CHAPTER 11. 



SUEFAOE FEATURES. 



MOUNTAINS. 



Althougli the elevation, above the level of the sea, of the hills of the 

 eastern portion of the district is quite as great as that of any other 

 portion, the more prominently distinct mountain masses within its lim- 

 its are located in the northwestern quarter, and consist of closely ad- 

 jacent and inseparable portions of the Uinta system. The Yampa Pla- 

 teau constitutes the principal one of these mountain masses, the others 

 being appendages or prolongations from it, as itself is an appendage or 

 accessory fold of the great Uinta Uplift, lying upon the southern side of 

 the eastern end of that chain. Section Eidge and Split Mountain are 

 western prolongations or spurs from Yampa Plateau, and Midland 

 Eidge is a long accessory fold and eastern prolongation from the same, 

 at least as a topographical featuce. The latter is not so high as the 

 plateau except at its western end, but yet it forms a very conspicuous 

 topographical feature of the region; its bright red strata making it also 

 • a very conspicuous geological one. Beyond this group of subordinate 

 mountain masses, to the northward and northwestward, lies the main 

 fold of the Uinta system; and stretching to the westward its great chain 

 of peaks is seen, with their patches of perennial snow glittering in the 

 midsummer sunlight. 



Junction and Yampa Mountains are remarkable, isolated mountains, 

 each about 2,000 feet high above the surface of the lowland of the basin 

 out of Which they rise ; but they both belong to the Uinta system and 

 lie upon the vanishing extension of the flexure of the great Uinta Up- 

 lift; which extension I have called the axial flexure. The first-named 

 mountain lies some three or four miles east of the eastern end of 

 the Uinta chain, and the latter, which must not be confounded with 

 Yampa Plateau, lies some 15 or 16 miles still further eastward, in line 

 with the great Uinta Axis. The structure and relations of all these 

 mountains will be discussed in a subsequent chapter. 



Although the elevation of the eastern portion of the district is quite 

 as great as that of the mountain masses of the northwestern portion, 

 the rise to the eastward is so gradual, and the surface comparatively so 

 little broken into separate mountains within the eastern borders of the 

 district, that it is not, strictly speaking, mountainous there. Just be- 

 yond its limits to the eastward there is a broad elevated district called 

 the White Eiver Plateau. This plateau has be3n largely formed as 

 such by a great trap-outflow, the borders of which are now cut by ero- 

 sion into deep gorges and ravines, among which White Eiver and Wil- 

 liams Fork of the Yampa have their rise. 



There are some other mountain masses in the more central portions 

 of the district, left as such by the deepening of the drainage-valleys by 

 erosion, that, although they are really important features, have been 

 designated by distinctive names only so far as it was found necessary 



