IV-47 



Caul f Estuarine Region : Cape Romano to the Mexican border. 



A wide continental shelf extends all the way around this large 

 embayment, in which warm tropical waters are moved gently by 

 weak currents and small tidal ranges. Heavy rainfall over most 

 of tne area brings sediments from the broad coastal plain 

 to be deposited in the estuarine zone. Host of tne drowned 

 river valleys nave evolved to a point intermediate between 

 those of the Middle and South Atlantic Regions -- barrier islands 

 are extensive and have large shallow bays behind them. 



The Missippi forms one of tne major deltas of the world. This 

 delta is unique among the estuarine systems of the United States, 

 both in its size and in the extent to which it has built out 

 over the continental shelf. 



Pacific Southwest Estuarine Region : Mexican border to Cape 

 Mendocino. 



Because of the narrow continental shelf, perodic upwelling of 

 deep water close inshore as winds force the California current 

 offshore brings cool, fertile water near the coast for several 

 months of the year. The coastline has a typical beach and bluff 

 configuration with only a few shallow embayinents and the unique 

 earthquake-born valley of San Francisco Bay which, in tne cielta 

 formed by tne confluence of the San Joaquin and Sacramento 

 Rivers, show what erosion and sedimentation might 



