Thursday, March 20, 2014

Geo 730: March 20, Day 444: Around Virgin Valley

A final shot of the warm pool. A group that I believe calls itself "Friends of Virgin Valley" (I can't find any info about them on the net) has taken a fantastic role of maintenance and restoration here. From rebuilding and mortaring the shower house and wall around the pool, to clearing algae from the pond, installing the fence, sidewalk and benches, these good folks have used their own sweat and private donations to restore an installation that was on the verge of utterly falling apart in the late 80's.

I mentioned Thousand Creek Canyon in passing yesterday, and I want to spend some time on it simply because it doesn't seem to be a widely known feature that is quite spectacular in several ways. It's a narrow, vertically walled cut, mostly into very competent rhyolite similar to the outcrop to the west along 140 (See March 11- March 17). The sheerness of the walls combined with the narrowness of the gorge, flatness of the floor, it's more-or-less east/west orientation, and apparently year-round water flow (though very low at times), all work together to create a lush, cool, and verdant microclimate that one doesn't expect at all in the midst of this arid land. It's like a lawn, in places. Though Sharkey originally took us in to look at a contact between two rhyolite flows, I've long forgotten exactly where that spot is, or what made it notable. Normally when I've visited the spot with others, it's more out of ecological interest than geological. And sightseeing... it's utterly beautiful!

Getting into it is a bit problematic; the mouth is clogged with small willows, brush and beaver dams, and it's been different every time I've been there. There are pretty clearly occasional large flow events, which rearrange the entrance and deposit woody debris at surprising heights above the canyon floor- 15 to 20 feet. At any rate, the first bit is tangled and slow going, but keep pushing toward the north side of the canyon. There, turn into the canyon, and follow the rudimentary path. Once you reach the more vegetated areas, the path disappears and reappears as options to spread out are available or not. I know some people have pushed all the way through to the far end, but I'd guess I've been no more than a mile or so into it. It does get rugged. But it's an amazing thing to experience. In this FlashEarth view, you can see the entire canyon, with the downstream end of the canyon under the crosshairs, and a sweet bit of inverted topography at Railroad Butte. This is a spot where a basalt flow followed a drainage, making the infilled, lower area more resistant to subsequent erosion. This in turn caused the originally low area to remain high while the originally higher ground around it has eroded down- effectively inverting the topography.

Photo unmodified. August 19, 2011. FlashEarth Location.

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