Between The Dalles and Hood River, soil and talus were swept from the valley walls, leaving the series of clean steps we now see on the barren lava flows of Columbia River Basalt. At many places the accumulations of talus, which one would expect to see after 15,000 years at the base of the cliffs, have yet to form substantial slopes. Just west of Mayer State Park, the river makes an abrupt turn to the north. This change in the course of the floods caused the cliffs to be undermined so extensively that a great landslide developed, down which the Scenic Highway 30 swings in a series of turns forming the Rowena Loops.
The almost vertical 600-foot-high cliffs here were overtopped by at least 200 feet of water, which cleaned off much of the overlying The Dalles Formation and left several scabland channels.
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