32 THE ICE AGE IN NORTH AMERICA. 



century, the Malaspina Glacier, and others near its south- 

 eastern border, had advanced so as to completely fill Disen- 

 chantment Bay and transform Russell Fiord into a long nar- 

 row lake, dammed up by the ice at the mouth of the bay. 

 According to Tarr,* the evidences of this recent advance are 

 abundant in the moraines that were pushed up on the moun- 

 tain slopes east of Yakutat Bay. But, for some time previous 

 to 1905, a recession had been in progress along the front of 

 all the separate glaciers into which the original confluent 

 glacier had been resolved by the general retreat. Thus he 

 writes : 



There is a remarkable change in progress in at least 

 four of the many valley glaciers of the Yakutat Bay region — 

 the Variegated, Haenke, Atrevida, and Marvine. This change 

 is of the nature of a paroxysmal thrust, as a result of 

 which the ice is badly broken, as if a push from behind had 

 been applied with such vigor as to break the rigid resisting 

 ice mass in front. In each case the effect of this thrust is 

 felt from far up the mountain valley well down toward the 

 terminus of the glacier, and in the Haenke and Marvine 

 glaciers to their very end. 



In Variegated and Atrevida glaciers the ice has been 

 broken for a distance of five to seven miles: in Marvine 

 glacier the breaking extends fully fifteen miles. The crevassing 

 in all cases extends completely across the valley portion of 

 the glacier and down into the stagnant, or nearly stagnant, 

 moraine-covered margin. In all cases, too, the thrust is 

 accompanied by a forward movement of the margin; and in 

 at least three cases — the Variegated, Haenke, and Atrevida — 

 there has been a distinct thickening of the ice as a result of 

 the forward thrust. . . . Such a remarkable change 

 in the condition of the glaciers as to transform long-stag- 

 nant, unbroken, moraine-covered valley glaciers into a laby- 

 rinth of crevasses in the short interval of ten months — a 

 phenomenon, so far as known, not elsewhere recorded — calls 

 for a special explanation. 



* a United States Geological Survey, Professional Paper" 64, pp. 91-106. 



