132 



that the great recession of Muir and adjacent glaciers may 

 be largely due to increased melting and iceberg discharge 

 consequent to the rapid retreat, by which the length of 

 Muir ice cliff exposed to the waves was increased from 

 9,200 feet (2,800 m.) in 1892, to 40,000 feet (12,000 m.) 

 in 1906. Tarr and Martin [76, 77] have concluded that 

 the effect of the earthquakes on the recession may have 

 been somewhat exaggerated, for it is certain that a dimin- 

 ution of snow and ice supply is mainly responsible for the 

 rapid changes. The 8f mile (14 km.) shortening of Muir 

 glacier from 1899 to 191 1 was accompanied by 500 to 

 1,500 feet (150 to 450 m.) of thinning through vertical 

 ablation of the glacier surface, which could not be ascribed 

 to the earthquakes. There is, however, a remarkable 

 coincidence between the date of the earthquake and the 

 beginning of accelerated retreat of the ice tongues of 

 Glacier bay. There is no known change of level of the 

 land to aid in accounting for this. 



The recent great advance of the two glaciers of Rendo 

 inlet in Glacier bay raises the interesting question as tu 

 whether Muir glacier and the other ice tongues of Glacier 

 bay will soon readvance. On one hand the maturity of 

 forest growth between the ancient and the second advances 

 suggests that readvance should not commence for a long 

 time; but, on the other hand, the earthquake stimulation 

 introduces a new factor besides that of climatic oscillation. 

 As this factor is yet little known, prediction is unsafe. 



ANNOTATED GUIDE.— Continued. 



105 m. Entrance to Glacier Bay — Leaving the 



168 km entrance to Glacier bay we continue in a 



southwesterly direction through Cross sound to 



the open Pacific ocean; thence we follow the 



130 m. Pacific Ocean — ccast line in a northwesterly 



208 km. direction. The mountains of the Fairweather 



range are conspicuous a short distance inland, 



the prominent peaks named in order from the 



south being La Perouse (10,756 ft., 3,278 m.), 



Crillon (12,727 ft., 3,879 m.), Lituya (11,745 



ft., 3,579 m.), and Fairweather (15,330 ft., 



4,672 m.). Because of heavy snowfall this 



range is mantled by snowfields and glaciers. 



