ICSI. No. II. THE STRANDFLAT AND ISOSTASY. 239 



This Stage may have lasted for some time and during tliat period 

 tlie surface of the continental shelf was to a large extent above sea-level 

 and was exposed to suhacrial denurlation, fluvial erosion, and to a vigorous 

 shore erosion by frost, which ha\e left their marks on this surface. 



I have previously [cf. 1904, pp. 151 f.î pointed out that the longitu- 

 dinal arrangement of submerged valleys and fjords in the inner regions 

 of the continental shelf of Norway must stand "in genetic relation to the 

 tectonic structure of the underlying rocks", and that this fact is "conclusive 

 evidence that the underlying ground of at least the innermost part of the 

 shelf is solid rock at no great depth below the surface". And I furthermore 

 pointed out 'cf. 1904, pp. ^j f.] that these longitudinal valleys, following 

 directions parallel to the coast and to the direction of the Caledonian 

 mountain folding, "must owe their prime origin to the subaërial erosion 

 of rimning water", because it is hardly conceivable that the glacial erosion 

 alone would excavate such valleys at right angles to the direction of the 

 general glacial movement, unless the glaciers were to some extent guided 

 by initial fluvial valleys. 



This means, however, that the least the inner part of the continental 

 shelf must have been above water when these initial fluvial valleys were 

 developed. This may to some great extent have occurred during preglacial 

 periods: but it is also probable that by the emergence of the shelf during 

 the glacial periods, there has been some fluvial erosion of these valleys. 



\Mien the ice-caps increased and extended outwards, the shelves were 

 graduallv more or less covered by the ice. They were then depressed in- 

 stead of being upheaved, and the peripheral belt of upheaval was gradualh- 

 shifted outwards. During the last glacial period this was obviously the 

 case in the inner part of the broad continental shelf outside the coast of 

 Helgeland and the Trondhjem region and also to some small extent out- 

 side the coast of the Xordmor and Romsdal region. 



During the maximum development of the Pleistocene ice-caps the 

 whole of these shelves were obviously covered by ice, and they were then 

 much depressed, and were probably also much eroded by the glaciers, at 

 least in some regions, c. g. outside Helgeland and the Trondhjem region, 

 where the surface of the shelf was thus much lowered. 



The Deposition of Sediment has gradually raised the general 



Sea-Level. 



If the continental shelves of the world cannot have been initially 

 formed and developed to their great width, and if their rocky planes 

 cannot have been cut in solid rock during the comparatively short periods 

 when the general sea-level was lowered by the formation of the Pleisto- 

 cene ice-caps, the question still remains open how and when were they 

 formed. 



