Missoula Floods, Ice Age Floods, and Pacific Northwest Geology | Scott Burns
The Pacific Northwest looks normal because we are used to it.
The Columbia River Gorge, The Dalles, Eastern Washington, Portland, Lake Oswego, the Willamette Valley. It all just feels like the landscape we happen to live in.
Then you learn about the Missoula Floods and realize a lot of this place was shaped by repeated Ice Age mega floods that tore through the region with enough force to rearrange the map.
Very casual.
In this episode of Maxwell’s Kitchen, I talk with geologist Scott Burns about the Missoula Floods, Glacial Lake Missoula, J Harlen Bretz, the Channel Scablands, Portland geology, ice-rafted boulders, the Willamette Meteorite, Ice Age animals, wine terroir, climate change, and how to read the landscape around us.
Scott is Professor Emeritus of Geology at Portland State University and co-author of Cataclysms on the Columbia: The Great Missoula Floods. Ooligan Press describes the book as the story of the prehistoric floods that shaped the Pacific Northwest and the scientific research that challenged early 20th-century geology.
In This Episode
The Missoula Floods and Ice Age Floods
Glacial Lake Missoula
How an ice dam created repeated mega floods
J Harlen Bretz and the Channel Scablands
How the floods shaped Oregon and Washington
The Columbia River Gorge and The Dalles
Portland, Lake Oswego, and the Willamette Valley
Ice-rafted boulders and the Willamette Meteorite
Mastodons, mammoths, saber-toothed cats, and giant beavers
Mount Hood, Mount St. Helens, and volcanic history
Radiocarbon dating and radiometric dating
Geology, soil, grapes, and wine terroir
Climate change, glaciers, sea level rise, and nuclear power
Guest
Scott Burns
Professor Emeritus of Geology
Scott Burns is Professor Emeritus of Geology at Portland State University. His areas of expertise include landslides, earthquakes, floods, volcanoes, radon, tsunamis, national parks, and the relationship between soils, climate, grapes, and wine.
He is also co-author of Cataclysms on the Columbia: The Great Missoula Floods, with John Eliot Allen and Marjorie Burns.
About the Missoula Floods
The Missoula Floods are one of those stories that sound fake until a geologist starts pointing at the land and explaining what you are actually looking at.
During the Ice Age, an enormous ice dam blocked the Clark Fork River and created Glacial Lake Missoula in western Montana. When that ice dam failed, the water rushed across the Pacific Northwest, through Eastern Washington, into the Columbia River Gorge, through the Portland area, and down into the Willamette Valley.
Then the dam reformed.
Then it failed again.
Then it happened again.
And again.
Scott explains that researchers now understand this was not one flood, but a repeated series of catastrophic Ice Age floods. In the episode, he talks about evidence for around 40 floods reaching Portland and Walla Walla, and more reaching the Spokane area.
That is hard to wrap your brain around.
One flood would already be insane.
Dozens of them starts to feel like the Earth was just aggressively renovating.
How the Floods Changed Geology
One of the best parts of this story is the scientific fight behind it.
J Harlen Bretz looked at the Channel Scablands in Eastern Washington and argued that the landscape had been carved by catastrophic flooding. At the time, that went against the dominant thinking in geology, which held that landscapes were mostly shaped slowly over long periods of time.
Bretz was mocked, challenged, and pushed back on.
Then the evidence kept piling up.
Eventually, other researchers connected his work to Glacial Lake Missoula, giant ripple marks, flood deposits, and other clues across the region. The story became one of the classic examples of science slowly changing its mind because the evidence would not go away.
Which is how science is supposed to work.
Annoying when you are the person everyone thinks is wrong for a few decades, but still.
The Columbia River Gorge, The Dalles, and Portland
This episode was especially interesting for me because I grew up in The Dalles.
When Scott starts talking about the Columbia River Gorge, the cut banks, the exposed basalt, the silt, the erosional lines, and the way the floodwaters moved through the region, it starts connecting to places I actually know.
That is the fun part of geology.
You are not just learning abstract facts. You are learning how to look at familiar places differently.
Scott explains how the floodwaters came through the Gorge, hit the Portland area, moved through Lake Oswego, filled the Tualatin Basin, pushed into the Willamette Valley, and then drained back out toward the ocean.
So when you drive through the Gorge and look at the land, you are not just looking at a pretty view.
You are looking at evidence.
Ice-Rafted Boulders and the Willamette Meteorite
One of the stranger parts of the Missoula Floods story is the ice-rafted boulders.
As the ice dam broke apart, chunks of ice carried rocks along with the floodwaters. Those floating ice chunks moved through the region, then melted and dropped boulders far from where they started.
That includes the Willamette Meteorite.
Scott explains that the meteorite was carried by ice and floodwater before being deposited near what is now West Linn. It is the largest meteorite ever found in the United States, and it is now at the American Museum of Natural History in New York.
That is a ridiculous journey for a rock.
Space, Earth, ice, flood, Oregon, museum.
Honestly, good for the rock.
Fossils, Mastodons, and Giant Beavers
The floods also connect to Ice Age animals in Oregon.
Scott talks about mastodons, mammoths, saber-toothed cats, giant ground sloths, and giant beavers. Tualatin is especially important because a mastodon was found there, and Scott talks about the future Ice Age Floods Visitor Center planned for the area.
He also explains why geologists look for fossils and flood evidence in depositional environments instead of erosional ones.
That sounds technical, but the simple version is this:
Do not look where the flood ripped everything away.
Look where the flood dropped things.
That is where the story is buried.
Dating Rocks, Floods, and Fossils
We also get into dating methods, because apparently you cannot just point at a rock and say, “old.”
Rude.
Scott explains radiocarbon dating, radiometric dating, uranium-thorium dating, volcanic ash layers, and how geologists use surrounding rocks and deposits to understand when something happened.
The useful takeaway is that different materials require different dating methods. Wood, bone, ash, volcanic rock, sediment, and minerals all tell time differently.
Geology is basically detective work, except the crime scene is 15,000 years old and the suspects are water, ice, volcanoes, and time.
Wine, Soil, and Terroir
The conversation eventually turns to wine, which makes sense because Scott has studied the relationship between geology, soils, grapes, and climate for decades.
He explains how the Missoula Floods helped create the fertile Willamette Valley soils that are great for crops like grass seed and hazelnuts, while many Willamette Valley vineyards grow above the flood sediments on older, redder, lower-nutrient soils that stress the grapes in a useful way.
In Washington, the situation is different. Many vineyards grow on flood sediments or windblown silt, and growers use irrigation to control the vines.
Same floods.
Different soils.
Different wine.
I like when science ends in wine.
Climate Change, Glaciers, and the Future
Toward the end, we talk about modern climate change, melting glaciers, sea level rise, changing wine regions, and whether a Missoula Flood-scale event could happen again.
Scott explains that the biggest known floods are tied to ice dams and advancing glaciers. Today, the larger concern is not the same kind of ice dam failure in our region. It is warming, melting glaciers, sea level rise, changing growing regions, and the long-term effects of burning fossil fuels.
We also get into nuclear power, spent fuel, and whether humans can still turn things around.
Light ending.
Just ancient mega floods, climate change, and the future of civilization.
Normal podcast behavior.
Quick Takeaways
The Missoula Floods were repeated Ice Age mega floods, not just one flood.
Glacial Lake Missoula formed when an ice dam blocked the Clark Fork River.
When the dam failed, floodwaters tore across the Pacific Northwest.
The floods helped shape Eastern Washington, the Columbia River Gorge, Portland, Lake Oswego, and the Willamette Valley.
J Harlen Bretz was criticized before the evidence proved the flood story.
Ice-rafted boulders were carried by floating ice and dropped as floodwaters receded.
The Willamette Meteorite is part of this flood story.
Oregon’s Ice Age landscape included mastodons, mammoths, saber-toothed cats, giant ground sloths, and possibly giant beavers.
Geology is about learning how to read the landscape.
The Missoula Floods also connect to soil, agriculture, grapes, and wine in Oregon and Washington.
Climate change is already affecting glaciers, sea level, and wine regions.
The land has been telling this story the whole time. We just had to learn how to read it.
