I shot this gigapan (900 images) last Thursday during the lunch break of the annual “Geology of Virginia” symposium hosted by the Commonwealth of Virginia’s Department of Geology and Mineral Resources. [gigapan id=”75096″] It shows the rock garden outside the DGMR’s offices in Charlottesville, a place where they have collected charismatic megasamples from across the … Read more
Walking back to my hotel after departing the Northeastern / North-central GSA section meeting on Sunday, I noticed this fine shear band cutting across a polished slab of granite on the exterior of an office building in downtown Pittsburgh: You’ll notice some grain-size reduction along that shear zone, and what looks to be a decent … Read more
Migmatite schist sample from Orange Springs Farm, near Unionville, Virginia, with cm-demarcated pencil for scale. Sample was cut and polished. Here’s what the untreated sample looks like: [youtube=http://www.youtube.com/watch?v=XDDcLVp_4Ss] Happy Friday. Enjoy your weekend. I’m off to the Northeastern / North-Central joint section meeting of the Geological Society of America today. We’ll see if my time … Read more
A few microscope photos for you, showing close-ups of feldspars in igneous dikes in the Crazy Mountains of Montana… You’ve seen these rocks before, when I posted a few field photos from this area in August 2009. I took these images of feldspar phenocrysts in a hand sample (from a quartz latite dike) with my … Read more
Lamprophyre dikes on the Billy Goat Trail (Potomac, Maryland): are they offset because of a fault? Or not? Inquiring minds want to know!
The Friday fold takes us to some high-grade metamorphic rocks in the Piedmont of northern Virginia.
Today, you get the first of several batches of photos dealing with one of the most magical places I’ve ever been, the Cappadocia region of Turkey. Cappadocia (pronounced “kap-uh-doke-ee-yuh“) is an area of eroded volcanic tuffs. The overall effect is badlands-like, but without the micro-turrets and hoodoos. The individual erosional remnants are larger in Cappadocia … Read more
Part 4 of the ongoing series examining the geology of the San Francisco area. In today’s post, Callan visits Kirby Cove in the Marin Headlands, where intensely deformed chert can be found on one end of the cove, pillow basalts on the other, and an “artificial dune” in the middle.
Second in the on-going series about the geology of San Francisco: this post explores the pillow basalts of the Marin Headlands Terrane.
Obsidian bearing well-developed conchoidal (clam-shell-shaped) fracture with concentric ribs, as displayed at the recent U.S. Science and Engineering Festival on the National Mall by a local gem/fossil/mineral club.