SCIENTIFIC RESULTS 



61 



and studies on polar glaciology. It is mainly from this literature 

 that the following classification is taken. Practically all the various 

 forms in which glaciers have been observed may be classified as 

 follows : 



(a) Cachment, h(nuj(ng, eirqiw, or c\i-in^ a glacier occupying a 

 small depression on a slope. 



(Z>) Alpine. — The common valley glacier. 



{c) Plateau or highland. — Spreading from one or more cachment 

 basins over a level plateau. 



(d) Piedmont. — A coalescence of ice masses in cachment basins, 

 or of glaciers at the foot of a descent. 



{e) Inland ice. — All land forms hidden. 



(/) Ice-foot a/' snoir-di-ift glacier. — Wrapped about foot of 

 mountains. 



{g) Shelf ice. — Accumulation of snow on fast ice of protected 

 coastal shelf. 



A Comparison Between the Antarctic and the Arctic Ice Sheets 



Figure 31. — The protile of Antarctica, above, when compared with that of Greenland, 

 below, reveals a striking dissimilarity in the general form of the ice sheets. The 

 former with its marginal overflow, causes the ice to calve many huge tabular ice- 

 bergs. In the north, however, the ice edge characteristically ends on land, and 

 glaciers plowing across the uneven foreland produce irregular, picturesque-shaped 

 icebergs. (Figure after Priestley and Koch.) 



The first five forms have a wide distribution in polar regions, but 

 the last belongs to the antarctic. The ice-foot or snow-drift glacier 

 should not be confused with the ordinary ice foot which is so com- 

 mon in the north, the latter consisting of salt-water ice formed on 

 a chilled shore line near the tide line. (See p. 23.) The ice-foot 

 glacier is seldom found in the north. Differences in certain underly- 

 ing factors specific to the region develop corresponding differences in 

 the features of the ice. As an example of one of these agencies we 

 can point to the low mean annual air temperature which prevails 

 in the Antarctic. The Avarmth of the arctic summer has no parallel 

 in the far south and mainly because of this thermal difference the 

 ice sheets of the north polar regions are unlike those of the south- 

 ern. The margin of Antarctica's cap, overflowing its land support, 

 is free to spread over the sea until fracture detaches huge strips, 

 sometimes including 10 to 20 miles of its front. In Greenland, by 

 contrast, the edge of the inland ice ends on land, and glacier tongues 

 are deformed as they plough across the uneven foreland so that their 



