40 UNIVERSITY OF COLORADO STUDIES 



where the more rapidly moving ice below pulls away from the 

 more slowly moving ice above. "^ "It is formed near where the 

 upward-sloping neve meets the rock walls enclosing it."^ "It extends 

 along the cirque wall and opens every spring by the motion of the neve 



on its downstream side In the most nearly perfect cirques 



the hergschrund is one single rent .... constitutes the dividing line 

 between the moving neve and the quiescent neve; it is the upper 

 limit of glacial motion. The only factor which determines the loca- 

 tion of the hergsckrund in any valley is the depth of the neve."^ "The 

 hergschrund is formed by the moving of the lower part of the snow- 

 field away from the portion above."'* If any sharp line is to be taken 

 to divide a glacier from neve, this seems to be the only one at all satis- 

 factory. A beautiful example is found on Arapahoe Glacier. 



Stratification. — All glaciers exhibit stratification. Usually clear 

 blue ice alternates with more spongy strata. The strata, as they 

 near the end of the glacier in their downward movement, bend upward 

 toward the surface, thus, as observed at their surface outcrop, dipping 

 toward the head of the glacier.^ On Arapahoe Glacier "dips of thirty 

 or more degrees are common a hundred yards from the edge and the 

 steepness increases as the margin is approached.'"^ The nature of the 

 stratification has been much discussed. It has long been contended 

 that the "blue bands" were quite different in their origin from the 

 strata of deposition, the usual view being that they were due to 

 pressure. Recent investigations do not seem wholly to support that 

 idea. Reid in 1898^ noted the "persistence of the original stratifica- 

 tion occasioned by the snowfall of successive years on the neve''' 

 but this structure was distinguished from "the transverse blue band- 



' Reid, Harky Fielding, "The Mechanics of Glaciers," J own. GeoL, Vol. IV, pp. g2o, 1896. 



' Russell, Isilael C, "Glaciers of Mount Ranier," Eighteenth Ann. Rept. U.S. Geol. Surv., for 1896-97, 

 Part II, p. 382, 1898. 



J Matthes, pRANfOis E., "Glacial Sculpture of the Big Horn Mountains, Wyoming," Twenty-first Ann. 

 Rept. U.S. Geol. Surv., for 1899-1900, Part II, pp. 185, 190, 1900. 



< Chamberlin, Thomas C, and Salisbury, Rolun D., Geology, Vol. I, p. 258, 1905. 



s Reid, Harry Fielding, "The Mechanics of Glaciers," Journ. Geol., Vol IV, pp. 917-23, 1896; "The 

 Flow of Glaciers and Their Stratification," Appalachia, Vol. XI, pp. 1-6, 1905. 



« Fenneman, N. M., "The Arapahoe Glacier in 1902," Journ. Geol., Vol. X, pp. 847-48, 1902. 



' Reid, Harry Fielding, "The Stratification of Glaciers" (abstract). Science, N.S., Vol. VIII, p. 463, 



