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Outcrop of Bishop Tuff from the Long Valley Caldera in California

By California Volcano Observatory
A stark white wall of pitted and furrowed pumice and volcanic ash rises 3-4 meters above the heads of a large group of brightly-bedecked scientists. Thin layers mark the concave lower half of the wall, with the upper overhang holding fewer layers but more football-sized pumice stones.
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Detailed Description

USGS geoscientists examine air fall tephra and pyroclastic flow deposits at the base of the Bishop Tuff, in a quarry near Bishop, CA. This pumice-rich tuff was laid down by the caldera-forming eruption of the Long Valley Caldera around 760,000 years ago.

Sources/Usage

Public Domain.

USGS photo by Jessica L. Ball