38 GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. 



CHAPTER III. 

 VICTORIA GLACIER (Continued). 



i. GLACIAL STRUCTURE. 



a. Stratification. In this chapter there is set off for description a number of 

 features, especially well shown upon the Victoria and its tributary the Lefroy, 

 but which were more or less well represented upon the other glaciers also and are 

 characteristic of glaciers in general. Among the first of these is the stratification 

 the origin of which in the neVe" has been given on page 22. It is conceivable that a 

 stratification in the basal layers might arise exceptionally through the operation 

 of differential stresses in the body of an unstratified glacier. As pointed out by 

 Chamberlin in the case of the massive Greenland glaciers shearing-planes may thus 

 arise leading to a concentration of debris. The lower stratum over which the 

 shearing takes place may be protected from the shearing thrust, may be more 

 heavily charged with debris, or may be more rigid because of its temperature 

 and water content. 1 In the case of the Canadian glaciers studied it seems 

 probable that the strata are depositional, in very large part, at least. Conditions 

 most favorable for the formation of shearing-planes would seem to be found in the 

 case of the Illecillewaet Glacier, owing to the body of ice and its rapid descent 

 from its reservoir. The depositional stratification is almost completely obliterated 

 by the ice cascade and none other has arisen to take its place. 



The stratification of the Victoria continues throughout the glacier's extent, 

 and is seen at the oblique front, in the drainage tunnels and channels, in the 

 moulins, and upon the walls of the crevasses. The line of demarcation between 

 adjacent strata is usually only a soiled streak, but sometimes there is sand, gravel, 

 and an occasional cobble-stone. The strata vary in thickness from 1 2 inches to 

 10 or 12 feet, as seen upon the Lefroy. This thickness would indicate that 9 to no 

 feet of loose snow had taken part in their formation. The average thickness of 

 the Victoria strata is not too great to suppose that they may represent the 

 accumulated and compacted snow fall of the year. Those of unusual thickness 

 are to be ascribed to avalanches. About the mouth of the abandoned drainage tun- 

 nel in 1904 the stratification of the ice was well displayed (plate vm, figure 4, and 

 plate xii, figure 3) as previously referred to. Three strata here averaged 2 6 inches, 

 the full thickness of the lower one not being seen. The uppermost layer was 

 wedge-shaped and thickened from 13 inches to 81 inches. The strata all dipped 

 back into the body of the glacier at an average angle of 26, as measured upon the 

 tunnel walls, but this was less than the actual angle when measured at right 

 angles to the strike of the layers. The irregularities shown in the strata here, 

 as well as in the oblique ice face, are probably due to the partial nourishment of 

 the glacier by means of avalanches of snow and ice. Upon the regenerated Lefroy 

 Glacier the strata are massive, 6 to 12 feet in thickness, having been produced 

 entirely from the avalanches from Mt. Lefroy. These strata all dip towards the 



' See Geology, vol. I, Chamberlin and Salisbury, p. 303. 



