224 



WILLIAM S. COOPER 



The present series of moraines is very recent and owes its dis- 

 tinctness to a recent minor advance. Just before the present 

 series began to come into being, the ice had retreated to a point 

 within at least the outer boundary of the oldest of the now exist- 

 ent moraines. This is proved by the fact that this moraine has 

 been laid down upon a shingle flat which must have been an 

 outwash plain. Shallow drainage channels cut into this flat 



Fig. 4. Muruiiit'8 and shingle flat of Robson Glacier. Rock knob with patch 

 of climax forest at left. The five moraines mav be distinguished: the oldest, 

 with dark forest: the second, very narrow, a dark line of thicket; the third and 

 fourth, apparently without vegetation; the fifth bevond the outlet stream,' the 

 ice resting upon it. The dark portion of the shingle flat, protected by the mo- 

 raines, bears patches of forest and thicket; the light portions have been recently 

 denuded by torrents. At the right, early stages of the Shingle Flat Succession; 

 Berg Lake at extreme right. Photograph bj^ Frank M. Warren. 



are seen to disappear beneath the edge of the oldest moraine. 

 No signs of earher deposits were found, though remnants prob- 

 ably exist at many points along the sides of the caiions. The 

 glacier therefore, not long ago, having retreated to a position 

 somewhere near its present limit, advanced a short distance and 

 deposited a morainic ridge upon the shingle flat. Upon most of 

 the front the ice advanced considerably beyond the rock pro- 

 jection mentioned above, so that its outer limit bulged on each 



