But in the course of the winter the ice heaps will grow firmer and firmer. The falling snow 

 fills the fissures and passages of the ice hummock; blocks of ice which form the ice hummock 

 settle and pass under their own weight. Together with the changes in temperature, the internal 

 deformations of the various pieces of the ice begin, increasing their durability. In such a way, the 

 winter ice hummocks are stronger than the summer ones and the older ones stronger than the 

 younger ones. 



Usually, toward the end of the polar summer, the flat yearly or annual ice is destroyed in the 

 regions of the fast ice and of the floating ice. Floating ice at this time is made up either of various 

 floebergs and hummocks or ice hummock fields and blocks. 



If toward the beginning of the new ice formation these high sections appear beaten down to- 

 gether they are folded and form "cauldrons"; if also toward the beginning of the ice formation they 

 appear scattered, a comparatively large distance from one another, they form more or less ice- 

 heaped fields. 



Cauldrons represent a very durable ice formation. In the course of the following winter, they 

 thicken and settle. Only in a few cases are they smashed into separate parts, for in the majority 

 of cases they represent the beginning of perennial pack fields. Being carried out by the currents 

 from the bordering seas into the Central Arctic Basin, they enter for the future into the packed 

 ice as composite parts. In the bordering seas of the Arctic Basin, cauldrons are destroyed in some 

 only in exceptional years. In the north part of the Barents and Kara Seas, it is not a rarity to meet 

 cauldrons of 2 or 3 years growth. In the Chuckchee Sea it is almost possible to meet yearly blocks 

 of perennial ice with a height of 4 to 5 m, the draught of which is 10 to 12 m. The ice fields which 

 consist of young ice with spots in them of nesiak are much less durable: in the course of winter 

 they are repeatedly broken up along the lines of the least resistance, which are, in the majority of 

 cases, thermal fissures and lines of solder. 



Figure 96. A scheme of the structure of a hummock according to Burke. 



As we have seen, the forms of the hummocks as a result of complete breakup, marginal 

 crushing and pushing of one ice field on another are quite different. The hummocks of the pushing 

 type are made up of the largest ice slabs and it is natural that the angle of slope and the height are 

 the smallest. The hummocks from marginal crushing are made up of large blocks sometimes of 

 very irregular forms. The hummock of complete breakup consists of fine blocks. Its height and 

 angle of slope appear the greatest. These hummocks are the most regular in form. 



269 



