Advertisement

20 October 2017

Friday fold: Kink folds in Glacier National Park, part II

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 one:

There’s more where this came from – stay tuned for more…. and in the meantime, Happy Friday!

Comments/Trackbacks (0)>>



18 October 2017

VGFC 2017: Limbs of arkose

This past weekend was the annual Virginia Geological Field Conference, hosted by Piedmont Virginia Community College, with a field trip led by Chuck Bailey, Megan Flansburg, Katie Lang, and Tom Biggs. We examined the geology of Albemarle County, Virginia, the county that surrounds Charlottesville. This is the Blue Ridge province; the county spans its width almost exactly. We began on the east limb of the Blue Ridge Anticlinorium, traversed its basement rocks (exposed in the middle of the big fold) and ended on the western limb, adjacent to the northern terminus of the Blue Ridge Parkway and the southern end of Shenandoah National Park.

If there was a theme for the day, it was “arkose.” There’s a lot of feldspar-rich sand that was deposited in central Virginia during the Neoproterozoic. Though the formations vary, the (meta-)arkosic flavor carries through the Lynchburg Group. A few examples:

Here’s a boulder contrasting the typical lichen-encrusted outer surface with a fresh face:

We visited the Mechum River Formation (worth a blog post in its own right since it appears to be glaciogenic), but I didn’t taken any new photos on Saturday.

There were also a few fine-grained units, like these lovely pelitic metasediments, now hosting substantial garnets:

At a highway entrance ramp I’ve traversed dozens of times without stopping, I got to examine pelitic layers within the arkose. Here you can see the contact as an arcuate feature dipping to the right in the photo:

…Zooming in:

Here’s that contact annotated, in case it’s a wee bit too subtle:

The pelite here has been metamorphosed to a phyllite, and bears small crenulated wrinkles:

Even the arkose at this site had a phyllitic matrix, as you can see from the tilting back and forth of this cut and polished sample:

At another site, we saw an unusual combination of finely interbedded arkosic sand and graphitic phyllite:

Whatever the depositional setting was for these sediments, there was a lot of organic carbon getting added to the mix. A “bayou” type setting with distributary channels was hypothesized as one explanation.

Cut samples and fresh rock from the site, the first showing the arkose mixed with graphite rich beds at the base:

More graphic, but still sand dominated:

Here’s one dominated by graphite with a lesser amount of intercalated sand:

Nothing but graphite:

At the final stop up on the Blue Ridge itself, we saw coarse arkosic sediments within the Catoctin Formation, which is otherwise dominated by greenstone (meta-basalt):

Contact between medium and coarse grained dark gray arkose:

Here’s the contact between the greenstone (below) and the arkose above:

It appears to be unconformable on the basis of the wiggly, undulating contact, but the facing indicators were insufficient to convince me that I could tell which way was paleo-up. So I’m not sure if this is the bottom of the arkose or the top (and then bedding was overturned, which is something reasonable to expect in the western Blue Ridge). Annotated:

I have a few more images from the trip to share, but they have a different theme, so I’ll save them for another post.

Comments/Trackbacks (4) >>



16 October 2017

After On, by Rob Reid

It turns out that Rob Reid can write. This “novel of Silicon Valley” is a tour de force of writing. Reid shows off his chops at writing potboiler adventure stories, ironic Amazon reviews, and sparkling dialogue. It’s a story of Silicon Valley culture, of start-ups and venture capital and social navigation in the Bay Area, but it’s also a novel that explores artificial intelligence (AI) in a fun, engaging way. Much of the material covered in Life 3.0 or Our Final Invention is explored here in an approachable, character-driven fashion (James Barrat even gets a shout-out by name!). The decisive strategic advantage (see Bostrom’s Superintelligence for more details) that the world’s first AI gets is an interesting plot point to the story, as the world’s first AI is more interested in matchmaking (which she is astonishingly good at, considering she has access to all the world’s data). The book explores quantum computing, augmented reality, the casual erosion of privacy, self-commodification of services, bioterrorism, genetic engineering, the ethics of publishing sensitive data, generation of fake audio and video, government surveillance, and much more. The setting is today – and it very much feels like a novel of this moment in history. It won’t feel as fresh ten years down the line, because all the references and plot devices hinge on the tools in our pockets right now, the capabilities of our computers right now, and I guess also the things our computers cannot yet do – but will be able to pretty soon. So read it soon! The characters are brash, brilliant, and often stressed out. They act like us, having the conversations we’re having. The difference is that as they’re innovating and grappling with office politics, an AI emerges from the Facebook/Groupon/Google/Tinder/Apple-like company that they work for. The whole set-up is simultaneously a commentary on modern American techno-life and an adventure story. It was very enjoyable. I listened to the audio-book version, which was lively and exceptionally well produced. If you can’t stomach a nonfiction book about AI, you may find After On more palatable. I was very impressed with the book overall; I know I’m going to read more by Rob Reid in the future.

Comments/Trackbacks (0)>>



13 October 2017

Friday fold: ptygmatic vein from Finland (NMNH)

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 a pronounced foliation. Note the cuspate “flames” of matrix between the broad “lobes” of folded vein. These two materials were behaving quite differently at the time of folding. It’s a lovely sample.

And I hope you have a lovely weekend.

Comments/Trackbacks (0)>>



11 October 2017

Pompeii vs. Herculaneum

What’s missing from this picture of Pompeii, outside of Naples in west central Italy?

I’ll give you a hint: here’s a photo of nearby Herculaneum:

I visited both sites this summer, and was struck by some of the differences.

First, what they have in common: Both towns were satellite Roman communities that were snuffed out in AD 79, when the volcano Vesuvius erupted violently. Those residents who didn’t escape during the early stages of the eruption were buried. Almost two thousand years later, their remains may be viewed in the context of the archaeological sites their towns have become.

The difference between the two photos above is that at Pompeii, excavations have removed almost all the pyroclastic material (ash and lapilli) that killed the people and preserved the town. At Herculaneum, much of it remains in place. While Pompeii pokes out into the air as you might expect a village to, Heculaneum feels like an excavation: it’s a hole in the ground. The walls of that hole are pyroclastics that the surrounding city have been constructed upon.

Today, let’s explore both sites together.

Some images from Pompeii:

There are plenty of vantages of Vesuvius, the great threat, off in the distance.

It’s a beautiful place – hauntingly beautiful if you think about what happened here.

The roads and floors:

Some art from Pompeii:

Building materials varied, but included thin bricks and blocks of travertine, here accompanied by vesicular basalt for artistic effect, and also a block of carved marble (modern) for the sign:

In some places, the basalt (quite common in the area because of the neighboring volcano) dominates:

Blocks of travertine  show the external molds of plants growing adjacent to the spring:

Full body casts of the dead at the Garden of the Refugees:

These striking forms resulted when human beings (likely slaves) were buried by a pyroclastic flow. The pyroclastics were already meters deep at the time of their demise, and their masters had likely fled the city. The slaves’ bodies rotted away over time (save for some bone material) and yet the surrounding envelope of ash had enough structural integrity to remain standing and preserve the shape of their bodies. Later infilling of this external mold with plaster of Paris created a cast of the original three-dimensional shape of their bodies.

The cast of a child who died almost two millennia ago:

Two millennia later, a child examines the lapilli that entombed this city:

This is the only pyroclastic material I observed in Pompeii; everything else must have been cleared away – and a tremendous amount of it, too. It seems to me that there is a missed opportunity for some geological education here. By seeking not to obscure the gorgeous archaeological features of Pompeii, the geological “murder weapon” has been removed from the scene.

Herculaneum, in contrast, sits in a hole in the pyroclastic deposits, surrounded by urban greater Naples:

Vesuvius can be seen looming in the distance here, too.

Here’s a room (now missing the wall closest to us, and the roof), where you can see dune-scale cross-bedding moving in from the former door (on the right) to fill the interior (on the left):

Zooming in on the cross-bedding:

Annotated to show the flow direction:

Herculaneum also preserves the bodies of the dead, but here they are skeletons.

These macabre remains are in a series of boat shelters at the former harbor of Herculaneum: the low archways along this wall:

It’s a sobering view.

One of the striking aspects of Herculaneum’s archeology is the preservation of carbonized wood at the site. Here is a bed that still persists, 2000 years after it was built: absolutely remarkable!

Some of this wood remains in architectural position, holding up walls and ceilings (though now reinforced with modern additions):

Along the walls of the excavation pit, you can see additional buildings, not yet revealed. The lapilli and fragments of the carbonized wood are crumbling into the open pit:

Some art at Herculaneum:

Differential weathering of blocks of yellow tuff, relative to the mortar that holds them in place:

Finally, here’s a stone* mill for making flour, one of two located in a bakery in Herculaneum:

*porphyritic vesicular basalt

Both sites are extraordinary windows into the past. They offer views of life during the heyday of the Roman Empire. Each has its strengths. Pompeii is enormous. We walked its streets for six hours in the blazing sun and hardly visited the same spot twice. Herculaneum (the excavated portion, anyhow) is much smaller – only a few blocks. Visitors have greater liberty to enter the buildings at Herculaneum, and it’s less mobbed by visitors. For these reasons, coupled with the visceral sense of being in the volcanic deposit, I think Herculaneum was the more powerful visitor experience. Ideally though, a stronger sense of how this violent day went down can be achieved by visiting both sites in tandem.

Comments/Trackbacks (1)>>



9 October 2017

Braiding Sweetgrass, by Robin Wall Kimmerer

Braiding Sweetgrass is a collection of thematically-linked essays by Robin Wall Kimmerer, an environmentalist, academic, and Native American. The themes that unite them are plants, the human relationship to the natural world, and love.  I’ve read Kimmerer’s essays in Orion before, but there’s a sort of literary force multiplier when you get a whole book full of her thoughtful insights, story after story, back to back.  Braiding Sweetgrass is a work that reminds me of Annie Dillard’s or Barbara Kingsolver’s nonfiction, with the additional flavor of indigenous insight woven (or maybe “braided?”) in. The key aspect of this indigenous insight is a consciousness of the human role in a larger dynamic ecosystem – the valid and valued role that human beings can engage in if they choose to, to the benefit of both their own selves and the natural world as a whole. For instance, in a section about a basket-making lesson, Kimmerer recounts how the students had dropped scraps of ash wood (long fibers called “splints”). In describing her teacher John’s reaction, she says:

In a circle around each novice is a litter of scraps. [John says] “Stop and think what you’re holding. That ash tree was growing out there in that swamp for thirty years, putting out leaves, dropping them, putting out more. It got eaten by a deer, hit by a freeze, but it kept working year in and year out, laying down those rings of wood. A splint fallen on the ground is a whole year of that tree’s life and you’re about to step on it, bend it, grind it into the dirt? That tree honored you with its life. There’s no shame in messing up a splint; you’re just learning. But whatever you do, you owe that tree respect and should never waste it.” And so he guides us as we sort through the debris we’ve made. Short strips go into a pile for small baskets and decoration. The miscellaneous bits and shavings get tossed into a box to be dried and used for tinder. John keeps to the tradition of the Honorable Harvest: take only what you need and use everything you take.”

As with basket-making, this is excellent perspective to maintain in Life In General. But Kimmerer is a plant scientist too, and she shares fascinating research about how human harvest of black ash actually helps (rather than hurts) the trees’ population, one of those counter-intuitive revelations from ecology that remind us why we practice the scientific method instead of just assuming we know what’s going on with the world.

Kimmerer’s locations in the book are mainly centered in upstate New York, but there’s also time spent in the deep South, the Pacific Northwest, and other spots. Her career has had her travel, and she has relevant experiences accrued in each location, even if the woods and lakes of New York are her home.

The writing is eloquent and evocative. I was particularly taken with her description of Pacific salmon feeling the urge to quit the sea, head inland, and spawn:

Far out beyond the surf they felt it. Beyond the reach of any canoe, half a sea away, something stirred inside them, an ancient clock of bone and blood that said, “It’s time.” Silver-scaled body its own sort of compass needle spinning in the sea, the floating arrow turned toward home. From all directions they came, the sea a funnel of fish, narrowing their path as they gathered closer and closer, until their silver bodies lit up the water, redd-mates sent to sea, prodigal salmon returning home.

That’s just great description, but I feel Kimmerer really hits her stride when she’s make explicit connections between the natural and human worlds. (Of course, she sees these two as the same, or they should be the same, but she also knows she’s writing for an audience of humans who have been cut off from deep connection with the natural world through their own choices or Society’s.). Here’s Kimmerer on the Umbilicaria lichen, for instance:

The first drops [of rain] splatter hard against the rigid surface of rock tripe, which instantly changes color. The mud-brown thallus becomes sprinkled with clay-gray polka dots, the tracks of raindrops, which deepen over the next minute to sage green, like a magic picture developing before your eyes. And then, as the green spreads, the thallus begins to move as if animated by muscle, stretching and flexing as the water expands the tissue. In a matter of minutes it is transformed from a dry scab to tender green skin, as smooth as the inside of your arm. … Where the umbilicus anchors the thallus to the rock, the soft skin is dimpled, with little wrinkles radiating about its center. It looks to all the world like a belly button. Some are such perfect little navels that you want to kiss them like a little baby tummy. … As the lichen gets older, it becomes asymmetrical, the bottom half as much as 30 percent longer than the upper, a legacy of lingering moisture that permitted it to keep photosynthesizing and growing after the top half was dry and still. The trough can also collect debris, the lichen equivalent of belly-button lint. … Event the tiny thalli are dimpled with navels. How fitting that this ancient being, one of the first forms of life on the planet, should be connected to the earth by an umbilicus. The marriage of alga and fungus, Umbilicaria is the child of earth, life nourished by stone.

The book’s longest essay is on the legacy of pollution in Lake Onondaga, but others focus on harvesting maple sap for syrup, the different kinds of fire, teaching students in the Great Smoky Mountains, motherhood, rescuing salamanders, and climate change. There’s plenty of diversity of topical material, but her treatment is consistent – both the natural ecosystem and people do better when we cooperate. It behooves us to learn the ways of nature, and to envision a role for our own species to play in that larger system.

Recommended.

Comments/Trackbacks (0)>>



6 October 2017

Friday fold: recumbent isoclinal folds in Saruratown Mtn window, NC

Here’s a cool fold pair that rolled through my Twitter feed today:

Joe Allen gave me permission to share it with you here. Here’s the photo with bedding traced out (by me)  in yellow:

Happy Friday, all!

Comments/Trackbacks (0)>>



29 September 2017

Friday folds: soft sediment deformation in thin sections of MTD sandstone

For your Friday fold delectation, I offer you these GIGAmacro images of thin sections of the exquisite mass transport deposit (MTD) above the Spechty Kopf Diamictite (latest Devonian) in the exceptional roadcut just east of the Alleghany Front along Corridor H in Hardy County, West Virginia. This was a package of interbedded sand and mud that collapsed into deeper water en masse, deforming internally as it went. This is soft-sediment deformation, not post-lithification tectonic deformation. We dubbed the folded sandstone bodies “ploudins,” as they were sort of half “pillow” (as in ball & pillow soft sediment deformation) and part “boudin” (as in boudinage). Explore the ploudins’ internal structure these enormous images of the slides under plane and cross-polarized light. Search for graded bedding, cross-bedding, folding, faulting, organic debris (carbonized plant scraps), and maybe even a zircon or two. These images are Flash-based, so if you don’t have Flash, you can’t see them. Enable Flash on your browser, or click the “link” after each one to go to a non-Flash source page.

Here’s an annotated “cheat sheet” to guide your eyeballs on the first one:

These slides were prepared by John Weidner, a former math professor and a dedicated volunteer in our department.

Here’s a GigaPan of slide JW46 under cross-polarized light:
Link 2.19 Gpx GIGAmacro by Robin Rohrback & Callan Bentley

Here’s a GigaPan of slide JW46 under plane-polarized light:
Link 2.71 Gpx GIGAmacro by Robin Rohrback

Here’s a GigaPan of slide JW45 under cross-polarized light:
Link 2.10 Gpx GIGAmacro by Robin Rohrback

Here’s a GigaPan of slide JW45 under plane-polarized light:
Link 3.22 Gpx GIGAmacro by Robin Rohrback

My former student Maddy Rushing and I have been working on a characterization of this outcrop which we plan to present at GSA in Seattle next month. We’re using these sort of images as well as some other new digital toys to more fully describe and interpret the outcrop, in particular the Spechty Kopf Diamictite, which appears to be glaciogenic. But once you throw in plant fossils, changing oxidation states, and a mass transport deposit, it all starts to look a wee bit more complicated. Another volunteer in our department, Sarah Yun, has just completed a new suite of thin sections of the diamictite’s massive and laminated members. I can’t wait to show them off! If you’re available, Maddy’s talk on this work is Monday at 4:55pm in Bryan Turner’s and Shannon Dulin’s mud rock session. Please come!

Comments/Trackbacks (0)>>



22 September 2017

Friday fold: bend in a vesicular lava flow, Etna

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 this feature), but I think we can appreciate it regardless:

Comments/Trackbacks (0)>>



20 September 2017

Make It Stick, by Peter Brown, Henry Roediger and Mark McDaniel

This past spring, when I attended the InTeGrate workshop called “Teaching About the Earth Online,” one of the participants recommended the book Make It Stick, by Peter Brown, Henry Roediger and Mark McDaniel. Months later, the volume finally moved up in my reading queue to the top. It’s a fascinating account of the empirical research about how people successfully learn. I found it absolutely engaging and stimulating, in particular the first several chapters. Much of how we think about learning and teaching is based on myth and lore, and several widely-deployed practices are not supported by scientific study.

The book’s big revelation for me is that testing (or quizzing) is a learning strategy. Durable learning results from effortful “retrieval practice.” Educators like me can embrace this realization by frequently deploying scheduled low-stakes quizzes, either before or right after the lesson, and giving feedback. If “before the lesson” sounds bizarre for the scheduling of a quiz, that’s exactly why you should read this book. Many of its lessons are counter-intuitive. But research shows that struggling with a problem before being taught how to do it, while frustrating, actually results in better assimilation of the lesson once the instructor teaches it. This is the beauty of the Make It Stick philosophy: Hard work is hard. But it works better than illusory learning that feels easy. The standard practices of re-reading chapters and highlighting them over and over and cramming before the test may feel like you’re learning, but you’re really just building familiarity with the text, or your lecture notes. This is called “massed practice,” and the authors of Make It Stick assert that you should stop wasting your time on it immediately.

Another shocking revelation along this same theme — “make it difficult” — is that if the text that a student is reading is made slightly blurry, or is presented with a word missing out of each sentence, the extra work that the brain has to do to make sense of the text actually results in better understanding of the concepts, and better recall. How crazy is that? Professors and teachers, you should make a special effort to present lecture material in a different order than the textbook presents the material. The extra effort students have to make to parse the different orders forces them to discern the underlying concepts rather than just a clever turn of phrase their professor puts on the book’s content.

Failure should be embraced as part of this process, but we need to change how we think about it. It’s not a reflection of the student’s inner worth or inability, but a curve in the road to success. Envisioning failure this way, as something to be accepted and conquered, is essentially an attitude change. It becomes a tool for mastery, an essential experience that should be looked forward to — and learned from. Perseverance in the face of failure is key to success. Failed tries are useful information to the dedicated learner.

The book’s chapters are written in a good mix of anecdote and peer-reviewed empirical research. Two of the authors are education researchers, but the lead author, Peter Brown, is a storyteller and writer. The stories he tells to open each chapter range in focus from business people to surgeons to pilots and sports coaches and active duty military. In each case, there are elements of each protagonist’s story that illustrate a key lesson from educational research, with the descriptions of the actual studies following the more compelling human tale. There’s rather more sports talk than suits a non-sporty person like me, but even I could choke it down.

The second half of the book was less compelling to me, perhaps because I was already familiar with some of the ground it covered: the Dunning-Kruger effect, Bloom’s taxonomy, the fraught idea of Multiple Intelligences & learning styles, memory palaces and other mnemonic devices, the general psychology/neurology of learning. However, the final chapter ties it all together with specific advice for various populations (students, teachers, trainers) and that I saw as a really useful distillation of the book’s main lessons.

Students, for instance, will be reminded that their number one strategy for more effective studying is not re-reading the chapter with highlighter at the ready but instead to initiate a program of self-quizzing. Making mistakes is to be an expected part of this process, so long as the students learn from those mistakes and refocus their efforts on the portions of the material where their performance is sub-par. Use a quiz such as the “Concept Checks” or end of chapter review in the textbook, or make up your own quiz. Convert the key points into questions, and then answer them. Syntax gets too much attention; you should focus on the underlying precepts. As you read, pause every couple of chapters and quiz yourself on what you just read. This will seem slow and clunky at first, but the effort you expend will be rewarded. More effortful recall results in a better-trod pathway of the mind, and more durable learning. Review your self-quiz results and do it again. And again. Write your answers out for real, don’t just dismiss a given question with “Yeah, I know that one.” Space your effort out in time, and mix it up with other related activities. Elaborate on the ideas you learn; don’t just parrot the same language in which the book presents material. Fluency with the text generates an illusory sense of mastery – but you don’t want to know the text. You want to master the underlying ideas.

All told, I think Make It Stick is going to revolutionize the way I teach; in particular with regard to frequent scheduled low-stakes quizzing.

Comments/Trackbacks (1)>>