SCIENTIFIC RESULTS 



99 



from the fjlacier front. Helland ( ISTG, p. 99) actually witnessed 

 the buoyancy process of calvin<!: — 



an immense dentate piece of tlie glacier turning over and over, and rearing on 

 its edge high up in the air in front of the ghicier. then the moment it rose, large 

 towerlikc jiart.s of the latter fell d(»\vn. ( )u the following day one of the newly 

 formed icehergs was measured and found to he 89 meters in height, while the 

 height of the glacier wall hardly exceeded 4i> meters. 



The.se observations were made on Jacobshavn Glacier, which it 

 will be recalled is one of the few glaciers whose front is lower than 

 many of its icebero:s. I)ry<ialski (I.S95, p. 402), in agreement with 

 the buoA'ancy theory divides the calving into three classes. The first 

 class includes large detachments of the front, from top to bottom, 

 unassisted by previous fragmentation, and described as follows : 

 The front face of the glacier slowly rises above the main portion, 

 sways back in the direction of the parent body, the foot of the berg 

 shooting forward and then settling down in the fjord, rolling back 



The Manner in Which Glaciers Calve 



FiGUKE ."19. — The glacier in profile is usiuilly grooved at tlie fjord water 

 line, causing an overliaiiging upper and a jutting lower under- 

 portion. The ice of the upper ledge detaches by its own weight, 

 while the underwater shelf is continually liroken away by its own 

 buoyancy. (Drawing after Russell in Kayser, 1928.) 



and forth several times. Calvings of the second class refer to the 

 breaking away of a submarine toelike underbody which })rotrudes 

 into the fjord. Drygalski states that he heard a tremendous roar 

 and suddenly savr an iceberg breach out of the water beneath and 

 directly in front of the glacier wall. The underwater projection of 

 the glacier front is presumably formed liy the many disintegrating 

 processes which proceed (hiring ^-ummer at a faster rate in the air 

 above, than in the water below. Calvings of the third class are 

 simply pieces of ice breaking otf and falling down from the upper 

 body of the glacier. The third cla.ss of calvings produces only 

 small bergs: the second cla.ss medium to large bergs; while the 

 first class calvings account for the largest run of bergs. 



Steenstriip (1^88. ]). 92) warns that too much emphasis should 

 not be phiced on calving caused by the submergence of the outer end 

 of the glacier, calling attention to the .sensitive balance that he has 

 found out on the bottom of the fjord. The outer end of the ice 



