44 TARR AND MARTIN CHANGES OF LEVEL IN YAKUTAT REGION 



South of Turner glacier, where the uplift was 33 to 47 feet, while dead 

 Mytilus and Balanus are abundant all along the abandoned strand, not 

 an individual of either, nor any of the seaweed (rock weed) so common 

 elsewhere in the fiord were found growing at present sealevel. Here the 

 destruction for nearly 4 miles was absolute, and in the six years since 

 the uplift the common forms of shore life have not yet advanced upon 

 this part of the coast. There are three apparent reasons for the failure 

 of life to advance on this coast from other parts of the fiord : ( 1 ) the ice 

 barrier of Turner and Hubbard glaciers to the north; (2) the sand and 

 gravel-shore barrier to the south ; and ( 3 ) the presence of an outmoving 

 current of water, due to the glacial streams from Hubbard and Turner 

 glaciers, and therefore coming from a region in which these marine forms 

 are absent.* 



One is impressed by such evidence with the important effect of changes 

 of level on life, and of its possible influence on extinction of species and 

 change of environment in regions of unstable coastlines during the geo- 

 logical past. 



Human Evidence of Uplift 



general evidence of recency 



The human evidence of deformation of the shorelines has its value 

 largely in the fact that it checks our conclusions upon two important 

 points: First, that the elevation took place in connection with the 1899 

 earthquake; second, that all the movement was at once (that is, in the 

 same month). The condition of the beaches, benches, and fans suggests 

 that the movement was recent and that it occurred essentially at one 

 time. The uniform perfection of preservation of certain of the marine 

 forms points to the same conclusions. The fact that vegetation seems to 

 have encroached on all parts of all the beaches at once (equally old plants 

 at all levels and all parts of each beach) points to a single period of 

 uplift; and the fact that of these plants none were found that exceeded 

 five years in age is very definite confirmation of the conclusion that the 

 uplift occurred in 1899. 



NEGATIVE EVIDENCE OF THE HARRIMAN EXPEDITION 



It has already been stated that the Harriman expedition, with a corps 

 of trained observers, including Dr G. K. Gilbert, was in the bay about 

 three months before the earthquake. They report no evidence of recent 

 uplift, although they landed on parts of the coast where uplifted shore- 



* We are not certain that they are absent between Turner and Hubbard glaciers, for 

 we did not visit that coast ; but from a distance this coast appeared to be occupied by 

 alluvial fans, on which neither barnacles nor mussels could thrive. 



