BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 23, pp. 537-562 NOVEMBER 9, 1912 



DEFLATIVE SCHEME OF THE GEOGEAPHIC CYCLE IN AN 



ARID CLIMATE ^ 



BY CHARLES R. KEYES 



(Presented before the Society December 29, 1911) 



CONTENTS 



Page 

 Introductory 5.38 



Controlling erosional agents under diverse climatic conditions 539 



Preparation of rock materials for erosion 539 



Effectiveness of water action in a moist climate 540 



Dominance of wind-scour in a dry climate 540 



Extent of ice scoring in a glacial climate 541 



Relations of glacial and arid erosion conditions 542 



Essential features of aridity 543 



Contrasted characteristics of arid and humid initial conditions 543 



Surface offered to sculpturing agencies 543 



Antecedent rivers of desert regions 544 



Consequent drainage features 545 



Centripetal drainage 545 



Migration of basinal wash 546 



Initial relief features under aridity 548 



Contrasted features of arid and humid topographic juvenility 548 



Conditions generally postulated 548 



Youthful arid stage under deflation 549 



Ideal type of early arid stage 550 



Certain characteristic deflative features 551 



Certain peculiarities of arid youth 551 



Mature stage of arid relief 554 



Deductive course of development 554 



Mature arid features under deflation 554 



Development of original drainage lines in desert ranges 555 



Duration of arid maturity 557 



Prevalence of old age in desert regions 559 



Postulated characteristics .- 559 



Topographic features of old age under deflation * 559 



Baselevel of eolian erosion 559 



Normal water action in desert regions 560 



Recapitulation 562 



1 Received by the Secretary of the Society March 25, 1912. 

 Read by title under the caption "(leofrrapbic cycle in an arid climate : Should its 

 development be by wind or water?" December 29, 1911. 



(537) 



