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Sierra Club Bulletin 



Thus, the largest of the Clouds' Rest avalanches, in rushing 

 down their magnificent pathway of nearly a mile in vertical 

 depth, on their arrival at the Tenaya Creek (Fig. 3) dash 

 across its channel and up the opposite bank to a height of more 

 than a hundred feet, pushing all the pebbles and boulders of the 

 stream up with them. Spring freshets bring down a fresh sup- 

 ply of pebbles and boulders from year to year, which the ava- 

 lanches patiently add to their moraine, until in a few thousand 



J 



Fig. 3. 



years these washed pebbles form a considerable proportion of 

 the mass. Trees over a hundred years old occur upon the 

 upper portions of some of these avalanche-beds, showing that 

 no avalanche of sufficient power to disturb them had occurred 

 since they began to grow. The lower portions of these beds are, 

 on the contrary, in a raw formative condition, and about as 

 plantless as the shining boulder-beds in the bottoms of rivers. 



Again, stone avalanches have their share in depositing soil. 

 The observer among beetling Yosemitic cliffs occasionally sees 

 a single boulder eight or ten feet in diameter whizzing down the 

 sky like a comet with a tail of dust two thousand feet long. 

 When these huge soil-grains strike among other boulders at the 

 end of their course, they make a sound deeper and heavier than 

 thunder; the ground trembles, and stone-spray is whirled and 

 spattered like water-spray at the foot of a fall. 



The crushed and pounded soil-beds to which avalanches of 

 this kind give rise seem excellently well adapted to the growth 

 of forest trees, but few of them are sufficiently matured to be 



