94 CARNEGIE INSTITUTION OF WASHINGTON. 



are subject to a minimum degree of destruction. The general tendency 

 is to preserve the evidence of one period by covering it with the deposits 

 of another. Thus long series of deposits are formed which contain a full 

 climatic record, if only it could be read. In most desert regions such 

 records are accessible only in small fragments where their borders 

 have been eroded, or by means of deep borings which of necessity 

 disclose the nature of only a minute portion of a given deposit. In the 

 Death Valley drainage area the deposits are fortunately eroded to 

 an unusual depth in many places, or else have been upturned by recent 

 faulting, and can be studied with great ease and thoroughness. There 

 is, perhaps, no other part of the world where the prospects are so bright 

 for obtaining a complete record of all the climatic changes, both large 

 and small, from the later part of the Tertiary era through the entire 

 glacial period to historic times. 



In addition to the main purpose of framing a climatic scale, the 

 present work in the Death Valley drainage area serves two other 

 purposes. One is to test the old criteria for the determination of past 

 climatic conditions and to devise new criteria. The other is to deter- 

 mine the relation of each new fact to the various hypotheses advanced 

 in explanation of climatic changes. Only a preliminary reconnaissance 

 has in most cases been possible during the present year. One of the 

 most important lines of study, namely, a correlation of the glacial phe- 

 nomena of the Sierras with the various types of evidence in the desert at 

 their base, has not yet been begun. 



The Effect of Climate versus Earth Movements, by Ellsworth Huntington. 



Terraces and other alluvial deposits are of special importance as pos- 

 sible evidences of climatic changes, because no other type of evidence 

 seems to be so widely spread. The great difficulty in interpreting 

 them lies in the fact that similar features have repeatedly been sup- 

 posed to be the result of movements of the earth's crust. The Mohave 

 Desert is a particularly good region in which to study the matter. 

 On the south the desert is bordered by the great San Andreas fault, 

 along which the San Francisco earthquake took place, and on the west 

 by the still greater fault at the eastern base of the Sierra Nevadas. 

 Along both lines extensive movement has taken place in recent times. 

 Hence here, if anywhere, terraces due to earth-movements ought to be 

 well developed. Yet such is not the case. Although most interesting 

 and peculiar features have arisen along the fault zones, terraces are 

 not important except where the climatic conditions are appropriate 

 according to the hypothesis set forth in "Explorations in Turkestan" 

 and ''The Climatic Factor." A phase of this problem has been inves- 

 tigated by Mr. Free, as described below. 



