GLACIAL POTHOLE 



19 



Bench Mark 



Glacial 

 Pothole 



Before entering the Museum one notices the "Bench Mark" estab- 

 Hshed by the U. S. Geological Survey in 1911 on which is 

 inscribed the latitude and longitude, 40° 46' 47.17" N., 

 73° 58' 41" W., and height above sea level, 86 feet. 



On the right is a "pothole" from Russell, St. Lawrence Co., N. Y., 

 formed by an eddy in the waters of a stream beneath the 

 melting ice of the glacier that covered Northern New York. 

 The stream carried pebbles that, whirled around by the 

 eddy, cut and ground this hole, which is two feet across and four feet 

 deep. 



On the left is a large slab of fossiliferous limestone from Kelleys 

 Island in Lake Erie near Sandusky, whose surface has been 

 smoothed, grooved and scratched by the stones and sand 

 in the bottom of the vast moving ice sheet or glacier that 

 the northeastern part of North America during the Glacial 

 The front of this continental glacier is now thought by most 

 geologists to have retreated northward across Lake Erie from 30,000 

 to 50,000 years ago. At Kelleys Island the ice was moving from east 

 to west. 



Glacial 

 Grooves 



covered 

 Epoch. 



AT THE ENTRANCE TO THE MUSEUM 



