Devils Postpile National Park
Geologic Story
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Curved columns. Photo by Wymond W. Eckhardt, NPS.
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Most of the columns in the Devils Postpile diverge from the vertical as
though tilted and some are even curved as if they had been bent. Under
ideal conditions, the long dimensions of basalt columns develop at right
angles to the cooling surfaces. If a lava flow is homogeneous in chemical
composition, of uniform thickness, and has level top and bottom cooling
surfaces, then, theoretically, the flow cools uniformly into vertical columns.
All of these factors were not fulfilled in the Devils Postpile flow, however,
causing irregularities in cooling and consequently producing curved posts
with various number of sides.
The exceptional aspect of the Devils Postpile is
not that some columns are curved, but that in places
the lava was homogeneous enough and had a cooling rate uniform enough
to have produced many columns
so long and regular. |
Continue to Other Volcanic Rocks In and Near the Monument, See the Contents or Return to the Beginning |
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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.
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