1 68 ALASKA GLACIERS 



i ,000 feet above the sea, as indicated by the contours of 

 the Canadian Boundary Commission's map. 



Between Lituya Bay and the mouth of Alsek River 

 are several other morainic ridges, more or less crescentic 

 in form, and so related to modern glaciers as to indicate 

 that they were formed by them at some earlier epoch, when 

 the ice streams were greater than now. In some cases 

 the modern ice seems to extend to the base of the mo- 

 rainic rampart, and in one instance ice projects through a 

 gap in the rampart; but the height of the old moraines 

 forbids the idea that they were adjusted to glacial condi- 

 tions closely resembling the present. From a distant 

 view some were judged to be as high as 1,500 feet, 

 and the modern glaciers seemed merely to touch their 

 bases, instead of pressing against their inner faces. Asso- 

 ciated with them, and extending along the coast beyond 

 them, are a system of terraces, the highest of which was 

 estimated to be 500 feet above tide; and these suggest 

 that the sea surface stood comparatively high when the 

 moraines were built. 



The fact that the old moraines rise far above the modern 

 glaciers but yet inclose areas only a little larger than the 

 modern ice is able to occupy, is notable, and doubtless has 

 an important significance if rightly interpreted. The ex- 

 planation which occurred to me is, that the extent of the 

 old glaciers was restricted by contact with sea water. As 

 already pointed out, a warm ocean, like the Pacific in the 

 Gulf of Alaska, is a most efficient agent for the wasting 

 of glaciers. The high specific heat of water, the freedom 

 of the circulation by which warm water is brought to re- 

 place the water which has parted with its heat, and the 

 great depth of the body of warm water on which this cir- 

 culation can draw, all contribute to this efficiency. It 

 seems to me entirely possible that if the greater glaciers 

 descending from Fairweather Range in earlier times en- 



