17 February 2017
Garnetiferous beds from the aureole of the Leinster Granite east of Baltinglass, County Wicklow, Ireland (Declan De Paor’s senior thesis mapping area, 1973). Manganese-rich metasediments. The prominent ‘elasticas’ or fan folds (folds with a negative inter-limb angle) are superimposed on isoclinal folds: so the brownish layer at top and bottom are the same, though that is not obvious from the image. This is a sample from the structural geology collection of Declan De Paor and Carol Simpson.
Take a look at the whole sample in this GigaPan. If you don’t have Flash enabled on your computer, you’ll have to click through to explore it:
Link 0.58 Gpx GIGAmacro by Callan Bentley
15 February 2017
With the current political climate being what it is, I’m newly motivated to learn the best way to communicate science with the American public. I’ve decided to read several books on the topic that I’ve been aware of for years, but not yet made time for. The first is Randy Olson’s Don’t Be *Such* a Scientist. Olson has a unique perspective to apply to the question: he was a tenured professor of biology before quitting academia and moving to Hollywood to make movies. He knows how academic scientists talk, and he knows how Hollywood tells stories, and the two are really different. More to the point, one works for communicating with the general public, and the other slams the door in their faces.
Key points: Science is a negating profession, and communicating that way comes off as condescending. We scientists are in the business of nurturing fledgling hypotheses, only to slaughter them with facts both blunt and sharp. Karl Popper’s ‘falsifiability’ is the name of the game – we love to find the holes in arguments, the flaws in studies; our prestige is enhanced when we can find new and clever ways of saying “no, that’s not how it works.” This brutal crucible of negation leaves the strongest ideas standing, and we can trust in their robustness relative to weaker notions. But when a scientist takes this inherent negativity into general conversation, it comes off as grouchy or disdainful. I was thinking of this myself the other day when a friend who’s concerned about climate change emailed me a link to an article about the lengthening crack in Antarctica’s Larsen C ice shelf. Olson’s book made me see my response (“I wouldn’t see it as a major scary item by itself though – this is what ice shelves do – ice gets added ‘upstream’ by glaciers, and it “ablates” (breaks off) downstream. People seem to like big dramatic events though, and this is charismatic enough to grab folks’ attention!”) as an example of this negative sort of reaction. I essentially pooh-poohed her engagement with the story of the growing crack in light of my understanding of ice sheet dynamics. In retrospect, I wish I’d engaged differently – it was an opportunity missed for participating in a discussion.
We need to be conscious of where we are pitching out stories. By “where,” I mean where in the human psyche. Olson proposes a “Four Organs” theory of science communication. Metaphorically, we respond to communications with our (1) heads, (2) hearts, (3) guts, and (4) sex organs. Scientists communicate with other scientists head to head, but if you want to reach the general public, it’s more useful to frame your message in terms of an emotional appeal (heart) or humor (guts). Appealing to sex is the most widespread human approach, but it’s so jiggly and disorganized down there in our gonads that it’s difficult to communicate a coherent message. So Olson aims his science stories below the neck but above the belt.
Stories are good. I knew this intuitively, but Olson makes the point well by recounting the construction of his film Flock of Dodos, and how the first several cuts of the movie elicited weak reactions from his screening audiences. He then re-cut the film with an archetypal narrative (“hero saves a damsel from a dragon”) and the audiences found it much more compelling and enjoyable. This is a lesson I pledge to apply going forward. At the very least, I’m going to experiment with it where I can.
A corollary of the ‘make it a story’ edict is that you need not make it a story and have it be a textbook. He examines several films on the same topic (global warming, in this case) and qualitatively compares their information content to their emotion and humor content. While scientists are very interested in information, they value fact-heavy films over fact-light films. But Olson suggests that if there is no “heart” or “gut,” then the fact payload will never be delivered, as a general audience will be bored and change the channel. But a non-scientist audience knows what it likes, and it finds much more of a connection to films that speak from (and to) the hearts and guts of the audience, and the actual amount of information involved really doesn’t matter to them. This is a distinctly non-science conclusion to come from – and it makes me feel astonishingly uneasy to contemplate communicating in that way. That’s why Olson’s book is useful: it forces our community of science communicators to examine ideas that wouldn’t otherwise occur to us, in hopes they might prompt a change in our practice.
If you do science communication, you should read Olson’s book.
13 February 2017
Time for another episode of “you ask the questions”… After posting a Google Form to allow anyone to submit questions anonymously last week, I got some excellent questions/topics submitted. I’ll try to get to a couple per week!
3. Why does the Massanutten Mountain not run the whole length of the Valley?
Some background: the questioner is asking about the mountain ridge system where I live: Massanutten Mountain and the Fort Valley. It is situated in the middle of the much larger Shenandoah Valley, a valley in a mountain in a valley. This is a question about geomorphic expression of the Valley & Ridge province of the Appalachian mountain belt.
So the question is why doesn’t this…
…look like this?…
Google Earth, modified by me!
Basically, it boils down to how “deep” the Massanutten Formation dives into the Earth.
The Massanutten (Tuscarora equivalent: a big thick package of Silurian quartz sandstone) is a sheet of sedimentary rock. It is a ridge former because it’s dominated by quartz: a hard, chemically-stable mineral. In the Shenandoah Valley, it overlies the Martinsburg Formation, a mix of shale and graywacke sandstone. It is overlain by Devonian limestones and shales. Where the Martinsburg Formation crops out, it weathers away relatively rapidly, making a valley. The same is true for the Devonian limestones and shales. But where the Massanutten Formation crops out, it weathers away more slowly, leaving a ridge.
The strata of the Valley & Ridge are folded, and the base of the Massanutten Formation dives into the Earth at the mountain’s northeastern end and re-emerges at the southwestern end. It’s like the bottom of a canoe:
This is the situation with Massanutten, too:
Massanutten is doubly-plunging synclinorium: an overall canoe-shaped fold that plunges down and inward in the “bow” and in the “stern.”
The one spot where the base of the Massanutten blips up above the land surface is about 2/5 of the way along the range, at New Market Gap, where Route 211 crosses over:
But under the Fort Valley, the bottom of the Massanutten Formation is buried deep in the Earth, and everywhere else (surrounding the mountain east and west, north and south) in the Shenandoah Valley, the bottom of the Massanutten Formation is above the surface of the Earth – or rather, it was, prior to erosion. The “canoe” used to be longer, in other words, and it’s getting whittled away over time. As the differential weathering proceeds on the landscape, the gap at New Market Gap will enlarge, and the Massanutten Mountain system will shrink and shrivel. Eventually, the deepest part (under the central Fort Valley) will be exposed, as a lone ridge, and then it too will succumb to the forces of erosion.
Summary / short answer: Massanutten Mountain isn’t longer because the tough stuff it’s made of has been eroded away everywhere else.
4. When will man walk on the Sun?
This is not going to happen.
There are a couple of issues.
First up: humans cannot walk if they are too hot. The Sun is too hot. The ‘surface’ of the Sun is around ~10,000 °F. That’s about ~9,900 °F hotter than you can take. You’d die before you could take a single step, much less go for a walk. But let’s say you got over the big discrepancy between your comfortable temperature range and what the Sun has to offer. What then?
The Sun is 333,000 times more massive than the planet Earth. So think of how quickly you hit the ground when you trip and fall here on Earth. If you were to stand on the Sun, your mass would be the same, but because the Sun is so much more massive than Earth, the gravity there would be much, much, much much, much, much, much, much, much, much, much, much stronger. In fact, it would not be advisable to attempt to go and see if you could walk on the Sun, because you would pretty much never be able to get away again. So you should know going in, this is the last trip you’re ever going to take. Even if you reconciled yourself to that, your muscles are going to be far too weak to take a single step away from the surface of so massive an object.
And finally, there is the issue wouldn’t be a ‘ground’ equivalent to walk on. The Sun is a big ball of plasma, and I think you’d have a rough time walking on it. It’s not a solid. Now, the average density of the Sun is ~1.4, while Earth is ~5.5, and your body is ~1.0. So your body would be less dense than the Sun’s average, but don’t think that’s a guarantee of ‘floating’ in the uppermost solar plasma. The Sun is roiling with convection, which means that your average non-flammable, impervious, super-strong Joe who steps foot on the Sun is likely to be caught up in one of these convection cells, and quickly pushed toward one of the downwelling zones. Just as convection in a pint of Guinness can drag bubbles (of low density) downward, I wouldn’t count on your relatively low density to save you. Convection is another risk of attempting to walk on the Sun.
So, bottom line: this is not going to happen. Sorry!
Got a question to prompt a bit of discussion here? Use this Google Form to allow anyone to submit questions anonymously.
10 February 2017
Steve Mirsky, an editor at Scientific American (he does their “60 Second Science” podcast), loans us some photographs today for the Friday fold.
Steve took these images in the Grand Canyon, Arizona, on a trip that the National Center for Science Education runs every summer:
Based on where he took them, I think these in the Tapeats Sandstone, base of the Paleozoic sequence that makes up most of the Canyon’s celebrated walls. I wouldn’t expect much folding in that unit, but Garry Hayes has documented some, and it appears to be of a similar character. If anyone knows differently, then please let me know.
Thanks for sharing your fold photos, Steve. Happy Friday, everyone!
9 February 2017
Do you remember the blog post four years ago about documenting the doomed outcrops at Scientists’ Cliffs, Maryland?
It was the site of gorgeous Miocene fossil exposures in the Calvert Formation.
Here’s what the site looks like now:
Photo by Peter Vogt
That ugly thing at the base of the cliff is a gabion, protecting the houses on the clifftop and making fossil access impossible. I’m glad we got there before it was “protected”…
8 February 2017
I’ve always been fascinated by parasitism. Parasites are organisms that live on or in another organism (or organisms) in a way that detracts from the vitality of the host. Nothing in nature is redder in tooth and claw than the parasite. They represent a stark repudiation of the naive way many people think of evolution, with humans at the pinnacle, with a historical sense of purpose or progress, and with the morality that might imply. Parasites live in highly specialized ways, and they harm they leave in their wake is more personally palpable as a result. They exist, as we all do, to propagate their genes to the next generation, and the destruction they cause along that path can be macabre and fascinating. As Charles Darwin put it in a letter to Asa Gray,
I cannot persuade myself that a beneficent & omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of caterpillars, or that a cat should play with mice.
The ichneumons Darwin refers to are wasps that sting caterpillars (or spiders, depending on the species) to paralyze them. They stash the living but still bodies in secret burrows or chambers, and lay an egg or a dozen on them. The wasp larvae hatch and eat the host alive, saving the vital organs for last so the meat is fresh. Imagine being paralyzed and eaten alive, feeling those hungry grubs chewing away at your flesh and being unable to do anything about it, until finally, when your bodily larder is emptied, you’ve outlived your usefulness to them, and they burst through your skin to live out their destiny. It’s a horror show, and it shows decisively that natural organisms don’t exist as exemplars of moral purpose. They don’t live to comfort us. They exist to reproduce, and if they have to go through you to do it, they will.
There are even nematodes that parasitize the parasitic wasps, and other parasitic wasps that protect their conquered caterpillar by hatching two varieties of offspring: (1) reproductively viable individuals, and (2) others that basically exist only as booby-traps to kill other species of parasitic wasps that might happen upon the caterpillar smorgasbord post-paralyzation. The body of a caterpillar is a brutal battleground. It’s fascinating the learn about.
Lucky for us that Carl Zimmer has written the book Parasite Rex (2000), a survey of all things parasitic. Like everything Zimmer touches, it’s awesome science and awesome writing, leavened with a bit of personal anecdote and humor. I really enjoyed it. Chapters examine the societal (mis)appropriation of parasites as a political analogy, the relationship of parasites and the immune system, how parasites can drive evolutionary change, and parasites’ social and economic effects on humanity. Along the way, we get insights into the detailed physiology and biochemistry of dozens of parasitic organisms and profiles of the scientists who study them. One surprising point the book makes in an excellent and convincing way is that parasites can have beneficial effects on a host organism, and even to the functioning of an ecosystem.
Did you know that Plasmodium vivax (the little protozoan that causes malaria) and intestinal worms together rob humanity of 80 million “life-years” annually? Did you know that parasites are the majority of species on Earth? Did you know that some parasites take control of their hosts’ sex lives, castrating some and performing sex-changes on others? Dig into the deep ecology of Wolbachia and its peers by reading Parasite Rex, and feel your jaw drop in horrified wonder.
7 February 2017
Today, let’s journey to Iceland, to a bit northwest of Reykjavík. This is a view from the top of the Grábrók cinder cone, across the valley to the east.
With very few exceptions, Iceland is a big pile of basalt, and that shows through in the walls of this valley, which display a stack of basaltic lava flows, intercalated in places with pyroclastic debris or volcaniclastic sediment.
One portion of the far wall of the valley shows some discontinuities in the layering:
I had a satisfying few minutes puzzling over multiple working hypotheses for this observation. Is there a fault along that little green gully? How best to explain the highly inclined basalt layer to the right of that? What to make of the grayish granular pocket in the middle? (I’d be curious to hear your reactions, if you’d care to record them in the comments below.)
The valley appears to have glacial influence, on the basis of U-shaped “hanging valleys” that feed into it, but the bottoms is relatively flat, which may reflect a heavy sedimentary “backfiling” of the valley post-glaciation, as with the Yosemite Valley in California. A river runs through it today, with several channels that merge and bifurcate:
Take a look at the whole scene in this GigaPan. If you don’t have Flash enabled on your computer, you’ll have to click through to explore it:
Link 0.55 Gpx GigaPan by Callan Bentley
See if you can find: (a) the “fault” site I discussed above, (b) a hanging valley, (c) a river channel, (d) columnar jointing, and (e) an outcrop showing at least five sequential basalt flows.
6 February 2017
Over the weekend, I launched a new initiative on Facebook to assist my friends in learning about scientific matters that they are interested in. I want to serve society in combating science illiteracy, and I think one way I can do that is to solicit questions or topics from those who want to learn more, and use those as a springboard for discussion. It’s time for me to let my social media network including you, dear reader, drive the content of the blog. I’ve set up a simple Google Form to allow anyone to submit questions anonymously.
Here are the first two questions, and my responses:
1) Why do geologists get so excited about folds?
This is a question that is entirely within my wheelhouse, since folded rocks are one of the most prominent features of this blog. I think I find them so fascinating because they are so counter-intuitive to basic human experience. I mean, here is a rock, a solid thing that would hurt us if it hit us on the head, and yet it clearly displays evidence that it has flowed as a soft, putty-like substance. To reconcile these two facts, we have to think beyond our normal experience. This is what science is so useful for, of course – systematic, empirical study allows us to escape our quotidian Ape Brain and come to terms with nature as it really is. Much of what science has revealed is counter-intuitive: Continents move. The Earth orbits the Sun. Our ancestors were fish. Quarks exist. The universe is vast.
When we allow the rocks to deform under higher temperatures than we can handle, at pressures much greater than we can survive, or for time spans much longer than our ephemeral lifetimes, the stiff, hard rocks can behave in astonishing ways. Rocks can flow. I think folds show this most clearly, though metaconglomerates and shear zones make the point in a different way. The realization that rocks can flow is fundamental: It’s a thought that forces us to change our assumptions about physical conditions, about the passing of time. It allows us to conceive of mantle convection. It allows us to imagine the formation of mountains as a dynamic process. It’s essential to understanding how the Earth works.
2) Why are some people born with tails, excessive amounts of body hair, and even what appears to be animal hands and feet?
The short answer to this one is “humans are animals.” We are creatures of flesh and blood, made of the same atoms and programmed by the same genetic code, as everything else on Earth. Ultimately, every living thing on this planet is a relative, though some are closer relations than others. Humans are apes, descended from tree-dwelling shrew-like critters, which were descended from hairy reptiles, which came from amphibians, which are basically fish that learned how to walk. We bear the marks of this extraordinary ancestry in our bodies. Our skeletons are built on the same basic body plan as every other mammal, but modified to allow us upright posture and big brains. It’s not a perfect arrangement: women’s hips are barely big enough to accommodate massive-headed babies to be born. We are plagued by lower back pain due to the S-shaped curve in our spine that animals like chimpanzees or hyenas lack. But in spite of the less-than-ideal tweaks that make use unique, the shared affinity is hard to dispute:
One of the most fascinating classes I took in college was Developmental Biology, the study of how a single fertilized egg grows into a whole organism, with many diversified cell types. Though developmental biology is not my professional specialty, I think I can make some general comments toward answering the question. In our mothers’ wombs, embryos grow according to tried-and-true developmental routines, mediated by biochemistry. The amount of hair is a function of how much the genes for hair growth are “expressed” (that is, copied and enacted by enzymes). People that have a lot of hair might (1) have genes that say “lots of hair” or (2) they might just have vigorous expression of the same genes that in someone else might result in less hair. So there are the instructions (genes) and then how frequently those instructions are read and enacted (regulation). We probably carry all sorts of genes that were useful to our non-human ancestors that are now “along for the ride” without being expressed as active blueprints for our development. Other inherited genes might be doubled-up or tripled, and that extra expression might result in very different effects in humans compared to non-human animals. So a gene for making hair follicles for instance, might be increased or decreased, to dramatic effect.
Another factor to consider is the presence of biochemical gradients. The length of toes, fingers and the backbone may be controlled by biochemical gradients that run from front to back (or top to bottom, or left to right). Let’s say there is some hypothetical chemical that is more concentrated toward one end of the growing embryo than the other end. When the concentration of this chemical (shown in purple in the sketch below) is high, the developing embryo starts making “head” stuff by turning on “head” genes, but if the concentration is low, the “head” genes are kept quiet, and instead, “tail” genes are turned on.
The embryo stops growing one of these body parts when its chemical surroundings change. There are dozens of ways that could happen, but let’s just imagine what happens when something goes wrong, and the chemical gradient is altered in some way. Maybe it’s too strong, or maybe it fades off sooner than it should, or maybe it increases, then decreases, and then increases again. The development of the embryo will react to those changes, and toes might be too short as a result, or the pieces of the tailbone might tack on additional material, extending them to be longer than they would otherwise have been. Giraffes have the same number of vertebrae in their necks as humans do; they’re just a lot longer. Or perhaps the number of pieces of tailbone can be changed. Repeating segments is an easy recipe for evolutionary variation. Just ask the centipede, the boa constrictor, or the polycheate worm.
If there is some environmental change, it too could alter the gradient, or the reception of the growing embryo to the gradient. For instance, there is a medication called thalidomide that pregnant women used to take to combat morning sickness, but it changed developmental conditions so that many of their children failed to fully develop their arms and legs, being born with paddle-like appendages instead. The addition of something like thalidomide alters the developmental environment, and this is why it’s so essential for pregnant women to protect themselves from substances which would hurt the embryo’s development.
The tailbone (coccyx) is basically the end of the spine, and it shows the same pattern as the rest of the backbone: a series of segments analogous to vertebrae, but tapering off to a point. Depending on who you look at, you may find three segments to the tailbone, or four, or five, fused together to a greater or lesser degree. This variation is a reflection of either the genes of the individual, or else variation in the strength of some developmentally-relevant biochemical gradient as the embryo is growing. That variation is an observation which gives us an insight into the source of developmentally-induced variation in humans – the sort of conditions that might result in people having characteristics like those in the question. A non-human example is using the ancestry of the chicken to turn the bird “back” into a dinosaur. It just takes a few tweaks on what’s already there to create something that looks a lot more like a Compsognathus than a dinner.
The diversity we see in our human brothers and sisters is a reflection of our collective animal ancestry. It shouldn’t surprise us to see that some people have tails or extra hair, because we are descended from animals that had lots of hair and had tails. What would be truly weird is if something showed up that wasn’t in our evolutionary heritage: an unprecedented novelty like a set of wings growing out of our backs, or antennae sprouting from our foreheads. Don’t hold your breath for either of those to show up any time soon.
That’s all for this first installment of “Q&A.” If you have a topic you want me to explore, use the Google Form to submit your questions anonymously.
3 February 2017
Today’s set of Friday folds comes from just south of the Time Zone Bridge in the Canyon of the Salmon River, Idaho.
Can’t see them very well in that view? Very well, let’s switch from a perspective looking down on the plane of foliation to looking along the plane of foliation…
The rocks are mapped as the Squaw Creek Schist, a common unit near Riggins.
Basically, the edge of ancestral North America can be found in here. Folds exposed the Squaw Creek Schist are a result of the stresses of adding terranes onto North America’s westward margin. When Pangaea formed in the late Paleozoic, North America was moving relatively eastward, causing deformation and metamorphism along its eastern edge (the Appalachians). When Pangea broke up, North America started moving westward, opening up the Atlantic Ocean in its wake, as well as smashing into various terranes (chunks of crust) along its new ‘leading’ edge, the west. These terranes started off as oceanic crust, or island arcs, or microcontinents, out there in the wide Pacific Ocean (recently formerly known as Panthalassa). Multiple lines of evidence suggest that western Idaho was the “cowcatcher” on the front of the proverbial train. The Squaw Creek Schist could be thought of tectonic “roadkill” splattered onto the front of this continental Amtrak. As the continent thundered westward, it accumulated quite a bit of crustal debris all over its front bumper. Today we call that “Washington state,” and “Oregon.”
Here’s another nearby outcrop with a 3D exposure of a crenulated fold train:
These rocks were a stop on the excellent field trip I did looking at the accretionary tectonics of western Idaho, following the Rocky Mountain Section meeting of GSA last May.
2 February 2017
Today, let’s return to the Barberton Greenstone Belt in Barberton Mountain Land, South Africa. I visited there in late August of last year, and documented some of the extraordinary Archean rocks exposed in that place. The Barberton GeoTrail on the road called R40, which runs from Barberton to the Swaziland border is a great place to introduce yourself to some of the varieties of rocks that can be found here.
One lovely unit is this banded iron formation.
(There’s a pretty big difference in the vibrancy of the red depending on whether the sun was shining or not.)
Banded iron formation is a rock type that no longer forms on planet Earth. To get hematite and magnetite to precipitate onto the ocean floor, you first need to have iron dissolved in the seawater. This is hard to do if you have free oxygen in any quantity, the iron will react with the oxygen and precipitate out. So BIF is in fact a rock that records the local oxidation of iron, but that implies more or less global absence of oxygen, for the iron to be in solution in this quantity in the first place.
So BIF is evidence of a different ocean chemistry than what we have today, and that implies a different atmospheric chemistry than we have today. Like komatiite, it’s an “extinct rock” on our planet, evidence of a radically unfamiliar planet’s primordial operations.
The particular outcrop that’s “the BIF stop” on the Barberton GeoTrail also features some pronounced folding, which may represent soft sediment deformation. Here are few examples:
Here are two GIGAmacro looks at the front and back of a sample of BIF I collected in Barberton. You’ll need Flash to view these here; otherwise click through to see a non-Flash-based version of the image. Compare the layers of hematite to the layers of chert and jasper for yourself:
Link 0.52 Gpx GIGAmacro by Callan Bentley
Link 0.63 Gpx GIGAmacro by Callan Bentley