14 FKID'IJOF NANSF.N. M.-X. Kl. 



at about present sea-level? If, after that great elevation (250 — 300 metres 

 hif,Hier than now) when the valleys were l;ase-levelled on the continental 

 shelf, the land was suhnierj^a'fl, the valleys were naturally als(j more or 

 less submerged, and their floors would be jjelow sea-level near the coast. 

 There would tlius be no possibility of base-levelling the valleys in this 

 coast zone, as they were already deepened below base-level. 



It might then be assumed tliat the elevation of the land occurred 

 after the valleys of the present land-surface had been base-levelled and 

 'the distal Ijase-levellerl plain' had been formed. But if so the land must 

 have stood at that higher level for a considerable time, sufficiently long 

 for the base-levelling of the fluvial valleys of the shelf, and after that 

 the land has again sunk to its previous level, or the shore-line has returned 

 to the same level wdiich it had during the very long period wdien A.'s old 

 valley generation was base-levelled. But what kind of movements is it 

 that has changed the level of the shore-line in this peculiar way, and after 

 such a long time brought it back to its original level? A. cannot be seen 

 to have considered this difficult question, which his theory must inevi- 

 tably raise. 



There is also another difficulty which he does not mention. He 

 thinks that the inner part of the continental shelf "constitutes an imme- 

 diate continuation of the coastal zone, thus l^elonging to the peripheric 

 base-levelled plain" [1919, p. 211]. But how is this to be understood? 

 Was the plain of the continental shelf base-levelled at the same time as 

 his old valley generation further inland was base-levelled? But the level 

 of the latter, is now^ near present sea-level, and is considerably higher 

 than that of the former. How then could extensive formations, so sharply 

 marked as the strandfiat, and the floors of his old valley generation, be 

 so well developed at this base-level, when there was also another lower 

 base-level (before or after?), represented by the inner part of the con- 

 tinental shelf? A.'s ideas do not seem to be very clear on this point. 



His views of the genetic origin of the continental shelf shall not be 

 taken up for discussion here. A factor of much importance for this and 

 other questions dealt with in A.'s treatise, is the isostacy of the earth'.^ 

 crust, which, however, he does not mention. 



The conclusions arrived at concerning Ahlmann's views of the nature 

 of the Norwegian strandfiat, may be summarized as follows: 



A. is right in assuming that the subaërial denudation (i. c. atmo- 

 spheric weathering, frost disintegration, and fluvial erosion) has been of 

 chief importance for the denudation of the Norwegian coast land, as well 

 as for the land slope within. This is in full accordance with the views 

 of several previous writers. 



A. is wrong in assuming that the Norwegian strandfiat, forming often 

 a sharply marked horizontal incision in the mountain slope, has been 



