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Geology of Mount Shasta

Figure 29

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Figure 29: Pyroclastic flow deposit features. The left photo shows pyroclastic flow deposits from Shastina (lower, gray) and Black Butte (upper, beige) exposed in a railroad cut just north of Black Butte. Leader lines from the "R" point to the thin reddened top of the lower deposit and the thicker reddened top of the overlying one. Note that the lower deposit is crudely layered, which suggests that it was formed as successive flows swept across this area from their source at Shastina, 12 kilometers to the east. The right photo shows a prismatically-jointed dacite block collected from one of the Shastina pyroclastic flow deposits.


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