News Release

Rhyolite Erratic Floods Evidence

Rare Rhyolite Erratic found in Tualatin, Oregon

Image used by permission Rick Thompson (c)

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News Release Date: May 28, 2021

Ice Age Floods rafted a two-ton igneous rock not normally found in Oregon's Willamette Valley to Tualatin. It was discovered during excavation for the new Lakeridge Junior High School. The Rhyolite is mottled yellow, brown and greenish rock which likely came from the mountains of British Columbia, Canada or Montana.

This story was widely coverd in the press. Here are links to those articles:

Tualatin Life Newspaper https://tualatinlife.com/featured/rare-geological-find-is-headed-to-tualatin/

PSU Website Portland State professor identifies 15,000 year old boulder at site of new Lake Oswego middle school 
 



Last updated: September 24, 2025

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Program Manager
Ice Age Floods National Geologic Trail
1008 Crest Drive
Coulee Dam, WA 99116

Phone:

(509) 237-9722

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