After the Floods

Unraveling the mystery behind the Northwest's channeled scablands

 

Updated Nov. 24, 2009

The view from State Route 281, a few miles south of Quincy, Wash., doesn't seem like one of the world's more dramatic landscapes. Not to me, anyway. This is country to be endured (better yet, slept through) on the way to other, more captivating environments. The topography here is mostly flat, and whatever isn't paved is russet or beige or an irrigated green. But Gary Kleinknecht is doing his best to show off the region's subtle charms.

"So where we're standing, we'd be under, oh," -- he takes his bearings -- "probably 800 feet of water."

We are in the midst of the Channeled Scablands, a braided maze of buttes and canyons scoured out by massive floods thousands of years ago, and now blended into the workaday scenery of eastern Washington. A few miles north of us are the Frenchman Hills; the Saddle Mountains are to the south. Kleinknecht explains that the area they bracket, the Quincy Basin, was at one time under a huge temporary lake, Lake Lewis, which also covered the nearby Pasco Basin and the Yakima Valley. The lake only existed for a week or so, but in places it was nearly 1,000 feet deep -- transforming today's mountains into small islands, or submerging them completely. Then it drained swiftly away, leaving behind raw earth.

"We're surrounded by some of the most fascinating geology on Earth," Kleinknecht says, as a semi rumbles past, followed by an antsy string of cars. He watches them go. "And the people who drive past this stuff every day, they just don't have a clue."

Kleinknecht's quest, as president of the Richland, Wash.-based Ice Age Floods Institute, is to give them a clue. Last March, Congress made his job easier when it passed the Omnibus Public Lands Management Act of 2009, which included a bill for the formal designation of the Ice Age Floods National Geologic Trail. Scheduled to be completed by 2016, the trail will lead amateur geologists and their longsuffering kin along nearly 1,000 miles of roads, from the floods' origins in Montana to their exit on the Oregon coast.

"Now we can really start getting the story out," Kleinknecht says. "And it's a helluva story."

But it's a story that presents unique challenges in the telling. Most geological parks focus on contained, stationary features. This trail, the first of its kind, will be something else -- an attempt to put rock in motion, to give it narrative, a start and a finish. All of which raises the question: How exactly do you get people to see movement in something as permanent-seeming as stone?

Here's the no-frills version: About 15,000 years ago near the end of the last ice age, a lobe of the Cordilleran Ice Sheet, which covered much of Alaska and western Canada, stretched south to what is now Sandpoint, Idaho, blocking the Clark Fork River with an ice dam over 2,000 feet tall and 2,200 feet thick. The backed-up river formed an enormous lake, called Glacial Lake Missoula, which held over 500 cubic miles of water -- more than is held by Lakes Erie and Ontario combined. Over the decades, the water wormed its way through minute cracks in the ice, probing and wearing away at the base of the dam as only water can until the entire structure became critically unstable. When at last it failed, it did so spectacularly. A towering wall of water blasted out and rampaged across Idaho and eastern Washington at up to 80 miles per hour. Over 3,000 square miles of land were covered to a depth of 1,000 feet. The torrents peeled off columns of rock and boiled up at choke points along the Columbia Gorge, back-flooding so furiously that the Snake River ran in reverse. The waters rumbled on to present-day Portland, still hundreds of feet deep, backing up again at the narrows near Kalama, Ore., and forming another temporary lake in the Willamette Valley, before roaring on, past Astoria, another 100 miles or so to the edge of the Pleistocene coast, and then into the Pacific, spewing sediments out along the ocean floor as far south as California.

Glacial Lake Missoula took only two days to drain; the floods probably lasted two weeks. After they subsided, the ice dam started to re-form. Then, after 30 to 50 years, it failed again. The process repeated itself, perhaps more than 100 times over the next 3,000 years, before the Earth warmed and the Pleistocene Epoch ended. According to geologists, the Ice Age Floods, as they eventually became known, may have been the largest floods the Earth has ever experienced.

Great Article, Great Topic
Timothy Martin
Timothy Martin
Dec 17, 2009 09:17 AM
Unexpected article for HCN. My family and I traveled through the scablands area of eastern Washington this past summer and had a great time seeing the flood sites. We missed the visitors center in Wenatchee, though would have liked see. Eric Wagner did a great job with this article. Reminded me of David Quammen a little! Keep up the good work.
After the Floods: J Harlan Bretz
Norm Cimon
Norm Cimon
Feb 26, 2010 01:19 PM
The best part of the story, and I've heard it many times living as we do in NE Oregon, is that Bretz outlived all his more staid and, it needs to be said, un-scientific critics. He did the grunt-work, laid out all the evidence, he was the professional - the scientist. There's an endless list of geological metaphors available here, so let me use one: they were stuck in the uniformitarianist past. It would have been nice for him to be able to gloat a little, he earned it.

Loved the story. How about more of the same? We're surrounded by flood basalts here in the Blue Mountains. These thick layers of black rock, more than a dozen of them visible in the river canyons that feed down to the Snake, mark the initial emergence of the Yellowstone hotspot ten million years ago. That hotspot continues melting away rock to this day. The Snake River plain is but a burned out memory of the continent's path as it ratchets its way westward across the smoking caldera. Yellowstone keeps that torch burning hot, marking out the eons in its own spectacular way. Easy to see why people get enthralled when the step back to take a look.