i8a 



WORK OF THE OCEAN 



Every division plane, whether due to bedding, to jointing, or to 

 irregular fracture, is a source of weakness, and rock of great hard- 

 ness may be so broken as to offer little resistance. A coast which is 



regular and of equal 

 exposure, but of 

 unequally resistant 

 material, will be 

 made irregular by 

 wave-erosion. A 

 regular coast of uni- 

 form material, but 

 unequal exposure, 

 will be made irregu- 

 lar by greater cut- 

 ting at points of 

 greater exposure. A 

 coast of marked ir- 

 regularity and ho- 

 mogeneous material 

 will be made more 

 regular by the cut- 

 ting off of the pro- 

 jecting points, be- 

 cause they are most 

 exposed. With a 

 given set of condi- 

 tions, waves tend 

 to develop a certain 

 sort of shore-line 

 which, so far as its 

 horizontal form is 

 concerned, is rela- 



Fig. 187. Portion of the Texas coast, showing 

 tendency of shore-deposition to simplify the coast line. 

 The deposits (narrow necks of land parallel to the 

 coast) shut in bays. (From chart of C. and G. Surv.) 



tively stable. Such 

 a shore-line may be 

 said to be mature 1 

 so far as wave-erosion is concerned. Since coastal lands are, in 

 general, both heterogeneous and unequally exposed, a mature coast- 

 line is somewhat irregular. 



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

 XXXIV, 1899, PP- I S I - 2 5?- A valuable study of shore-line topography. 



