The top of Chinidere is about...

The top of Chinidere is about...

The top of Chinidere is about a quarter mile above the PCT. Amidst the shale rubble, several windbreak platforms have been created where a dry camp is possible. Here the dogs look down on one hoping for some lunch.
on May 29, 2005 10:14 pm
Image ID: 107315


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dlcole01 - Jun 2, 2005 5:38 pm - Hasn't voted

Rock type

The photo caption mentions shale rock. Shale is a sedimentary rock type. The rock on Chinidere Mountain, however, is volcanic, specifically "platy" andesite, similar to the basalt so ubiquitous in the Columbia River Gorge, but containing a higher percentage of silica than basalt, lending a lighter color to the rock, in a fresh hand specimen.

Don Nelsen

Don Nelsen - Jun 16, 2005 12:40 pm - Hasn't voted

Re: Rock type

Thanks for correcting and clarifying, dlcole.

I've noticed outcrops of even more "platier" rocks at or near the summits of Larch, Thielsen, and others. Is it the silica content of the andesite that determines the degree of this "shale-like" form? (I've heard this called "shell rock" too - probably a better term than "shale like"?


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