Where on (Google) Earth #19

I'm still learning how to insert pictures into blogspot posts (and, actually, how to collect images from Google Earth). Apologies if this is small. (And if you've got hints about how to make these come out better, please share!)



Also, as another aside - has anyone tried to use something like this game in teaching? I think it could be a fun extra credit exercise - put up one Google Earth image a week, and have students e-mail me their guesses about where it is, and what it shows.

rediscovering the joy in field work

I became a geologist because I love to be outside. It's that simple, really. The chemistry lab smelled bad and I couldn't wear my contacts; geology labs involved things like hiking out to a flooding river and watching how it behaved.

But something funny happened on the way to a career. Field work became a drag.

It happened in fits and starts. First it was field camp. The TA hit on me, my field partners on one project spent an entire day saying unpleasant things about their girlfriends, and I simply didn't walk fast enough. And I didn't know the stratigraphy, and I didn't know the fossils, and I didn't carry enough water. I felt incompetent. But I must not have been, because the instructor recommended me for one of those USGS internships for the next summer. And after spending a summer working in geochemistry labs during the week and hiking on weekends, I realized that I really did need the outdoors, regardless of my field camp experience.

So I went to grad school and became a structural geologist. But the field work... was frustrating. I wasn't fast enough. We ran out of food (which is a particularly big deal when you've been dropped off by helicopter for three weeks). I was scared of heights, but I had to keep up with my field partners. Oh, and the rocks were not what they were supposed to be. "The map is not the territory..." especially when the original mapper didn't actually walk most of the ground.

I finished my PhD, despite actively loathing it by the end, and got a job (which was a pretty amazing feat, given that I thought my PhD was rather unimpressive, and given how much trouble my colleagues had finding work). And the next summer, I needed to find a field project for a student. And I found one, and the problem turned out to be more interesting than I had expected, but it took years to work it out. And every year, the same fear hung over my head: what if I'm wrong about this? What if I can't find the right rocks? What if I can't publish anything? What if I can't get funding? So I didn't much like the bugs, or the thrashing through the brush, or the long drive to the field area, or the negotiations between the bickering students. It was an important part of my life, but it wasn't something that I looked forward to.

And, although the research started going well by the end, the fears turned out to be justified. I didn't get tenure. So I got another job (which, again, was pretty darn lucky, under the circumstances). But this time, I decided not to commit myself to a new field area. I was tired. Tired of thrashing through the woods and finding nothing. Tired of working to learn a new area only to lose my job. Tired of expectations.

Fortunately, the expectations at my current job are pretty low. I'm a competent teacher, and I advised some research students, and I had enough ideas left over from my previous job that I published a little. Oh, and I co-wrote an instrument grant proposal, and it got funded. I guess that probably counted for a lot. Anyway, I got tenure despite not really having an active field area.

And I had a baby in there, as well. The first couple summers, the physical demands kept me home, and then the emotional demands kicked in. And, honestly, the kid made a good excuse. I didn't know what I wanted to do, and I didn't have any collaborators (either students or faculty) to brainstorm with, and it was very easy to live down to low expectations.

But finally the ideas started finding me. A grad student working in the area shared his conclusions with me, and one of his samples made me curious. So I talked an undergrad into looking at the rocks with me last summer, and she's going to work on them for her senior thesis. And for the past two weeks, we've been going out into the field to look for more samples.

Except that we ran into a few problems. The interesting rocks are in a wilderness area, on the opposite side of a small river from the main trail. I thought we would be able to cross the river on a bridge on private property, but it turns out that we would also somehow have to scale a major cliff with our backpacks. The property owner offered to let us use her horses later in the summer, when she finishes bringing them up to the high country and when the river is lower. But for now... we couldn't wade it, and we broke a canoe paddle trying to get across in a boat. So we put off that part of the work, and just spent some time doing reconnaissance on some related rocks.

And it was so cool. We hiked long days, we carried heavy packs, we scrambled up cliffs, we got rained on, we forded snowmelt streams, we headed back early because the strong winds were blowing down trees... and we looked at rocks, and compared observations, and saw things that hadn't been discussed by previous mappers, and brainstormed ways to test competing models, and tried to figure out ways in which some previous conflicting observations could be reconciled. And it was beautiful. The smell of the pines after a rain, the sound of rushing water, and the look of river-sculpted metamorphic rocks.

I don't know why, suddenly, it was so much fun. Maybe because the pressure was off, finally. No PhD qualification looming, no threat of tenure review, not even the fear that my student wouldn't have a thesis -- she already has some rocks from last summer, and this is an undergrad project. Maybe it was because there weren't any men along, and there wasn't this constant sense of having to prove how tough or competent I am. Maybe it was because I had been away from it for a long time, and there's nothing like a few summers dealing with office politics to make dirty socks seem like the most wonderful thing in the world.

But it doesn't really matter. Because for right now, for this particular moment, I'm enjoying what I do. And a year ago - even six months ago - I couldn't say that.

field notes of the day

I've spent the last several days camping and doing field work. The weather's been wild - first it was hot, and the streams ran high with the snowmelt; then a cold front blasted through, blowing over trees with gusts as high as 60 mph; then it was lovely again; then it rained again. This might be normal in, say, New England, but June is typically our driest month (though rivers usually are high, and snow lingers near treeline).

Tuesday morning's weather was cold and damp, with drizzle off and on. I was up nearly an hour and a half before my field partners, but I didn't have the heart to shake their tent, what with the rain and all. So I made some oatmeal and then watched the birds while I sipped coffee. We were only about a thousand feet higher than my house, but up in the Ponderosa/Douglas fir forests, the birds are quite a bit different. For instance, there are Steller's jays up in the tall trees, but not in the scrubby forest where I live.

One bird that seems to be everywhere, though, is the broad-tailed hummingbird. I grew up with hummingbirds back East, but they were hard to notice - so fast, and so little, and so quiet. But the broad-tailed hummingbirds make this loud buzzing noise when they fly - it sounds almost like an insect, or like high-voltage power lines, or like somebody running a blender in the distance. So these birds, I notice. For some reason they fly up at the elevation of the Ponderosa branches, rather than down where all the small flowers are blooming. Maybe their nests are up there. But they still pause and hover at each branch for a moment, as if they expect the pines to suddenly burst into flower.

So I was watching the hummingbirds hum, when suddenly, one appeared about six inches in front of my face. I looked at him. He looked at me. He hovered for a moment, eyeing my red coffee mug, then zipped away.

I guess he was a coffee purist, and was horrified that I add hot chocolate to mine.

Or maybe it's just that a bird whose wings beat 50 times in a second doesn't really need caffeine.

the rheology of women in science

I'm multitasking, bouncing between reading a classic structural geology article, brainstorming possible speakers to invite to campus next year, and mulling over the implications of Virginia Valian's tutorials about gender schemas and science (mentioned in this month's Association for Women Geoscientists newsletter). And it struck me: the experience of women in science (and, according to Dr. Valian's work, a lot of other fields, as well) feels like strain hardening.

Rocks may seem solid when we stub our toes on them, but rocks actually can change shape in a lot of different ways. There's brittle behavior - breaking rocks. That's fairly familiar - my four-year-old has even been experimenting with brittle behavior by dropping rocks onto one another and watching them smash into little pieces. Brittle behavior is responsible for things like earthquakes. Rocks near the earth's surface are brittle.

And then there's a whole suite of ductile deformation mechanisms -- ways in which rocks change shape without breaking, the way Silly Putty does. There's pressure solution, in which minerals dissolve because they've been pushed against one another too hard. There's Coble creep, which sounds kind of like somebody you would avoid sitting next to at lunch, but which really is just a way in which atoms move through the space between mineral grains. It's like pressure solution without the water. And there's Superplastic Creep, which isn't really capitalized, but really, how could I avoid capitalizing something that sounds like the ultimate geeky superhero? In superplastic creep, small grains both change in shape (maybe by pressure solution or Coble creep) and slide past each other.

All three of those mechanisms ought to let rocks deform more easily when the rock is made of smaller pieces of stuff - they should experience "strain softening," in which deformation gets easier as time goes by.

But there's one deformation mechanism that behaves in the opposite manner, and it's an important one: dislocation glide. Dislocation glide sounds like something that ought to be easy and graceful. And maybe it is, for a little while. Dislocations are lines where crystal lattices are contorted, and they're supposed to actually be easier places to break and reform bonds than is possible in a perfect crystal. And if a crystal had only one dislocation, the dislocation could glide right through from one side to the other, changing the crystal's shape ever so slightly. But crystals have lots of dislocations, and when they try to glide past one another, they get tangled up. (I keep imagining every Olympic ice skating champion for the past 30 years trying to simultaneously do a routine in a small ice rink. Crash. Tangle.) And when dislocations tangle, they get stuck, and it gets more difficult for the crystal to change shape -- the rock undergoes "work hardening."

And it strikes me that women scientists (or women in lots of fields) can experience a kind of work hardening. Valian argues that women constantly face little setbacks as a result of "gender schemas" - expectations about differences between women and men that lead people to overrate men and underrate women. For example, in academia, maybe a woman gets slightly weaker letters of recommendation, and then is hired by a slightly less prestigious institution, and then gets slightly weaker reviews of grant proposals, and gets slightly less funding, and then is less likely to be invited to collaborate on important projects, and then is not invited to participate in an NSF panel or to give invited talks, and then she's a weaker candidate for, say, the Young Scientist Medal at GSA. All those little qualitative things add up to a far weaker CV, and might result in getting delayed promotion, or receiving a lower salary than men, or not getting invited to join the National Academy of Sciences. The molehills become a mountain. But there's more to it than that. Those little things are exhausting, and it's easy to come to believe that, you know, maybe I didn't deserve tenure. Maybe I'm not that great of a teacher. Maybe my research isn't very exciting. They tangle together until the thought occurs: maybe I would make a pretty good stay-at-home mom, even though I'm happiest when I'm out in the field with a student, brainstorming alternate working hypotheses for a rock that doesn't make sense.

Dislocation glide happens under conditions of high differential stress and fairly low temperature. But with higher temperature - with just a little more energy - dislocations can "climb" - they can move out of each other's way and let the deformation continue. The work doesn't get easier with time, but it doesn't get harder, either. It reaches a steady state (which sounds really Zen, doesn't it?) as dislocation creep (which doesn't sound very Zen).

And I wonder. How much energy, exactly, is necessary to achieve the steady state of dislocation creep in the work world? And, well, will somebody figure out how to add water to the system so that pressure solution can take over? Because there are definitely times that I would prefer to dissolve away and precipitate someplace where the stress is lower.

The Sound of Mylonites

NPR has had this series, off and on, in which listeners record interesting sounds and then explain them on the air. I didn't have a recording device with me last weekend, but I literally stumbled across some of the most musical rocks I have ever heard: the Snake Range décollement.

I had never been to the Snake Range before, although it loomed much larger than its true elevation over my grad school career. The Snake Range is in easternmost Nevada, nearly on the Utah border, and is home to Great Basin National Park. And it's crossed by US 50, the "loneliest road," the road that continues west across the Basin and Range after I-70 ends. And in the 80's and early 90's, it was a case study for controversies over how continental crust stretches. It's a metamorphic core complex, a range with a core of metamorphic rocks overlain by a veneer of faulted and thinned sedimentary rocks. The boundary between the metamorphic and sedimentary rocks has been called a thrust fault, a low-angle normal fault, and an exhumed ductile-brittle transition. The metamorphic rocks are only around one-fifth their original thickness - pebbles stretched to pencils, thick beds of quartzite turned into mylonitic flagstone that is quarried into lovely slabs, thin and strong, with streaks of silver muscovite shimmering on their surfaces.

I was scouting out the area for a class field trip. I'm teaching Advanced Structural Geology for the first time, and I wanted to take students to see some classic fault and shear zone rocks. The Snake Range décollement is an amazing example of a mylonite, a rock in which the minerals have been shrunk and strung out by deformation within the crystal lattices themselves. Hard to explain to students the first time, and darn hard to identify in the field, and important to be able to recognize and interpret. And very, very cool.

The rocks were everything I had hoped. Perfectly exposed, with beautiful structures. Easy to find, easy to look at. I climbed to the ridgeline, enjoyed the view, and then headed down.

And then I heard something I hadn't expected. Not the rattle of a snake -- they don't call it the Snake Range for nothing! -- but a musical sound from below my feet. The thin slabs of quartzite knocked against one another, and each differently sized rock rang with a different tone. It was too resonant to remind me of wind chimes. It sounded, for all the world, as if I were dancing across a xylophone.

I wish I could have recorded it. I was sliding down the ductile-brittle transition. And it was singing to me.

It was delightful.

Edit: If you want to visit this site, it is described in at least two field trip guides:

Miller, E.L., Gans, P.B., and Lee, J., 1987, The Snake Range decollement, eastern Nevada, in Hill, Mason L., ed., Cordilleran section of the Geological Society of America Centennial Field Guide, p. 77-82.

and in more detail here:

Gans, P.B., and Miller, E.L., 1983, Field trip 6; Style of mid-Tertiary extension in east-central Nevada, in Gurgel, Klaus D., Geologic excursions in the Overthrust Belt and metamorphic core complexes of the Intermountain region; Guidebook, Part I: Special Studies - Utah Geological and Mineral Survey, v.59, p.107-16.