You are browsing the archive for metamorphism.
6 February 2019
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, …
2 November 2018
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!*
26 October 2018
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 …
22 June 2018
Another guest Friday fold (keep ’em coming, folks!) – This time from Eric Pyle of James Madison University: This is a weathered outcrop of the Connemara Marble in western Ireland, about a meter wide. Thanks for sharing, Eric!
18 May 2018
The Friday fold takes us to the French Mediterranean island of Corsica. Are you ready to dip into the blueschist facies in search of sheath folds?
13 April 2018
The Friday fold is on display in a rock garden outside the Department of Earth and Environmental Sciences at the University of Kentucky.
18 October 2017
The 2017 Virginia Geological Field Conference had a heavy arkose infusion. Meet some of these feldspar-rich Neoproterozoic sediments of the Lynchburg Group.
24 February 2017
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.
17 February 2017
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 …
27 January 2017
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.