GENERALIZATION 2l3 



The land is assumed to have considerable relief, and the submergence 

 is assumed to be complete. Taking the process as a whole, the migra- 

 tion of the shoreline is equal to what it would be by shifting alone; 

 but at different stages the actual migration and the hypothetical shifting 

 have varying ratios. 



If we assume the process to begin with relatively low initial cliffs 

 (a common case), migration at first exceeds mere shifting by reason of 

 excessive cliff recession (case I) ; the two curves representing the land 

 surface and that of marine erosion separate; the latter is concave up- 

 ward. With the decreasing rate of cliff-cutting there comes a stage 

 where it merely equals the rate at which shifting alone would carry the 

 shore landward (case II) ; the curves are about parallel and have their 



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Figure 4. — Generalized Diagram of Shore Erosion. 



The upper curve represents the original land surface. The lower represents the surface of 



marine denudation. 



maximum separation. Then migration becomes less than the theoretical 

 shifting by reason of the small seaward slope of the remaining land 

 (case III) ; the lower curve becomes convex upward and approaches 

 the upper. 



Interpreted in terms of shoreline topography, the erosive work of the 

 sea at first advances the shoreline in its cycle, smoothing its contour, 

 pushing back its cliffs rapidly, and increasing them in height and length. 

 As this process grows slower by its own development, the effects of sink- 

 ing begin to keep pace with those of erosion. The shore forms remain 

 stationary in their cycle while the shoreline recedes landward. The 

 cliffs have at this time their maximum height. With the diminution of 

 slope of the land surface, the surface of marine denudation approaches 

 it, the cliffs become lower, the rate of their recession is augmented, and 

 the features of youth return. Continued sinking will at length cause the 

 surface of the cut terrace to intersect that of the land, and submergence 

 will be complete. 



