Landscape reveals clues of area’s past

Continental lands keep shifting even in the present day

I remember being impressed at the idea of our continent being slowly built by bits and pieces of continents being added to it.

The idea of continents moving at all greatly shook up establishment of the day, but ultimately the evidence came in and had to be accepted.

Why do they start with the Idaho line as the former west edge of North America? Possibly because what I read was about the Pacific Northwest. The idea ultimately was accepted: Our state is a patchwork of bits and pieces of other continents, being slowly built as one moving bit after another was added to what was already here.

North America, some writers say, is moving west at the rate of about an inch a year. Parts of it, the Cascade Mountains, for instance, are moving upward from one to three inches a year.

We can tell that advancing scientific theories are being accepted when they make The National Geographic, as this one did a few years ago. Some nice sketches of the relative positions of continents and their component parts were laid out.

Tantalizingly, there was reference to this being not the first time this had happened, but those earlier positions thus far have not been established. Geology, we have been told repeatedly, tends

to erase earlier positions of things as they make new ones.

So there came, first, the section that holds the eastern west states, followed by the Okanogan Highlands, which left the western edge of the continent at what is now the Okanogan Highlands.

Included in this latest addition were two huge bodies of molten rock, the Kettle Dome and the Okanogan Dome, the latter making the new edge of the continent.

Later addition of the Cascades, says one source, arrived with spouting volcanoes in place. The range sutured itself to the continent, leaving the river which we call the Okanogan as a memory of the day when larger waters edged the country.

Rock on the two sides of the suture are totally different. If we can jump for a moment from the gargantuan scale of colliding continents to humans, the story is told that a woman and her husband, prospecting for homestead land, went from creek to creek, she with a bar of soap in her hand.

When she got a nice lather in soft water, she decided which place they would stay. If that delightful bit ever included her name, I haven’t heard it.

If we can return to the larger scale, we are back to the Okanogan Highlands, running north up the older side of the valley. Between the Okanogan and Kettle domes ran a line of volcanoes, which erupted until they had emptied their reservoirs of lava and then collapsed upon themselves.

Drive the San Poil road in a sharp summer rainstorm and there will be baby waterfalls all up and down the valley, briefly.

But that’s not the last word. The rock in the western exposure of the Okanogan Dome is currently identified as mylonite, according to “Northwest Exposures,” by Alt and Hydman.

They say: “Mylonite, a type of metamorphic (altered) rock that crystallizes within a moving fault zone deep enough that the rock flows instead of breaking.”

For years I misidentified it as gneiss (pronounced nice). There are beautiful exposures of it all up and down the Okanogan Valley, and in many other places up and down the Okanogan.

Hard, crystalline (contains thulite) and beautiful, it once edged the continent. Now, other rocks get the placement.

But that is another story.

Elizabeth Widel is a columnist for

The Chronicle. This is the 2,847th column in a series. She may be reached at 509-826-1110.

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