50 GLACIAL AND SURFACE GEOLOGY OF THE PACIFIC COAST. 



if to remove every possibility of a glacial theory of its origin, it presents in 

 precisely the direction from which any moving body of ice must have ap- 

 proached, — namely, towards the head of tlie Tenaya Canon, — a series of 

 immense projecting plates, the edges of which are sharply cut and do not 

 exhibit the least indication of rounding by glacial or any other erosive force. 



Below the Bridal Veil Meadow, at the lower end of the Yosemite proper, 

 the whole character of the valley changes; the sides assume the ordinary 

 V-shape due to erosion by water, and the piles of debris at their base become 

 conspicuous. All the characteristic Yosemite features, — the vertical walls, 

 the rectangular projecting cliffs, the 'almost entire absence of talus, — tliese 

 all disappear as soon as we enter the caiion below. 



All along the Sierra Nevada in the vicinity of the head of the Tuolumne 

 River, there is abundant evidence that the glacial masses covering so exten- 

 sive a portion of the western flanks of the range also extended far down on 

 the eastern side. Above the group of volcanoes near Fish Springs in Owen's 

 Valley, the eastern slope of the Sierra has been but ver}' slightly examined 

 by the Geological Survey. The deep caiions down which Big Pine, Bishop's, 

 and Indian creeks descend are, in all probability, glaciated in their upper 

 portions; but there seem to be no morainic accumulations of great size reach- 

 ing to a considerable distance below the summit, as is the case farther north. 

 All along this side, however, from Round Valley north, as for as Big Mead- 

 ows, twenty miles beyond Mono Lake, the moraines left by the glaciers 

 formerly descending the eastern slope are extremely conspicuous.* A very 

 extensive glacier formed on the east side of the liigh group of summits to 

 which Mount Ritter and Mount Maclure belong. This body of ice pushed its 

 moraines at least six miles to the north, towards Mono Lake. At the 

 southern end of this lake is an extensive group of volcanic cones and craters, 

 which rise to the height of from 9,200 to 9,300 feet above the sea, the 

 highest being about 2,750 feet above the level of Mono Lake. These cones, 

 which are chiefly made up of ashes and j^umice, have retained their original 

 shape in almost entire perfection, shoAving that the amount of precipita- 

 tion in the form of rain in this region must be very small, as otherwise they 

 could not foil to have been more or less washed away. Professor Brewer, 

 who ascended the highest of these old volcanoes, noticed several blocks of 

 granite near the sunnnit and within its crater mixed with the ashes. This 



* The position of the most iiupoitant ol' these moraines will be fouiul laiil down on the soutlieast-quarter sheet 

 of the Central California Map of the State Geological Survey. 



