198 



DEPTHS OF THE OCEAN 



basin (see Fig. 143), more than 3000 metres deep in the central 

 portion. From this depth the floor rises gradually towards 

 the continental slope on either side. The main features of the 

 continental slope and shelf along the coast of Norway will be 

 grasped by reference to the accompanying diagram (Fig. 144). 

 The term "coast banks" is usually applied to the higher parts 

 of the submerged continental plateau or continental shelf, which 

 are frequented by fishermen ; there is often a marked "edge" 

 between the plateau and the continental slope. 



The continental shelf fringes to a greater or less extent the 

 whole of the coasts of the Norwegian Sea, and occupies alto- 

 gether about a third of its entire superficial area. This shelf 

 is covered by depths down to 200 metres with channels down 

 to 600 metres. In water shallower than 200 metres there 



are only comparatively 

 small banks, the great- 

 est being at Lofoten 

 and Romsdal and 

 round the Faroes and 

 Iceland. Deeper than 

 600 metres the con- 

 tinental slope is steep ; 

 the bathymetrical 

 curves for 600 and 

 1000 metres lie every- 

 where in close prox- 

 imity to one another, and the area of the sea-bottom between 

 them is no more than 5.4 per cent of the whole extent of the 

 Norwegian Sea. 



G. 144.— Diagrammatic Section off the Norwegian 



Coast. 

 Continental slope ; b, continental edge ; c, continental shelf 

 or plateau ; d, coast bank ; e, fjord ; f, coast. 



Deposits of 

 the North 

 Atlantic. 



The distribution of the deposit-types over the floor of the 

 North Atlantic is shown on Map IV., an examination of which 

 bears out the statement that the terrigenous deposits are 

 relatively more important in the North Atlantic than in the other 

 oceans, in correlation with the relatively large area covered by 

 shallow water. Thus of the total area of 23 million square miles, 

 one-half, about ii|- million square miles (or 49 per cent), is 

 covered by terrigenous deposits. This area is to a very large 

 extent occupied by Blue mud, no attempt having been made to 

 indicate on the map the small areas occupied by Green mud off 

 the coast of the United States, off the Spanish and Portuguese 

 coasts, and in the vicinity of the Wyville Thomson Ridge, nor 

 the small areas occupied by Volcanic mud in the neighbourhood 



