LINEAMENTS OF THE DESERT 



LINEAMENTS OF THE DESEET 



By De. CHARLES R. KEYES 



DES aiOINES, lA. 



OUE notions of the genesis of desert landscapes have lately under- 

 gone complete revision. In land-sculpturing under conditions 

 of aridity we are led to recognize some entirely new phases of geologic 

 operations. The principles deduced are not alone applicable to coun- 

 tries with excessively dry climates, but likewise to all lands of the earth. 



In the moister regions of the globe, or those parts with which the 

 majority of us are most familiar, moving water is so universally 

 regarded as the chief agent of denudation that other erosive means are 

 seldom more than barely considered. In the arid districts there is a 

 reversal of the relative efficiencies of the erosion processes. Water- 

 action is of quite secondary consequence. Wind-scour, or deflation, is 

 not only the most vigorous, but often almost the sole, erosive power. 



The tremendous efficiency of wind as an erosive agent has been 

 lately brought to general notice mainly through the results of Pas- 

 sarge's investigations in the South African deserts. His principal 

 deduction is far-reaching in its scope and significance, and seems des- 

 tined to stand in geology as one of the grand generalizations of the 

 new century. In our own country it opens up vast and fertile fields 

 of geologic inquiry. 



The desert regions of earth have given to modern geography its 

 most suggestive and fundamental concepts. This is a fact that is all 

 but forgotten by most of us who are accustomed daily to apply these 

 basic principles in the more familiar moist tracts in which we live. 

 Yet the definite cycle of evolution which land-forms pass through, the 

 base-level to which all erosion tends, and a general plains-leveling, 

 without regard to sea-level, that goes on in dry countries, are deduc- 

 tions of the desert. 



True desert conditions prevail over a much larger proportion of 

 our earth than most of us appreciate. Southwestern United States, 

 the greater part of central Mexico, western South America, South 

 Africa, northern Africa, southwestern, central and east-central Asia, 

 eastern Europe and central Australia, all present vast areas of territory 

 which have rain-fall insufficient to raise ordinary grain crops without 

 artificial watering. The desert, however, is not the repulsive land that 

 its name whenever mentioned suggests to the layman. Most of it is not 



