We've got it pretty easy here in the Inland Northwest, as far as natural disasters go. The Earth's crust under our feet is relatively stable, and we enjoy a moderate amount of precipitation. Hurricanes, tornadoes and plagues of insects are unheard of. Except for intermittent ice storms and the occasional ash fallout from the eruption of a Cascade Range volcano, cataclysm on a wide scale is something that always seems to happen somewhere else. But that wasn't always the case.
On Friday at 9 pm, KSPS-TV will present Sculpted by Floods, an hour-long documentary hosted by Alison Kartevold that revisits a devastating event that drastically altered the landscape of four states and created Eastern Washington's dramatic and rugged profile.
If you were standing where you are right now about 15,000 years ago, you might have a very different perception of the geologic stability — indeed, the very habitability — of Spokane and all of Eastern Washington. Imagine yourself and every living and inert thing for as far as you could see suddenly swept up in a 1,000-foot wall of water moving at nearly 70 miles an hour — a torrent containing more than 500 cubic miles of water. Imagine being just one more piece of detritus caught within the largest known flood in the history of the Earth.
"All that water came through here in a matter of two to three days," says Kartevold. "Can you imagine? I mean, they don't like to use the word 'wall' of water because it wouldn't necessarily start all at once, but what else? I guess a better way of describing it is as a wedge."
Wall or wedge, it doesn't really matter. What scientists agree on is the original location of the floodwaters, the geographic areas affected and the cause.
Near the end of the last ice age, most of Canada and parts of the Pacific Northwest were under a glacier. A finger of this sheet of ice moved into the Clark Fork valley in North Idaho and dammed the river where it now empties into Lake Pend Oreille. Over time, the blocked flow of the Clark Fork together with glacial runoff created a huge inland lake behind the dam, eventually filling the valleys all the way to Deer Lodge, Mont., with water that, in places, was more than 2,000 feet deep, making islands out of mountain tops. At its peak, Glacial Lake Missoula contained more water than Lakes Erie and Ontario combined.
"The water kept rising until it came to a critical point and the dam could no longer hold it back," says Kartevold. "There are different theories about how the ice dam broke, but right now, the most popular one is that the water eventually floated part of the ice dam and once it got underneath, it eroded it away."
The lake emptied rapidly, dumping its entire contents through the mountains of North Idaho and into the basins of Eastern and Central Washington. The floodwaters wrecked havoc, stripping away topsoil to bare basalt, gouging out coulees, creating basalt pillars and reversing the flow of several major rivers, including the Snake.
Kartevold and videographer Jim Zimmer, backed by KSPS, have combined extensive research, computer animation, beautiful photography and old-fashioned storytelling to bring the tale of this ancient flood to life. Sculpted by Floods revisits the scientific evidence, beginning with telltale signs of an ancient inland lake and ending with the scoured landscape of Eastern Washington. Such evidence, says Kartevold, is all around us.
"If you've ever been to Missoula, look up on the hillsides, and you'll notice these parallel lines that run along them. Those are the old shorelines of Lake Missoula."
Closer to home, the marks left by the raging floodwaters are more dramatic.
"The water would pick up all this debris as it went, just like any river does, and it would speed up and slow down depending on how it was channeled. Where it slowed down, it would deposit things, where it sped up, it would do more scouring. Good examples of things it created would be Dry Falls and the double cataract it formed. The whole Grand Coulee was quarried by these flood waters. It also created the Spokane aquifer. All the gravel in the valley and the Rathdrum Prairie was deposited by the flood."
"That was one of the fun things as we went along the trail," she adds. "You know, we live in the Northwest and we see these features all the time. Our whole lives, we've been surrounded by these things that were created during that period, but we don't realize it."
Sculpted by Floods premieres on KSPS-TV (Spokane Channel 7) this Friday, Feb. 23, at 9 pm. It airs again on Sunday, Feb. 25, at 6 pm.