. lOD). 



be seen; however, correlation of terraces 

 from one profile to another is difficult by 

 mere visual inspection. A more satisfactory 

 method is one in which the depth span of 

 each terrace on each profile is shown by a 

 wide vertical line (Fig. 36). Correspondence 

 of terrace depths on adjacent profiles per- 

 mits short-distance correlation with a fair 

 degree of certainty. Correlation of most of 

 these terraces from mainland to island or 

 island to island, however, is less certain. 



The abundant outcrops of sedimentary, 

 metamorphic, and igneous rocks on the 

 mainland and island shelves show that the 

 terraces are erosional rather than deposi- 

 tional in origin, at least for the most part. At 

 the outer edges of both submerged and 

 emerged terraces, where sediment cover is 

 thin, bedrock forms linear outcrops which 

 are much steeper than the terraces that bor- 

 der both sides. Erosion is also indicated by 

 the presence of rounded gravels derived from 



Figure 35. Profiles of the sea floor bordering the Palos Verdes Hills from shore to depths of several hundred feet. These 

 were made from spot echo soundings taken about 60 feet apart, supported in part by recorded fathograms. Extension 

 of profiles on land is based on published contour maps. The vertical scale is eight times the horizontal one. From 

 Emery (1958a, Fig. 4). 



