THE GEOGRAPHIC SOCIETY'S ALASKAN EXPEDITION 



29 



that all forward motion ceased thus ab- 

 ruptly, though this also may have been 

 true, but merely that the rapid movement 

 which broke the surface of the glaciers 

 into impassable condition came to an end 

 .at least as early as the beginning of the 

 summer of 1907, and that the spasmodic 

 advance, from beginning to end, was ac- 

 complished within a period of not over 

 •one year. 



The evidence of this almost incredibly 

 rapid change from stagnation to great 

 .activity, and then back again to stagna- 

 tion, is clear and convincing, though in an 

 article of this length it cannot be dis- 

 cussed with sufficient fullness to marshal 

 all the proof. The proofs of the abrupt 

 advance have already been stated in this 

 paper, as well as much more fully in 

 ■other publications relating to the studies 

 •of earlier years. That the advance so 

 actively in progress in the summer of 

 1906 did not extend into the summer of 

 1907, is suggested by the extent to which 

 ablation has healed the crevassing caused 

 "by the spasmodic advance. The ice sur- 

 faces upon which we could not travel at 

 all in 1906 were again passable in 1909. 



We walked across the lower end of the 

 Variegated glacier, and crossed the Atre- 

 vida glacier to Terrace Point, and al- 

 though we did not go to them, it was evi- 

 dent that both the Haenke glacier and the 

 eastern, or Marvine, lobe of the Malas- 

 pina glacier could be traversed without 

 great difficulty. For ablation to so heal 

 the broken ice surface as to permit travel 

 over it time is required, and it is incon- 

 ceivable that the single season of 1907 

 was sufficient for this extensive ablation. 

 In the period of time required must cer- 

 tainly be included the summer of 1907. 

 Contributory evidence is supplied by 

 Hidden glacier, whose entire advance 

 and ablation to passable condition took 

 place after June, 1906; but travel over 

 this glacier is more difficult than over 

 those glaciers which advanced early in 

 1906, for there has been less time avail- 

 able for the reduction of the roughened 

 surface by ablation. 



Other more definite proof that the ad- 

 -\^ance ceased within a few months after 



our study of 1906 is furnished by each of 

 the glaciers. The front of the advancing 

 portion of Variegated glacier has gone no 

 farther than where it stood when last 

 seen in 1906; Haenke glacier front is not 

 quite so far out now as then ; the east- 

 ern margin of Atrevida glacier advanced 

 a little further, but the extent of breaking 

 out in the alder-covered stagnant bulb 

 is the same as in 1906, even the same 

 rings of broken ice in the alder thicket 

 being present ; and along the eastern mar- 

 gin of Malaspina glacier the forest 

 growth on the ablation moraine of the 

 stagnant ice was not entirely destroyed, 

 although in the summer of 1906 it was 

 disappearing at a rapid rate. 



In a word, although the change in gla- 

 cier condition between September, 1905, 

 and June, 1906, was marvelous in these 

 four glaciers, the changes between Au- 

 gust, 1906, and July, 1909, have been of 

 almost no consequence, excepting only 

 such extensive ablation as to render the 

 glaciers once more passable. It is not 

 to be inferred, however, that ablation has 

 so reduced the irregularities caused by the 

 breaking of the glaciers in their flood 

 stage as to bring about again the undu- 

 lating, easily traversible surfaces of 1905. 

 The condition of the glacier surfaces is 

 far different from that of the period be- 

 fore the advance, and travel over them is 

 as yet by no means easy. The surface 

 rises and falls in a series of great waves 

 and troughs, and crevasses are encoun- 

 tered at frequent intervals. Neverthe- 

 less, the ice surface of these glaciers 

 more closely resembles the condition of 

 1905 than that of 1906. It is evident that 

 they have once more relapsed into the 

 stagnant or semi-stagnant state by which 

 they have been characterized since first 

 discovered and studied. 



The observations of 1906 proved that 

 the advance of the p-laciers under the im- 

 pulse of increased supply furnished by 

 earthquake shaking was rapid, and the 

 observations of 1909 prove that the im- 

 pulse is spasmodic and of brief duration. 

 The entire cycle, from gentlv undulating 

 ice surface, through the broken stage of 

 the glacier flood, and back to the normal 



