54 LAUGE KOCH 



on it. The water streaming out from under the glacier is dammed up 

 until, the equilibrium being disturbed (most frequently at spring 

 tides), water and bergs are pushed out of the fiord with catastrophic 

 force. Sea ice never prevents the catastrophe. The sole example 

 is the ice fiord at Jacobshavn.^ 



4. Bergs are formed once a year. — The front of the glacier is 

 blocked up by sea ice part of the year, so a wall of compressed 

 icebergs is formed in front of, and on, the glacier. In the course 

 of the summer the ice melts off, the bergs often break away with 

 great violence, are shattered, and float away. Porsild has taken 

 the description of the Tormkatak Glacier as the type, but nearly 

 all productive glaciers in west Greenland belong to this type. 



5. Bergs are formed at intervals of a few years. — In deep bays 

 and fiords of Melville Bay sea ice floats out only in particularly 

 warm or windy summers. The front of the glacier is thus for a 

 brief succession of years blocked up by sea ice so that the bergs 

 accumulate on top of each other, forming an ice conglomerate 

 which freezes into one block after each summer. By degrees a 

 barrier of crowded bergs forms in front of the glacier, and when 

 this barrier of ice conglomerate finally floats off, it may be carried 

 far and wide before it is suddenly scattered into small fragments. 

 In years when there is no ice, more particularly, this kind of berg 

 is very common in the north of Melville Bay. 



6. Bergs are formed at intervals of many years. — The sea ice 

 remains so long before the front of the glacier that the bergs are 

 fused into a huge ice field with a level surface and without any 

 sharp boundary line toward the glacier at the rear. Toward the 

 perennial sea ice, however, there is still a boundary line. In this 

 way many kilometers of the glacier tongue may float upon the 

 water. The Ryders Glacier in Sherard Osborne Fiord is an example. 



7. Permanent sea ice prevents the formation of bergs. — On account 

 of the climatic conditions at the inner end of deep fiords, the sea 

 ice as well as the projecting tongue of the glacier increase in height, 

 the annual precipitation finding no outlet. For this reason no 



' This and the following type have been described by M. P. Porsild in "Om de 

 gronlandske Isfjordes saakaldte Udskydning," Geografiska Annaler, Ang. I, Haft i, 

 Stockholm, 1919. 



