40 



IKIDI \(>y NANSKX. 



M.-N. Kl. 



If W. C. Brøgger [1905] is right in assuming tliai the coasts of 

 Christiania Fjord were still rising fluring the first part of the Bronce- 

 age, but attained their present level towards the end of that age, we may 

 assume that the ledges of the present shore of the Fornebo Peninsula 

 have had about 2500 years for their formation. 



The ridges along the outer edge of the shore-ledges, rising above their 

 inner floor, which are so conspicuous on the ledges in Kvænangen Fjord 

 (Fig. 16) and of which there are also traces on the ledges of the Fornebo 

 Peninsula (Figs. 17 and 18), appear to be a common feature on shore- 

 ledges formed by frost erosion. They occur frequently on the lateglacial 

 and postglacial raised beaches of Norway, where especially O. E. Schiøtz 

 [1894] has called attention to them. They are also mentioned by other 



Fig. 19. 



writers. J. H. L. Vogt and J. Rekstad [\'ogt, 1900, p. 73] state that near 

 the outer edge of the shore-ledges in Helgeland, 10 to 20 metres broad or 

 more, rocky nabs frequently rise one or two metres above the general floor 

 of the ledges (c. g. on Leka in Helgeland). They are obviously formed by 

 the greater effect of the disintegration by frost on the inner part of the 

 ledge, where the accumulation of ice and snow remains longer, while it is 

 more easily washed away by the waves along the edge. On the inner part 

 of the ledge the accumulation of ice and snow (Fig. 19, i) may thus erode 

 the rock down to a lower level without being disturbed by the waves, as 

 is demonstrated in Fig. 19, A and B. 



The raised beaches of Norwa}^ have obviously, as a rule, been formed 

 by shore erosion by frost, in a similar manner as the strandfiat, but during 

 relatively short periods. 



Already F e i 1 d e n and De Ranee [1878] pointed out very clearly 

 the great importance which the disintegration by frost and the ice-foot 

 must have had for the formation of the many raised beaches or shore- 

 ledges in Arctic regions. 



