242 



PHYSICAL GEOLOGY 



FIG. 258. Wave-cut terraces on the California coast. (U.S. Geol. Surv,) 

 How many terraces are shown ? What is their relative age ? Outline 

 the history of the coast as recorded by the terraces. What changes are now 

 in progress ? 



The height of sea cliffs depends upon the elevation above sea 

 level of the land at the coast. Their steepness varies with 

 (1) the strength and structure of the rocks, and (2) the 

 rapidity of wave cutting and of weathering upon the cliffs 

 above. Loose material usually cannot stand in steep cliffs. 

 Firm rocks may form vertical and even overhanging cliffs 



FIG. 259. Raised beaches, near Elie, Fife. (Laurie.) 



(Figs. 260 and 261). (What rock structures favor, and what 

 ones oppose, the formation of steep cliffs?) Rapid cutting by 

 the waves tends to keep the cliffs steep, while the weathering 

 of the rocks of the upper cliffs and the removal of the loosened 

 material tend to lessen their declivity. (What inference 

 may be made from the fact that even sea cliffs containing 



