SCIENTIFIC RESULTS 



99 



from the glacier front. Hellftiid (187G, p. 99) actually witnessed 

 the buoyancy process of calving — 



ail iiiiiiieuse dentate piece of the glacier turning over and over, and rearing on 

 its edge liigli up in tlie air in front of tlie glacier, then the moment it rose, large 

 towerlike jiarts of the latter fell down. On the following day one of the newly 

 formed icebergs was measured and found to he 89 meters in height, wiule the 

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



These observations were made on Jacobshavn Glacier, wliich it 

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

 many of its icebergs. Drygalski (1895, p. lOS), in agreement with 

 the buoyancy 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 follow^s : 

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

 sways back in the direction of the ])arent body, the foot of the berg 

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



The Manner in Which Glaciers Calve 



Figure 59. — The glacier in profile is usually grooved at the fjord water 

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

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

 while the underwater shelf is continually broken 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 protrudes 

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

 and suddenly saw 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 by the many disintegrating 

 processes which proceed during summer at a faster rate in the air 

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

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

 body of the glacier. The third class of calvings produces only 

 small bergs; the second class medium to large bergs: while the 

 first class calvings account for the largest run of bergs. 



Steenstrup (1883, p. 92) warns that too much emphasis should 

 not be placed 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 



