PACIFIC SUBMARINE PROVINCES 



521 



Fig. 32.6. Postulated faults of 

 end of Aleutian Ridge and 

 trench. Reproduced from Gates 

 and Gibson, 1956. 



j western part of the Aleutian Ridge is an arched and faulted asymmetrical 

 j wedge bounded by a northward-dipping normal fault on the north and by a 

 I northward-dipping zone of reverse faults on the south. Formation of this 

 1 1 wedge probably began with major uplift and faulting of the western Aleutian 

 .area during the middle Tertiary, and the many earthquakes and active 

 (volcanoes in the Aleutian arc today indicate that deformation is still continuing 



; (Gate and Gibson, 1956). 



J 



The structure of the ridge as Gates and Gibson speculate is shown in 

 iFig. 32.7. 



BERING SEA FLOOR 



The Bering Sea is a closed triangular-shaped basin bounded by two 

 Continents and the arc of the Aleutians. About half the area is continental 



shelf, and half lies at depths of 1600 to 2240 fathoms. The greater depths 

 are in the southwestern portion. The maximum depth recorded, 2240 

 fathoms, lies 45 miles northeast of Attu Island, and is approximately 2 

 miles above the floor of the trench on the south side of the Aleutian 

 Islands. See Figs. 32.1 and 39.10. 



The deep division of the Bering Sea is marked by a submarine range 

 that takes off northward from the Aleutian arc and veers westward. It is 

 300 nautical miles in length, 60 miles in width, and rises in one place 

 12,156 feet above the bottom. It is known as the Bowers Bank Range and 

 supports Semisopochnoi Island and the Petrel Bank, as well as Bowers 

 Bank. 



The Pribilof Islands emerge from the shelf of the Bering Sea. which 



