155 



ceased to advance in 1910, and the 1910 advance of Nuna- 

 tak glacier had practically ceased when the glacier was 

 visited by N. J. Ogilvie of the Canadian Boundary Survey 

 party of 191 1; by 1912 he found that the tidal ice cliff of 

 this glacier had retreated about \ mile (.4 km.). 



It is believed that the observations of 1909, 1910, and 

 subsequent years furnish what further facts are necessary 

 to demonstrate the hypothesis put forward by Tarr in 

 1906 [72], and that the explanation may now be stated 

 with confidence, as an established hypothesis, — a new 

 cause for glacier advance. The sudden forward rush of a 



Excursion C 8. 







Elevated beach and sea cliff in Russell fiord, hoisted over 7 feet in 1899 earthquake. 



glacier accompanied by pronounced thickening and exten- 

 sive surface breakage may be called a glacier flood, and the 

 resemblance to a river flood is noteworthy. When heavy 

 rainfall, or unusual melting of snow occurs in the headwater 

 region of a river, a wave of rising, rapidly down-moving 

 water is started which may cause a flood all along the 

 stream course. If a portion of the river is ice covered, the 

 rigid ice crust will be shattered and heaved into a maze of 



