42 CRATER LAKE, OREGON 



formed a great landmark of the region. Proceeding eastward 

 from Llao rock, the rim loses somewliat in height, and at the 

 head of Cleetwood cove one sees the remarkable spectacle of a 

 lava stream descending tlie inner slope of the rim. It is the 

 only one that has behaved in this way, and its action throws 

 niucli liglit upon the disappearance of Mount Mazama. 



The Palisades are less than 600 feet in elevation above the 

 lake, and are composed almost wholly of one great flow. The 

 streams of lava extending northeast from this portion of the rim 

 are broad and much younger in appearance than those forming 

 the great cliffs south of the lake, where the flows are thinner and 

 more numerous. 



Round Top is a dome-shaped hill over the eastern end of the 

 Palisades, and is made up chiefly of the lava stream that formed 

 the Palisades, overlain by two sheets of pumice separated b}'- a 

 layer of rhyolite. The upper surface of the Palisade flow, where 

 best exposed upon the lalceward slope of Round Top, bears 

 glacial striae that extend beneath the layers of pumice and rhyo- 

 lite of later eruption from Mount Mazama. It is evident from 

 this relation that Mount Mazama was an active volcano during 

 the glacial period. The occurrence of eruptions from a snow- 

 capped volcano must necessarily produce great floods, and these 

 conditions may account in some measure at least for the detritus- 

 filled valleys of the streams rising on the rim of Crater lake. 



Returning from this glacial digression to the boat trip on the 

 lake, it is observed upon the eastern side of the lake that Red 

 Cloud cliff is rendered beautiful by the pinnacles of reddish tuff 

 near the summit, where it is capped by a great, dark flow^ of 

 rhyolite filling a valley in the older rim and extending far to the 

 northeast. Here the springs begin to gush from the inner slope 

 and cascade their foaming rills to the lake. They recur at Sen- 

 tinel rock, Button cliff, and especially under Eagle crag, as well 

 as further westward. Their sources in many cases can be seen 

 in the banks of snow above, but in others they gush forth as real 

 springs whose water must find its way in from the snow upon 

 the outer slope. 



The boldest portion of the rim, excepting perhaps Llao rock, 

 is Button cliff, whicii is made more impressive by the deep 

 U-shape notches on either side and the Phantom Ship at its 

 foot. The notches mark points where the canyons of Sun and 

 Sand creeks pass through the rim to the cliff overlooking the 

 lake. Tliese canyons, due to erosion on lines of drainage, belong 



