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26 May 2011
Fault in Massanutten Sandstone
Here’s a gigapan I shot last yesterday, looking west from “Blue Hole” towards a cliff of Massanutten Formation sandstone, south of Waterlick, Virginia. A prominent fault zone can be seen in the center of the image. Unfortunately, the auto-stitch deformed my face. I look like Quasimodo. Oh well. As usual, you can see it full screen, by clicking on the word “Gigapan” in the lower right. There, you can find …
23 May 2011
A tidy little quartz crystal
A doubly-terminated quartz crystal (or “Herkimer diamond”) is found on a hike in the Silurian sandstones of Virginia’s Valley & Ridge province.
12 May 2011
Deformational fabrics in the Weverton Formation
My student Troy was working on the geologic history of the Thoroughfare Gap regions for his Honors project this semester, and we went out there last week to check out some stuff. One thing I was struck by was how much more deformed these rocks were than I had expected. This was particularly evident in some coarse meta-sandstones and meta-conglomerates of the Weverton Formation, which showed some well-developed deformational fabrics: …
8 May 2011
Plumofare Gap
I already mentioned the “paddle hackle” that I saw on the field trip I took to Thoroughfare Gap in February. Well, this week I went back out to Throughfare Gap twice, once with a student and once with my fianceé and a friend of ours. I saw cool new plumes both times, decorating joint surfaces in the Weverton Formation quartzite. Here’s the best one, seen in one of the building …
15 March 2011
Sugarloaf III: Tension gashes
Background geology of the Sugarloaf Mountain area. (March 2010) Primary structures in the meta-sandstone of the Sugarloaf Mountain Quartzite. (yesterday) Background on tension gashes. (August 2010)
14 March 2011
Sugarloaf II: Primary structures
You’ll recall that I detailed a trip to Sugarloaf on this blog back in March of last year. Well, on Saturday (March of this year), Lily and I returned to this distinctive knob of quartzite for a five-mile hike. Along the way, we saw plenty of metamorphosed quartz sandstone (now quartzite), which was similar to what we saw on the previous Saturday’s hike, to Buzzard Rock on the northeast tip …
5 March 2011
Buzzard Rock
Took a hike this morning with my bride-to-be, out to Buzzard Rock on the northeastern corner of Massanutten Mountain. There, we observed numerous boulders of Massanutten Sandstone float, many bearing charismatic cross-beds. Here’s one more slab of float, presumably weathered out along the main bed, showing gorgeous internal cross-stratification: A closer look at the left side of this sample, animated via GIF: Why animated? Because I can. The object of …
22 February 2011
Beds and veins in the Weverton
Callan joins some students from George Mason University on a field trip to the rock exposures at Thoroughfare Gap, Virginia, where meta-sedimentary rocks are exposed in the eastern Blue Ridge province.
29 November 2010
Tavşanlı Zone field trip, part 7
Part 6 of the Tavşanlı Zone field trip had us looking at some blueschists and eclogites. Today we conclude the terrific field trip with a brief look at a couple more stops.
28 October 2010
Accretionary Wedge #28: Deskcrops
In honor of this month’s Accretionary Wedge (geoblog carnival; this month the theme is “deskcrops”), I recorded the following short video, showcasing some samples I have in my office: stromatolite (western Montana), conglomerate (Patagonia), schist (New Hampshire), anorthosite (New York), amygdular meta-basalt (Virginia), amphibolite (California), hematite concretions (eastern Montana), and a stretched-pebble lineated meta-conglomerate (Turkey).
Callan Bentley is Associate Professor of Geology at Piedmont Virginia Community College in Charlottesville, Virginia. He is a Fellow of the Geological Society of America. For his work on this blog, the National Association of Geoscience Teachers recognized him with the James Shea Award. He has also won the Outstanding Faculty Award from the State Council on Higher Education in Virginia, and the Biggs Award for Excellence in Geoscience Teaching from the Geoscience Education Division of the Geological Society of America. In previous years, Callan served as a contributing editor at EARTH magazine, President of the Geological Society of Washington and President the Geo2YC division of NAGT.