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16 September 2010
Drilling: what, why, and how
As mentioned, I spent a significant part of last weekend was spent on a paleomagnetic sampling project with collaborators from the University of Michigan. On Friday, this was our field area: That’s the south slopes of Old Rag Mountain, a popular Blue Ridge hiking destination because unlike many Virginia peaks, when you get to the top, you see some rocks instead of 100% trees: But we didn’t come here for …
10 September 2010
Friday fold: Kinky metagraywacke from DC
Fourth edition of the “Friday fold;” second one via video. Happy Friday!
1 September 2010
Another metamorphosed graded bed
Over the summer, when my blogging access was limited to my iPhone, I uploaded a photo (taken with the iPhone) of a metamorphosed graded bed on the summit of Mount Washington, New Hampshire. Here’s another one that I saw, further down on the mountain, on the Auto Road (famous for its iconic bumper sticker): Lens cap for scale. …And here’s the obligatory annotated copy: Both of these images are enlargeable …
25 August 2010
Jointed Virgelle
One of the stops my Rockies students and I made this summer was a dinosaur paleontology tour through the Two Medicine Dinosaur Center in Bynum, Montana. The folks there are very accommodating, and at my request gave the class a bit of stratigraphic context for the dinosaur fossils. For instance, we visited the geologic formation which underlies the dinosaur-bearing Two Medicine Formation: it’s a beach sandstone called the Virgelle Formation. …
24 August 2010
Tipping your tension gash
Tension gashes are small veins that open up when rocks get stretched. Often, they are arrayed en echelon with respect to other tension gashes, all oriented in the same direction. Here is a sample of tension gashes I found this summer in rip-rap (i.e., not in situ) at some building site in New England. (I forget where, but it doesn’t matter, since it’s rip-rap. Could have come from anywhere!) Check …
10 August 2010
Metamorphosed graded bed
This is the coolest thing I’ve seen this week: a graded bed metamorphosed via Acadian mountain building: The graded bed starts at the Swiss army knife at left, where you see an abrupt transition between coarse grained metamorphic porphyroblasts (“pseudo-andalusites”) and finer grained quartzite. This was once a mud to sand transition when these were loose sediments in the Kronos Sea, but with elevated temperature and pressure, the clay minerals …
30 July 2010
Ripple marks
… And here are some ripple marks from a block of the same sandstone in the previous image. Nice! Hope everyone is doing well. Lots of good geological experiences to report on, buy it’s hard to write a substantive blog post from phone… You’ll have to wait until I’m back at a computer!
Mudcracks
Here’s a package of mudcracks from a block of riprap on the waterfront of Burlington, Vermont: Oh yeah….
18 July 2010
Gros Ventre landslide, Wyoming
Yesterday’s field work took us to this classic mass wasting site:
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.