jj^Y^gj^j GEOLOGY ELK MOUNTAINS. 67 



very extended and grand. To the south we can see the country we 

 have just passed over from the Sawatch range. In the foreground the 

 series of sedimentary beds on both sides of Eock Creek, which have been 

 subverted by the uplift of the Snow Mass group, the great sedimentary 

 covering laid off from the granite as the covering of a bed is drawn over 

 from the pillows. At the southeast the lower beds, or those that run 

 next to the granites, are nearly vertical in position, but the newer or 

 higher ones geologically are tipped far past a vertical. Farther still to 

 the south, across the gorge, is a ridge covered with snow, from the sides 

 of which ocher and maroon strata incline at various angles, on one side 

 about east, and on the other west, while the nucleus is a mass of igneous 

 granite. To the eastward, extending a great distance, the red beds can 

 be seen inclining at various angles for the most part from the central 

 mass, but full of dikes. It would seem that the cones and i^yramids 

 formed remarkable cross-sections, showing fissures of various widths, 

 through which the igneous matter came to the surface. Twenty or thirty 

 of these dikes of all sizes are in sight on the east side of Snow Mass Peak. 

 These dikes present a great variety of forms. Sometimes the igneous ma'- 

 terial has flowed up through vertical fissures, as in the maroon ridge to the 

 southeast. In the same ridge the igneous matter has come to the surface 

 and overflowed, so that the ridge is capped with the granite. To the north- 

 east there is a red ridge, with a wide vertical dike through which the igne- 

 ous matter has come up from the central mass and overflowed, forming a 

 cap to the ridge. At another locality to the northeast we can see dis- 

 tinctly the ocher beds, or the lowest sedimentary group, probably Silurian, 

 resting on the granite, inclining 10<^ to 15°, and on these a great thick- 

 ness of red beds, and on top of the latter masses of irregular thickness 

 varying from 100 to 400 feet of the eru^Jtive granite, and at either end 

 the red beds again, resting upon the eruptive mass. In this case the 

 eruptive material must have been pushed up through a fissure in the 

 lower strata, and toward the summit lifted up the upper red beds, so 

 that it now appears like an interstratified mass. For twenty or thirty 

 miles from Snow Mass Peak to the northward between east and west, 

 the red or maroon beds rise in high, long ridges, with immense valleys 

 and gorges between. To the northwest are portions of the Snow Mass 

 group and Sopris Peak, all, parts of the great central granitic mass or 

 nucleus. Far in the distance, westward, thirty miles or more, is the 

 valley or caiion of the Grand Eiver, with stratified beds of a light red 

 on either side. In the amphitheater on all sides of this granitic nucleus 

 are quite remarkable glaciated rocks, with great numbers of beautiful 

 green lakes, which form the sources of numerous branches of the rivers. 

 These are reservoirs for the reception of the waters of the melted snows 

 which lie in glacier-like masses on the sides of the mountains. The 

 same proofs of the wearing away of these central masses is shown in 

 this range which we have so often observed in the preceding chapters. 

 The crest is a thin, sharp ridge, in many places so narrow that it is with 

 difficulty one can creep along it. It is remarkably zigzag in its strike, 

 enormous amphitheaters having been excavated on both sides, in many 

 instances having broken through the crest, either from one side or the 

 other. 



On the east side of Snow Mass group there is a fine, -large amphithe- 

 ater in which are several small lakes with vast quantities of broken 

 rock, and just above them, on the side of the crest, a vast glacier-like 

 mass of snow and ice, from which, at this season of the year, (August,) 

 water is flowing rapidly. We might suppose that in old glacial times 

 each one of these amphitheaters was the abode of a glacier which each 



