1 92 1. No. II. THE STRANDFLAT A\D ISOSTASY. 221 



glaciers, the land has been somewhat raised by isostatic movement to the 

 new level of equilibrium after the disappearance of the ice cap of each 

 glacial period. 



It is not known how many Pleistocene glacial periods there mav 

 have been in Norway. But considering that at least four different glacial 

 periods are now established for Central Europe, it seems hardly probable 

 that there should have been less in Scandinavia. 



If the strandfiat has two distinct levels it seems to indicate that there 

 have been at least three glacial periods in Norway as was already assumed 

 by Oxaal [1914, pp.42 f., cf. above p. 48]. If there are actually three 

 different levels, it may indicate four glacial periods. 



If we assume that the changes of level are solely due to isostatic 

 movements of the earth's crust, and in no degree to changes in the sea- 

 level (caused by changes in the volume of the Ocean), it may seem diffi- 

 cult to understand why the heights of the raised strandfiat are so very 

 similar along the Norwegian coast and even on Spitsbergen, although the 

 quantities of rock removed may probably have varied much in the divers 

 regions of the coast. 



If we assume that the upper limit of the strandfiat is universallv at 

 some height between 30 and 40 metres above the sea, we would then have 

 to assume that the quantity of rock material removed from the surface 

 of the coast land corresponds to a continuous layer of rock with an aver- 

 age thickness of at least 36 to 48 metres, which has been removed after 

 the upper level of the strandfiat was first developed. This seems a great 

 deal. Although much thicker layers of rock have obviously been excavated 

 from the deepened valleys and fjords during this long period, the thickness 

 of rock removed from the high land surface, between the deep vallevs and 

 fjords, has probably not been very consideraljle. It is also striking that 

 the level surface of the strandfiat itself cannot have been much denuded. 

 On the other hand, if there have been at least two glacial periods, 

 and probably three, after the upper level of the emerged strandfiat was 

 developed, it is not inconceivable that the weight of the rock material 

 removed by the glacial erosion of the coast land during these periods 

 may go some way towards explaining the elevation of the strandfiat above 

 present sea-level. 



The submerged strandfiat offers, however, another difficulty to this 

 assumption. If, during some period before the last glacial epoch, this 

 part of the strandfiat was cut at a level actually lower, though slightly 

 lower, than the present sea-level, the level of the land cannot have been 

 permanently raised after that time, unless the general sea-level has also 

 been raised. 



To me it seems probable that, in addition to the isostatic upheaval 

 of the land, there have been chancres in the level of the sea. 



