Big Earthquake in Japan

A M6.7 (6.8 according to the USGS) earthquake hit the north shore of Japan today. I've heard of at least 6 fatalities, and that the quake caused a fire at a nuclear power plant. My Japanese is a little rusty (I learned it all from reading menus), but some of the video here is interesting. In particular, I am always looking for how people react in the videos. Most of the time people look confused and rarely do they do what they are supposed to do. Never having been in a large earthquake, I am in no position to criticize, but maybe it says something about our earthquakle preparedness?

UPDATE 11:14 PM my time - Reports are now that a very small amount of contaminated water leaked out of the reactor and into the Sea of Japan. In addition, another M6.8 quake hit the same region, farther out at sea and fairly deep (316 km according to the USGS, compared to the earlier one at 55km,) so we'll see if it does much damage.

No thanks, I only eat organic free-range cardboard

I am leaving this post up but it turns out it might have been all made up, see my retraction here. The authenticity of the original report and the later correction are both debatable.

I have recently hinted that my recent field work in the Pyrenees was augmented by exceptionally good food. For my Ph.D. I did field work in eastern China, and while in general I thought the food was also quite good (can't say the same for the wine but that's OK), there were some things I was a little suspect of. Baozi, little steamed buns filled with pork, sweet bean paste, or nothing, were pretty standard both at breakfast and lunch (and pictured above.) I considered them pretty harmless, especially in constrast to the Thousand Year Eggs. That was until I read this article. In case you don't want to link to the article, a Chinese television crew found that at least some baozi makers will substitute up to 60% of the wheat or rice flour dough with cardboard softened with industrial solvents. Yes, you read that correctly, cardboard softened with industrial solvents. Allegedly the buyers couldn't tell the difference. In my experience, most baozi are pretty bland. To be fair I didn't have the pork ones (I'm a vegetarian), but the sweet bean and plain ones were not that memorable. Although my adviser and I did devise a genius plan to make them marketable in the US by stuffing them with cheese, beer battering and deep frying them and then serving them with a ranch dipping sauce.......I digress. My point is that even though they are not the most flavorful things in the world I am shocked that 1) someone would think of this, 2) someone would actually follow through on this once they had the terrible idea 3) no one could tell the difference, and 4) the folks at Hostess didn't think of this one first.

As a kind of side note, I also just [finally] finished Michael Pollan's The Omnivore's Dilemma. I will write a proper review, but suffice it to say it is an excellent book, and it got me thinking about all kinds of things. In the last part of the book, Pollan describes a dinner he prepared almost entirely made of food he collected (foraged, hunted, gathered, etc..) from the forest. I wonder if cardboard baozi count as a forest food?

Where on (Google) Earth #28

This could be hard, or Ron and his army of undergrad assistants (Yami let out that secret here) could have it figured out before I return from my coffee run. Anyways, here it is, Where on (Google) Earth #28!

Apparent Return

I have now returned from the field, and am ready to once again rejoin the geoblogosphereo, armed with field pics, a new appreciation for cheese, vertical profiles, and a few hundred pounds of nice fresh granite. First the field pics and a little geology.

For those of you who don't know I am working on a project in the Pyrenees, a very interesting [mainly] Cenozoic convergent orogen. This was my first trip to this area, and I think like many geologists visiting their field site for the first time, my appreciation for the project and of the many papers already written about the geology of the area increased dramatically.

This is also the first time that I've used thermochronology to study the uplift of a convergent orogen. In the past, I have mainly focused on extensional orogens and normal faults. Normal faults are in many ways the most ideal system for thermochronology. This is a highly simplified schematic diagram showing how large rotational normal faults operate. There is no scale on this diagram, but it is meant to depict a fairly large cross section of the brittle upper crust, let's say 8 or 10 km thick.


The three images above depict three different time slices during the extension of some chunk of crust. Normal faults are the kinds of faults that accommodate extension (you can see that the final image, on bottom, has been thinned and stretched, or extended). The faults rotate as they move, and in the end, rocks that were originally very deep in the crust (some of the grey bars), are exhumed, or brought up to the surface. This exhumation can happen relatively rapidly, and results in the cooling of originally hot rocks (hot because they were deep in the crust). This cooling is what we can measure using thermochronometers.

Thrust faults are completely different, not only in terms of what environment they form in, but also with respect to what they do thermally for a rock. The figure below shows time slices of an idealized thrust system

(stolen shamelessly from http://ic.ucsc.edu/~casey/eart150/Lectures/4ThrustFlts/4thrustfaults.htm)

Although thrust systems can make some impressive topography (think the Himalayas, Rockies, and many other major mountain systems), they actually do not exhume rocks. You can see this by tracing how deep any one point is on the diagram above, or on this excellent animation of a thrust fault. Since thrust faults don't exhume rocks, they don't cool rocks (well, that isn't strictly true but we will save that discussion for later), and therefore we can't necessarily use the same thermochronologic approach to study them.

Fortunately for us, the large welts in topography often formed during thrust faulting are often associated with very high rates of erosion. Erosion removes rocks from the top of the thrust sheets, thereby exhuming and cooling the deeply buried rocks we want to study. One of the reasons the Pyrenees are such a great place to work is that the products of this huge erosional event (aka the sediments in the foreland basin) are very well preserved and in many places very well exposed. In fact, many of the older sediments are themselves caught up in younger thrust sheets, which are then eroded and exposed for us to study. Many Spanish and French geologists (along with colleagues from around the world) have done an exceptional job reconstructing the history of deformation and fault activity by mapping these sediments and associated thrust sheets. And, just as a disclaimer I would like to point out that my thermochronology would be completely and entirely meaningless were it not for the labor of the structural geologists and sedimentologists who have studied this area for decades. As another disclaimer I am not a sedimentologist, and can only pass for a structural geologist by association.

On our way to the field site, we passed through places where these sediments are well exposed. One of the more impressive things about the Pyrenees are the piles and piles of conglomerate you see, some like this exposed in thousand meter high cliffs.



these conglomerates were all deposited, then deformed, during the main contractional event in the Pyrenees (early to mid Cenozoic). Some of you who have travelled to Spain may be familiar with similar looking exposures at Montserrat, these are not directly related to the Pyrenean orogen (but instead the younger Catalan Coast Range orogen), but did add to my feeling of this part of Spain as the land of conglomerates.

The thrust sheets are themselves impressive, and although I don't have the information on the unit exposed here, it is a pretty picture


But alas what I came to sample and study were the granites. Most of these granites formed (well, crystallized from a magma) during the Hercynian orogeny (late Paleozoic) where they intruded a Paleozoic sedimentary succession. The Paleozoic sediments are now all deformed and metamorphosed (that will be a later post). Many of the granites were then exhumed to at or near the surface. We know that because we can still find places where the granites are overlain unconformably by Triassic sediments. You can see that in this picture

The reddish layered rocks at the very top lie uncomformably on the granite below (the greyish stuff). The contact is itself folded (don't let anyone every tell you granites don't fold), and has now been eroded nicely for us to sample and study.

In order to do proper thermochronologic studies, you need to sample the greatest amount of structural relief you can. In extensional terrains, this is nice. Because the blocks rotate as they exhume, you can often collect samples from many kilometers of structural relief, sometimes without climbing more than a kilometer of actual altitude. Areas where the exhumation is accomplished mainly by erosion are very different, here, for example, structural relief roughly equals actual relief. So, to sample 15o0 meters of structural relief requires hiking up 1500 meters of elevation.

Not to complain, I was with an excellent field group and was able to do some exceptional (albeit long) hikes. The pyrenees are filled with very nice marked trails that take you up big granitic mountains. I was even able to bag my first 3000 meter Pyrenean Peak (3221 to be exact). But it did give me a whole new appreciation for vertical profiles. They are definitely the way to go for thermochronology (perhaps another post as to why), but they are tough things to collect.

This was also my first trip to Europe, which was incredible. But more on that later.

Anyways, a brief intro to my field season, some of my bajillion pics, and even a little geology.

Apparent Void

My posting has been pretty poor lately, all due to my preparation for my upcoming field work. I am leaving this evening for an obliquely convergent Cenozoic orogen, and will be back in July. At least then there will be plenty of field pics to enjoy! Cheers, and enjoy the rest of June.

On-line Thermochronology Community

Lest you think Apparent Dip is the only on-line refuge for Thermochronologists, I'd like to point out the OnTrack Forum, an on-line forum for the international fission-track and thermochronology community. The Forum is edited by Matthias Raab, a research fellow at the University of Melbourne. Although originally a fission-track journal (hence the name), it incorporates all manner of thermochronology, and provides a forum for discussion, networking, meeting announcements, and the like. You must register to take part in any of the discussions, but that is free and worth it if you are a budding thermochronologist.

Communicating Science

Mrs. ADBWADLN directed me to this article by Chris Mooney written for Seed Magazine. The article discusses some of the hurdles faced in communicating science to the public, focusing on the climate change debate, but applicable to a great deal more. In short he discusses the disconnect between scientists and what the general public believes, pointing out some of the misconceptions that make their way into media and political discussions

But I wonder if the scientific community as a whole can truly continue to passively accept the ongoing translational failures that seem to ensue on virtually every occasion that scientific information enters the political and public arena.

Worth the read.

Radon, Humidity, and Earthquakes Update

Just a back track to a previous post of mine that many of you commented on. On of the authors of the paper commented today on my post, the comments, and his paper. He also provides references to his data set and other explanations.

Related Cartoon

I thought I'd link to this cartoon (from of my favorite political cartoonists Ann Telnaes) that relates to a recent post of mine

Broader Impacts

I spent most of the holiday finishing off the last of the bajillion temperature steps I ran on a k-feldspar from my new field area (collected by someone else, but mine now!) I got to thinking about my thesis, and then about how much I contributed to the world's knowledge base. Here is a diagram I came up with, in case you are curious.

Yes, they are different.

Show us your lab - BWRU edition

Following Lab Lemming and Sara at Life is Nich si mal as well as the related field photo post from ...Or Something I am contributing pictures of my old lab. This is kind of cheating, because I no longer work there, but I don't have pics of the new place yet.

How much you pay for gasoline

Because gasoline is an earth science related commodity, I feel I can still call this post earth science related even though it will largely be an airing of grievances. As anyone in the U.S. who ever listens to the radio, picks up a newspaper, or clicks on a TV can tell, gasoline prices are at an all time high right now, just prior to a big travelling/driving holiday weekend. I am not sure what the average price is, but at the Exxon station down the street from my house it is $3.15 a gallon for regular. This seems to be a huge story, oil prices are down, but gas prices are up, oil companies are gouging us, what will congress do to save the consumer? The hard working American? The major news outlets are particularly fond of this, pointing out how gas costs are starting to really hurt middle class America. Even NPR is devoting an amazing amount of newstime to the issue, and to top it all off, the other day I got an email from MoveOn.org rallying for a petition to stop oil companies from price gouging, save America! While I agree price gouging for any product it wrong, and if that is happening I want people held accountable, I am shocked by the focus. Has anyone (even the "progressive" MoveOn.org) used this as a rallying cry for increased funding of public transportation? How about tighter fuel standards? Of course not, the focus is all on how much you pay at the pump. It burns me that spending an extra $30 or $40 a month shares headlines with all of the truly horrible things happening in the world.

This gets me riled up, because what everyone seems to be ignoring is that you decide how much you are going to pay for gasoline WHEN YOU BUY YOUR CAR. Fluctuations of the price at the pump really don't make that much of a difference. For example, my wife and I own 1 car, a 1999 Saturn SL, which easily gets over 35 mpg in the city, and often tops out of 45 mpg on the highway. We drive more than we like to; we now live in a city with poor public transportation, and previously lived in a situation where Mrs. Apparent-dip-but-with-a-different-last-name could either spend 5 hours round trip on public transport or make the same round trip in 1.5 hours in the Saturn. Anyways, my point is that we drive, but when we bought our car our first concern was mileage. The big myth is that if you want a high mileage car you have to plunk down over $20,000 for a hybrid, that just isn't true. Many 4 cylinder cars get good mileage, and are on the cheaper end of the car price spectrum (lik ours.) So, we bought a car, we take public transportation when we can, but we end up driving a fair amount. The recent spike in gas prices means that every month I pay maybe $25 more for gas now that I did 6 years ago. That's it. A few less schwanky coffee drinks per month? Maybe cut my own hair, instead of my usual expensive professional 'do? I am paying less for gas now than the driver of some behemoth SUV compensation monstrosity did 10 years ago. Even the most fuel efficient SUV's rarely break 20 mpg, which means that if they bought gas at half of it's current price they'd still be paying as much as I do now at the current record high prices. The point of this is that anyone who has bought a new car in the last 10 years intentionally decided how much they wanted to pay for gas and what kind of mileage they wanted, and if they went with a low mileage, then instead of complaining about oil companies they should realize that it is mainly the fault of their terrible decision making skills that fluctuations in gas prices cost them so much. Especially when they ponied up $25,000 or more for a 6 or 8 cylinder SUV or "luxury" sedan; you knew what you were buying, so stop complaining so much! And if this is a rallying cry for anything it should be for public transportation and intelligently designed (read walkable and bikeable) communities.

I am not pro price gouging, or a huge fan of all of the business dealings of oil companies, but they are companies, and the reason they make so much fricking money is because we use so much of their fricking product. Nail them for price gouging if they are doing it, but seriously, there are more than one party in the wrong here.

OK, have a good holiday weekend.

National Parks in 3D, on Your Laptop!

I've been checking out the Branner Earth Sciences Library Blog lately, and it just pointed me towards a National Park Service site that offers 3D pictures and images relating to the geology of national parks. Here's a classic example.

The Clocks in the Rocks

As I mentioned in my last post, the Smithsonian Natural History Museum has a geochronology display in the Rocks and Minerals section of the museum. The exhibit wasn't enormous, and did not have anything on thermochronology, which is too bad considering how they are trying to appeal to young people, and thermochronology is non stop excitement (the only geologic discipline in the running for a spot in the X-Games as an eXtreme sport), but I still really liked it.

One things they had was a ginormous zircon crystal on a big rotating disc. The crystal would go around in a circle every 5 seconds or so. At the bottom is a geiger counter, so as the crystal got closer and closer, the geiger counter started registering more and more counts. I took a series of pictures hoping you could see the meter on the counter and the position of the zircon, but alas, not enough light.


But perhaps my favorite part was a short video entitled "The Clocks in the Rocks" (see the transcript here). The story has two characters, a woman who is the geochronologist, and the guy who wants to know more about geochronology. They are in a TIMS lab (thermal ionization mass spectrometry), and the video goes through the basic steps of getting an age. Unfortunately none of my pictures of the TIMS filament or the ion-exchange chemistry came out, but you get the point.

What I liked most about this video was that even though it was simplified and directed at a general audience, it wasn't dumbed down or incorrect. I think this is key to attracting young students into the geosciences, the discipline has to be presented as rigorous, as something more than mineral collecting. It is easy in the earth sciences to fall back on pretty pictures and catastrophic events as ways to hook students, but that tends to misrepresent what professional geologists actually do.

Anyways, the rock sample they allegedly used for this video was from Half-Dome, and in the end they show a concordant U-Pb age of ~86 Ma (on a Wetherill Diagram).

So two thumbs way up for the Smithsonian Natural History Museum Rocks and Minerals display. Unfortunately I did most of my museum visiting when I was young, and this is one of the first times I've gone to a place like this as a professional geologist. I'd be interested in reviews of other public museums and how well/poorly they treat geology.

Smithsonian Natural History Museum

On my recent trip to Washington D.C. I had a chance to spend a good afternoon in the Rocks and Minerals section of the Smithsonian Natural History Museum. This was the first time I've been to D.C since I was in grade school, a time in my life when I would have only cared about the displays if they had video of Andre Dawson or Walter Payton, or if there was free food, especially really bad for me food. Now that I am a certified geologist, I was really excited to go through the displays again. I was entirely impressed, I really thought that the combination of fantastic rock and mineral specimens, informational displays and devices, and interactive exhibits was superb. I mentioned in the last post that they had a "Make Your Own Earthquake" experiment, they also had petrographic microscopes set up to view thin sections on cross polarized light, real-time displays of world earthquake activity, interactive quizzes, and things you can sit and climb on (a pre-requisite for a very active young Thermochronic). They also had a geochronology display (which I'll blog about next) that included a video describing how to make a TIMS (thermal ionization mass spectrometry) zircon U-Pb measurement. Simplified, of course, but very well done.
Attached to the rocks and minerals is the gem display, which includes the Hope Diamond, the world's largest blue diamond. Perhaps it is my bias as an earth scientist, but the cut gem display was a huge letdown after the minerals exhibit. Diamonds are interesting minerals, and are good for jewelry, but are not even in the top 10 of Thermochronic's most beautiful and interesting mineral list. Please excuse the blurriness of some of these pictures, the lighting isn't the best in the museum, and I don't own a tripod [yet].

Quartz with rutile inclusions

riebeckite (crocidolite), the bad-for-you asbestos

rhodochrosite and fluorite on calcite

amethyst (purple quartz)

Two stony-rion meteorites, Esquel (left from Argentina), Springwater (center from Saskatchewan), and Imilac (right, almost off screen, from the Atacama Desert)

Two more stony irons, Albin (from Wyoming) and Ahumada (from Chihuahua)

peridotite xenoliths from Hawaii

columnar jointed basalt

annd my favorite, a ptygmatically folded vein

Incidentally, I also had a chance to do my version of geology recruiting. Like all of D.C., the museum was packed with bajillions of middle and high schoolers on field trips. When I was in a crown at the more popular exhibits, I made sure to say things like "Wow, this is amazing, I think when I get to college I am going to take a geology class," or "Looks like being a seismologist would be a great job!" This made Mrs. Apparent-dip-but-with-a-different-last-name laugh, which is always good, but I am sure I also inspired dozens of young earth scientists to think of new careers.

Home Seismology Laboratory

I spent the past weekend in Washington D.C. visiting THM, a trip which included plenty of time at the Natural History Museum and its superb geology/mineralogy display. I'll write more about that later, but while we were there, THM and I got stuck in the "Make Your Own Earthquake" display. It is basically a seismometer sitting on a big cube of pink granite and hooked up to a monitor. If you whack the granite or jump up and down nearby, it registers as an earthquake. I think the display is aimed at middle schoolers, but my earthquakes were way better.
Anyways, he told me he had a similar capability on his laptop, so when we got back home I looked up and downloaded the freeware program SeisMac. SeisMac takes advantage of the Sudden Motion Sensor (an accelerometer) standard in all relatively recent Macintosh laptops (probably in PC's as well, but I'm a Mac man, so I don't care). The SMS is responsible for detecting when you drop your computer, to try to stop and protect the hard drive. I am not up for testing this feature yet, but SeisMac at least lets you see the real time readings. Below is a screen capture I took on the train ride home from D.C., when we hit a little bump, you can also see some of the more rhythmic rolling of the train car.
Incidentally, the same person/company that made SeisMac also makes SeisMacCalibrate. Since the computer is only really worried about large accelerations, it isn't the best-calibrated or most precise device in the world. Now I just need to figure out a good way to fit this into a lesson...

K-Ar and 40Ar/39Ar Thermochronology

In this post I'd like to outline some of the more important aspects of Ar/Ar thermochronology. I am going to start with a brief outline of the K-Ar technique, but spend most of the post on the more popular Ar/Ar variant. This post is a long time coming; as far as published reliable radiometric dates, I'd bet that Ar/Ar thermochronology is the most used chronometer in earth science (although I did recently hear Mark Harrison claim he had "age characterized" 100,000 zircons for U-Pb geochronology, so I could be way way off). There are a few primary reasons for the popularity of the method, some I'll discuss later. But first the basics.

Potassium (K) is the 7th most abundant element in the earth's crust, and is a major component of many common rock forming minerals. Very common minerals like biotite and muscovite mica and potassium feldspar contain weight percent levels of K. Naturally occurring K is made of 3 isotopes, ³⁹K (93.258%), ⁴⁰K (0.012%) and ⁴¹K (6.730%). ³⁹K and ⁴¹K are stable, ⁴⁰K is radioactive. Natural Ar is fairly abundant in the earth's atmosphere (~1% of the air we breathe) and is composed of three isotops, ⁴⁰Ar (99.600%), ³⁸Ar (0.063%), and ³⁶Ar (0.337%). ⁴⁰K decay is an interesting process, unlike the U and Th systems I've blogged about earlier which undergo a chain decay, ⁴⁰K has a branched or dual decay scheme. That means that 89.52% of the time, ⁴⁰K decays by beta emission to ⁴⁰Ca. 10.48% of time time, ⁴⁰K decays by extranuclear electron capture to ⁴⁰Ar. The ⁴⁰K to ⁴⁰Ar process is the one we will concern ourselves with in this post. ⁴⁰K - ⁴⁰Ca is rarely used as a geochronometer because Ca is so abundant in nature. It is hard to differentiate in minerals what Ca formed in the mineral from decay of K and what Ca was included in the original mineral structure. Argon, a noble gas, is rarely present in significant amounts within crystals, so we do not have to worry as much about the original ⁴⁰Ar component (although you will see later that the ⁴⁰Ar/³⁹Ar technique lets us deal even with "inherited" ⁴⁰Ar). ⁴⁰K has a half-life of 1.25 billion years (Ga), which makes it perfect for addressing a wide range of geologic problems. The graph below shows the evolution of ⁴⁰K, ⁴⁰Ca, and ⁴⁰Ar abundance versus time.

Like in all graphs that show parents and daughters, the curves intersect at the half-life. Focusing on the ⁴⁰Ar then, we can see that the daughter to parent ratio, or ⁴⁰Ar/⁴⁰K changes over time, like this
We can measure the ⁴⁰Ar and ⁴⁰K in a sample, and from that ratio, calculate an age. The age equation (shown below)

then relates the amount of parent (⁴⁰K), daughter (⁴⁰Ar) and time. Like with all geochronologic systems, actually calculating the age is fairly straightforward. The actual K-Ar age equation is a little more involved because of the branched decay I mentioned earlier, so the final form looks like thiswhere
is the ⁴⁰K decay constant (total)

and

are the decay constants for the two decay paths that produce ⁴⁰Ar, and

is the decay constant for ⁴⁰Ca production from ⁴⁰K. The term in the age equation just before the daughter to parent ratio therefore describes the fraction of ⁴⁰K decays that result in the formation of a ⁴⁰Ar atom.

The K-Ar geochronometer came into widespread use in the 1940's, once the basics of the decay scheme were worked out. There are two main issues with the technique, however, that are kind of a pain, and are the reasons that more often that not the ⁴⁰Ar/³⁹Ar technique is much more popular today. First, you cannot measure K and Ar on the same machine. Typically, samples would first be heated (often using an induction furnace) to very high temperatures (~1400°C). At these temperatures the Ar trapped in the sample is liberated and can then be measured. The ⁴⁰Ar from the sample would be spiked with ³⁸Ar, and then measured on a mass spectrometer. The degassed sample would then be retrieved from the furnace, and analyzed separately for ⁴⁰K. With the amount of ⁴⁰Ar and ⁴⁰K, you culd then calculated an age.
The second problem with the K/Ar technique is determining where the Ar came from. As I mentioned earlier, Ar is fairly abundant in the atmosphere, making up about 1% of what we breathe. It is also fairly common in groundwater and geo-fluids (fluids associated with igneous intrusions and metamorphism). Some of this Ar could become trapped in the crystals, therefore rendering the calculated age kind of meaningless. We know the atmospheric ⁴⁰Ar/³⁶Ar ratio very well, so by measuring the ³⁶Ar we can correct for this "trapped Ar", but we have to assume that the composition is atmospheric. In some cases this is a perfectly reasonable assumption, but with the advent of the ⁴⁰Ar/³⁹Ar technique, we are actually able to evaluate that assumption.

The basis of the ⁴⁰Ar/³⁹Ar technique is the fact that when K is bombarded with neutrons (in a nuclear reactor), some important reactions take place. Namely, ³⁹K is converted into ³⁹Ar. We know the natural ³⁹K/⁴⁰K ratio, so if we can measure the efficiency of this transformation in the reactor, we can use ³⁹Ar as a proxy for ⁴⁰K. This would allow us to measure an age by simply measuring the ⁴⁰Ar/³⁹Ar ratio of a sample. What is even better is that ³⁹Ar does not exist naturally, so we do not have to worry about any inheritance or atmospheric contamination.

³⁹Ar production can be described by this equation

where
is the neutron flux at energy Eis the neutron capture cross section at energy E for the reaction ³⁹K(n,p)³⁹Ar, and
is the duration of the irradiation. In practice, instead of measuring these values directly we figure them out using well defined age standards, producing this equation


where ⁴⁰Ar^* is the ⁴⁰Ar derived from radioactive decay, ³⁹Ar _K is the ³⁹Ar produced in the reactor from ³⁹K, and J is a term that incorporates all of the irradiation variables but can be calculated from standards of known age (determined with other methods), whereThe advent and refinement of the ⁴⁰Ar/³⁹Ar method solved some of the larger problems with the K/Ar technique. First, sample analysis became much more straightforward, measuring different isotopes of the same element is much easier that measuring different elements. Measuring a ratio of two isotopes is also easier that measuring abundances of two elements. The ⁴⁰Ar/³⁹Ar frees us from uncertainty in the spikes used during analysis.

Second, it allows the geochronologist to evaluate the assumption that the "extraneous Ar" in the sample is atmospheric in composition. This is done by progressively degassing the sample at higher and higher temperatures (called step-heating experiments). The first temperature steps are at low temperatures, and tend only to liberate very loosely bound Ar from the crystal, perhaps Ar adsorbed to the surface of the crystal, or held near the surface. With increasing temperature we access and analyze gas that is more tightly bound up in the crystal structure. In the end we then have a series of steps, each with separate isotopic values. If the gas came only from the atmosphere, and was not related to any K, then ³⁹Ar/⁴⁰Ar would equal 0. If the gas was entirely radiogenic, and had no atmospheric input, then ³⁶Ar/⁴⁰Ar would equal 0. In truth, we typically have some mixture of inherited (or atmospheric) Ar and radiogenic Ar. If we plot up these values on an inverse isochron diagram we can determine what the composition of the extraneous Ar reservoir is, and therefore correct our values to determine the real age.

as shown above. If your sample is a mixture of inherited Ar from a single reservoir and radiogenic Ar of a single age, then your individual temperature steps will define a mixing line between those two compositions. We can use the inherited Ar composition to correct our ⁴⁰Ar values, and get the real age. It is also common to see the data displayed as an age spectra, shown below. Here, each box represents an indivual temperature step from a single sample. The y-axis is the age (here in Ma), corrected for extraneous Ar. The height of the box is proportional to the uncertainty of the measurements. The x-axis is the cumulative percent of Ar released. The steps are in order, so the first low temperature steps are on the left, and progressively higher temperatures towards the right. The width of the box is proportional to the amount of radiogenic Ar (⁴⁰Ar^*) released during that step. The large flat area in the middle of the graph is called a plateau and indicates that ages from different temperature steps agree. There is no real physical basis for the definitions of a plateau, and variations abound. Realistically, if our measurement precision was high enough, we would never see plateaus, because natural volume diffusion should round out the profile and make the early temperature steps slightly younger. But, age spectra are very common in literature, so it is important to know how to read them.

The inverse isochron diagram is much more powerful, and I am suspect of Ar papers that do not include inverse isochron diagrams. If the sample is very radiogenic, and there is little ³⁶Ar, then the corrections aren't significant, but still that information should be included. Plateaus and age spectra diagrams are interesting on their own, almost from a Psychology of Science perspective. Even though they are not the most powerful Ar/Ar tool, they are visually pleasing, and telling someone you got a nice plateau usually convinces them of your data quality faster than discussing inverse isochron diagrams. The definitions of a proper plateau usually involve some minimum number of consecutive steps representing some fraction of the total gas that are within error of each other for age and have no statistically discernible slope. You can imagine that if your measurements were kind of crappy, and the age uncertainty on each step high, then getting consecutive steps to agree isn't very difficult. As labs drive for higher and higher precision, and individual step ages have uncertainties less than 1% and official plateau get tougher and tougher to create, even when the age and sample are perfectly acceptable.

⁴⁰Ar/³⁹Ar thermochronology is a very common and useful tool for geologists, and is particulary interesting because it allows the direct examination of a number of the assumptions involved with radiogenic isotope geochronology. Later posts will examine the power of the technique in more detail.

Note - the inverse isochron diagram I used is one I made up just as a teaching tool, the age spectra is real data I collected a few years ago.

Foray into Politics marking an important anniversary

Disclaimer: I in no way pretend to be a historian or expert on war, politics, Haggar Slacks, or international relations. Geology posts will resume soon.

I was inspired today after reading ...Or Something and this post. I tend not to be too political on my blog, but seeing as today is a very important anniversary for my country, I wanted to get this out. First, some background.

Separating minerals for geochronologic analysis is a rather long and tedious process. There are many different steps, non of which are particularly difficult, but screwing them up can mean the complete loss of months of time and thousands of research dollars. Therefore, I can't juggle mineral separation with any activity that requires my eyes or hands, I have to keep those free for the task at hand. To keep myself entertained, I usually turn on my iPod and listen to music, a book on "tape", or, more recently, a podcast.

A few months ago I was "floating kspars" and listening to an American Radioworks Episode about the recently released audio tape collection of presidential phone calls and oval office conversations. I was struck by some of Lyndon Johnson's conversations, especially those that related to the Viet Nam War (although, for a true laugh I recommend his call to the Haggar clothing company requesting some custom made slacks, seriously, some of the funniest stuff I've ever heard). Back to Viet Nam. In particular I was struck by a conversation he had with Senator Eugene McCarthy (Democratic Representative from Minnesota) about the Viet Nam War. This conversation took place on February 1, 1966 (transcript and recording can be found here, more conversations from Johnson and other presidents are here or downloaded here including the aforementioned Haggar Slacks call).

President Johnson : What they [subscribers to the Walter Lippman - J. William Fulbright argument] really think is we oughtn't to be there [in Viet Nam] and we ought to get out. Well, I know we oughtn't to be there, but I can't get out. I just can't be the architect of surrender....I'm willing to do nearly anything a human can do, if I can do it with any honor at all.

As I said earlier, this conversation took place on February 1, 1966. This was the beginning of the escalation in Viet Nam, and just before the deadliest years of the war. According to the National Archives, as of 2/1/1966, there had been 2,670 American deaths in the Viet Nam War, less than 5% of the eventual total of 58,193. Hindsight is 20/20, but if Johnson could have looked ahead at the 55,523 more soldiers who would die before the U.S. got out of the war, you have to wonder if his definitions of honor and surrender would have changed. And why is the focus on honor anyways, shouldn't it be on doing the right thing and saving innocent lives? So when I hear talk of surrender now with Iraq, this is what I think of, I think of the 55,523 kids who could have been saved if someone would have had the guts and foresight not to think of their re-election, or even their short term legacy, but of the long term consequences of saving face. To realize that these are real lives, real people who will pay the price for their political ambitions.

I know that playing the "what if" game with history is dangerous and pretty fruitless. It is easy for me to look back and tell people what they should have done, years before I was even born. I just hope that in 41 years someone isn't writing the same blog entry about Iraq.

If you are interested, this conversation is on tape WH6602.01 9602, the part I highlighted starts at about the 1:28 mark (you can download the .mp3 from here).

All lights burning bright: Apparent Dip Music Club Concert Review #1

This post has nothing to do with earth science, geology, thermochronology, or Brian Urlacher. It does have to do with an excellent singer/song writer, so if that floats your boat, read on.

Today I attended my first concert since moving out east, David Francey playing at the Earlville Opera House in nearby Earlville, NY. Here goes the review.

The background - I stumbled upon David Francey about a year ago, when I was in the middle of trying to write my thesis, and before I had heard any positive responses to job applications. Needless to say I had a few million things in my brain that would start swirling around the moment I woke up and would reach hurricane force by noon. I found David Francey's album The Waking Hour on iTunes, downloaded it, and didn't stop listening to it for at least a few months. It seemed to fit my situation perfectly, Francey's songs are incredibly well written and heartfelt, his voice suits the songs perfectly, and The Waking Hour, as an album, just does not have a weak point. The Waking Hour got me through the first draft and re-writes of all of my thesis chapters, drives and flights between Seattle, Sacramento, and BWRU, and many a anxiety filled late night bout of insomnia. The Waking Hour has since joined Trace, No Code, Between the Breaks Live, and El Corazon as albums I credit with getting me through various challenges in my life. As much as I loved the album I then hit a wall; although Francey released his first album in 1999, only one was available in the U.S., and my budget at the time did not include extra for import discs. Fortunately, over the past decade I have formed an extensive and international network of like minded music aficionados, some of whom I turned on to David Francey, and are now living in Canada (Professor Van Halen). By the fall I had Francey's complete catalog, which of course did not disappoint. As I told the guy sitting behind me today, I recommend them all.

The artist - Francey is a singer/songwriter (and occasional guitar player) who was born in Scotland and moved to Toronto when he was twelve. This means he has an excellent accent, primarily Scottish but with distinctive Canadian features. His songs are drawn primarily from his personal experiences, which is the flavor of folk music I like the most. I compared him in an earlier post to Stan Rogers, not so much in sound or voice or even style, but in the feeling of his songs. Very influenced by place, experience, and probably most importantly, people. This is of course very different from crappy coffehouse poetry "folk music", a lilting and opaque brand of "music" that poor undergrads at tiny liberal arts colleges are subjected to on a regular basis. Sorry, flashback; I've seen a ton of folk singers in concert, and the degree to which newage (which as THM reminds us rhymes with "sewage") and whiny reject poets have infiltrated folk music is alarming. I believe I can ward off these evil spirits by loud regular doses of Francey, Stan Rogers, Townes Van Zandt, Jerree Small, Greg Brown, Gillian Welch, Todd Snider, and The Be Good Tanyas........anti-newage voodoo (see my music links sidebar for suggestions).

The venue - The Earlville Opera House is a nice small venue in a tiny town just south of Colgate University in New York. It was built in 1892, fell into ruin, and is now being restored. Getting there meant an excellent drive through New York on a perfect sunny day. Very nice. Their upcoming folk lineup at the Opera House is pretty solid, if you live in the area check it out.

The concert - David was accompanied by guitarist Craig Werth. He played two sets with a good mix of older songs and some from his newest album, Right of Passage. Even though he apologized for his voice (he had a cold or flu), he sounded excellent, as did Werth, even when singing the a capella "Torn Screen Door". Concerts have a way of changing how you feel about the artist and/or specific songs, depending on the performance; folk singers in small venues especially. Francey introduced each one of his songs with a story about how or why he wrote it, or maybe something about his life that was relevant to the song. I tend to like a song more when I know what it is about, well, as long as the story isn't lame. This is a common folk singer technique, and is one of the main reasons I enjoy small concerts so much. Today I came away really liking "All lights burning bright", "The Waking Hour", "Kansas", and "Under the Portland weather." I liked all 4 of these already, but now that I know the story behind them I put them up with some of my Francey favorites. I don't want to spoil the stories. He has a live album (the one I don't have, and today I was broke and therefore couldn't augment my collection, it'll have to wait), but if you like his studio work (you can preview two of his albums on iTunes), you will like his concerts. In addition, he seemed genuinely nice and appreciative of the folks who came out to see him. This is crucial for me, there isn't much more annoying than discovering a musician you like is actually an immature stuck up retread (we can call this Ryan Adams Syndrome).

The verdict - Excellent, well worth everything. My live music batteries were entirely drained this morning, but are now nice and full. Francey makes excellent albums and puts on excellent shows.

Follow Up to the Last Post - Cheap Food

To follow up on the last post with something related, I offer this article. It describes how the governer of Oregon has decided to try to live on food stamps for a week. I know nothing about the governor of Oregon but I am a big fan of experiments like this. A week isn't a terribly long amount of time, but so many people in charge have absolutely no idea what life is like for the average American (let alone the average citizen of the world, that is of course a completely different story). The total budget for a weeks worth of food (if you are on food stamps) is $21.00, which makes my occasional trips to the Wegmans olive bar seem completely extravagant.
This is kind of interesting, after the shootings at Virginia Tech last week I had thought about blogging about my experience working in the mental health field, specifically my frustrations. I decided not to, but now thinking about the price of food my experience at this job comes up again. During the year after college and before graduate school, I worked as a counselor at a residential treatment facility (read: group home) for severely emotionally disturbed teenagers. It was a definite change of pace for me. An odd job, the average work day could be spent restraining 200lb violent 17 year olds for a few hours and watching against suicide attempts, or I could spend all day playing football and bar-b-qing. Anyways, where does food come in? Well, seeing as we were contracted by the State, we had to provide a set diet for the kids. Every two weeks we got menus, and then had to do the grocery shopping and cooking for the group. We would get in trouble if we strayed too far form the set diets. Technically the kids were supposed to help with the cooking but with the frequency of problems they were usually kept off limits from any kind of cooking implement. It turned out that of the counselors working during my shift, I was the only one who was much of a cook at all. As such, I got very familiar with the official state recommended diet for 11-7 year old boys. The food we had to provide was amazingly unhealthy, very meat, cheese, and starch heavy dishes, very few fresh vegetables (save for iceberg lettuce "salads"), and almost no fruit. A typical weekend breakfast would include either pancakes or french toast, scrambled eggs, sausage or bacon, regular toast, and occasionally a banana. Follow this with a grilled "cheese" and french fry lunch, and cheese burgers, tater tots, canned corn, chip and salsa dinner. What made this worse was that the budget we were give to shop with was just appalling, so that even when a decent cook like myself was around, there was no way to afford anything of any quality at all. Mushy apples (the kind you buy in the 10lb bags), fake cheese, kleenex style bread, etc. And they wondered why the kids always gained weight; add the food to the fact that many of their medications sapped their energy, easy path to obesity. On the upside, I did learn to cook a mean pot roast (quite an accomplishment for a vegetarian), and my french toast was pretty solid. But still, with all of the money spent trying to address the kid's many mental issues, I was always amazed at how little attention was paid to their physical health. And, since we were their legal guardians, what kind of life lessons were we really teaching? OK, this has turned into a ramble, good night.