Sunday, March 30, 2008

Sunday stroll: flowers and birds

A few things are starting to flower. Last week, it was crocuses. This week, it's the teeny little irises planted in with the crocuses:



The irises, the crocuses, and the tulips (which have come up, but which haven't bloomed yet) are all drought-tolerant bulbs that I ordered from High Country Gardens down in New Mexico. (I ogle their catalog a lot, but it's taken me a long time to adjust to the rainfall and the soil here, so I order things rarely and experiment to see what survives. Meanwhile, I've got a non-lawn made of cheat grass.) As far as I know, none of the bulbs are native to this area, though these flowers are doing better than most of the stuff I've planted.

They're the only things flowering yet, unless those brown things on the tips of the Gamble oak branches were flowers. (They may have been. They were dusty, as if they had a brownish pollen on them.) The native shrubs are still working at leafing out, and the prickly pear is looking rather squashed from its burial beneath the snow.

Meanwhile, the birds were making a racket. My son had a bird-sounds book (complete with recordings), and some the birds in it are found locally. We had seen the chickadees, and robins, and we could hear both of them. (We also heard a red-winged blackbird, which surprised me - I thought they liked wetlands. I hope it didn't mistake our sewage lagoon for a wetland. Ewww.) We also pulled out my grownup bird book, and discovered that none of those birds migrates around here. (I knew that chickadees could handle winter - they overwintered in Maine - but I had always thought that robins migrated further south than Colorado. Maybe they change elevation.) So the noise may have been a sign of spring, but the birds themselves probably aren't.

I noticed that one of our local birds was missing: the hummingbird. It's probably a good thing that the native plants aren't flowering yet - the hummingbird is the most obvious local pollinator.

There's a storm blowing in, and March still ought to be winter here. I don't think it's going to snow down here, but I'm still glad that the littlest birds aren't around yet.

Saturday, March 29, 2008

Geology terms overdue for retirement?

In the last couple weeks, I've heard a number of comments about geology terms that are unnecessary or outmoded. The Cordilleran tectonicists at the Las Vegas GSA meeting kept making jokes about how they weren't supposed to use "miogeocline" (which means essentially passive margin, and which replaced "miogeosyncline" after plate tectonics became accepted). "Greywacke" also seems to be on its way out. In the geoblogosphere, Olelog asks whether we need the word euxinic. And then there's this wisecrack from Ammon Shea, who is writing a book about reading the Oxford English Dictionary:

For instance trondhjemite is defined as ‘Any leucocratic tonalite, esp. one in which the plagioclase is oligoclase’. I have my doubts as to whether anyone has ever thought to themselves ‘I wonder what trondhjemite means?’ But if someone did, and went to look it up in the OED, it seems unlikely that this definition would clear things up much.

I disagree with Shea. I know what a tonalite is, and I know what oligoclase is, but I often need reminding of the precise definition of "trondhjemite." I've got even more problems remembering the definitions of other igneous rock names ("alaskite," "pantellerite," "hawaiite," "benmoreite," etc.) but that's partly because I've worked in Precambrian rocks, and lots of Precambrian geologists talk about trondhjemites. So I think the definition in the OED is useful, but I'm not so sure that the term itself ought to remain in active use. (By the way, if Shea wants a really impenetrable geologic definition, he should see the definition of cactolith.)

So I'm curious. If you could get rid of five geologic terms as unnecessary and/or outdated jargon, which ones would you choose?

Thursday, March 27, 2008

Job-hunting suggestions

A couple soon-to-be geology graduates commented on my last post, saying that they hadn't seen any job openings for anyone with less than a year of experience. I'm going to list some things that I would do, if I were looking for a geology job. Warning: I've never had a job outside academia, and we've got alums in the mining and oil & gas industry visiting campus and recruiting - I don't know if any of these types of searches would actually work.

1) Use google to find some companies. I would try search terms like "mudlogging" (which turned up at least one company looking for workers on its first page), or "copper exploration." (Try lots of different metals, too. Look at the financial pages of your local newspaper - what metals are selling at high prices right now? Gold, copper, molybdenum, uranium...?)

2) If you find news about companies, google the company's name and see if they have any ads online. (I know Newmont and Barrick Gold are hiring, and I've heard that there are positions for molybdenum exploration - maybe with Climax? - in Colorado.)

3) Even if they don't have ads, send a resume looking for an entry-level geologist position.

4) Look in phone books for "environmental" or "geology" to find local consulting firms that may be hiring. Towns with significant resource industries (like my across-the-border neighbor: Farmington, New Mexico) are more likely to have jobs - look for places that are geology boomtowns. You won't find jobs everywhere - but you don't find gold or oil everywhere, either.

5) Tailor your resume to the company you are applying to. Don't tell mining companies that you want to work in the petroleum industry, or oil companies that you want to clean up groundwater. If you're open to lots of different industries, have lots of different resumes.

6) Keep trying, if your first few attempts don't land you a job.

7) Be flexible. You might find a job that isn't in your dream town. It might not even be on your dream continent. But if you work there for a little while, you might get valuable experience that will let you get another job, or will ground you in reality as you work through grad school. (Or you might learn that you want to go to law school. And that's a good thing to know.)

Good luck!

(And for the rest of the geology bloggers, especially those of you in industry... what would you do, if you had a B.S. or B.A. in geology, and didn't have industry connections, and wanted a job?)

Wednesday, March 26, 2008

Teaching for a new geology job market

Geotripper asks whether the sudden boom in geologist hiring is a good thing. We got into geology for the love of it; can one become a geologist just for the money?

I've got a slightly different question (but one that Geotripper alluded to at the end of his post): what would happen to our teaching if students suddenly started flocking to geology majors?

I've never seen boom days for geologists. I graduated from college in 1989. Nobody was recruiting geologists then. I went straight to grad school because I got an NSF fellowship, and it paid. The alternative, as far as I could tell, was flipping burgers. I went to job fairs in grad school, but there weren't many recruiters. My friends who did dissertations on basin analysis or copper porphyry systems had trouble finding jobs; the companies certainly weren't interested in young idealists who specialized in structures in metamorphic rocks. Most of my grad school cohort got jobs in academia or in government, or became computer geeks, or got MBAs, or disappeared from the geology radar.

I've had the fortune to teach in good undergrad departments. (My current department has more undergrad geology majors than any college in Colorado, including 20 graduates this year.) But even here, surrounded by spectacular mountains, our intro courses are mostly filled with students looking for general education science credit. I see 50 to 100 intro students a year; one or two of them go on to be geology majors. We constantly worry about our numbers of students. Will we recruit enough freshmen? Will we attract enough transfer students? How many sophomores are registered for Mineralogy?

If we suddenly had the numbers of students who want to major in something like Accounting, though, I wonder what I would do? I'm used to intro classes full of students whose interest in geology is marginal, at best. My sophomore mapping class, however, is a complete zoo when 30 students register for it. If we were flooded with sophomores, I would need to divide the class into at least two sections, which would make it more difficult to schedule everything (since I also teach Structure and Earth Systems, with labs, that semester). My goal in the mapping class is to make sure the students leave with the skills to do field work in the rest of their classes. Would I be able to give the students the individual, hands-on attention that they need? And if I had 30 students in Structure at the same time, would I be able to function? Would I be tempted to weed? (I probably wouldn't need to; students have to take chemistry, pre-calculus, and Mineralogy before they take Structure.)

Our students are being recruited right now. I know of offers comparable to the ones quoted by NPR and Bloomberg. I'm advising the seniors not to get used to high pay, and to take care of their debts and retirement planning ASAP. I wonder how I would react to freshman who were only in it for the money, though. I'm used to an entirely different market, one in which a geologist has to survive on love of the work. I might still be too much of an idealist for industry.

Tuesday, March 25, 2008

What are these dirt snake things, anyway?

Now that the snow has mostly melted, we get to look at what it has left behind. Fortunately for me, my house is off the main road and I don't have a dog, so some of the things that can make mud season so icky aren't part of my landscape.

Instead, I've got things like this:



These are ridges of loose dirt, about 5 cm wide and a few cm tall. They are just downhill from my driveway, on a 15 degree slope, but there are also some on the flatter slope of the nearby drainage. They lie across last year's grass, and across some cobbles near the side of the driveway. I've seen similar features above treeline, soon after the snow has melted, and had lots of discussions about what they are. (Critter burrows? Remnants of running water, like teeny eskers?)

Anybody know of literature on things like these? What are they?

Sunday, March 23, 2008

Sunday stroll: UFOs and alcoves

Just across the New Mexico border, near the town of Aztec, New Mexico, it is rumored that a UFO crashed on a sandstone cliff in 1948. The Aztec town library will be holding a UFO symposium next weekend, as it does every year. We headed out to the crash site - or at least to a trail near it - this weekend, so we could explore without being abducted.

We didn't see anything resembling alien spacecraft (though it's possible that the mountain bikers were in disguise). But if the aliens wanted to hide, we found some nice sapping alcoves for them.

If you look up at the cliffs of the canyon country of the American Southwest, you might see near-caves, overhanging sandstone that shades little alcoves. The Ancestral Puebloans (aka the Anasazi) made use of them to build cliff dwellings in places like Mesa Verde. There aren't any cliff dwellings in the sandstone above Aztec (although there are some other Ancestral Puebloan ruins nearby), but there are alcoves.

Alcoves are excavated by groundwater.* Water seeps into the sandstone at the surface, and then, somewhere below, it hits a less permeable layer and flows to the nearest open surface - in my part of the world, that would probably be a canyon wall. As the groundwater leaks out, it loosens the sands grains, and gradually removes rock beneath an overhang. (If the process continues, it can create arches like those in the parks to our west in Utah.)

I've seen more spectacular alcoves than those along the Aztec UFO trail - Mesa Verde, of course, but also in the Canyons of the Ancients National Monument. But I've never seen water leaking out of them before.

I don't know what caused the permeability of the rock to change. There was sandstone above, and sandstone below. But there was water trickling out of the rock - it has been a wet winter, after all - and it was carrying sand with it.

And I forgot to get out the camera, because my son thought the cave was a little scary.

We probably shouldn't have mentioned the UFO story to him.

Even though I didn't bring my camera, there are pictures of many of alcoves with ruins in them around. Here's one:



Sand Canyon, west of Cortez, Colorado. Source (with lots of other nice pictures and descriptions).

Different sandstone unit. Same hydrologic process.

* Edit: Or maybe not. See the comments for references to other explanations.

Saturday, March 22, 2008

High-pressure metamorphism before 1.7 billion years ago?

The further back in time we look, the more difficult it is to figure out how plates have moved, or whether plate tectonics was even active. The ocean basins give us less than 200 million years of history, and in long-lived continental crust, younger events can wipe out the record of older events.

And some types of evidence are quite fragile. For instance, when oceanic crust is subducted into the mantle, it moves more quickly than heat can flow into it, and is metamorphosed into distinctive rocks that form only at unusually low temperatures for their depths. These rocks, blueschists and eclogites, are convincing evidence for an old subduction zone... but they rarely survive their return trip to the surface. It doesn't make much heating to replace the unusual minerals of a blueschist with more common lower-pressure minerals.

In the 1980's, when I first learned about blueschists, there weren't any known that formed in Precambrian time. Did that mean that plate tectonics was a new phenomenon, or that the subduction-related rocks just hadn't survived more than 500 million years? In the years since then, older high-pressure rocks have been found, but they're still very, very rare. Precambrian geology is interpreted in terms of plate tectonics, for the most part, but the blueschists and eclogites aren't part of the evidence in most mountain belts.

That's been true of North America. My corner of North America is thought to have formed from collisions between lots of volcanic arcs, from around 1.8 to 1.6 billion years ago. The evidence comes mostly from metamorphosed volcanic rocks, and from Precambrian deformation. The arcs are here, but their subduction complexes are gone.

Or, at least, their subduction complexes are mostly gone.

At the Rocky Mountain/Cordilleran section Geological Society of America meeting that I was at last week, Nina Fitzgerald and Mark Colberg of Southern Utah University showed evidence of retrograded eclogites from southwestern Utah. The rocks weren't pristine, by any means, but the authors had good evidence that the rocks had been at much higher pressures. (Not extremely high pressures - the pyroxenes didn't contain as much sodium as they do in, say, the Franciscan eclogites from north of San Francisco. And they didn't find coesite or diamonds, like in the ultra-high-pressure rocks of Norway or China or the Alps.) But they were the best candidates for subduction-zone rocks I've seen described in the Precambrian of the American Southwest. And they're the oldest high-pressure rocks I've heard of (though I've been out of the HP loop for a while now).

And they were found by people at a school with no grad students, doing good field mapping and looking at thin sections.

Ref: Fitzgerald, N.E., and Colberg, M.R., 2008, Evidence for Paleoproterozoic high-pressure metamorphism and decompression melting in the Mojave-Yavapai suture zone, Beaver Dam Mountains, Utah: Geological Society of America Abstracts with Programs, v. 40, n. 1, p. 64.

Wednesday, March 19, 2008

April 2008 Geology: articles I want to read

I'm running off to Las Vegas for the Rocky Mtn/Cordilleran section GSA meeting this evening, but hopefully I'll be able to carve out time to read some of the articles that have just become available from next month's issue of Geology:

Seismic imaging of subduction zone metamorphism, by St├ęphane Rondenay, Geoffrey A. Abers, and Peter E. van Keken.

They found eclogites in seismic profiles of the Alaska and Cascadia subduction zones. I mean, yeah, they ought to be there, and we find fossil subduction zones, in part, by finding blueschists and eclogites. But there they are.

Toroidal mantle flow through the western U.S. slab window, by G. Zandt and E. Humphreys.

What's going on in the mantle under the Basin and Range, anyway? And what does it mean for the rates of extension in the northern and southern parts of Nevada?

Porphyroblast rotation versus nonrotation: Conflict resolution! by C. Fay, T.H. Bell, and B.E. Hobbs.

One wouldn't expect something as pretty as a snowball garnet to create really acrimonious debate, but it has. Do garnets rotate? Does the world (or maybe just the foliations) rotate around the garnets? Is it safe to go back to the thin sections and interpret them for shear sense?


(Source: Dr. Pierre Dezes, University of Basel)

Toasting the jelly sandwich: The effect of shear heating on lithospheric geotherms and strength, by Ebbe H. Hartz and Yuri Y. Podladchikov.

I love the jelly sandwich analogy. The upper crust is strong, the lower crust is weak, and the mantle lithosphere is strong again. In some places. There's been debate in GSA Today over the past few years, and it makes for great discussions in my Tectonics class. And now there's another source of heat to consider.

Hot arguments to cool off the plume debate, by Cornelia Class.

This one's a Research Focus article, which means that the entire thing is available online for free. Is there any data that could solve the mantle plume debate? Read the commentary and see what Class thinks. (I will... this afternoon. Maybe.)

Sunday, March 16, 2008

Sunday stroll: frozen puddles

This is actually from yesterday's exploration - today I spent picking the brain of Mineralogical Society of America lecturer Lukas Baumgartner, who will be giving a talk to the department tomorrow.

My son and I went out looking for more signs of spring. And we saw more buds and less snow than last week. But he's four, and the most interesting thing we saw was:



Frozen puddles. Most of the puddles were only half-full of water. So... how did the ice grow? I mean, it doesn't grow as big sheets in air. (As snowflakes, yes. But not as frozen tops of puddles.)

I wonder if the puddles filled through the warm day, as melting outpaced infiltration of the water, but then emptied at night, when the water had more time to soak into the soil?

It is mud season in Colorado, but it's a very different thing from New England's mud season. It doesn't take long for snow-free ground to dry out. The road is dry, except beside the snowbanks. And the muddy areas have the oddest soil texture - all lumpy and almost cracked. I don't know if it's the nature of the clay minerals in the soil here or what. (Are the clays swelling and shrinking so noticeably?)

Meanwhile, the ice on the puddles was melting fast... but not fast enough. My son broke the ice on every single one of them.

Friday, March 14, 2008

Tiara rocks

Maria at Green Gabbro nominates the Bishop Tuff as the Tiara of the Sierra Nevada, because it's so sparkly. Now, welded ash-flow tuffs are very lovely rocks, especially with all those sparkly sanidine crystals. But princesses need company. So, I give you...


(Source: Vermont Geological Survey.)

The Gassetts Schist, Tiara of the Taconian Orogeny. (Or maybe Acadian. Argon gives exhumation ages, I believe. Though there's something creepy, like Brothers Grimm or something, about exhuming princesses.) Which would make the Green Mountains the Princess of New England, unless Maine, New Hampshire, and Massachusetts want to fight about it.

Thin section:


(Source: Union College.)

Muscovite/paragonite, biotite, garnet, staurolite, kyanite, quartz, chlorite... and wait, it's got too many minerals for an AFM diagram. That's ok. If you're a princess, you get additional components, so you can have extra phases, too. Because princesses totally can do thermodynamics.

Edit: If you prefer metals in your tiara, Silver Fox reminds us that there's big money to be made in mining these days. (Dr. Lemming would probably agree, if he weren't in the field at the moment.) So you can make your own tiara, or you can make a lot of money and buy one.

Wednesday, March 12, 2008

Internships, scholarships, and workshops, oh my!

Here are various opportunities culled from my e-mail from the past few days. These start with undergrad opportunities, and then go on to opportunities open to grad students, post-docs, and faculty.

Association for Women in Science Multicultural Internship Program: summer internships in Washington, DC for women undergraduate science majors from underrepresented groups (individuals of African American, Latino/Hispanic, Native American, and Pacific Islander descent).

Summer of Applied Geophysical Experience, a Research Experience for Undergraduates program at Los Alamos National Lab, New Mexico. (A former student of mine was an intern at LANL for a year after graduation, and the experience helped him a great deal in grad school.)

Various Association for Women Geoscientists scholarships. Several chapters give their own scholarships, some for undergrads, some open to grad students. There is also the national Minority Scholarship, open to undergrads nationwide.

On the Cutting Edge workshop deadlines:

Preparing for an Academic Career in the Geosciences, for grad students and post-docs. Deadline is Friday, March 14.

Early Career Faculty, which means in the first four years of a full-time teaching position. Deadline is Friday, March 14.

Teaching Introductory Geology in the 21st Century still has ten slots open, although the deadline passed. The workshop program is starting to come together, and it's going to incorporate discussions of how to reach out to underrepresented groups and how to teach geology in an urban setting. (I'm going to this one.)

Monday, March 10, 2008

Teaching: group work and individual mastery

There's apparently an academic honesty case against a student who organized a study group on Facebook, and it inspired this rant from Bora at A Blog Around the Clock:

Thus, education, especially science education, from Kindergarden through post-doc and beyond, should be organized around collaborations, teaching people and letting them practice the networking skills and collaborative learning and action. Individuals will make mistakes and get punished by the group (sometimes as harshly as excommunication). They will learn from that experience and become more collaborative next time. The biggest sin would be selfish non-sharing of information.


Hmmmm. On the one hand, yes: students can learn a great deal from one another, more than they can learn in isolation, and it's important for scientists (and lots of other people) to learn how to collaborate. But on the other hand, groups don't seem to work socially in the way that Bora imagines that they should.

I've observed many of the same things that Bora's commenters have: some students slacking off and letting others do the work, and some students getting impatient and doing everything themselves. Some of the students don't learn whatever their supposed to be mastering - and, yes, that is a problem. The class isn't going to go out into the world as a cohesive unit - they're going to disperse, and each individual is going to need to be able to apply the skills and knowledge as a member of a new group. (Would you want a member of a mapping team who couldn't identify rocks, or couldn't tell a bedding plane from a joint?) In order to work well in a group, an individual needs to be able to do his or her part.

So: if collaboration is good at some level, but students also need to individually master material, what's a teacher to do?

The simplest answer is to let homework be collaborative, but give individual exams. But I like to give students individual feedback when they're learning, before they're tested. That goes for the social aspects of group work, as well as the understanding of the material - I want to encourage the students to work well together while they're working on an assignment. So I've got a lot of different ways to try to judge mastery and encourage students to work together well while they're collaborating.

Grade based on reasoning rather than on answers. When I started teaching Structural Geology, I had a lot of field trip assignments with a lot of short-answer questions. I found that the weaker students would follow the stronger students, and both would write the same answers. So I started making students write papers for their labs, instead. When the students had to describe the outcrops in words, and then interpret their data, they were more likely to think the questions through for themselves (while also discussing the problems with the other students). Yes, they could have turned in identical papers - but it was a small class, and they knew that would be wrong. (I repeatedly lay out the rules for acknowledging help vs writing a paper together.)

Papers are hard to grade, but there are other ways to look at students' reasoning as opposed to just the answers. Concept sketches can be good. (For an explanation, see the materials for Steve Reynolds' presentation here.) Even just questions like "what's your evidence?" can push students to put the pieces together.

Make each student responsible for a critical piece of the project. This is the way real collaborations work. The jigsaw technique is great for small projects. For bigger projects, it's worth choosing a project that requires the effort of everyone in the class.

Have the project be something they want to be proud of. It's hard to figure out some kind of carrot beyond a mere grade, but if you can find one, it can be a great motivator. My writing class is in charge of putting together the alumni newsletter for the department, and if it isn't good enough to show to the world, I don't send it out... and everyone knows that the class blew it. I've only had one inadequate newsletter - knowing about that one class is enough to push all future classes to work hard.

Evaluate individuals orally in class. I've never done this, but Eric Baer of Highline Community College in Washington suggested this to me as a way to reduce the burden of grading labs. What if I circulated around the lab room while students were working, asking individual students to explain their reasoning as they did problems, and graded them on the spot? It's an intriguing idea, though I worry that I would have trouble getting to all twenty students, especially on the last problems.

Make critiques part of individual work. My structural geology class is currently working on a project that I fondly call "the cross-section from hell." It's a fairly straightforward problem, really: they've got a map of part of the Wyoming fold-and-thrust belt, and they have to draw a cross-section down to Precambrian basement, and it has to be reasonable geometrically. Each fault has to have matching beds in the hanging wall and footwall, and each bed has to be offset the same amount (unless there is a fault-propagation fold), and faults have to meet in reasonable ways. But it's really, really hard to make it work, and the solutions depend on the choices the students make at the beginning. (Which bedding orientations are most reliable? When should they average orientations, and when should they split them into two groups? What the heck is going on with that overturned fold, and why doesn't it follow John Suppe's rules for fault-propagation folds?)

After they've worked for a week, I have them exchange cross-sections with a classmate and look for things that don't work. They learn from one another, but they can't really cheat, because I grade each cross-section on whether it works, not on whether it matches my key. (I guess a student could go to the light table in the department office and trace a cross-section made by a student during a previous year, but that would take a lot of nerve to do under the eyes of all the faculty members!)

What about the rest of you? Do you have ideas that I haven't thought of?

Sunday, March 9, 2008

Sunday stroll: looking for signs of spring

I'm not from around here. The plants and animals still are unfamiliar, even after seven years. And I don't have a good sense of "normal" for weather. Spring comes both early and late: it's so warm on sunny March days, but when a storm blows through, we can get a foot of snow.

I've got a preschool-aged child, though, and I want him to grow up aware of the world around him. Last spring we started exploring outside, watching lizards do push-ups and admiring horned lizards and trying to sneak up on jack rabbits. Lately, though, our outdoor activities have consisted of shoveling snow, and shoveling more snow, and shoveling slush. We tried following animal tracks after the first storm, but we haven't done much lately.

I was inspired to go out and start looking at the plants by a post from John Fleck, who wrote about observations of early-blooming flowers in the Swiss Alps in 2007. It turns out that there's a network of US citizens making the same kinds of observations: Project Budburst.

Aha!, I thought. What a great way to introduce the kid to science and nature!

Well, maybe. The problem is... well, I mentioned the problem at the beginning of this post. I don't know my local plants*. I've got a field guide to local plants (Shrubs and Trees of the Southwest Uplands), but there are so many little ecological niches out here. Elevation matters. So does aspect. So does the type of rock and soil. So does the history of past climates. Put it all together, and you've got a lot of species that are peculiar to certain places. My field guide's pictures are hand-sketched, not color photographs, and they're organized by ecosystem, but my area is on the border between the pinyon-juniper and Ponderosa forests. Oh, and there are three distinct types of leaves on the various shrubs, but there seem to be several different species with similar leaves.

So my son and I went out looking for plants beginning to leaf out. I'm not sure which species we were looking at, but maybe someone reading can help me identify them.

There are only two plants starting to leaf out right now. The first one has fuzzy alder-like leaves about half the size of my thumbnail:


This particular shrub is low to the ground, but I think this is one that we cut back last year. (Anything near the house and underneath a pinyon gets cut back, in hopes that we can reduce the fire danger.) It may be Cercocarpus montanus (alderleaf mountain-mahogany), but I'm not sure. I've found some pictures on the web that have sharper teeth.

The other plant that's beginning to leaf out looks like this:



The leaves are fuzzy, thick, and greyish-green, though many of the new leaves are reddish. This is mostly a low plant, and it's really tough - it's the only thing that survived my attempt to transplant shrubs to the cleared ground where our cistern was put in last year. I think this one will have tiny yellow flowers sometime this spring. Right now, it's leafing out in places where the snow has melted all the way to its roots, but it's still brown wherever the snow is still deep. Maybe this is Purshia tridentata, antelopebrush?

There aren't any examples of the third type of leaf, a long, skinny leaf. I think it may be false mock-orange, Fendlera rupicola. But there are at least two different plants with white flowers (one has four petals and one has five) that I noticed last spring. I'm not sure what the second one is.

And then there are different plants that grow on the north-facing slopes. One, at least, has alder-like leaves, but softer, thinner, darker green than the leaves of the similar-looking plants on the sunnier side of the hill.

I don't think that one's going to be leafing out very soon, though. It's buried under this:



Not-quite-five-year-old kangaroo for scale.

* This isn't entirely true. I know pinyon, juniper, Gambel oak, prickly pear, and yucca (though I don't know which variety of yucca it is). I just don't know most of the flowering shrubs. Until last year, I thought there were only two or three types, but when I started looking at the flowers, I realized there were more. So now I'm going to start paying attention.

Thursday, March 6, 2008

Misleading headline of the day: sea level is falling!

Headline from National Geographic: Sea Levels to Plunge Long Term, Study of Dino Era Says.

It paints a scary view of the Cretaceous: forget T. Rex. Did you know that sea levels were 560 feet higher than they are now? That would make the tip of the Washington Monument barely above sea level! (And, for that matter, the high points of Florida, Delaware, and Louisiana would be only accessible by scuba diving!) That's right... and it's all natural - it's due to the sea floor pulling apart!

Umm. Actually, I did know that. In fact, where I live, at 6500 feet above sea level, I can go see the shoreline of the Cretaceous Interior Seaway that flooded North America. The high sea levels of the Cretaceous are hardly big news to geologists, and the role of mid-ocean ridges in controlling global sea levels was accepted by the 1980's, at least.

The story is about an article coming out in Science tomorrow. Science is supposed to published ground-breaking, cutting-edge research. They wouldn't publish something that's been accepted for decades, would they?

Of course they wouldn't.

The paper discussed by National Geographic (Muller, R.D., Sdrolias, M., Gaina, C., Steinberger, B., Heine, C. (2008). Long-Term Sea-Level Fluctuations Driven by Ocean Basin Dynamics. Science, 319(5868), 1357-1362. DOI: 10.1126/science.1151540) deals with a far more subtle question. We know sea level was high during the Cretaceous, but how high was it, exactly? Different methods of estimation give different answers. Estimations of mid-ocean ridge volume gave numbers in the neighborhood of 250 meters (820 feet - above the high point of Rhode Island). Sedimentary rocks in New Jersey, on the other hand, imply that the highest Cretaceous sea level was only 40 meters (131 feet) - less than the sea level rise that would occur if we melted all the ice on the planet. Why the discrepancy?

Muller and colleagues started by assuming the sea level rise was mostly the result of tectonics. The young rocks at mid-ocean ridges ride higher than the old, cold rocks of the abyssal plains, so the first thing they had to do was figure out just how old the ocean floor was in the Cretaceous. That's not that easy, because several oceanic plates in the present-day Pacific have gone down subduction zones and disappeared. Then the authors had to account for hot spots (like Hawaii), and for sediments, and for changes in the area of oceans versus continents (such as that caused by the widening of Nevada during formation of the Basin and Range). And finally, yes, they calculated how much sea level would rise if our ice caps all melted.

They conclude that Cretaceous sea levels were 170 meters (~560 feet) above present-day sea level.

So why do the sedimentary rocks from New Jersey give such a different answer?

They blame the mantle. Actually, they blame the Farallon plate - the oceanic plate that subducted beneath North America during the Mesozoic (and whose remnants are still sliding under the Pacific Northwest, Central America, and South America). The old Farallon slab is still down there, sinking... and apparently it is dragging New Jersey (and presumably the rest of the East Coast of the US) down with it.

I'm not sure how to evaluate the explanation for New Jersey's low elevation. If it's correct, it implies that the mantle drives major changes in relative sea level. Now, heat in the mantle is blamed for the high elevations in rift zones (such as the East African Rift), but I hadn't heard of ancient subducting plates dragging their overriding continents down. (Is there a similar effect in eastern South America? Is northern Asia affected by subduction of the Indian plate?)

Whether their explanation for New Jersey is correct or not, however, the National Geographic article completely misses the point. Yes, I know that "Discrepancy Resolved Between Cretaceous Sea Level Estimates" doesn't have the same ring. But the Science article does not say anything about future drops in sea level. It certainly doesn't try to extrapolate the trend 80 million years into the future, as the National Geographic article does:

When this trend is extrapolated out 80 million years from now, it suggests that even if all of today's ice caps were to melt, sea levels would be 230 feet (70 meters) lower than they are today.

This sounds like the advice of a bad stock analyst in the 90's: if it's going up now; it will always go up. And if it's going down now, it... will continuing decreasing forever.

My advice: if you are hoping for subduction of mid-ocean ridges to save your city from flooding due to global warming, don't hold your breath. Even if tectonics causes global sea levels to fall, the ocean floor isn't going to change very fast.

Edit: Reuters has an equally misleading headline. It sounds from the news release like the authors of the paper are claiming that the paper predicts the future. Hmmm. I guess it's possible to predict the future subduction of the East Pacific Rise and the Gorda/Juan de Fuca/Explorer Ridges. But is it possible to predict future hot spots/large igneous provinces, especially given that there's a debate about their origin? And do we know exactly why the Pacific plate appeared at the triple junction between three other oceanic plates? (Is it the result of some kind of triple-junction instability?)

Meanwhile, Ole has a good discussion of long-term versus short-term sea level changes. I can't comment on his site (it requires registration), so I'll say here: read it. It's a good discussion.

Wednesday, March 5, 2008

Aspect is important

This is the view west from campus today:



That long ridge is made up of the Mancos Shale, and the cliff above it is the Point Lookout Sandstone of the Mesa Verde Group.

But I'm not posting this for the stratigraphy. The Mancos Shale is eroded into lots of steep gullies, and on each one, the south-facing slope is bare, and the north-facing slope is snow-covered.

It's all about the aspect, at this time of year.

My field trip spots all face south.

Tuesday, March 4, 2008

That geologic death wish...

So Chris Rowan wants to hear stories about hazardous field work, huh?

I've been afraid of heights, or at least of exposure, since I was ten. I've learned to manage it (mostly; my former field partners may disagree), because sometimes the interesting rocks are hard to get to.

I'm not particularly afraid of water, though. I grew up in New England, I worked as a lifeguard, and I've waded across countless streams with my boots tied to my pack. This past summer, however, I decided that maybe I need to re-think my cavalier attitude towards liquid hazards.

This is where I'm working these days:



Unfortunately, to get to part of our field area last summer, we had to cross this:



That's a small river in the wilderness. No bridges across it. And in June, there was still snow melting in the high country. We tried to wade the river, but it was up to our mid-thighs before we got six feet into the current. It didn't seem very safe, especially with backpacking equipment.

So we left, and came back the next day with this:



I've done a lot of flat water canoing, but I don't have much experience with strong currents. My dad, however, had, so he tried to teach me.

If you look closely at that photo, you'll see the result: we broke a paddle.

We ended up doing some reconnaissance work on a low-elevation (by my current standards) shear zone, and went back to this area in late July.

(Maybe later I'll tell Alaska stories.)

Monday, March 3, 2008

Continuous GPS monitoring: do you know where you're going?

Honestly, I meant to answer Silver Fox's question about GPS monitoring of deformation across the Basin & Range.* But I got distracted by another commenter, who pointed me to the EarthScope GPS site.

Some background: this isn't the handheld GPS unit that you can use while hiking, and which is good for locating an outcrop (or, in my case, my Subaru). These are high-precision units, and they measure changes in location well enough to monitor plate motions. That alone impresses me - it's confirmation of a theory that we accepted based on very indirect evidence. But GPS can do more - it can measure the quiet deformation that follows a major earthquake**, or swelling of a volcano that's about to erupt, or the deformation that occurs within a continent. That means that it (along with other techniques for measuring active deformation) has the potential to test ideas about the behavior of plates, on their boundaries and within their not-always-rigid interiors.

There's a big geophysics experiment going on right now in North America: the EarthScope program. Among other things, it has set up an array of continuous GPS receivers across the US.

And you can look at the results on Google Earth. (Click on images to see a larger version.)



Each red arrow represents the velocity of an individual GPS station. The longer the arrow, the faster it's moving. The Bay Area, for instance, is moving northwest at about 50 mm/year. Sacramento, on the other hand, is moving more slowly, and more toward the west.

But it gets better. You can also look at the 3D velocities:



Red Mountain Pass, not too far north of me, appears to be sinking, as well as moving toward the west. Not very fast - maybe 5 mm/year, with an error of about half that. (There are error ellipses that you can turn off and on in Google Earth.)

Mt. St. Helens is also dropping (as one might expect, given that the magma's coming out right now):



It looks like Mt. St. Helens is spreading a little, too - the north side is moving north, and the south side is moving south.

And yes, to go back to the previous question, there is a GPS station just south of Wells, Nevada.



Wells is moving west and a little up. The adjacent sites had very similar motion.

Now, this doesn't show changes in rate before and after the earthquake. That, presumably, would require more analysis of the data. And then it would take modeling to figure out whether the fault behaved as one might expect for a normal fault in eastern Nevada.

So no great insights about the Wells earthquake. But I know where I'm going now.

(The .kmz files are available from UNAVCO, if you are interested in exploring for yourself.)

*Thatcher et al., 1999, Science, DOI: 10.1126/science.283.5408.1714.

**Subarya et al., 2006, Nature, doi:10.1038.