234 FRIDTJOF NANSEN. M.-X. Kl. 



(i 



U ~ — 



3 



'l'lic final lowerinj^ of the ji^eneral sea-level would in that case be 

 al)(Ail iwo tliirds of the aiiKiunt hy which the averaj^e depth of the Ocean 

 was reduced. 



The al)o\'e formula for // will only be valid if perfect equilibrium 

 (jf the entire crust of the earth br restored. In that case the depression 

 of the crust in the regions of the ice-caps would be entirely compensated 

 for by the ui)lica\al of the general sea-floor, and no permanent changes 

 in the general level (jf the continents w(juld then be caused. 



As, however, the shifting of the plastic rock or magma underlying 

 the rigid crust is an extremely slow process, this state of perfect 

 c(|uilibrium is hardl\- ever attainerl. \Vhat wouUl actuall\- liappen may, 

 perhaps, be as follows: 



The immediate effect of the accumulation of water in the ice-caps 

 will be a sinking of the general sea-level to the full amount by which the 

 average depth of the Ocean was reduced. Then the isostatic readjustment 

 of tlie crust would gradually ])egin. 



The crust under the ice-caps would be depressed by the increase of 

 the weight of the ice-caps. This depression would cause a corresponding 

 upheaval of the crust in the areas surrounrling the ice-caps. If these 

 areas consist more or less of sea-floor, their upheaval will reduce the 

 sinking of the general sea-level accordingly. 



The reduction of the depth of the water in the other parts of the 

 Ocean will gradually cause an upheaval (//) of the sea-floor. This up- 

 heaval, wdiich is not compensated for l)y the depression of the crust in the 

 regions of the ice-caps, has to be compensated for l:)y the sinking of the 

 continents surrounding the Ocean. The upheaval ;/ of the general sea- 

 floor will then be: 



// = M 



3 



where M is a quantity determineii by the reduction of pressure at a 

 certain level under the continents due to their sinking. 



The following consideration may help to make this clear. 



If the globe were covered entirely by an Ocean, the increase or de- 

 crease of the volume (/. c. the depth) of this Ocean would have no effect 

 upon the level of the sea-floor. If, however, continents emerge above the 

 surface of the Ocean, the conditions are entirely altered. An increase of 

 the volume of the Ocean will then press down the Ocean floor and press 

 up the continents accordingly. 



If the average depth of the depression of the Ocean floor be ;/, the 

 average height of the upheaval of the continents be //. the area of the 



