SECT. 2] 



THK Min -OCEANIC RIDGE 



401 



Fig. 11. KartlKniako epicenters in the Norwegian Sea, 1905-56. Plotted f"rf)ni compilation 

 of (iiitenberg and Richter (1954) and the epicenter cards of the United States Coast 

 and Geodetic Survey. (After Heezen and Ewing, 1961.) 



7. Arctic Basin 



Between Spitsbergen and Greenland, the Norwegian Sea basin narrows to 

 less than 200 miles from shelf break to shelf break. This area has been referred to 

 as the Nansen's Sill as it marks the sill or threshold for water-masses flowing 

 between the Norwegian Sea and the Arctic Basin (Fig. 11; and Heezen and 

 Ewing, 1961). That the depths across Nansen's Straits are less than those both 

 to the north and to the south is apparent from existing soundings. However, 

 the existence of an east-west ridge at Nansen's Sill is pure supposition. In 

 considering the course of the mid-oceanic ridge through the length of the Gulf 

 of Aden we saw that, as the Gulf narrowed, the depth of the basins flanking the 

 median ridge shallowed accordingly. Nansen's Sill lies at the narrowest part of 

 the ocean and hence, by analogy with the Gulf of Aden, the depth here should 

 be the shallowest. Hope (1959), however, states that "recent Soviet exploration 

 has in fact revealed a deep-water trough completely piercing Nansen's Sill". 

 He also quotes Frolov and Pasecki (1958) as reporting that "on the 80th 

 parallel the trough is 3000 m deep and 50 km wide between 1000 m isobaths. 

 Its orientation is roughly northward". Hope points out that "this trough then 



