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SUMMARY 



The Geologic and Geographic Setting of 

 Santa Monica Bay 



Santa Monica Bay is bordered on the north by a mountain 

 range that has been uplifted along east-west trending faults. 

 On the southwest, the Palos Verdes Hills have been elevated 

 during relatively recent time. The north side of the hills 

 is separated from the Los Angeles Basin by a fault trending 

 in a northwest direction. This fault probably extends into 

 Santa Monica Bay and has played an important role in its 

 structural history. The relief in the Los Angeles Basin was 

 formed largely in Late Pleistocene and early Recent geologic 

 time and the tectonic forces responsible for deformation 

 probably have also affected the submarine geology of the bay. 

 Thus, the structure of Santa Monica Bay is more related to 

 forces active in the Los Angeles Basin and Palos Verdes Hills 

 than to tectonic activity in the Santa Monica Mountains, Earth- 

 quakes on Ismd and in the bay, and other lines of evidence indi- 

 cate that deformation is still taking place. 



The major drainage into the bay is from the southern 

 slopes of the Santa Monica Mountains, while there is little or 

 no drainage from the area south of the city of Santa Monica, 

 Prior to 1825 Ballona Creek drained a large inland area, but 

 since that date only a minor amount of material has entered 

 the bay through the Ballona Creek outlet. A variable amount 

 of sand comes into the bay around Point Dume, but probably no 

 material finer than beach sand comes from this source. 



