44 P^KIDJJOP^ NANSEN. M.-N. Kl. 



energy. 1'lnis both processes, the liorizontal shore erosion by frf>st and 

 waves, and tlic vertical wave erosion on tlic- sul;nierge'l j^art of the shore - 

 plane, will go on simultaneous!}', and will continue llieir gradual march 

 landwards. 



This is the probable genesis of the typical Arctic shore, which we find 

 in many regions where the sea-level has remained fairly stable for a suf- 

 ficiently long time. I may instance the north coasts of Russia and Siberia. 



Wilhelm Ramsay describes [1900, pp. 59 f.] an illustrative example of 

 such a flat shore formed at present sea-level on the northern coast of the 

 Ribachi Peninsula (Fisher Peninsula, Murman Coast). This shore-plane 

 (Fig. 20) is emerged at low-tide to a breadth of 50 metres, and is cut in 

 black clay-slates, wdiich is easily disintegrated by frost. This coast has a 

 severe climate, but is at the same time exposed to the violent surf of the 

 open and stormy northern ocean. 



Although the frost is the chief causal agent for the formation of the 

 shore-ledges, the aid of an effective wave erosion is thus necessary in order 

 to develop these ledges into broader shore-planes, because on the one hand 

 the waves must wash away the débris of the frost erosion, and on the other 

 hand they must denude the outer part of the planes sufficiently to get 

 access to their inner parts. 



Though the shore-ledges may be easily formed in fjords and sheltered 

 sounds, it is thus obvious that the best conditions for the development of 

 extensive shore-planes must be along the open, outer coast, exposed to the 

 full force of the wave action of the open sea, and where also the land 

 generally is lowest and most dissected into islands, so that there is much 

 less rock to be cut away. 



The rate of the wave erosion increases very much with the storminess 

 of the sea, it being proportional to something between the third and the 

 si.vtii power of the velocity of the wind [cf. Nansen, 1904, pp. 181 f.] pro- 

 vided that the latter has a steady landward direction. 



Thorolf Vogt, in his valuable paper on recent shore-ledges [1917, 

 p. 1 21 J, has already given expression for a view of the formation of the 

 strandfiat which is similar to what has been hefe described. He says: 

 "The forces developing shore-lines, work qualitatively very sharply limited 

 without removing very much rock, while the surf combined with frost 

 disintegration removes much greater quantities of rock without working 

 so sharply limited as to level. Where there is a vigorous surf in connection 

 with an intense disintegration by frost the necessary conditions prevail for 

 an abrasion of great dimensions, and this may be the point of view from 

 which one has to consider the development of the strandfiat." 



In the above discussion of the development of the strandfiat by the 

 joint action of frost disintegration and the breakers, the sea-level was 

 supposed to remain stable. If, however, the coast be slowly submerged 

 during this process, it is obvious that the frost disintegration as well as 



