GEOLOGICAL CLASSIFICxiTION OF SOILS 59 



ice sheets as they advanced and retreated in response to their 

 environment. The great loads of sediment carried by such 

 streams were either dumped down immediately or carried to 

 other areas for deposition. As long as the water had ready 

 egress it flowed rapidly away to deposit its load as gravelly 



Fig. 13.— Diagram showing how glacial lakes were formed in 'New York 

 State. The lighter shading represents the Ontarian ice lobe; the 

 darker shading indicates the position of the glacial lake waters in 

 the Ontario and Hudson river basins, (After Pairchild.) 



ontwash, river terraces, valley trains and alluvial fans. In 

 many cases, however, the ice front came to a stand where 

 there was no such ready egress and ponding occurred. Often 

 very large lakes were formed which existed for many years. 

 (See Fig. 13.) 



"With the ice melting rapidly on the hill tops these lakes 

 were constantly fed by torrents from above, which were 

 laden with sediment derived not only from under the ice, 



