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11 June 2021

Friday fold: inadvertent kink fold analogue model

It’s Friday!

Adam Forte, a geology professor at LSU, posted this image yesterday on Twitter:

It’s a box of sheets of newsprint, stored vertically and ignored for a while, now rotated 90° so we’re looking at a cross-sectional view. To me, this is an excellent example of a physical analogue modelling experiment (albeit inadvertent) that demonstrates the process by which kink folds form. The key parameters to get this distinctive style of folding is (1) a highly mechanically layered material, (2) a substantial confining pressure, and (3) a dominant stress direction is parallel to the orientation of that layering, or close to it. In the case of Adam’s box of paper, the layering comes from the discontinuities between the sheets, the confining pressure comes from the box, and gravity’s pull was the principal stress direction (σ1). In geological examples that I have celebrated on this blog, the layering is usually sedimentary bedding or metamorphic foliation, and compressive tectonic stress is the cause of the kinking, while being buried deep in the crust provides the requisite confining pressure. Compare what you see above to these examples:

Other kink folds, from previous posts:

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Dalradian schists, Walls Boundary Fault, Shetland


Harpers Formation phyllite, Harpers Ferry, West Virginia

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Dalradian schists, Arran, Scotland

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Somewhere else in Arran (not my photo)

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Metagraywacke, Billy Goat Trail, Maryland


Playa limestones, Basin & Range


Catoctin Formation greenschist, Thoroughfare Gap, Virginia


Unknown source – kinked phyllite from the GMU teaching collection


Sample on display at Tennessee Tech

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St. Ninian’s Isle, Shetland

And one more from Shetland, again of the Dalradian schists adjacent to the Walls Boundary Fault, since they provide the closest visual match to the paper in Adam’s box, but this time as a stone in a rock wall:
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Peace be upon you. Enjoy the weekend. Stretch those kinks out, and get some rest.

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29 May 2021

Book report

It’s been a while since I’ve checked in with you on recent reads. I managed to read a few volumes over the course of the disjointed, stressful fall semester. Here are a few of the highlights:

How to be an Antiracist, by Ibram X. Kendi

An important book that explores racism in its many, many forms, structured around Kendi’s reflections on his growth as a person. The “memoir” aspect of the book touches on moments that illuminate some aspect of racism in the United States, including many of a deeply personal nature in the author’s life, and that then leads to more general discussions of capitalism, elitism, or racism within the Black community. One great theme that leaps out of these pages is the inherent racism that exists in all of us, because we have been raised within a racist society. What does “racist” mean in this context? Many things – but in short, it means perpetuating a series of policies that lead to inequality on the basis of race. The second great contribution of How to be an Antiracist is the careful articulation of a series of precise definitions of what it means to be racist in various contexts, and —equally importantly— what it means to be antiracist. Antiracism is a collection of behaviors and policies that lead to increasing equality for all people in our society. I found the rumors about this volume to be true: that it offers a fresh and clarifying interpretation of our societal situation, and by defining terms unambiguously and with compare/contrast examples, shows a way forward toward a better world. Thought-stimulating and recommended.

The Rendezvous, and other stories, by Patrick O’Brian

Patrick O’Brian wrote one of my favorite series of novels of all time, the astounding Aubrey/Maturin adventures. I’ve read several of his other books too, including several other adventure novels and a biography of Joseph Banks. But this is the first time I’ve delved into his short stories. As far as I can tell, this is the only collection of them under a hard cover. I found the stories to be a mixed bag. There were many moments of terrific writing, as you might expect, but overall I think that was outweighed by a pervasive sense of misery and gloom. These stories are almost uniformly about unhappy people in trying circumstances. A lot of them felt like they could have been written by Hemingway, in terms of mood and setting, though not sentence structure. So many focused on fishing, hunting ducks, hunting foxes with dogs. Sometimes this was mixed with the theme of unhappy relationships, sometimes the unhappy relationships were presented on their own. There were many sharp, well-observed details, but none of it really got my serotonin flowing the way an Aubrey/Maturin novel would.

The Invisible Library and The Masked City, by Genevieve Cogman

These are the first two novels in a fun series called “The Invisible Library.” In them, the job of “librarian” is raised to a new level: a spy and an adventurer, traversing alternate realities in search of unique books. The idea is that there is this awesome sounding, multi-square-mile Library that exists in a place out of time and space. Its agents can slip into different versions of the world, fighting against both local bad guys and rogue Library evildoers in a quest to balance chaos, magic, and science. The concept is very fun – visit a Victorian London choked with smog, but with battle alligators, werewolves, and zeppelins piloted by ornery cabbies. Protagonist Irene must mentor a smoldering trainee while sparring with the local detective, the proud culture of humanoid dragons, and a group of Slytherin-esque individuals called Fae. Plus there’s the office politics of the Library itself. The true charm of the series comes not so much from the genre blending of the alternate worlds as from Irene’s thought processes as she figures out her way forward through one crisis after another. The first book is a bit better than the second, but I look forward to seeing where the series leads.

What the Best College Teachers Do, by Ken Bain

This is a follow-up to a volume I read early last year, focused on student behavior. Here, Bain focuses on the approach, preparation, and guiding questions of highly effective professors. He looks at their behavior in terms of their mindset and respect for their students: their focus on learning and growth in their students. I picked up a few new perspectives and ideas from reading it. One is to brainstorm out and articulate all the motivational questions about why a particular course is worthwhile – what major questions does it help the student address? Another, more prosaic, is to make each exam cumulative, and each successive exam score replaces its predecessors, so students are continually motivated to learn and integrate their knowledge. Finally he makes a strong argument against late penalties for assignments that come in after the deadline. Most of the book focuses on broader material, but little of it felt new or uniquely insightful to me. Excellent professors care about their students, prepare thoughtfully, seek feedback, and are self-reflective. None of that struck me as particularly shocking. Also: For what it’s worth, I think the book designers made a mistake with the cover: the back of a silver-haired white man’s head? Come on.

Eating the Sun, by Oliver Morton

Finally, I’ll highlight the third of the great books written by Economist science/climate writer Oliver Morton. This one, from 2008, examines photosynthesis from every angle imaginable, telling a series of stories about scientific insights and the people who produced them in Morton’s characteristic prose: profound, playful, appreciative. To write compelling prose about the Calvin Cycle is a laudable achievement; I’m not sure it has ever been accomplished before! I was really impressed with the discussion of photorespiration and C4 photosynthesis as a response. Morton’s great distinction is his ability to get into the nittiest-grittiest details, while simultaneously retaining a serene sense of poetry about the whole matter. A discussion of entropy, for instance, leads to a comparison between fire and information. “Life,” Morton concludes, “is a flame with a memory.” He knows the right analogies to present to change the reader’s perspective on the matter. Another example, on the subject of the endosymbiosis of a cyanobacterium within an archeal host cell to make the proto-chloroplast: “Because humans are big creatures, it is natural for us to see the story of this symbiosis as starting with an act of ingestion. But from the cyanobacterial pint of view it was much more like a colonization. Photosynthetic bacteria had tackled a number of environments – the open ocean, bacterial mats in tidal flats, lake-bed sediments and many more – before the endosymbiosis. The insides of early eukaryotic cells were just another  new environment, one which, if permitted survival, would be colonized.” I’ve now read three of Morton’s four books, and each has changed the way I think about the planet I live on.

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16 May 2021

A Brief History of Earth, by Andrew H. Knoll

Andy Knoll wrote a masterful, fascinating book in 2003, Life on a Young Planet. Now, 18 long years later, he’s published another popular science volume, an eight-chapter encapsulation of our planet’s story. I don’t know why he’s waited so long (busy doing science, I guess) but he really does have a talent for telling geobiological stories in a full but accessible way. Knoll is a paleontologist, and the great theme he explores in Earth’s biography is the interaction between the nonliving and living portions of the planet. The volume is organized chronologically, starting with 30 pages on the chemical processes that developed in the condensation of the presolar nebula, then moving into the physical processes that organized the planet into layers and triggered motions in some of those layers, into the origins of life, and the rise of oxygen. Animals and plants get a chapter each, which leaves one for a discussion of singular catastrophes (LIPs, extraterrestrial impacts) that interrupt the flow of evolution, and the human influence of natural systems after that. Knoll draws a parallel between the end-Permian mass extinction and the current “Anthropocene” suite of changes in the planet, concluding that the next chapter in the saga is up to us all, collectively, to write.

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7 May 2021

Friday fold: Lynchburg Group

Last weekend, I went to get my second vaccination, and because of the ridiculous quirks of the way the vaccination campaign is (dis)organized, I had to travel to Lynchburg, Virginia, to get the shot. An extra two hours on the road (roundtrip) may sound like a pain, but it was ameliorated by getting to see some cool outcrop along the way.

This is in Riveredge Park in Madison Heights, Virginia, directly across the James River from downtown Lynchburg:

The rock here is Neoproterozoic Lynchburg Group metasediments that were folded and faulted during Appalachian mountain-building. The layering you see is primary sedimentary bedding, and it serves as strain markers for westward-verging asymmetric folds (and tectonic cleavage in the muddier layers).

In the upper right (east), the outcrop features sandy layers that show off more open folding:

Look for the variation in dip across this field of view: essentially vertical in the upper left, moderately left-dipping in the center, and approaching horizontal at the lower right edge:

Small-scale parasitic folds and cleavage are particularly well expressed at this spot:

(I had teased that site on Twitter earlier this week.) Another example of the little crenulations:

Rock fall aficionados will also appreciate this outcrop for its instability. There’s a skin of soil and vegetation stretching across a rock-free chasm at the top of the cliff, and a pile of debris at the bottom. Access to the cliff is fenced off with a “no trespassing” sign posted; a reasonable precaution it seems to me. Still, the debris run-out reached to the edge of the parking area and had broken through one of the fence cross-beams, so maybe they should go further.

It’s also interesting to see the various processes of weathering playing out here. The outcrop was much prettier just two years ago, as this Google Maps Streetview capture shows. Since then, it’s rotted and painted itself with iron oxides and what appears to be travertine:

There are even some little “stalactites” building downward off some of the overhangs:

I collected one sample there; which I intend to turn into a 3D model – Maybe in time for next week’s Friday fold…?

Happy Friday, and Happy End-of-the-Spring-Semester to those who observe!

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16 April 2021

Friday fold: Colorado cluster

Reader Carl Brink laments the lack of robust recent Friday folds, and he’s decided to do something about it!

From Colorado’s Front Range, he sends this image of an intensely folded granite dikelet within Proterozoic biotite schist:

That’s intense. Ptygmatic, sure, but the butterfly-like sense of symmetry to it reminds me of a Rorschach blot.

What a gorgeous fold. Thank you, Carl!

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26 March 2021

Friday folds: 3D models by Sara Carena

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.

Absolutely super models of absolutely super folded rocks. Well done, Sara! Viewing these should get everyone’s weekend off on the right foot!

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20 February 2021

Ms. Adventure by Jess Phoenix

Jess Phoenix first came onto my radar when she ran for Congress in 2018. Since that time, and thanks to Twitter’s ability to connect geologists, Jess and I co-hosted a 2019 Pardee Symposium on geoscience communication at the GSA annual meeting in Phoenix, Arizona. Jess stepped in at the last minute to cover for Iain Stewart, who was unable to be there due to a family emergency. Like Iain, Jess has been the face of geoscience on television programs, an advocate for for science-based policy and the excitement that a geology-infused perspective on the world brings to one’s life. In Ms. Adventure, her first book, Jess recounts the experiences that made her choose geology as a career, and formative lessons on volcanoes, research cruises, and television. It’s a fun read, more of a memoir than a geoscience text, but there are bite-sized explanations for volcanological phenomena here and there. Several standout sections detail the rationale for certain geoscientific practices. For instance, in a chapter about facing down a cartel to retrieve her beloved rock hammer, she writes, “To a field geologist, a good rock hammer is indispensable. Seeing the inside of rocks, the parts free from the ravages of weather and time, is how we discover their true nature. Since we don’t have x-ray vision, the rock hammer makes understanding the heart of the those very solid objects possible. I often joked that if I couldn’t fix a problem with my rock hammer, it couldn’t be fixed.” The book tracks Jess from Death Valley to Hawaii to Ecuador, Mexico, and the Explorers Club in New York City. I think this would be a great book to gift to an adventurous teen with an orientation toward nature. As she gets into and out of hot water, Jess explains her thinking and rationale. I think it would be a good guide for a young person keen to participated in the world and in need of role models to emulate. Though Jess didn’t win her political campaign, she’s still out there today, working hard to expand everyone’s access to understanding their home planet. This takes many forms: expeditions for student researchers via her nonprofit Blueprint Earth, her prominent advocacy on social media and in periodicals and journals, television appearances, and now: a book!

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16 February 2021

Deep Time Reckoning, by Vincent Ialenti

Stereotypically, I think of anthropologists as scholars who head off into years-long sojourns embedded with indigenous peoples, learning their cultures, practices, and insights. Vincent Ialenti has shown me that modern anthropologists can study other groups too. Ialenti’s population of interest is a modern group of European geoscientists, nuclear engineers, and planners. Together, they are charged with planning for the integrity of a Finnish nuclear waste repository. But studying this group, called “the Safety Case,” has led the author into a non-traditional direction. His dissertation research inspired him, for his subjects thought about time differently from “normal” people. Geologists won’t find this shocking, to think in Deep Time – both backward and forward over millions of years, but it appears to have been profoundly insightful to Ialenti. He reworked his anthropological documentation into an unusual book that simultaneously attempts to report on the nitty-gritty of a very specialized academic study but also spin off grand lessons for humanity at large. I picked it up for the latter, but was willing to indulge in the former. I felt the book was at its strongest when it articulated a vision for the future where Deep Time thinking is integrated into educational curriculum, if not into the wider culture, but the academic anthropological descriptions of Finnish bureaucrats didn’t engage me as much as Ialenti appears to think it should. Similarly, the end-of-chapter exercises in practicing Deep Time thinking (which he calls “reckonings”) didn’t feel especially novel to me, but I am a geologist who is quite comfortable toggling back in time to the Cambrian, or forward 10 million years into the future. I’m probably not the target audience because I’m already sold on the main conclusion, and I would be curious to hear whether novices find these activities mind-expanding. I agree with Ialenti’s premise: that our species and our world benefit if we think about the very, very long-term consequences of our actions or inactions. Replacing short-sightedness with looooooooooooong-sightedness is an unalloyed benefit, I’d argue too. How can we be responsible ancestors to the future of our species; the future of life? Deep Time Reckoning comes at this question from a unique direction, and offers clear guidance for our common future.

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14 February 2021

Under a White Sky, by Elizabeth Kolbert

Elizabeth Kolbert’s third book is now out! Under a White Sky is “a book about people trying to solve problems created by people trying to solve problems.” These problems are environmental problems – they are instances of nature becoming less natural. As humans build cities and plant crops and make waste, we alter the world we live on, the ecology we live within. In Kolbert’s previous book, the Pulitzer Prize-winning The Sixth Extinction, she examined ongoing crises with ocean acidification, invasive species, and novel diseases, all set against the geologic context of extinction, and the causes of mass extinction trauma in Earth’s deep history. Under a White Sky continues that work, but the direction of Kolbert’s gaze is different. The new book’s attention is focused instead on attempts to intentionally alter the future. From genetic engineering to pest control and nurturing of endangered species to carbon capture and solar radiation management, she examines strategies being taken by some humans in our world to try and make the planet of tomorrow better than it would otherwise be. Like all of her writing, the new book strikes a readable balance of background, reportorial anecdote, interviews with leading thinkers, and clever wordplay. It’s a delight to read, informative across a wide range of anthropogenic environmental issues and various attempts at solutions. This is a book about the Chicago River, the Devil’s Hole pupfish, the Greenland ice sheet, and calcite filling basaltic amygdules. It’s about coral spawning and gene drives and forest albedo and volcanic eruptions, and how all of these things are case studies in the human control of nature, in the continued existence of human civilization on this planet, and the other species with which we will be sharing our altered planet. Recommended.

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5 February 2021

Friday fold: a new 3D model

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 a thin section, and of course I can’t ask Declan any more, so its 3D beauty will just have to speak for itself.

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