Geol.— Vol. I.| TURNER— ORIGIN OF YOSEMITE VALLEY. 275 



there are the usual rock-basin and morainal lakes and 

 morainal meadows. No evidence was obtained in my trip 

 to Mt. Whitney of the glaciers having extended in the 

 canyons of Cottonwood and Whitney creeks to a lower 

 altitude than 9,000 feet, but no careful examination was 

 made. In Crabtree and Rock creeks, however, which 

 drain west from the crest of the range, the glaciers probably 

 extended farther down. The reason of this small develop- 

 ment of the glaciers in the Mt. Whitney region, considering 

 the great altitude, is doubtless in part the low latitude and 

 in part the great height (14,000 feet) of the Kaweah Peak 

 range lying to the west, which receives the first and prob- 

 ably the heaviest precipitation from the rain clouds. 



J. The Recent or Post- Glacial Period. 



Since the glaciers have vanished from the range its topog- 

 raphy has been but slightly modified. The glacial lake 

 basins are being filled up by sediments, frost and heat have 

 continued their work of disintegration, and minor earth 

 movements have taken place as noted under "Orogenic 

 Movements in the Pleistocene." Land slides have occa- 

 sionally blocked up the canyons, as at one point near the 

 headwaters of the Kern River, and in Slide Canyon which 

 drains into the canyon of the Tuolumne from the north. 



Perhaps the most striking evidence of heat and frost 

 erosion in recent times is the formation of talus slopes, and 

 the removal of glacial polish from the rocks. The forma- 

 tion of the rich bottom lands along the rivers and in the 

 Great Valley, as well as the most recent of the detrital fans 

 of the arid eastern base of the range, are likewise to be 

 ascribed to this period. 



IV. The Origin of Yosemite Valley. 

 I. General Statement. 



Yosemite Valley is a widened portion of the canyon of 

 the Merced River. The altitude of the floor is about 4,060 

 feet above sea-level near the Sentinel Hotel, and the sur- 

 rounding cliffs rise on an average from 3,000 to 4,000 feet 



