THE GEOGRAPHIC SOCIETY'S ALASKAN EXPEDITION 19 



exhibiting the full efTects of the response 

 in the sudden addition to their snow sup- 

 ply. As the abrupt melting of snow in 

 the headwaters of a river causes a flood 

 which, in time, sweeps to the very river 

 mouth, so in these glaciers the great and 

 unusual addition of snow and ice during 

 the earthquakes has given rise to an ice- 

 flood which has swept down to the glacier 

 ends. On this theory, therefore, the 

 phenomena observed are explained as the 

 result of a glacier flood started by earth- 

 quake impulse. 



The observations of 1905 and 1906 

 were sufficiently extensive to at least lend 

 strong probability to this theory, and it 

 has been quite generally accepted. It 

 was, however, of great importance to ap- 

 ply further test to the theory and to study 

 the later phases of the phenomena at- 

 tending such glacier advance ; and there- 

 fore it was with keen interest that the 

 authors again turned their attention to 

 the Yakutat Bay region in 1909 under the 

 auspices of the National Geographic 

 Society. 



If the earthquake theory were the 

 correct explanation of the remarkable 

 changes observed in 1906, three things 

 were to be expected : In the first place, 

 other glaciers should by that time begin 

 to show the efifects of the glacier flood ; 

 secondly, those glaciers which had al- 

 ready been under the influence of the 

 glacier flood should begin to show signs 

 of its diminution, though just what these 

 signs would be or how rapidly the glacier 

 flood would subside could not be pre- 

 dicted ; thirdly, no such profound, spas- 

 modic changes in the glaciers should be 

 found in regions on either side of Yak- 

 utat Bay outside the area of severe earth- 

 quake shaking. 



A study of these three points was the 

 foremost object of the expedition of 

 1909, and the results of this study were 

 in all cases in support of the theory pre- 

 viously proposed. If further demonstra- 

 tion of the accuracy of this theory were 

 demanded than that previously presented, 

 the results of the expedition of 1909 sup- 

 ply enough to establish the theory on a 

 firm foundation. This additional evi- 



dence will be considered under the three 

 phases mentioned above, beginning with a 

 consideration of the new advance. 



ADVANCE OF GLACIERS BETWEEN 1906 AND 

 1909 



Several of the glaciers of Yakutat Bay 

 have as yet suffered no change as a re- 

 sult of the earthquake shaking, so far as 

 can be seen. This is true, for instance, 

 of the Fourth glacier, which lies just 

 east of the head of Yakutat Bay ; of the 

 tidal Nunatak glacier, that has continued 

 the recession which has been in appar- 

 ently uninterrupted progress since 1891, 

 and whose ice clifif is now a mile and a 

 half or more farther back than in 1899; 

 of the tidal Turner glacier, which appears 

 to be almost as it was in 1890, 1899, 

 1905, and 1906; of the Hayden glacier, 

 the easternmost tributary to Alalaspina 

 glacier, which is in the same state as in 

 1905 and 1906; and of several smaller 

 glaciers which are in the same state as in 

 1905 and 1906. But three large glaciers 

 have come under the influence of the 

 glacier flood since last seen in 1906. 



Of these the largest and least eft'ected is 

 the tidal Hubbard glacier, which seemed, 

 in 1909, to have just begun to come under 

 the influence of the glacier flood. This 

 is an active glacier, and since first ob- 

 served by Russell, in 1890, has been 

 crevassed from side to side and has 

 poured a steady stream of icebergs into 

 the fiord from its 5 miles of ice cliff. But 

 beyond the mountains the extreme east- 

 ern margin, blanketed by a cover of 

 lateral moraine, has been in a semi-stag- 

 nant state, and, where it projected into 

 the sea, rose as a dirt-stained ice cliff 

 from which the discharge of icebergs was 

 infrequent. Back from this ice cliff, on 

 the land, was a moraine-covered ice 

 slope in which little ice showed, and up 

 which it was easy to climb to the glacier 

 surface (see pages 16 and 35). 



HUBBARD GLACIER IS EVIDENTLY ON EVE 

 OF GREAT MOVEMENT 



In 1909, however, this moraine-covered 

 land slope of the glacier margin was 

 being destroyed ; the ice was pushing out 



