20 ll'.IDTIDT NANSFN. M.-X. Kl. 



IV. GLACIAL EROSION. 

 The Erosion of the Glaciers of the Inland Ice. 



It wc sliall try to form some idea as to what the importance of the 

 j^^lacial erosion may have l)een for the devehjpment of the strandflat, it 

 would be necessary to examine the mode in which the glaciers erode under 

 different circumstances, and their erosive effect upon the land surface in- 

 different regions. There will be no opportunity of making such a com- 

 prehensive investigation liere. We must lim't ourselves to some points of 

 importance for our special subject. 



There is a striking difference between, on the one hand, the remarkab'v 

 small denuding effect which the inland ices of the glacial periods have had 

 on the relatively level surfaces of central and eastern Norway, and the 

 greater part of Sweden, where, in many places, the depth of glacial erosion 

 may only amount to several metres, and, on the other hand, the con- 

 siderable dissecting work performed by the glaciers of the ice ages in the 

 coastal regions of Norway, where the valleys and fjords have been deepened 

 hundreds of metres. 



This remarkable difference of effect luust be chiefly due to differences 

 in the velocities with which the eroding ice has moved over the rocks, and 

 not appreciably to differences in its thickness and the pressure therebv 

 exercised on the underlying ground. 



A. G. Hogbom [1910, p. 435 f.] and other writers are obviously right 

 in assuming that the erosive power of a moving glacier is much less due 

 to its scouring effect upon the underlying rock tlian to its power of 

 breaking loose (plucking) stones from the rocky ground, and this power 

 obviously increases rapidly with the velocity of the ice motion. The ero- 

 sive effect of a glacier will also to some extent depend on its power to 

 move and transport stones and rocky material along the ground. ]Moreover. 

 a sufficiently thick glacier will have a disintegrating effect on the under- 

 lying rock by the alternate melting and freezing of water on its under sde, 

 caused by the frequent changes in the stress and pressure of the ice movirg 

 over the rough rock surface. 



I have tried to investigate quantitatively the various manners in which 

 moving glaciers may erode the underlying ground. The results of these 



