EARTHQUAKE OF CENTRAL JAPAN, 1891. ßQ]^ 



I. Dislocations. 



Whatever may be the cau«e, whether depression or unequal con- 

 traction of the earth's crust, the formation and structure of mountain- 

 ranges are surely due to the folding, rending, and Assuring of strata. 

 Therefore it is not entirely out of place to insert here some considera- 

 tions on the topic of dislocations, which Professor Suess has ably 

 sketched out in his " Das Antlitz der Erde^ 



" Die sichtbaren Dislocationen in dem Felsgerüste der Erde sind das 

 Ergebniss von Bewegungen, welche aus der Verringerimg* des Volums unseres 

 Planeten hervorgehen,^' A stress originated in this process may be 

 resolved into tangential and radial components. The first is 

 horizontal, folding and shifting the mass; the second is vertical, often 

 causing a large tract of land to be depressed. The tangential com- 

 ponent is more superficial, pressing up the strata into mountains; the 

 radial component acts more profoundly in the interior of the crust, 

 and as a rule volcanic explosi<3ns accompany the dislocations due to 

 it. 



«) We begin with the tangential movements of the lithosphère. 

 The simplest result of a horizontal thrust of any superficial part of the 



* Every theory which lias hitherto been proposed to accoiant for the elevation of moun- 

 tains and the folding of the stratified rocks forming the earth's crust hinges finally on changes 

 of temperature. Thus the tangential force generated in the rigid crust of low temperature 

 by the cooling and shrinking of the earth's nvicleus has been invoked to account for the 

 cruuipling of the crust into mountain-ranges ; the crumpling skin of a dried ajjple being the 

 stock illustration. In this case, the force called in is continuous contraction by loss of heat. 

 The theory which Mellard Read has elaborated is the one dependent upon alteration of 

 temperature in the crust, contraction and expansion both being agents of viplift and lateral 

 pressure. Mellard Read : Origin of Mountain-ranges by Sedimentary Loading and Cumulative 

 Recurrent Expansion. 



