OCEANOGRAPHY AND SEA-ICE 



deposits, there is a special southern zone of glacio- 

 marine sediments, which have been deposited from 

 glacier ice, icebergs, etc., during several hundred thou- 

 sand years. This zone extends as far north as the ice 

 drifts. Diatoms are very plentiful in Antarctic waters 

 but they are shrouded by the larger bulk of the glacial 

 debris. How^ever, just north of this latter zone is a 

 belt of diatom-ooze, which in its turn extends some- 

 what farther northward below cold currents. The 

 warmer waters supply globigerina (foramini feral) 

 ooze, and this extends farther south below warm cur- 

 rents. To quote Drygalski, "the distribution of the 

 bottom sediments furnishes evidence of the develop- 

 ment of the present and former currents." 



Formation of Sea-Ice 



According to C. S. Wright, the first stage in the 

 formation of sea-ice in the open sea is the production 

 of myriads of small ice plates in the body of the water. 

 These form a thick scum, and are akin in origin to the 

 frazil ice which forms in fresh- water rivers, or at- 

 tached to ropes in cooling sea water. The ice is much 

 less saline than the sea water, and the saltier water is 

 squeezed out, as it were, and sinks. This frazil ice 

 appears on the surface of the Antarctic seas about the 

 end of March. The crystals are squarish in shape and 

 up to half an inch across. The layer of horizontal 

 plates grows thicker and forms a feltlike mass. It is 

 not rigid owing to included layers of salty liquid. The 

 writer vividly remembers Captain Scott jumping up 

 and down on new sea-ice, only three or four inches 



163 



