My friend Vali Memeti posted this photo of her husband Scott Paterson examining some folded rocks on the coast of Tasmania last week. It looks like Vali and Scott enjoyed a fun excursion to this “Even Further” Down Under location. This is the Sulphur Creek geologic site, part of a geocache suite called “Created from … Read more
The Friday fold is a figure from a 1922 book about the geology of the Alps by Swiss structural geology genius and artistic master Albert Heim. Marvel at his gorgeous depiction of the internal and long-since-eroded structure of these mighty mountains.
Here’s a guest Friday fold from reader Carl Brink: Carl tells me that this is: Precambrian Amphibolite schist float boulder from the Idaho Springs Formation in Rist Canyon west of Fort Collins, Colorado. Knife is 2.25 inches long. Thanks for sharing, Carl!
The guest Friday fold comes to us from the Miocene of California, deposited in a releasing bend basin along the San Andreas Fault.
This Friday, let’s return to Glacier National Park. Here are some folds in Helena Formation limestone: Can’t see them? Fair enough – the point of maximum inflection appears to be hidden behind a snow-filled gully: But in addition to that big fold, there are several kink bands in there, too. Let’s zoom in: Here they … Read more
What does it mean for a vein to be “quantankerous?” Well, to start with, it’s quartz. Second, it has to be disagreeable or cantankerous. This vein, seen in meta-arkose of the Catoctin Formation near the summit of the Blue Ridge at Rockfish Gap (not Afton Mountain), is such a quantankerous individual: You’ll notice its “S” … Read more
Over the summer, I treated you to a great big kink fold in the sedimentary rocks of Glacier National Park. Here’s another set: Did you see both of them in that first picture? – one bigger down below, one smaller up above. Both kink bands dip to the left. Let’s zoom in on the upper … Read more
Happy Friday! Here’s a sample from the Smithsonian Institution’s National Museum of Natural History in DC: As the label says, we have a nice example of ptygmatic (“intestine like”) buckle folding here. It comes from Finland. The coarse equigranular crystals in the vein appear to be mainly potassium feldspar and quartz. The surrounding matrix has … Read more
Here’s a cool fold pair that rolled through my Twitter feed today: 2nd day Appalachian field trip. Recumbent isoclinal folds on a clear morning at Sauratown Mtns window NC pic.twitter.com/sHkmbp6roh — Joe Allen (@CU_in_the_field) October 6, 2017 Joe Allen gave me permission to share it with you here. Here’s the photo with bedding traced out … Read more
The Friday folds are small soft-sediment deformational features within a dismembered, folded sandstone (a “ploudin”) from a mass transport deposit from the latest Devonian of West Virginia.
It’s the First Friday of Fall! Here’s a sort of fold to help you celebrate: a section through a ∧ shaped bend in a vesicular basalt flow from the eastern flanks of Mount Etna in Sicily. It’s due to volcanic lava flowing rather than ductile deformation of a pre-existing solid rock (our usual habit with … Read more
The Friday fold comes from highly foliated rocks in a shear zone near Tyrol, Italy. It was contributed by reader Samuele Papeschi.
I was transferring some samples into my structural geology cabinet last week when I found this beautiful ptygmatic (“intestine-like”) folded quartz vein. I thought it deserved some wider circulation. I can’t recall where it came from, but it’s beautiful, with a train of a dozen or so isoclinal folds. So I made the digital media … Read more
Okay, I’ll admit this is a bit of a stretch, but here’s your Friday fold: The mosaic-covered floor of this long hallway in the Villa Romana di Casale in central Sicily shows profound warping. The middle shadowed area sags downward by at least a meter, maybe more. It’s not a geological material that’s been deformed, … Read more
When in Rome, do Friday folds as the Romans do? Here are some images from my brief, sweltering visit to the Roman Forum(s) this past summer. The whole region is a jumblepile of ancient ruins in a thousand styles. Almost nothing is labeled. It looks like this: This particular building held up a bit better, … Read more
For the Friday fold, Callan digs out images of Eagle Rock, Virginia, well aged in his digital archive for a decade!
It’s Friday and that means “fold time” here at Mountain Beltway. Today, we feature a trio of samples on display in the halls of the Department of Earth and Planetary Sciences at the University of New Mexico.
It’s Friday! How about we celebrate with a beautiful kink fold from a gorgeous national park?
My friend Ander Sundell at the College of Western Idaho is the source of today’s Friday fold. It’s from somewhere in Sardinia, and I think you’ll find it visually striking: Ander says: The rocks here are Silurian phyllites generated from mudstones that were deposited on the floor of the rheic ocean basin. The color and … Read more
The Friday fold visits the Apennine Range of central Italy.