WAVES AS DESTROYERS AND BUILDERS 161 



is an example of what has occurred in many seacoast 

 regions. 



Unless the material pillaged from the land by the waves 

 falls into too deep water, it is buffeted about by them and 

 broken and worn into small pieces. These are then borne 

 along by the shore currents until they find lodgment in 

 some protected place where they can accumulate. When 

 sufficient material has been accumulated, the storm waves 



A SAND SPIT, FORMED BY WAVES AND CURRENTS 



and the wind sweep some of it above sea level and fringe 

 the water's edge with a border of water- worn sand and 

 pebbles. These accumulations of shore drift are called 

 beaches. 



Currents moving loose material with them sometimes 

 form it injto bars which tie islands to the mainland or extend 

 into the sea free ends, forming what are called spits. A 

 famous example of a land-tied island is that of the great Eng- 

 lish fortress at Gibraltar. Although now a promontory, it 



