IV-64 



streams or as seepage across the surface, coastal marshes often 

 form and circulation patterns are weak and undefined. This 

 situation may exist where local coastal drainage runs off to the 

 sea, where a drowned river valley has filled in so much that the 

 river channel is no longer defined, or where sediment deposition 

 at the mouth of a large river forms a delta (Figure IV. 1.6). 



Fjords are formed where a glacier, having gouged out a deep 

 embayment, melts as it reaches the sea and deposits the entrained 

 dirt and rock as a shallow sill across the entrance of the 

 embayment (Figure IV. 1.25). This sill isolates the lower water of 

 the fjord from the sea; the only significant water movement is 

 in the layers above the sill level. 



It is where moderately large rivers and streams meet the sea that 

 the unique estuarine circulation patterns occur most frequently. 

 Large fresh water flows in well-defined channels tend to slide 

 over the top of denser sea water without rapid mixing. Water 

 movement in such cases exhibits various degrees of stratification. 



Narrow channels and high fresh water flows result in a well-defined 

 sea water layer moving upstream along the bottom of the channel 

 and a nearly fresh layer moving toward the sea along the surface 

 (Figure IV. 1.26). 



The Mississippi and Savannah Rivers are classic examples of this 

 "salt-wedge" circulation pattern. With this type of water move- 

 ment, salt and water from the bottom layer mix constantly into 



