Monday, September 23, 2013

Geo 365: Sept. 23, Day 266: Dacite and Doug Fir

We're looking up at the sky here, not down at the lake... I had a brief moment of bemusement and amusement as I was going through to choose today's photo, and my mind tried to tell me the Douglas fir was growing horizontally from the caldera rim. To be honest, I'm not absolutely certain we're looking at either dacite or Douglas firs, though both are the most likely options. Dacite is intermediate between rhyolite and andesite, and is common on Mt. Mazama. The block to the lower left shows a nice conchoidal fracture. This was a random stop on the roadside, so I'm not precisely certain of the location; the link below is my best guess.

My, I'm doing a lot of guessing today, aren't I?

Photo unmodified. August 18, 2011. FlashEarth location.

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