CHAPTER XXX 

 THE HUMAN OR PRESENT PERIOD 



The end of the glacial period. The close of the glacial period 

 is usually placed at the time when the ice-sheets disappeared from 

 the lowlands in the middle latitudes of Europe and North America. 

 Notwithstanding this usage, the ice-sheets had not then disappeared 

 completely, and have not even now, for about 10% of the recently 

 glaciated area of North America (chiefly in Greenland) is still buried 

 in ice. These relics of the last glacial epoch show that the continent 

 has not yet emerged completely from the glacial period. Indeed it 

 is not absolutely clear that there may not.be another increase of ice 

 before the long series of glacial epochs closes, but the probabilities 

 seem to be against it. 



It is not wholly clear that the deformative period which began 

 in the late Tertiary, and extended through the Pleistocene, is yet 

 completed. We are accustomed to regard it so, and perhaps this 

 position is justified; but the movements of post-glacial times are not 

 to be ignored (p. 661). A recent movement in the region of the 

 Great Plains seems to be suggested by certain physiographic 

 features. Many phenomena suggest that the western side of the 

 Great Plains was lower than now, relatively, until about the close 

 of the glacial period. On the western side of the continent there is 

 much evidence of recent movement, some of which appears to have 

 taken place since the close of the glacial period, as usually defined. 

 Similar phenomena are found in other continents. It is not wholly 

 clear, therefore, whether the present is to be regarded as a part of 

 that period of deformation which had its climax in the Pliocene, or 

 \vlu-ther it is rather the initial stage of a period of quiescence now 

 being entered upon. 



FORMATIONS 



The formations which have been making since the end of the 

 glacial period are similar to those of that period, except that gla- 

 cial drift is now being made in limited areas only. Most marine 



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