climate is less severe here and also because the slope of the valley is steeper, and therefore the 

 area of ice accumulation is greater. The fact that the main mass of Greenland icebergs is calved 

 between 65° and 75° north is explained mainly by the presence of this cross valley. 



LITERATURE: 62, 79, 143, 146, 171. 



Section 51. Icebergs 



The ends of glaciers, falling into the sea in a form of hanging walls or steep slopes in pro- 

 portion to their entry into the water, undergo a constantly increasing pressure of the water from 

 the bottom upward due to the low density of the ice. In connection with the periodic and non- 

 periodic fluctuations of the sea, this pressure first increases then decreases, and as a result, 

 chunks of ice of smaller or larger size break off from the end of the glacier. Icebergs, extremely 

 different in size and form, starting with small "pups" and ranging to tremendous "ice mountains, " 

 are formed in this manner. DrigalsMi considers that the end of a glacier can waste in three ways: 



In the first, a complete fissure going approximately across the end of the glacier is formed. 

 The broken-off monolith of ice, after several fluctuating movements at opposite positions of equilib- 

 rium corresponding to its form, becomes an iceberg carried from place to place by marine cur- 

 rents and wind. The largest icebergs are created in this way. 



The second method is characteristic during the summer for the comparatively southern lati- 

 tudes, particularly in Baffin Strait. If the summer wastage of the glacier end is greater on top than 

 its wastage in the water, then the arm of the glacier finally becomes an underwater shelf, which 

 extends for a considerable distance into the sea. In time, this underwater shelf breaks off and 

 floats up from the depths of the sea. It is clear that such "float-up icebergs" cannot be of a large 

 size. Aside from this, they are outstanding in the great erosion of their form. 



In the third form of end-glacial waste, large and small chunks of ice gradually break off from 

 its hanging wall and fall into the water. This method of wastage is especially characteristic of 

 slowly moving glaciers in the high latitudes and of ice-dome islands (see Section 53) . 



Every glacier falling into the sea can be characterized by its productivity, i.e., by the 

 amount of icebergs produced annually and also by the size and form of the latter. 



First of all, the productivity of a glacier is determined by the velocity of its flow. As a 

 whole, this velocity is always greater along the axis of the glacier (than along the edges) and in the 

 upper part (than in the lower) . 



The flow velocity of some glaciers in Greenland is extremely great. Thus, for instance, 

 Quarayaq Glacier, along the western shore of Greenland (70° north, 50° west), which is only 5 km 

 wide along its front, with an altitude of 100 m above sea level at the end of the arm, flows at a 

 velocity of 20 to 25 m per day, i.e. , at a velocity almost 20 times greater than the velocity of the 

 most rapid Alpine glaciers. Jakobshaven Glacier, located somewhat farther south, which does not 

 halt its activity even during winter and which yields, by computation, 1, 350 icebergs annually, or 

 about 10 per cent of all the Greenland icebergs, flows with the same velocity. 



In August, 1928, Smith counted 4, 000 to 6, 000 icebergs in the Jakobshaven fjord. It is noted 

 that after indeterminate periods of time, approximately ten times a year, a chain of icebergs (evi- 

 dently after breaking an ice dam which had formed somewhere), begins to move toward the exit 

 from the fjord, slowly at first but later at a velocity of 10 to 15 km/hr. All this is accompanied by 



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