II. geological observations 



SEA FLOOR TOPOGRAPHY OF THE BERING SEA (fig. 2) 



The Bering Sea is located in the northernmost portion of 

 the Pacific Ocean. It lies inside the Aleutian Island arc and 

 is bounded to the north by Siberia and Alaska. The narrow, 

 shallow Bering Strait connects the Bering Sea to the Chukchi 

 Sea (also known as the Chukotsk Sea), which is that portion 

 of the Arctic Ocean lying immediately north of northeastern 

 Siberia and northern Alaska. 



The continental slope traverses the Bering Sea obliquely 

 from southeast to northwest, cutting it into two approximately 

 equal areas, (1) an abyssal ocean basin and (2) an extensive 

 and shallow continental shelf. The recorded soundings on 

 existing charts show that the abyssal ocean basin has a level 

 floor at a depth of about 2100 fathoms, 100 fathoms deeper 

 than could be recorded by the NMC-1 fathometer aboard the 

 USS NEREUS. Along the track of the USS NEREUS from Adak 

 to the Pribilof Islands, the abyssal floor of the central portion 

 of the basin is everywhere deeper than 2000 fathoms and 

 probably level because even minor seamounts rising from 

 the basin to less than 2000 fathoms are absent (fig. 3A*). At 

 the periphery of the basin near the continental slope, the 

 floor rises to depths less than 2000 fathoms and has the form 

 of a smooth, gentle, concave-upward slope suggestive of a 

 depositional surface such as might have been formed by the 

 sedimentation of large quantities of sediment transported into 

 the basin from the continental shelf. In the immediate vicinity 

 of the base of the continental slope, this gently rising plain is 

 interrupted by a number of seamounts. 



Beyond these deep seamounts toward the Pribilof Islands, 

 the continental slope rises rapidly and straight. The mile-high 

 portion of the slope between 1300 and 200 fathoms has an aver- 

 age declivity of 23 degrees, making it one of the steepest known 



*The plotted geographic position of the strips in figures 3, 4, 

 6, and 7 can be determined by reference to figures 2 and 5. 



