The Devil's Canyon

Description

The same violent glacial floods which carved out the channeled scablands in eastern Washington helped to form the Devil’s Canyon coulee.  North of Lower Monumental Dam on the Snake River, Devil’s Canyon linearly extends five miles toward the town of Kahlotus, WA. Once a floodway channel from Washtucna Coulee to the Snake River Valley, Devil’s Canyon is a recessional cataract canyon, meaning that the floodwaters over-topped Washtucna Coulee and eroded the basalt and undercut the edges of the channel, forming the canyon.

The Purcell Lobe of the Cordilleran ice sheet formed an ice dam which plugged up the Clark River Valley, forming glacial Lake Missoula. Periodically, the dam failed and the lake drained, releasing vast amounts of floodwaters to the south and southwest (Weis and Newman, 1976).   Nearly four hundred feet in elevation separated the waters of the Washtucna Coulee from the Snake River, the resulting fluid pressure leading those floodwaters to preferentially erode along the fractured basalt and spillover (Bjornstad et al., 2007).  The wall rock of Devil’s Canyon also resulted from flooding: the basalt flows that make up the Wanapum and Grande Ronde Basalt formations of the Columbia River Basalt Group formed 15 to 16 million years ago, flooding across much of Washington, Idaho, and Oregon (Reidel et al., 2002).   It was fractures in these basalt flows that the floodwaters spilling over from Washtucna Coulee were able to exploit in their deviation toward the Snake River.

A gravel mound projects from the mouth of the canyon, extending a third of the way into the Snake Canyon (Bretz et al., 1956).  Kahlotus Lake once existed within the Washtucna Coulee to the north of Devil’s Canyon; since the water table lowered, the lake has vanished (Bjornstad 2006).


Images Show

Recessional Cataract

Recessional Cataract

Source: Modified from John Sonnechson's Bretz Flood's | Creator: Cassandra Hennings [View Additional File Details]

Devil's Canyon Geologic Map

Devil's Canyon Geologic Map

Source: Modified from Bretz, Smith, and Neff 1956 | Creator: Cassandra Hennings [View Additional File Details]

Aerial photo looking west of the northern end of Devil's Canyon with the town of Kahalotus

Aerial photo looking west of the northern end of Devil's Canyon with the town of Kahalotus

The recessional cataract at Devil's Canyon retracted up the area labeled "cataract". The water that eroded the canyon flowed from the north as a spill-over from Washtucna Coulee | Source: Tom Tabbert trike flyer extraordinaire! | Creator: Dr. Chad Pritchard [View Additional File Details]

Aerial photograph looking north from the Snake River up the Devil's Canyon

Aerial photograph looking north from the Snake River up the Devil's Canyon

Source: Thanks to the trike flights of Tom Tabbert! | Creator: Dr. Chad Pritchard [View Additional File Details]

Cite this Page

Cassandra Hennings, “The Devil's Canyon,” Ice Age Floods Explorer, accessed April 29, 2017, http://floodexplorer.org/items/show/22.
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