THE GEOGRAPHIC SOCIETY'S ALASKAN EXPEDITION 17 



REMARKABLE CHANGES IN THE ALTRE- 

 VIDA GLACIER 



In June, 1906, the Atrevida glacier was 

 marvelously transformed. Its margin 

 was no longer moderately sloping and 

 moraine-covered, but in its place rose a 

 jagged ice cliff, advancing into the forest, 

 and pouring into it a stream of boulders 

 and other morainic debris that was con- 

 stantly sliding down the newly formed 

 ice cliff. The ice was in motion before 

 our very eyes, and the cracking of the 

 glacier, the tumbling of boulders, and the 

 dislodging of huge ice blocks was heard 

 on ev^ery hand. Viewed from a neigh- 

 boring mountain top it was seen that the 

 entire surface of the Atrevida glacier, 

 from its valley head far out into its 

 expanded, alder-covered piedmont bulb, 

 was a mass of yawning crevasses. Travel 

 over this tumultuous sea of broken ice 

 was utterly impossible, and even the as- 

 cent of the margin was possible only by 

 cutting ice steps all the way (see p. 39). 



In a period of nine months a stagnant, 

 or nearly stagnant, moraine-covered gla- 

 cier had advanced, thickened, and become 

 broken into an impassable condition, but 

 neighboring glaciers showed no change 

 from their condition of the previous year. 

 Eor instance, the Lucia glacier, whose 

 piedmont bulb joins that of the Atrevida 

 on the west, and the Hayden glacier, 

 further west, were unchanged. 



West of the Hayden glacier the next 

 large glacier is the Alarvine, which de- 

 scends from the mountains to form the 

 eastern lobe of the great piedmont Malas- 

 pina glacier. This had been transformed 

 as the Variegated, Haenke, and. Atrevida 

 bad been. Where Russell easily crossed 

 it in 1890. near its emergence from the 

 mountain valley, the Marvine was now 

 an impassable sea of seracs, and the east- 

 ern portion of the Malaspina. as far 

 as Point Manby, at the western entrance 

 to Yakutat Bay. was so broken that 

 travel over its surface was no longer 

 possible : yet it was over this portion of 

 the Malaspina glacier that Russell trav- 

 eled in 1890 and the Duke of the Abruzzi 

 and Mr Bryant in 1897, The junior 



author saw the Malaspina and terminus of 

 the Marvine in September, 1905, when it 

 seemed exactly as in 1890. In 1906 the 

 whole eastern margin of the Malaspina 

 was observed by the senior author as a 

 broken, jagged ice cliff, which was ad- 

 vancing in August. 1906. and destroying 

 the forest that grew in the ablation 

 moraine that had accumulated on this 

 stagnant portion of the glacier. 



EXPLANATION OF THE ADVANCE 



In seeking an explanation for these 

 phenomena there was no assistance to be 

 gained from previous records of glacial 

 changes, for such abrupt transformation 

 of glaciers had never before been wit- 

 nessed. Some unusual cause must have 

 been in operation to have transformed 

 stagnant ice into the broken, crevassed 

 condition of rapidly moving glaciers, and 

 to have caused a sudden forward move- 

 ment and thickening of the lower por- 

 tions of the glacier. Such an unusual 

 cause at once suggested itself, for in 

 September, 1899, the Yakutat Bay region 

 was the center of a series of earthquake 

 disturbances of great severity, and to the 

 Study of the eft'ects of these earthquakes 

 we had in 1905 given much attention, 

 finding clear evidence of an uplift of the 

 coast line (in one place to an elevation 

 of 47 feet), of depression, of several 

 fault lines, and of numerous avalanches. 



As a result of a consideration of the 

 phenomena observed in 1906 and of their 

 possible explanation the senior author 

 put forward the following theory as the 

 only one that could adequately account 

 for the facts, and against which there 

 were no fatal objections: 



In September, 1899, the severe shaking 

 of the mountains during the earthquakes 

 caused extensive avalanches of snow, ice, 

 and rock from the lofty mountains into 

 the reservoir of the glaciers of the Yaku- 

 tat Bay region. This added so much to 

 their supply that in time a response must 

 necessarily be felt in the glaciers them- 

 selves. In the short Galiano glacier, and 

 perhaps in others where not observed, 

 the response occurred before 1905, and 

 in i9or) the four glaciers mentioned were 



