Visiting the Ice Age Floods National Geologic Trail

Head into the visitor's center at Dry Falls State Park and you can see an artist’s conception of the falls during one of the periodic ice age floods. The lower photo shows Dry Falls as it appears today, looking across the line of 350-foot cliffs. Photo by the author.

A mile south of Washtuchna, Washington, State Road 261 – which has been curling through close hills – suddenly straightens and drops down the wide Washtuchna Coulee. On either side of the road the land sweeps up to rocky outcroppings and ledges. Drive 60 mph and you’re shooting across the landscape at about the speed of the ice age floodwaters that first tore open this former river channel some 15,000 years ago.

Turn left and you’re driving in and out of those rocky ledges themselves. This is the road to Palouse Falls State Park, which might become one of the favorite stops in the Ice Age Floods Geologic Trail now being developed by the National Park Service.

The falls of the Palouse River drop nearly 200 feet into a narrow canyon, creating a can’t-miss photo opportunity and at least a sense of the water that once coursed through the bare rock beneath this otherwise fertile plain. But it’s a tiny remnant of the 600-foot walls of water that once roared over the land, from upper Montana through upper Idaho and down the eastern half of Washington to Oregon and on out to the sea.

As photogenic as the falls are, it’s the landscape around them that is unusual and that has attracted the attention of the Park Service. Geologists believe that at the end of the last ice age, a huge glacial lake in the area of what is now Missoula, Montana, periodically dammed and breached, releasing ice- and rock-laden torrents of water that in a matter of days ripped away the top soil and cut into the underlying basalt.

The erosive deluge created steep buttes, twisting coulees, and islands of tear-drop shaped earth where water flowed on either side – difficult terrain that earned the unflattering name of “scablands,” perhaps because the low, cracked outcroppings of basalt often look like dark, crusted wounds on the skin of the earth. This effect is especially evident around Sprague, Washington, just off Interstate 90, and the “Channeled Scablands” farther south.

It is the interstate, running through both Missoula and Spokane and on out into the scablands, that will likely carry many of the visitors interested in the ice age floods. Palouse Falls lies about an 90 minutes south of the highway, below Ritzville, Washington. Travel a half-hour farther west on the interstate to Moses Lake, and then an hour north on State Road 17, and you will pass through erosion on a tremendous scale. This is Grand Coulee, once the bed of the now-diverted Columbia River, but torn wide and deep by the ice age floods. What remains are 900-foot cliffs and a retreating series of plunge pools that lead to Dry Falls State Park.

The park overlooks a 350-foot extinct waterfall that stretches 3.5 miles across the coulee. In its day it would have dwarfed Niagara – except that the fall’s days were short-lived indeed: The waters ran only 48 to 72 hours at a time, and then were dry for years before the lake breached and the land flooded again. It is this devastating on-and-off tap that fascinates scientists: Cataclysmic geology, which changes the landscape in a matter of hours, was once believed to happen mostly in connection with volcanoes, but evidence now indicates that glacial floods can – under the right conditions – quickly alter the earth as well.

Dry Falls is scheduled to host one of five principal interpretive sites on the national park trail, with others near Missoula, where walls above the town still bear the marks of the ancient lakeshore; Cabinet Gorge, Idaho, where the Clark River was repeatedly ice-dammed to create Glacial Lake Missoula; Walla Walla in southern Washington, where the floodwaters backed up to create a temporary lake, and The Dalles in Oregon, where the Columbia Gorge was partly formed by the floods.

Smaller sites are planned at places like Palouse Falls and Oregon’s Willamette Valley, which also filled up during the deluges.

Discussions between the state and the federal government are under way now to determine how the sites will be developed. At Dry Falls, a small interpretive center built in 1965 (and looking very much of its time) might be preserved, as will the Depression-era stonework around the edge of the overlook. Preliminary plans are to build a larger NPS center south of the existing overlook.

It will be years before the trail is fully developed and interpretive centers can be built, but national park enthusiasts can get a preview by visiting the sites now. Maps of proposed routes are available at this page and in local guidebooks such as Bruce Bjornstad’s On the Trail of the Ice Age Floods and Paul Weis & William L. Newman’s The Channeled Scablands of Eastern Washington can help create itineraries that will carry travelers back in time and down the same paths that once carried the earth-shattering waters of Glacial Lake Missoula.

Comments

Oh, wow. The first time I visited the eastern Washington scablands, I was a kid. I now live in western Washington, and have been back and forth to that part of the state several times, once with a birder friend who showed me some seriously magnificent wildlife over there.

I can't think of a more deserving place for a geologic trail. I hope I can still hike once they've got it finished.

One common misconception is that Dry Falls was produced by the Missoula Floods alone. Essentially Dry Falls was the retreating cataract the glacier-diverted Columbia River which carved Lower Grand Coulee, and as such produced a spectacular waterfall that dwarfed Niagra for many thousands of years. If there were never a Missoula Flood event, we would still have a Dry Falls here.

However, during a Missoula flood event, that exaggerated flow washed away vast swaths of topsoil, sand and gravel down to basalt bedrock, produced incredibly powerful vortexes that "jack-hammered" enormous potholes into that same bedrock, and otherwise were instrumental in hydraulically sculpting the unique landforms that exemplify the 'channeled scablands' of Eastern Washington, which can be seen today from the visitor's overlook at Dry Falls.

PS: The first sentence for the caption below the photos at the top of the page should read, in part "...an artist's conception of the falls while the Columbia River was glacially-diverted for thousands of years."

During the initial stages of a Missoula Flood event, the falls and the surrounding countryside were under several hundred feet of water!