64 TARR AND MARTIN CHANGES OF LEVEL IN YAKUTAT REGION 



gather ; but of one thing we are certain : In spite of the parallelism of the 

 fault lines to several reaches of the fiord, and in spite of their possible 

 importance in determining the main lineaments of the valleys, the present 

 depth and form of the fiords are assignable not to faulting but to glacial 

 erosion. The evidence of this is clear and convincing, but the statement 

 of it can not be made in this paper.* 



Comparison with Other historic Uplifts 



While there are many evidences of changes in level during recent geo- 

 logical time, in widely separated localities, some of a slow secular nature 

 still in progress and involving extensive areas, some evidently abrupt and 

 involving smaller areas, the great majority of these give us no clue either 

 to the time or nature of occurrence or to the amount of uplift at a given 

 period. 



Some instances are fairly definite in these respects, and some locate 

 the period of uplift and determine its amount with exactness. A prelim- 

 inary examination of the literature fails to find a single instance in which 

 an uplift approximating in amount that of the Yakutat Bay region, in 

 its maximum, is described as having occurred at a single period of dis- 

 turbance. Compared with the historic changes of level associated with 

 definite earthquakes, the Yakutat Bay deformation therefore stands con- 

 spicuous. It is apparently the greatest historical change of level (47 feet 

 4 inches at the maximum) ; it combines the various classes of evidence — 

 beaches, benches, sea caves, marine animals, human testimony, as in 

 South America (1822, 1835, 1839) ; new reefs, accompanying faulting, 

 as in New Zealand (1855) ; combination of elevation and depression, as 

 in India (1811) ; and it adds the new types of evidence of dissected 

 alluvial fans and uplifted till shorelines, besides furnishing the most 

 complete interrelated evidence of all sorts in practical agreement. 



* See Tarr and Martin : Bull. Amer. Geog. Soc, vol. xxxviii, 100(3, pp. 145-167. 



