ANTARCTIC GLACIOLOGY 335 



Bearing of the Present Antarctic Ice Cap on the 

 Pleistocene Ice Sheets 



It is through its relation to the Pleistocene ice sheets, and the 

 comparisons which its existence makes possible, that the Antarctic 

 continental ice has a more than purely scientific interest. There 

 are many questions to which the answer must be sought in Antarctica. 

 Modern theories of ice action can be tested only in the one region 

 where ice sheets of continental extent still maintain almost their 

 fullest development. It is in Antarctica alone that all the main types 

 of land ice are met with today. Three of these, in particular, the 

 largest and the smallest, the continental ice, the shelf-ice sheets of 

 the coast, and the tiny scooplike and cuplike drifts and cwms, present 

 problems which are of particular interest both in themselves and as 

 representatives of similar conditions elsewhere in the world. 



A sheet of continental ice comparable in size with the European 

 and North American Pleistocene ice sheets is found in Greenland as 

 well as in Antarctica today, but it is the latter alone which not only 

 occupies the continent on which it is based to its uttermost limits 

 (if we except a few wind-swept promontories mostly of recent volcanic 

 origin) but spreads out into the sea, adding some hundreds of thou- 

 sands of square miles to the effective "land" area. In one respect 

 both the Greenland and the Antarctic ice sheet are better compared 

 with the Pleistocene continental ice of Europe than with that of 

 America, for the latter spread out and thinned out mainly over 

 lowlands, while the former ended abruptly, on one side at least, in 

 the sea, as also do its modern rivals. Only in the Antarctic — indeed, 

 so far as we know, only in the Ross Sea sector of the Antarctic — is 

 there anywhere a true parallel, in importance and extent, to the ice 

 sheet that formerly filled the North Sea and deposited its load of 

 boulders, including the unique "rhomb porphyry" from Scandi- 

 navia, across the lowlands of East Anglia and even pushed them up 

 the slopes of the uplands of the Lincolnshire and Yorkshire coast. 



Study of Ice Erosion 



It is unfortunate for our study of glacial erosion that the continent 

 of Antarctica is so symmetrical in shape. The ice sheets everywhere 

 push out and persist until they float upon the sea, and the accumulated 

 debris of the erosion of the Ice Age is deposited beneath the water 

 and thus successfully hidden from the gaze of man. The tendency 

 of the Antarctic explorer has thus been to adopt a very conservative 

 estimate of the power of ice to erode. There are, however, hints 

 that a systematic survey of the deposits of the sea bottom would 

 give us a much truer view of the eroding power of the ice sheets at 

 their maximum, when the outward flow of the glaciers must have 



