Words’ worth IV

Back on the first incarnation of this blog, I occasionally posted about words that bugged me. A few more have piled up since then, so here we go with the latest consideration of “words’ worth”…

First off, let’s consider the use of “outcrops” as a verb. This came up recently on this blog when commenter Tom Skaug pointed out that I was incorrectly using that term. He’s right of course, and has the dictionary citations to prove it. Technically, we should say that a particular rock unit “crops out” on a hillside. Mea culpa. I appreciate the correction. That being said, I know a lot of geologists who speak as sloppily as I write. Using “outcrop” as a verb is reasonably common slang in my circles.

Next, let’s consider some plural words. When reviewing an article recently, I saw the words “maximums” and “minimums” written out by a science writer. I suggested to the editor that these should be “minima and maxima” instead. The editor countered that real people (i.e., non-scientists) don’t speak that way, and that the accepted parlance among the general public is just to tack an “s” on the end of a word to make it plural. However, in Latin, the language that gives us these words, the plural would end with the addition of an “a.” When you look it up in a dictionary, both plural forms are listed. To add insult to injury, my computer’s automatic spell-checker function is putting the red zigzag under my correct Latin versions, and NOT underlining the “-s” versions. I’m beset on all sides!  Still, to me, “minimums” sounds clunky and clumsy, while “minima” is elegant and sleek, like a well-designed scientific instrument.

Okay, here’s another one. Occasionally, graffiti appear on the walls of the bathrooms here at the community college where I teach. When I spot a new scrawl, I write an e-mail to the cleaning staff alerting them to the vandalism. But what do I do when there’s just one little new jotting? Graffiti are plural; the correct singular of this Italian word is “graffito.” But that sounds vaguely ridiculous, right? “Dear Cleaning Staff, There is a new graffito in the men’s bathroom on the east side of the Shuler Building’s second floor.” I feel silly, and maybe a little pompous, if I use the correct singular form of this word. Anybody else have a word like that, where they know how to use it correctly, but they use it incorrectly on purpose for the ease of communication? (…Or possibly to avoid offending someone?)

Along similar lines, data are plural, while datum is singular. Most scientists are comfortable discussing a single datum, and are careful to only use “data” when there’s more than one chunk of information being discussed. But the general public doesn’t parse this distinction as finely. You’ll see “data” used to refer to what really is a lone datum.

Natural gas – I was thinking about this one while driving into work the other day, and the radio newspeople were talking about that big explosion a few weeks ago in San Bruno, California. It got me thinking about the term “natural gas.” What a dumb, non-descriptive term. I mean, do we ever refer to “natural liquid” or “natural solid?” Natural gas is annoyingly non-specific. I get it: it’s a cocktail of different gases, mostly methane, with a dash of ethane and maybe a few other volatile compounds too. If it were pure methane, we would call it “methane,” but it’s often not pure. It’s a mixture. So we can’t call it just “methane,” because that wouldn’t be accurate. The mixture occurs naturally, so we call it natural gas. We trade specificity for meaningless but accurate inclusiveness. Blech. The role of “natural gas” as a fossil fuel is ascendant; we’re going to be talking about it for some time to come. I think we need a better name for the stuff. Suggestions?


Today I’m in the air, on my way back to Turkey for the Tectonic Crossroads conference being held in Ankara next week. Before the meeting, I’m joining a field trip to examine a subduction zone complex. Over three days, we will drive from Istanbul to Ankara by way of ophiolites and blueschists and other geologic wonders. I’m excited. Hopefully I’ll be able to post an update or two from Turkey, but I don’t know what my internet access will be there. I’ve also got a couple of short pieces in the pipeline to post automatically, so you won’t go into withdrawal while I am out of town.


* Get it, like it’s my second time sampling the flavors of Turkey? “Leftovers?” Like the day after Thanksgiving? …Funny, right? …Right?

Speleothem microscopy: soot & aragonite

My friend Dave Auldridge, formerly a structural geology student of mine at George Mason University, is now in grad school at the University of Alabama. Dave is working on an interesting project with speleothems: those drippy looking CaCO3 growths that you find in caves, like stalactites and stalagmites. He’s looking at these speleothems in order to determine paleo-climate with oxygen and carbon isotopes. The carbon soot that’s trapped in the speleothems provides a novel mechanism of constraining the age of the different laminations which comprise the feature.

The other day, Dave sent me some neat images from his research, and when I expressed enthusiasm and appreciation, he gave me permission to post them here. All these images are from stalagmite #4 (DSSG-4), DeSoto Caverns, Alabama. The are all imaged with a scanning electron microscope (SEM), which is why there is no color, only texture.

The first image shows a nugget of carbon soot that, according to Dave, is “probably common cane, that fell off an Indian’s torch ~1000 years ago.” The cave where this stalagmite was collected was used as a Native American burying ground. Prior to going into the SEM, the sample has been acid washed, which means that it has enjoyed a 30-second cold 5% HCl dip.

That’s seriously cool: thousand year old Native American torch ash… inside a stalagmite! Dave reports to me that these carbon laminations suddenly stop about the same time Hernando de Soto showed up in the Southeast with his conquistadors. Then the laminations resume once the cave started getting used as a saltpeter mine. Dave tells me that there’s a little bit of silica in these laminations too — which may be from phytoliths in the cane.

This next chunk may be carbon soot, or may not. Dave adds, it “may be a bug, maybe not…” As with the first image, this sample has been acid washed.

This one shows a coarse spar of calcite, penetrating down into the aragonite. The younging direction of the aragonite is left to right: you can see the bundles branch out in that direction. The sample has been acid washed.

I am reminded of a school of sardines swimming around a whale…

Our penultimate image is looking down on to an up-growing aragonite bundle (inter-fingering of several bundles can be seen). The sample has not been acid washed. Don’t lean too close, or you might scratch your nose!

The last (and most beautiful, in my opinion) is of aragonite bundles cut perpendicular to growth laminations. The younging direction is left to right.

These last two images are incidental to Dave’s research, as no carbon soot can be seen. But he took them and passed them around his research group (and his extended e-mail network of former professors) just as something cool to look at. As he said, “We are geologists, right?” (We like looking at pretty rocks!) As far as he knows, no other speleology research group has cut and imaged a speleothem along a lamination.

Dave’s work used the Central Analytical Facility, which is supported by The University of Alabama.

Deducing my first anticline

When I was done with my sophomore year at William & Mary, I embarked on a time-honored tradition among W&M geology majors: the Geology 310 Colorado Plateau field course. Jess alluded to this same course in her Magma Cum Laude contribution to this month’s Accretionary Wedge geology blog “carnival,” too.

My version of Geology 310 was led by the legendary Gerald Johnson (a.k.a. “Dr J”), a dynamic and enthusiastic educator who seemed particularly at home in the field. One day, he had us out in Utah (I think) somewhere, and pulled over to the side of the road so we could examine some tilted sandstone layers. We took a strike and dip reading, and plotted it on a map.


Then we descended into a narrow valley, where Dr. J did some “geology at 60 miles per hour,” pointing out shale outcrops in a few places in the valley. Then we drove up the opposite side. We pulled over again. Same sandstone strata: we again took a strike and a dip on the beds. The data was then recorded on our maps with a strike and dip symbol, a broad, squat “T” shape, where the upper bar of the “T” is parallel to the strike of the bedding, and the vertical prong of the “T” is pointing in the dip direction.


“Well,” Dr. J asked us, “What’s going on here?”

We were all silent, trying to puzzle it out. What’s the deal? What is he fishing for? Seconds ticked by, and no one had the right answer. We started to sweat… “Um, the sandstone beds are dipping to the west on the ridge west of the valley,” someone ventured, “and they are dipping to the east on the ridge east of the valley?”

“Yes, but what does that mean?” he replied. Silence…

Eventually, he relented, and spelled it out for us. Imagine this situation from the sides, he suggested, gesticulating the layers dipping off in opposite directions. “These are the same layers, so they were once laterally continuous…” He mimed a cross-sectional perspective:


How could we connect these disparately oriented strata together?


Bam! It hit me: I got the idea of an anticline at that point — the idea that a structure like an anticline could be so large that I couldn’t actually see it from my earthbound human-sized perspective, and I could only infer it from detailed measurements of the rock structures. It was a revelation to me: this valley and its surrounding ridges were part of a massive fold. The anticline must have breached in the middle, with the shale eroding away faster than the sandstone, producing a valley flanked by two ridges.

I’m grateful to Dr. J for putting us through all stages of this exercise: collecting the incremental pieces of data, being forced to think about it in an attempt to come up with an interpretation, and then finally giving us the proper interpretation, once it had become obvious we weren’t going to get it on our own. This last bit is particularly important to me as an educator: sometimes it’s okay to spell it out for students, particularly if it’s their first time walking down a particular path. By revealing the “answer,” Dr. J guided my thinking from data to big picture structure to geomorphological interpretation in a way that I can only describe as “opening up a new pathway” in my mind. Once he showed the way to think about this sort of thing, it was suddenly very easy for me to visualize this sort of complicated four-dimensional story. Once the pathway was there, it was almost effortless to let my thoughts flow along that pathway. Weird how one’s perspective can change in a moment, and how that influences everything that comes after.

For me, this exercise and ensuing discussion constituted an important moment in developing my ability to think like a geologist. I don’t think my brain will ever be the same.

Friday fold: Siccar Point, Scotland

As with last week, I’m going to show you someone else’s fold today. This one should have strong resonance with most geologists, because it’s a fold in the tilted (and contorted) older strata exposed below the famous unconformity at Siccar Point, Scotland:


I found this image on the British Geological Survey’s online repository of images, which are available for public use with attribution. I found out about the BGS photo repository via a post on StructuralGeology.org.

The photo was taken by T.S. Bain in 1979. Rock hammer (lower left) for scale.

The specific rock type here is shale, and their age is Silurian. Note the thinning of the limbs of the fold, and the relatively thick hinge area.

Happy Friday – may your workday rapidly thin (like the limbs of this “similar” fold), and your weekend be as thick as this fold hinge!

An unfortunate name

I’ll bet this Turkish children’s clothing company really wishes they had gone with something else for their name…


Building stones of the Haghia Sophia

The Haghia Sophia (or “Ayasophia”) is an astounding building in old town Istanbul. It is an ancient cathedral turned mosque turned museum. Through all these incarnations, the Hagia Sophia has retained some features and had other ones added on: it is a palimpsest of architecture, symbology, and history. Walking through its soaring main chamber, or side passages and alcoves, visitors like me stand with necks bent and mouths agape. It is an unparalleled location for peeling back the layers of time.

Built in 532 CE by the Emperor Justinian, the cathedral rose on the same spot where two earlier churches had stood, the first of which was built in 360 CE. The name “Haghia Sophia” comes from the Greek for “holy wisdom.” For more than a thousand years, it served as the principal church of the Byzantine Empire. It was the world’s largest cathedral for thousands of years. The minarets were tacked on in 1453, after Constantinople fell to the Ottoman Empire:


There’s a gazillion aspects of this building to discuss, but today I’d just like to share some images of the different building stones seen in and around the Haghia Sophia. To start with, here’s a “Verde Antique” (serpentenite breccia) sarcophagus outside the building:


The floor stones in an interior hallway, worn smooth and shiny by millennia of human shuffling:

And a bunch of shots of stones used in the interior walls …

Granite (verging on unakite?):




Rhyolite porphyry:


Rhyolite porphyry with xenoliths (also used to construct a sarcophagus outside):


Marble gneiss:


Darker granitoid:


There are also some structurally interesting rocks, like this red and white marble breccia that shows pressure solution. Notice the sutured boundaries of the white grains, and their pronounced long axes, 90° to that maximum pressure direction.

Kind of reminds you of the Purgatory Conglomerate, right? (Me too.)

My favorite rock there is this lurid, gory red/white/black marble gneiss, as it displays ptygmatic folding (elsewhere it is also boudinaged):

I wish I had more photos of this stuff. It’s great. It reminds me of guts!

Here it is in a typical display (pardon the blurriness of the photo): they “fillet” the rock and spread it open in the manner of a Rorschach blot. This produces an attractive symmetrical design, with minimal artistic effort:

Another nice “butterfly” spread, this one of folded marble gneiss:

Another one:
Look close at this one. Note the little gray crosses in there? Let’s zoom in…

Here’s one closer-up:


These are ancient Christian crosses, or rather, the holes where ancient Christian crosses were once mounted on the wall. When the Haghia Sophia was converted to a mosque in 1453, these Christian symbols were removed, and the holes cemented over to obliterate traces of the old religion. Here’s another one, where the cement has fallen away:


Along similar lines, here’s some Arabic script carved into the railing of the second floor, marring a lovely marble breccia:

Stuff like this just floors me. I mean, think about all the different people to lean on this railing over the past 1500 years. The Haghia Sophia’s history is so deep, with so many distinct overlapping layers. The mind reels…

A fantastic concentration of building stones may be found at the “Coronation” spot on the main floor of the building, where Byzantine kings were crowned:






After several pleasant hours touring the Haghia Sophia, we got lunch at a great cafe nearby. Lily got lentil soup:


…and I got an amazing pide, the Turkish style of “pizza”:


Delicious rocks followed by delicious repast! Can’t complain…

EARTH: the biography, by the BBC

Last week, I watched the BBC/National Geographic series “EARTH: The Biography,” hosted by Iain Stewart.

Stewart is a charismatic host, with a thick Scottish accent that cannot disguise his enthusiasm for geology. The five episodes focus on: volcanoes, ice, oceans, atmosphere, and “rare planet.” Overall, I thought the series did an good job covering some of the greatest stories in geology with an emphasis on presenting the latest ideas. Snowball Earth gets screen time, for instance, and the ocean-anoxia hypothesis for the end-Permian extinction, too. They also cover ocean acidification, a topic I feel deserves wider press.

The series is well-produced. Stewart zips all around the globe, and the editors seamlessly incorporate imagery from other BBC series (like Planet Earth) as supporting content where appropriate.

Here are some of the tidbits I gleaned from the show:

Two billion tonnes of the Andes are carried down the Amazon every year (in the form of sediment weathered and eroded off the Andes). Along similar lines, 40 million tonnes of dust from the Sahara Desert are dumped on the Amazon Basin every year. I wonder if the Sahara dust is included in their sediment volume estimates, or whether it is deducted since it’s not of Andean origin. Great statistics regardless.

They tell the story of Joesph Kittenger in the atmosphere episode. He did a skydiving jump from 90 miles up! After free-falling through almost the entire Earth’s atmosphere, this crazy dude lights up a cigarette! Those were the days.

Four million tonnes of the Sun’s mass are converted into energy every second. Whoa.

Humans now move more rock and soil than all natural processes combined. Ergo: Anthropocene.

The Mediterranean Sea loses three times as much water to evaporation than it gains from rivers and rain. Without the Straits of Gibraltar to let in Atlantic water, it will dry up (and it has dried up, multiple times in the past). In illustrating this, Stewart goes into a salt mine beneath Sicily and shows some BEAUTIFUL contorted salt laminae. Worth watching the whole series just for those gorgeous patterns. (here’s one shot)

The footage of Fayetteville Green Lake in New York is excellent — this is a deep lake with pronounced internal stratification of water and not much mixing — the deep parts of the lake have become anoxic and euxinic (enriched in H2S). They illustrate this by diving into it and the water turns PINK. It is presented, of course, as an analogy for one of the leading models for the end-Permian extinction: global ocean euxinia. It is astonishing to see pink water, and enticing to think about, but the show commits a major “fail” when they don’t tell what this substance is, or where it comes from. They describe the water as having “something deadly” in it, and then say it’s a “highly toxic poison,” or “a gas as deadly as cyanide,” but never do they (a) call it hydrogen sulfide, and (b) explain that it comes from certain kinds of bacteria that thrive in low-oxygen waters. Another complaint: they don’t say when the Permian-Triassic extinction occurred, just the same old saw about it being the “greatest” extinction in Earth history, and that it occurred “before the dinosaurs.” The word “Permian” is never used.

I have some other criticisms, too…

The phrase “a blink of an eye, geologically” is used too often. Twice in the first episode alone!

They show an image of a comet moving like a badminton birdie, with the tail pointing back where the comet came from. This isn’t accurate — comet tails point away from the sun (dragged downstream by the solar wind).

At one point, when discussing the history of life on Earth, Stewart suggests that “life needs catastrophes.” I would argue that life has diversified due to catastrophes, but that catastrophes are not necessary for life to continue. In a non-catastrophic situation, life just perpetuates itself and may exhibit increasing specialization or genetic drift within the parameters available in its environment. But “needing” a catastrophe every now and again? Only if diversification of life is the goal — I take issue with this verb.

In another episode, Stewart is describing convection in the mantle, and says that “magma” is moving upwards. This is false: it is hot rock (a solid), less dense than neighboring relatively-cold rock. The “magma” idea for the Earth’s mantle is a popular misconception which Stewart is opting to elide rather than confront.

At another point, in praising the Moon, Stewart suggests that the planet Earth’s climate would have switching between freezing cold and boiling hot if it were not for the Moon’s influence. No explanation is given for this extraordinary claim. He may indeed have a chain of evidence and inference in mind when he says this, but without a robust explanation, this statement comes off as “because scientists say so”: an authoritative statement with no supporting detail which shows how science comes to a particular conclusion. Worse, he then cranks it up with the future fear factor — they go into great detail about how we have determined that the Moon is drifting further away from Earth over time, and then suggests ominously that Earth will then lose its climatic stability. So now we’ve got alarmism too, but again, no explanation of the supposed causative relationship is given.

Overall, it’s an enjoyable series, and I was pleased to have it to watch when I had the flu last week. Check it out, and let me know what you think.

Champlain thrust fault


Over the summer, I went up to Vermont to visit my friends the Clearys. Joe Cleary is a college friend and a talented luthier. He and his wife Tree and their children Jasper and Juniper have settled in Burlington, a lively town with a lot of cool stuff going on. Joe took time out one morning to show us a superb example of a thrust fault on the shore of Lake Champlain. It is on private property, but Joe got permission for us to hike there first. Our group that day consisted of Joe, Lily, and me, plus by a stroke of good luck, my pal Pete Berquist was in Burlington at the same time, with his friend Amy. The five us were Team Burlington for the day.

There are two rock units involved in the faulting at this location. Consider the first:


This is the Dunham Dolostone. It’s early Cambrian in age. It’s resistant to erosion, and stands up in cliffs above Lake Champlain. The distance from my ten little piggies down to the water is probably fifty feet. Below the Dunham Dolostone, you can find the Iberville shale. It is actually younger than the overlying dolostone. (We know this from unfaulted stratigraphy elsewhere in the region.) The Iberville shales are Middle Ordovician in age. They are relatively weak (‘incompetent’) rocks, and have been sheared out by the faulting. Here, Team Burlington demonstrates the sense of shear, by leaning over in the direction that foliation has rotated towards:


Looking in one direction along the base of the fault to show the differential weathering of the two units:


Flip it around 180°, and you see the same thing in the other direction:


Pete, Joe, and I crawled underneath the ominously overhanging dolostone to check out the detailed structure of the fault. Here’s Pete tickling the sheared out shales, looking for little sigmas…


The shales had nice veins of calcite running through them, and the high contrast of light and dark reveals some lovely folds, like this one:


Pete goes into professor mode, gesticulating and using the verb “shmoo” to describe the reaction of the shale to a gazillion tons of dolostone sliding over top of it:


Another nice fold (little tiny blue Swiss Army knife, 5.7 cm in length, for scale):


And another nice fold:


This fold is transitioning into a shear band:


Here’s my favorite part of the outcrop, a big fold with little parasitic folds all over it, showing opposite senses of shear on the opposite limbs of the big fold:


S-folds on the upper limb, Z-folds on the lower limb. Sweet, eh?

Here, a sort of S-C fabric has developed, with foliation tipped over the the left, and then near-horizontal shear bands running along through it:


Here’s something weird. Perhaps a reader can explain it. Here’s a shot of some of the veins, with the same 5.7 cm knife for scale:


Now we’ve zoomed in, and you can see some detail in the vein:


What are those lines? Is that more “S-C” fabric? I mean, it can’t be cross-bedding in a vein… but I’m having trouble visualizing what process of shearing the vein could yield such a delicate, even distribution of dark material amid the vein fill. What the heck is going on here?

Okay, now that you’ve twisted your brain up thinking about that, you can relax with a structure whose meaning is obvious. Some artistic and romantic previous visitor (not a member of Team Burlington) had arranged pebbles weathered from the two rock units into a bimodal icon of love:


Displacement along the Champlain Thrust is estimated at 30–50 miles (48–80 km). These dolostones started off near the New Hampshire border, then crossed Vermont, almost but not quite making it into the Empire State! The Champlain Thrust is the westernmost thrust fault that has been associated with the Taconian Orogeny, a late Ordovician episode of mountain building associated with the docking of an island arc with ancestral North America. Looking up at the fault trace:


A final glance at the thrust outcrop, looking north and showing the fault’s gently-inclined easterly dip:


Joe, thanks for taking the time to bring us out there!

Guest concretion


This was brought in last week by a student… It’s a broken concretion that she found in Des Moines County, Iowa, many years ago. She also had a slab of limestone with crinoid columnal fossils, and a broken geode from the same locality. I think this concretion is a thing of beauty, like a fossilized Gobstopper. I had to photograph it before I gave it back to her.


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