526 GEOLOGY. 



The Behavior of the Continental Borders. 



We conceive the continental borders to have been affected in their 

 own special and peculiar way by (1) body-deformations of the globe, 

 (2) movements of the outer shell, and (3) movements of the sedi- 

 ments. With these were combined cooperative actions on the part 

 of the sea and of the land-drainage. 



(1) The effects of body-deformation. — If the body-deformations con- 

 sisted, as we have supposed, of a downward movement of the ocean- 

 basins and a relative upward movement of the land, it was obviously 

 at the borders of the continent that the transition from the one to 

 the other took place, and hence they were the tracts in which warping 

 was specially felt. The basin sectors are thought not only to have sunk 

 relatively more, but to have crowded somewhat upon the land sectors, 

 and hence at their junction the sea-bottom tended to sink, and at the 

 same time to push under the land, while the latter tended to rise rela- 

 tively, and perhaps even to spread above toward the ocean basin. 

 In normal cases, this tended (1) to depress the outer border of the 

 continental shelf, which may be supposed to have been built out upon 

 the border of the sea-basin by progressive sedimentation, and (2) to 

 submerge the stream-channels there, while (3) the region back from 

 the coast was warped upwards, the streams being thereby rejuvenated 

 and the conditions provided for the formation of the rapids of the 

 infra-coastal tracts. 



(2) The movement of the outer shell. — If the view that an outer shell 

 three or four miles thick shears over the inner body of the earth be 

 correct, it will be readily seen that if the shell is thrust landward over 

 the newly deformed surface of the inner body, the continental shelf 

 would probably be pushed up the landward slope and so caused to 

 emerge obliquely from the sea, the extent of the emergence being depend- 

 ent on the extent of the lateral thrust, and the degree of inclination 

 of the shear-plane beneath. The shell must move enough, taking 

 the globe as a whole, to give rise to the mountain folds and the over- 

 thrust faults of the several periods of deformation, and this was con- 

 siderable, even on the most conservative estimate. Just how this motion 

 was distributed over the globe is uncertain; but the more the evidence 

 is studied, the more the conviction grows that the movement was very 

 general, and not necessarily confined to particular basins and con- 



