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27 March 2017

Cleaved, boudinaged, folded Edinburg Formation southwest of Lexington

Cleaved, boudinaged, folded Edinburg Formation southwest of Lexington

Explore a dozen photos highlighting the structural geology of an outcrop of limestone and shale near Lexington, Virginia. Cleavage refraction, overturned beds, boudinage, folds, and even a small fossil – we’ve got something for everyone. Bring the whole family!

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10 March 2017

Friday fold: Sheba Mine sample

Friday fold: Sheba Mine sample

When touring the geology of the Barberton Greenstone Belt last August, our group visited the Sheba Mine, a gold mine high in the hills. Their geologist kindly showed us around and allowed us to visit his history-laden office. I have no idea where this sample originated, but it was the only fold I saw in the place, nestled between sepia-toned photographs and old lanterns and rusty picks. I wonder what …

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3 March 2017

Friday fold: Kink folded Dalradian metasediments

Let’s reminisce back to the Walls Boundary Fault on the Ollaberry Peninsula of Shetland today. Here’s a 3D model to go along with the ones I posted last time: It’s a little ragged, but so am I at the end of the workweek! Happy Friday. Have fun spinning this thing.

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24 February 2017

Friday fold: 3D model of kinked schist from Rhode Island

Friday fold: 3D model of kinked schist from Rhode Island

For your Friday fold this week, I present to you a 3D model of a sample of kinked schist from Beavertail State Park, Rhode Island. Spin it right round, baby: This is another sample from the structural geology collection of Carol Simpson and Declan De Paor.

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17 February 2017

Friday fold: Buckled at Baltinglass

Friday fold: Buckled at Baltinglass

Garnetiferous beds from the aureole of the Leinster Granite east of Baltinglass, County Wicklow, Ireland (Declan De Paor’s senior thesis mapping area, 1973). Manganese-rich metasediments. The prominent ‘elasticas’ or fan folds (folds with a negative inter-limb angle) are superimposed on isoclinal folds: so the brownish layer at top and bottom are the same, though that is not obvious from the image. This is a sample from the structural geology collection …

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10 February 2017

Friday fold: the Grand Canyon

Friday fold: the Grand Canyon

Deep in the Grand Canyon of Arizona, Steve Mirsky found a Friday fold to share with you.

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6 February 2017

Q&A, episode 1

Q&A, episode 1

A new series takes science and nature questions and answers them. Read the answers to the first two questions and submit your own!

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3 February 2017

Friday fold: Squaw Creek Schist, Idaho

Friday fold: Squaw Creek Schist, Idaho

The edge of ancestral North America can be found in the canyon of the Salmon River in western Idaho. Folds exposed the Squaw Creek Schist near Riggins record the stresses of adding terranes on during North America’s westward movement since the breakup of Pangaea. The Friday fold crinkled up during the accretion of a terrane to the growing North American continent.

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2 February 2017

Banded iron formation in Barberton Mountain Land

Banded iron formation in Barberton Mountain Land

Banded iron formation is an “extinct rock” that can be found in ancient marine strata such as those found in the Barberton Greenstone Belt. Visit an outcrop on the Barberton GeoTrail and contemplate the bizarre anoxic world that Earth used to be.

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27 January 2017

Friday fold: the Bradshaw Layered Amphibolite

Friday fold: the Bradshaw Layered Amphibolite

The Friday fold can be found along the Fall Zone, where crystalline metaigneous rocks of the Piedmont meet the gently sloping strata of the Atlantic Coastal Plain. Contemplate their high metamorphic grade and their tight folding, and imagine the mighty mountains that once rose on this spot.

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