8o 



WILLIAM H. HOBBS 



studied with respect to tectonic structure. Speaking broadly and 

 in the usual terms, this arc consists largely of a series of sediments 

 folded into closed recumbent flexures with axial planes which incline 

 (except where the crown has sunk) toward the interior of the arc, 

 and which are further extensively "over thrust" and "overridden" 



Fig. 4. — Arc of the Carpathians with volcanoes ranged upon the concave margin 

 (after de Martonne). 



Fig. 5. — Sketch map to show the relation of fore-deeps and arcs of volcanoes 

 to Asiatic arcs. 



in the same sense. Such knowledge as we have of the arcs of Asia, 

 now fortunately assembled and analyzed by Suess, indicates that 

 in a very general way close recumbent folding and "overthrusting" 

 is characteristic of them, and that the dip of the axial planes and 

 the "thrusts" takes the same direction toward the interior of the 

 arc. Quite recently a somewhat comprehensive tectonic study 



