VOLUME XXVIII NUMBER i 



THE 



JOURNAL OF GEOLOGY 



JANUARY-FEBRUARY 1920 



DL\STROPHISM AND THE FORMATIVE PROCESSES 



X. THE ORDER OF MAGNITUDE OF THE SHRINKAGE OF THE 

 EARTH DEDUCED FROM MARS, VENUS, AND THE MOON 



T. C. CHAMBERLIN 



The University of Chicago 



PRELIMINARY CONSIDERATIONS 



During the last century it was the prevalent view that the 

 earth was once a white-hot liquid globe. It was a logical inference 

 from this view that the subsequent shrinkage of the earth arose 

 chiefly from a loss of heat and from effects incidental thereto. 

 On critical inquiry, however, it was found that the contraction 

 assignable to lowering of temperature was disappointingly small. 

 On the other hand, it was found as field inquiry was extended that 

 the sum total of surface shortening impHed by foldings, crumplings, 

 overthrusts, and similar evidence was distinctly large. As a 

 result of these divergent disclosures, students of diastrophism came 

 to feel not a little hesitation in following out fully and freely to 

 their logical limits the trend of interpretations suggested by field 

 evidence whenever very great shrinkage was foreshadowed. The 

 restraint thus felt was much like that suffered during the same 

 period from supposed limitation of geologic time, a restraint now 

 happily removed. 



A radically new aspect, however, was given to the whole problem 

 of earth shrinkage when, near the opening of this century, it was 



