Purcell Trench, Northern Idaho
N 47° 44.356 W 117° 02.010
11T E 497488 N 5287322
This wayside has a sign provided by the Idaho State Historical Society that explains the Purcell Trench.
Waymark Code: WM9XBT
Location: Idaho, United States
Date Posted: 10/10/2010
Views: 13
The sign reads:
"Purcell Trench
A long, glaciated valley, extending from British Columbia this far into Idaho, brought part of a Contenental ice sheet past here thousands of years ago. Rocks and boulders transported here by glacial ice backed up Lake Coeur d'Alene. Then a gradually warming climate let an outlet from Lake Pend d' Oreille discharge past here-sometimes with catastrophic results. As ice receded, Kootnai River also flowed past here before lower channels in British Columbia no longer were blocked by a glacial barrier. In those days, this was Columbia River's main channel.
Sign #256
For additional information about the heritage of Idaho, access the Idaho State Historical Society Website at www.idahohistory.net"
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There is also a great deal of information about the Purcell Trench and how it is associated with the Missoula flood, at this website: (
visit link)