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Devils Postpile National Park Geologic Story
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Curved Columns
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.
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Continue to Other Volcanic Rocks In and Near the Monument or Return to beginning
| Devils Postpile geology home |
Devils Postpile National Monument home |
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http://www.nature.nps.gov/grd/usgsnps/depo/dpgeol8.html
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