Reviews 



Geosynclinaux et regions a tr emblements de terre (" Geosynclines and 

 Earthquake Regions"). By F. de Montessus de Ballore. 

 Bulletin de la Societe Beige de Geologic Brussels, 1905. 

 Pp. xviii+ 243-67. 

 This memoire was read before the Societe Beige de Geologie on Decem- 

 ber 20, 1904. The views presented are so suggestive that they are given 

 here at some length, in order that the geologists of this country may 

 promptly consider the theories advanced. M. de Ballore is well known 

 as the compiler of the earthquake catalogue published in Beitrdge zur 

 Geophysik, Vol. IV, and the statistics have been turned to account in the 

 article here mentioned. The author lays stress at the outlet upon the appar- 

 ent influence of relief upon stability in the earth's crust, whether that 

 relief be land or sea bottom. He then adds: 



The seismic description of the globe has afforded two general results of great 

 importance. One of them, the independence of seismic and volcanic phenomena, 

 was already suspected. The other and quite unexpected one was the grouping 

 of the earthquake regions of the earth into two narrow zones lying along two 

 great circles of the globe. This purely geometric relation demanded a geologic 

 interpretation. It was found at once on the maps: These zones embrace the 

 earthquake regions which coincide exactly with the geosynclines of the secondary 

 epoch, as represented by M. Haug in his well-known memoire on the geosynclines 

 and the continental areas. 



Here is a general synthetic law clearly placing seismic phenomena under 

 the direct control of the principal movements of the earth's crust, for it is along 

 these lines that they have attained their greatest amplitude, both positive and 

 negative. Depending entirely upon statistics and observations, and without 

 the introduction of hypotheses, the law may be stated as follows: 



The geosynclines, or the most yielding belts of the earth's crust where the 

 sediments deposited to the greatest thickness have afterward, during the Ter- 

 tiary epoch, been strongly folded and raised for the formation of the principal 

 present chains or geanticlines, alone include, with only two or three doubtful 

 exceptions, all the seismic regions 



Seismic instability cannot be uniform along these belts on account of the non- 

 synchronism of the movements and of the differences of amplitude. They include 

 here and there peneseismic, and sometimes even aseismic, regions, the reason 



for which may be found in the details of geologic history 



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