Cascades and Columbia Together
Cascade Range and Columbia Plateau
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The Cascade Range and the Columbia Plateau are closely related. The plateau came before the mountains, built by flood basalt eruptions that culminated in the Miocene about 15 million years ago. (That's Columbia basalt on the right.) The range began farther west, some 45 million years ago, and has migrated east over the years, encroaching onto the plateau. Mount Hood, on the left, is part of the Cascades. (c) 2005 Andrew Alden, licensed to About.com, Inc. (fair use policy)
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