243 W. H. HOBBS THE ASIATIC ARCS 



several festoons of arcs — their order of succession in time — and so to 

 determine whether the deforming unbalanced stresses have come from 

 the front or the rear. These festoons of arcs bear such close relations 

 to each other as parts within a system that what has been true of one 

 has in a general way been true of the others, as regards the method of 

 their formation. In other words, we are here dealing with the large 

 jDroblem of the deformation of the continent of Asia under the influence 

 of a system of crustal stresses which have acted over a long period of 

 time and have involved vast areas. 



As a part of this system of arcs, the festoons of islands which parallel 

 the coast are from the relation of their design to that of the ranges upon 

 the continent to be included in the system. The striking difference 

 between the several arcuate series within the system, both as to the ages of 

 the strata involved, the topographic development, the erosional stage, et- 

 cetera, indicates that they have been formed at different times : and since 

 these differences are in a noteworthy degree graded from the interior 

 of the continent toward its margins, they may be assumed to have been 

 formed in succession. The question is whether the interior or the ex- 

 terior arcuate series is the initial one in the succession, and this will 

 (jbviously depend on whether the surface shell of the lithosphere has 

 migrated after the fashion of a glacier in the direction of the surround- 

 ing seas or whether a thrust coming from the seas and directed against 

 the borders of the continent has in successive stages raised a ruffle along* 

 its margin. 



The maps and accompanying sections of figure 1 represent an attempt 

 to set forth these contrasted views with their necessary corollaries, the 

 first (map .and section A) setting forth the generally accepted view of 

 Suess that the thrust has come from the back of the arc, the second (map 

 and section B) the view of the author that this thrust has come from the 

 front. Mountain ranges in process of erection are well known to be zones 

 of seismicity and to be further accompanied by active volcanoes, and these 

 elements have been introduced into the maps. Moreover, inasmuch as 

 erosion is always in sensitive adjustment to uplift, the degree of denuda- 

 tion which should under each of the views be expected in each series of 

 arcs is displayed in the sections. 



Especially to be noted is the condition of marked compression from 

 opposite sides of the arcs within the southeastern extension of the conti- 

 nent in the direction of Australia. In case the outer skin of the continent 

 of Asia is conceived to have migrated centrifugally, as implied by Suess, 

 the position of the ancient coign of Australia should have the effect of 

 broadening the arcs in proportion as they approach this '^'obstruction." 



