22 



The Ocean 



Fig. 13. Submarine valley off the mouth of the Hudson (according to Smith). 



expected to remain at such steep angles for any length of time without collapsing. 

 Nor can it be supposed that they have been washed out of thick soft bottom sediments 

 since they would then hardly be permanent. On the other hand, they appear definitely 

 to be quite young formations that have been formed only in recent times; they appear, 

 at least in part, to be connected with earthquakes, tectonic breaks and fissures. For a 

 description of the morphology of these canyons see especially the work of Shepard 

 and his collaborators (1933, 1938); concerning their probable origin see particularly 

 Daly (1936) and Kuenen (1938); reference might also be made to the interesting 

 work of Cooper and Vaux (1949), of Kullenberg (1954), Hecson, Ericson and Ewin 

 (1954). They have been discussed from the purely geological standpoint by Jessen 

 (1943), and a survey has been given by Kaehne (1941). 



Turning to the general form of the deep sea bottom it is immediately obvious that the 

 rises and ridges that divide the ocean are features of such enormous size that they 

 could scarcely occur on the land. The most prominent of these features is the Atlantic 

 Ridge that extends from Iceland through the Azores, Ascension and Tristan da 

 Cunha to Bouvet Island and resembles an enormous mountain range 20,000 km 



