I92I. No. II. THE STRANDFLAT AND ISOSTASV. 237 



Hence the general sea-level would be lowered about 24.5 metres in- 

 stead of 27.4 metres and the negative shift of the continental shore-line 

 would be 18 metres, provided that the coast would sink as much as the 

 average subsidence of the continents, which, however, is not probable. 



The values of tlie upheaval of the sea-floor and sinking of the con- 

 tinents found above are. however, maximum values. It would probablv 

 be a verv long time before the whole area of the continents were sunk. 

 For all practical purposes we may assume that only some parts of them 

 near the coasts would sink and this would substantially reduce the amounts 

 of the upheaval of the sea-floor and the subsidence of the continental 

 coasts. 



We may assume that the sinking of the general sea-level caused bv 

 the formations of ice-caps will at least be 70 per cent of the amount by 

 which the average depth of the Ocean is thus reduced, and the negative 

 shift of the general continental shore-line, outside the regions depressed 

 and raised by the weight of the ice-caps, will be at least 53 per cent of 

 the amount by which the Ocean depth is reduced, but as rule much more. 



The preceding computations are only rough estimates. They prove, 

 however, on the one hand that quite considerable changes in the average 

 depth of tlie Ocean mav have been caused by the formation of the Pleisto- 

 cene ice-caps and bv their melting, and on the other hand that the shifts 

 of the general sea-level and the general continental shore-line have been 

 at least 70 and 53 per cent of the amounts by which the depth of the Ocean 

 was changed. 



It is quite possible that during the maximum development of the 

 Pleistocene ice-caps the general depth of the Ocean was reduced by 150 

 metres. In that case the general sea-level would sink at least 105 metres, 

 and the nes:ative shift of the general shore-line would be at least 80 metres. 



The Lowering of Sea-Level during the Glacial Periods and the 

 Surface of the Continental Shelf. 



The (juestion is now, whether this lowering of the general sea-level 

 during the glacial periods can help us to explain the formation of the 

 continental shelves? My view is that, although the great glacial periods 

 may have lasted a very long time, the time would nevertheless not be 

 sufficient for the development of such broad formations as the floor of 

 the North Sea. the continental shelf west and south of Great Britain and 

 Ireland, Sec, not to speak of the continental shelf of Norway, Iceland. 

 Greenland, and the coasts of the North Polar Sea. It must also be 

 remembered that during the maximum development of the Pleistocene 

 ice-caps these northern shelves were to a great extent covered by ice, and 

 were more or less depressed. 



