1921. No. II. THE STR.AXDFLAT AXD ISOSTASY. 227 



XV. THE CONTINENTAL SHELF AND ITS 

 FORMATION. 



In a previous treatise on the bathymetrical features of the northern 

 seas [1904J I have described the continental shelf of Norway and of other 

 northern regions and discussed its formation. There is this resemblance 

 between the continental shelf and the strandfiat, that both of them form 

 fairly horizontal planes, in front of the coast which in Norway and several 

 other countries is steep and ascends abruptly from the inner margin of 

 the planes. Both formations as far as they are cut in solid rock, may 

 most naturally be assumed to have been planed largely by marine de- 

 nudation of some kind. There is, however, this striking difference be- 

 tween them, that the typical strandfiat is largely confined to cold regions, 

 where there has been severe climates favouring shore erosion by frost, 

 and it is only exceptional that strandfiats occur outside such regions, in 

 places where there have been special climatic conditions, as for instance 

 along the south-east coast of India — while the continental shelf has a 

 universal distribution along most old coasts in all latitudes. 



The continental shelf is obviously to a large extent built up of waste 

 from the land carried into the sea during long geological periods and 

 deposited outside the coasts. Rut as I previously pointed out [1904] 

 it is also to some extent cut in solid rock. It would, for instance, be 

 extremely difficult to explain in any other way the striking fact that 

 outside the Norwegian coast its shape and the height of its level is ob- 

 viously to some extent dependent on the nature of the rocks of the coast. 

 It is especially narrow and high where the rocks possess a comparatively 

 great power of resistance to erosion, as along the Romsdal, Sondmor coast 

 and the coast of Lofoten, A'esterålen and Senjen, while it is very broad 

 and lies comparatively deep below sea-level outside Helgeland where the 

 rocks on the whole possess much less power of resistance to erosion. 



The submerged fjords on the continental shelf, c. g. outside Søndmør, 

 and outside Helgeland, and the coast north of Trondhjem, also indicate 

 the rocky nature of the shelf. These fjords, which to a large extent follow 

 the same direction as the valleys of the great Caledonian mountain folding 

 on land, are obviously sculptured in stjlid rock [cf. Nansen, 1904, p. 151]. 



