INSTABILITY OF SEA COASTS 



299 



ties of the land surface, so the waves and currents of the 

 ocean are constantly straightening out the water margins. 

 Uniformity seems to be the goal for the erosive forces. 

 But when the results of surface erosion are brought to the 

 sea by the rivers, deltas are formed which interfere with the 

 straightening of the coast. If the material brought by the 



A BEACH AT CATALINA ISLAND. 

 Notice how the water is smoothing out the irregularities of the land. 



rivers is sufficient, a delta is built out into the sea in spite 

 of the action of the waves and currents and the coast line 

 becomes increasingly irregular. Lake shores are acted 

 upon in a similar way and with similar results, only the 

 forces here are less powerful than those that act upon the 

 sea coasts. 



142. Instability of Sea Coasts. It often happens that in 

 making excavations at a considerable distance from the 



