This is the final post on NOVA Geoblog. From here on out, all my geoblogging will be done at a new blog, "Mountain Beltway:"



I have also started a new "announcements only" blog, which I've given the breathtaking name of "D.C. Geology Events:"


If you're in the Washington, D.C., metropolitan area and you want to keep up on what's happening at venues like the Carnegie Institution or the Geological Society of Washington, I would invite you to subscribe to the D.C. Geology Events feed. Every time I find out about a talk or a field trip or a museum exhibit opening or whatever, I'll post it there. I'm also recruiting other D.C.-area geological cognoscenti to serve as co-authors on D.C. Geology Events. So far I've got two people to help out by posting stuff there. So, dear reader: if you are a pipeline for information about seminars, etc., and want to be able to post your events on D.C. Geology Events, please get in touch with me, and I'll add you to the blog as an author.

Why this change, this "avulsion" of my blog flow? There's several reasons.

1. Blogger decided to stop publishing via FTP. I composed NOVA Geoblog on Blogger, but then published it to the NOVA servers. This was always problematic -- NOVA makes me change my password periodically, and it was difficult to keep Blogger in sync with it, resulting in many frustrating instances of failing to publish when I tried to, and then it shutting down my NOVA account access (which automatically locks after three unsuccessful attempts to log in). Blogger found it a pain too, and decided to stop dumping so many resources into supporting FTP. Fair enough. Turns out I'm happy enough to switch away from Blogger for a couple other reasons, too.


2. I always hated the limits Blogger imposed on my typography. I'm an advocate of the old Chinese aphorism that "The beginning of wisdom is to call things by their proper names." Unfortunately, Blogger cannot seem to handle things like accent marks, tildes, degree symbols, and the like. This is a bummer. Even things like long dashes and curly quotation marks turn into garbled code mess when copied and pasted into Blogger. ("Copied and pasted" because you sure can't type them in directly.) So Blogger limits users that way.


3. I started this blog as a way to communicate a stream of news items and web resources to my students. Soon after I started publishing it, though, other people discovered it, and now that extended global audience is primary in my mind as I am writing. I think re-inventing the blog as Mountain Beltway will allow me to directly serve that readership with less NOVA-flavored ambiguity. Fortunately, there is a new tool that allows one to transmit links to cool web resources with a minimum of infrastructure: So, I've decided to join Twitter, and import my Twitter feed into the sidebar of Mountain Beltway.


4. Along similar lines, a clear issue with NOVA Geoblog is that I'm very much a local boy with a lot of interest in engaging with the local geologic community. Hence the frequent announcements about seminars, talks, meetings, etc. Mountain Beltway will be written from a D.C. perspective -- the name itself conveys that, I hope -- but it will be free of all "locals-only" meet-up information. That's what D.C. Geology Events is for.


5. Because NOVA Geoblog is hosted on servers owned by the Commonwealth of Virginia, the same people who employ me, and I never got official permission to blog on our webspace, I was always a little worried that someone would get upset with something I wrote, and get in touch with my bosses and shut me down. There are plenty of cranks out there, and plenty of lawyers to back them up. If I'm blogging on my own, and it's hosted by WordPress, that's no longer as acute an issue. I suppose it's worth disclaiming that there, as here, my opinions are my own and do not represent Northern Virginia Community College, the Virginia Community College System, or the Commonwealth of Virginia.


6. To shake things up a bit. While NOVA Geoblog hasn't gotten "stale," exactly, I've definitely gotten a charge out of inventing Mountain Beltway. I'm excited to do some cool blogging there. In fact, I've been so motivated that I've already written the next ten posts that will appear there -- but I'll parse them out over the next ten days. So much for my plans to blog less, eh?

I got some great feedback in the survey that I blogged about yesterday, and one of the things I'm keen to do is engage in more discussion with other geobloggers and geoblog readers. Ever since my 1000th post, I've noticed an increase in the tempo and diversity of commenting here, and I'm grateful for it. I've also made more of an effort myself to comment on other blogs, and also to respond to comments here, even if they don't explicitly require a response. I've enjoyed the discourse: it's fun. Thanks to all who have participated. I envision a similar lively back-&-forth at Mountain Beltway.

I'll leave comments open on NOVA Geoblog for 1 more week, then shut them down, too.

I set the new blog up a week ago, so you'll find some content waiting for you. See you there.

Labels: blogs, dc, meetings, virginia, words

Via the comments on my Bob Hazen book post, I found George D. Turner's thoughtful, fun geoblog Eclectic Plagiodoxy. You know I'm going to be intrigued by a title like that. Here's the beginning of George's explanation of that polysyllabic wonder of a title:

The word "plagiodoxy" came to me in a familiar place: in front of a classroom of introductory geology students. I was trying to connect the sometimes arcane jargon of the science with ordinary experiences the students were familiar with. In this case, I was working my way through the mineral group called feldspar, trying to make semantic connection with the two sub-groups, orthoclase and plagioclase. So I was chatting about ortho-dontists, ortho-pedists and ortho-doxy. I ended up saying something like "I suppose if you wanted crooked teeth, you would go to a plagiodontist. If you wanted crooked bones, you would go to a plagiopedist. If you wanted to learn to think on the slant, you would go to a plagiodox institution. That's called 'college'."

Go and check out the rest -- I think I like the way this guy thinks!

Labels: blogs, humor, words

Happy new years! The grammar police return! A while back (May!), I commented on a few words that had gotten my attention through their misuse. Since then, a few more peaked piqued my interest, and now I return with the third installment of "Words' worth."

Peak / Peek / Pique - "Peak" means summit or maximum value; "Peek" means look at quickly or furtively; "Pique" means provoke or stimulate. You can "take a peek," but you cannot "take a peak" (unless you're involved in Appalachian coal mining). You can have something "pique your interest," but you cannot "peak your interest" in anything.

(Similiarly): Eke / Eek - People can "eke out a living" but they should reserve "eek" for unexpected encounters with mice.

Cite vs. site - a "site" is a place, either in the real world or on the web. You use "cite" when you're attributing work to someone else (or issuing a ticket, if you're a traffic cop).

Extinction vs. extirpation: extinction of a species or variety means there are none left, anywhere. However, the local version of the phenomenon is properly known as extirpation. Thus, if say you killed every single wallaby in Australia, but the wallabies on New Guinea were still numerous, you would have extirpated them from Australia, but you would not have made them extinct. Even professionals use "extinction" where they ought to be saying "extirpation."

Similarly, a lot of people use the word decimate "incorrectly." To decimate a population (say, of Roman soldiers) was to kill one out of every ten. 10% die, in other words, and 90% are left alive. That may be the official definition, but the truth of the matter is that the vast majority of people use the term decimate in exactly the opposite sense: that 90% die, and only 10% survive (or thereabouts). At what point do we switch the definition of a word: when 90% understand the meaning to be one thing, and only 10% stick with the old definition?

Shear vs. Sheer - There are many definitions to both "shear" and "sheer," but the one I see fuddled up most frequently is when people use "shear" to describe cliffs, or use "sheer" to describe geological stresses.

Oh dear: did you hear about the omission of "emission" on a Kansas state test (wherein some test-writer swapped the word omission for emission). Don't worry: the kids caught the error!

Literally - "Literally" means "actual," not an exaggeration, analogy, simile, or hyperbole, but actual truth. Amazing how many people use this incorrectly. Sometimes it seems like literally the entire world!

Metamorphosize - The first time I put up a post like this (see link above), I harped on the word "orientate." I pointed out that the word "orient" (verb) means the same thing, without an extra, unneccesary syllable. In spite of my harangue, orientate remains in the dictionary. Even worse, I find a lot of people want to throw an extra syllable in at the end of "metamorphose" even though "metamorphosize" is not an actual word.

Standing on line versus standing in line. This one seems to be cultural. Some people claim that when you queue up for, say, a movie, you're standing "on line." This grates on my ears, and I would instead say that you're standing "in line." (I reserve "online" for internet presence.) But I don't know that I am justified in feeling this way -- I think it's more likely that I just grew up in an "in" household, versus an "on" household.

As before, I'd like to know which words bug you. Chime in.

Labels: geologists, science and society, teaching, words

People. It's T. rex, not "T-Rex."

Also, silicon is an element (Si); silicone is a colloidal gel made with lots of water; silica is a compound (SiO2) which is the building block of many minerals.

Unique means "one of a kind." Therefore, applying modifiers to unique, like "very unique," or "most unique," add words without adding any additional meaning. If it's unique, it's unique. There's no such thing as "very one of a kind."

Thank you for your attention.

While I'm dispensing some advice, can someone give me some...? What's the difference in meaning between geologic and geological? And similarly, historic vs. historical?

What's the difference between silicic and siliceous?

Words' worth I

Labels: dinosaurs, minerals, words

It's the Earth's "birthday!" Today, October 23, is the anniversary of the 4004, BCE creation of the cosmos, according to Archbishop James Ussher, Primate of All Ireland and Archbishop of Armagh. Ussher is famous for having made a pre-geology attempt to date our planet using a literal interpretation of Biblical scripture and a carefull tallying of "begats." Though a scholarly and noble attempt given the intellectual context of his day, Ussher's ideas were soon supplanted with the discovery of deep time by geological studies, starting ~100 years later with another James, James Hutton. The accepted age of the Earth was pushed back further and further by subsequent geological work, and our currently accepted age for the planet (and the Solar System) is approximately 4.6 billion years. Despite these insights, there are a substantial number of "Young Earth" creationists who stick to Ussher's number, or a similarly itty-bitty age derived from a Holy Book of their choosing. This bizarre contention puts them in the awkward position of having to deny the fossil record, the decay of radioactive isotopes, the expansion of the universe, and (of course!) the evolution of species by mechanisms other than Special Creation by a diety. Because Ussher was a scholar and a thinker as well as a religious man, my suspicion is that if he were alive today, he would reject the close-minded anti-science that so many creationists voice.

I love the fact that Ussher's title was "Primate," considering that the main issue creationists have with evolution is that they don't want to be descended from non-humans. The word primate comes from the Latin for "first" (as in "primary") and reflects Ussher's position at the top of the Church of Ireland, and Linnaeus' view that the primates were "first" among the mammals, an anthropocentric bias that persists in uncountable ways today. The truth of the matter is that humans are primates, and so are baboons, lemurs, gorillas, and yes, even chimpanzees.

Ussher was indeed a primate -- just like the rest of us. Happy birthday!

Labels: geologic time, history, words

First off, I'd like to say a big "Thank you!" to everyone who joined in the basins discussion yesterday after my post comparing depositional basins and structural basins. I haven't had a post generate that level of chewy discussion in a while, and it pleases me to see folks chiming in.

So here's some additional thoughts: yes, structural basins are big synforms wherein the bedding dips in all directions towards the center of the structure. They are the opposite of structural domes. It seemed that this was a sticking point with several readers, who weren't familiar with "structural basin" used in this way. Chris indicated that the term "structural basin" isn't part of structural geology vocabulary in the U.K., and in many ways I agree with him when he says, "calling a structure which was never a site of sediment deposition a 'basin' seems rather silly to me." But that is what our textbooks and lab manuals refer to them as... That's why students get confused, and that was my motivation to draw the graphic delineating the differences. (I didn't invent this term! Ed appears to back me up on this.)

Suvrat called attention to the erosion that I included as part of my structural basin "model," and while that's not necessary for a structural basin to be called a structural basin, I included it to show that there was no basin-like topography necessarily involved. And that word, topography, is likely critical to the discussion. Shame on me for not mentioning it yesterday. (Ed mentioned that's how he distinguishes the two.) Here's the way structural domes and basins are expressed in the second edition of Steve Marshak's textbook Earth: Portrait of a Planet (reproduced here with his permission):


In the uppermost part of the image, you have both topographic and stuctural domes and basins. In the central part of the image, you see erosion-gutted (and differentially eroded) structural domes and basins that are not topographically basinal or domal. Brian asked an excellent question after yesterday's post, which was "where's a good example of a structural basin?" I didn't know of any great ones offhand, so I Googled it, and as it turns out, Wikipedia has a list on their page about "structural basins." (Tragically, the fourth hit on that same search turned up yesterday's blog post! I hate it when that happens.)

And this brings us to the most interesting part of the discussions: Lockwood was the first to say it: "Basins can be both, can't they? i.e., a structural basin can become a locus of deposition." Ah, yes! As my friend John Weidner likes to say about simple geological explanations, "Actually, it's more complicated than that." Are there depositional and structural basins? "Yes...."

"...but actually, it's more complicated than that."

The reality is that many basins are both structural and depositional. I hinted at this yesterday, when I said "[Depositional basins] can also self-perpetuate, as the heavy sediment keeps the crust sagging downward at that location." But I didn't launch into a full-blown discussion then because I was mainly interested in generating crisp thinking in my students: understanding that the term "basin" gets used (at least in our textbooks) to mean two different things, which have similar patterns but independent means of generation. Yes, the reality is that crustal sagging creating a lowspot is itself a structural phenomenon, which then has sediment accumulate atop it, which can encourage through its weight additional sagging, and additional sediment accumulation, and so on. Howard pointed this out in yesterday's comments. The layers at the bottom of such a "hybrid basin" will be structurally deformed at the same time sediment is being deposited at the top of the stack in the resulting topographic low.

So, really, what I outlined yesterday are end-members of a spectrum:


Reality has shades of gray! Yesterday's post was about the "black and white." Today, we discuss the spectrum in between.

How can we tell them apart? The classic test of whether a basin represents a sag in the crust and a hence a paleo-crustal downward flexure is to look at the thickness of the sedimentary layers. If they thin towards the edge and thicken towards the middle, then you've likely got some topographical low, and hence elements of a depositional basin. In contrast, a purely structural downwarp in the strata will not necessarily show any such changes in bedding thickness across the structural basin; so you'll see uniform thickness across (so much as such a thing exists):



Many basins have aspects of both of these -- sometimes they look structural further down and depositional higher up. The lower half of the Marshak illustration above is a map that shows the various basins and domes of the Midwest U.S. (Sometimes the domes are called 'arches' in they're more elliptical in outcrop than circular.) So are these regional-scale basins depositional or structural? Or both? Both, pretty much. These basins do show bedding thickness changes over time, and as I understand it, those times of increasing crustal flexure have been tied to the various episodes of Paleozoic mountain-building on the east coast. The Cincinnati Arch, for example, appears to have developed by the Devonian, since the layers older than the Devonian appear to be uniform in thickness across Ohio, but the Devonian sequence is thinner atop the arch and thickens to the southeast. (I'm no expert on Midwest geology; if someone cares to clarify and/or enlighten, please do!)

Eric made another excellent point: that sometimes we refer to the volume of sedimentary rock that was deposited in a depositional basin as a sedimentary basin. Hence the volume of sedimentary rock comprising the tortured strata of the Valley & Ridge province is sometimes referred to as the Appalachian Basin: not because it's either a depositional or structural basin today, but because it was a depositional basin in the past, before it got folded and faulted. Interestingly, the Marshak map also shows a non-folded, non-faulted Appalachian Basin northwest of the Valley & Ridge province. Hmm. You mean there's one term that geologists apply to two different things?

"No! Say it ain't so!"

Howard asked about the basins of the Basin & Range province. In my parlance, those would be strictly depositional basins -- structurally controlled, yes, but by brittle faults rather than crustal downwarping. They are sites of sedimentary accumulation, but do not show any kind of synformal structure. Thus, they don't qualify as "structural basins." Tricky business! ...Yes, they're basins; yes, they're structurally controlled. But they don't meet the definition for "structural basin."

And lastly, both Eric and Howard noted that there's yet another kind of basin: a drainage basin, a topographical feature through which runoff is collected, essentially synonymous with "watershed." To summarize the difference between a drainage basin and a depositional basin, consider this: a topographical basin which is primarily the site of erosion would be a drainage basin. A topographical basin which is primarily the site of deposition would be a depositional basin. Can a single topographical basin host both erosion and deposition? Definitely! Consider the Mississippi River drainage: eroding in the high country headwaters, depositing in the lowlands nearer the mouth of the river.

Thanks again for all the thoughtful comments, folks.

Labels: appalachian plateaus, appalachians, devonian, sediment, structure, valley and ridge, words

One thing I've noticed when teaching Historical Geology at NOVA and GMU over the past four years is that students get confused between basins. There are depositional basins and structural basins, and they're not the same thing, though they both sag downwards in the middle. The other day while driving out to the Blue Ridge for a hike, a lightbulb went off above my head. I knew what I needed was a graphic that explicitly laid out the processes responsible for each structure, and their development over time. I jotted down a reminder to myself on the lid of the Starbucks coffee cup in my car's cup-holder.

When I got home, I translated the scrawled reminder into action. In my spare time over the past couple of days, I've been composing the basin graphic with CorelDraw. Here's what I drew:



Depositional basins result when there's a low spot on the Earth's crust. Water flows into these crustal sags, carrying sediment with it. Gradually, they can fill in. Sedimentary inputs are shown with arrows. (They can also self-perpetuate, as the heavy sediment keeps the crust sagging downward at that location.) Layers stack up according to superposition: oldest on the bottom, youngest on the top.

In contrast, structural basins have a different story. There, we start with an accumulation of sedimentary layers, and then we deform them into a basin shape. This deformation is the result of tectonic stresses which warp the rock layers. Erosion can then attack the downwarped strata, planing the "nested cups" shape down to a roughly horizontal ground surface. Sedimentary outputs are shown with arrows. The resulting outcrop pattern is somewhat like a bull's-eye, with the youngest layers exposed in the middle and the oldest layers exposed on the outer part of the structure.

In a depositional basin, the downward central sag comes first, and the stack of sediment is a result of that sag. In a structural basin, the stack of strata comes first, and the central downwarp is produced second.

________________________________________
If any educators want a larger version of this graphic for use in teaching, let me know. I'll happily e-mail you one. Also, if anyone would suggest any modifications to the graphic to make it more accurate or more useful for communicating these ideas, I'd be happy to get that feedback.

Labels: art, sediment, structure, teaching, words

This might be a "Words Worth" sort of item...

I find that a certain subset of my students (i.e. the ones who don't do very well in my classes) make no distinction between the phrases "tectonic plates" and "plate tectonics." To me, these mean very different things, but to the undertrained geologist, they must appear synonymous.

What's the difference?

A tectonic plate is a thing, a noun, an object. It is a slab of the Earth's lithosphere that behaves as a relatively coherent block. It is not eternal. It can grow with the addition of new lithospheric material from neighboring plates along its edges (accretion) or fuse with another plate along a suture zone. It can also break apart discretely, as Eastern Africa is doing today, or diffusely, like the Basin and Range province of North America, where the crust is being stretched and thinned.

On the other hand, plate tectonics is a paradigm, a model for how the Earth works. It is a well-corroborated hypothesis that explains so many disparate phenomena it has earned the status of a theory. (And I mean theory in the scientific sense -- a seriously well-founded concept, on par with the theory of gravity, atomic theory, or the theory of evolution by natural selection: these are all hypotheses which have been repeatedly tested over many years and never falsified, so that they are our best working explanation of how a particular thing works.) It is a variety of tectonics in general, which includes non-plate-oriented explanations for building things like mountain belts and continents. Plate tectonics is an idea, an explanation.

Anybody else encountered the false conflation of these two different terms? I think it's going to have to be something that I address up front when I introduce plate tectonics in class, in the manner of A Private Universe -- assessing student worldviews and weeding out (nullifying) false conceptions as a necessary first step before you can sow correct ideas.

Labels: plate tectonics, teaching, words

Jesse Carlucci of the Diagenesis blog has an excellent piece up today about the term "Darwinism" and its pitfalls on many levels. You should go check it out immediately.

Labels: blogs, evolution, words

Some geology-oriented terms made the New York Times' annual rundown on buzzwords. It's noteworthy that two of the (non-geological) others on the list (futarchy and edupunk) were coined by Virginia professors.

Labels: news, teaching, virginia, words

I reckon I'm due for a rant. Here's a list of words that bug me:

Dolomite in place of dolostone: dolomite is a mineral. A huge pervasive second use of the word, however, is to mean a rock made mainly of the mineral dolomite, for which the proper name is dolostone. This is so, so, so common it's hardly noticed. And it's so incorrect. Rocks and minerals are not the same thing.

Orogen in place of mountain belt: the word orogen is technically correct, and quite accurate, but in spoken speech, it sounds too much like "origin," and its use can sow confusion. The only real difference I am able to hear when people say "orogen" is that they tend to pronounce all three syllables, while "origin" is generally pronounced with just two: ore-gin. But maybe that's just the Virginians I hang around with. Mountain belt has the same meaning, but I guess it has problems of its own, since mountain belts may not be topographically mountainous any more. Hmmm. ...Toughie.

Extra-syllable words: Should we say benthonic when benthic means the same thing but with one fewer syllable? What about people orientating themselves instead of orienting themselves? What advantage do these extra syllables provide? Are they vestigial structures in our language?

An educational peeve is that students regularly refer to teachers giving grades. I don't know about the other professors, teachers, and instructors out there, but this one really rankles me. My students earn their grades. What I do is keep track of what they have earned, and eventually assign the proper grade to them. I am merely a secretary, an accountant. I tally it up, but the points they accrue (or don't) depends on them. No gifts required!

A huge bummer is the continued use of theory in non-scientific circles to mean hypothesis. In general use, "theory" has a tenuous, shaky implication, while in science it means "as solid and dependable as an explanation gets." David Quammen explored this well in his discussion of evolution in National Geographic a couple years ago. For the record: a hypothesis is a possible explanation of a phenomenon, calling to be tested. A theory is a well-corroborated hypothesis (i.e. it has passed a great many tests) that coherently unites a number of disparate phenomena under one central explanatory umbrella. Big difference there; huge. Makes communication about important concepts difficult.

Lastly, my all-time least favorite word: Believe.

Everywhere I look, I see statements like "Scientists believe that the Earth formed 4.5 billion years ago," and it drives me up the wall. Scientists infer that the Earth formed 4.5 billion years ago, based on their reliance on data and logic. We have physical evidence (lead isotope ratios from three different radiogenic systems, measured in Earth rocks and in meteorites) that all suggest the solar system's solid-state clock started counting 4.5 billion years ago. Because we've never observed anything other than the steady, statistical decline of radioactive parent isotopes to produce daughter isotopes, we assume that the past worked in the same way as today (actualism/"uniformitarianism") and that these empirical measurements have meaning. We logically deduce that the Earth is the implied age, but we don't "believe" it.

Similarly, I get apoplectic when students ask me "Do you believe in global warming?" No, I don't believe it; I'm convinced of it on the basis of (a) physical evidence (data) and (b) logical inference from that data. To spell it out:

1. CO2 absorbs infrared radiation.
2. Infrared radiation is reflected upwards from the surface of the Earth.
3. CO2 is produced by the burning of coal, oil, natural gas, wood, ethanol, and biodiesel.
4. We burn a lot of these carbon-rich fuels by oxidizing them.
5. CO2 concentrations in the atmosphere are measurably increasing.
6. Oxygen concentrations in the atmosphere are measurably decreasing.
7. Globally, average temperatures are observed to be increasing.
8. Therefore, based on #1-7, the increase in CO2 concentrations in the atmosphere is causing the increase in temperature.

There's nothing there to believe in. It just is. Fact, fact, fact, fact, fact, fact, fact, and a logical inference that stems from those facts.

Ditto for the theory of evolution by natural selection. It's not something I believe in; it's something I'm convinced of because it's logically coherent and supported by reams of data gathered over 150 years of hypothesis-testing.

If there is one thing that scientists believe in, it's that the universe makes sense. Our starting assumption is that the physical world operates according to unchanging laws which may be deduced if we're clever enough. On the other hand, if the universe is mercurial in its physical laws, then science doesn't have a chance of figuring things out because the laws that apply on Tuesday will be different from the laws that apply on Wednesday. It should go without saying that, as far as we can tell, this is not the case. The universe does behave in a consistent and predictable manner, insofar as we can tell. Ergo, science is an appropriate way to go about elucidating its structure and properties. No belief necessary.

Which words bug you? Chime in.

Labels: geologists, science and society, teaching, words