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You are browsing the archive for folds Archives - Mountain Beltway.

17 May 2019

Friday fold: Found folds

This week, for Friday folds, I offer up some random folds that have passed my perceptual transom this week. First up: In the new Netflix series Our Planet, in episode 7 (Fresh Water), an anticline/syncline pair makes a brief appearance as David Attenborough discusses glaciers as a reservoir for fresh water. Here is a screenshot: I’m not sure where this is in the world: Greenland? Antarctica? Let me know in …

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3 May 2019

Friday fold: Monarch Canyon

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…

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26 April 2019

Friday fold: Black Sands Beach

The Friday fold can be found in a boulder of gray chert layers on Black Sands Beach, at Marin Headlands in California.

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19 April 2019

Friday fold: Angel Island “III”

For the third Friday in a row, “Mountain Beltway” features folds from Angel Island, in northern San Francisco Bay, California, This time, it’s meta-cherts on Perles Beach, showing impressive metamorphic recrystallization reactions.

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12 April 2019

Friday fold: Angel Island “II”

Happy Friday, all. Here are a few shots of crinkled, thin, multicolored cherts from Kayak Beach on northern Angel Island, California, piggybacking on the folds I showed you last week.

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5 April 2019

Friday fold: Angel Island “I”

The Friday fold is on the north shore of Angel Island, San Francisco Bay, showing blueschist-facies high-contrast metalliferous cherts with folds on many scales.

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29 March 2019

Friday fold: Plunging Purisima

AGU’s Centennial year is also the 35th anniversary of the publication of Clyde Wahrhaftig’s unique field guide to the geology of San Francisco. A team of geologists is updating “A Streetcar to Subduction” for a modern digital audience, and recently did some California field work to visit key sites. Check out one of them here with the Friday fold, as we visit a plunging syncline in the Purisima Formation on the coast near San Mateo.

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18 March 2019

New discoveries in the Martinsburg Formation

A virtual field trip to examine some deepwater clastic sediments shed off the first phase of Appalachian mountain building, and deformed in the third phase. It’s a lovely day for a field trip to the late Ordovician!

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15 March 2019

Friday folds: two more from Oman and Chuck Bailey

Friday is that special day of the week where we take a break from our hurried lives and gaze longingly at great photos of folded rocks in exotic corners of the world. Today, we return to Oman, and we say, “Oh, man!”

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8 March 2019

Friday fold: Dent de Morcles

The Friday fold is a recumbent anticline/syncline pair, deforming the K/Pg boundary in the Swiss Alps, as photographed from the air by Bernhard Edmaier.

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