A TYPE OF LAKE FORMA TION IN CANADA 



257 



A study of many cases showed that a certain ratio between 

 the confluent valleys is necessary to the existence of this kind 

 of lake basin. If the confluent valleys are nearly equal in size, 

 thus showing that the glaciers formerly occupying them were 

 probably of the same dimensions, the drift ridge projects as a 

 long tongue between the two valleys and no basin is formed. 

 If the ratio between the confluent valleys is about three to one 

 or more, the drift ridge is thrown across the mouth of the lesser 



Fig. 5. — Lake Louise from the upper end showing the dam. 



valley and a lake basin is formed. If, however, the ratio is 

 exceedingly great, the lake basin will either be small, or totally 

 lacking, and will be farther within the lesser valley, as though 

 the lesser glacier had been set back by the great volume of the 

 main ice current. 



Many lake basins of this type have been entirely filled in by 

 deposits of glacial streams and the growth of sphagnum mosses 

 or forests which have made peat swamps or flat meadows where 

 a lake basin formerly was. 



