940 HISTORICAL GEOLOGY. 



QUATERNARY ERA, OR ERA OF MAN. 



Hitherto, along the ages, to the close of the Tertiary period, the conti- 

 nent of North America had been extending its foundations and dry land 

 southward to the Gulf, southeastward to the Atlantic, and southwestward to 

 the Pacific, chiefly through marine depositions. The scene of prominent 

 action now changes. The Quaternary phenomena are mainly those that 

 pertain to the continental surface ; and this general fact is true for all the 

 continents, north and south. Through the making of the great mountain- 

 ranges in the era just passed, and the raising of them to icy altitudes, and 

 by the growth of the continents to their full limits, the water-power of the 

 world had been vastly increased, and this was the chief working agency. 



Rivers had become of continental extent, and glaciers had gathered about 

 the loftier mountains. These agencies, so eminently characteristic of the 

 new era, were the means of finishing off the earth's physical arrangements. 



The Quaternary era opens with a glacial period. " The existence at this 

 time of an epoch of unusual cold was a natural sequence to the vast amount 

 of elevation and mountain-making that had been going on in the Tertiary 

 over all the continents ; for this upward movement would necessarily have 

 resulted in increasingly cold climates over the earth." (D., 1881.) 



The following are the periods of the Quaternary : — 



3. E.ECENT Period. — A moderate elevation of the land where depressed in 

 the preceding period. Mammals of existing species. 



2. Champlain Period. — Depression of lands that were glaciated in the 

 Glacial period ; amelioration of climates ; final disappearance of the 

 ice ; great river floods and lakes, and fluvial and lacustrine deposits. 

 Mammals of the warm temperate zone over parts of the previously 

 glaciated regions, their species largely extinct. 



1. Glacial Period. — Increased elevation of the land over wide regions in 

 higher latitudes ; climate in these latitudes of low temperature and 

 abundant precipitation, and consequently, the production of glaciers, 

 and a wide-spread glaciation of the frigid lands, with the exclusion of 

 all life except that of icy regions. 



The Glacial and Champlain periods were united by Lyell, in his later 

 works, under the general name of the Pleistocene ; and thus the Quaternary 

 era — or the Post-Tertiary, as he named it — was divided into the Pleisto- 

 cene and Recent periods. The term Pleistocene is used beyond in this 

 sense. 



Lyell used the term Post- Tertiary for the formations subsequent to the Tertiary, and 

 through many editions of his works divided it into Post-Pliocene and Recent. In the first 

 edition of his Principles of Geology, published in 1830— S3, the Tertiary was followed 

 simply by the division Recent ; and the subjects of the Drift and Cave animals were 



