Columbia River Gorge is the only major break of the range in the United States. When the Cascades began to rise 7 million years ago in the late Miocene, the Columbia River drained the relatively low Columbia Plateau. As the range grew, erosion from the Columbia River was able to keep pace, carving out the gorge and major pass seen today. The gorge also exposes uplifted and warped layers of basalt from the plateau.

History

Before European exploration,

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