Devils Postpile National Park Geologic Story

DISTRIBUTION OF VOLCANIC ROCKS DEVILS POSTPILE NATIONAL MONUMENT AND VICINITY Geology by DAVID W. CLOW and KENNETH R. COLLUM, 1983 Modified from N. K. HUBER and C. D. RINEHART and R. P. KOEPPEN. Base map by U.S. Geological Survey.

EXPLANATION

• Undifferentiated surface deposits, including: pumice, stream deposits, recent organic soils.
• Basalt of the Red Cones. Unglaciated red cinder Cones and lava flows.
• Basalt of the Devils Postpile. Dark gray, fine-grained basalt flow, with abundant feldspar crystals.
• Andesite of Mammoth Pass. Light gray to dark gray, fine-grained andesite, with minor feldspar and pyroxene crystals.
• Rhyodacite of Rainbow Falls. Light gray, fine-grained rhyodacite, with minor oxyhornblende crystals. Exhibits horizontal to semi-horizontal platy weathering fractures. Some dense, black, columnar-jointed outcrops.
• Tuff of Reds Meadow. Similar to Bishop Tuff. Buff, ash-flow rhyolite exhibiting welding of pumice with abundant quartz, feldspar, and rock fragments.
• Basalt of The Buttresses. Dark gray basalt, with abundant olivine crystals, and minor pyroxene. Crude columnar jointing.
• Contact, as mapped by Clow and Collum (1983).
• Contact, volcanic units as mapped by Huber and Rinehart (1965; 1967).
• - Monument boundary.

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This page was last updated on 9/7/00

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Material in this site is adapted from a pamphlet, Devils Postpile Story, by N. King Huber, USGS, and Wymond W. Eckhardt, NPS. It is published by Sequoia Natural History Association, Sequoia Natural History Association, HCR-89, PO Box 10, Three Rivers, CA 93271-9792, Telephone (559) 565-3759