Plucking the Columbia Basalt
Cascade Range and Columbia Plateau
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Washington state route 14 runs up a natural channel created by Missoula floodwaters hundreds of meters deep. The floods ripped basalt boulders out of the solid flows in the process of hydraulic plucking, or quarrying. The cliffs behind, although they show some weathering in the last 10,000 years or so, are still fresh—without the floods' erosion, they would be as smooth and subdued as the basalt heights beyond. (c) 2005 Andrew Alden, licensed to About.com, Inc. (fair use policy)
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