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