OCEANOGRAPHY AND SEA-ICE 



wide and eight hundred yards long along the central 

 split. The inner end had been shoved up some six 

 feet by pressure from the east. The whole structure 

 was floating. Another example occurred just south- 

 west of Cape Roberts. (See Punch Bowl, Figure 24.) 



Ice Foot 



This structure is a narrow shelf of ice adhering to 

 the coast line. It varies in width from a foot or two 

 to a belt of ice one hundred yards wide. It forms best 

 on shores which have a gentle slope, and roughly speak- 

 ing the width depends on the extent of shallow water 

 within the one- fathom line. 



Its formation is closely bound up with the position 

 of the tide crack, and with the direction of the pre- 

 vailing wands. As the sea-ice becomes thicker the dis- 

 tance of the tide crack from the shore tends to become 

 larger, for the maximum shear in the ice is, of course, 

 just where the moving sea-ice reaches the solid rock. 



The sea-ice between the tide crack and the rock is, 

 of course, held firmly by its attachment to the latter, 

 and this fixed belt of sea-ice constitutes the ice foot. 



From the above considerations it will appear that 

 the ice foot is in general wider where the shore is 

 shallow, and this is generally true. Also where the 

 shore consists of a vertical cliff there is rarely an ice 

 foot, and the reason is obvious, for the cliff itself forms 

 the logical boundary between moving ice and fixed 

 coast. 



But the above simple explanation is complicated by 

 the action of wind and spray. In gales, w^hen the tem- 



169 



