Had this brainstorm a few weeks back (or maybe months?). Been meaning to blog it up, but hadn’t gotten the chance to flesh it out. The geologic map of the Commonwealth comes from Chuck Bailey of William & Mary, who gave me permission to use it for this project. Anyhow – do you think there … Read more
Callan and three students visit a world-class outcrop of columnar jointing in Shenandoah National Park.
Callan visits a new outcrop of highly-sheared rocks in the basement complex of Virginia’s Blue Ridge province.
I saw this boulder lining a garden this past weekend down in Nellysford, Virginia, in the scenic valley of the Rockfish River draining the eastern slope of the Blue Ridge. It’s a piece of the Neoproterozoic-aged Catoctin Formation, a series of lava flows and associated rocks that erupted on the breakup of the early supercontinent … Read more
Today, I share with you eight images that I took yesterday on Skyline Drive in Shenandoah National Park: Blocks of Antietam Formation quartzite (meta-quartz sandstone) of Cambrian age, used in the low rock walls of an overlook parking pull-out. They all bear lovely Skolithos trace fossils (seen end-on, and in cross-section):
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
Some fall photographs from 2007, taken of the south fork of the Shenandoah River, southeast of Massanutten Mountain, in Virginia’s Valley & Ridge province. Photos are by my NOVA colleague, the biologist (and pilot) Mike Peglar: Our leaves are changing color now, and I’d imagine if we were soaring over the Shenandoah Valley this morning, … Read more
Last spring, I made two visits, six days apart, to Veach Gap, a small water gap superimposed on the Massanutten Synclinorium. One was with my Field Studies in Geology one-day field course, and the second was with my Structural Geology students from George Mason University. We go there to see some lovely parasitic anticlines that … Read more
By local prodigy Hannah Holland, elementary school student: Click through to make it bigger and see some details. Nice work, Hannah! Very impressive, and thanks for sharing!
Hurricane Irene passed this way two weeks ago, and dumped a lot of rain on the mid-Atlantic region and the northeast. As a result, runoff increased, rivers swelled, and sediment was mobilized. Some of that sediment was suspended and transported downstream. On Tuesday, I got this e-mail from my colleague Ken Rasmussen, who took students … Read more
These are all in the northern stairwell between the 2nd and 3rd floors of the Godwin Building here on the Annandale campus of NOVA. The cement blocks have clearly separated along their mortared edges, and the disruption of the paint layer in a series of en echelon fractures reveals that deeper structural issue. I find … Read more
A up-to-date tally of the aftershocks from the Mineral, Virginia earthquake is presented as a time vs. magnitude plot.
The USGS reports more aftershocks, so your humble graphing servant has responded with a plot that updates the images I showed you last week. Here you go: Embiggable, via a simple click. Again, the “decay” pattern jumps out at us. One thing that I’m also noticing is how there are no events below 2.0 magnitude. … Read more
So last Tuesday we had an earthquake, and we expected some aftershocks as the crust in the Mineral, Virginia, area adjusted to the new stress regime. We expected those aftershocks to be lesser in magnitude, and to take place after the main shock. In other words, we would predict the following: And, indeed, over the … Read more
Callan describes his experience with the widely-felt east coast earthquake of August 23, and provides an analysis of the fault(s) that may be reponsible.
Another thing I saw last week in the Rockfish Conglomerate were several nice examples of “bookshelfing,” which is when a rock or mineral fractures into pieces, and the pieces slide down relative to their neighbors, like a set of encyclopedias slumping outward on a bookshelf. This has the effect of shortening the grain/clast in one … Read more
Callan presents a gazillion photos from a field trip to examine the Rockfish Conglomerate, a potential Snowball Earth glacial outwash facies from the Neoproterozoic of the Virginia Blue Ridge province.
The current edition of the Accretionary Wedge geology blog carnival (hosted by Evelyn Mervine of Georneys) is built around the theme of favorite geology words. My favorite geology word is derived from the French boudin, for sausage. It’s “boudinage,” and it’s best said with a heavy French accent and a leering, dirty expression. “Boo-din-ahhdj” I … Read more
This Friday, I give you a fold from the shores of the Rockfish River, south of Charlottesville, in Virginia’s Blue Ridge basement complex, and just down the road from the Lawhorne Mill High Strain Zone. The fold distorts (and improves) a felsic dike cutting the darker granite of the basement. You can make this (stitched … Read more