RESEARCHES IN ALASKA 



555 



: .■ ■ ■ ■ ■ 



Photo by Lawrence Martii 



thk terminal ice cascade of chenega glacier, icy bay, which is about 550 

 feet high, compared graphically with the washington monument 



At the borders of these older deposits 

 there are usually moraine ridges, beyond 

 which is thick-set, mature forest with 

 trees from 100 to 225 years or more 

 of age. Barry Glacier is bordered by a 

 barren zone with the oldest shrubs only 

 1 1 years old, and there are not two belts, 

 but one, outside which a very perfect 

 push-moraine ridge on each side oi the 

 glacier separates the barren zone from 

 the thick forest. 



I had found, therefore, that the ad- 

 vances were not synchronous, and that in 

 three cases out of the four the glacier 

 had advanced twice, for it is hardly con- 

 ceivable that each glacier stood at the 

 inner moraine while the shrubs grew for 

 50, 66, and 92 years. The data for the 

 last of these two advances may be ar- 

 ranged as follows, suggesting glacial 

 maxima in the years shown in the right- 

 hand column, if we assume that retreat 

 began as soon as the glacial maximum 

 was reached in each case : 



Glacier. 



Age of trees. 



Possible date 

 of advance. 



Serpentine 



Toboggan 



Baktr 



20 years. . . . 

 18 years.. . . 

 1 1 years.. . . 



1882 

 1889 

 1891 

 1898 



There are no known visits of white 

 men by which to check any of these 

 dates, except in the case of the Barry 

 Glacier, which had retreated slightly 

 from the edge of the barren zone when 

 the Harriman expedition visited it in 

 1899. In 1898 some army officers saw it 

 from a distance and the advance had al- 

 ready taken place, but they were not near 

 enough to see whether it was still ad- 

 vancing. 



This group of advances, 11-27 years 

 ago, may possibly be due either to cli- 

 matic variations or to earthquake ava- 

 lanches. If it was the former, we must 

 explain why all these glaciers, which are 

 fed from adjoining snow-fields, did not 

 advance approximately together instead 



