848 



GEOLOGY 



the most marvelous features of the ice dispersion was the great 

 extension of the Keewatin sheet from a low flat center westwan 1 and 

 southwestward over what is now a semi-arid plain, rising in the 

 direction in which the ice moved, while mountain glaciers on the 

 west, where now known, pushed eastward but little beyond the 

 foothills. 



The Cordilleran ice-sheet is less simply defined. Much of it 

 occupied a plateau hemmed in by mountains, and plateau glaciation 



Fig. 561. Sketch-map showing the area of Europe covered hy the conti- 

 nental glacier at the time of its maximum development. (Jas. Geikio.) 



was complicated by extensive mountain glaciation of alpine type. 

 In some sense, the whole Cordilleran ice-sheet was the product of 

 a confluence of mountain glaciers deploying on the intervening 

 plateau; but there appears to have been plateau glaciation not 

 solely dependent on contributions of ice from the mountains. The 

 southerly lobes of the complex body of ice crossed the boundary 

 of Canada into the United States. Though hampered by its en- 



