THE WORK OF THE OCEAN 303 



The general result of wave-erosion is the advance of the sea on 

 the land, the rate of advance being determined chiefly by the nature 

 of the material attacked and the strength of the waves. Though 

 examples of the retreat of coast-lines before the advance of the 

 sea are numerous, it is not to be understood that the advance of 

 the sea on the land is universal or uninterrupted. On the contrary, 

 the land often encroaches on the sea, and the two things sometimes 

 go on side by side. At Long Branch, N. J., the advance of the sea 

 has been so rapid in recent years as to menace important buildings, 

 while a few miles to the north and south, the land is advancing into 

 the sea by the deposition of shore drift. The low coast of the 



Fig. 247. Fig. -248. 



Fig. 247. Diagram illustrating high sea cliffs. It shows also a submerged 



terrace, due partly to wave-cutting and partly to building. 

 Fig. 248. Diagram snowing a low sea cliff. 



Middle Netherlands has retreated two miles or more in historic 

 times, but the opposite tendency is shown at other points in the 

 same region. On the coast of England the sites of villages have 

 disappeared by the advance of the sea within historic times 1 , but 

 the coast of the same island affords illustrations of land advance. 

 On the south side of Nantucket Island, the sea-cliff has been known 

 to retreat before the waves as much as six feet in a single year. 2 

 Almost every considerable stretch of coast affords illustrations both 

 of the advance of the sea on the land and of land on the sea; but 

 in the long run, the former exceeds the latter. 



Topographic features developed by wave-erosion. As the 

 waves cut into the shore at and near the water-level, they develop 

 a steep slope above the line of cutting. This steep slope is the sea- 

 cliff (Figs. 247 to 250). The term lake cliff is applied to the cor- 

 responding cliffs of lakes. 



1 Dana, Manual of Geology, 4th. ed., p. 219. 



2 Shaler, Sea and Land, p. 29. 



