QUATERNARY PERIOD. 545 



Section 2. — Quaternary Period. 



Characteristics. — The chief characteristic of the Quaternary is that 

 it is a period of great and widely-extended oscillations of the earth's 

 crust in high-latitude regions, attended ivith great changes of climate. 

 During this period the class of mammals seem to have culminated. 

 During this period also man seems to have appeared on the scene. We 

 do not call it the age of Man, however, because he had not yet estab- 

 lished his reign. His appearance here is rather in accordance with the 

 law of anticipation. As already stated, the invertebrate fauna was 

 almost identical with that still living, but the mammalian fauna was 

 almost wholly peculiar, differing both from the Tertiary which pre- 

 ceded and from the present which followed it. 



Subdivisions. — The Quaternary period is divided into three epochs, 

 viz.: I. Glacial ; II. Champlain ; III. Terrace. These epochs are 

 characterized by the direction of the crust-movement, and of the change 

 of climate. The Glacial epoch is characterized by an upward move- 

 ment of the crust in high-latitude regions, until the continents in those 

 regions stood 1,000 to 2,000 feet above their present height. Large 

 portions of these regions seem to have been sheeted with ice, and an 

 arctic rigor of climate extended far into now temperate regions. 



The Champlain epoch, on the contrary, is characterized by a down- 

 ward motion of land-surfaces in the same region until the sea stood 

 relatively 500 to 1,000 feet above its present level, covering, of course, 

 much that is now land-surface. It was, therefore, a period of inland 

 ice. Coincident with this sinking was a moderation of climate, and a 

 melting of the ice. It was, therefore, also a period of great lakes and 

 flooded rivers. Over the inland seas and great lakes, masses of ice, 

 loosened from the ice-sheet on their northern borders, floated. It was, 

 therefore, also a period of icebergs. 



The Terrace epoch is characterized by the gradual rising again to 

 the present condition of the continents, and the establishment of the 

 present condition of climate. It is, in fact, a transition to the pres- 

 ent era. 



Although we call these divisions epochs, yet we must not suppose 

 that they are equal in length to the epochs of earlier times. As we 

 approach the present time, and the number and interest of events in- 

 crease, our divisions of time become shorter and shorter. 



It is so difficult to separate these epochs sharply from each other in 

 all countries, and to synchronize them, that it seems best to treat of the 

 whole Quaternary period, taking up the epochs successively — first in 

 Eastern North America, as the type or term of comparison, then of the 

 same on the Pacific coast, and last of the same in Europe. 



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