THE STRENGTH OF THE EARTH'S CRUST 



JOSEPH BARRELL 

 New Haven, Connecticut 



PART II. REGIONAL DISTRIBUTION OF ISOSTATIC 

 COMPENSATION 



Introduction and Summary 



Geodetic Measurements of Isostasy by Hayford and Bowie 

 Hayford's Conclusions from Deflections of the Vertical 

 Hayford and Bowie on Variations of Gravity 



Regional versus Local Distribution of Compensation 

 Conclusions on This Topic by Hayford and Bowie . 

 Review and Analysis of the Evidence .... 

 The Test by Adjacent Stations at Different Elevations 

 The Test by Areas of Grouped Residuals 



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INTRODUCTION AND SUMMARY 



The strength of the crust has been tested in the first part of this 

 paper by those geologic changes which alter the surface of the 

 earth, but not the density of its interior. If these changes in load 

 initiate rather than merely coincide with vertical movements which 

 serve to diminish the stress, they are thereby shown to be greater 

 than the earth can permanently endure. If, on the other hand, the 

 constructional forms persist, as in the two great deltas studied, then 

 the movements which may exist in the crust due to those loads 

 must be slower at least than the process of surface construction. 

 Such loads consequently, unless counterbalanced by some factor 

 not apparent, are within the limits of crustal strength. 



But surface changes and the loads implied can be measured only 

 in special cases. The previous attitude of the crust and the degree 

 and direction of strain then existing in it are complicating factors 

 which it is difficult quantitatively to evaluate. For these reasons 

 the evidence yielded by geodetic investigation promises, in the end, 

 more general and more accurate results. 



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