418 STEPHEN KR CAPES, 
to the past and present glaciation of the range as observed by the 
several geologists who have worked in this field. Such a summari- 
zation must naturally be incomplete until the range has been fully 
mapped. 
DISTRIBUTION OF EXISTING GLACIERS 
The distribution of existing glaciers in the surveyed areas is 
shown in the accompanying map, Plate I. In many cases the 
upper ends of the glaciers lie in unexplored and unmapped portions 
of the mountains and in these places the probable headward exten- 
sions of the glaciers are indicated by a different pattern. The shapes 
of the unmapped portions will be modified when more exact informa- 
tion is obtainable, but their general position is believed to be 
approximately as indicated. 
As is to be expected, the glaciers reach the greatest size and are 
most closely spaced in the higher portions of the range, and are 
smaller, or are wanting altogether in the regions of lower relief. 
They are all, however, distinctly of the valley-glacier type, and 
differ in this respect from the glaciers of lower Kenai Peninsula, 
the Wrangell Mountains, and the coastal range west of Mount 
St. Elias, which originate in the ice caps and spread from these down 
the valleys. No extensive ice caps exist in the Alaska Range and 
each glacier is fed from ice which accumulates in its own basin. 
By far the largest glaciers of the range are those of the group 
which drains from the northwest into the Susitna basin. These 
head on the slopes of the highest mountains of North America, 
and by their presence so obstruct the approaches to the crest of the 
range that an area of several thousand square miles exists which 
has never been penetrated by man. ‘This group doubtless includes 
large ice tongues which lie in the unsurveyed area east of Mount 
McKinley, and are, therefore, not shown on Plate I. 
The next important group of glaciers is that which occupies the 
range for about 50 miles west of Delta River, and which includes 
many large and vigorous ice streams which do not, however, equal 
in length or area those in the vicinity of Mounts McKinley and 
Foraker. The third group lies east of Delta River and the glaciers 
become smaller and disappear as Mentasta Pass is approached. 
