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UNIVERSITY OF COLORADO STUDIES 



but are easily distinguished. A bank of snow and ice forms at the 

 foot of a chff, sometimes extending some distance up the cUff. Rocks 

 broken from the cliff by frost sHde down over the bank all the spring 

 and early summer and accumulate at its foot. Then the snow and ice 

 melt away and leave it standing out from the cHff as a ridge which 

 does not contain the fine glacial mud mentioned elsewhere. It may 



Fig. I. — Showing origin of snow-bank talus ridges, resembling moraines. 



contain mud composed of wind-blown sand, small rock fragments 

 and fragments of vegetation, but that is readily distinguished from 

 glacial mud. 



Conditions Limiting Glacial Formation 



Types of Glaciers. — It is probable that all of our Colorado glaciers, 

 both ancient and existing, are of the alpine type, which may be sub- 

 divided into cliff glaciers (those hanging upon steep chffs) and valley 

 glaciers (those originating on the chffs of cirques and extending down 

 valleys). Except Arapahoe, the existing glaciers of the state are 

 cliff glaciers. 



Glacial Climates. — It is commonly supposed that very severe 

 climate is necessary to produce glaciers, and glacial epochs have been 

 frequently referred to as periods of maximum cold. Glaciers result 

 from the relation of snowfall to temperature, hence either an increase 

 of annual snowfall or a decrease of mean annual temperature, espe- 



