THE ROCKS OF MOUNT RAINIER 



Glacier, as well as on the surface of the glacier itself, 

 and in the following season bowlders of granite were 

 found to be plentiful in the river bed at the foot of 

 this glacier. This anomaly of granite bowlders com- 

 ing from a volcanic peak was also noted in the canyon 

 of the Nisqually by Emmons. 



In the somewhat more careful study of the Mount 

 Rainier rocks, search was made and the granite was 

 found in place at several points on the northeastern 

 slope. A biotite-hornblende-granite was observed on 

 Carbon River at the mouth of Canada Creek, about 12 

 miles from the summit of Mount Rainier, and at 

 Chenuis Falls, 2 miles up the river, a finer grained 

 holocrystalline rock occurs, apparently an aplitic 

 phase of the granite. In the lower portion of Carbon 

 Glacier, near its eastern edge, a nunatak of granite 

 can be seen, while the same rock occurs farther to the 

 east, beyond the older of the lateral moraines. Higher 

 on the slopes of Rainier a more marked ridge of gran- 

 ite was traced. A knob rises above the eastern moraine 

 of Carbon Glacier at an altitude of between 7,000 and 

 8,000 feet, and the more prominent features to the 

 east in Moraine Park also owe their survival to the 

 greater erosion-resisting power of the granite. 



PETROGRAPHIC DESCRIPTION 



These granites have few features worthy of special 

 mention. Hornblende and biotite are the ferromag- 

 nesian constituents and vary much in relative im- 

 portance. The variations from hornblende-granite to 

 biotite-granite occur in the same knob or ridge, and 

 considering all occurrences the two varieties seem to be 

 of equal development. There is also some variation 

 in the amount of quartz present, and in the relative 

 importance of the orthoclase and plagioclase. All of 

 these characters are also found in the granites of the 

 Northern Cascades. 



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