BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 21, pp. 565-598 October 13, i9io 



DEFLATION AND THE EELATIYE EFFICIENCIES OF EEO- 



SIONAL PEOCESSES UNDEE CONDITIONS 



OF AEIDITY^ 



BY CHARLES E. KETES 



(Presented by title before the Society December 29, 1908) 



CONTENTS 



Page 



Introductory 565 



General characteristics of the arid country 567 



Peculiarities of an arid climate 568 



Rock-weathering in desert regions 569 



Limitations to geologic work ti water in arid regions 571 



Classes of erosional effec s 571 



General corrasive phenon.ena 571 



Role of the plains floodslieet 572 



Arroyo-running 575 



Influence of through-flowing streams 575 



Deflation of arid lands 580 



General considerations 580 



Destructive versus constructive eolation 581 



Plains-forming tendency of wind action 581 



Degradational character of deflation 583 



Extralimital effects of deflation 583 



Extent and volume of eolian transportation 584 



Importance of deflative process 585 



Comparative effects of corrasion and deflation 585 



Initial physiographic conditions of the arid country. 587 



Governing factors of an arid cycle 587 



Arid cycle in a mountainous region 589 



Arid cycle initiated in a plains region 592 



Recapitulation 597 



Introductory 



The desert has given us the two great laws on which rests the entire 

 scheme of ancient and modern landscape evolution. Arid regions have 

 supplied the fundamental data for a general plan of land sculpturing 

 that is in its nature strictly genetic. It is, indeed, as recently stated, a 

 notable fact that the waterless waste should furnish us first glimpses of 



1 Manuscript received by tlie Secretary of the Society August 16, 1909. 



XL— BULL. Geol. See. Am., Vol. 21, 1909 (565) 



