Umtanum Ridge Water Gap

These anticlines are part of the Yakima Fold Belt near the western edge of the Columbia River Plateau.

The great basalt flows of the Columbia Basin and of the Ellensburg Formation, in some places over 5000 meters (17,000 feet) thick, have been folded into ridges (anticlines) and valleys (synclines) running roughly east–west as a result of north–south compression.

This unusual juxtaposition (rivers cutting through ridges rather than flowing through apparently more favorable routes) is an example of geologic precedence.

The ancient Yakima River is believed to have been there, flowing southward above the relatively flat basalt layers.

The river continued to follow its historic course, cutting downward through the basalt to maintain a relative level.

Photo showing roads parallel to the Yakima River as it discharges from the Yakima River Canyon outside of the city of Selah .
Fly fishing from drift boat on the Yakima River in the Yakima River Canyon.
A view south from Umtanum Ridge into the Yakima Canyon.
A view from the north near Ellensburg, Washington toward the Yakima Canyon.