220 



University of California. 



[Vol. 2. 



not in general yield abundant drift. Extensive incoherent deposits 

 along the main coast are not common, and there are very few 

 streams bringing to the ocean any considerable supply of detritus. 

 The material brought within reach of wave action is in general 

 readily disposed of, so that active cliff cutting is now taking place 

 at nearly all points of the California coast. The same has been 

 true, apparently, during all the time that the terraces were forming. 

 For, along the coast, in general, where the slopes are gentle, active 

 cutting and not deposition is shown by the wave-cut terraces. 

 Where the slopes are steeper and the coast more rugged, though 

 no terracing or only imperfect terracing is found, the conditions 

 must have been still more unfavorable to the formation of wave- 

 built barriers, on account of the steeper on- and off-shore slopes, 

 and the more resistant rocks, supplying a very limited amount of 

 drift. 



Where barriers have been well developed, and are associated 

 with low landward slopes (as would normally be the case), these 

 features, on elevation, may preserve their chief characteristics for a 

 long time. When built of loose, incoherent material, the forms 

 may be greatly altered by winds, unless soon covered with a 

 protecting mat of vegetation. However, where barriers are not 

 now being developed to any considerable extent, as along the 

 California coast, and where the conditions have been extremely 

 unfavorable to their extensive formation in the past, such fossil 

 features can not be expected on elevated parts of the coast, espe- 

 cially where the topography is rugged, and the slopes nowhere 

 approach the low angle necessary for their development. 



In the formation of bars as distinguished from barriers, the first 

 essential is an irregular shore line, for in order to have a bar there 

 must first be an interval to be spanned. In order that a bar may 

 form across any opening or embayment of the coast, the entrance 

 must have a certain width proportioned to the size of the opening 

 itself. If the entrance is narrow and the embayment large, the 

 entrance will not be barred, on a seacoast, on account of the tidal 

 scour. If the embayment is very broad and open, and the water 

 sufficiently deep, the shore drift will follow the coast line, instead 

 of crossing from point to point. 



