Hello young people. The Palouse River Canyon, just south of Washtucna,
Washington. Welcome to Palouse Falls State Park. The crown jewel, the Palouse Falls itself. One hundred and eighty foot cliff with the
Palouse River cascading over basalt bedrock. It's a beautiful place especially in spring. But even in winter during a cold snap. You
get much of this water locked in ice.Equally impressive. But we're here for more than the waterfall.
We're here to talk about the river canyon itself. One of the most interesting
canyons you'll find anywhere. The upper stretch of the canyon above the
falls is perfectly straight, arrow-straight, a four mile stretch. Here by the falls, the canyon zig-zags back
and forth. And in the lower stretch there's a more classic
look to a coulee system with magestic buttes popping up from the canyon floor. And caves have been found with evidence of
human history going back 10,000 years. People have been enjoying this place for a
long, long time. Geologically this canyon is not much older
than 10,000 years. During the Ice Age this canyon was not here.
The waterfall was not here, the river wasn't even here. To tell the story of how this canyon formed,
let's go upstream. The peaceful Palouse River, a few miles north
of Palouse Falls. That's the road to Pullman in the distance there. Before the Ice Age floods, the Palouse River
used to flow parallel to the Snake River, and a divide, a ridge separated the two "V"
shaped river valleys. The ridge was composed of fractured basalt
bedrock, mantled with windblown silt know as loess. Que the Ice Age Floods. Coming from Montana,
cruising through northern Idaho and barreling down into this tranquil scene. Way too much water for this valley to handle. And the Ice Age floods easily over-topped
the ridge and dumped directly into the Snake River. The erosive power of that floodwater did serious
damage to the ridge in multiple places. What's now known as Palouse River Canyon,
H U Ranch Coulee and Devils Canyon. They're parallel cuts, deeply into the basalt bedrock. It wasn't just the loess taken away, it was
all the bedrock as well. Deep fractures that are parallel to each other
controlled where the floods did the most damage. Like taking a fire hose to the ridge and etching
out those deep fractures. The fractures formed originally 50 million
years ago in response to crustal compression from the south and a lateral torquing as well. The Palouse River took advantage of this.
In the old days the Palouse River Continued down it's river channel north of the ridge. That's now know as Washtucna Coulee and that
coulee's dry. No river is in it anymore. Instead, the Palouse River took advantage
of the deepest cut, took a left turn a south turn into the ridge and now forms the Palouse
River Canyon. So we've got our answer right? The Ice Age
floods cut this canyon, not the Palouse River. When the floods got the floor of this canyon
lower than Washtucna Coulee, the Palouse River permanently came in here and left it's old
valley high and dry. The Snake River effectively captured the Palouse
River. Something we call "Stream Capture". Today
Palouse Falls is impressive. A drop of 180 feet. In fact there was a world record
for a kayak drop recently. But back during Ice Age floods time, fill
the entire canyon with water. Brown, raging dirty water coming through,
thundering through this canyon. With the original position of the Ice Age waterfall down at
the Snake River. And through flooding had the lip of that waterfall
migrate back five miles to it's present position. The power of the Ice Age floods in the Palouse
River Canyon, south of Washtucna, Washington.
