242 FRIDTJOF NANSFN. M.-N. Kl. 



As tlic sIkji'c erosion I)v frost will larj^a-ly increase the- rate of the 

 marine abrasion, the continental shelf may be expecterl to be very broad 

 HI the cold rcf^ions of the j,'lobe, where the climate may have favoured 

 this erosion also durin/^-- preg'laci.'d periods, dlie fact is that the continental 

 slielf is exceptionally well developed in the Arctic rejj^ions, and esijccially 

 outside the coasts rouml the Nortl: I'olar Sea. 



It nuL^ht be objectefl that by tlie j^^reat auKnuit of waste carried from 

 the land on to the surface of tlie continental shelf formed in this manner, 

 its level would be built up towards sea-level faster than the general sea- 

 level could be raised I)y the deposition of sediment on the floor of the 

 Ocean. Owing to the considerable movements of the water, however, 

 especially those caused l)y tidal-currents and wind-currents over the con- 

 tinental shelf, as a rule comparatively little sediment can be deposited on 

 its level parts or higher parts. The sediment is therefore chiefly deposited 

 in the hollows and depressions or is gradually moved beyond the shelf, 

 and is deposited on the continental slope outside. 



Hence tliere will not as a rule be much deposition of sediment on the 

 continental shelf after its depressions and liollows liave been filled up, 

 and it will not be much depressed by the weight of the sediment after it 

 has been once fully developed. The probability is therefore that its level 

 vxill remain fairly stable, while there is a slow upheaval of the emerged 

 land inside to compensate for its denudation by subaërial erosion, and a 

 slow subsidence of the sea-floor outside caused by the deposition of sedi- 

 ment. As the general sea-level gradually rises and the depth of water 

 over the continental shelf increases, it will be slightly depressed by the 

 increasing weight of this water. 



If the submerged shelf of the continents has been developed in a 

 manner somewdiat similar to wdiat has been indicated above, it is also 

 fairly easy to understand how it is possible that there are two wideh' 

 extended formations, which seem to indicate two distinctly different levels 

 at wdiich the shore-line of the Ocean has remained for very long periods. 

 The one formation is the low continental plains, which rise gentlv inland 

 from present sea-level, and the development of which would be extremely 

 difficult to understand unless we assume that the general sea-level has 

 remained more or less the same as now during long geological ages. The 

 other is the continental shelf which also indicates a sea-level and which 

 must have required a very long time for its development. The levels of 

 these two planes are as a rule distinctly different, and the difference 

 between them is often marked by a comparativelv steep descent from the 

 coast, or in Norway from the edge of the strandfiat, down to the inner 

 surface of the continental shelf. 



Both plains have been formed at about present sea-level more or less, but 

 while the continental shelf has been somewhat depressed and is more and 



