244 



PHYSICAL GEOLOGY 



island in front of the retreating shore. From their form, such 

 islands are frequently called stacks or chimney islands (Fig. 

 263). 



Waves may cut through a rocky headland in such manner 

 as to form a natural bridge (Fig. 264). If the roof covering a 



FIG. 261. Sea cliffs in northwestern France. 



sea cave near its mouth remains after the roof above the inner 

 end of the cave has collapsed, a natural bridge also results. 



While interesting because of their picturesqueness, these 

 special features of cliff shores have little geological importance. 



The goal of sea erosion. Just as rivers seek to wear the 

 land to sea level, so the waves of the sea, acting as a horizontal 

 saw, seek to cut the land to a level slightly below the surface 



