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Geology of Mount Shasta

Figure 32

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Figure 32: Samples of pumiceous (left) and lithic (right) tephra from Mount Shasta. The pumiceous tephra was probably produced by the Red Banks eruption about 9,600 years ago. These pieces were collected from the alluvial fan of Whitney Creek on the northern flank of the mountain where they have been rounded by transport in stream or debris flows. The lithic tephra is thought to have been produced by an eruption that fragmented part of the summit dome about 200 years ago. This tephra has probably been reworked by wind and rain since its deposition, and is mixed with a small amount of plant debris. This sample was collected from a deposit near the Old Ski Bowl.


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