246 GEOLOGY OF ASPEN MINING DISTRICT, COLORADO. 
comparatively smooth, showing long, low ridges or drumlinoidal hills, with 
gently curved or straight furrowlike depressions, which run in a general 
east-west direction. Over this surface there is a heavy morainal covering, 
consisting chiefly of granite and quartzite, none of the bowlders being very 
large. In places there are well-marked lines of moraine, with larger 
bowlders, and in these places the drift is often as much as 100 feet thick. 
Pl. XXXIV shows this glaciated topography, with the valley of Hunter 
Creek on the right and the summits of the Sawatch Range in the distance. 
DIRECTION OF ICE MOVEMENT. 
Judging from the transportation of material and from the direction of 
the furrows which the ice has impressed upon the topography, the glacier 
had a general movement toward the west, away from the Sawatch. On Red 
Mountain the drift consists mainly of granite and quartzite, which must 
have been carried in a westerly direction across the intervening Hunter 
Creek Valley. In the Roaring Fork Valley there are large quantities of 
granite in the moraine, and granite bowlders are especially frequent below 
Red Butte on the flanks of Red Mountain. 
DIMENSIONS OF ICE SHEET. 
The ice sheet overrode all the hills and valleys in this district, and its 
movement was apparently not influenced by the topography. The hills 
over which it moved now rise 3,000 feet above the broad Roaring Fork 
Valley, and the transportation of material as illustrated on Red Mountain 
shows that the ice did not move down into the valley, but along the moun- 
tain tops parallel to it. If this valley were as deep at the time when this 
great glacier existed as at present, the thickness of ice must have been at 
least 3,000 feet. This ice sheet, however, disappeared at a comparatively 
ancient period, as is shown by the great effects of subsequent erosion, for 
on Red Mountain and other localities the drift has been completely stripped 
away from the mountain sides, leaving a bare and apparently unglaciated 
surface. 
ROARING FORK GLACIER. 
In the last stages of the Glacial period the ice shrunk to comparatively 
small dimensions, and existed only in local glaciers, which ran in the pres- 
