A second escarpment of considerable magnitude was 

 located during two crossings of a submarine "spur" extending 

 out 300 miles from the Antarctic Continent adjacent to Prin- 

 cess Ragnhild Coast. A profile of this escarpment, obtained 

 during the west-to-east crossing, shows the probable faulted 

 nature of the eastward side of the "spur" (see fig. 31B). The 

 escarpment, with a 44- degree declivity, drops from 1100 fath- 

 oms to at least 2700 fathoms; and aural soundings suggest the 

 presence of a foredeep. This escarpment is almost certainly 

 the result either of faulting or of a sharp flexure in the earth's 

 crust. It may have been produced by uplift of the elevated 

 side, or by foundering of the deep portion or, most likely, by 

 a horizontal movement along a fault which displaced a portion 

 of the Antarctic Continent and formed the submarine "spur." 

 This feature reminds one of the Gordo Escarpment off northern 

 California which, according to Shepard, may have been 

 formed by horizontal displacement of the continental shelf 

 along an extension of the San Andreas fault. 



Continental Slopes and Submarine Canyons. During her 

 passage around the Indian Ocean sector of the Antarctic 

 Continent, the HENDERSON remained for the most part in 

 the deep water (greater than 2000 fathoms) of the basins 

 surrounding the continent. These basins are extremely level 

 and no seamounts were found in them. At times the vessel 

 ran along the continental slope where depths were less than 

 2000 fathoms so that the bottom was recorded on the echo- 

 sounder tape. Irregular fathograms were obtained, but the 

 presence of submarine canyons or of other indentations in 

 the continental slope could not be definitely determined be- 

 cause of the constant maneuvering around the ice. There 

 is no detailed record of the changes in the course during 

 this maneuvering, thus many traces which appear to show 

 indentation in the slope may have been produced by the changes 

 in course along a smooth slope. The only conclusion that can 

 be drawn is that no unquestionable examples of submarine 

 canyons were found. 



The HENDERSON reached the continental shelf of Ant- 

 arctica only once. On this occasion, an excellent profile was 

 recorded almost directly up the continental slope from the 

 Indian Ocean to the Mackenzie Sea (fig. 32). In comparison 

 with the slopes around other continents of the world, this one 

 displays a profile that is remarkably long, smooth, and gentle. 

 The slope has a long, sweeping, and concave form and in 

 declivity it varies from two degrees near the top to about 



60 



