INTRODUCTION. 
By 8. F. Emmons. 
POSITION. 
Aspen is one of the most picturesquely situated mining towns of the 
Rocky Mountain region. It lies in the valley of the Roaring Fork River, 
at a point where that stream issues from the area of granite and gneiss 
which constitutes the uplift of the Sawatch Mountains into the upturned 
Paleozoic and Mesozoic strata that encircle it. The Roaring Fork heads 
in the Sawatch Mountains, on the west side of the main crest and about 
opposite the Twin Lakes of the Arkansas Valley. Its general course is 
northwest, and below Aspen it flows along the eastern flank of the Elk 
Mountain uplift for about 50 miles to its junction with Grand River at 
Glenwood Springs. The scenery along this stream above Aspen is very 
sharply contrasted with that below, and in both regions is largely dependent 
upon the geological structure. Above is a relatively broad and straight 
valley, lying between rounded and generally rather barren-looking hills 
of granite and gneiss, bare of vegetation and forbidding of aspect. At 
Aspen the character of the scenery changes; the hills are well covered with 
vegetation, and are remarkably steep and rugged in topographical form; 
the valley bottom is now broader and is filled up, to a certain extent, 
with horizontally bedded gravel deposits, which form a nearly level plain, 
admirably adapted for the location of a town. 
As has already been remarked,’ the scenery and topographical forms of 
the Elk Mountain region are characterized by a peculiarly alpine aspect, 
in strong contrast to those of the eastern flanks of the Rocky Mountains. 
This is due in part to the greater rainfall on the western slopes, and in part 
1Geologic Atlas U. S., folio 9, Anthracite-Crested Butte, Colorado, 1894. 
MON XXxXxI IT xvii 
