Columbia Gorge and Grand Coulee, 2003

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin - Green Bay

The pictures here supplement the pictures in theChanneled Scablands Virtual Field Trip. Detailed explanations of the geology can be found there.

Columbia Gorge

Approaching the Columbia River from the west along Interstate 90.
Above: Just north of the bridge at Vantage is this wild horse sculpture on a mesa, overlooking a rest area. Below: views of the gorge from the rest area.
Below: Not far to the north is the Gorge Amphitheater, a popular venue for rock concerts (appropriate!)

Below: Panorama of the Columbia River gorge from the Wild Horse Rest Area

Vantage to Ephrata

Diatomite is common in the sedimentary interbeds in the vicinity of the gorge.
Left and below: low-relief scabland terrain.

Lower Grand Coulee

Looking south along lower Grand Coulee from just south of Dry Falls.
Lava flow contact.

Dry Falls

Left: the visitor center.

Below: opposite side of the gorge showing flood-transported boulders. At the height of the floods, this entire area was under water and the falls would have been completely submerged. The water would have been moving about 100 km/hour.

The channel above the falls, showing scabland topography.

Below: Panoramas of Dry Falls

Upper Grand Coulee

Left and below: near the upper end of upper Grand Coulee is one of the rare places where scablands are developed on rocks other than basalt. Here lava flows overly granite, which was plucked in a manner quite different from the basalt. The lake is Banks Lake, formed by damming upper Grand Coulee at both ends.
Looking south to Steamboat Rock.
Looking north through the gap where upper Grand Coulee joins the Columbia River.

Grand Coulee Dam

North end of the dam abutting granitic rocks.
Granite with dike and xenolith.

Left and below: channels cut in loess east of Grand Coulee.

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Created 15 November 2005, Last Update 08 June 2020