The Friday fold is a contribution from the Massachusetts Geological Survey. It shows a migmatite with lovely structure. An upcoming (free) field trip to this location will be part of the 2012 Structural Geology and Tectonics Forum: an event readers may be interested in attending
I got this note via email last week. Hi Callan, First of all, congratulations to your blog. It is just great. I would like to contribute to your “Friday fold” section. A few words about myself. I am born in Austria and did my BSc and MSc at the Montanuniversitaet Leoben. In September 2011 I started … Read more
Rob Simmon of NASA’s Earth Observatory is the source for today’s Friday folds. Last week, he tweeted this image to me: That’s a excellent example of the outcrop pattern of a more or less horizontal outcrop of folded rock. To the north is a synform (notice that where streams have eroded it, the bull’s-eye pattern … Read more
I got an email a few weeks back from Moritz K., a PhD student at the Universidad Nacional Autónoma de México (UNAM) in Querétaro. He wanted to offer up a potential Friday fold. Here’s what he had to say: I wanted to send you a couple of pictures of folds I took in my PhD … Read more
Richard Littauer, a MSc student in Computational Linguistics at the University of Saarland (on Twitter at @richlitt) sent me today’s Friday fold. It comes from a garden at Nijo Castle in Kyoto, Japan. Definitely some wavy layers there. It’s a lovely specimen that would add gravitas to anyone’s garden. Not sure what it is – … Read more
When are sedimentary layers also faults? …When the slab-like layers slip over and under one another during the act of folding. Structures traditionally confined to faults show up on the bedding plane in these circumstances. Callan shares a shiny example from West Virginia in the form of an animated GIF.
One more structure from the Castner Marble. This one is clearly tectonically-induced: Top to the left! (East over west)
The Castner Marble is an extraordinary Mesoproterozoic limestone (later re-crystallized and metamorphosed) that exhibits some primary structures (both explicit and ambiguous) and some secondary (tectonic) overprints. It’s exposed in the Franklin Mountains of west Texas.
Searching for Peter Luffi’s latest Where On Google Earth? challenge, I found myself touring Iceland last week. While I didn’t find the strange comet-shaped feature he posted, I did find this: And zooming in a bit, to the high-contrast area in the center: This appears to be volcanic ash layers distorted by glacial flow and … Read more
Hand sample of folded limestone strata in West Virginia (presumably Devonian in age). Note the rip-up clasts and large grain size at the base of the sample (to the right in the photo). Note the fine-grained, thin-bedded shale laminations towards the top (left) of the sample, too. Together, they tell a story of decreasing energy … Read more
I know we spent time last Friday on some nice folds in the Poleta (?) Formation in the White Mountains of California, but here are a few more that I saw on my way up to the Ancient Bristlecone Pine Forest… Some elliptical objects caught my eye: Traced out along the plane of bedding, these … Read more
Callan and his field studies students encounter a lesson in the White Mountains of eastern California that combines bedding, cleavage, folding, and even fossil archaeocyathids!
While on Callan’s field course in eastern California, student Filip finds a lovely fold sample.
Some views from the airplane, over southern Wyoming (first two photos) and north-central Nevada (last four), last Saturday morning… A canyon: …and zooming in to the middle area of the previous photo: Strata upwarped into a structural dome (that has been “planed off” to be topographically horizontal, revealing a bull’s-eye-shaped outcrop pattern, then differentially weathered … Read more
Meter-scale fold in metagraywacke layers at the head of Mather Gorge, Maryland shore of the Potomac River, highlighted by differential weathering along the layering. Annotated interpretation: Happy Friday!
GigaPan by Alan Pitts, as part of the M.A.G.I.C. project that we are working on. Here’s another one from a few meters away. Here’s a shot from 2.5 minutes after Alan saw this anticline for the first time. Here’s some shots of my own early visit to the site, after I first found it.
Another sample from the collection on display, both indoors and out, at the University of Texas at El Paso. Don’t know anything about it beyond its lovely differential weathering. Happy Friday.
Callan looks south across the border from Texas. Above the drug-war-ravaged town of Juarez, the Sierra de Juarez Mountains feature an enormous recumbent synform.
From the road that keeps on giving: new New Route 55, in West Virginia, west of Moorefield.
I’m in El Paso, Texas, today (and tomorrow and Saturday), collaborating on a massive brainstorming session for a new NSF-funded initiative called InTeGrate, which is all about Interdisciplinary Teaching of Geoscience for a Sustainable Future. As leader Cathy Manduca said today when she opened our session, “We’re here to save the world!” And we’re going … Read more