Proceedings of the Ohio State Acadcvw of Science 231 



THE DEVELOPMENT OF SHORE LINES. 



The processes involved in the development of shore lines 

 are chemical and mechanical. The chemical factor is not of 

 great consequence, though from one point of view it demands at- 

 tention ; the mechanical processes are really the ones that need 

 consideration. Winds impel the water into waves and currents 

 producing primarily two movements, on-shore and along-shore. 

 The effectiveness of each movement is controlled directly by the 

 velocity of the wind and the nature of the coast. 



The work accomplished by these agencies is influenced in 

 the first place by the nature of the material which the waves 

 are attacking ; if the coast is rock it yields less readily than do 

 unconsolidated deposits ; in the second place, by the profile of 

 the beach and oft'-shore slope. Ultimately these agencies under 

 normal exposure to waves will bring about a fairly uniform and 

 constant profile which is a gentle long slope into deeper water. 

 The time required for a given body of water in a particular local- 

 ity to produce shore line structures, depends very largely upon 

 the original outline of the coast : if sufficiently irregular, and if 

 it yields quickly to these denuding agencies, a supply of material 

 will be at hand for constant work. 



It is in the production of this material that the chemical pro- 

 cess figures. In the presence of water, chemical disintegration 

 is facilitated. This is important even when the coast being at- 

 tacked consists of unconsolidated deposits. The basic elements 

 of glacial drift break down more readily, leaving the acidic for 

 distribution by waves. 



But the more effective work in the preparation of material 

 is accomplished locally by the waves of translation which erode 

 the shores producing bluffs, that in turn are under-cut by wave- 

 impact and the tools the water has in it. This on-shore move- 

 ment of water likewise grinds the constituents of the beach, 

 rounding and diminishing the size of all the stones. The along- 

 shore movements also do much attrition work. Furthermore, as 

 the waves of greater size break off-shore, they pick up bits of 

 rock, dashing them again to the bottom, thus continuing the work 

 of attrition begun nearer shore. 



