1921. No. II. THE STRANDFLAT AND ISOSTASY. 



VII. THE STRANDFLAT OF THE NORWEGIAN WEST 



COAST FROM THE REGION OF SOGNE FJORD 



TO THE REGION OF HARDANGER FJORD. 



The heights of the strandtlat g-iven in the following- descriptions 

 were determined by levelling-. In the summer of 191 i, in the Sogne Fjord, 

 along the Norwegian coast, and on the Shetland Islands, a small levelling 

 telescope and a levelling rod (4 metres long) were used. In the following 

 summer, on Spitsbergen, the same rod was used, but the levelling instru- 

 ment simply consisted of a U-shaped glass tube containing coloured water. 

 Where there was an opportunitv, the level was also determined by the 

 horizon of the sea. This is not a very accurate method, but as the 

 distances within which the measurements were made were never con- 

 siderable, the final error of a levelling thus performed hardly ever ex- 

 ceeded a metre. If the distances are greater the use of a telescope w'ould 

 greatly increase the accuracy of the measurement. 



The accuracy with which the heights of the strandfiat may be deter- 

 mined, does not, however, as a rule depend on the levelling method 

 employed. The real difficulty is in most cases to decide where the actual 

 level of the strandfiat is. Seen at a distance this level may look at if it 

 were quite sharplv defined; but coming near one often finds the surface 

 of the strandfiat to be uneven, with depressions and elevated ridges, 

 causing doubt as to what actually indicates the general level, and whether 

 it should be put perhaps one metre higher or lower, and sometimes 

 even more. 



As the strandfiat has been denuded by glacial erosion after its final 

 formation, it may be preferable in most cases to be guided more or less 

 by the elevated ridges, if their summits are lying approximately at equal 

 heights. But on the other hand, the surface of the strandfiat may originally 

 have been fairly rough, and ihe ridges may have been higher than the 

 general level. It will, therefore, often be a question of personal judgement 

 what the correct height should be estimated to be. 



Another difficulty is the determination of the present shore-line on 

 which the levelling is based. Most observers have used the uppsr fucus 

 limit in the shore as a base, whicli nia\' have great advantages. But this 



