Physiography 



Figure 2. Raised terraces of Palos Verdes Hills facing southeastward toward Palos Verdes Point, 

 profiles of terraces in Fig. 8. Photograph by J. S. Shelton and R. C. Frampton. 



Compare with 



drawal of sea water to form glacial ice; 

 hence, at least the higher terraces must have 

 been elevated by diastrophic movements. 

 Lawson noted that many terraces are under- 

 lain by rocks of Miocene age and some of 

 Pliocene age; thus, the uplift must have oc- 

 curred in post-Pliocene time. Since the 

 reconnaissance work of Lawson and Smith, 

 no other writers have attempted a general 

 analysis of the terraces; instead, they have 

 confined their efforts to a detailed study of 

 terraces in small areas or to brief description 

 of terraces as incidental to quadrangle map- 

 ping of geology. Among the most thorough 

 local studies were those of Davis (1933) at 

 Point Dume, Putnam (1942) at Ventura, 

 Woodring, Bramlette, and Kew (1946) at 

 Palos Verdes Hills, and Upson (1951<3) at 

 Gaviota. Briefer reports of local terrace 

 elevations have been given by Ellis and Lee 

 (1919), Hoots (1931), Bremner (1932, 1933), 

 Norris (1951), and others. Terraces farther 

 south, in Baja California, have been briefly 

 described by Beal (1948) and those farther 

 north by other authors. 



Each terrace is a feature of composite 

 origin. The cut surface where visible is not 

 horizontal but instead has a slope that indi- 

 cates a period of slower-than-average rise of 

 the land from the sea. Atop the eroded sur- 

 face there is sometimes present a veneer a 

 few feet thick of rounded pebbles and cobbles 

 and of shells typical of shallow water. Many 

 of the cobbles and some of the bedrock con- 

 tain borings made by worms and various 



mollusks before the terrace was raised. Cov- 

 ering these marine deposits are alluvial fans 

 and other stream deposits that have filled in 

 the angle between the wave-cut terrace and 

 the ancient sea cliff' at its back. This mate- 

 rial reaches thicknesses of scores of feet, 

 completely burying small terraces and soft- 

 ening the profiles of larger ones. The cover 

 on the broad Linda Vista Terrace near San 

 Diego is partly in the form of six subparallel 

 beach ridges which rise as much as 100 feet 

 above the general level of the terrace (Emery, 

 1950Z7). 



Elevations of the erosional surfaces would 

 be best for making possible correlations but 

 exposures of it are rare. Published elevation 

 measurements of the depositional surfaces 

 are nearly worthless for comparing separate 

 areas because most writers have reported 

 only single elevations for the terraces, either 

 that at the front or that at the back. These 

 two elevations may diff'er by more than 100 

 feet. Both are higher than the original cut 

 surface, the one at the back because of de- 

 position of alluvial material, and the one at 

 the front because of removal of the original 

 seaward edge by both marine and nonma- 

 rine erosion. In order to secure comparable 

 elevation data for many parts of the coast, 

 the writer decided to ignore all past meas- 

 urements and to begin anew, measuring with 

 a sensitive altimeter the profiles of terrace 

 series. These data are still too incomplete to 

 provide a general picture, so instead eleva- 

 tions of terraces or of the alluvial cover atop 



