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MARGARET BRADLEY FULLER 



feet above the stream level at the base of steep granite walls on 

 the north side of the valley. 



3. Potholes. — Nearly every exposure of granite in the Estes 

 Valley is marked by several well-defined potholes which vary in 

 size from some 3 or 4 inches in diameter and i or 2 inches deep to 

 others 2 feet deep and 4 feet across (Fig. 5). 



Most of them are nearly circular with the margin broken down 

 on one side. The margins of these potholes have been etched by 

 weathering so that large angular feldspar crystals protrude into 



Fig. 5. — Glacial potholes cut in granite along the Estes Vallej' 



the cavity like small teeth. Within the holes the surface is 

 smoother, and in some grooved so deeply that a secondary pothole 

 has been cut within the original one. 



These potholes are found at all elevations from the summit of 

 Prospect Mountain, 8,896 feet, and the Needles, 10,075 ^^^^j ^o the 

 level of 7,500 feet on the floor of Estes Valley. They also appear 

 in Fish Creek Valley up to the top of Lily Mountain, 9,793 feet. 

 They are believed to mark the margin of early glaciers which filled 

 the Estes Valley where whirlpools following the drainage retreated 

 into the valley with the floods from the waning ice. From Drake 

 to Mont Rose there are a few poorly preserved potholes in the schist. 

 It appears that the schist and pegmatite are not massive enough to 



