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6 December 2019

Friday fold: a secret Santa rock exchange gift!

I participated this year in the Secret Santa Rock Exchange, wherein I shipped out a mystery rock to a random person, and got back a mystery rock from another random person. What fun! My mystery rock has folds in it! It’s from Matt Bruseke at Kansas State University. Check it out: Matt writes that this is a piece of the Silver City rhyolite, from the Owyhee Mountains, Idaho. The sample …

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31 August 2017

Geology Underfoot in Southern Idaho, by Shawn Willsey

I love the “Geology Underfoot” series published by Mountain Press – the same folks who have published dozens of titles under the “Roadside Geology” theme. “Underfoot” is better than “Roadside,” I think, because it tells the story of discrete places, suggesting ideal places to visit. Each chapter is self-contained and useful without extraneous details, and avoids the redundancy of many roads crossing through near-identical geology. The latest title in the …

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3 February 2017

Friday fold: Squaw Creek Schist, Idaho

The edge of ancestral North America can be found in the canyon of the Salmon River in western Idaho. Folds exposed the Squaw Creek Schist near Riggins record the stresses of adding terranes on during North America’s westward movement since the breakup of Pangaea. The Friday fold crinkled up during the accretion of a terrane to the growing North American continent.

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10 June 2016

Friday fold: Mesoscopic structures in the Lightning Creek Schist

There are some structural goodies here at the confluence of the Rapid River and the Salmon River in west-central Idaho. I visited these outcrops three weeks ago on a field trip after the Rocky Mountain section meeting of GSA. The rocks are the Lightning Creek Schist, a schist that’s part of the Wallowa Terrane, an accreted chunk of crust that docked with western North America during the Mesozoic. Here is …

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3 June 2016

Friday fold: Riggins, Idaho

There are some folds in this stunning west Idaho landscape. Perspective is looking toward the north, more or less. See if you can find them: Link GigaPan by Callan Bentley One example that will probably be obvious at first glance is this syncline/anticline pair, differentially weathered, with subvertical axial traces, and an apparently shallow plunge of the axes to the south: A more subtly expressed example is on the hill …

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2 June 2016

Flood deposits of Glacial Lake Missoula outburst floods

Two weeks ago, I went on an awesome, informal field trip to eastern Washington State to visit the Channeled Scablands for the first time. My collegue Bill Richards of North Idaho College picked me up in Spokane and drove me halfway across Washington and back to Moscow, Idaho, over the course of a day. This is a region of the country where a glacier-dammed valley filled up with water (Glacial …

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24 May 2016

Nine new GigaPans from Team M.A.G.I.C.

Alethopteris fern fossil: Link GIGAmacro by Robin Rohrback Rapid River Canyon, Idaho: Link GigaPan by Callan Bentley River cobble of brecciated Columbia River Basalt, Hammer Creek (Salmon River), Idaho: Link GIGAmacro by Callan Bentley Petersburg Granite exposed at Belle Isle, Richmond, Virginia: Link GigaPan by Jeffrey Rollins Ammonite: Link GIGAmacro by Callan Bentley Slickensides in ultramafic rocks of the Wallowa Terrane, just outboard of the paleo-Laurentian tectonic margin, Salmon River, …

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20 May 2016

Friday fold: core

At the Rocky Mountain Section meeting of the Geological Society of America this week, there were several displays of interesting cores. I’m not sure where this one came from, but it had a fold in it, and since no one else had volunteered a Friday fold for this week, I took a photo: It’s standard core diameter; I’d guess that’s about 2 inches. Given that I’m headed out on an …

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4 May 2012

Friday fold: ball & pillow in volcanic ash

Another guest Friday fold – this one supplied by Ander Sundell of the College of Western Idaho, and his student Katie Ursenbach, who took the shot and gave permission for me to re-post it here. You’re looking at cuspate-lobate folds due to primary sedimentary settling. the Snake River Canyon in southwestern Idaho. A pile of volcanic ash erupted into water in the Paleogene, and soon after covered by a series …

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