Posted by: Anne Jefferson | June 22, 2010

Braided river meets mountain gorge: The Snake River escapes Jackson Hole

Though I don’t think anything can top Kyle’s pathologically misdirected RYNHO, I recently had cause to contemplate a river that everyone has heard of – the Snake River of the northwestern United States. Now, the Snake River has a famous gorge, a famous lava plain, and it’s had a famously big flood or two, but the upper reaches of the Snake are pretty scenic too. The Snake originates in Yellowstone National Park and flows through Grand Teton National Park and the Jackson Hole valley. Throughout the broad, flat valley, the Snake is beautifully braided (with some gorgeous terraces too).Then it runs into some mountains – the Wyoming Range – and it runs out of room to braid, becoming constricted into a narrow mountain gorge. Interestingly, after heading south from Yellowstone and through Jackson Hole, the river turns west through the mountains and then quite abruptly turns north towards Idaho’s Snake River Plain.

I’d love to know how and why the river started along this path and how intensely the river’s course is geologically controlled. I think the gorge is south of the Teton block, and it’s possible that it’s in an narrow zone that hasn’t seen as much uplift as other mountain blocks in the Basin and Range, but I’m just speculating here. If anyone has any good ideas or citations, please drop them in the comments.

The images below are from a mix of Flash Earth (permalink here) and Google Earth. The first is a large scale view of the braided-gorge transition, while the second and third are close-ups of typical braided and gorge reaches, respectively.

Posted via web from Pathological Geomorphology

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