Steamboat Rock, Washington - Glacial Lake Missoula Flood Features on Waymarking.com

Steamboat Rock is a massive basalt butte, several miles long and 800 feet high with a surface area of 600 acres. It looms like a battleship above the 27 mile long Banks Lake, a manmade reservoir that fills the upper Grand Coulee in northeastern Washington. It is a main stopping place on a proposed Ice Age Floods National Geologic Trail--a network of sites in Montana, Idaho, Washington, and Oregon, each bearing the dramatic imprint of the cataclysmic Missoula Ice Age Floods that swept 600 miles across the region 15,000 to 18,000 years ago.

An ice dam, over 2,000 ft high and 30 miles wide, had blocked the Clark Fork River in northern Idaho, creating Glacial Lake Missoula, an enormous body of water that stretched 200 miles into northern and western Montana. Eventually, the ice dam holding back Lake Missoula collapsed. A towering mass of water and ice burst through in a thunderous rush toward the abyssal plains of the Pacific Ocean. This process was repeated perhaps as many as one hundred times over the next 2,500 or so years.

The powerful floods chewed through the basaltic plains of the arid Columbia Plateau, stripping away more than 50 cubic miles of rich topsoil, gouging deep canyons (“coulees”) in some places, piling mountains of gravel in other areas, and scattering enormous boulders and great rocks called glacial erratics all the way from the Rockies to the Willamette Valley in Oregon. The catastrophic floods created the gorges, and “channeled scablands” (so-called because they resemble scabs on the back of an animal) of the Columbia Basin. There were huge ripple marks that proved the lake had emptied in a sudden rush. The floods also carved out numerous kolk depressions.

The ice age floods clawed out and then left behind a bone-dry canyon that was more than 50 miles long, up to 900 feet deep, and, in places, five miles wide. French Canadian fur trappers called it the Grand Coulee, after the French verb couler, meaning “to flow.” The monolith that came to be known as Steamboat Rock is located at the northern end of Grand Coulee. A “stubbornly uneroded piece of volcanic plateau,” in the words of writer William Dietrich, was left sitting “like a sternwheeler grounded by a departed tide, silent and evocative as an old wreck”.

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Date Logged Log User Rating   07/26/2014 Cool Cow Cachers visited it 08/25/2013 AndrewsDK visited it 08/09/2011 Rose Red visited it 01/26/2011 wildernessmama visited it 11/09/2007 Hikenutty visited it

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