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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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22 November 2019

Friday fold: Noonday Dolomite in Mosaic Canyon

Because I’m putting together a field course for spring break 2020 to Death Valley California, I was looking through old Death Valley photos this week, from the last time I went to that special place. It was seven years ago! How time flies… This one is in Mosaic Canyon, and was taken by my student Marcelo Arispe, a talented photographer as well as a talented geologist: By the standards of …

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15 November 2019

Friday fold: two samples from Tennessee Tech

I spent some time in east central Tennessee last week, visiting the Earth Sciences department at Tennesee Technical University in their lovely newly-remodeled home on the main campus quad. In a hallway display case, they had many beautiful specimens on display to educate and inspire. Here are two lovely examples of folding. Terrific rocks to take us into a terrific weekend. Have a good one!

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8 November 2019

Friday fold: Rist Canyon cobble

From a creek bed in northern Colorado, the Friday fold distorts foliation in early Proterozoic quartzofeldspathic gneiss, peppered with small almandine garnets.  

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1 November 2019

Friday fold: Newfoundland beach cobble

This Friday’s fold is found in a metasedimentary beach cobble I found last summer in southeastern Newfoundland: A lovely little “pocket fold,” it came home with me and is among the handful of “deskcrops” I keep in my home office. Happy Friday and happy November!

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25 October 2019

Friday fold: Identity of a BIF

The Friday fold is a slab of banded iron formation now dwelling in the University of Washington’s Department of Earth & Space Sciences. But where did it come from? India? Brazil? Perhaps you can help identify its provenance.

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18 October 2019

Friday folds from the Foreknobs Formation

TGIF! That’s my seven year old field assistant showing off the shape of a syncline in shale, siltstone, and fine sandstone of the Foreknobs Formation, a Devonian nearshore package of clastic sediment in the Valley & Ridge Province of eastern West Virginia. Want to see something freaky for Halloween? Photoshop can make it happen: Ewwww. Creepy! Another shot of the same fold, with a thick massive sand above a thicker …

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