BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 21, pp. 599-624, PLS. 41-42 NOVEMBER 24, 1910 



BEACH CUSPS^ 



BY DOUGLAS WILSON JOHNSON 



[Presented hefore the Society December' 29, 1909) 



CONTENTS 



Page 



Introduction 599 



Literature 600 



Characteristics of beach cusps 604 



Contributing observers 604 



Form 605 



Material 606 



Size 607 



Spacing 607 



Relation of cusps to other beach forms. 612 



Relation of beach cusps to other factors of shore activity 613 



Artificial beach cusps 615 



Theories of origin 615 



Shaler's theory 615 



Cornish's theory 616 



Jefferson's theory 616 



Branner's theory 617 



Wilson's theory 618 



Additional theories 619 



References 623 



"Selecting any pebbly beach where the stones are prevailingly of small enough size to 

 be readily tossed about by the waves, the observer will note that at almost all times, 

 but especially after a heavy storm, the slope from the high-water mark downward is 

 scalloped In a curious manner. From the level beyond the waves, ridges tapering out- 

 wardly extend down the incline, it may be, for a distance of ten to fifteen feet or more, 

 and a height of from a few inches to two or three feet. Between these ridges, which 

 taper toward their lower and outer parts, there are small, wedge-shaped embayments, 

 which at the outer edge of the ridges may be from two or three feet to fifteen or twenty 

 feet wide, tapering thence, like the section of a rather pointed cone which is obtuse at 

 the apex, to the edge of high water. These scallops may, under favorable conditions, be 

 traced in orderly and uniform succession along miles of shore." — N. S. Shaler, 1895. 



Introduction 



The purpose of this paper is to review such previous accounts of beach 

 cusps as deal with the origin of these forms; to describe in some detail 



Manuscript received by the Secretary of the Society April 8, 1910. 



(599) 



