SUMMATION AND CONCLUSIONS 211 



On the other hand, the borderlands and Sino-Anstralia have foundered 

 more or less into the oceans. In fact, even the Archeozoic and Protero- 

 zoic synclinoria of the Canadian shield or kratogen have not undergone 

 a second cycle of localized subsidence. However, a region once made 

 positive through orogeny will subsequently be arched from time to 

 time, and the aggregate of these epeirogenic uplifts may attain several 

 thousand feet, as in the Appalachians (2,000) or the Eocky Mountains 

 (7,000), or 10,000 feet as in the normally faulted rising masses of the 

 Andes. We have also seen that out of the Cordilleran geosyncline there 

 arose the Intermontane geanticline, while the sequent geosynclines on 

 either side of it are the folded parts of the former greater trough. 



Diastrophism is mainly due to earth shrinkage. My paleogeographic- 

 studies appear to make it clear that there are at least five sets of inter- 

 actions bringing on the marine floods over the continent and the making- 

 of mountains. Three of these are in consequence of earth shrinkage, and 

 one is due to crustal or isostatic adjustment. All of them are reflected 

 in the marine transgressions and emergences. The sealevel is, in addi- 

 tion, altered by the filling of the seas and oceans with the debris of the 

 lands, by the subtraction of oceanic water and the piling of it upon the 

 lands during glacial times, by the growth of mountains of extrusion, and 

 by the movements within the oceanic basins themselves. It is not easy 

 for stratigraphers to evaluate properly the significance of these oceanic 

 alterations in their relations to continental floodings, and we may 

 eventually come to see that their importance is far greater than is now 

 believed. 



Taking Le Conte's views of 1897 and modernizing them, we hold that 

 of crustal movements there are four categories, as follows : 



(1) The most primitive, extensive, and longest-enduring progressive 

 movements are those of (a) negative or downward direction, resulting in 

 the oceanic depressions with the heavier kinds of rocks; and (&) positive 

 or upward direction, giving rise to the continental platforms of lighter 

 materials. 



(2) The comparatively quick orogenic progressive movements in one 

 general direction due to crustal lateral thrusting. They give rise in the 

 stratosphere (or tectonosphere, Sonder 1922) to the folded mountains 

 (orogeny), and in compensating areas to stretching and rifting (tafro- 

 geny). Earth shrinkage is concentrated in the main uj)on the geosyn- 

 clinal areas, the lines of greatest weakness in the crust. 



(3) The slowly forming epeirogenic or more or less wide and high 

 arching or vertical movements of an oscillating character, now upward 

 and now downward. Epeirogenesis predicates eventual orogenesis. 



