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UNIVERSITY OF COLORADO STUDIES 



the existing Arapahoe Glacier,' once extended down the valley for a 

 distance of perhaps over eight miles, with a depth of 600 feet or more 

 in places. 



Middle Boulder Glacier at its greatest extension probably reached 

 a little below Nederland, though the evidence is not as clear below as 

 above. Its last retreat apparently long anteceded the recession of 

 the North Boulder Glacier. I believe that North Boulder Park, 



Fig. 2. — Map showing approximate general distribution of ancient glaciers in 

 Colorado. 



Middle Boulder Park and South Boulder Park are all filled-up beds 

 of ancient glacial lakes, perhaps representing the earlier glacial exten- 

 sion. Just such lakes are now being rapidly filled up and drained all 

 over the glaciated region, where their glacial origin is undoubted. 

 Unlike most of the gulches of this region, Middle Boulder does not 

 now contain lakes and the upper part has never had such extensive 

 lakes as North Boulder, Albion Gulch, the South St. Vrain etc. 



' Fenneman, H, M., "The Arapahoe Glacier in 1902," Journ. Geol., Vol. X, pp. 840-42, 1902. 



