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27 March 2020

Friday fauxld: a false syncline in Titus Canyon

What day is it again? Hard to keep track in the days of raging coronavirus infections, but it is in fact Friday, which means that if you want a dose of the halcyon pre-COVID-19 days, you can enjoy this example of a false fold from Death Valley National Park’s Titus Canyon.

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20 March 2020

Friday fold: more folds from lower Titus Canyon

We are living in surreal times. It hardly seems possible, but a week ago this evening, I drove down the Las Vegas strip with my students, ogling at the glitz and spectacle and crowds. Now, a mere 7 days later, Vegas has been shuttered, and it’s been shuttered for days. We traveled freely through California and now a week later, everyone in the state is ordered to stay home. What …

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13 March 2020

Friday fold: Bizarro folding in Titus Canyon

Hi everyone, and greetings from eastern California’s Death Valley, where I’m leading a field geology course over our spring break. I found an excellent Friday fold for you: That’s the Cambrian-aged Bonanza King Formation, a package of limestones, as exposed in lower Titus Canyon, Death Valley National Park. Here’s the thing: the lower part of that outcrop is Upper Bonanza King Formation, while the upper part of the cliff is …

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6 March 2020

Friday fold: an Extreme(adura) geological history question

The Friday folds are revealed in an elegant cross-section through fantastic rocks in the Extremadura region of Spain.

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28 February 2020

Friday fold: sandbox

The Friday fold is a lovely little sandbox analogue model by Prof. Marco Martins-Ferreira, who posted it on Twitter this week:  As deformation proceeds, you can see the layers develop folds that then morph into faults, shoving deeper layers atop more shallow strata. As a bonus, you can hear Marco’s baby cooing in the background! Here’s a stabilized, sped-up version, courtesy of Anna Williams:  Happy Friday, all!

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14 February 2020

Friday fold: Miocene slump in Anza-Borrego

Today’s Friday Fold comes from Edith Carolina Rojas, the dynamic geology professor at The College of The Desert in Palm Desert, California. She’s an awesome person, and also the sense of scale in this amazing image: Edith shares that this gorgeous structure is an anticline is located in Split Mountain Gorge in Fish Creek Canyon. It’s a gigantic gravity-slide fold due to soft sediment deformation in the Latrania Formation. Wow …

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7 February 2020

Friday fold: Kings Canyon

The Friday fold shows disharmonic crumpling in marbles of the Boyden Cave Root Pendant in California’s Sierra Nevada. The GigaPan image displayed is part of the digital legacy of Ron Schott, who passed away a year and a half ago.

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31 January 2020

Friday fold: tension gashes near Sunflower, Arizona

Reader John Christian shared these folds with me via email last week. They are quartz veins in slightly metamorphosed Precambrian igneous rocks found near Sunflower, AZ in the Mazatzal Mountains. The second photo is a close-up shot of the curviest, cleanest batch of folds from the first shot. These are beautiful examples of folds in similarly oriented quartz veins; we call them “en echelon” for the way you have a …

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24 January 2020

Friday fold: Pelham Parkway

A roadside boulder in the Bronx shows folded gneissic banding. It’s another guest-submitted Friday fold!

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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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