542 C. R. KEYES THE GEOGRAPHIC CYCLE IX AN ARID CLIMATE 



gins to produce notable erosion effects. In the adaptation of the normal 

 humid-climate scheme of the geographic cycle to that of a glacial climate 

 the conditions postulated have not been those of a truly glacial climate, 

 but those of a mountainous region where glaciers are present, which is 

 a very different thing. 



The marked distinction between mountain glaciers and continental 

 glaciers, or inland-ice fields, is fundamental. This is especially empha- 

 sized by Hobbs.^° Physiographically this distinction is far-reaching. 

 The climate in the one case is not a glacial climate at all. The vigor 

 and extent of ice scorino; is more than commensurate with that which is 

 displayed by the other. If anything, the absolute amount of abrasion is 

 very much less in the last -mentioned instance. 



Continental glaciers seem to present conditions that are essentially 

 desert conditions. The advancement of the ice-margin is probably more 

 rapid through the constant outward drifting of the fine dry arctic snows 

 than by any general motion of the ice itself. Eecent observations in 

 Greenland and ilntarctica seem to leave little doubt of the existence of 

 anticyclone areas over these inland-ice fields. Xansen-^ and Peary-- in 

 particular call attention to it in the north, while Shackleton-^ furnishes 

 complete evidence of the existence of a South Polar anticyclone, which 

 20 years before had been advocated by Murray.-* The drifting of the 

 arctic snows is in all respects identical with the shifting of desert dusts 

 and sands. 



Formulated strictly according to boreal conditions and not on what is 

 really a humid-climate basis, the commonly recognized scheme of a geo- 

 graphic cycle in a truly glacial climate needs radical revision. It may 

 be that the glacial cycle could be with great advantage regarded as an 

 arid cycle. 



EeLATIONS of GLACIAL AND ARID EbOSION CONDITIONS 



In the paper read before the Geological Society in 1908^ I inciden- 

 tally compared the most striking effects of deflation in the desert with 

 tliose of the winter blizzard on our northern prairies, where fine ice-dust 

 and ice-sands take the place of mobile comminuted rock-waste. Were it 

 possible to extend the blizzard a week or a month, or repeat it at short 

 intervals for ^ longer period instead of a single day, the general plana- 



20 Characteristics of existing glaciers, 1911, p. 6. 

 ai First Crossing of Greenland, vol. ii, 1890, p. 496. 



22 Geographical Journal, vol. x, 1898, p. 233. 



23 Heart of the Antarctic, vol. ii, 1910, p. 18. 

 2* Geographical Journal, vol. iii, 1893, p. 1. 



25 Bull. Geol. Soc. America, vol. 21, 1910, p. 582. 



