THE WORK OF THE OCEAN 



307 



unequally resistant material, will be made irregular by the waves. 

 A regular coast of uniform material, but unequal exposure, will be 

 made irregular by greater cutting at the points of greater exposure. 

 A coast of marked irregularity and homogeneous material will be 

 made more regular by the cutting off of the projecting points, be- 

 cause they are most exposed. With a given set of conditions, 

 waves tend to develop a certain sort of shore-line which, so far as 

 its horizontal form is concerned, is relatively stable. Such a shore- 

 line may be said to be mature 1 so far as wave-erosion is concerned. 



Fig. 253. A wave-cut terrace now well above the sea. Either the land has 

 been raised or the sea-level has sunk since the terrace was cut. Seward 

 Peninsula, Alaska. (U. S. Geol. Surv.) 



Since coastal lands are, in general, both heterogeneous and un- 

 equally exposed, a mature coast-line is somewhat irregular. 



Since the conditions of erosion along coasts are constantly, 

 even if slowly, changing, maturity is constantly being approached, 

 but rarely reached. Other forces and processes, such as those of 

 aggradation, vulcanism, and diastrophism, are in operation along 

 coasts, and their results are sometimes antagonistic to those of the 

 waves. The horizontal configuration of coasts is, therefore, the 

 result of many co-operating forces, of which waves are but one. It 

 is, nevertheless, important to note the end toward which the waves 

 are working, even though they are continually defeated in their 



1 Gulliver, Shore Line Topography; Proc. Am. Acad. Arts and Sci., Vol. 

 XXXIV, 1899, pp. 151-258. A valuable study of shore-line topography. 



