MARVINB GLACIER 275. 



the ice-front. In many cases the soil had been removed from around the 

 roots, and in consequence the vitalit}^ of the plants had been so sapped 

 that their leaves had assumed the colors of autumn. Of these trees, 

 fallen or otherwise, none were seen which had not completely developed 

 their leaves, which proves conclusively that the forward thrust, along this 

 margin at least, had its beginning after the spring season. Many of the 

 Cottonwood trees growing on the margin of the glacier were at least fifty 

 years old, so that the essentially stagnant condition of the glacier, now 

 abruptly interrupted, must have had a duration of at least half a century. 



Rapid geologic changes. — The sudden transformation to liquid water 

 of this latent supply, locked up in ice and blanketed beneath debris, has 

 opened possibilities for rapid geologic changes succeeding a long period 

 of stagnation and inactivity. This was well illustrated by the changes 

 that occurred in the glacier margin immediately back of a camp site 

 which we occupied on the west side of the Kwik. Early in July a small 

 stream emerged from the broken ice and flowed past our camp, passing 

 through a small lake in which it was building an alluvial fan (plate 33). 

 During our stay at this camp we were every few minutes disturbed by the 

 sound of falling ice-blocks, the crashing of falling trees, and the sliding 

 down of large quantities of morainie soil. The melting ice supplied so 

 much water that streams of liquid mud were constantly descending the 

 ice-face, building up mud-flow fans along the base of the ice into which 

 one dared not step. These deposits advancing into the fringing forest 

 are rapidly destroying it (plate 23). 



On our return a month later this small stream was greatly swollen, the 

 fan was much larger, and the lake was nearly destroyed. In the meantime 

 the detailed form of the glacier was totally altered. Leaving some supplies 

 cached here for three days, on our return we found them almost under- 

 mined by the stream, which in the meantime had more than doubled its 

 volume. 



Since the entire eastern margin of the Malaspina, not only along Kwik 

 valley, but also along the Yakutat Bay front, is in a similar condition, this 

 sudden supply of water, acting on the morainie debris residually accumu- 

 lated through years of slow ablation, is producing important changes over 

 a wide area. It is a marvelous change, and in a single season more work 

 of transportation and deposit has been accomplished than for scores of 

 years immediately preceding. Another season of exposure to sun and 

 rain will have removed most of the accumulated debris and forest from 

 the margin of this advancing and broken glacier, 



