The thrust belt in my driveway

It's snowed a lot in the past two weeks. Somewhere around two feet of snow fell between the last day of classes and December 26. Good for ski areas, but a lot of work to shovel. Fortunately, structural geology can make all kinds of difficult labor fascinating.

When you push a shovel through a relatively thin layer of snow, it piles up next to the shovel in a wedge shape. Push the shovel along, and the wedge gets longer and thicker, but it maintains the same shape: a triangular wedge, with a consistent angle at its front end.

Photo: a wedge of folded and faulted snow in my driveway, 12/22/08.


You see similar shapes in belts of thrust-faulted rocks from mountain belts all around the world, from the Himalayas to the Canadian Rockies to the Appalachians to Taiwan:

The cross-section above is from a classic paper by Davis, Suppe, and Dahlgren (1983) that explains what's going on mechanically in these wedges. The shape of the wedge is governed by a balance of horizontal forces: the push from behind the wedge; gravity, which would tend to flatten out the wedge (by moving material from the higher back part of the wedge to the front); and the frictional resistance to sliding, which tends to keep the front of the wedge from sliding along, causing the wedge to be steeper. The other big assumption is that the wedge is always just about to fail: its internal strength exactly balances the stresses that compress it. This means that the nature of the material also makes a difference - cohesive sheets of material behave differently from loose sand.

There's a lot of underlying math behind the explanation of wedge mechanics, but the cool thing about it is that it all boils down to a pretty simple concept. If the friction at the base of the wedge and the mechanical behavior of the rock (or snow) stays the same, the wedge should maintain the same shape. It can get bigger, but the front of the wedge should keep the same angle. That simple geometry has a lot of predictive power. It tells what should happen in a mountain belt that's eroded by a lot of rain or glaciers, compared to one that's in a rain shadow. It's been used as one explanation for the exhumation of high-pressure metamorphic rocks. And it solved a long-standing problem for structural geology: how could huge masses of rocks slide along a nearly flat plane for immense distances, as had been observed in places like the Canadian Rockies.

And it turns snow shoveling into an analog modeling experiment. Take a driveway made of smooth concrete. Drive a truck over it, and pack down snow in parallel ridges. Then let it snow another couple inches before shoveling the driveway. The results of the experiment look like this:


The wedge started out small. It's hard to see the exact structure forming - are there thrust faults beneath the folds on that surface? But it formed a nice taper, and slid along fairly easily. (Note the highly rigorous descriptions of basal friction from this experiment.)

I pushed the shovel a bit more, and the wedge got longer and thicker, but kept the same shape:


But then I reached the old tire track, and it suddenly got really hard to push that shovel. And the wedge looked like this:


The taper of the wedge suddenly got steeper, at least until I got past the tire track. But by that time I was experiencing significant edge effects, both from the top of the shovel and the snowbank beside the driveway, so the experiment ended.

The different snow storms led to somewhat different wedge shapes. Over Thanksgiving, we had a couple inches of wet snow. It formed a cohesive layer, and I could see the individual fault blocks. (I even had some tear faults separating thrust faults with different offset! Unfortunately, I didn't have the camera yet.) Before AGU, we had an inch or so of powder, which compacted somewhat when I shoveled it. And on Christmas night, we had about five inches of wet, heavy snow, and I stopped doing experiments because moving it was a lot of work, and besides, it kept falling over the top of my shovel.

My students still think that snow is for skiing, not for experimenting with structural geology. But if you've got to shovel, you might as well have geeky fun at the same time.

Reference: Davis, D., Suppe, J., and Dahlgren, F. A., 1983, Mechanics of fold-and-thrust belts and accretionary wedges: Journal of Geophysical Research, v. 88, n. B2, p. 1153-1172.

Photo note: I adjusted the levels on all the snow photos, because I haven't figured out how to take good photos of snow with my new camera yet.

Fresh dinosaur tracks

It's snowing. A lot. This morning, there was even a little snow on the walk under the eaves, outside my front door. And some tiny dinosaurs had been hopping there, looking for seeds in the dead plants:


Can I count this toward my list of geological things I've done?

(Also, since ice is a mineral, is snow a sediment or a volcanoclastic deposit? I know it's not metamorphic until it's been buried in a glacier, or at least buried in the snowpack and recrystallizes.)

I hope everyone has had and is having great holidays.

The stuff that comes home from a conference

I don't pick up as much stuff at conferences as I used to. I've stopped checking baggage unless I'm traveling with my kid, and I never have room to bring home books and flyers and toys. But it's hard to come home without picking up anything:


Counter-clockwise from top left: AGI's new materials for attracting students to the geosciences; my meeting program (with my scribbled notes from one session inside it); a publisher's book list; a CD from William Prothero, who spoke in my session; a free mini-fieldbook; a public transit map; a sticker from GSA; my name badge (along with a holder that I forgot to recycle); and a cool magnetic shapes game for my son (because it's never to early to learn about rotational symmetry, even if it's 7-fold).

Any suggestions as to where I should put the sticker? I'm considering my computer and my coffee cup at the moment. (The car is officially a sticker-free zone.)

(I had to use the new camera, even if it's for something that will make Chris Rowan jealous. I promise to show pictures of things like rocks or minerals soon, as penance.)

AGU non-blogging

I'm at AGU (after a rather eventful travel day that included a cancelled flight and a broken de-icer, among other things). I'm not live-blogging it, but maybe if I have time, I'll blog about at least one of the sessions I went to:

Early morning: Teaching Geoscience in the 21st Century posters. (Saw a few posters, had long conversations - mostly about teaching - with people I knew from the Teaching Intro Geoscience workshop. I have more ideas to steal now.)

Late morning: Exhumation of High- and Ultra-high Pressure Rocks: the cross-disciplinary view. I will blog more about this if I find the time - this is the research that I wish I had gotten into as a grad student, and which still fascinates me.

Gabbed with former thesis student. Ran into some grad school friends in the hall. (Scientists have a reputation as anti-social. It's a big lie.)

Early afternoon: Plate motion and its relation to deforming zones. I find high-precision GPS data fascinating, and wanted to learn more about it. I'm not in this field (and never have been), so I don't have a good handle on what is new and exciting (other than being able to really truly see active deformation, which is exciting enough for me). I probably won't blog in detail on it, but it was an interesting session.

Late afternoon: Teaching Introductory Geoscience: Staying Relevant in the 21st Century II. This was my session. Maybe I'll blog about what I'm doing at some point. I won't blog about the other talks, because I was busy trying to remember what I was going to say in mine. (I have this problem in sessions all the time. It's a shame, because I miss learning interesting things related to my own research interests.)

Ran into a college friend who I thought had become a biologist. Gabbed.

Had a late dinner with geology bloggers. (Scientists are social, remember.)

And now I'm here, and need to go to bed, so I can get up, have a too-short day, and run back to the airport to go home.

AGU has grown a lot since I was here last - I wish I was staying longer.

Geologists' 100 things meme

The geologist's 100 things meme, from Geotripper.

Bold the ones you have done:

1. See an erupting volcano [Kilauea, barely oozing lava at the time, but still thrilling.]
2. See a glacier [A couple in the Alps, including the spectacular Gornergrat. One had signs showing the location of its toe through the years. It had receded a lot - and I visited it in 1991.]
3. See an active geyser such as those in Yellowstone, New Zealand or the type locality of Iceland [Yellowstone.]
4. Visit the Cretaceous/Tertiary (KT) Boundary. Possible locations include Gubbio, Italy, Stevns Klint, Denmark, the Red Deer River Valley near Drumheller, Alberta. [The local K-T boundary is an unconformity. I think. If it's not, then I've seen it.]
5. Observe (from a safe distance) a river whose discharge is above bankful stage [It was a stream, really, and it wasn't a safe distance.]
6. Explore a limestone cave. Try Carlsbad Caverns in New Mexico, Lehman Caves in Great Basin National Park, or the caves of Kentucky or TAG (Tennessee, Alabama, and Georgia [I'm fairly claustrophobic, so I've only been into caves with lights and tours and stuff. Most recently, Lehman Caves, which are beautiful.]
7. Tour an open pit mine, such as those in Butte, Montana, Bingham Canyon, Utah, Summitville, Colorado, Globe or Morenci, Arizona, or Chuquicamata, Chile. [The most impressive was the Homestake Mine in South Dakota, which I visited on an undergrad field trip.]
8. Explore a subsurface mine. [As a tourist, in the Upper Peninsula of Michigan most memorably.]
9. See an ophiolite, such as the ophiolite complex in Oman or the Troodos complex on the Island Cyprus (if on a budget, try the Coast Ranges or Klamath Mountains of California). [Coast Range ophiolite.]
10. An anorthosite complex, such as those in Labrador, the Adirondacks, and Niger (there's some anorthosite in southern California too). [The Adirondacks.]
11. A slot canyon. Many of these amazing canyons are less than 3 feet wide and over 100 feet deep. They reside on the Colorado Plateau. Among the best are Antelope Canyon, Brimstone Canyon, Spooky Gulch and the Round Valley Draw.
12. Varves, whether you see the type section in Sweden or examples elsewhere. [Remnants of Glacial Lake Vermont. Not a good place to chew silt and clay - there was a cow pasture above the exposure.]
13. An exfoliation dome, such as those in the Sierra Nevada. [Yosemite.]
14. A layered igneous intrusion, such as the Stillwater complex in Montana or the Skaergaard Complex in Eastern Greenland.
15. Coastlines along the leading and trailing edge of a tectonic plate (check out The Dynamic Earth - The Story of Plate Tectonics - an excellent website). [Japan, and the coast of Maine.]
16. A gingko tree, which is the lone survivor of an ancient group of softwoods that covered much of the Northern Hemisphere in the Mesozoic.
17. Living and fossilized stromatolites (Glacier National Park is a great place to see fossil stromatolites, while Shark Bay in Australia is the place to see living ones) [Upper Peninsula of Michigan.]
18. A field of glacial erratics [Do the woods behind the house where I grew up in Maine count?]
19. A caldera [Long Valley, Yellowstone, Silverton, Lake City...]
20. A sand dune more than 200 feet high
21. A fjord [Technically Somes Sound in Acadia National Park is a fjord.]
22. A recently formed fault scarp [Borah Peak earthquake.]
23. A megabreccia
24. An actively accreting river delta [There are small ones into every reservoir around here.]
25. A natural bridge
26. A large sinkhole
27. A glacial outwash plain [Where the glaciers in the Alps were receding.]
28. A sea stack [Coast of Oregon.]
29. A house-sized glacial erratic [In the woods in Maine.]
30. An underground lake or river
31. The continental divide [Only the Atlantic-Pacific one in the US. But I have to cross it all the time.]
32. Fluorescent and phosphorescent minerals [Only in museum displays.]
33. Petrified trees [Only in the department rock collection; not in the field.]
34. Lava tubes [Hawaii.]
35. The Grand Canyon. All the way down. And back. [Only from the rim.]
36. Meteor Crater, Arizona, also known as the Barringer Crater, to see an impact crater on a scale that is comprehensible [Only from the air.]
37. The Great Barrier Reef, northeastern Australia, to see the largest coral reef in the world.
38. The Bay of Fundy, New Brunswick and Nova Scotia, Canada, to see the highest tides in the world (up to 16m)
39. The Waterpocket Fold, Utah, to see well exposed folds on a massive scale.
40. The Banded Iron Formation, Michigan, to better appreciate the air you breathe.
41. The Snows of Kilimanjaro, Tanzania,
42. Lake Baikal, Siberia, to see the deepest lake in the world (1,620 m) with 20 percent of the Earth's fresh water.
43. Ayers Rock (known now by the Aboriginal name of Uluru), Australia. This inselberg of nearly vertical Precambrian strata is about 2.5 kilometers long and more than 350 meters high
44. Devil's Tower, northeastern Wyoming, to see a classic example of columnar jointing
45. The Alps.
46. Telescope Peak, in Death Valley National Park. From this spectacular summit you can look down onto the floor of Death Valley - 11,330 feet below.
47. The Li River, China, to see the fantastic tower karst that appears in much Chinese art
48. The Dalmation Coast of Croatia, to see the original Karst.
49. The Gorge of Bhagirathi, one of the sacred headwaters of the Ganges, in the Indian Himalayas, where the river flows from an ice tunnel beneath the Gangatori Glacier into a deep gorge.
50. The Goosenecks of the San Juan River, Utah, an impressive series of entrenched meanders.
51. Shiprock, New Mexico, to see a large volcanic neck
52. Land's End, Cornwall, Great Britain, for fractured granites that have feldspar crystals bigger than your fist.
53. Tierra del Fuego, Chile and Argentina, to see the Straights of Magellan and the southernmost tip of South America.
54. Mount St. Helens, Washington, to see the results of recent explosive volcanism.
55. The Giant's Causeway and the Antrim Plateau, Northern Ireland, to see polygonally fractured basaltic flows.
56. The Great Rift Valley in Africa.
57. The Matterhorn, along the Swiss/Italian border, to see the classic "horn".
58. The Carolina Bays, along the Carolinian and Georgian coastal plain
59. The Mima Mounds near Olympia, Washington
60. Siccar Point, Berwickshire, Scotland, where James Hutton (the "father" of modern geology) observed the classic unconformity
61. The moving rocks of Racetrack Playa in Death Valley
62. Yosemite Valley
63. Landscape Arch (or Delicate Arch) in Utah
64. The Burgess Shale in British Columbia
65. The Channeled Scablands of central Washington
66. Bryce Canyon
67. Grand Prismatic Spring at Yellowstone
68. Monument Valley
69. The San Andreas fault
70. The dinosaur footprints in La Rioja, Spain
71. The volcanic landscapes of the Canary Islands
72. The Pyrennees Mountains
73. The Lime Caves at Karamea on the West Coast of New Zealand
74. Denali (an orogeny in progress)
75. A catastrophic mass wasting event [Not in progress, but recent.]
76. The giant crossbeds visible at Zion National Park
77. The black sand beaches in Hawaii (or the green sand-olivine beaches)
78. Barton Springs in Texas
79. Hells Canyon in Idaho
80. The Black Canyon of the Gunnison in Colorado
81. The Tunguska Impact site in Siberia
82. Feel an earthquake with a magnitude greater than 5.0.
83. Find dinosaur footprints in situ
84. Find a trilobite (or a dinosaur bone or any other fossil)
85. Find gold, however small the flake
86. Find a meteorite fragment
87. Experience a volcanic ashfall
88. Experience a sandstorm
89. See a tsunami
90. Witness a total solar eclipse
91. Witness a tornado firsthand. (Important rules of this game).
92. Witness a meteor storm, a term used to describe a particularly intense (1000+ per minute) meteor shower
93. View Saturn and its moons through a respectable telescope.
94. See the Aurora borealis, otherwise known as the northern lights.
95. View a great naked-eye comet, an opportunity which occurs only a few times per century [I've seen the Northern Lights and one of the spectacular comets of the 1990's at the same time. Possibly the most amazing thing I've ever witnessed.]
96. See a lunar eclipse
97. View a distant galaxy through a large telescope
98. Experience a hurricane [A small one. I didn't know at the time that "typhoon" and "hurricane" were the same things.]
99. See noctilucent clouds
100. See the green flash

There are several of these that I haven't done, but which I could do within a day's drive of my house. Kind of embarrassing - I've lived here longer than I've lived anywhere but Maine, by this point.

My five-year-old is losing his apatite

My five-year-old has cavities. Four cavities. Two on his lower left, where his back teeth rub together, and two little ones in the same spot on his lower right and upper left. I've never had any cavities myself, so I may be more worried about the next dental visit than he is.

"Does he drink a lot of juice?" the hygienist asked me.

"No..." I frowned. "But I've been letting him brush his teeth himself. He might not be doing a very good job."

"The chewing surfaces look fine," the hygienist said. "He's got to get the sugar between his teeth to get his cavities. Usually it's fruit juice that does it."

"He drinks mostly milk and water," I said. "What else could it be? We don't do very good job flossing his teeth, I know. And... we were on well water until this summer. I never got the water tested for fluoride, and the dentist didn't want to give him extra fluoride, because the groundwater around here varies alot." I didn't go into detail about the diverse bedrock geology that contributes to the variability in water chemistry. I was busy feeling guilty because I had treated the problem as something to solve by knowing more about the bedrock, when I should have just sent the water to the local health department for a fluoride test.

See, I don't know much about teeth, except that brushing and flossing every day is good, eating lots of sugar is bad, and the enamel coating consists mostly of the mineral hydroxyapatite. And that tooth decay happens because sugar-eating bacteria excrete weak acids, which slowly etch the hydroxyapatite and destroy the enamel.

Apatite is a mineral that all geologists learn at least in passing – it defines “5” on Moh’s hardness scale, it’s the most common of the phosphate minerals, and it’s got a funny name. And it’s present in a lot of different types of rocks, igneous, sedimentary, and metamorphic. I usually miss it when glancing at a thin section, but find it on a microprobe, when I’m actually looking for tiny grains of plagioclase feldspar. But most of what I know about apatite comes secondhand, from collaborating with thermochronologists, who use apatite to figure out when rocks cooled to near-surface temperatures. (Well, that’s near-surface to someone who likes to work on metamorphic rocks.)

When I was in grad school, apatite was mostly used for apatite fission-track dating*. Apatite is mostly a calcium phosphate mineral, but it can contain tiny amounts of uranium. When the uranium decays by nuclear fission, it damages the crystal lattice of its host apatite grain. If the temperatures are high enough, the lattice is able to heal, but at low temperatures, the apatite grain collects these damage zones called fission tracks. You can’t see the fission tracks in a normal thin section – you need to separate the apatite grains, mount them in epoxy, polish them, and etch the surface with an acid. Then the heroic (and very patient) thermochronologist counts and measures all the little etched tracks. But there are complications. And one of those complications has to do with the amount of fluorine that substitutes for the hydroxy (OH-) ions in the structure.

I don’t remember exactly what the complication was. But I’m willing to bet that fluorapatite isn’t just harder than hydroxyapatite. I’m not sure, but I think that fluoroapatite doesn’t dissolve as easily in acid.

My son's cavitities are in baby teeth, which is a good thing. They will fall out before enough fission tracks can accumulate in them to be countable. They will fall out and be replaced by adult teeth. Which are currently growing. Which is why the dentist prescribed supplementary fluoride tablets, for a little while, at least.

In the meantime, the hygienist and I came up with another hypothesis for the source of the sugar.

“Ummm,” I said. “When he started kindergarten, he was able to choose from white milk or chocolate milk. I think he drinks chocolate milk a lot.”

“Chocolate milk has sugar in it,” she nodded.

In fact, I think he’s been drinking chocolate milk nearly every day since starting kindergarten. I had encouraged him to try the white milk, and to save the chocolate milk for special occasions. But, well, he’s five. There are a lot of special occasions.

But now, maybe he’ll listen to me when I tell him that chocolate milk will destroy his apatite.

* Since I left grad school, a new method, (U-Th)/He dating, has been developed and become an incredibly powerful tool for thermochronology.

What does a scientifically literate person need to know about the geosciences?

What, exactly, are the earth sciences about, anyway? Even using the name "earth sciences" is a way of waffling - geology, geophysics, and geochemistry obviously fit, but what about paleontology, the oceans, climate, the atmosphere, other planets...? I don't have a clear answer for myself (although I should - I teach the only college-level Earth Science course that some future K-6 teachers take), but NSF has brought together a group of earth scientists to figure it out. They've put together a draft document, opened it for one round of comments in October, and now (starting December 15) they are looking for comments on the final draft. The draft itself (and links to a page for commenting) is available here: The Earth Science Literacy Initiative.

Here are the nine Big Ideas that they have proposed:

1. Earth science explores our planet.
2. Earth is 4.6 billion years old.
3. Earth is a complex system of interactions between rock, water, air, and life.
4. Earth is a continuously changing planet.
5. Earth is a water planet.
6. Life evolves on a dynamic Earth and continuously modifies Earth.
7. Humans depend on Earth for resources.
8. Humans are threatened by Earth's natural hazards.
9. Humans have become a significant agent of change on Earth.

The meat of the document comes in the supporting statements within each Big Idea. Check it out and comment (starting Monday).

There will also be three sessions at AGU where you can discuss it:

Monday 2:10 - 2:25 pm, Room MC 3011:
Oral Session ED13D: Earth Science Literacy: Building Community Consensus

Tuesday 8:00 am, Hall D:
Poster ED21A-0601: Earth Science Literacy: Big Ideas and Supporting Concepts

Thursday 6:15 pm, Moscone West 3005
Open Town Hall Meeting: Developing a Framework for Earth Science Literacy

(H/T Barb Tewksbury.)

Can't go to AGU? Here are some ways to get your fix.

Not going to be in San Francisco next week? Don't want to miss out on the American Geophysical Union meeting? Here are some other ways to keep up with what's going on:

AGU will have live webcasts of one or two sessions each day:

Monday, 15 December,
0800h–1000h, U11C - MESSENGER at Mercury: The Second Flyby I

0830h–1930h, U15A - Frontiers of Geophysics Lecture: The Spread of Scientific Knowledge From the Royal Society to Google Earth and Beyond

Tuesday, 16 December
1020h–1220h, U22B - The Great 2008 Wenchuan Earthquake: A Multidisciplinary View II

Wednesday, 17 December
0800h–1000h, U31B - Episodic Tremor and Slip I: Field Studies; A Growing Cottage Industry

Thursday, 18 December
1020h–1220h, U42B - Interaction of Earth Reservoirs

Friday, 19 December
1020h–1220h, H52B - Arsenic and Other Metals as Contaminants in Hydrologic Systems

(I may have to turn on the Mercury session on Monday morning while I'm frantically writing my final exams. Planetary geology is just plain amazing.)

For commentary, Erik Klemetti may try live-blogging from his new iPod. And last year, one of the RealClimate contributors live-blogged some of the climate sessions - I don't know if they're planning to do the same thing this year. As for me - I'm not going to try to blog the meeting; I learned at GSA that I would rather talk to people face-to-face when I've got the chance. If I see anything that I want to share, I'll try to post about it later. (I blog on a geologic time scale anyway, so I figure that I can keep talking about things I saw at this year's meetings for the next billion years or so, right?)

Goals for the next year

It's still the beginning of December, and I know the tradition is to review the last year before AGU, and do resolutions after. And the geoblogosphere is doing the first-post-of-the-month meme. But it's not just the beginning of the last month, the end of classes, and the week before AGU for me. It's also my 42nd birthday, and in celebration of the number 42 and the answer to life, the universe, and everything, I'm going to skip straight to plans for the next year.

In the next year I want to:

- Put more miles on my bike, skis, and feet than I do on my car. ("Better start taking long bike rides," says my husband. Bad news, because I prefer to run. But I was doing 20-mile weeks a few years ago while training for a marathon; I would like to get back to that kind of mileage.) If I can't pull it off, I want to at least do two running races: the Mother's Day 10K trail race (with free chocolate) and the Thanksgiving Day Turkey Trot. Both start within a bike ride's distance of my house, too.

- Get one paper sent off to a journal. I know this doesn't sound very ambitious, especially for people who are still actively in the job hunt. But for me, it's more about not feeling guilty than about being a super-productive scientist. Finish the paper, stop feeling lousy about myself.

- Follow through on at least one really crazy idea. Could be a research idea, could be a teaching idea, could be some kind of non-work thing that I'm scared to try. (Husband says I should do this 42 times, but when I say follow through, I mean really follow through. It could take a year or more to really give a crazy research or teaching idea a chance.)

- Avoid unpleasant interpersonal politics. I've been lucky this year - I've been on good committees, my department is getting along, and the geoblogosphere has been pleasant. I'm going to try to continue the pattern.

- Post more pictures. I got a new camera for my birthday. Now I need to learn how to use it (and how not to break it).

Oh, and unrelated: for an AGU meetup, how about at the Thirsty Bear (661 Howard St., SF) at 7:30 pm on Wednesday, December 17?

Geobloggers at AGU

Geobloggers (and anyone else who wants to come) are planning to get together on Wednesday night (one week from tomorrow!) at AGU. And... well, we haven't made any plans beyond that. Let's make some.

Here are my constraints: I'm giving a talk that ends at 5:30 pm, and my session ends at 6. (And it would be kind of rude to give my talk and run.) I think Brian's session is earlier in the afternoon?

I don't have any suggestions for where to meet - I haven't been to San Francisco since 1999 (which wasn't even this century, and yes, that does make me feel old, especially today). Apparently the Moscone Center is twice as big as it used to be, too. So Bay Area locals (Brian? Andrew?) - any suggestions for a time and place? AGU has also gotten even larger in the past nine years, so I'm guessing that restaurants are hard to find (except that San Francisco should still be better than Houston after a major hurricane... well, unless there's an earthquake this week, which I most fervently hope there is not).

Edit: How about the Thirsty Bear at 7 pm?


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Old dogs and new tricks

I've just realized that I'm going to be giving my first AGU talk (ever) in a week and a half.

It's actually kind of scary, even though I've spent way too many person-hours talking to darkened rooms in my career. (And even though I'm not going to be trying to impress potential employers; this will be my first AGU meeting when I don't need to look for a job.)

Field work: this might be heaven or this might be hell

I love field work. No, really, I do. But when I tell stories about it, they always end up being about running out of food or wrecking vans or collecting samples of giant mosquitoes by slamming a field notebook shut or not being able to find a single sample of high-pressure metamorphic minerals except trapped as inclusions in a garnet. (And that was just my PhD area.) I've thrashed through ice-storm-damaged woods, taking an hour to walk a mile, in search of non-existent staurolites. I've fallen into streams. I've broken a canoe paddle while trying to cross a melt-swollen river. I've post-holed through snow banks. I come back from the field covered in mud, sweat, scratches, bruises, and occasionally blood from where my hammer missed the chisel and slammed the back of my hand.

Which makes me wonder, while lying in a tent with an aching back and wondering whether that sound outside is a hungry bear or just a vole with insomnia, whether it's worth it.

Then I come back to the human world, where people care about things like other people's shoes*, and I think: worth it? Are you kidding?



Photo: me, someplace where the temperatures are cold and the rocks are hot. In other words: someplace close to heaven.

(For the November Accretionary Wedge.)

* Edit: a story, in explanation. In my second or third year in my previous job, I was a junior faculty member on one of those campus-wide committees. Before one snowy winter meeting, I found myself outside the meeting building with the committee chair, a faculty member in another department on campus. She said to me: "Isn't the etiquette of Vermont winters funny? It's inappropriate to look at other people's shoes until they've had a chance to change them." I was flustered and had no idea what to say; I generally changed into indoor shoes because my winter boots were snow-covered, muddy, and made my feet sweat. It had never occurred to me that I was being judged by my footwear.

I failed to successfully negotiate the social boundaries between effective teaching, interesting research, and the expected image of a female faculty member. My favorite field area was in northeastern Vermont - although it was in dense, bug-filled woods, it was the first place where I found surprising results and struggled through to models that were my own, not my advisor's or another mentor's. And I haven't been back there since I was denied tenure.

I've found a new, beautiful place to work. I haven't had the thrill of finding things that are unexpected yet. But there are beautiful views, and in Durango, nobody cares what I wear.

National Student Exchange

Fort Lewis College has recently re-joined the National Student Exchange, a program that allows students at many colleges and universities in the US and Canada to study at another institution in North America. Geology students usually get to study in another part of the continent (or sometimes the world) during field camp, but NSE makes it possible to spend an entire year in another geologic setting.

Most of the schools that participate are public colleges and universities. There's a complete list on NSE's web page. If anyone is interested in coming to Durango for a year and wants information about how the geology courses at Fort Lewis would fit into their home institution's major, please feel free to contact me. (shearsensibility AT gmail DOT com, or in comments, or by googling my name and sending me an e-mail at work).

Opportunities for grad students interested in working in national parks

From a friend who now works for the National Park Service: Park Break.

If you're a grad student interested in a career working in a national park, you can spend spring break learning about national park management and research careers. Park Break is designed to give graduate students experience that could lead to work in a national park. And for geoscience students, it could lead to a summer internship through the GeoCorps program.

Applications for Park Break are due by December 31, and applications for the GeoCorps program are due by January 31.

Experience with non-PV solar technology?

Does anyone out there have experience working with non-photovoltaic solar technology? Anything from the theoretical to building your own solar hot-water heater? I've got a writer friend who is working on an article on solar thermal technology. She's especially interested in talking to people who have experience with small-scale projects (like a water system for a home), but she's interested to talking to anyone who can help her understand the background, too.

I vaguely remember talking about semi-off-the-grid ideas when I was in high school. (A friend had an indoor swimming pool that may have been partly solar, but I think it was also heated by a wood stove. That was Maine, and the sun doesn't shine as much there as it does in Colorado.) But although I know people from grad school who rebuilt diesel engines to run on used cooking oil, it's been a long time since I've talked to anyone who does their own passive solar. (Beyond south-facing windows, that is.)

If you've got experience or know people who do, could you e-mail me (shearsensibility AT gmail DOT com), so I can pass contact information along to my friend?

How important are GRE scores for geoscience grad school?

I took the GREs twenty years ago this month. Twenty years! I spent an entire day of my Christmas break in a big lecture hall at the University of Maine, filling in bubbles with my #2 pencil.

The world has changed in the past twenty years. GREs are taken on computers these days, and the bizarre but fascinating logic problems are gone. ("Jenny likes cabbage, but Fred is allergic to horseradish. Who is seated beside Louise?") There's a new writing section, along with the verbal and math sections. And there's no longer a geology subject test. So I've become less and less capable of giving any kind of reasonable advice to students about how to prepare for it. And because I don't read grad student applications, I don't have any idea how grad schools look at the current version of the test.

When I started grad school, I got the impression that the GREs weren't particularly important for anything except competing for NSF graduate fellowships. Research is not a multiple choice exam, and the ability to fill in little bubbles (or whatever mouse-click has replaced it) is no substitute for creativity, perserverence, and the ability to take a lot of criticism. I've gotten the impression that the things that matter for a graduate application are 1) a coherent statement of purpose that fits with the research interests of a faculty member; 2) good grades in relevant coursework (maybe geo, maybe math or chemistry or physics); 3) strong letters of recommendation; and 4) maybe research experience, although it's become common enough at the undergraduate level that it might not mean as much these days unless it's incorporated into the statement of purpose. The GREs - well, the general test is taken by everyone, from physicists to literary scholars, and it would be hard to come up with a test that could identify people who would be skilled at both subjects. I remember the verbal section as being essentially the SATs with longer words (but not geology jargon), and the math section as being algebra. I took it, I sent off the scores, and I never thought about the test again*. Until students came to me worrying about it.

So here's my question to the rest of the world. Based on your experience, do GRE scores matter? Do some schools put more weight on them than others? Is there a minimum cutoff score for some schools, or are they used as a tie-breaker between otherwise similar applications? Or are they a form of practice at jumping through hoops, preparation for things like dissertation formatting instructions?

*Well, other than to score geek points against my soon-to-be-ex college boyfriend. But once I got to grad school, I didn't think about the scores.