236 FRIDTJOF NANSEN. M.-N, Kl. 



case of an ahstractinn nf water frum llic sca 1j\' llic fonnatioti of ice-caps 

 oil land, the same compulation can he mafic, only in the inverse direction. 



It lias to he noticed tliat as the continental coasts are to some extent 

 raised or sunk hy the crustal movements, the iiej^^ative or positive shifts of 

 shore-hne will not corresj)ond to the clianges of the j^cneral sea-level, hut 

 will as a rule he somewhat smaller. 



For instance, hy a rlecrease of the avera.i^'e dejjth of the Ocean, the 

 sea-floor will he raised, whicli will reduce the sinking- of the general sea- 

 level accordiuLjl}-; hut the continental coasts will sink somewhat, which 

 will reduce the neg"ati\e sliift of tlie shore-line causeri hv the sinking of 

 the general sea-level. 



These reductions, however, will not he considerahle. 



T.et us take an example; let us assume that the thickness of the Ant- 

 arctic ice-cap is increaserl on the average 1000 metres. As the area of 

 the ice-cap is ahout 13 millions square kilometres, this would mean a 



13 



reduction of the average depth of the Ocean by — — xiooo = 36 metres. 



36 1 



Let us furthermore assume that the depression of the crust caused 



hy this increase of the ice-cap is compensated for by an upheaval of the 



sea-floor in a surrounding area which is four times the depressed area 



under the ice-cap. According to the formula given on p. 231 we have then 



the average upheaval (U) of the sea-floor in this area 



^, 1000 -0.9 900 



L -— — = = 60 metres. 



3 + 3/0-25 15 



As the area of upheaval is 52 millions square kilometres, this would 

 mean a reduction (r) of the sinking of the general sea-level by 



52 



r = x6o = 8.S metres. 



361 ^ 



Hence the general sea-level would be lowered 36 — 8.6 = 27.4 metres. 

 This reduction of the depth of the water of the rest of the Ocean, 

 with an area of 361 — 52 = 309 millions square kilometres, would cause 

 an upheaval of the sea-floor and a sinking of the continents. In order 

 to simplify our computation we will now leave the upheaved part of the 

 Ocean round the Antarctic out of consideration as we well may in this 

 rough estimate. If we assume that the area of the lowered continents be 

 J49 — 13= 136 millions square kilometres the upheaval (//) of the sea- 

 floor would be 



27.4 



3 + 3£^ X 3 

 •^ 136 



2.85 metres 



and the average subsidence (//) of the continents would be 



3p9 

 136 



/; = 3p9_^^2_g ^ g metres. 



