290 FRIDTJOF NANSEN. M.-X. Kl. 



XVII. ISOSTASY. 



iriiat Is the cause of the lale-^laeial siihjuergence and the postglacial 

 upheaval of the land in Fenno-Seandia, Spitsbergen, Scotland, Iceland, 

 Greenland, and North America? 



T. 1^". Janiieson \vas the first to su,!;;fjcst 1 1865, 1882, 1887 tliat tlie 

 eartli's crust liarl been flcprcssed !)>■ tlic loarl of tlic icc-cai)s, and tliat the 

 postglacial upheaval of the land was due to the removal of this hjad. 

 N. S. Shaler [1874I, evidently without knowing Janiieson's first paper, 

 gave a similar explanation of the (|uaternary changes in the level of 

 the land. 



After this theory had been sujiported l)y the investigations of Gilbert 

 [1882, 1890] and of ]\ussell [1885] in the Uniterl votâtes, and especially 

 by Gerard de Geer [1888. 1890] in Sweden, and by Andr. M.Hansen [1890] 

 in Norway, it has more and more universally been accepted by geologists. 



The fact, provcl by the strandfiat and l)y the raised shore-lines, that 

 the coast of Norway has been depressed during the last glacial period, 

 and has again in postglacial time risen to a level slightly higher than the 

 level it harl before the subsidence, while the upheaval of the land is not 

 yet completefl in the central and Baltic regions of the depressed area, 

 which after the retreat of the ice was covcreri by a thick layer of sea, 

 seems to me to form convincing evidence of the correctness of the theory 

 that it was the load of the ice which caused the depression of the crust, 

 and the unloading which caused its upheaval. I do not think that serious 

 objections can any longer be raised against this theory. 



It is, therefore, hardly necessary to spend luuch time in discussing 

 the other attempts made to explain the cause of the postglacial upheaval 

 of the land, e. g. the suggestion that it was flue to a rise of the temperature 

 of the earth's crust after it had been cooled by the ice-cap — or that it 

 w-as due to some kind of tangential pressure in the earth's crust similar 

 to that causing mountain-folding [R. Sieger 1993, A. G. Nathorst 1894] 

 — or that the upheaval of the land was ncn real, but that the appearance 

 was produced by the sinking of the sea which had been attracted by the 

 mass of the ice-cap [Penck 1882]. 



The first explanation is sufficiently disproved by the fact that e. g. 

 in northern Fenno-Scandia and in Spitsbergen the temperature of the 



