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deltas of the world and 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 horder to Cape 

 Mendocino 

 Because of the narrow Continental Shelf, periodic 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 embayments and the unique earthquake-born valley of 

 San Francisco Bay, which, in the delta formed by the confluence of 

 the San Joaquin and Sacramento Rivers, shows what erosion and 

 sedimentation might have done along the southwest coast if rainfall 

 were greater in that area of easily erodable mountains. 



Pacific Northwest estuarine region: Cape Mendocino to the 

 Canadian horder 



The Continental Shelf and coastal configurations are similar to 

 those of the Pacific Southwest, but ocean water temperatures are 

 lower here; the movement of the California current away from the 

 coast is not as pronounced, and heavier rainfall has resulted in some 

 major rivers cutting through the coastal mountains to form deeply 

 embayed estuarine systems. Extensive erosion and sedimentation have 

 caused wide tidal flats, bars, and shoals to be typical of these systems. 



The Straits of Juan de Fuca and Puget Sound,which were glacier 

 formed, do not have as severe sedimentation as exists along the ocean 

 coast, and have retained much of their original configuration. 



Alaska estuarine region: All of Alaska including the Aleutian 

 and Bering Sea Islands 

 The dominant factors in this region are temperature and precipita- 

 tion. Water temperatures are near freezing, and much of the precipita- 

 tion falls as snow. The Continental Shelf is wide all through the re- 

 gion, and tide ranges are very large. The southeast and south coasts 

 have active glaciation and consist primarily of glacier-cut embayments 

 and fjords; the west and north coasts are much flatter and have been 

 modified to some extent by sediments eroded from the interior, includ- 

 ing glacial silt, and by the grinding action of pack ice during winter. 



Pacific Islands estuarine region : The Hawaiian Islands^ Ameri- 

 can Samoa, and Guam, 

 This region consists of tropical ocean islands of volcanic origin. 

 Dominating factors are lack of a continental shelf, full exposure to 

 oceanic conditions, and pleasantly warm temperatures. Coral reefs and 

 beach and bluff configurations are typical. 



THE LAND AND THE WATER 



Within the general domination of broad-scale environmental factors 

 are smaller scale governing conditions that, through their effects on 

 water movement and circulation, determine what kind of local en- 

 vironment can exist in a particular estuarine system. 



