78 ALASKA GLACIERS 



raine surface over which the ice had advanced, and this 

 surface was elaborately fluted in the direction of ice 

 motion, the corrugations having a vertical magnitude 

 of several feet (fig. 40). In one instance it was seen 

 that a large bowlder in the underlying drift had im- 

 pressed its form on the ice, preserving in its lee a train 

 of drift of the same cross-section, which constituted 

 a ridge, and it is probable that the other flutings were 

 of the same character. As these details in the con- 

 figuration of the drift surface would be quickly ob- 

 literated by frost and rain, their exposure must have 

 been very recent. Probably the advance creating the 

 push-moraine and the subsequent melting which laid 

 bare the ice-molded drift had taken place within one 

 or two years. 



On the mainland at the east the same phenomena were 

 observed, with the exception of the fluted drift surfaces. 

 There was an inner push-moraine, chiefly or wholly of 

 drift and running parallel to the ice margin. There was 

 an outer push-moraine, less regular in its distance and 

 associated with disturbance of the forest and the meadow 

 peat (fig. 4I). 1 In the tract between the two many 

 prostrate trunks were seen, showing that in places the 

 front of the forest had been crowded back several hun- 

 dred feet. Many of the trees that were overturned but 

 not overridden, retained their bark, branches, and even 

 minor twigs, but the leaves had fallen. On disturbed 

 forest soil Coville found three young spruces which 

 had grown since the catastrophe. In each case the 

 age, as shown by rings of growth, was seven years. 

 The date of the ice maximum was therefore not later 

 than 1892 and may have been that year. 



1 The view in fig. 41 is toward the northeast along the front of the push- 

 moraine. A little of the steep face of the glacier is seen at the left. At right 

 is a tract of undisturbed bog. 



