FRID'I.IOF NANSKN. M.-N. Kl. 



y\s a whole llie coni iiiciital sliclf is ohxiously a verv >>](] formation 

 (Icxclopc'il during; loiij^' j^coloj^ical |KTio(ls, to a ^reat extent prej^'lacial, 

 wliilc llic sliamlftat has been fIe\'eloped atter tlie first TJreat Ice Ag'e. 



/\ few points nia\ ]>v specially mentionerh 



Onr in\csli,i;ations of the Xorwej^-ian stranfjflat anr] the late-j^'-jacial 

 sLibmcrj^ence of ihe laml (see nt-xl chapter) pro\e the almost p^-rfect 

 isostacy (;f the crust. 



It seems then improbable that the initial laii'l in the region of the 

 continental shelf can on tlie averag'c have been ^■e^y high. 



( )ntsi(le I lel,<4e!an(l tliis shelf has a width of 250 kihjmetrcs, vcrv nearlv 

 e(|ual to thi- distance from the coast castwarrls to the central region of 

 Fenno-.Scandia wliere the land had its greatest late-glacial submergence 

 of 300 metres or more. Idiis shelf is consequently so broad that the crust 

 in that region must stand very nearly at its level of equilibrium. 



If the average specific gravity at the crorled surface rocks be 2.6, 

 that of tlie underlying ])lastic rock or magma, displacing the uplieaval {11) 

 of the crust, be 3, tlie tliickness of rock eroded be //, and the permanent 

 lowering by ere)sion of the level of the land surface be /, we have: 



MX3 = /1X2.6 

 / = h — n 



2.6 



/0 



7 



Hence m order to lower the average level of the land surface 100 

 metres it would be necessary to remove a layer of rock having an average 

 thickness of 750 metres. If the specific gravity of the underlying magma 

 be higher, the thickness of the layer of reck which had to be removed 

 would be smaller, c. g. with a specific gravity of the magma of 3.5, it 

 would be only 389 metres. 



As the planing of a shelf in solid rock by the joint action of subaërial 

 denudation and marine denudation is obviously a very slow process, 

 especially if it is not vigorously assisted by frost disintegration, and as 

 the continental shelf of Norway cannot be assumed to be of sufficiently 

 old age to make a vertical denudation of very great dimensions probable, 

 we may assume that the initial land in the region of the present continental 

 shelf was fairly low. 



It may, however, have been much more uneven, and there may have 

 been isolated parts or mountains rising to greater heights. The sub- 

 merged lower parts, the depressions and valleys, of this initial land, may 

 then in the course of time have been filled up with waste from the land, 

 and the crust mav thus have been depressed to a certain degree. 



There is also the possibility that in the outer part of the shelf there 

 is only a small amount of rocky ground, and that this part is chiefly 



