192 GLACIOLOGY 



SUMMARY 



This completes the cycle in the history of this sea ice. It may be noted that the 

 sea ice is important, both as a geological and meteorological factor, by covering over 

 with a thick, non-conducting layer the relatively warmer surface of the sea itself 

 The immediate effect of its formation is to greatly lower local temperatures ; when- 

 ever, as the result of a blizzard wind, the freshly-formed ice was disrupted and 

 driven out temperatures at once rose at Cape Royds. The geological importance of 

 sea ice appeared to us to be generally the following : — 



1. During the autumn, winter, and early spring it exerts a protective influence 

 on the shore-line as it checks marine erosion, but when later it becomes broken up, 

 the drifting floes grounding along the coast accomplish a very limited amount of 

 mechanical erosion. 



2. Biologically this action is important, as it checks the development of a true 

 shallow water littoral fauna, and accounts for the absence of the shelly beaches so 

 common in temperate and tropical latitudes. 



3. It forms a gathering ground for a considerable amount of drift snow, blown 

 ofl" the inland ice fields of the Great Ice Barrier. 



4. When broken up the floes bear out with them northwards vast quantities 

 of finely divided wind-blown rock debris, together with occasional larger blocks 

 which have fallen from rock cliffs. By transporting these fragments some distance 

 from the shore seawards, the sea ice, when it melts, sheds a very large quantity 

 of angular rock material, remarkably free from decomposition, on to the marine 

 organic muds of Ross Sea and the adjacent southern ocean. 



