Sand Beaches 



197 



Figure 1 72. Erosional ripple marks produced by steep truncation of dark laminae and gentle truncation of thick, 

 coarse, light-colored laminate. Note the rhomboid ripple marks with their usual diamond pattern. Scripps Beach 

 with ocean side at top. 



be self-perpetuating through the building of 

 washover fans (Price, 1947), a delta-like 

 blanket of sand left when waves cross the 

 crest of the berm and the water soaks into 

 the sand. Repeated accumulation of wash- 

 over fans must add to the height of the 

 berms's edge, thereby accentuating the 



usual landward sloping surface of the berm 

 (Fig. 174). Sand beaches of southern Cali- 

 fornia also commonly contain sand cusps 

 that have shapes similar to those of gravel 

 cusps. Distances from point to point of ad- 

 jacent cusps commonly range between 3 

 and 30 meters. Preliminary studies show 



i-Sj 



Figure 173. Current ripples at former mouth of Mission Bay, San Diego. Note destruction of ripples by erosion and 

 redeposition of sand at low tide through action of escaping interstitial water. 



