Compton Peak columns
Callan and three students visit a world-class outcrop of columnar jointing in Shenandoah National Park.
Callan and three students visit a world-class outcrop of columnar jointing in Shenandoah National Park.
After my talk Wednesday night to the Potomac Appalachian Trail Club, I got an email from PATC member Tom Johnson, with an extraordinary photo attached. It shows an exceptional outcrop of the Neoproterozoic Catoctin Formation, exposed atop Compton Peak in northern Shenandoah National Park, Virginia. The outcrop features enormous, well-preserved cooling columns from these ancient … Read more
The geology program at the College of William & Mary turned 50 years old this year, and last weekend they held a party to celebrate. Of the 800 or so geology majors the department has produced in 50 years, about 100 came to this event – that’s a pretty great ratio, I think: 1 out … Read more
Elizabeth Eide of the National Academies shared this image with me a year or two ago, when she gave a talk on Norwegian geology for the Geological Society of Washington. Those are some bookshelfed gneiss layers sandwiched between upper-left and lower-right carbonates. The “bookshelfing” refers to the numerous parallel brittle fractures along which the gneiss … Read more
Northern Colorado’s route 287 connects Fort Collins, Colorado with Laramie, Wyoming. Along its length, it displays roadcuts into Archean-aged basement complex. Two of these outcrops are featured in this post: one metamorphic (mostly), and a second igneous (mostly), with some intriguing polka-dotted plutons.
At the Burgess Shale this summer, it wasn’t all fun and fossils. I also saw a lovely, distinctly feather-shaped plume: This is an example of plumose structure – the subtle branching micro-topography that forms on the surface of a joint as the fracture propagates out from its origin. The more obvious “rib” that is perpendicular … Read more
Spotted this one Monday on the newly-rerouted section of the Billy Goat Trail’s Loop A, in Chesapeake and Ohio Canal National Historical Park. This graded bed was deposited as a turbidite in the Iapetus Ocean, sometime in the time-frame of 700 to 460 million years ago. It was metamorphosed 460 Ma during the late Ordovician … Read more
This morning, Dana asks about the pattern of columns in this image: She muses: If I had a time machine and surviving-fresh-lava gear, I’d head back to see what this bugger was up to. Why did some of its columns form ramrod-straight whilst others are practically horizontal, or curved? I’d imagine it was contending with … Read more
Callan shares a geological analogue that developed in his house yesterday: en echelon tension fractures, common in sheared rocks, appeared on his ceiling due to the Mineral, Virginia earthquake.
Dave Lageson of Montana State University and I ran into each on our respective field trips sometime last year outside of the Two Medicine Dinosaur Center in Bynum, Montana, and he told me that I had to go check out the Swift Dam area, a little ways northwest of the town of Depuyer. So, a … Read more