The Natural History of Chautauqua 



built up. Some valleys were deepened, others were more or less com- 

 pletely filled. Some streams were turned completely out of their val- 

 leys, some were only partly interfered with, and many valleys were 

 locally transformed into lakes. Chautauqua Lake was formed in this 

 last-mentioned manner. 



Glacial deposits cover the entire Chautauqua region, and extend 

 along Lake Erie, through northwestern Pennsylvania, and down into 

 Ohio. These deposits were laid down and re-worked during a long 

 series of glacial and interglacial stages. Some of the deposits are much 

 older than others. The younger or later deposits are referred by 

 geologists to the " Wisconsin Drift Sheet." It is this "Wisconsin " 

 drift that is the prevailing surface material, soil and loose rock, 

 around Chautauqua Lake. The Wisconsin drift comprises three kinds 

 of glacial drift, as follows: 



a. Till or ground moraine. This is the drift most abundant in 

 Chautauqua County. All of the bed rock covered by the glacier was 

 first scoured by the grinding ice-front, and then covered with this de- 

 posit as the ice melted. The drift was deposited mainly underneath 

 the ice sheet ; in the places where it is mixed and unassorted it is known 

 as " //// " ; wherever it has been stratified and assorted by water action 

 it is called "ground moraine." 



b. Terminal moraines. These deposits were formed at various 

 points along the melting front of the ice sheet, where the rate of melt- 

 ing was about as rapid as the onward movement of the ice, so that 

 the ice marging remained nearly stationary. Under these conditions 

 the materials carried by the ice accumulated over a long period of time 

 in a small area, and were heaped up in irregular hillocks. The city 

 of Jamestown is built upon a cluster of these morainic hills, which were 

 dumped into the ancient valley at this point, in consequence of the 

 valley's peculiar position in relation to the various glacial sheets. 



c. Outwash. From the margins of the terminal moraines, both dur- 

 ing and after the ice invasion, large quantities of rock and soil were 

 washed out and spread over the adjacent lowlands. This condition is 

 general through the Chautauqua region, and is strikingly shown in the 

 Warren, Pennsylvania, area, just to the south of Chautauqua. 



Chautauqua Lake and Its Basin in Relation to the Ice Age 



The Chautauqua basin appears to have been filled with bodies of 

 ice and water possessing all the powers and motions requisite for lake- 

 making. Under their actions streams were cut together, valleys were 

 broadened, bowl-shaped basins were formed among the hills. Had not 

 the processes been interrupted, either by the failure of the ice supply or 

 by the wearing down of its outlet (which resulted in drainage), it is 

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