252 



PHYSICAL GEOLOGY 



FIG. 271. Diagram of a coast that has been 

 submerged recently. 



tending to produce an even, regular coast, submergence an 

 irregular one (p. 238). In either case, waves and currents 



tend first to in- 

 crease the irregular- 

 ity of the shore line, 

 and finally to make 

 it smooth. Unequal 

 wave erosion and 

 the building of spits, 

 hooks, barriers, etc., 

 increase the length 

 of a shore line. 

 Later, the wearing 

 back of the head- 

 lands and the filling 

 up of the indenta- 

 tions, the complet- 

 ing of bars and the 



FIG. 272. - Diagram showing the coast repre- fillin g in f the ba / s 



sented by Figure 271 after it has been modified and lagoons they in- 

 by streams and shore agents. Marshy bay-head , straighten and 



Hfiltaa hnvp hppn formpd bv thp larirpr rivprs. ' S6 > kiraigni 



simplify the coast. 

 Figures 271, 272, 

 and 273 show suc- 

 cessive stages in the 

 development of an 

 embayed (drowned) 

 coast. Figure 274 

 shows shore deposits 

 shutting in bays, 

 and tending to sim- 

 plify the coast line ; 

 thus far, however, 



FIG. 273. A still later stage in the development they have increased 



of the coast shown in the two preceding Figures. ^ ne shore-line mile- 

 Bay filling and cliff recession have produced a 



nearly straight shore line. &gG. 



deltas have been formed by the larger rivers. 

 Waves have cut back the headlands in cliffs. 

 Shore currents and waves have built hooks and 

 bars. The islands are partly consumed. Sub- 

 marine terraces front the cliffs. The material 

 worn from the land is spread over the ocean- 

 bottom as sheets of sand and mud. 



