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Oregon Trail, Part IV - The Deluge

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“Ages End” - Missoula Flood heads down the Gorge, Crown Point in the foreground.
Stev Ominski

In the last installment of Oregon Trail we looked at horned gophers and Hell Pigs, plus volcanoes and some of the most immense lava flows the Earth has seen in 500 million years.

Oregon was built & shaped by cataclysm. We’re going to continue that theme partly because destruction is fun, and partly because our University of Oregon Ducks wouldn’t be here without it.

One of the main reasons Oregon was settled back in the day - both by Native Americans & later white pioneers - is the Williamette Valley’s uncanny fertility. It’s lined with incredibly deep topsoil (up to half a mile deep in some places) that creates some of the most fertile farming land in North America.

Now, river valleys are always rich places, but few reach the sort of Garden of Eden territory in west Oregon that causes people to trek halfway across a continent in a covered wagon, risking high mountain passes & drowning & broken wagon axles & “You have died of dysentery”.

Wheat, corn, potatoes, berries, hops, wine grapes, the list goes on. You can grow things here easy, real easy, not many places can match it.

But why?

To answer that, let’s pan the camera over to the Palouse in eastern Washington. WSU country.

There’s a region there called the Channeled Scablands – it’s a weird place where most of the topsoil’s been stripped away and amongst the exposed rocks odd channels have been carved going every-which-way in the landscape without much regard for topography.

The Scablands

Some areas there have undulating crests similar to beach sand that’s been rippled by waves, but on a huge scale. It’s a strange & desolate place – very few similar to it on earth – and for decades it baffled geologists. It just doesn’t quite make sense.

And where did all their dirt go?

Short answer, to Eugene. Here’s how it went down.

Back in the Ice Age, glaciers would often dam up river valleys with ice, causing lakes to form. One particularly large one occurred in western Montana – known as Lake Missoula, it covered 3,000 sq miles, was 2,000’ deep, and held about half the volume of Lake Michigan. That’s very big. It was basically a miniature freshwater sea.

The problem with ice dams is that they’re not permanent, and under the right conditions (a combo of warmer temps & water pressure) they can be fragile. You really don’t want to be downstream from a fragile dam.

Sometime around 14,000 years ago Lake Missoula’s ice dam ruptured and the contents of this small inland sea headed west. This is called a Glacial Lake Outburst Flood and though others have occurred elsewhere, none have approached this scale.

“Floods Dam Failure” - the glacial dam at Lake Missoula ruptures, look out below...
Stev Ominski

The wall of water was in some places 1,000’ tall and rushed forward at up to 80mph, over a swath of Washington hundreds of miles wide. Thus, the Channeled Scablands were formed – the initial stage of the flood basically demolished the landscape there, etched the random channels you can still see today, and scoured clean all their topsoil (along with a bunch of gigantic rocks too).

It eventually flowed into the Columbia River valley, carving out the dramatic cliffs of the Gorge as we know it and reaching heights of over 700’ above the current river surface. After the Gorge the Columbia got plugged up by another dam near Kalama Washington, so all this water headed south into the Willamette Valley.

“Inundation At Beacon Rock” - for reference, Beacon Rock is about 850’ tall.
Stev Ominski

It formed what is known as Lake Allison, a temporary prehistoric lake about 400’ deep and stretching from around Vancover WA down south to our beloved Eugene. Finally with the water staying put, all that dirt of eastern Washington was able to settle – the lake eventually drained away & deposited a thick layer of good fertile Palouse topsoil for future Oregonians to tap. Sorry Cougs!

“Lake Allison” - essentially the Willamette Valley half-filled with water.
Stev Ominski

It also brought with it the solid-iron Willamette Meteorite – the largest known North American meteorite – which had probably crashed in Montana but got carried along by the flood to a spot near Portland (it’s now in a NYC museum, but that’s a story for later).

Scientists estimate that the total peak flow of this flood was more than 10 times all other rivers of the world combined, and released energy equivalent to 4,500 megatons of TNT - for reference, this is about triple the power of the world’s total nuclear weapon arsenal. Oh, and it happened at least 40 times over the course of a couple millennia.

Without these floods (now called the Missoula Floods, or Bretz Floods after the geologist who first theorized them), civilization probably wouldn’t have thought the Willamette Valley particularly worth developing, UO wouldn’t have been founded in Eugene, and Marcus Mariota would have been slinging touchdowns for Bama or USC. Joey Harrington (of west Oregon stock himself) might not have even existed, neither Uncle Phil. It would have been a poorer world from a Duck’s perspective.

So next time you’re on your patio enjoying an Oregon IPA or Willamette pinot noir, picture a 700’ wall of water bearing down on you filled with tumbling boulders and trees and 16-ton meteorites - then maybe raise your glass and give thanks for the bounty it provided.

Epilogue: Events like this happen on such a scale & with such violence, they’re hard to really visualize. For this article, Oregon artist Stev Ominski (stevominski.com) was kind enough to lend me use of his awesome - in the original sense of the word - paintings of the flood. These are all based on current science & more or less to-scale. Stev has a lot of other great pieces too, mostly Pacific NW landscapes & scenes.

The header image is called “Ages End” and depicts the water sweeping down the Gorge from the vantage of Crown Point with a mostly-underwater Beacon Rock in the distance. You may have seen it before, since a copy hangs in the U of O Museum of Cultural & Natural History.

Potential Discussion Topics:

  1. Ever been to the Palouse and/or Scablands? Pretty out-there, huh?
  2. Got any good flood stories?
  3. What’s better, Oregon beer or Oregon wine?

Next Week on The Oregon Trail: People Move Here