A CERTAIN TYPE OF LAKE FORMATION IN THE 

 CANADIAN ROCKY MOUNTAINS 



In the Rocky Mountains of Canada there are abundant evi- 

 dences of the great Pleistocene ice invasion. During consider- 

 able travel with pack horses through the valleys of the most 

 easterly or summit range the writer had occasion to cross the 

 continental divide by five different passes, from the Simpson Pass 

 on the south to the Athabasca Pass on the north. This crave 

 a familiarity with the range through a degree and one-half of 

 latitude, or from 51 to 52 30' N. The evidence was every- 

 where so constant that a more extended region would undoubt- 

 edly reveal the same indications of a former ice sheet. 



The general topography of the Rockies in this region is 

 exceedingly rough, the mountains being disposed in long ridges, 

 with peaks from 8000 to over 13,000 feet high, with deep, nar- 

 row valleys between. 



In order to understand the special type of lake formation to 

 be discussed, it is necessary first to review briefly the general 

 results of former glacial action in the region. These results are 

 evident in the drift, striations and grooves, the transportation of 

 erratics, and in glacial contours. 



Drift, consisting of unstratified clay deposits containing 

 angular and glacially striated stones, covers the valleys and 

 passes throughout the region examined. It varies in thickness 

 from a thin layer up to observed sections of more than 300 

 feet. It is generally thickest in the valley bottoms and on the 

 lower slopes of the mountains up to an altitude of about 500 feet 

 above the stream beds. Above this level it gradually thins out, 

 leaving the mountains bare at from 1000 to 2500 feet above the 

 valleys. 



Drumlins occur in many valleys, especially in those now 

 occupied by large streams, and in some regions are so abundant 

 as to become the most prominent feature of the landscape. 



247 



