1 62 ALASKA GLACIERS 



several extensive banks of waterlaid material constitute 

 terraces, both on the mainland and on the shore of Van- 

 couver Island. These banks are flat-topped, and esti- 

 mated to rise from 100 to 200 feet above the water. One 

 of them was seen to overlap hills with distinctly glacial 

 sculpture, and as they are from 50 to 100 miles within 

 the limit of the glaciated district they must have been 

 accumulated after the last ice maximum. 



The glacial deposits we encountered are of trivial mag- 

 nitude collectively, in comparison with the glacial erosion 

 of which we saw evidence, and it was therefore inferred 

 that the principal regions of glacial deposition lay outside 

 the field of our observation. This inference agrees with 

 the conclusion of Dawson that the ice-sheet embraced the 

 entire Alexander Archipelago, together with all other is- 

 lands of the coast except the Queen Charlotte, and that its 

 outer margin was beyond the present line of coasts. 



Associated Sea-Levels. The question of the relations 

 of sea and land at the time of the great Pleistocene glacia- 

 tion is of much interest, and some considerations bearing on 

 the question will be mentioned, although the evidence at 

 present available is either indirect or negative. As gla- 

 ciers are chiefly phenomena of the land, and as glacial 

 erosion in this district has been carried far below the 

 present sea-level, it is natural to assume that the sea- 

 level associated with that erosion was much lower. A 

 little consideration, however, will show that such a con- 

 clusion does not necessarily follow. The deepest known 

 hollow ascribable to ice work is in Chatham Strait, and 

 lies 2,900 feet below sea-level. At that point the total 

 depth of the great glacier was probably 6,000 feet. It is 

 commonly assumed that where a glacier enters a sea not 

 deep enough to float it, a part of the ice, equal in weight to 

 the displaced water, is upheld by the water, and the pres- 

 sure of the glacier on its bed is correspondingly dimin- 



