THE FORMS CARVED AND MOLDED BY WAVES 233 



by constantly increasing friction, a strong turning motion or 

 couple is started about a horizontal axis, the immediate effect 

 of which is to steepen the forward slope of the wave, and this con- 

 tinues until it overhangs, 

 and, falling, " breaks " into 

 surf. Such a breaking 

 wave is called a " comber " 

 or "breaker" (plate 11 B). 

 Effect of the breaking 

 wave upon a steep rocky 

 shore the notched cliff. 

 If the shore rises abruptly 

 from deeper water, the top 



of the breaking wave is FIG. 249. Notched rock cliff cut by waves and 

 hurled against the cliff with the fallen blocks derived from the cliff through 

 the force Of a battering ram. undermining Profile Rock at Farwell's 



Point near Madison, Wisconsin. 



During storms the water of 



shore waves is charged with sand, and each sand particle is driven 

 like a stone cutter's tool under the stroke of his hammer. The effect 

 is thus both to chip and to batter away the rock of the shore to 

 the height reached by the wave, undermining it and notching 

 the rock at its base (Fig. 249). When the notch has been cut 

 in this manner to a sufficient depth, the overhanging rock falls 



by its own weight in blocks which 

 are bounded by the ever present 

 joints, leaving the upper cliff face 

 essentially vertical. 



Coves, sea arches, and stacks. 

 It is the headland which is 

 most exposed to the work of the 

 waves, since with change of wind 

 direction it is exposed upon more 

 than a single face. The study of 

 headlands which have been cut 

 by waves shows that the joints 

 within the rock play a large role 

 in the shaping of shore features. 



FIG. 250. A wave-cut chasm under 

 control by joints, coast of Maine (after 



Tarr). 



. n ,. , , , 



The attack of the waves under 



the direction of these planes of 



