350 GLACIAL GEAVELS OF MA1:NE. 



The valleys tributary to the South Branch of the Roaring Fork were 

 occupied by glaciers to a point not far below Aspen. They left moderate- 

 sized moraines and a sheet of glacial gravel that extends for 30 or more 

 miles down the valley. In the valley of Hunters Creek, east of Aspen, a 

 line of perched bowlders marks the upper limit of the ice. 



KOCK CREEK. 



This stream flows for a few miles west, and then north, and drains the 

 western slopes of the Elk Mountains. Grlaciers extended 12 miles down 

 the valley and have left numerous rather small moraines. The amount of 

 glacial gravel in the valley is less than in most valleys of the westei'n slope 

 having so large a drainage surface. 



When one follows the Roaring Fork down to its junction with the 

 Eagle River to form the Grand River, and thence down to the Colorado, he 

 will appreciate what a tremendous weapon the glaciers furnished the present 

 rivers. The jjlains of rolled gravel and cobbles left by the glaciers have 

 helped protect the higher slopes of the mountains from erosion, but the 

 streams have rolled them down to the Gulf of California with fatal effect 

 on the plains and plateaus. In time of high water the ceaseless rattle and 

 roar of those stones as the Grand River surges them on is one of the most 

 astonishing phenomena of the mountain slopes. If the ear be held- near 

 the water or against a boat, one hears a roar as of distant thunder mingled 

 with the sharper click of near-by stones. After that the profound canyons 

 of the plateau region are no mystery. 



ESTES PARK. 



Several glaciers 5 to 10 miles long flowed down into Estes Park. 

 They left very large lateral moraines near where they enter the park, and 

 smaller terminal moraines at about 6,100 feet elevation. The retreat of 

 the ice is marked by a series of terminal moraines, which are found at 

 intervals all the way up to the ultimate basins in which the glaciers origi- 

 nated. Nowhere have I seen such great masses of bowlders showing few 

 or no signs of glaciation and without admixture of fine material, as some 

 of these retreated moraines exhibit. They are locally known as bowlder 

 fields, and are often almost impassable even to men on foot, owing to the 

 large size of the bowlders. They are mostly of granite and are more 



