42 H. L. FAIRCHILD — ICE EROSION THEORY A FALLACY 



the general assumption from fiords and hanging valleys. The very im- 

 portant work of Russell over a large area in the northern lands, specially 

 on the Malaspina and the Mount Saint Elias group, brings out no facts 

 favoring erosion. 



The most studied glacier in Alaska is the Muir, which furnishes only 

 indisputable evidence of its failure as an erosive agent. The Muir is 

 now uncovering, or receding from, a thick deposit of gravel and forest 

 ground which it had overridden during its latest advance, and did not 

 remove. The fact is recognized by all students of the region, and the 

 abundant literature* makes the extended description here unnecessary. 



Cushing writes as follows : 



"A glacier of great thickness (over 2,000 feet) has advanced over these gravels, 

 and done so for considerable time. . . . The influence of the ice upon it must 

 have been more protective than anything else. . . . These deposits have for 

 their floor an old land surface, with tree stumps still standing in the soil in which 

 they grew, ..." (Page 220.) "At Muir glacier, in just the position where the 

 greatest erosion would naturally be expected, soft gravels have been undisturbed 

 by the ice." (Page 230.) 



In discussing this behavior of Muir glacier, Russell says : 



"That glaciers of great thickness may overrun unconsolidated gravels, without 

 disturbing them, is no longer open to question." (Paper noted above, page 194.) 



He then refers to such deposits beneath the Malaspina glacier, and to 

 uncovered gravels near Mono lake, California. 



More than other writers, Professor Cushing has noted the erosional 

 phenomena of the Muir Glacier region, and his observations are interest- 

 ing and important, and negative in their force. 



"On all the mountain slopes which Muir glacier has overrun, a tendency toward 

 the production of a surface consisting of small, shallow valleys separated by low r 

 ridges is seen, both trending in the direction in which the ice has moved. . . . 

 The production of such surfaces in this region depends on the presence and distri- 

 bution of the fissure planes. Weathering takes place along these planes to varying 

 depths, resulting in the loosening of V-shaped blocks of varying sizes. After such 

 decay has been in progress for a considerable length of time, a glacier riding over 

 the ridge and removing loosened material will tend to leave a surface composed of 

 ridge-like projections with shallow depressions between. 



11 Lakes. — On the tops of the low mountains bordering Muir glacier, over which 



*S. P. Baldwin : " Recent changes in the Muir glacier." Am. Geol., vol. xi, 1893, pp. 366-375. 



H. P. Cushing: "Notes on the Muir glacier region, Alaska, and its geology." Am. Geol., vol. 

 viii, 1891, pp. 207-230. 



H. F. Reid: "Glacier bay and its glaciers." Sixteenth Ann. Rep. U. S. Geol. Survey, pt. i, 1896, 

 pp. 4lo-461. 



I. C Russell : "Origin of the gravel deposits beneath Muir glacier, Alaska." Am. Geol., vol. ix, 

 1892, pp. 19'»-197. 



G. F. Wright : " Ice age in North America," 1902, pp. 36-66. 



