Callan Bentley This site, from the USGS, shows depth to the water table for a well in Virginia: You’ll notice the tidal influence on the water table (broad sine-curve-like up and down crests and troughs at ~12 hour intervals), and then a sudden perturbation which caused some wiggles almost two and a half feet of magnitude! This, … Read more
When I was out poking around in the woods, confirming for local geophile Barbara that indeed her local geologic map wasn’t 100% accurate, I noticed this on the frozen ground: We have seen this before, in a post back on NOVA Geoblog, almost exactly a year before I took this photo. Here’s another shot from … Read more
One of the cool things about being the local geoblogger is that people get in touch with you about local geology. Sometimes this even leads to meeting up for field trips. Here’s two quick photos from a recent (January 2010) field trip to a creek near Springfield, Virginia. My host was Barbara X, a local … Read more
For those of you who are potential NOVA students (really, that’s pretty much anyone on the planet), I wanted to let you know that applications are now open for the July 2010 Regional Field Geology of the Northern Rockies course that I co-teach with Pete Berquist of Thomas Nelson Community College. A more detailed description … Read more
Seeing my cat in this posture: …made me think of this: Where did those hind legs go?
Earlier in the month, during the big snowstorms, my window got plastered with snow. This snow formed a vertical layer which then deformed under the influence of gravity. Looking at it through the glass, I was struck by how it could serve as a miniature analogue for the deformation typical of a mountain belt. Let’s … Read more
Last September, at the location of the faulted moraine (eastern Sierra Nevada, California), I took some photos of some of the sexier plutonic contacts exposed in big boulders (erratics) of the glacial till composing the moraine. Check them out. What do you see here?
Today, some photographs from Guatemala. I know one of my geoblogopeers is down in Guatemala doing research, so I’ll be interested to hear her take on these photos. These photos all come to us courtesy of my friend Courtney, who is a librarian at M.I.T., and a fellow M.S.-graduate of the University of Maryland geology … Read more
On last May’s GSW spring field trip to Chain Bridge Flats, I saw a quartz vein: Surely, upon looking at this photograph, you will be struck by the way the vein is not the same thickness along its length, and parts of it appear to be a white line transitioning into a parallelogram, and back … Read more
A few photos from last May’s spring field trip with the Geological Society of Washington… Here’s the group at Chain Bridge Flats (far westernmost-Washington, D.C.), looked at the metamorphic rocks there — a metagraywacke melange known as the Sykesville Formation. Another group shot, with field trip leaders Tony (khaki shirt) and Gary (red jacket) Fleming … Read more
Guess which day I launched the blog? Thanks to everyone who has stopped by so far. I’ve gotten the same question several times from several readers, so let me address it here for everyone’s edification: Yes, NOVA Geoblog will be left “as is,” where it is. You can link to it, or bookmark it, or … Read more
Today, you get a photo of a fossilized crinoid stem, from the Mississippian-aged Lodgepole Limestone of the Bridger Range, north of Bozeman, Montana. A pencil is provided for scale: Zoomed-in a bit, and cropped. The segments (“columnals”) show up nicely: Crinoids are echinoderms, the invertebrate phylum which includes sea urchins and sea stars. However, at … Read more
A friend forwarded this via e-mail to me today… U.K. readers may be interested in participating. Millstone Grit? Kimmeridge Clay? Old Red Sandstone? Durness Limestone? Yorkshire Lias? ………. What are YOUR top three British sediments? BSRG (British Sedimentological Research Group) are conducting a small survey to find out what formations geologists consider the “best” sedimentary … Read more
Mark your calendars! Prehistoric: D.C. will profile (part of) the ancient past of Washington, D.C., in an episode to air February 28, 9pm, on the Discovery Channel.
Whilst discussing how to quantify strain with my GMU structural geology students recently, I hit upon a cool analogy. In order for you to understand the analogy (assuming you’re not a structural geologist), I’ll have to review some background information first. Stick with it, and I promise you a salamander at the end. Structural geologists … Read more
Since yesterday’s live-blogging the rock sample prep routine turned out blurry, I figured I owed it to this sample, and to you, to give everyone a better look. So I scanned it this morning. Penny for scale. Assuming that your computer screen is vertical, this is in the same orientation as when it was deposited: … Read more
Continuing with some photos from eastern California… After checking out the faulted moraine, but before heading up the hill to check out the indurated shear zone (which you can just see in the background of this photo), we stopped to check out this visually-striking outcrop: Look at the glee on the faces of Kurt (green … Read more
Today during Physical Geology lab, I used our grinding wheel to plane down a turbidite sample than I collected this past December down in Chilean Patagonia. Thanks to the technological miracle of blogging via iPhone, I can send it to you in a mere 45 seconds. Enjoy the graded bed: let it transport you back … Read more
Small-scale debris flows as a muddy slurry flowed over weathered-out chunks of the Bishop Tuff. Probably about two days old. Southern edge of the Volcanic Tableland, last September.
Check out these cool structures in one of the amphibolite bodies exposed along the Billy Goat Trail (C&O Canal NHP, near Potomac, Maryland): Those are shear bands — basically small shear zones that are discretely localized within a larger body of less-deformed rock. Note the grain-size reduction visible in the shear bands, their dextral sense … Read more