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Burdell Mountain andesite lava flow

By California Volcano Observatory October 2024 (approx.)
A small outcropping of rough gray boulders sits in the middle of a field of dry, tan-colored grass. A metal clipboard leans on one rock to provide scale, and a low hill with a stand of oak trees is visible in the background.
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Detailed Description

The Burdell Mountain volcanics are flow-banded porphyritic andesite, volcanic breccia, volcanic mudflow deposits, and minor flow-banded dacite which can be found west of the Petaluma Valley. Dated at about 11 million years old, they are related to the Quien Sabe Volcanics to the southeast and were displaced by the Hayward-Calaveras fault system. Photo courtesy of Ross Wagner.

Sources/Usage

Public Domain.

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