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26 March 2021
It’s Friday, and it’s been a few Fridays since I offered you a fold. Let me make up for that with five Friday folds today, all from the incredible collection of free 3D models by Sara Carena on Sketchfab. Sara is a senior scientist/lecturer in Geology at Ludwig-Maximilians University in Munich. [sketchfab id=”f424c677140147138f25d15b5c9a1718″ start=”0″ spin=”” controls=”0″] [sketchfab id=”79f5e7be0c7f4e5397cf2158fcce1dd4″ start=”0″ spin=”” controls=”0″] [sketchfab id=”58f60e9e9aab4e919b0b7be442d23b66″ start=”0″ spin=”” controls=”0″] [sketchfab id=”79b2a04061634c188df31ef26954fd56″ start=”0″ spin=”” …
5 February 2021
Here’s a good sample, another one I inherited from Declan de Paor when he retired from Old Dominion University. It’s an interesting sample – I guess I’d call it a graphitic clay shale, but it’s surprisingly lightweight, so I’m not super confident that’s right. The bedding surfaces are glossy and slick, indicating some flexural slip between the layers. In terms of composition: It’s too beautiful to cut up and make …
19 June 2020
My friend Alan Pitts is orchestrating a virtual field camp for George Mason University this summer, utilizing outcrops in central Italy’s Apennine Mountains. Here’s a 3D model he just posted of one of the most impressive outcrops there: the chevron folds in the Scaglia Rossa limestones at Lago di Fiastra. I featured the site as a Friday fold 3 years ago when Alan took me there in person, but this …
2 April 2019
A book by Nick Pyenson (of the Smithsonian Institution’s National Museum of Natural History) details the past, present, and future of whales. Combining paleontology, oceanography, environmental awareness, evolution, and history with personal stories of field work and insight, it’s a compelling tale of modern science on charismatic, mysterious creatures.
22 August 2018
A reader asks: “What is foliation and what makes it so important to the structure of rock?”
Callan answers with a lot of images of beautifully foliated rocks.
25 May 2018
This is a block of rock I found in the rock garden at Northern Arizona University a few weeks ago: [sketchfab id=”16a73845eaf44a23b28b2f1bb3921ba9″ start=”0″ spin=”” controls=”0″] It’s intensely folded. Not sure what kind of rock it is, but it was quite dense.
26 March 2018
A solo hike in search of anticlines yields new outcrops and good views!
14 March 2018
New media to show off exemplary features of the Devonian-aged Hampshire Formation along Corridor H, West Virginia
Last week, I was in Morgantown, West Virginia, to deliver a colloquium talk to the geology department at West Virginia University of geological visualization. The next day, I took some time on the way home to geologize a bit on the road called Corridor H, a gorgeous transect through the eastern Allegheny Plateau and western Valley & Ridge provinces. I focused that day on the Hampshire Formation, Foreknobs Formation, and …
2 February 2018
The Friday fold is a really cool 3D model of differentially-weathered calc-silicate rocks in Scotland that were folded during the Caledonian Orogeny.
12 January 2018
In keeping with the Arizonarific theme of this week’s posts (thanks to my participation in the 2018 Structural Geology and Tectonics Forum), I thought I would wrap up my ‘geology of the Phoenix area‘ posts with a walk I took on my last day there. This was to what Google Maps calls “Hayden Butte,” but the locals call “A Mountain.” Not “a mountain,” but “the mountain called ‘A‘.” It has …
8 September 2017
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 you see below. Enjoy! Here’s a GIGAmacro of the sample (you need Flash enabled to …
9 August 2017
A showcase of five new 3D digital models of awesome rock samples and outcrops, produced using Agisoft Photoscan.
15 July 2017
I collected only a single rock on my summer travels in France and Italy. (Those of you who know me will realize how extraordinary this low number is!) It’s a flow-banded rhyolite from Vulcano, in the Aeolian Islands north of Sicily a few weeks ago. It contains porphyritic vesicular basalt xenoliths. I featured a similar sample on Twitter yesterday on the occasion (supposedly) of “International Rock Day”: For #InternationalRockDay , …
9 June 2017
Check this out: is it a fold? Annotated to show the 3D expression of the ‘bed’ (left) and cross-sectional view (right): Here’s a 3D model of the outcrop to better convey its shape: [sketchfab id=”7a5a02f9521d45dab56b2464a37c8dd9″ start=”0″ spin=”” controls=”0″] This is in the same sandstone unit I blogged about on Tuesday with the apparent soft-sediment deformation. This could be another example of the same general class of pre-lithification structures, or it …
5 June 2017
I’ve been busy making 3D models lately. Here are three ones united by a theme of being sand that was deposited relative to mud. In one case we have scouring to make flutes, in another case we have have localized sagging to make “ball & pillow” structures, and in the third case we have an extraordinary submarine landslide deposit. For two of them, the shale has been preferentially etched away, …
9 May 2017
The Foreknobs Formation is a Devonian unit in the Valley & Ridge province of the Mid-Atlantic Region. It was deposited in relatively shallow near-shore conditions during the Acadian Orogeny. On a field trip to Corridor H, a new highway transecting the West Virginian Valley & Ridge province on Monday, I stopped to document a couple of beds showing very nice ripple marks. These ones are symmetrical, and thus likely represent …
3 March 2017
Let’s reminisce back to the Walls Boundary Fault on the Ollaberry Peninsula of Shetland today. Here’s a 3D model to go along with the ones I posted last time: It’s a little ragged, but so am I at the end of the workweek! Happy Friday. Have fun spinning this thing.
25 February 2017
Some enormous concretions are encountered in a shale quarry in the central Fort Valley. Concretions like these are typical of the Devonian-aged Millboro Formation.
24 February 2017
For your Friday fold this week, I present to you a 3D model of a sample of kinked schist from Beavertail State Park, Rhode Island. Spin it right round, baby: This is another sample from the structural geology collection of Carol Simpson and Declan De Paor.
13 January 2017
On the western coast of Islay, Saligo Bay showcases turbidites of the Neoproterozoic Colonsay Group. The Smaull Graywacke shows Caledonian (late Ordovician) folding and cleavage superimposed on world-class graded bedding. There’s also a nice dolerite dike to examine.