70 GEOLOGY OF ERIE COUNTY 



present Allegheny and Susquehanna rivers. At a later stage of 

 its retreat when its front lay along the present morainal zone at 

 Gowanda, the water was still prevented by the ice from taking 

 its ancient course to the westward and was forced southward 

 over the divide at Machias and Dayton, where are to be seen the 

 great channels which carried the glacial waters southward to the 

 Allegheny. 



Subsequently when the ice had receded from its moraine at 

 Gowanda and had paused once more at the point now marked by 

 the Hamburg moraine the water had found a lower outlet than 

 those at Machias and Dayton. The surface of Erie county slopes 

 to the northward. The glacier was retreating slowly down these 

 slopes. As a consequence there came to be an ever widening 

 notch between the ice front and the uncovered land surface. 

 This gradually widened into a v-shaped trough closely following 

 on the north side the ice front and the southern side the emerg- 

 ing slopes of the land surface. This trough naturally filled with 

 water from the melting glacier and a lake was formed, and into 

 this lake were emptied not only the glacier streams but the 

 drainage of the emerging land. 



Fig. 36. Diagram showing how a lake was formed between the southward- 

 facing glacier and the northward sloping land of Erie county. 



At this stage the entire southeastern half of the county had 

 emerged from its ice covering. Its ancient stream channels 

 were dammed at their lower ends by the ice and were conse- 

 quently filled with water which extended far up their valleys. 

 Each valley formed a separate little lake and each of these lakes 

 drained into the next across the ancient divide at its lowest 

 point. The lakes filling the valleys of Cazenovia creek and 



