Growing up in northern Arizona, spring was always an exciting time to finally pack away the snow shovels and de-icer and get outside. If you want to see enough running water in the desert southwest to actually get your feet wet, spring snowmelt season and summer afternoon thunderstorms are pretty much your only hope.
Spring in the Pacific Northwest is similar…except that instead of going from no water to a little water, we go from a decent amount of water to A LOT of water. Nowhere is spring runoff more apparent than 187 foot high Palouse Falls, which is about 1-2 hours (depending on your driving speed) north of Walla Walla, on the Palouse River just upstream of its confluence with the Snake River.
Normal people think lots of different things when they see Palouse Falls, among them “How do I get down there?”, “Wow, that’s pretty!”, “Where’s the snack shop?”, and “I really need to go to the bathroom after driving down that really bumpy, windy road”. All perfectly legitimate. Other people however see a kayak jump.
Palouse Falls garnered some attention in recent years when it became the site of the worlds largest kayak waterfall descent. In case that didn’t sink in, let me reiterate: someone paddled over that thing in a KAYAK.
As someone who has expertly piloted a kayak over 6″ riffles on the Palouse River below the falls, I can tell you that this is an impressive feat. Palouse Falls is nearly 200 feet; ants may be capable of surviving a fall off the kitchen counter but we aren’t designed to do such things. Just look at this picture.
If that was me, the discharge of the falls would be spiking dramatically right then due to the amount of bodily fluids I would have been emitting our of sheer terror.
The falls were formed by an phenomenon that comes in at #1 on our list of “Geological Terms That Make You Sound Like An Idiot If You Pronounce Them Correctly”: a jökulhlaup. If you are Icelandic, you’ll need no pronunciation guide. For the rest of you, that’s “yo-cooool-HOIP”. Once again, that’s “yo” as in the famous cellist Yo-Yo Ma, “coooool” as in “coooool Razor scooter man!”, and “HOIP” as in “House of International Pancakes.”
Now that we’ve got that squared away, lets set the scene: imagine you are an ice sheet, specifically the vast Cordilleran Ice sheet that covered the northern half of the North American continent during the last ice age. The climate is starting to warm; the mammoths are starting to die and those pesky humans are starting to increase in number. As the temperatures slowly increase, you start to feel a little sweaty and you begin to melt and retreat northwards to more suitable weather. All that glacial meltwater is getting funneled into river canyons that were cut tens of thousands of years earlier and are just now being uncovered by the retreating ice sheets. Even as a retreating ice sheet though, you will likely have a few appendages (called lobes) that reach several hundred kilometers south of the main ice front. These lobes block some of the river channels, forming a barrier that impedes the river’s progress. Massive quantities of water back up behind the ice dam, creating lakes larger than several of the Great Lakes. Remember though, you are a big piece of ice, and what does ice do in water? It floats. Once the lake becomes large enough, your appendages are no longer strong enough to maintain contact with the bottom of the canyon. The entire ice dam begins to rise slightly in the water, opening a seam at the base of the dam through which water begins to rush, eating away at the dam from underneath. Eventually, undermined by the water, the entire ice dam catastrophically collapses, draining the entire lake in a matter of hours and sending thousands of square kilometers of water rushing across the landscape. That’s a jökulhlaup. After the ice dam is blasted away, you, the glacier, slowly flow back down into the canyon over the next few years, creating a new dam and lake and starting the process all over again.
Anthropomorphized geologic features notwithstanding, this actually happened…at least 40 separate times at the end of the last ice age, from about 15,000 to 13,000 years ago. The river was the Clark Fork of the Columbia River, the ice dam was located near Lake Pend Oreille, Idaho, and the lake was glacial Lake Missoula, which stretched from northern Idaho almost all the way to Yellowstone National Park. The ice dam collapsed every few hundred years, sending a Lake Erie’s worth of water rushing down the Columbia River, across what is now Eastern Washington, all the way to the Pacific Ocean.
Look at what happens to your yard after a big storm and you know it doesn’t take that much water to carry out some significant erosion. Palouse Falls is located in one of thousands of scour marks, known as “coulees,” that were gouged out of the basalt bedrock of Eastern Washington by the force of these floods.