I9IS-] EARTH FROM THE VIEWPOINT OF GEOLOGY. 281 



in the form of great embossments and basins. These surface con- 

 figurations must have conditioned the locaHzation of extrusions and 

 the deployment of the effusive material. If the lavas arose from a 

 general and abundant source of supply which was responsive to 

 general and powerful stresses, vestiges of this vital relation should 

 be found in the volume and deployment of the lava floods. If, on 

 the other hand, the molten material was but a fraction of the en- 

 vironing mass, variously distributed through it, the result should 

 be a multitude of driblets squeezed out here and there in such special 

 situations as the controlling stresses required, or else forced into 

 weak portions of the earth-body where the stresses were less im- 

 perative. Now there is abundant geological evidence that the earth- 

 body has been subjected at repeated intervals to strong compressive 

 stresses by which its outer portion has been folded into mountainous 

 ranges, or pushed up into great plateaus, while masses of continental 

 dimensions have been raised, relatively, to notable heights, and the 

 bottoms of basins and deeps have sunk reciprocally to even greater 

 relative depths. The internal stresses which these deformations 

 imply should have made themselves felt proportionately on any 

 great mass of liquid in the interior — if it were in existence — and 

 extrusions proportionate to the great deformations of the rigid ma- 

 terial should have accompanied such diastrophism. But, while 

 liquid extrusions took place somewhat freely at the times of great 

 diastrophism, it was not, at least in my judgment, at all commen- 

 surate with the deformative stresses implied by the diastrophic re- 

 sults in the solid material. 



Nor was the concentration of the extrusions indicative of origin 

 from a molten interior or from great residual reservoirs of liquid 

 rock. If such ample sources of liquid had existed they might natur- 

 ally have been expected to have given forth, under the great stresses 

 then seeking easement, correspondingly great floods of lava. Yet 

 no single lava flood seems to have attained more than an extremely 

 small fraction of the mass of the earth or of the known solid matter 

 of its region. Even when the sum total of the most massive series 

 of successive floods in a given region are taken together — though the 

 successive issues stretched over a considerable period — they rarely 

 rise above a most insignificant fraction of earth-mass or even of the 



