Lower Columbia Chapter

Temporary Lake Allison Was 400+ Feet Deep Over Portland

Floods Filled the Portland Basin

When the Ice Age Floods roared into the Portland Basin they deposited gravel bars and scoured around topographic highs like the ‘Boring’ volcanoes (Powell Butte, etc.) and the Portland Hills. As they flowed on toward the ocean they were obstructed downstream at Kalama Narrows, which caused the flood waters to back up in temporary Lake Allison that filled the Willamette Valley up to ~400 feet deep all the way south to Eugene.

In the quieter areas of Lake Allison the sediment-laden waters deposited large volumes of rich Palouse soils that were stripped from upstream areas of central Washington and now support vibrant agriculture throughout the Willamette Valley. But as the muddy waters rushed into and later back out of narrow passages they scoured out depressions that are now filled by peaceful lakes like Lake Oswego. 

Many icebergs floating in the flood waters became stranded on the edges of Lake Allison as the flood waters receded, where they melted and deposited exotic ‘erratic’ rocks embedded in them (even a meteorite) that were carried from the ice sheet far to the north.

Lower Columbia Chapter

IAFI’s Lower Columbia Chapter serves the Willamette Valley and lower Columbia River

The Lower Columbia Chapter hosts lectures on the third Thursday of each month except in August and December when we do not meet. Before (and after?) the pandemic, Meetings are held at the Tualatin Heritage Center, 8700 SW Sweek Drive, Tualatin, Oregon 97062, except the September meeting which is held at the Tualatin Library.

Since the pandemic we’ve held the meetings via Zoom. In 2020 we started recording our Zoom lectures and uploading them to the IAFI YouTube channel. If you can’t make it to a lecture, we generally have the video uploaded to YouTube in the next week. We invite you to visit our channel and browse the videos there!

Chapter News – KGW TV in Portland recently carried a story on it’s “Grant’s Getaways” show entitled “Oregon’s Erratic Rocks.” The segment features Rick Thompson of the Lower Columbia chapter and looks at how erratic rocks found in the Willamette Valley are remnants of the Lake Missoula floods. Click here to view the video segment.

Please see the Upcoming Events or the General Events Calendar for a listing of all chapter meetings and events.

President
Charles Hall

Vice President
Gerry Tunstall

Secretary
Jane Walpole

Charles Hall

Treasurer
Charles Hall

Technical Expert
Dr.Scott Burns

Lower Columbia Chapter – Ice Age Floods Institute
PO Box 25658, Portland, OR 97298
Email: LowerColumbia@IAFI.org

Lower Columbia Chapter​
Lower Columbia Chapter News

Lower Columbia Chapter News

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March 2024
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Ellensburg, WA 98926 United States
Apr 12

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