52 GEOLOGICAL SURVEY OF THE TEKEITOEIES. 



which Clear Creek meanders so beautifully is a modern result, and was 

 worn out of the great detrital mass by water after the close of the true 

 Glacial period. Between the detrital walls in the valley are mounds or 

 ridges of the detritus that has been brought down Clear Creek and 

 lodged near its mouth. The last glacial movement was checked by the 

 remnant of the granite mountain in place at the lower end of the ex- 

 pansion, and as the ice melted the debris was left behind in irregular 

 mounds. Bounded masses of granite of immense size, 100 feet in 

 diameter lie scattered about the mouth of this creek, now going to 

 decay by the process of exfoliation. Between Clear Creek and Lake 

 Creek the slopes are rather smooth, with the granite rocks cropping out 

 here and there, but revealing the effects of abrasion in a marked degree. 

 The surface is covered mostly with a thick deposit of the detrital mat- 

 ter. The placer-mines are very extensive over this area, and the work- 

 ing of them in several localities has exposed a glimpse of the old chan- 

 nels worn deep into the underlying granites and covered with the 

 bowlder-drift. If this thick drift-deposit could be stripped off it would 

 expose a granitic surface Worn down by the movements of vast masses 

 of ice and snow, perhaps grooved and scratched, and the entire area 

 cut through from the mountains on either side with the old creek-chan- 

 nels. We believe, also, that this space between the main river and the 

 base of the range, a width of about six miles, has been worn down from 

 an elevation but little, if any, lower than the front portions of the range 

 that now remain. All the evidence x^oints to the existence here of 

 aqueous forces at a comparatively modern period, of which the present 

 is but an insignificant remnant. 



On both sides of the Arkansas up to its very sources the drift phe- 

 nomena are very remarkable, but much more extensive on the west side, 

 so that there is a slope from the immediate base of the Sawatch range 

 to the river ; but the terraces and bowlder-deposits are well shown on 

 both sides. On the west side the valleys of the mountain-streams are 

 now much used for the pasturage of large herds of stock during the 

 summer-season, the owners driving them south into the San Luis Val- 

 ley during the winter. 



By glancing at the map it will be seen that there are a considerable 

 number of those little branches which run high up near the crest or 

 water-divide of the Sawatch, cutting deep channels or gorges through 

 the mountain-sides, and deep valleys after emerging into the slope, 

 or foot-hills. The slope, or foot-hill, forms a peculiar belt from four to six 

 miles in width between the base of the main range and the river, and 

 in a general way slopes down to the river. The difference in elevation 

 between the bed of the Arkansas and the junction of the slope with the 

 mountain-side would vary somewhat, but must be 1,000 to 1,500 feet. 

 Viewing this slope from the crest of the Park range on the opposite 

 side of the Arkansas we can see clearly the gorges and gorge-like 

 walls of the principal streams at intervals of a few miles apart. Be- 

 tween the main valleys the interval is singularly rolling, consisting of 

 rather deep grassy valleys, extending down from the mountain-sides 

 to the Arkansas, while between them are rounded ridges, or rounded 

 oblong hills, covered over with debris. In many cases the abrupt sides 

 are toward the mountains, and the sides and summits are covered 

 with immense bowlders, as if the masses of ice had lodged on them, 

 and melting had dropped their contents there. This furrowed condi- 

 tion of the surface continues to a greater or less extent up to the sources 

 of the Arkansas in the Tennessee Pass. The great morainal ridges 

 on the south side of Lake Creek are as much as 500 feet to 700 feet high 



