7 8 
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^Trost 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. 41 ). 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. 
iThe 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. 
