HUMMOCKY ICE: (I.AAc )— Hummocked ice. 



HUMMOCKY POLAR ICE: (I.A.4.C.)— Polar ice that has been hum- 

 mocked. 



HUMMOCKY WINTER ICE: (I.A.4.C.) — Ice one year old or less that 

 has been hummocked. 



ICE: (I., II., or V.B.) — The solid state of water formed either by freezing 

 or sublimation. 



Ice encountered at sea consists for the most part either of icebergs 

 or other land ice originating from continental ice sheets and glaciers, 

 or of sea ice formed by the freezing of the top layers of the sea itself. 

 Sea ice proper accounts for probably 95 percent of the area of ice 

 encountered at sea, but icebergs are important because of the manner 

 in which they drift far from their place of origin, constituting grave 

 menaces to navigation. A certain amount of ice also may originate in 

 rivers or estuaries as fresh-water ice, but it is in a state of decay by the 

 time it reaches the open sea and is of local importance only. See 

 land ice, river ice. 



ICE APRON: 



(1) (II.A.l.a.) — Ice which is in part an accumulation of drift snow 

 and in part the refreezing of thaw water from an ice sheet or glacier 

 above, connecting with avalanche ice below (Fig. 70) . 



(2) (II.A.l.d.) — Area of snow and ice on cirque walls. Cf. ice 

 tongue. 



ICE ATLAS: (V.A.)— A series of charts showing geographic distribution 

 of ice, usually by seasons or months. 



The "Ice Atlas of the Northern Hemisphere," H.O. Pub. No. 550, 1946. 

 is a good example. Cf . ice chart. 



ICE BARRIER: (II.AAa.)— Ice cliff. 



ICEBERG: (II.A.5.a.) — A mass of land ice that has broken away from 

 its parent formation on the coast and either floats in the sea or is 

 stranded on a shoal. The many different types of icebergs may be 

 classed either as (1) tabular, generally derived from shelf ice, or 

 (2) irregular, generally derived from glacier ice. 



Names assigned to iceberg types depend upon either the content of 

 the iceberg or its form. The names most frequently used are: Pin- 

 nacled, arched, valley, drydock, blocky, tilted, weathered, glacier, 

 black and white, sugar, tabular, barrier, neve, unconformity, 

 ice island, and dome-shaped. 



In general, tabular icebergs having flat tops and angular contours 

 are found in the antarctic, whereas the irregular, pinnacled icebergs 

 are products of the arctic. Weathering, however, can alter the size 

 and shape of an iceberg to such an extent that it can no longer be 

 identified by form alone. 



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