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1 July 2022
A quick Friday fold that I observed last month in a boulder of riprap at Chippokes State Park in Surry, Virginia. I have absolutely no idea where this rock was quarried; but it doesn’t look like anything I’m familiar with in Virginia, so maybe the Baltimore Mafic Complex??? Anyhow, it’s not native to the Coastal Plain, but it shows a pleasing fold train of green and gray amid the black …
24 July 2020
Exploring his new digs in Charlottesville, Callan is introduced to a large exposure of phyllite at a dam’s spillway. The foliation there is folded in many ways. Share in a dozen field photos of the site…
7 December 2018
A summary of resources to learn about the geology of Washington, D.C. and the surrounding region, in anticipation of AGU’s Fall Meeting being held in the nation’s capital city.
9 November 2018
Reader and former student Paxton DeBusk shared this lovely folded gneiss with me at the conclusion of the Virginia Geological Field Conference a few weeks ago: That’s a lovely hand sample, with a high folding:volume ratio! Happy Friday, all
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 …
21 September 2018
It’s Friday! Here’s a lovely sight, contributed by reader Fred Atwood: [youtube_agu id=Au-jIGfbs8g] Those are quartz veins in one of my favorite local rock units, the Mather Gorge Formation. Fred reports, This is at Madeira School in Great Falls between Black Pond and the Potomac. The rocks around Great Falls, particularly those on the Billy Goat Trail’s “A” Loop, are exemplary in many regards. That’s why I am taking my …
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.
24 May 2016
Alethopteris fern fossil: [gigapan id=”187190″] Link GIGAmacro by Robin Rohrback Rapid River Canyon, Idaho: [gigapan id=”187535″] Link GigaPan by Callan Bentley River cobble of brecciated Columbia River Basalt, Hammer Creek (Salmon River), Idaho: [gigapan id=”187524″] Link GIGAmacro by Callan Bentley Petersburg Granite exposed at Belle Isle, Richmond, Virginia: [gigapan id=”187523″] Link GigaPan by Jeffrey Rollins Ammonite: [gigapan id=”187221″] Link GIGAmacro by Callan Bentley Slickensides in ultramafic rocks of the Wallowa …
3 August 2015
As part of my work on the GEODE project, I’m always looking for good imagery to teach key concepts in geoscience. One important concept that I’ve been thinking about lately is the principle of relative dating on the basis of inclusions. Just as you can’t bake a loaf of raisin bread without already having raisins in your kitchen, rock units that are included in another rock unit must be older …
30 April 2013
Following on yesterday’s post about the kink bands within the strained metagraywacke of the Laurel Formation in DC, let’s take the opportunity today to go to Klingle Valley, site of a different facies within the Laurel Formation: a strained metaconglomerate. Though the exposure isn’t as great as the Purgatory Conglomerate, I think you’ll find plenty to hold your attention in these rocks. Close looks will reveal sericite-after-staurolite pseudomorphs (evidence of …
10 November 2012
My students Chris Johnson and Robin Rohrback have been busy adding to the Mid-Atlantic Geo-Image Collection. Check out a few of these new GigaPan images: [gigapan id=”117788″] link [gigapan id=”117786″] link [gigapan id=”117390″] link [gigapan id=”117346″] link [gigapan id=”116919″] link
8 November 2012
Check out these lovely images (mouth-watering, even) of the protomylonitic and mylonitic Walker Top Granite of North Carolina’s Inner Piedmont. There’s also some views of the field trip participants and scenery.
10 May 2011
Yesterday afternoon, I spent some time in the field with a colleague, a student, and a gigapan. I took four gigapan images, which are of varying quality due to the partly cloudy day, but still you ought to find them interesting to explore. You can see any of them full-screen by clicking on the word “GigaPan” in the lower right corner: Antiform in Mather Gorge Formation, C&O Canal: [gigapan id=”77023″] …