62 ^v. CROSS — wind erosion in the plateau country 



sandstones, with soft strata above and below them, are among the most 

 widely distributed formations on either side of the Colorado river. The 

 climatic conditions of the high plains near Grand river are common to 

 much of the Plateau country ; hence it seems evident that if deflation has 

 been effective in the area between the Abajo and La Sal mountains it 

 must be assumed to have done important work in many other districts. 



The stupendous erosion of the Plateau country represented by the Colo- 

 rado canyon and its tributaries has been the subject of much discussion. 

 It has seemed to some physiographers that such a gigantic task could not 

 have been accomplished under existing climatic conditions, always assum- 

 ing water to have been the only transporting agency. With this idea, 

 recourse has been had, notably by Dutton,^* to the hypothesis that a more 

 humid climate prevailed during the principal epoch of canyon erosion. 

 In a recent discussion of this question by Davis^^ it is held that even 

 under existing conditions the topography of the Grand Canyon district ia 

 adequately explained as due to water transport of land waste. In no 

 discussion of this question is the process of deflation treated as of impor- 

 tance. Davis refers to a suggestion made to him "hy a correspondent 

 well versed in the topography of arid regions" (Walther ?), that wind 

 action has been an important agency in producing the huge amphitheaters 

 of the Colorado canyon, but is unable to accept the suggestion in the 

 case of those forms "inasmuch as their slopes are always developed in 

 accordance with lines of gravitative action, and not in sympathy with the 

 flowing lines characteristic of the bottom of an air current." He admits 

 that "the wind is a powerful agent in regions where vegetation is as 

 scanty as it is on the barren walls of the Colorado canyon."^* Davis does 

 not discuss the effect of deflation in the localities where the wind is ad- 

 mitted to have been "a powerful agent." 



In all probability the relative importance of wind and water trans- 

 portation in the Plateau country has not been discussed because satisfac- 

 tory criteria for distinguishing them and for measuring the wind work 

 have not been recognized.. It is hoped that the foregoing brief statement 

 of observed facts, together with the interpretation which has been ad- 

 vanced as seemingly most reasonable, may serve to draw the attention of 

 special students to an important and hitherto almost wholly neglected 

 line of investigation in the wonderful province of Plateau and Canyon 

 adjacent to the Colorado river. 



" C. E. Dutton : Tertiary history of the Grand Canyon district. Monograph II, U. S. 

 Geological Survey, 1880. 



'" W. M. Davis : An excursion to the Grand canyon of the Colorado. Bull. Mas. 

 Comp. Zool., vol. .\xxviil, 1901, pp. 187-192. 



'" W M. Davis : An excursion to the Plateau province of Utah and Arizona. Ibid.. 

 vol. xlii, 1903, p. 34. 



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