THE NATIONAL GEOGRAPHIC MAGAZINE 



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Serpentine, Toboggan, and 

 Baker glaciers, all of which 

 are now retreating. 



Around the termini and 

 lower borders of a number 

 of the Prince William Sound 

 glaciers are conspicuous bar- 

 ren zones, where the glaciers 

 have melted back from their 

 farthest recent advance. There 

 was such a barren zone around 

 Columbia Glacier in 1899 when 

 Gilbert visited it, but before 

 1909 most of this barren zone 

 was overridden by the ad- 

 vancing glacier, and in 1910 it 

 was all covered, as were parts 

 or all of the barren zones bor- 

 dering the College Fiord gla- 

 ciers in 1899 and 1909. In 

 Harriman Fiord these barren 

 zones are still present near 

 most of the glaciers. My first 

 impression was that the ad- 

 vances preceding the retreats 

 that exposed these barren 

 zones were synchronous, and 

 that an examination of the 

 ages of shrubs that had sprung 

 up in the barren zones would 

 reveal the approximate date 

 at which the last advance of 

 these glaciers had taken place. 



Serpentine Glacier was 

 studied first, and in its barren 

 zone the scattered willows, 

 alders, and spruces were none 

 of them more than 27 years 

 old. An earlier moraine out- 

 side this had trees up to 93 

 years of age. Baker Glacier, 

 just south of Serpentine, had 

 a nearly barren inner moraine 

 with shrubs 18 years old, and 

 a more thickly forested outer 

 moraine with spruces up to 

 no years old. Toboggan Gla- 

 cier, near by, has 20-year-old 

 shrubs on the last moraine of 

 its barren zone and conifers 

 of 70 years' growth on an 

 older moraine. 



Many trees were cut down 

 in determining these ages, the 

 oldest ones being cited here. 



