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5 June 2020
Reader Christian Gronau writes with this Friday fold contribution: Greetings from Cortes Island, BC – at the opposite end of the Strait vis-a-vis Lopez Island. Your Mountain Beltway blog is always of interest, and I have been following it for several years by now. Thank you for putting the effort into this worthwhile website. Quite regularly your posts elicit “echoes” and make me go back to some of my own …
29 May 2020
The Friday fold shows some sheared quartz-filled tension gashes in sandstones of one of the San Juan Islands in Puget Sound.
8 May 2020
Eric Fulmer (who pitched in with last week’s Friday fold) returns this week with another treasure. He writes, I was in Hopeville, WV a couple of years ago. The entire area between Cabins and Hopeville is a real joy (geologically and recreationally) as some of the most resistant rocks of the Mid-Atlantic Appalachians are folded and exposed in quick succession and with great relief. I am particularly fond of seeing …
27 March 2020
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.
31 January 2020
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 …
11 July 2019
Traveling in Newfoundland, Callan visits a seaside outcrop showing a Proterozoic submarine slump complex, overprinted by tectonic cleavage and weathered by the sea.
3 May 2019
When a dike is subjected to shear, how does it deform? A guest Friday fold from Darrel Cowan of the University of Washington teaches a nice little lesson. Join the field trip in Monarch Canyon of Death Valley National Park…
25 January 2019
Four Friday folds from Marli Miller’s online photo archive of geological images.
18 January 2019
Scott White (@SeafloorScott) of the University of South Carolina pitched in with today’s Friday fold: Click to enlarge This shows a section of high grade gneiss in the spillway of the Saluda Dam in Columbia, South Carolina. Zooming in there, you can see a nice fold hinge on the left edge: Although I don’t know the precise location of this outcrop, I did a bit of internet sleuthing… According to …
21 November 2018
Today, we take a look at the structural geology that reveals the deformation evolution (first ductile, then brittle) of the South Mountains metamorphic core complex, south of Phoenix, Arizona. Expect lots of photos of smeared-out rocks, broken by faults.