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You are browsing the archive for 2010 February.

28 February 2010

Crucifix Site 1: Sediments

On the September 2009 GSA field forum in the Owens Valley, the final stop of our first day was to check out the so-called “Crucifix Site,” along Chalk Bluff Road (north of Bishop, California, at the southern margin of the Volcanic Tableland). It’s called the “Crucifix Site” because there is a metal cross erected there: This is the site of some pre-Bishop-Tuff volcaniclastic sediments. The place is interesting on several …

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27 February 2010

Virginia water well shows seismic waves

This site, from the USGS, shows depth to the water table for a well in Virginia: You’ll notice the tidal influence on the water table (broad sine-curve-like up and down crests and troughs at ~12 hour intervals), and then a sudden perturbation which caused some wiggles almost two and a half feet of magnitude! This, presumably, is the seismic waves from the Chilean earthquake arriving — surface waves, I would …

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Frozen soil lifts off

When I was out poking around in the woods, confirming for local geophile Barbara that indeed her local geologic map wasn’t 100% accurate, I noticed this on the frozen ground: We have seen this before, in a post back on NOVA Geoblog, almost exactly a year before I took this photo. Here’s another shot from the more recent excursion, taken a foot or so over from the first one: What’s …

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26 February 2010

Piedmont rocks exposed in a creek

One of the cool things about being the local geoblogger is that people get in touch with you about local geology. Sometimes this even leads to meeting up for field trips. Here’s two quick photos from a recent (January 2010) field trip to a creek near Springfield, Virginia. My host was Barbara X, a local aficionada of Piedmont geology. She has lived in this particular neighborhood for many years, and …

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25 February 2010

Rockies course applications open

For those of you who are potential NOVA students (really, that’s pretty much anyone on the planet), I wanted to let you know that applications are now open for the July 2010 Regional Field Geology of the Northern Rockies course that I co-teach with Pete Berquist of Thomas Nelson Community College. A more detailed description is available on my website. Contact me via e-mail if you want more information or …

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Lola → ammonite

Seeing my cat in this posture: …made me think of this: Where did those hind legs go?

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24 February 2010

Snowy décollement

Earlier in the month, during the big snowstorms, my window got plastered with snow. This snow formed a vertical layer which then deformed under the influence of gravity. Looking at it through the glass, I was struck by how it could serve as a miniature analogue for the deformation typical of a mountain belt. Let’s start our discussion by taking a look at an iPhone photograph of the snow: So …

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23 February 2010

Plutonic contacts in eastern Sierras

Last September, at the location of the faulted moraine (eastern Sierra Nevada, California), I took some photos of some of the sexier plutonic contacts exposed in big boulders (erratics) of the glacial till composing the moraine. Check them out. What do you see here?

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22 February 2010

Pacaya Volcano, Guatemala

Today, some photographs from Guatemala. I know one of my geoblogopeers is down in Guatemala doing research, so I’ll be interested to hear her take on these photos. These photos all come to us courtesy of my friend Courtney, who is a librarian at M.I.T., and a fellow M.S.-graduate of the University of Maryland geology department. She shared these images with me about a year ago, and I intended to …

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21 February 2010

Transtensional quartz vein

On last May’s GSW spring field trip to Chain Bridge Flats, I saw a quartz vein: Surely, upon looking at this photograph, you will be struck by the way the vein is not the same thickness along its length, and parts of it appear to be a white line transitioning into a parallelogram, and back into a white line again. What, you make ask, gives? I think what you’re looking …

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