76 



Lithology 



elephants to the northern islands (Stock, 

 1935), and separated others so that certain 

 marine invertebrates, land animals, reptiles, 

 insects, and plants began to develop endemic 

 varieties (Grinnell, Dixon, and Linsdale, 

 1937; Cockerell, 1938, 1940; Dunkle, 1950). 

 Unless diastrophic activity greatly in- 

 creases in the future, it seems probable that 

 the future geography will be characterized 

 by a general retreat of the shoreline as one 



after another of the basins becomes filled by 

 sediment from shore. Because the volume 

 of water in the continental borderland far 

 exceeds the volume of rock above sea level 

 in the tributary drainage area, it seems evi- 

 dent that the rate of filling of the basins will 

 decrease unless large additional drainage 

 areas are captured. Thus, the rate of sea- 

 ward movement of the shoreline should also 

 decrease in the future. 



