38 GEOLOGICAL HISTORY OF LAKE LAHONTAX. 



MOUNTAINS. 



The numerous narrow and rugged mountain ranges of the Lahontan 

 basin, excepting in a few instances where thev are scantily clothed with 

 cedars and pine, are nearly as barren and desolate as the intervening sage- 

 brush valleys. The Sierra Nevada, as is well known, supports varied and 

 beautiful coniferous forests that are valuable for the timber and wood which 

 they supply. The trees are mainly confined to the moderately elevated 

 portions of the range, their upper limit or the "timber line" having an ele- 

 vation of about 10,000 feet. The lower extent of arborescent vegetation, 

 more especially of the pines, is apparently determined by lack of moisture, 

 and along the eastern base of the Sierra Nevada occurs at an elevation of 

 about 5,000 feet. The upj)er limit of timber-growth is invariably occupied 

 by pines, which, owing to the severe winter climate of the elevated regions, 

 are dwarfed and gnarled, and, at their extreme upper limit, extended prone 

 on the mountain side. At widely separated points in the High Sierra, where 

 exposed to the full fury of the winter storms, the branches and trunks of the 

 pines are stripped bare of leaves and bark, and even eroded by the drifting 

 ice-crystals to a considerable depth, thus recording a recent climatic change 

 that has produced more severe storms than were experienced during the 

 earlier history of the trees. King states that this recent climatic oscil- 

 lation began previous to 1870, and was the first of its kind for over 250 

 years.' ^ 



In the northern part of the Lahontan basin the most conspicuous ranges 

 are the Santa Rosa, Jackson, and Pine Forest. The first two of these are 

 scantily clothed with cedars, above which rise the bare and rugged mount- 

 ain crests; the third, on the western border of the nortliern extension of 

 the Black Rock Desert, is covered over a limited area with a forest of yel- 

 low pine, from which the range derives its name. The mountains bordering 

 on the Carson Desert on the east are dark with pinon, and afiPord to the 

 Pahute Indians an abundant harvest of pine-nuts during certain seasons. 

 On the precipitous mountains overshadowing Walker Lake on the west, 

 there is a timber band, composed almost entirely of pinon, commencing 

 about 1,000 or 1,500 feet above the lake, and extending upwards to within 



"U. S. Geological Exploration of the rortieth Parallol, Vol. I, p. 527. 



