From Montana westward to the Pacific Ocean, a long-ago series of cataclysmic floods remodeled the landscape, leaving amazing formations in their wake.
By Rhonda Ostertag
Looking for an offbeat travel theme? Well, how about vacationing where a giant ice-age flood ripped through the northwestern United States? The settings are dramatic and the history amazing.
During the last ice age, a series of gargantuan floods, known as the Missoula Floods, scrambled the landscape of Montana, Idaho, eastern Washington, and northern Oregon. The floods broadened the Columbia River Gorge, rerouted the Snake River, and, in places, made both rivers run backward. What visitors see today is an eerie lunar-like landscape of cliffs, stranded house-size boulders, ship-sized rocks, grand coulees, dry cataracts, wildlife scablands, giant ripples, 30-story-high gravel bars, and a wondrous gouged-out waterfall canyon.
Because no single route can explain this chaos of water and excavation, a collection of discovery pathways (both primary and secondary driving routes) can make up your trip. Seven sites on the floods’ path already have been named national natural landmarks.
Whether or not a trail honoring the floods will receive designation from the National Park Service was doubtful as of early 2006, although in 2001 a study was done to consider it. Regardless, motorhome travelers can still enjoy the views, because many state parks, private campgrounds, and local tourist routes and interpretive boards are already in place. In addition to geology tracking, recreation opportunites include sight-seeing, hiking, fishing, boating, and bird-watching.
Imagine the biggest of these floods. It began at Lake Missoula, near Missoula, Montana, as a glacial dam split apart, allowing water and debris to rush westward into what is now Oregon and Washington, forever changing the landscape. The water body created by the dam encompassed 3,000 square miles and contained more water than Great Lakes Erie and Ontario combined. When the 2,000-foot ice dam collapsed, 500 cubic miles of water exploded out of the dam at speeds in excess of 65 miles per hour. Calculations show that Lake Missoula could have emptied in as little as 48 hours. If you had a front row seat downstream, you would have passed an unsettling half hour marked by crescendoing thunder, trembling earth, and winds reaching hurricane force, all for no apparent reason. Then it would arrive, an unstoppable onslaught of water swamping heights of 1,000 feet and roiling with chunks of basalt, uprooted trees, and the gravel and sediment from four states. This flotsam carried boulders weighing 200 tons more than 500 miles from their place of origin. The footprint of the floods covers 16,000 square miles, with many of the floods’ features large enough to view from space by satellite. In turn, the bizarre landscape has lent an understanding of the topography on Mars.
Discovery points for the geologic trail lie mostly in Montana and Washington, but this story will travel in all four states. A natural starting point is Missoula, Montana. Faint telltale bathtub rings on the hillsides south of the Missoula airport and on Mount Sentinel and Mount Jumbo east of town hint at the ancient lake. The horizontal lines reveal the changing lakeshore heights. The highest ring is at the 4,200-foot elevation, 1,000 feet above the current town.
From Missoula, travel north to Flathead Lake, the largest freshwater basin in the West. It harks back to Glacial Lake Missoula, but it’s no more than a baby’s footprint in comparison. The glacial lake stretched out 186 miles long and 65 miles wide; Flathead Lake is 28 miles long and 5 to 15 miles wide. Conjecture has it that Flathead is a remnant of the glacial lake.
In its spectacular mountain setting, this lake’s cobalt recreation water woos visitors. Favorite pursuits are fishing, boating, hiking, horseback riding, golfing, and perhaps watching a play at the Bigfork Summer Playhouse. Boat tours offer ways to become acquainted with the lake. Boat rentals are offered in the towns of Polson, Somers, and Bigfork. The logging town of Bigfork has transitioned into an attractive little tourist area, complete with espresso. In July, fruit stands loaded with cherries and huckleberries coax lakeside travelers aside. Plenty of campgrounds rim this area.
South of Flathead Lake, Mission Valley, threaded by U.S. 93, holds the wildlife lands of the ancient lake bed. The pond-marsh habitats of Pablo Reservoir and Nine-Pipe National Wildlife Refuge attract flyway travelers, along with their binocular-eyed following. More than 200 bird species have been identified in the valley; spring and fall migrations bring tundra swans to the sky. The valley is also home to the National Bison Range. Dramatic symbol of the American West, the American bison is the primary reason visitors venture to this outback near Moiese.
The bison range’s Red Sleep Mountain Scenic Drive not only shows off wildlife but rounds past interpretive markers describing the Missoula Floods, as it twists through an attractive prairie hill setting. For this drive, though, leave the motor coach at the campground or at the visitors center parking lot and tour in the towed car. Motorcycles, by the way, are not an acceptable alternative because of human-animal safety concerns.
Now, on to Idaho. Travel from the bison range back to Interstate 90 west and turn north of Coeur d’Alene on U.S. 2/95 to Farragut State Park, at the south end of Lake Pend Oreille. According to scientists, this is where that giant ice dam once stood. The park offers a campground and plenty of beauty. Human-made dams enlarge the lake, a popular wet playground.
From here, you can continue west on I-90 to Washington or take a loop detour via U.S. 95 south to Lewiston, Idaho, and its compadre across the Washington state line, Clarkston. Lewiston roughly marks the end of the Snake River backsplash. It picks up the tale after the flood surge sent the Snake River backward for 80 miles. A gravel bar south of town shows the stacked sands of the Missoula Floods. Jet boat tours on the Snake River are a Lewiston signature.
Although the mark on Idaho is slight, the flood imprint on eastern Washington is both sweeping and striking. Coulee channels gouged out by the runaway waters, raked scablands, rounded loess (wind-carried glacial silt) hills, and potholed wetlands are among the legacy. Washington wheat farmers plow around the displaced house-size boulders (erratics) that dot their fields. Key flood viewing sites are at Steamboat Rock, Sun Lakes, and Palouse Falls state parks; Turnbull and Columbia national wildlife refuges; and Walulla Gap, at the east end of the Columbia River Gorge.
If you opted to forgo the Clarkston-Lewiston foray, you’ll shave miles off your trip by heading straight west from Coeur d’Alene to Spokane, and then west via U.S. 2 to Grand Coulee Dam. Of the broad flood channels cutting the Columbia Plateau, Grand Coulee is the largest and finest example of a receding cataract. Grand Coulee Dam, the popular tourist attraction at the town of Coulee Dam, actually blocks the adjacent Columbia River channel and forms Lake Roosevelt, centerpiece to Lake Roosevelt National Recreation Area. Visitors can tour the dam’s interpretive center, learning about the dam and area geology, or take in the nighttime laser show.
Within the Grand Coulee basin, manmade Banks Lake is home to Steamboat Rock State Park (south of Coulee Dam off State Route 155). The park’s namesake is a landmark 1,000-foot-high ship-like rock, the remnant of an island that parted the floodwaters. Within the park, much smaller Thompson Lake serves up Steamboat Rock views. Camping, fishing, boating, hiking, and birding are pleasurable pastimes.
On State Route 17 below Dry Falls Dam, lower Grand Coulee holds one of the most easily viewed discovery sites: Dry Falls, a state heritage area at Sun Lakes State Park. Overlooks and a seasonal visitors center peer out on this naked 3.5-mile-wide horseshoe-shaped cliff with a 400-foot drop that was awash during the Missoula Floods, buried under 300 feet of water. The waterfall’s skeleton is bigger than Victoria Falls in Zimbabwe-Rhodesia. But it’s the volume of water that passed over Dry Falls that puts it in a league of its own. By comparison, today’s Niagara Falls would look like a trickle.
Camping, boating, fishing, golfing, and horseback riding engage guests at Sun Lakes State Park, with boat and horse rentals available. Within the park stands Umatilla Rock, another classic ship-rock island; it divided the flow of the ancient waterfall. Dry Falls Lake is the remnant plunge pool.
From here, head to an out-of-the-way spot called Palouse Falls, located approximately 120 miles southeast from Coulee City, off State Route 261. This truly is a flowing waterfall. Palouse Falls State Park (near Starbuck) has a tiny primitive campground, so motor coachers are better served at Lyons Ferry Marina to its south.
The glacial floods rerouted the Palouse River, excavating the gorge now seen. In the upstream retreat of the Snake River cliffs, weak zones in the basalt left behind picturesque pillars. Fryxell Overlook offers a bluff vantage of the 200-foot whitewater column thundering into the canyon.
While you’re this far south, continue the way the water flowed, toward Wallula Gap. Take U.S. 12 south to Walla Walla and continue west to the spot where the pinched gorge turned back the mighty Columbia and its upstream tributaries, forming temporary Lake Lewis. Geologists estimate that every day the gap received four times as much water as it could hold. The waters that punched through the gap chewed at the sides of the Columbia River, widening the divide between Oregon and Washington.
As you travel west of there via State Route 14, you follow the Columbia River as the gorge’s National Scenic Area celebrates the stunning beauty and geology of this great chasm. Trails, viewpoints, waterfalls, and rip-away basalt features, such as Washington’s Beacon Rock and Oregon’s Rooster Rock, contribute to the discovery.
And as one may suspect, all the water ended up in the sea. The trail terminates in Astoria, Oregon, and the Pacific Ocean, where the flood-transported sands actually raised the ocean floor. Geologists estimate that more than 90 percent of the silt ended up on the ocean bottom, never to be seen again ….
To learn more about the Missoula Floods and their impact, check out these Web sites, which belong to the Ice Age Floods Institute and Glacial Lake Missoula, a part of the Montana Natural History Center, respectively:
Further information about travel spots mentioned in this article is available from the following state travel bureaus:
301 South Park
P.O. Box 200533
Helena, MT 59620-0133
(800) VISIT-MT (847-4868)
Idaho Division of Tourism Development
700 W. State St.
P.O. Box 83720
Boise, ID 83720-0093
(800) VISITID (847-4843)
Washington State Tourism
P.O. Box 42500
Olympia, WA 98504
(800) 544-1800 (8:00 a.m. to 5:00 p.m. Pacific Time Monday – Friday)
670 Hawthorne S.E., Suite 240
Salem, OR 97301
National Natural Landmarks Related To The Missoula Floods
- Giant Flood Ripples, Montana. The fast flow of the Missoula Floods created these watermark ridges.
- Wallula Gap, Washington. This narrow gap in Horse Heaven Hills created a bottleneck that temporarily formed Lake Lewis.
- The Great Gravel Bar of Moses Coulee, Washington. This outstanding gravel bar is on the channeled scablands area.
- Drumheller Channels, Washington. This floods-caused butte-and-basin scabland is on the Columbia Plateau.
- Grand Coulee, Washington. The largest of the Columbia Plateau coulees is probably the world’s finest example of a recessional cataract gorge.
- Crown Point, Oregon. A 900-foot-wall of floodwater passed this dramatic high point in the Columbia River Gorge.
- Willamette Flood Plain, Oregon. This is the largest remaining native, unplowed interior valley grassland in the region.