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2 December 2022
Friday fold: Hidden Rock Park, Goochland County
Two weeks ago was the annual Virginia Geological Field Conference, which was centered this year on the Goochland Terrane, an interesting block of crust in the Piedmont which shows some similarities to the Blue Ridge geologic province, but also shows some differences that suggest it’s not just a mini-Blue-Ridge. One of the best exposures was in Hidden Rock Park, where a series of “whaleback” outcrops expose things like this: There, …
16 September 2022
Friday fold: isoclinal limestone near Harrisonburg
This weekend, my family and I traveled to a little agrotainment complex north of Harrisonburg, Virginia, a joint called Back Home On The Farm. It featured a corn maze, hayrides, petting zoo, apple cider donuts, and pumpkin picking. All typical fall frolic; good clean fun. But there were also big blocks of limestone everywhere on the property. I did my best to check them all out. I was mainly scanning …
18 August 2022
Quarrying soapstone
Earlier this summer, I was lucky enough to visit a soapstone quarrying operation in Schuyler, Virginia, right on the Albemarle/Nelson County line. These soapstone bodies are metamorphosed ultramafic intrusions into the Neoproterozoic sedimentary deposits of the Lynchburg Group. The protolith peridotite sill crystallized at ~580 Ma, meaning the host sediments are older than that (but younger than the Grenvillian basement complex that underlies both). Then both plutonic rock and sedimentary …
24 June 2022
Friday fold: Kinked Lynchburg metasediments near a soapstone body
Happy Friday! Here are some kink-folded metasediments from Virginia’s Lynchburg Group to help usher in the weekend.
6 November 2021
Revisiting Tinker Creek
While my son takes banjo lessons downtown, I stroll Charlottesville’s walking mall and browse the bookstores. Last week, I dropped $40 at one of the used-book stores, walking away with an armful of volumes. Most were intended for my son (a voracious reader in addition to being banjo-philic), but on the shelf I also saw a trade paperback copy of Pilgrim at Tinker Creek, by Annie Dillard (1974), a book …
25 June 2021
Friday fold: The Blue Ridge Tunnel
Inside the Blue Ridge (in an 1850s-era railroad tunnel), Callan finds folds and boudinage that formed during Appalachian mountain-building.
7 May 2021
Friday fold: Lynchburg Group
On his way to get his COVID vaccine, Callan visits a new outcrop showing folded and faulted strata of the Neoproterozoic Lynchburg Group.
20 January 2021
Peering through
When hiking recently in my neighborhood, I saw this gleaming apparition appear in an eroded gully in a dirt road: Those multicolored stripes are varying compositions in a zone of ultramylonite: ductilely-sheared-out rock that formed in the deep equivalent of a “fault” in the Blue Ridge basement complex. We call it a “shear zone” most of the time, but a better descriptor would be “high strain zone.” These rocks are …
31 July 2020
Friday fold: Two Mile Run Overlook
I spied an anticline last weekend while engaging in a day of solo geologizing along Skyline Drive in Shenandoah National Park. At Two Mile Run Overlook, I gazed west toward the southern tip of Massanutten Mountain, and noted what appeared to be an anticline in the Blue Ridge foothills: Annotated: And here it is in Google Maps, with the perspective rotated to looking ~along strike to the north, and I …
24 July 2020
Friday fold: Totier Creek phyllite
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…
22 March 2019
Friday fauxld: concentric weathering rinds
Here’s a deceptive Friday “faux”ld I saw last week on the South Page Valley Road whilst learning about the Martinsburg Formation outcrops there: Looks like an isoclinal fold in this slab of siltstone, but the curvy lines are just concentric weathering rinds. Not a real fold at all! I hope everything you see this weekend is more straightforward and less deceiving. Happy Friday!
20 March 2019
The Dinosaur Artist, by Paige Williams
A book review of Paige Williams’ “The Dinosaur Artist,” a tale of international trade in dinosaur skeletons.
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!
1 January 2019
2018 Yard List
New year’s day is the time I tally up and report the bird species seen in my yard on the forested slope of Massanutten Mountain in Shenandoah County, Virginia. This is my seventh such annual list. Here are the previous iterations: 2012 (39 species) 2013 (51 species) 2014 (58 species) 2015 (65 species) 2016 (59 species) 2017 (56 species) It’s been a good year. Two new “seen for the first …
9 November 2018
Friday fold: gneiss from the Southside Virginia Piedmont
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
21 September 2018
Friday fold: quartz veins in metagraywacke of the Mather Gorge Formation
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 August 2018
Beautiful Swimmers, by William Warner
The subtitle of this wonderful book is “Watermen, Crabs, and the Chesapeake Bay.” It’s an excellent account of crab ecology in the Chesapeake Bay as it stood in the mid-1970s, and simultaneously a sympathetic portrait of the lives of the locals who capture those crabs for sale to the seafood market. The writing is thoughtful and calm, paced very similarly to John McPhee’s writing, rich in quotes from the watermen …
22 August 2018
Q&A, episode 5
A reader asks: “What is foliation and what makes it so important to the structure of rock?”
Callan answers with a lot of images of beautifully foliated rocks.
17 August 2018
Friday folds: Moomaw Reservoir outcrops
Break out your paddle and sunhat. We’re going kayaking on Lake Moomaw, in search of Friday folds…
