Friday, May 23, 2008

I wanna be a Science Scout!

I just found this website (part of the Science Creative Quarterly), and I had to get my own "flair". (Never was in the Scouts, but I was always a little jealous of the cool badges.) Apparently some of the folks up at the University of British Columbia have a lot of time on their hands. Or maybe it's just a Canadian thing.

Look! They have one that was definitely designed for me.

The “active volcano is my research locale” badge.More exotic than the usual laboratory bench. (R)

This one's pretty self explanatory...



And some others...

The “talking science” badge. Required for all members. Assumes the recipient conducts himself/herself in such a manner as to talk science whenever he/she gets the chance. Not easily fazed by looks of disinterest from friends or the act of “zoning out” by well intentioned loved ones. (DN)

Zoning out just means that they're not conscious enough to run away, so you've been successful in capturing their attention.

The “I blog about science” badge. In which the recipient maintains a blog where at least a quarter of the material is about science. Suffice to say, this does not include scientology.

Snarking about bad science counts as science, right?



The “inappropriate nocturnal use of lab equipment in the name of alternative science experimentation / communication” badge.In which the recipient has “borrowed” scientific supplies for the sake of stealth scientific communication. (JG)

What, like you've never used the big sledgehammer on a can of Natty Lite just to see what would happen?

The “I may look like a scientist but I’m actually also a ninja” badge. Lethal when in combination with the “destroyer of quackery” badge. (AC)

I took a year and a half of judo and a semester of high ropes training. And I have a black facemask and a sword lying around somewhere...

The “totally digs highly exothermic reactions” badge.Might be best to keep an eye on such recipients. (JM)

If a volcanic eruption doesn't count as an exothermic reaction, I don't know what does.



The “works with acids” badge.
In which the recipient has worked with acids. (L)

Oh, the joys of HF. Or rather, the total paranoia caused by working with a liquid that etches bone and causes internal acid burns.


The “I didn’t bathe at all for an entire month, because of science” badge. Ah the joys of field work… (SW)

It was only two weeks, okay? And the smell really wasn't noticeable after the first week, anyway.


The “has done science whilst under the influence” badge.
This can apply to both achieving moments of intellectual clarity or actual performance of an experiment whilst under the influence. It presumes talking about science under the influence a given. (JD)

This is practically a job requirement for geologists, right?

Thursday, May 22, 2008

Hat? Check. Leather Jacket? Check. Whip? Hm...

Nah, don't actually have the whip. But I do have the hat and the jacket and a minor in anthropology.

It's about darn time.

Tuesday, May 20, 2008

Accretionary Wedge #9: Cenozoic magmatism and the subduction of the Farallon slab

My significant geological event is a pretty long one - actually, something like 40 million years long, and probably still ongoing somewhere down in the mantle. The subduction of the Farallon plate actually means a great deal to me, because without it, my senior thesis research would never have happened. (Okay, probably a lot of other things, including me being born, wouldn't have happened, but my research is pretty dependent on it.) Callan talked about the accretionary wedge that formed during the subduction, and how it parallels orogenic activity on the East coast of the US, but I wanted to concentrate on the intraplate effects of Farallon subduction. (And hopefully I won't screw any of this up - it's been a while since I wrote this part of my thesis.)

(Image from Wannamaker et al., 2003, using seismic tomography to illustrate the current position of the Farallon slab.)

During the Laramide Orogeny, which started between 70 and 80 million years ago, there was a great deal of intraplate magmatism and volcanism in the Western United States. Igneous activity in eastern California, Nevada, and western Utah moved southward along a generally east-west trending front, and magmatic processes were characterized by both extensive calk-alkaline (does anyone still use that term?) and bimodal volcanism, and widespread plutonism beneath south-central and southwestern Utah. After ~20 Ma, the bimodal stuff transitioned to mainly basaltic volcanism resulting from Basin-and-Range extension. The assumption here is that everything before the basaltic volcanism was a result of the subduction of the Farallon plate, and that the patterns of those volcanic rocks reflect the geometry of the subducting plate.

But the interesting thing about Farallon subduction is that, at the end of the Laramide orogeny (35 to 55 Ma), there was a distinct lack of volcanism over the Farallon plate - even though it was still being subducted (and still is today, somewhere down in the mantle) . Simply put, it "skipped" a large area, mostly under Nevada and part of Utah, and then started up again ~40 Ma (sometimes called the "Mid-Tertiary Ignimbrite Flare-up").

(Figure from Lipman et al., 1972, of the "skip", or lack of magmatic activity after ~40 Ma.)

Several models have been suggested to explain this "skip", and they involve changes in the way the plate was subducting. My background research mostly pulled up ideas focused on the "flat-slab" subduction style, where the Farallon plate is thought to have switched from a steep dive (~30 degrees) into the mantle to a shallow, nearly-horizontal (~5 degrees) movement against the lithosphere. This would effectively shut off the magmatic source for volcanism, accounting for the "skip". A resurgence in this magmatism resulted from more changes in the subduction geometry; in one model, the downgoing Farallon plate began to steepen again at ~40 Ma, allowing for more decompression melting and magmatism under the western United States; and in another model, only part of the plate steepens (like ripping a part of a sheet of paper in half, keeping one half horizontal and pulling the other down). This model suggested that the "rip" or warp in the plate propagated south as the plate subducted, which accounts for the patterns of volcanic deposits produced during this interval (moving south and west-to-east at the same time). The second idea also explains the lack of volcanism south of the igneous “front” by having the steeply-dipping portion of the downgoing plate on the north side of the front, and the gently-dipping plate to the south. Since the steep subduction would result in hydration and melting of the mantle wedge and the shallow subduction would not, volcanism would be concentrated above the steeper portion of the Farallon plate.

(A "cartoon" of a proposed evolution of the Farallon slab in the upper mantle by Schmid et al., 2002.)

There are, of course, other ideas on Farallon subduction (including one about how a "rift pillow" of hot material built up during the Laramide may be responsible for Basin-and-Range faulting, and another that suggests remnants of the Farallon plate are responsible for driving local mantle flow under the New Madrid Seismic Zone and could be a driving mechanism for seismicity there), and other explanations for why there was so much volcanic activity in an intraplate setting, but I tend to favor the slab-geometry ones - at least for the moment.

Why is all this significant to me? Without the Farallon subduction, the particular patterns of volcanism that produced the High Plateaus of Utah (and associated igneous provinces like the Marysvale Volcanic Field) would not have happened. No High Plateaus = no thesis for Tuff Cookie. It's also particularly important to me because it ties the geology of a relatively small area into processes that operated over millions of years and across a good chunk of the continent - the kind of comprehensive understanding that's very difficult to wrap your mind around. When I first visited the High Plateaus as part of my first real field course, I didn't know a thing about magmatism and tectonics in the Western US. I picked up a little on that trip, but it wasn't until I returned several years later for my thesis research that I had a chance to really dig (sometimes literally) into the geologic history of the area - and understand it.

I had a moment somewhere in the panic of thesis-writing where it all clicked together, and I could draw connections I'd never considered before. It certainly wasn't on the scale of an epiphany, but it was exciting - and why else would anyone do geology? It's one of the reasons that I like to describe geology as puzzle-solving, because at some point in a project I always have one of those "ah-ha" moments where the pieces finally fit together.

Going back and reviewing all that research again is also very enlightening; I'm able to see where my thesis can be improved, and what I can do better when I'm writing on the subject in the future. Learning about the subduction of the Farallon plate not only gave me valuable material for my thesis, it forced me to think on very grand scale - to realize that the repercussions of a single event could last millions of years and have an impact on nearly the entire continent (if you include the New Madrid research). I find it fascinating, and amazing, and just pretty darn cool.

References:

Forte, A. M., J. X. Mitrovica, R. Moucha, N. A. Simmons, and S. P. Grand (2007), Descent of the ancient Farallon slab drives localized mantle flow below the New Madrid seismic zone, Geophys. Res. Lett., 34, L04308, doi:10.1029/2006GL027895.

Lipman, P.W. et al., 1972, Cenozoic Volcanism and Plate-Tectonic Evolution of the Western United States: Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences, v. 271, no. 1213, p. 217-248.

Schmid, C. et al., 2002, Fate of the Cenozoic Farallon slab from a comparison of kinematic thermal modeling with tomographic images: Earth and Planetary Science Letters, v. 204, p. 17-32.

Stewart, J.H. et al., 1977, East-west patterns of Cenozoic igneous rocks, aeromagnetic anomalies, and mineral deposits, Nevada and Utah: Geological Society of America Bulletin, v. 88, p. 67-77.

Wannamaker, P.E. et al., 2001, Great Basin-Colorado Plateau Transition in Central Utah: An Interface Between Active Extension and Stable Interior: Utah Geological Association Publication 30 – Pacific Section American Association of Petroleum Geologists Publication GB78, 38 p.

Other resources:

USGS diagram of the Farallon plate subduction from 30 Ma to present

Wikipedia article on the Farallon plate

A NASA Scientific Visualization Studio animation of the subduction

One of Tanya Atwater's (UCSB) animations showing the history of the Western North American plate from 38 Ma to present.

Sunday, May 18, 2008

Thursday, May 15, 2008

Oldies but Goodies: A Report on the Geology of the High Plateaus of Utah

I feel like I've been totally lazy about posting anything substantial lately, and (probably because I was in the throes of paper writing) I missed the PodClast again. I did, however, see this post at Clastic Detritus, and I thought it might be interesting to write about some of the older books and papers on my shelves. This is one of my favorites, probably the oldest, and (unfortunately) not one that I own in book form, because it would cost me a thousand dollars. (It's also my favorite because it deals with my thesis field area, which I really miss at times like this when I'm chained to a desk.)

C. E. Dutton, 1880, Report on the Geology of the High Plateaus of Utah with Atlas, US Department of the Interior

Clarence Edward Dutton was one of the founders of seismology, and came up with the concept of isostacy; he worked for the U. S. Geological Survey from 1875 to 1891 (under John Wesley Powell), and published several books about geology in the Western United States. He was also the chief of the USGS Division of Volcanic Geology in 1887. (And hey, his 167th birthday is today!) He made geological investigations of the Grand Canyon in Colorado, the plateaus of Utah, and the 1886 Charleston earthquake.

Reading any of Dutton's works is a pleasure - not only because they are accounts of the first explorations of the geology of the western US, but because of the writing style of Dutton's time. It reads a little like a travelogue, a little like an adventure story, and is elegant, succinct and thoroughly insightful.

Some of my favorite parts of the book don't even have to do with geology. Take the first page, for instance:
"Sir: Herewith I have the honor to transmit a report of explorations and studies in Utah Territory prosecuted during the years 1875, 1876, and 1877, in connection with the survey of Maj. J.W. Powell, under the Interior Department."
How often do we get to say that we are honored to offer up a paper for publication? (I suspect by the time we get around to submitting anything, especially to an online system, we are anything but honored to have dealt with the thing.)

The book also contains a number of lovely heliotypes, which makes me respect and admire the people on these expeditions even more - you've got to be pretty damn determined to lug that kind of photography equipment over High Plateaus terrain.

The descriptions of the High Plateaus are really beautiful, and not much has changed there since Dutton's day.
"The 'Plateau Country' of the west is, I firmly believe, destined to become one of the most instructive fields of research which geologists in the future will have occasion to investigate. Of its subdivisions the District of the High Plateaus is one of the most important, and the relations of the district to the province were studied with great care."
CE Dutton is my hero! And here I thought my study area was just some obscure part of Utah that no one ever visited. Looks like it was destined for greatness long before I got there. (Now, whether it's achieved greatness is another matter...)

The most relevant part of the book for me is the Fish Lake Plateau section, where some of the commentary reads like a travel advertisement:
"Not the smallest among its attractions for the geologist is the fact that it is a most eligible summer camping-place. In the daytime, throughout July, August, and most of September, it is mild and genial, while the nights are frosty and conducive to rest. The grass is long, luxuriant, and aglow with flowers. Clumps of spruce and aspen furnish shade from the keen rays of the sun, and fuel is in abundance for camp-fires. Thus the great requisites for Western camp-life, fuel, water, and grass, are richly supplied, while neither is in such excess as to be an obstacle to progress and examination."
I'll second that. Here's a description of Fish Lake itself:
"Passing across the nearly level summit a distance of 2 miles we reach the southeastern verge of the plateau, whence we may look down upon the beautiful surface of Fish Lake. This sheet of water, about 5 1/2 miles in length and a mile and a half in breadth, is walled in by two noble palisades...No resort more beautiful than this lake can be found in Southern Utah. Its grassy banks clad with groves of spruce and aspen; the splendid vista down between its mountain walls, with the massive fronts of Mounts Marvine and Hilgard in the distance; the crystal-clear expanse of the lake itself, combine to form a scene of beauty rarely equaled in the West."
But more on the volcanic stuff, which (despite Dutton's glowing recommendations), is sometimes obscured by the luxrient grass and glowing flowers. He tries to tackle the tricky question of where all the volcanics on the Fish Lake Plateau came from - exactly what I'm working on at the moment. Here's what he has to say:
"The first inquiry which arises is, whence came all these lavas? The question is not easy to answer satisfactorily, for they were erupted far back in Tertiary time, and the changes which the country has undergone since their outpouring are very great...As for the Fish Lake table itself, it does not furnish very decisive indications of being an eruptive center."
Definitely not. While the FLP has lots of lovely grabens, glacial moraines, and cirques, one thing it doesn't have is volcanoes or vents. After spending several weeks scrambling over landslide deposits, scaling cliffs and bushwhacking through mosquito-infested woods, I can pretty much guarantee that there are no volcanoes or volcanic vents on the Plateau. Dutton later suggests that one of the mountains may be part of a string of vents, but mainly because (I think) his experience with volcanic deposits was limited to Hawaiian-style volcanism, and he couldn't conceive of any other way for such thick flows to have been emplaced. My undergrad advisor and I are working on a paper that offers an alternative explanation (ash flow tuffs all around!), which we'll hopefully have published sometime this year (so I can talk about it more).

Dutton makes very thorough descriptions of a number of the High Plateaus, and although the book doesn't seem to have any sort of concluding chapter, we've found it very useful as a primary source for our Fish Lake research. One part of the book that, sadly, we didn't have access to was the map that accompanied it. But, thanks to the wonders of Google, I managed to find a copy of it in the David Rumsey Historical Map Collection, and after spending a good two hours with the "copy-paste" function and Photoshop, I am now the proud owner of a beautiful digital file that I intend to get printed up and framed. (It's a really awesome website, by the way - you can save files from it for personal use, or you can order professional-quality reproductions.)

Fish Lake is over on the right, above the center fold, sitting in a big pink (sorry, desert rose - old joke) pool of Tertiary rocks. I certainly can't blame Dutton for not assigning any names at the time, since the area is insanely complicated (and we're still working on the stratigraphic correlations).

I won't go on singing Dutton's praises too much longer, but I will mention that in one part of the book he refers to thousands of thin sections that his group made from samples they collected. I sure wish I knew who has (or had) those, and if they still exist. I would really love to get my hands on those, if just for the satisfaction of knowing that someone other than me spent a good chunk of their life going blind by staring through a petrographic microscope.

At any rate, I highly recommend at least skimming through this book online, if only just for the pictures. Pretty much anything that came out of the western expeditions of Dutton and Powell's time is well worth the effort, and gives you a fascinating glimpse into the early days of geology.

References:

C. E. Dutton, 1880, Report on the Geology of the High Plateaus of Utah with Atlas (Google Book)

David Rumsey Historical Map Collection

Wikipedia article on Clarence Edward Dutton

Bailey et al., 2007, Geology and Landscape History of the Fish Lake Plateau, Utah Geological Association Publication 35.

Because Earth science does way more than rock

Here's a good resource for anyone who's introducing students to Earth science, trying to keep it in or add it to a curriculum, or anyone who wants to see really cool animations. It's AGI's "Why Earth Science" video, which they've recently posted on the web.



There's also an accompanying brochure available for downloading in English and Spanish versions.

Monday, May 12, 2008

At least I won't get attacked by monkeys

I just came across an article from a July 2007 Wired Magazine article about the "Best Dangerous Science Jobs". Guess what #7 is?

Volcanologist! (I love the little graphic.)

And #6 is...

Graduate student.

Yep, I'm doomed. Happily doomed, though.

Tuesday, May 6, 2008

We had an earthquake!

Okay, so 1.8 is pretty dinky - but I felt this one, darn it. Whee! My first earthquake.

Details from the Arlington Alert website:

05/06/08 14:55The USGS has confirmed a magnitude 1.8 "micro" earthquake occurred near Annandale, VA at 1:30pm. There have been no reports of damage or injuries.
OEM/LCS
05/06/08 14:31The National Earthquake Information Center, via FEMA Operations, is reporting that Northern VA has experienced rumblings equivalent to an earthquake of magnitude 2 to 3. It remains unclear if this was an actual earthquake, or due to another cause.
Arlington OEM will continue to monitor.
OEM/LCS

The USGS report:

Earthquake Details

Magnitude1.8
Date-Time
  • Tuesday, May 06, 2008 at 17:30:23 UTC
  • Tuesday, May 06, 2008 at 01:30:23 PM at epicenter
Location38.828°N, 77.234°W
Depth10 km (6.2 miles) set by location program
RegionVIRGINIA
Distances
  • 2 km (1 miles) WSW (250°) from Annandale, VA
  • 3 km (2 miles) NW (320°) from North Springfield, VA
  • 3 km (2 miles) SE (143°) from Mantua, VA
  • 6 km (4 miles) NNE (32°) from Burke, VA
  • 12 km (8 miles) WSW (242°) from Arlington, VA
  • 21 km (13 miles) WSW (244°) from Washington, DC
Location Uncertaintyhorizontal +/- 1.7 km (1.1 miles); depth fixed by location program
ParametersNST= 6, Nph= 13, Dmin=70.2 km, Rmss=0.3 sec, Gp=151°,
M-type=duration magnitude (Md), Version=1
Source
Event IDld1022071


Map showing earthquakes

Now I'm all excited. Yup, not getting any work done today.

(Actually, we thought someone was moving furniture upstairs. Or that our elevator had crashed. )


UPDATE: Oh, I feel cool. Got to do the "Did You Feel It?" report. Oh yeah.

UPDATE 2: Thanks to Ron for the email - he checked in with Callan and I right away. (Callan's got great coverage, and he managed to find the seismogram of the earthquake from the Maryland Geological Survey. And he was practically on top of the thing. Lucky!)

Monday, May 5, 2008

Oh, all right...

Because every person in the known geoblogosphere is doing this, I suppose I'll have to as well.

Voila! My thesis:
created at TagCrowd.com

Fish were a very prominent feature. (No, not mica fish. I like things that go or went boom, remember.)

Sunday, May 4, 2008

In the Humorous Vein #2

For all those of you out there who are going through the ordeal once more - and that includes grading - I salute you. (And next year, I'm going to be joining you on both fronts!)

Although it's nice that, for the first time in four years, I'm not taking a final on my birthday.

Friday, May 2, 2008

Look! I'm famous!

I was recently asked to do a short interview for the blog My Cool Job about being a geologist. Here's the post - hopefully I've done a good job of describing the job to the non-geo-blogosphere! And showing off flow banding in welded ash flow tuffs - that's one of my favorite photos.

(And yes, it uses my real name. Which you can figure out by doing a little digging anyway. I still like Tuff Cookie :)

Update: Looks like that post made it to the front Wordpress page. Woohoo! I'm really famous.