POST-GLACIAL LAKES IN CANADA 



347 



Each roll may be traced eastward to where it pinches out into 

 the hollows between. The trend of these rolls conforms closely 

 with the direction of ice movement as established by glacial striae at 

 various points along the lake shore. Each roll can only represent 

 a point, carved out by the glacier when it was excavating the basin, 

 around which the waters of the lake lapped at some stage in its 

 development. 



Fig. 9. — View of shingle beach, at elevations up to 150 feet above present lake 

 level, Great Slave Lake, N.W.T. (Photo by A. E. Cameron, 1916.) 



Fig. id. — View of shingle beach, at elevations up to 150 feet above present lake 

 level, Great Slave Lake, N.W.T. (Photo by R. T. Hollies, 1920.) 



Elsewhere about the lake shores undoubted lake beaches and 

 wavecut cliffs are observable at various elevations above the 

 present lake level. They are very numerous and excellently well 

 developed, and are noticeable wherever high land exists in the 

 vicinity of the present shore line (Figs. 9 and 10). 



TERMINAL MORAINES 



In the valleys of Hay and Buffalo rivers occur terminal moraines, 

 marking positions of the ice front during stages of halt or of slight 



