Friday, August 31, 2007

Scenic or desolate?

I had some grad students over for dinner during my last break, and one of them asked me if my field areas were scenic, or just desolate. I wasn’t sure what the difference was, so I figured I’d let y’all make the call. And maybe this guy can tell us how to tell them apart. Whatever you decide, this is where I’ll be for the next fortnight. Catch y’alls later…

Suggestions for science in high school

I recently heard from an old high school buddy with whom I had lost touch for a number of years. She is now an assistant principal at a 6-12 secondary school, and she is currently redesigning their science curriculum. She asked if I had any suggestions, and I told her that I could ask the science blogosphere, and she could stop by the lounge to see what people thought.

Now, I can’t guarantee she’ll actually visit the lounge, much less that she’ll care what any of y’all think. But if any of the scientists who read this e-rag have opinions on secondary school science curricula, feel free to introduce yourself in the comments here and state your opinion. With a little luck, one of the people crafting one such curriculum might possibly take note of what you have to say here.

Otherwise, she’ll have to go with what I told her are the four most important take-home points from the geosciences:

That the Earth is:
-less than 10 Ka old
-designed by an intelligent creator
-warming due to entirely natural causes.


Back in the middle Permian, Astropixie tagged me with the anecdote meme. Now, I lead a pretty boring life, so it has taken me a while to think up some events worth mentioning. And eight is a lot. But I’m leaving soon, so posting a book will give y’all something to doze off while reading for the next few weeks.

1. When we came into the last station on our first field tour of this season, there was a flock of hawks circling the corral. There must have been more than 50 of them, wheeling and soaring over the cattle yards. I’d never seen hawks flock before, and the sight of so many majestic birds was amazing.

The station manager was out, so we asked his partner, who was tending to the garden, what was going on.
“Do you guys have a plague of rodents?”
“Did the muster stir up mice or lizards or something.”
“Don’t think so. Why?”
“Well, you’ve got all these hawks up near the yards. We were just wondering if they are after something to eat.”
“Oh, yeah. The boys just castrated this year’s steers, so the hawks are probably looking for…”

We looked up in the sky again. The same hawks were flying. Only now, their curved talons looked more powerful, their hooked beaks crueler, less august. And that glint in their eyes looked considerably more antagonistic. We shifted uncomfortably from foot to foot.
“Look. I think it’s time we moved on up the road…”

2. The Thanksgiving after I finished hiking the Appalachian Trail, my brother and I had an eat-off. We weighed our plates before and after each course of the holiday feast, to determine who was the greater glutton. Although months of binge-and-fast eating had prepared my digestive system for the contest, I chose to rely on strategy as well as bile.

Knowing that my brother did not enjoy eating sweet potatoes, I went for the normal mash early, so that we rapidly demolished that and the turkey. With the mash, bird, and cranberry sauce depleted, I then turned to the orange root, while he was forced to consume Mom’s super filling whole-meal breadrolls. As they were a bit dry, he had to fill precious stomach space with water.

While I won the battle, I lost the war. He continued to grow into his college football O-line body and has soundly eaten me under the table every time since. I think he learned a lesson, though, as he also taught himself to cook, and he is now by far the most accomplished chef in the family.

3. In the second year of my PhD, I went to the Kimberlite Conference in Cape Town, along with several other students in our research group. A couple of us checked out the Lonely Planet guide for things to see. We are all of an age where the anti-apartheid leaders were childhood heroes of ours, and we realized that the diocese over which Archbishop Desmond Tutu presided was near our hostel, and that we would be in town for Easter Sunday.

Figuring that a sermon by one of the great moral crusaders of our time might be worth getting up in the morning for, we set our alarm clocks to hangover-banishing time, became Anglican for the day, and rocked up for the Easter Sunday Service. After doing all the standing up and sitting down whenever everyone else did, we eventually realized that the proceeding were being led by a boring old white guy who bore very little resemblance to the great Archbishop.

The white guy proceeded to give the most boring sermon that I have ever heard in any house of worship on this entire planet. He talked about fidelity to the church, and the important of obedience, and the danger of individuality and of questioning authority. He did not mention the freedom struggle, the new government, or even the historic Good Friday agreement signed three days before.

We stuck out the whole thing, partly because not even I am game enough to walk out of an Easter Service in a strange town, and partly because we clung to the forlorn hope that this guy was the Anglican version of a warm-up act.

It was not until much later, as we medicated the hazardous level of boredom with some beers, that we realized that our guidebook was out of date, and that the Archbishop traded in the preaching gig for the chairmanship of the truth and reconciliation commission several years before.

As we sat in the fine autumn afternoon, we wondered if there might be some sort of lesson in our getting bored out of our skulls by attempting to use a religious holiday to go celebrity spotting. After a few more fine Namibian lagers, though, we stopped wondering what that lesson might be.

4. I have never been overly enthusiastic about formal education. Throughout most of my overly drawn-out academic career, I have received A’s in the classes I liked, and C’s in the ones I didn’t particularly care for. But I didn’t really care one way or the other, with a single exception.

Brown University’s geology department did not offer its own field course when I was an undergrad. Like many east coast schools, it farmed its students out to whatever western course offerings we could get accepted to. I ended up going to Cal State Hayward, partially because it was small and different, but mostly because it was cheap.

As a quiet kid who grew up in a conservative East Coast suburb, and who never lived anywhere more flamboyant than Germany, Northern California was a bit of a shock to the system. Reticent around groups of strangers at the best of times, I simply slunk into the back corner of the classroom for orientation, determined to keep my own company.
The local students knew each other already, of course, and the professor gave th5e rest of us a short introduction, even though most of the other students had taken classes with the Hayward mob before, and only two of us were from East of the Mississippi.
Finally, the professor said who I was, and where I was from, and that was all OK. Except that he then continued….
“Now Chuck here is a bit of an unusual situation. We actually had more people apply to this course than we had places, so we had to turn a few people away, and Chuck was missing several pre-requisites for this class. But I thought his application essay was somewhat amusing, and if we’re all going to stay sane for the next six weeks, we’re gonna need some comic relief. So, I decided to bring him along. As for the prereqs, since this class is graded on a curve, you can all consider his inclusion a gift to your grades.

I was absolutely stunned. Nobody had asked me to entertain anyone ever before, much less an entire crew from whom I could not escape. And the curve comment was outright insulting. As I sat there, trying to figure out how to get my jaw back up to my mouth, only one thought registered in my mind. I HAD to get an A in that course.
In the first field area, I pushed so hard that my partner got exhaustion, slipped in an Arroyo, and busted several ribs. This cut into our mapping time, and my grade for that project. But after that I started to get canny instead of simply powering through, and I earned that A by the end of the course.

It was not until years later that I realized the professor had read me like a book.

5. When I first came to Australia, I tricked myself into thinking I was prepared by looking up Australian slang on the internet. Nothing I ever saw said anything about garnishes, so when it came my turn to cook in the share house I was in, I pulled out my American lasagna recipe and headed to the store. Once at the supermarket, I though nothing of grabbing a big jug of tomato sauce, oblivious to the possibility that it could be anything other than sauced tomatoes.

We sat down to eat, and after a bite I realized that something was amiss. The cheeses were blended fine, the pasta was well cooked, but the sauce didn’t seem quite right. It was unusually sweet, and extremely vinegary. Despite these obvious warning signals, I puzzled over the strange taste for several days, before a few chats with my native housemates and a good hard look at the ingredient list finally convinced me of what should have been obvious all along; in Australia, tomato sauce is the substance that American call Ketchup.

The really scary thing, however, is that my housemates said the lasagna tasted great.

6. I was a post doc in Washington DC during the sniper attacks in 2002. I suppose that in the long run it was good for me in that my cycle commute times dropped by 5-10 minutes for the duration, improving my fitness levels, but it was stressful at the time. I really wanted to let off some steam by calling up a radio station, and request Pat Benatar’s Greatest Hit with a dedication to the scumbag who was going around shooting up parking lots. But I was too cowardly, disorganized, and lazy to follow through with that plan.

7. I love hitch hiking. I’ve thumbed down rides of up to 200 km on 4 different continents. The people who give rides always have amazing stories, as boring folks generally don’t slow down. One of the oddest rides I scored, however, was more of a business transaction than a hitch.
I was in Idaho Falls in the summer of ’94, seeing the west and getting dissed by girls in the weeks between field school and the start of fall semester. And I was in a bit of a fix.

Greyhound had previously lost everything I owned save my wallet, my journal, and half a loaf of banana bread. More seriously, my grandfather had unexpectedly passed away back east, so I needed to catch a flight leaving from Jackson WY the next day. I decided to start hoofing it, realizing that my luck might be better the farther out of town I got. While walking, I came across a woman broken down on the side of the road. She had a flat, and didn’t seem real handy with a jack and a tire iron, so I bartered a repair for a lift to the Jackson Pass junction. Despite her not being a lift-giving regular, we engaged in the ritual chit-chat anyway, and it eventually came out that I was a geology student. This piqued her interest.
“Is it true,” she asked, “That the states of California, Oregon, Washington, and Idaho are going to fall into the ocean in 1998?”
It took every ounce of self control I had (e.g. both of them) not to say, “That’s right, ma’am. We’re all going to die.”

I haven’t used my thumb in anger since getting married, aside from an emergency situation on the honeymoon. It is one of those things where I don’t realize what I’m missing until sitting down and reminiscing. But these days, I wouldn’t hitch with the baby anyway- driving a bub without a properly installed car seat is just too risky.

So, that’s seven. One anecdote to go. So in order to liven this place up a bit while I’m out, I’m gonna do something foolhardy. I know there are people- people from my real life- who occasionally read this blog. Most of these folks are generally fairly shy when it comes to commenting. But all of them have at least a little dirt on me. So here is what I will do. I’m opening up anecdote #8 to the readership. If you have some illuminating, embarrassing, or remarkable occurrence that you’d like to share, post it in comments below. I’m off tomorrow, so I can’t even screen the comments or defend myself.

Monday, August 27, 2007

A gneiss town

There have been a lot of things written about Alice Springs over the years. However, despite the many descriptions and opinions of the desert atmosphere, the scenery, the culture, the art, and the politics, the town’s ductile deformation is rarely mentioned. Which is too bad.

Look at the above rock, from an outcrop on Bath Street. Viewed end-on, it could almost be mistaken for a granite porphyry. But a simple rotation out of the plunge direction shows extensive linear deformation. With rocks like this, who needs camel races?

Saturday, August 25, 2007

No Mercury Added

Starting about a year ago, I have seen the above slogan used increasingly in zinc-bearing goods, especially batteries made in China. It is one of those statements that is both technically correct, extremely misleading and dangerously deceptive.

The fact of the matter is that nobody ever intentionally added mercury to zinc products. This is why I have no doubt that the statement is correct. This is also what makes it misleading. The statement implies that Hg contamination is caused by an additive, kinda like lead in gasoline. But that implication misrepresents the most obvious source of mercury contamination.

A quick look at a periodic table will show that Zn, Cd, and Hg are all in column 2b, and one might surmise from this that they have broadly similar geochemistry. And indeed they do. In nature, they all occur primarily as +2 chalcophile cations, meaning that sulfur, and not oxygen, is their preferred anion in the Earth’s crust. Indeed, most zinc mined today is mined from sphalerite (ZnS) ore. But because of the similar chemistry of these three elements, Cd and Hg can, and generally do substitute for Zn in natural sphalerite to varying extents, depending on the particular mine and type of deposit. So in order to have zinc that is contaminated with Cd and Hg, you don’t need to add those toxic metals- they are often already in the orebody.

Therefore, the important health and safety question is not whether or not Hg has been added, it is whether or not the primordial Hg already present in the ore has been removed during the smelting and refining process. Most of the products I’ve seen with the “No mercury added” claim also say “Made in China” , a country not exactly famous for stringent environmental regulation of its heavy industry. So the fact that they put a true but irrelevant statement on their product does not exactly convince me that it is non-toxic.

In fact, it might be a fun undergraduate research project to figure out just how much Cd and Hg various zinc-based “no mercury added” products actually contain. Too bad I don’t work in a lab anymore…

Thursday, August 23, 2007

The outback winter... shorter than this blog entry.

Monday, August 06, 2007

Happy Hiroshima day!

Greetings from Alice Springs.
62 Years ago today, the first atomic bomb was detonated in anger.
I'm heading off into the desert to look for uranium.
Go figure.

Saturday, August 04, 2007

If you're looking for me...

I'll be in my office.*

* Office: place with no paperwork, no furniture, no books, no walls, no running water, no electricity, no surface water, no roads, and no people; the place I must go to earn my paycheck.

p.s. anyone getting restless is encouraged to try their hand at Where on (Google) Earth number 38.

Friday, August 03, 2007

Diffusion and melt inclusions

I haven’t written much about actual lab science recently, and Dr. Carl Spandler, a former postdoc of ours at the ANU, recently published a funky nature paper using data from our laser lab, so here’s a summary of what they did. I should point out that I didn’t do any of the gruntwork for this research. I did, however, provide some minor assistance for some of the followup studies.

A summary of the paper, and the abstract are free. The full paper requires a subscription.

But first, a description of melt inclusions.

As a magma (or silicate melt) cools, it starts to crystallize. In the case of basalt, the first crystals to form are generally olivine. Sometimes, as these crystals are growing, they grow in a geometry that allows a blob of the melt from which they grow to become trapped as an inclusion inside of the crystal. If the crystal is then transported somewhere else, it keeps this entombed blob of melt.

Sometimes, melt inclusions are anomalous. An anomalous melt inclusion in any melt inclusion with a trace element composition different to what one would expect to find. One trace elemental component that is often anomalous is the relative abundances of the lanthanides, known to geologists as the rare earth elements. For those who can’t remember the names of these elements, a mnemonic is available here.

In the Earth’s mantle, rare earth elements all generally occur as trivalent oxides in melts, silicates, or (rarely) phosphates. Because they have the same charge, similar oxygen affinity, and gradually decreasing ionic radius, their behavior in geochemical systems relative to each other can be predicted fairly well. Thus, deviations in the relative abundances of REE’s compared to a particular reference value are used to infer all sorts of geological stories.

Many anomalous melt inclusions have anomalous REE patterns, and these have been used to constrain the origin of these melt inclusions. For example, the heavy REE have a small enough ionic radius to easily fit into the crystal structure of garnet, while the light REE do not. So if a rock containing garnet partially melts, and that melt is in equilibrium with some residual garnet, then the melt will have a very high La/Lu ratio, because some of the rock’s Lu will stay behind in the garnet, while none of the La will.

Because garnet is only stable in the mantle at high pressures, a “garnet signature” REE pattern can be used to infer a deep source of melting- and most basalts do not show significant garnet signatures. A melt inclusion with a garnet REE signature in a rock with no bulk garnet signature would be said to be anomalous.

Of course, in order to be geologically meaningful, the REE in a melt inclusion have to be effectively trapped by the crystal. If the temperatures and residence times are too large, then solid state diffusion might allow the melt inclusion to equilibrate with the melt outside of the crystal. While most melt inclusion people have previously assumed that the existence of melt inclusions requires them to not re-equilibrate, the purpose of the experiments presented in the Spandler et al. paper was to determine whether or not REE diffusion can occur in typical magmatic systems.

So, this is what they did:
1. Get a population of normal MORB melt inclusions that were unlikely to have any anomalous inclusions in them.
2. Determine the temperature at which these inclusions were trapped in the host olivine.
3. Determine the composition of the olivine that traps the inclusions.
4. Calculate what the composition of a basalt should be, in order to be in equilibrium with the olivine at the trapping temperature of the inclusions, under a fixed fO2 and atmospheric pressure.
5. synthesize a basalt of that composition. A synthetic basalt made from lab reagents will have no REE in it.
6. Dope the synthetic basalt with several hundred ppm of the following REE: Pr, Eu, Tb, Ho, Lu
Presumably these were chosen for the following reasons: AS odd-numbered elements, they have lower abundance, so the ration of synthetic to natural is greater for a fixed concentration. Also, the detection limits and counting stats for the mass spec are better, because all but Eu are monoisotopic clear mass numbers, so you can count all the ions, not just those from a minor isotope.
7. Heat the synthetic basalt up to the trapping temperature, toss in the intact olivines containing natural melt inclusions, and let them sit for varying time periods.
8. Quench, extract the olivines, polish them down to expose the melt inclusions, and see if any of the doped elements diffused into the melt inclusions.

Not only did they find that diffusion occurred, but they were able to determine what the diffusion coefficients were. And applying those coefficients to magmatic systems showed that REE will diffusively re-equilibrate on a timescale of years. Short-lived nuclide and geophysical constraints suggest it takes thousands to tens of thousands of years for melts to migrate from their mantle sources to the surface. Thus, anomalous melt inclusions must be trapped in a late stage of magma migration, as any melt inclusion captured early on would re-equilibrate long before it was erupted the surface.

While the paper was languishing in review, Carl described the results in a talk at Goldschmidt. It was that talk that caused Al Hoffman to blow his top, which was highly entertaining for us pudknockers in the back row. But melt inclusion research is an incredibly finicky and laborious line of study, so I can see how being shown that it can’t possibly mean what you think it means could be upsetting.

Anyway, that’s the lab denizen’s view of the study. It would be interesting to see what a skeptical petrologist makes of it.

C. Spandler, H. St C. O'Neill & V. S. Kamenetsky 2007. Survival times of anomalous melt inclusions from element diffusion in olivine and chromite. Nature 447, 303-306

Spare a kind word for Sciencewoman

Sciencewoman is starting a new job, looking for childcare, and trying to adjust to a cross-country move using a moving company that operates using the geologic time scale. If that isn't enough, the IRS has issues with her taxes, her mom is sick, and some random numbskull who doesn't know his ass from a hole in the ground is whinging about her ability to nurture her beautiful baby. I'm starting to wonder if her new home town is Nashville, and if her dog and her truck are looking over their respective shoulders...

But the fact of the matter is that her down-to-earth style, scientific outlook, and extraordinary personal honesty make her one of the best science bloggers on the web, so if any of y'all wanna pop over to her place and write an encouraging word, I reckon she'd appreciate it.