19 October 2018
Today is another reader-contributed Friday fold:
Here are three from my Master’s work in the Brooks Range. My field area was the West Fork of the Atigun River, in the Brooks Range, Alaska.
I note that these images carry a special charm, since they are scanned from slides. That’s the way we used to take field photos, kids!
Riia’s descriptions follow…
Photo A12 is of the ridge labelled Fold 2A and Fold 1 A on figure 3 of the attached paper, and is approximately located at 68.245509, -149.521162 (according to GoogleMap’s “what’s here” button).
Here is the figure she references:
Zooming in on the fold:
Annotated to show the trace of bedding in red:
Photo E14 is of the set labelled Fold 1B, 2B, 3B on that figure, and is approximately located at 68.240801, -149.550688
Zooming in on the folds:
Here’s my armchair annotation of that one – Hopefully I’ve sussed the trace of bedding out correctly!
Photo H23 is of the segment of the Kayak Shale just north of the label “Panel B” in that figure (approximately 68.244300, -149.541418), and shows parasitic folds that are only visible in perfect lighting conditions. That photo was taken from camp, and most days that summer that was a featureless black hillside.
Zooming in on the folds:
And, a set of annotations, showing the trace of bedding in white:
Thanks for sharing, Riia!
Other readers: Do you have cool folds to share with the Mountain Beltway audience? If so, shoot me an email to share them: cbentley at nvcc dot edu. Thanks in advance!
Happy Friday to all. Enjoy the weekend.
17 October 2018
Mark Kurlansky might be the king of the micro-history. His books Salt and Cod were both excellent examinations of history in the context of those minerals and fishes. So when I saw The Big Oyster on the audio-book shelf at my public library, I checked it out, knowing roughly what I would get – a history anchored to that particular delicious mollusk. In this case, it’s a history of New York City specifically. This is a little crazy if you’ve been to New York lately, but Kurlansky maintains that back in the day, about 200 years ago, New York’s waterways – the Hudson River and the East River and the various bays – contained half of the world’s oysters. They were apparently legendary for their size and flavor in addition to their profusion. Middens attributed to the Lenape, a Native people, and their predecessors show huge oysters at the base of the piles, some 8 to 10 inches across, and then a decrease in size going upward, as the best were harvested and consumed first, and more marginal specimens taken only when nothing better could be gleaned. That prehistorical trend presaged the eventual destruction of New York’s oyster beds through overharvesting and (more importantly) pollution.
I learned some fun facts in the book, like the fact that the word “cookie” comes from the Dutch settlers of New Amsterdam, and that it was one of the few terms that stuck around after the British took over. (“Biscuits?” No thanks!) Or that “Catskill” (as in the Catskill Mountains of upstate New York) referred to streams with bobcats and mountain lions near them. I learned that you can train an oyster to keep shut (“clammed up”?) in order to make him/her last longer on shipment to markets far from the shore. I learned about sustainable oyster cultivation using nothing more technologically advanced than a rowboat and some tree branches. I learned about Charles Dickens’ predilection for oyster bars, about the relationship of oysters to the ‘gangs of New York‘ in Five Points as well as to the robber barons of the gilded age. Kurlansky can tie oysters to political movements and prostitution and ecological insight and the canal industry. It’s all there! But the essential messages of the book are gustatory and environmental, I’d say.
There are parallels between The Big Oyster and William Warner’s Beautiful Swimmers (about blue crabs in Chesapeake Bay), but Kurlansky’s book is all third-person, holding the subject at arm’s reach. I really appreciate it when an author like Warner (or John McPhee) gets up close and personal with his subject, reporting first hand on experiences or conversations. This book lacks that.
It’s not a perfect book. As usual, I can find geological errors in almost any text. (It’s a curse!) One that glared in The Big Oyster was Kurlansky saying “65 million years ago, when humans first began evolving,” which is monstrously inaccurate. There were no primates 65 million years ago, much less any hominins. There were human ancestors, but they were rodent-like things, and they hadn’t “just” begun evolution; their had been at it since the beginning of life on this planet. Aside from relatively minor errors like that, another issue I had with the book was the excessive recounting of oyster recipes, which became absolutely maddening with repetition. Kurlansky lays out something like 2 or 3 dozen historical ways of preparing oysters, when half a dozen would have made the point adequately.
That said, I never knew anything about this essential aspect of early New York. It was the oyster capital of the world for a long time, and that legacy has helped shape the city that remains in the post-oyster era.
12 October 2018
Another guest Friday fold (keep ’em coming, people!) – this time from my friend and colleague Russ Kohrs, who shares these images from his family camping trip last weekend.
This one is called “The Devil’s Backbone:”
Down the road a ways, there was this:
Since the first one was an anticline and got dubbed “The Devil’s Backbone,” maybe we should call its neighbor, a syncline, by an opposite name. “The Angel’s Xiphoid Process,” perhaps? That’s certainly got a lovely ring to it…
Anyhow, Russ reports:
So, my wife took these images yesterday morning on our way back home from a two night getaway in Pocahontas County, West Virginia (which, by the way, is replete with fabulous exposures!). I’m sure you’ve seen and, probably, even used the “Devil’s Backbone Anticline” in your Friday Folds posts, but the other one was just a bit down the road – and, I think, it’s Martinsburg/Reedsville, just below the Tuscarora in the anticline.
Thanks for sharing, Russ. I welcome people submitting Friday fold photos to me. Get in touch if you’ve got some!
11 October 2018
It’s time for a new reader-submitted question. This is part of a periodic “you ask the questions” feature here on Mountain Beltway. Anyone can ask a question, serious or spurious, and I’ll do my best to answer it here. Use the handy Google Form to to submit your questions anonymously.
This one gets personal:
8. What impassions you about Structural Geology?
Actually, someone else asked that too, a few months back:
9. What got you interested in geology? What is your story behind your passion for geology?
My answer to these questions comes now as we head toward Earth Science Week next week, an annual celebration of geoscience, facilitated by the American Geosciences Institute (AGI). This year’s theme is “the Earth as inspiration,” and I think that’s my short answer to the questions above. I think geology in general, and structural geology in particular, is inspiring.
The thing that I think first drew me into structure was the beauty of patterns.
I’ll show you what I mean, using the most general of terms: chunks, bumps, lines – before I had jargon to apply to these facts of nature, I could at least appreciate their shapes and colors…
For instance, a high-contrast pattern like this: Why are there dark chunks in light colored stuff? Why do they have those shapes?
What does that pattern mean? What does it have in common with the one we see here?
Or here’s another one, with cool colors in addition to chunks of different shapes:
Why are the chunks we sometimes see more rounded and internally massive, while others show precise internal geometries that parallel their overall shape?
Or let’s consider this gradational pattern, light to dark: What is the light-colored stuff telling us? What is the meaning of the dark stuff? Why does the light transfer crisply and utterly to dark in some places, but then they smoothly fade into one another at other transitions? …
Here is another example of that same pattern, but now the direction of the grading is reversed. We can make the observation, and we can ask “Why?”…
Or what about lines? I’ve seen some cool looking lines out there…
Sometimes lines are lines in their own right (as in the two examples above), and other times they are the intersections of planes with the face of the outcrop, as here:
Some of those planes I learned to call “beds.” Others I soon came to name as “fractures.”
The fractures appeared to have gotten soaked with stain-inducing fluids sometimes:
These stains could be quite beautiful in their own right, even once liberated from their in situ positions that spoke about the power of those fractures to conduct fluid flow:
And rusty water isn’t the only fluid that can flow through a rocky crack: sometimes a seam of totally different rock can be found there, igneous rock in a tabular mass we call a dike. Where these students in this photo now hike, was once a deep injection of thousand-degree molten rock:
Sometimes these can even cross one another, and an order of cracking, and magma injection, can be discerned:
Photo by Victor Zabielski
That is a pattern! “… X marks the spot.”
Sometimes color could draw me in. Here are a few examples, in red and green:
And what about lumps and bumps? Here are some that are more or less tongue shaped:
Here are some that are squiggly:
And here are some that appear to be circles on one view …
But viewed from a different angle, they appear to be cylinders or tubes:
These patterns that entranced me had three dimensional form; they called me in to examine them from more than one angle, to crane my neck, pull out my hand lens, crawl into caves, climb cliffs. A single glance doesn’t show the whole story, I learned.
Speaking of things that look different in different manifestations: What about this pattern, these “scalloped edges?”
The more these patterns drew me in, the more I learned about their cause, and what linked them to other varieties, like these:
Photo by Bob L’Hommedieu
All in all, my point of entry into geoscience, and one of my sustaining sources of inspiration, is this wealth of cool-looking patterns in the natural world. I could cite hundreds of other neat outcrops, beautiful hand samples, or patterns glimpsed only through a microscope, or through satellite imagery, or through LiDAR – but these photos I have shown will suffice for now. My deepest wellspring of inspiration is these observations with their distinctive geometries, textures, colors. And unlike clouds shaped like bunnies, or Rorshach blots, or grilled cheese sandwiches that show the form of the Virgin Mary, these are patterns which can be decoded – they are patterns that carry meaning. They are not fodder for pareidolia, “random noise” upon which our brain extracts a pattern that only exists in our own minds. These are the record of processes, events – actions that have transpired in the past of our planet. If you collect these patterns, and tally them up, and keep track of how they relate to one another, you can tease out a story, the story of a planet through time.
Our planet writes its autobiography in (jargon alert!) breccias and dikes, conchoidal fractures, porphryoblasts and trace fossils, flute casts and megacrysts and graded beds and slickensides, hackle fringes, amygdules and Liesegang bands. Though those words may seem alienating to the neophyte, you’ve just looked at a dozen photos of them. They are the record of the Earth’s past. They are the language that Earth uses to communicate her story; when we learn the meaning of these messages, they entice us to learn more about our home world.
What do you find inspiring about this planet? Or the science which helps us understand it better? Share your inspirations in the comments below.
If you have other questions you would like me to answer about science, the Earth system, or anything else, please ask them.
5 October 2018
A Friday fold from the legendary region of Cinque Terre, on Italy’s northwest coast:
This comes to us courtesy of my friend Callan Swenson – yes, there’s another Callan out there! – who’s there this week on vacation. This is near the village of Vernazza. The Other Callan is not a geologist, though, so we’re on our own to figure out the story of these outcrops. From a quick investigation online, it looks like this is a region where the Ligurian nappes have deformed the local rocks. There are ophiolites further to the north, but these appear to be a package of turbidites. Unfortunately, I can’t squeeze much useful information from the 1:1,250,000 scale Geological Map of Italy online. Oh well, chances are that at least a dozen of this blog’s reader have been to the site, and can share their knowledge in the comments below… Please, enlighten us!
(And: Happy Friday!)
28 September 2018
A guest Friday fold rolled into my email inbox last Friday. It’s a beaut!
This is an anticline in the Big Cottonwood Formation, exposed in Slate Canyon, just east of Provo, Utah:
It comes from reader Octavia Spencer, who writes:
The attached photo is one of several I took while hiking a canyon near my house in Utah. I wasn’t able to include a scale object because the photo was taken from the opposite side of the canyon, but my best guess from looking at maps and satellite images is that it’s probably about 500 ft across. The rock is pre-Cambrian quartzites and slates.
As a non-geologist, I’d like to say how much I appreciate your blog, by the way. Often when I read geology blogs I find the illustrations really confusing; they’ll post a picture that says “Look at this amazing example of a [name of feature]!” without indicating where it is in the photo or how I can tell it apart from everything else. (Admittedly, I may not be their target audience.) I love that you take the time to put lines, arrows, etc. on your photos and explain them clearly and unambiguously, so that even an English major can understand what you’re talking about.
Thanks for sharing this cool photo of a cool fold, Octavia, and thanks for the laudatory comments about the power of annotations to “show what a geologist sees.” Happy Friday!
21 September 2018
Here’s a lovely sight, contributed by reader Fred Atwood:
Those are quartz veins in one of my favorite local rock units, the Mather Gorge Formation. Fred reports,
This is at Madeira School in Great Falls between Black Pond and the Potomac.
The rocks around Great Falls, particularly those on the Billy Goat Trail’s “A” Loop, are exemplary in many regards. That’s why I am taking my Physical Geology students there next month. Of relevance to understanding Fred’s video is that there are two generations of quartz veins in these rocks: (1) a pre-late-Ordovician set, which were ductilely deformed during the Taconian Orogeny (local metamorphic ages ~464 Ma), and (2) a post-Taconian set, which are undeformed, cutting across their crumpled predecessors. The latter set of veins, whose traces appear as straight white lines on the rock outcrop surface, are gold-bearing, but that’s not the case for these “folded oldies.”
I guess we can console ourselves that they have something even more valuable than gold to share: beautiful deformation! sublime wiggles! classic contortions! uplifting undulations!
Thanks for sharing, Fred; Great outcrops!
19 September 2018
The talented science writer David Quammen has a new book out, and it’s excellent. The Tangled Tree explores endosymbiosis and horizontal gene transfer, two aspects of evolution that undercut the traditional ever-more-branching “tree of life” vision for the relatedness of living things. The lineage of organisms is not only divergent, but convergent too: populations diverge and sometimes merge, in whole or in part, complicating the traditional “ramose” structure of phylogenetic trees and evoking a more “reticulate” (net-like, or “tangled”) shape. The reality, revealed by the last 150 years of science (specifically molecular phylogenetics), is that especially for microbes, ‘mergers and acquisitions’ take place regularly, with huge implications for both public health and our understanding of evolution. Specifically, these insights allow us to re-conceive the source of genetic novelty that natural selection can then play with, as well as the actual (past-tense) history of life, including the line of descent that led from microbes to us. This is a history book, a history of the development of ideas, pushed along by interesting scientists who uncover interesting information about the history of organisms. It is a story of people, people who figure things out, who make new knowledge. It’s remarkable in that sense, very much focused on humans going through the process of science, rather than merely the empirical results of their work. These people collaborate and fight, synergize and snipe. I came away from reading it with a much better sense of who Carl Woese was, who Lynn Margulis was, who Ford Doolittle is. These people are essential in the story of how we came to understand who we are as a species, and Quammen is to be commended for his thoughtful, sympathetic rendering of their human essence. He’s a great writer: methodical, erudite, curious, measured. He consciously skips unnecessary information, and lets you know he’s doing it – this editorial sense of efficiency is much appreciated. At the same time, nothing feels rushed. Key notions, the ones that are really worth delving into, really get delved into! The book is written with a gentle redundancy, circling back just frequently enough to remind its readers of key ideas, figures, or data. There’s a lot to keep track of, and I appreciate this “reticulate” structure of the narrative. What’s more, Quammen has a Dan Brown-like talent for ending each chapter with a cliffhanger or teaser that leads directly into the introduction of the subsequent chapter. It’s delicious reading about a fascinating topic. Recommended.
14 September 2018
Today, I dug into my photo archives looking for folds that (I think) I haven’t shared before, and came across these two, from the beginning of the R40 road outside of Barberton, South Africa, on the road that leads up into Barberton Mountain Land, and toward the border with Swaziland.
The rocks here are sedimentary layers, and they show some relatively minor folding: Honestly, they’re pretty pristine for Archean aged deposits of mud, silt, and sand!
13 September 2018
Yesterday, I finished listening to the audiobook version of A New History of Life, by Peter Ward and Joe Kirschvink (2016). This book is only a couple of years old, and takes as its topic ‘the modern perspective’ on life’s long history on Earth, using the latest insights available. It aims to debunk old hypotheses that don’t stand up to new data, and to expand the purview of life’s reign on Earth beyond the Phanerozoic and flesh out its Precambrian details. It also argues for expanding life’s purview beyond Earth itself – both way back when with a planetary perspective on why they think life began on Mars, and also for the future, as they forecast the eventual demise of planet Earth to due the inevitable hostility that comes with solar evolution. Another major focus is on ‘greenhouse mass extinctions,’ the principal subject of another Ward book I consumed recently, Under a Green Sky. Ward and Kirschvink put true polar wander into Earth’s history along with the Snowball Earth glaciations, and they suggest that the first of these was unleashed by the CO2 drawdown associated with the O2 buildup of the Great Oxygenation Event – the first of ten (not five) mass extinctions in the record of life on our planet. This is a book that really emphasizes oxygen’s role in steering the fate of organisms, both positively and negatively. The authors invoke oxygen time and again as they discuss bird air sacs, dinosaur eggs, and big Carbonifeous dragonflies. Ward and Kirschvink manage to summarize and synthesize a tremendous amount of insights from the past few decades, including papers from their own careers and fields of interest, and others that are outside their professional wheelhouses, but that they gleefully delve into in their book. This is a jargon-heavy book, so it’s not going to be as useful to a novice as to someone like themselves – a professional interested to see what the current thinking is on everything that’s being presented in all those GSA meeting sessions that you don’t have time to get to. I found it an impressive work and I’m grateful to the authors for compiling it all in one place. That said, I don’t think I would use it as a Historical Geology textbook because of the high level of its writing – it assumes a fairly substantial incoming knowledge base for its readers, and pulls no punches when it comes to taxonomy or biogeochemistry. Another, minor, note: if you read it, go for the paper book version rather than the audiobook. I listened to the Audible version of it, and I lost several mm of enamel off my teeth from gnashing them every time the narrator mispronounced a word. The audio narration really could have used some “p(ear) review” before being published!