Saturday, October 13, 2007

Watch the Vashon stage of the Cordillieran ice sheet engulfs Puget Sound, deepening the Strait of Juan de Fuca, and wrapping around the Olympic Mountains. So in fact the salmon have to have reestablished their relationship to the rivers of the Olympic Mountains sometime after about 13,000 or so years ago. How long did it take them to find their way back? A lot of time on our scale, but not a lot of time on the earth's scale.

I particularly like the time when the mountain glaciers have melted back creating lakes still dammed up by the big ice sheet, which hasn't retreated yet.

This graphic comes, with explanation, from the Olympic National Park website. The U. S. Geological Survey has a Geology of Olympic National Park website, which updates R. W. Tabor's book, Geology of Olympic National Park. University of Washington has a nice page of studies about the present-day Blue Glacier on Mount Olympus.

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