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

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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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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13 December 2019

Friday fold: blueschist & eclogite at Jenner, California

A pre-Fall Meeting field trip to the coast of northern California yields rare sights of garnet-bearing blueschist, plus eclogite, some pillow basalts, birds, waves, wind, and a lot of rain.

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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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9 August 2019

Friday fold: crumpled green metavolcanics from St. Anthony

The Friday fold erupted out of a volcano, completing the second part of its two stage cooling history, then later got folded and metamorphosed. It was found atop a high cliff near the northern Newfoundland town of St. Anthony.

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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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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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6 February 2019

Dalradian schist at Glen Roy

We saw last week how glaciation carved out a valley in Scotland called Glen Roy. As the glacier ground into the landscape, it liberated tremendous numbers of sedimentary particles from the bedrock, which is composed of Dalradian metamorphic rocks (mainly porphyroblastic schist in my observation). Then once that now-U-shaped valley had been deglaciated, a new glacier dammed it, making a lake that rose and filled the declivity of Glen Roy, …

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2 November 2018

Friday fold: Refolded marble from Corsica

The Friday fold comes to us from Corsica via University of Washington structural geologist Darrel Cowan. It’s a marble that’s been folded *twice!*

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26 October 2018

Friday folds: Mather Gorge Formation

It’s been a very Billy-Goaty week for me. Three times since Sunday afternoon, I’ve taken people to the Billy Goat Trail’s “A” loop in C&O Canal National Historical Park. On Tuesday and Thursday, it was my NOVA Physical Geology students. On Sunday, though, it was just my son and me. Good news! He helped me discover a new fold by exploring some new rock outcrops and climbing on them. He …

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