34 



THE NATIONAL GEOGRAPHIC MAGAZINE 



Scale: 



ATRIIVIDA, LUCIA, AND MARVIN^; LOBE 01^ MALASPINA GIvAClER 



Atrevida and Malaspina glaciers advanced between 1905 and 1906, while Lucia glacier was 

 advancing in 1909 (see pages 17, 24 and 25) 



condition of the stagnant glacier, is com- 

 passed in a period of but a few years, 

 say from four to six years. Surely the 

 term glacier flood is warranted for such a 

 sudden change in ice condition. 



This is not the place for a discussion 

 of the validity of the earthquake theory 

 for these remarkable changes, but it may, 

 nevertheless, be pointed out here that, 

 while this theory accounts for all the 

 facts, and stands all the tests applied to it, 

 no other explanation that has so far been 

 suggested can be considered even rational 

 enough to be retained as an alternate hy- 

 pothesis. We believe, therefore, that we 

 are warranted in claiming that a new 

 cause for glacier advance has been dis- 

 covered, for the theory of advance under 



earthquake impulse, first put forward hj 

 the senior author as a result of his ob- 

 servations of 1906, has, by the additional 

 evidence discovered in 1909, been put tO' 

 such tests as to completely verify it. 



GLACIERS OE OTHER SECTIONS SHOW NO' 

 EVIDENCE OE SPASMODIC ADVANCE DUE 

 TO 1899 EARTHQUAKES 



There is, however, one further test that 

 we were able to apply as a result of the 

 field work of the 1909 expedition. It has 

 seemed to us reasonable to expect that, 

 since the earthquakes of September,. 

 1899, were centered in and about the 

 Yakutat Bay region, the spasmodic ad- 

 vance of glaciers should be confined to 

 that region, or, at least, should not be 



