428 ELIOT BLACKWELDER 
precipitous and continuous. The lower end of the glacier is smooth 
and dirty with the débris of avalanches from the cliffs above. Doubt- 
less the absence of notable crevasses here is to be ascribed to the fact 
that the ice is closely confined down to its very end, and hence the 
tension which would result from an unrestrained deployment is 
lacking. 
From the Canyon Glacier east to the Alsek River no glaciers of 
considerable size remain. The heads of the gulches have been 
glaciated, as is indicated by the well-developed cirques and the rock- 
bound lakes; but only very small snow-bank ice-fields now remain. 
The Alsek Glacier is the largest of all in the area of our survey. 
It heads on the west slope of Mount Fairweather, and, after receiving 
many icy tributaries from the Boundary Range north of it, eventually 
reaches and constricts the Alsek River at its lowermost canyon. The 
lower part of the glacier is a great, flat ice-field or plateau having a 
breadth of 6-7 miles from northwest to southeast, and somewhat 
more from northeast to southwest. The main body of the glacier 
comes in from the east just behind the Deception Hills. Two broad 
tributary tongues enter southeast of the Green Nunatak,t while a 
third, which is double, comes down from the boundary range some 
distance farther to the north. Each of these tributary glaciers would 
in most regions be considered large by itself. The influence of the 
great lobe from Mount Fairweather seems at present to be slight, as 
is evidenced by the fact that the south side is not bulged northward 
at the junction. Much of the ice is clean and white, but a number of 
medial and lateral trains of dirt blacken it in places. Apparently 
by the slow spreading of the glacier itself, these moraines have widened 
and even coalesced in their lower courses. Different parts of the 
glacier show wide variations in the amount of crevassing which they 
have suffered. In general, the steeper parts of the tributaries are 
much cracked. Of the open plateau-like expanse at the end, the 
northern part is not much crevassed, and its level surface may be 
traversed safely if ordinary care is used. The cleaner part, south of 
the Green Nunatak and Gateway Knob, is a bristling mass of sharp 
seracs with deep crevasses between. It would be very difficult, and 
1 This name is applied in recognition of the fact that the medial moraine which 
originates in this nunatak consists chiefly of green slate fragments. 
