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ridges, but owing to internal stresses an ice field does not necessarily 

 crack in its thinnest part. Thus, cracks are frequently found passing 

 through ridges and hummocks of considerable height. Thin half- 

 melted ice may be left holding, but this is in many cases destroyed if 

 the wind changes. 



REGROUPING OF ICE 



Any wind will tend to regroup ice that is more or less scattered over 

 a considerable area. As the wind rises, the separate floes form lines 

 in a direction at right angles to the wind direction. These chains 

 break up when the wind changes, and after a time realign themselves 

 at right angles to the new wind direction. When the wind blows from 

 the shore, a channel of open water usually forms between the coast 

 and the ice or increases in width if already existing. On the other 

 hand, a wind blowing on to a coast or on to fast ice tends to reduce the 



Figure 12. — Airplane photo of huge iceberg showing direction and effect of deep-water 

 currents. Although the berg stands about 280 feet above water, it extends more than 1,000 

 feet below surface and is affected by currents which run too deep to move neighboring ice. 



5*»- ^"• 





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