where h is the thickness of the ice field, i is the length of the ice field, b is the width of the ice 

 field, 6j is the ice solidity. 



As we have seen, the loss of kinetic energy is expressed in the packing, smashing, and hum- 

 mocking formation. In the last process, part of the ice fragments move on to the ice, while a part 

 is crammed under the ice. In such a way, kinetic energy is transformed into potential energy. It 

 is necessary to note that kinetic energy, causing deformations of ice fields, is not the same at all 

 points of the ice field. At an external edge (figure 90) of the ice field, it is equal to 0; at point a, 

 at the same distance from the shore, it is equal to 



E,^h{l-X)b^i^. (7) 



Figure 90. Heaping on a vertical shore. 



Finally, at the shore, the kinetic energy is defined by formula (6). In such a way, the kinetic 

 energy causing the deformations increases along the direction from the sea edge of the ice field 

 toward the shore. It is clear that the work which can be produced due to the loss of energy by the 

 parts of the ice field which are more distant than the distance x from the shore can be shown 

 adequate only for a certain packing of the ice but not for its break-up. 



At a point situated at some distance from the shore, with a smaller x , the kinetic energy of 

 the left part of the field appears satisfactory, both for packing and for smashing of ice, but in- 

 adequate for formation of hummocks, and only beginning with a distance of significantly smaller 

 X from the shore can the kinetic energy appear adequate for all three processes: packing, break-up 

 and hummock formation. 



256 



