TITLES AND ABSTRACTS OF PAPI2RS 125 



INVESTIGATIONS INTO THE MAGNITUDE OF THE FORCES WHICH ARE 

 REQUIRED TO INDUCE MOVEMENTS IN VARIOUS ROCKS UNDER THE 

 CONDITIONS WHICH OBTAIN IN THE DEEPER PARTS OF THE EARTH'S 



CRUST 



BY FRANK D. ADAMS AND J. AUSTIN BANCROFT 



(Abstract) 



This somewhat extended investigation has been carried out with a view to 

 obtaining at least an approximate measure of the forces required to induce rock 

 flow under the conditions of differential pressure which obtain at two separate 

 horizons within the earth's crust, and also to ascertain the influence of increas- 

 ing load on such rock movement in the deeper portions of the crust. 



The following rocks were employed : alabaster, Castellino, Italy ; marble, 

 Carrara, Italy ; black Belgian marble ; dolomite, Maryland ; steatite, Virginia ; 

 slate. New Rockland, Quebec ; sandstone, Cleveland, Ohio ; granite, Baveno, 

 Italy; diabase, Sudbury, Ontario. 



In each experiment a standard cylindrical column of rock was inclosed in a 

 tube of nickel steel of standard dimensions and deformed with a very slow, 

 creeping movement, the pressure being exerted through pistons inserted in the 

 ends of the tubes. Two sets of steel tubes having different wall thicknesses 

 were employed, representing different resistances — that is, different loads of 

 overlying rock, equivalent to different depths beneath the earth's surface. 



In this way the "work done" in effecting a certain definite amount of defor- 

 mation was determined in the case of each rock and the relative ease with 

 which the different rocks were deformed was given mathematical expression. 



The results obtained from this investigation throw light on a number of prob- 

 lems presented by the zone of flow^ They show that certain of these problems 

 which have been made the basis of mathematical analysis must be reconsidered, 

 and they provide data for this reconsideration. Among other results, it is 

 shown that in going downward in the earth's crust there is a rapid increase in 

 the rigidity of rock masses, so that a continuously greater force is required to 

 effect their deformation. Movements, therefore, take place much more readily 

 in the upper portion of the zone of flow than in its deeper parts. This fact 

 has an important bearing on the questions of isostasy and orogeuic movements. 



Presented in abstract extemporaneously by the senior autlior. 



Discussion 



I'rof. George H, Ciiadwick asked whether the postglacial uplift of the (ireat 

 Lakes area and Canada InA-olved a deep-seated or a comparatively superficial 

 transfer of matter underground, 



Mr. E. W. Shaw : I'rofessor Adams has attempted to reproduce conditions 

 existing within the earth, but apparently his test specimens were dry and at 

 ordinary temperature. What elfect would the presence of water and higher 

 temperature have on the results? 



I'rofessor Adams' reply to Mr. Shaw : As stated in tlie paper, this investiga- 

 tion deals only with the effects produced by pressure. Our previous work has 

 shown that heat tends to increase the ease with which movement takes place. 



