Xkw York State 2 1 



Following this period, the courses of the rivers wore largely 

 determined. The lakes, small and great, were not in existence, 

 but through the basins of what we now know as lakes flowed 

 some of the ancient rivers. 



THE GLACIAL PERIOD 



The great ice age that followed this period wa-, geologically 

 speaking, of recent date compared with the periods going before. 

 The Laurentian ice sheet spread to northern Xew York. The 

 Adirondack Mountains, standing as a barrier, caused the ice to 

 divide, one portion passing southward through the deep Cham- 

 plain valley, extending into the valley of the Hudson, a branch 

 of which passed into the Mohawk valley, -where, not far from 

 Little Falls, it met the ice of the other portion which had passed 

 southwestward through the St. Lawrence valley ; a lobe passed 

 into the Ontario basin; another through the Black River valley. 

 The ice sheet pushed southward until the whole state except the 

 southern border of Long Island was buried under the ice. which 

 reached a depth of several thousand feet. The general direction 

 of the glacier was southward to southwestward, as evidenced by 

 the fact that central Xew Y^ork is strewn with boulders trans- 

 ported from the Adirondacks by the ice. Similar boulders are 

 found as far south as Binghamton and well down the Hudson 

 valley. Evidently there were two advances and retreats of the 

 glaciers in New York State. As indicated, the ice was charged 

 with rocks, boulders, and soil. Thus shod, it became a powerful 

 erosive agent, grinding rocks and soil in its path, leveling hills, 

 and carving out valleys. On the other hand, as the ice melted, 

 deposits were made, oonstituting what is known as " drift," and 

 covering practically all of the state. 



Where the ice first remained stationary it built up what are 

 known as " terminal moraines," a range of low, irregular hills. 

 Thnsr- mark tho southernmost limit of the ice sheet, and may 

 be distinctly seen through the whole length of Long Island, also 

 through the southern portion of Cattaraugus County. Further 

 northward, but not so distinct, moraines may be traced from 

 Herkimer through Oriskauv Falls, Cortland, TTatkins. Bath, 

 Portageville. Dayton, and Jamestown. 



