Tuesday, July 28, 2009

Some Cambrian rocks from the Bridger Range

My third day in Montana this summer, Lily and I took a hike in the Bridger Range, going up the west side of the range via Corbly Gulch to a cirque opposite the "usual" route up Sacagawea Peak, which starts at Fairy Lake on the east side, then goes up into Sacagawea Cirque* and south to the peak. Instead, we went up Corbly Gulch and got a whole new look at Bridger stratigraphy. First, orient yourself with this topographic map:



The Fairy Lake route brings you to the ridge crest from the upper right (northeast), wheras the Corbly Gulch route brings you to the same ridge crest from the lower left (southwest). Now take a look at some satellite imagery:



The green line at upper right is the ridge crest; Sacagawea Peak is just off-screen to the right. It will not surprise you to learn that stratigraphic contacts strike NW-SE in this area. The forested left-hand part of the screen is underlain by Mesoproterozoic LaHood Formation, a coarse-grained formation in the Belt Supergroup. Then there's a little gap of grassy area and a thin line of trees atop a light-brownish layer. This is the Cambrian Flathead Sandstone, which is chock-full of interesting sedimentary structures and trace fossils. The prominent light-colored ridge-forming layer traversing the screen from upper left towards lower right is the Cambrian Pilgrim Limestone, which shows "fossil hurricanes" in the form of limestone-chip conglomerates.

Here's some of the trace fossils in the Flathead Sandstone:
flathead_bridgers

Here's a limestone-chip conglomerate from the Pilgrim Limestone, which I interpret as a paleo-hurricane deposit: rip-up clasts from a carbonate bank tumbled and re-deposited together in a big jumble:
limestone_chip_conglomerate

We hiked up to the ridge, and peered down into Sacagawea Cirque (getting pummeled by the wind!), but didn't feel like we had sufficient time to attempt summiting Sacagawea, since I had to be back on MSU's campus for an evening session as part of "Bahama Montana" class. More on that tomorrow...

______________________________
* The following week, my Regional Field Geology students proposed to rename Sacagawea Cirque as "Death Cirque," for reasons I will explain in due course...

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Wednesday, July 1, 2009

Master Master

Hey there,

Just a quick note to say: (1) I'm in Bozeman, Montana, and (2) I successfully presented and defended my MSSE capstone research. Thanks much to John Graves and Dave Lageson for their counsel and wisdom! Now that I have two master's degrees (one in geology, one in science education), I'm going to take a few semesters off being a student.

Looking forward to the arrival of my NOVA students on Sunday!

CB

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Tuesday, June 23, 2009

A quick update

It's been busy round these parts. My apologies for the lack of posts this past week.

I leave tomorrow for Montana, and I'll have limited e-mail access while out there. I'll do my best to post when I can, but it will likely be more on the ~weekly timescale rather than ~daily.

On the agenda: (1) Bahama Montana, (2) present and defend my MSSE capstone project, and (3) lead my Regional Field Geology of the Northern Rockies class for NOVA.

More later...

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Wednesday, May 20, 2009

Massive set of concentric ribs (arrest lines)?

Concentric ribs (arrest lines)?

My MSSE advisor John Graves (previously mentioned here) went on a float down the Green River in Utah last weekend.

This appears to be a huge set of concentric ribs (a.k.a. "arrest lines") on the face of a big joint in massive quartz-rich sandstone. Bedding runs ~horizontally across the image, though not to be confused with the perfectly horizontal "bathtub ring" waterstains from the river. John says, "My best guess from the guide book is that it's Entrada Sandstone, Carmel Formation & Navajo Sandstone top to bottom." The fracture appears to have started in the middle of the cliff and propagated downward and outward. Note how the ribs "flare" out at the far edge. I guess an alternative hypothesis is that this is some weird kind of dune cross-bedding in the Navajo Sandstone: the inside of a barchan dune, perhaps? (though barchans wouldn't form in the "sand sea" situation in which the Navajo was deposited)

Anyone else want to offer another interpretation for this? I think that's what it is.

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Tuesday, May 19, 2009

NAGT field trip photos

Whew!

Sorry I haven't posted much here in the past week. I've been swamped.

The good news is that my biggest task is now off my plate (just turned in the first draft of my MSSE capstone to my advisor), and that means I've got some spare attention left for the blog.

I thought I would take the opportunity to share some images from this past weekend's NAGT (National Association of Geoscience Teachers) Eastern Section conference, held at the NOVA Loudoun campus. On Saturday, I led a version of my "Bedrock Geology of Washington, DC" trip for a group of eight conference attendees.

All these photos are from Randy Newcomer, Director of Training and Services for Complete Safety Solutions of Lititz, Pennsylvania, and are posted with his permission... and my annotations!

nagt07

nagt06

nagt03

nagt02

nagt05

nagt04

nagt01

If you're interested in seeing (most of) these rocks, join next Sunday's Walkingtown, DC tour!

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Wednesday, April 29, 2009

Ooh! Ooh!

I'm swamped -- absolutely sodden with responsibilities, of a dozen flavors. Stressed, harried, scatterbrained, and to top it all off, no time for proper blogging. But that doesn't stop me from getting excited about a new opportunity to do something cool... Even though I don't need any more credits for my MSSE degree this summer, I just found out about "Bahama Montana," an expedition into past carbonate environments of the Big Sky state, and their fossil inhabitants. Can't wait!

Eventually I'll use this credit... right?

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Wednesday, February 11, 2009

New folds in the Massanutten Sandstone

Yesterday I mentioned finding a new (to me) outcrop of the Martinsburg Formation's graded beds (turbidite sequences shed off the late-Ordovician Taconian Orogeny here on the east coast of North America). Today, I'd like to share a few images of where John Graves and I went next: up into the heart of the Massanutten Synclinorium, the Fort Valley. To remind you of the relationship between the Shenandoah and Fort Valleys, here's a Google Map I've posted before:



There, defining the ridges of Massanutten Mountain (and thereby separating the lower Shenandoah Valley from the upper Fort Valley) is the Massanutten Sandstone, a Silurian-aged quartz sandstone (in some places it's a quartz-pebble conglomerate) that is correlated to the Tuscarora Sandstone further west in the Appalachian Mountains' Valley & Ridge province.

The Massanutten can show some nice primary structures, including some of the oldest known terrestrial plant fossils (preserved as fragmentary carbon films) and cross-bedding like this:

Massa_Syn_16

With regard to the cross-bedding, note that this is "reverse" cross-bedding, which records shifts in current direction over time. At the bottom of the sample, the current was flowing from left to right, and at the middle and top of the sample, it was flowing in the opposite direction, right to left. This sample shows well the distinctive shape of cross-beds: they are tangential to the main bed at the bottom, but are often truncated on top, making them superb geopetal indicators. (They tell you whether your rock is right-side-up or up-side-down.)

I took John on a hike up the Veatch Gap trail, because I wanted to show him the awesome anticline in the Massanutten Sandstone that NOVA adjunct geology instructor Chris Khourey and I had found on a reconnaissance trip out there in May of last year. John and I took a "group shot" with the fold:

Massa_Syn_10

And here's John showing those Montanans that we do actually have some cool geology out on the east coast:

Massa_Syn_11

So, what's going on here? Well... the Valley & Ridge province of the mid-Atlantic region is defined by folded (and thrust-faulted) sedimentary strata. These folds were produced about 300 to 250 million years ago, during the Alleghenian phase of Appalachian mountain-building. The tectonic cause of this deformation is interpreted to be North America's collision with Africa, closing the Iapetus Ocean and completing the assembly of the supercontinent Pangea.

More locally, the Shenandoah Valley and Massanutten Mountain are structurally underlain by a great fold, the Massanutten Synclinorium. Synclinoria are different from mere synclines because they are more complicated: the overall synclinal shape is "decorated" with numerous smaller anticlines and synclines. It's a big trough-like shape, but wrinkles are "parasitic" on the main fold. So, even within the big "canoe" shape of the Massanutten Synclinorium, there are little bulges and wrinkles that go the opposite direction. This anticline is one of them.

At that point, having seen the anticline, we weighed whether to keep hiking or not.

We opted to press on... and I'm so glad we did. ... Twenty feet further down the trail, we saw another two anticlines!

Massa_Syn_14

At its base, this one had a small cave I could crawl into:

Massa_Syn_13

And: a short distance further we found a hiker's shelter with an apt name:

Massa_Syn_15

Ha! I love it.

More tomorrow, when I'll revisit the issue of plumose structure and hackle fringes.

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Tuesday, February 10, 2009

Congratulations, Rob!

I'd like to congratulate my friend and fellow MSSE candidate Rob Greenberg for being awarded this year's Outstanding Earth Science Teacher award for the state of North Carolina. (Link goes to GSA website where winners are listed; I read about it yesterday in this month's issue of GSA Today.)

Rob's one of the most enthusiastic people I know, and a gifted educator. He loves geology, astronomy, climate, and is a strong environmental advocate to boot! If you have ten years to spare, you can check out the wealth of materials he has online at his instructional website.

Congratulations, Rob!

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New outcrops in the Massanutten Synclinorium

Yesterday, I mentioned what my MSSE advisor John Graves and I saw along the Billy Goat Trail on Saturday afternoon. Today, I'd like to share some images and insights from our Sunday field trip, out to the Shenandoah Valley and the Massanutten Synclinorium which underlies it.

I would like to thank Rick Diecchio of George Mason University for sharing some key outcrop knowledge with me. I've found that information about good outcrops can be very difficult to obtain unless you know somebody who knows. The information is primarily passed on through the oral tradition, rather than written in sufficient detail in peer-reviewed literature or in field guides (...or posted on geoblogs?).

Anyhow, back in December, on our drive down to the Blue Ridge / Valley & Ridge Symposium in Charlottesville, I told Rick I was organizing a new Massanutten Synclinorium field course. It's a place he's very familar with. He recommended a good outcrop to see the turbidite sequences of the Martinsburg Formation, a late Ordovician clastic unit made of debris shed off the rising Taconian Mountains to the east. Rick drew me a map in my field notebook, and on Sunday I was finally able to schedule a visit. Since John is unfamiliar with the stratigraphy and structure of the Shenandoah Valley (or the east coast in general), we also stopped at a lot of the other stops I'll be taking students to, including the classic "Tumbling Run" section.

Today I'd like to share a sets of photos with you from this new (to me) outcrop of the Martinsburg Formation. Tomorrow I will share another set from the next layer up in the stratigraphic stack, the Massanutten Sandstone. Both outcrops a pleasing combination of sedimentary stratification and structural geology.

Here's the Martinsburg Formation outcrop, just west of the Shenandoah River's North Fork:
Massa_Syn_09

This, like the "Pet Store Anticline" that I have previously blogged about, is an excellent place to look at bedding/cleavage relationships. The beds are dipping east, but the cleavage dips steeply to the west, implying the outcrop's position within a much larger (kilometers-wide) cleavage fan.

Here's a eye-catching outcrop that shows the beds weathered out differentially, while pervasively cut by ~vertical metamorphic cleavage:
Massa_Syn_01

More beds, of alternating sand and mud, steeply dipping in the Massanutten Synclinorium:
Massa_Syn_06
Note how the muddier portions show cleavage development better than the sandier strata.

More pervasively-cleaved muddy layers:
Massa_Syn_07

Here's one that confused me. In this predominantly-sandstone layer, you can see that the cleavage is better developed on the right, lower side of the bed. Does this mean that the right, lower-side of the bed is more mud-rich? (and sand-poor?) It did appear to be finer grained. If so, does this imply this bed is upside-down? Ordinarily, I would have thought to only look for the primary sedimentary structure as a geopetal (right-side-up) indicator, but this is the first time it has occurred to me that structural susceptibility based on mineralogy (in this case, susceptibility to cleavage development) could be used as an indicator of younging direction. I should note that this particular photo was taken downhill of the main outcrop, and may well be overturned. It's a synclinorium, after all, not a smooth syncline!
Massa_Syn_03

In this photo, the turbidite sequences of the Martinsburg Formation show a cool feature, a primary sedimentary structure known as cross-bedding:
Massa_Syn_05B
Note that this photo is taken with the photo's long axis ~parallel to bedding, but the reality of the outcrop is that this is all steeply dipping, rotated 90 degrees clockwise (see the inset for "true" outcrop orientation).

...But wait! There's stuff dipping to the left, and stuff dipping to the right! Which one is this purported cross-bedding? Try this labelled version to sort it all out:
Massa_Syn_05A
Note how at the bottom, the cross-beds curve tangentially to subparallelism with the main bed. They are truncated at top by the overlying layers. This is a good geopetal indicator, and the photo is oriented in depositional position, with the top at the top. Furthermore, if you reconstruct the current direction from these cross-beds (after the strata have been "unfolded" and restored to their original horizontal orientation, it would have come from the east... that is, from the orogen itself (the roots of which are exposed along the Billy Goat Trail.)

The intersection of rock weaknesses along the planes of bedding and planes of cleavage can result in the rock fracturing into long pencil-like bits, a phenomenon known as "pencil cleavage." This is my Freddy Krueger impersonation using the Martinsburg's cleaved "pencils."
Massa_Syn_02

John puts his hand up to give a sense of scale to the axis of this small fold in the steeply-dipping strata:
Massa_Syn_08

I was all agog over this outcrop, really digging the relationship between the structure and sedimentological elements in the rock. Best of all, it's a very short drive from Tumbling Run, and will replace the hike to the Buzzard Rock outcrop in my Massanutten field trip in April. (For NOVA-area readers, there are still four spaces open in that class...)

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Monday, February 9, 2009

Quartz & fractures on the Billy Goat Trail

This weekend, my MSSE advisor John Graves was in town, and I took him out to a couple of field locations that I bring geology students to. We started off on Saturday afternoon on the Billy Goat Trail, where I went through the usual rigamarole, what with the Iapetus Ocean, Taconian Orogeny, migmatites, and what-not.

We also saw some cool fractures involving quartz, in two different situations, each instructive in its own way.

First, here at the base of the legendary "Traverse," is some metagraywacke that has fractured. Quartz-rich fluids flowed along these fractures, and the quartz they precipitated (presumably in interstitial spaces between grains?) made that particular zone on either side of the fracture more resistant to weathering than the non-quartz-infused metagraywacke. This "fortifying" effect falls off with increased distance from the fracture. Note that you can actually see the crack in each of these high-relief ridges; it's not a quartz vein per se, but a separate, related phenomenon. Penny for scale in both photos below -- one zoomed out, one zoomed in...

BGT_1

BGT_3

Second, check out these photos, of a spot near the downstream end of the Billy Goat Trail, where usually I don't have time to take students. The bedrock here is a migmatitic schist/gneiss. Here, you'll see ~vertical foliation cut by a ~horizontal quartz vein. Once again, a penny is for scale (this time held in place with some chewing gum, as the outcrop surface is vertical, striking at a right angle to foliation). These two structures are both representative of the same stress regime. With a dominant (tectonically-induced) stress directed ~horizontally, the various minerals in the original rock rotated (or grew) into new positions perpendicular to that stress (e.g., ~vertical). But that wasn't quite enough to accomodate the ~horizontal shortening. Some additional strain was accomodated by ~vertical extension through fracturing. That fracture was infilled with hydrothermal fluids that precipitated "milky" quartz, at almost a perfect right angle to the foliation:

BGT_2

BGT_4

John was suitably impressed, and we both appreciated the afternoon hike in EXCELLENT weather (55 degrees F; gorgeous!).

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Tuesday, January 20, 2009

The cold lab, and avalanches

Ed Adam's "cold lab" (which I toured this past summer as part of my "Examining Life in Extreme Environments" class at Montana State University) gets mention in an article in today's New York Times. They also profile some of Adams' experiments setting off avalanches at Bridger Bowl, in the Bridger Range north of Bozeman. Worth a read. Some cool photos, too.

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Friday, December 19, 2008

Geolutions for 2009

Christie asks: What are your top ten geological resolutions for the new year?


For me, the list would include:
  1. visiting the Galapagos Islands
  2. visiting the high Andes (Cotopaxi, Chimborazo), Ecuador
  3. finding a cool outcrop of graded beds in the Martinsburg Formation (late Ordovician turbidites in the Shenandoah Valley of Virginia) that Rick Diecchio told me about last week
  4. "walking on the Moho" in Gros Morne National Park, Newfoundland (late summer)
  5. seeing Snowball rocks and Ediacarans on the Avalon Peninsula, Newfoundland (late summer)
  6. visiting Egg Mountain paleontological site, Montana
  7. joining my colleague Ken Rasmussen's field trip to the Culpeper Basin, a Triassic rift valley in northern Virginia
  8. some cool trip next winter break (2009-10): perhaps Patagonia? Or Antarctica?
I've also got some big teaching resolutions:
  1. Running a successful and robust Structural Geology course for George Mason University (spring semester).
  2. Running a successful and innovation Environmental Geology course for NOVA (spring semester).
  3. Running a successful and safe Regional Field Geology of the Northern Rocky Mountains course for NOVA (summer semester).
  4. Preparing and running a successful and groundbreaking Honors Historical Geology course linked with English Literature 242 at NOVA, where the English professor and I will bridge the two subjects with readings of Lyell, Darwin, "A Pair of Blue Eyes," and others (fall semester).

On other topics:

  1. Finish my M.S.S.E. degree (July)
  2. Buy a house
  3. Put together a series of geology 'vodcasts' on local geology
  4. Write a few freelance articles
  5. Publish one cartoon per month in EARTH
  6. Prepping (cutting and polishing) a backlog of rock samples from all over the place
  7. Successfully moving the geology department into our new building

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Dino Dads

Frankie Jackson, one of the professors who orchestrated my "Dinosaur Paleontology of the Hell Creek Formation" course this summer, was quoted in today's Washington Post about a study she and colleagues have published in Science today. The study suggests that male theropod dinosaurs played a significant role in incubating eggs and tending to young.

Science news note.
Science article (DOI: 10.1126/science.1163245)

Update 12/20/08: NPR did a story on this, too.

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Monday, December 15, 2008

Bearpaw ammonite

Here's a fossil that I have hanging around my house; it's an ammonite from the Bearpaw Shale (late Cretaceous) of eastern Montana. I collected it just south of Glendive, Montana, this summer on the "Dinosaur Paleontology of the Hell Creek Formation" class I took through the MSSE program at Montana State University.

Overall, this little fellow has a maximum diameter about the same size as a quarter:
DSCN1075

On the back side, where the nacre has been broken off, you can see the suture patterns:
DSCN1078

Clearly, these are ammonitic sutures (as opposed to ceratitic or goniatitic), but I haven't identified it to genus level. Any paleontologists out there able to help me out with an ID?

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Thursday, December 11, 2008

Atop Mauna Kea

What's the tallest mountain on Earth?

Everest, right? Well, yeah: if you're measuring from sea level. If you're measuring from the top of the crust the mountain rises from though, it's Mauna Kea, Hawai'i. It's about ~13,800 feet above sea level, but it rises ~33,500 feet from the oceanic crust to the peak (that's compared to Everest's mere ~29,000 feet from base to peak. So... you could say that Mauna Kea is the tallest mountain on our planet... (you could!)

On Thanksgiving day, my friend Lily and I took a drive up to the top of Mauna Kea, and did a little hike up there at high elevation. Today, I'd like to share some photographs of that excursion. We saw some pretty cool geology.

On the drive up the mountain, we saw an animal which was apropos, considering the day:
mauna_kea_C_06
Gobble, gobble, gobble. Watch out turkeys, we'll be back after we work up an appetite...

Here's Lily's jeep in the "saddle" between Mauna Kea and Mauna Loa, looking north (with Mauna Kea in the background and basaltic lava flows from Mauna Loa in the foreground):
mauna_kea_02

Some cider cones (the Hawai'ian word for cinder cone is pu'u) in the saddle:
mauna_kea_03

Turning the other way (looking south), you can see the bulky form of "the long mountain," Mauna Loa. What a classic shield volcano shape! I love the fact that it's so dang wide it makes a lousy photograph. You just can't capture its spread-out bulk in a photo; it's too massive:
mauna_kea_01

This was the spot where I pretended to have my toes overrun by a pahoehoe flow:
hawaii_rocks_12

As we drove up the road to the top of the mountain, I was amazed at the raw volcanic landscape, decorated with cinder cones like this one:
mauna_kea_06

At one point, we passed a neat little angular unconformity on the roadside. Here it is, with a nickel (white dot left of center) for scale:
mauna_kea_04

Here's a closer-shot of this small angular unconformity. Earlier layers of ash and lapilli were deposited at a steep angle, and then eroded (perhaps by glaciation? pure speculation there) before more ash and lapilli were deposited atop it, at a lower angle. There's not likely to be much time missing here, and so perhaps it's better to think of this as the top of a cross-bed, an advancing front of pyroclastic deposition moving down the mountainside, overrun by later eruptions, which may have scoured off the upper few inches (??? pure speculation) or so before deposition.
mauna_kea_05
Really, the truncated tops of cross-beds are mini-angular-unconformities, when you think about it; just not with the same amount of time missing at a "real" angular unconformity (with millions of years missing) due to mountain building like the one at Siccar Point. (Video of cross-beds forming)

Here's something else which the clueless geologist might mistake for a sign of mountain building: mauna_kea_C_05
No, those aren't originally-horizontal strata that have later been folded. They're layers (again of ash and lapilli) deposited on the originally-rough topography of the mountainside, covering small ridges and filling small valleys. Where a given layer is exposed at higher elevation, I interpret to be a paleo-topographic high; where that same stratum is exposed at lower elevation, that's a paleo-topographic low. The roadcut reveals these layers have undulating shapes, but this is unlikely to be folding that results from tectonic compression: instead, I think it's showing us the lay of the ancient land surface.

Looking south, we could see past Mauna Loa to the actively erupting steam vent coming out of Halemaumau Crater at Kilauea Caldera (source of the vog!):
mauna_kea_07

Near the summit of Mauna Kea, there are a bunch of astronomical observatories:
mauna_kea_08

mauna_kea_10

mauna_kea_09

On the summit is where you find those examples I mentioned the other day of hawaiite, a rock of basaltic composition that is very dense (ostensibly due to erupting beneath the extra pressures of a Pleistocene ice cap):
hawaii_rocks_13

Here's me on the summit:
mauna_kea_B_03

View to the north from the summit: More cinder cones...
mauna_kea_B_02

Here's a YouTube video of me pointing stuff out from the summit (Kilauea, Hualalai, Mauna Loa, observatories, hikers, etc.). Unfortunately the wind makes it all but unintelligable, but I filmed it, doggone it, so I'm going to post it:



I found a beautiful example of a volcanic bomb up there:
mauna_kea_B_01

After the visit to the summit, we went for a hike to a small supposedly-glacially-gouged-out lake below the summit (Lake Waiau):
mauna_kea_B_04

Here's a Google Map, showing the lake's location:


I was surprised to see a thick biofilm on the bottom of the lake:
mauna_kea_B_05

Encrusting the pebbles and cobbles there, it reminded me of Nora Noffke's modern and Archean biofilm photos in the recent GSA Today, as well as my "Life in Extreme Environments" class this past summer at Montana State University.
mauna_kea_B_06

We saw some nice examples of structural geology on this hike. Previously, I've mentioned plumose structure, a branching pattern on the topography of fracture surfaces in fine-grained rocks. We saw some of that on blocks of basalt atop Mauna Kea, as in this example (again a repeat photo, but the other day I showed it to you for the vesicle; today I'm showing it to you for the plumose structure.)
hawaii_rocks_15

A similar feature are arrest lines, which again are minute variations in the surface of a fracture. Like plumose structure, which branches from a source point (where the fracture initiated) and branches out in the direction of propagation, arrest lines tell us about the development of a joint. Unlike plumose structure, though, they are not parallel to the propagating fracture front. Instead, they form perpendicular to it, and record how the fracture propagates in small "steps." Each of these arrest lines is interpreted as being a spot where the fracture grew a little bit, then stopped ("arrested") and then grew some more. In this case, the fracture face we're looking at started at the bottom of the picture and grew towards the top of the photo. You can even see some less-discernible plumose structure backing this up:
arrest_lines
Similar arrest lines can be seen in basalt images here and here...

We also saw some pretty spectacular xenoliths. Here's one of gabbro in basalt:
mauna_kea_B_08

Here's one of peridotite in basalt:
mauna_kea_B_07

And a few more:
mauna_kea_C_02
mauna_kea_C_01

My boots, with another volcanic bomb:
mauna_kea_C_03

Driving back down the mountain afterwards, we got this nice view of the cinder cones (pu'us!) in the eastern part of the "saddle" between Maunas Kea and Loa:
mauna_kea_C_04

This Mauna Kea excursion was one of my favorite things that I did on my all-too-brief trip to Hawaii. It was great to get up in the high country, where the air is thin (and vog free!) and the skies are deep blue, and the geology is surprisingly varied (at least it was surprising to me, and pleasantly so). The hike let us work up a good appetite, so we headed back down the mountain and straight to Thanksgiving dinner!

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Saturday, December 6, 2008

MSSE summer photos

The Masters of Science in Science Education program at Montana State University-Bozeman recently posted their list of summer courses for next year, and they illustrated it with a photo montage of images from last year's MSSE field courses. At the top of the stack? Yours truly, ogling the Grand Prismatic Spring in Yellowstone National Park:

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Friday, October 10, 2008

Topographic map of NOVA's Annandale campus

In my new work with the Campus Landscaping & Beautification Committee, I've been asked to come up with a few locations for a pet project of mine. I want to create a series of "fake" geologic outcrops on campus so we can have a "fake" geology field trip without leaving campus. The idea here is to create outcrops (using real rocks) in contrived positions, so that students get experience with figuring out things like rock identification, relative dating, transgressive/regressive sequences, faulting, etc.

I got this idea from Matty (2006), which I stumbled across while xeroxing science education articles for an MSSE class this past spring. The basic point is to have clear, useful teaching examples that students can access outdoors (emphasizing those kinesthetic and naturalist intelligences), without having to deal with the costs (legal, insurance, gas, carbon footprint) of a "real" field trip.

As a first step towards coming up with recommendations about where our initial "fake" outcrops will be placed, I asked our campus architect for a map of the campus. I told him I would prefer one with topography on it. Sure enough, he gave me one with topography... and a 1-foot contour interval! I don't think I've ever seen a topographic map with that level of detail. Anyhow, it's a beautiful thing, and I wanted to share it with you. I've labelled the buildings with their two-letter call numbers. (I teach in the CT building, for instance, but my office is in CF.*) Check it out:

Annandale_Topo

Comments on the map? Or on what you think ought to be included in a "Campus Geological Area"? You know how to comment...

* I hate these two-letter names. They are so utilitarian... Why must we call the CG Building "the CG Building," rather than Godwin Hall? That would be much more elegant and academic-sounding.

----------------------------------
Reference:
Matty, David J. (2006). "Campus landscaping by constructing mock geologic outcrops." Journal of Geoscience Education, v.54, n.4, p. 445-451.

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Sunday, October 5, 2008

Madison River Landslide, Montana

One of the most interesting spots I visited this summer was the Madison River landslide area, between Hebgen Lake and Ennis, Montana. Here's a photograph of the landslide scar:
madison_river_slide_5

Google Map of the area:


My "Northern Rocky Mountain Geology" class (through the MSSE program) visited the area this summer. Here's the class (all science educators of one sort or another) walking up to the viewing platform:
madison_river_landslide

What happened here? On August 17, 1958, a large earthquake ~10 miles to the east occurred. Known as the Hebgen Lake earthquake, it was a magnitude 7.5 on the Richter Scale, and shook much of the northern Rocky Mountain area. The earthquake's effects were most deadly where the Madison River drops down out of the mountains and into a graben to the west. There, schistose bedrock with a plane of foliation that dipped steeply into the valley was jarred loose. Sliding along the foliation's plane of weakness, and unthinkably massive amount of rock ( estimated at 70 to 80 million tons) went downhill, crushing a forest service campground and damming the Madison River. The momentum carried the rocky debris up the other side of the valley, where the Visitor Center is located today. There are some huuuuuuuge boulders there, as big as a house. 28 people lost their lives in the landslide (and related smaller-scale rockfalls further up the valley).

The Madison River began to back up behind the new dam, and it formed a "quake lake" called Quake Lake (sometimes called "Earthquake Lake," as in the Google Map above). The U.S. Army Corps of Engineers was worried that the dam would fail, draining Quake Lake rapidly and causing a catastrophic flood downstream. (They were cognizant that this had happened at the Gros Ventre landslide several decades earlier in nearby Wyoming.) So they bulldozed open a spillway, and got the lake level down to where they felt it didn't pose a huge flood risk for Ennis and other downstream communities.

But they didn't get the water back down to pre-landslide levels. Today, you can see a drowned forest along the shores of Quake Lake:
madison_river_slide_1

We also visited a couple of exposures of the Hebgen Fault scarp. Here's one at a campsite in the Gallatin National Forest. You can see the big dirty slope in the background: that's the actual fault scarp. Total offset here is something like 2.5 meters.
madison_river_slide_2

Another view of the fault scarp, looking along its trace.
madison_river_slide_4

Clever wayside sign, mimicing the offset in the land with offset in the sign:
madison_river_slide_3

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Saturday, August 16, 2008

Promoted

As of today, I'm now an Assistant Professor of Geology at NOVA. (I used to be an Instructor.) Yee-ha!

The Rank ladder at NOVA has four rungs: Instructor, Assistant Professor, Associate Professor, and Professor. With positive evaluations and the credits I accrued from my MSSE program, I qualified this summer to climb up a step. (NOVA does not have tenure; just contracts of increasing duration.) In another couple years, I'll be able to apply for promotion to the rank of Associate Professor, but I won't be able to make the jump to full Professor unless/until I get a PhD.

I'm a bit torn about the PhD: I feel like it's a research degree, whereas I'm not doing research in my job at NOVA. I'm an educator. And it's a fair bit of effort, that whole PhD thing: getting a degree specializing me to do research that I don't do. On the other hand, it sure would be nice to be finished with explaining to people that I'm not a doctor. And I'm sure it would help inform my teaching -to some extent- it's just a question of gains versus effort.

Time will tell; I get the feeling I'm going to start itching for another degree come next summer...

Anyhow, for the moment, I'm pleased with the validation of being promoted. Yesterday, I updated my main NOVA webpage to reflect the change. ...And the moustache.

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Monday, August 4, 2008

Examining life in extreme environments

A quick note here, just for the sake of completeness, on my final MSSE class of the summer: "Examining Life in Extreme Environments." This was a cool class, but structured in a different way from my other MSSE courses: it was set up more like a conference, with a variety of different speakers on different topics, interspersed with activities. The organizers, Susan Kelly and Monica Brelsford used a grant from NASA to help fund the course, which meant they had the money to fly speakers in from NASA Ames, the University of New Mexico, and the Wrigley Marine Science Center on Catalina Island, California. We also had a presentation piped in from Woods Hole. The goal of the class was to look at living organisms that manage to survive in 'extreme' environments, like really salty, really hot, really cold, really acidic, and so forth. Why study these bacteria and archaea? We're hoping they will give us insights into (a) the origins of life on Earth, and (b) the possibility of life on other planets or moons elsewhere in the universe. We had a field trip to Yellowstone National Park to look at microbial mats; we looked at cultures of hyperthermophiles; we listened to excellent talks by Mark Young (viruses as a source of genetic diversity), Ed Adams (new subzero lab tour), and Robert Szilagyi (thermodynamics of the origin of life). As you can see, it was pretty diverse -- all week long, always something new and interesting. I really enjoyed it!

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Saturday, July 19, 2008

Wildlife Ecology of Yellowstone

Back in Bozeman again after a great four day stint in Yellowstone National Park. I was up in the Lamar Valley ("Serengeti of North America"), checking out megafauna as part of my "Wildlife Ecology of the Greater Yellowstone Ecosystem" course. The hyper-enthusiastic course instructor, Dave Willey, took us to see this amazing ecosystem, using the wolf-elk relationship as a platform for understanding ecological connections. Dave knows a lot about wolves, and showed us plenty. We mainly observed the Slough Creek Pack, but we also saw one of the Druid Pack (the 'original' pack that was reintroduced to Yellowstone in the late 1990s). We also got to observe black bears, elk, bison, grizzly bears, coyotes, bighorn sheep, and a bunch of birds-of-prey.

One bear encounter is worth recounting here: We had hiked from the Lamar Valley out to Cache Creek, where rumor had it the Druid Pack had holed up. We spent the morning "glassing the slopes" (searching with binoculars), but didn't locate any of the wolves. No one had seen them in three days, and we were having the same luck. We began hiking back to the Lamar and our van. At one point, our group separated into two groups. I was at the tail end of the front group, and stopped to answer the call of nature before dropping down to the flat Lamar Valley floor. This short break to take a pee ended up preventing a major bear encounter, as it turned out. Why? It gave the front group time to get down ahead of me, so instead of staring at their backs, I was looking out over the valley. And there I saw two grizzlies heading through the sagebrush, on a direct line towards my colleagues! I called out to warn them (they couldn't see because they were on the same level as the bears, not elevated like I was). We all moved up onto the hill, so we could see the bears and the bears could see us. The tail end of our group caught up, and Dave shouted at them to get up to the high ground. Then we noticed another group of hikers, heading in on the trail. Through the binoculars, we could see that they were oblivious of the bears. We shouted to them too, and they moved up towards us. At that point, the lead bear huffed up and started galloping! "Oh shit," Dave said, "Who's got the bear spray?" When your wildlife ecology professor says "Oh shit," it's time to start worrying. Fortunately the bear's gallop lasted only twenty feet or so (a mock charge?) and then the pair resumed their amble through the sage. They crossed the trail a few feet from where the other group of hikers had been, and headed up a small wooded valley.

We all breathed a sigh of relief, and ventured down off the hill and onto the trail again, keeping a wary eye on the wooded valley. Safely past it, we relaxed and began hiking normally again, at which point we got a great look at a big black wolf trying to cross the Lamar River to our left! It was definitely the closest we had been to a wolf all week! The wolf got spooked by some fishermen, however, and retreated up the hillside on the other side of the road. Pretty cool stuff to see. The Yellowstone Ecosystem appears to be alive and well, even with wolves being "delisted" as threatened species in March, and then reinstated as "endangered" yesterday.

Also, while we were there, a man was attacked by a (probable) grizzly in his tent two campsites up the road. Pretty scary stuff, no longer being at the top of the food chain. These animals will eat you! For me, it was really insightful to get to experience some of that firsthand. This trip was the first time I had camped in the park (in spite of numerous visits over the years), and I really enjoyed the early morning and late evening wildlife viewing: that's the time to be out there!

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Sunday, July 13, 2008

Dinosaur paleontology of the Hell Creek Formation

Got back yesterday from six days out in eastern Montana, at Makoshika State Park. I was there on one of my four MSSE classes this summer, and I learned a lot. As many of you know, I'm trained as a structural geologist, not a sedimentologist. Though I use a lot of sedimentology (and fossils) in my Historical Geology course, there is much I have left to learn. Some of those gaps got filled in this week during "Dino Camp," though. Plus we had a lot of non-geologic fun!

The Hell Creek Formation is well exposed in Makoshika, as well as the overlying Fort Union Formation. The Hell Creek is latest Cretaceous, while the Fort Union is earliest Paleocene. The boundary formerly known as "K/T" is therefore between the two, and it records the changing of the eras: from Mesozoic to Cenozoic. I say "formerly known as K/T," since Tertiary is an archaic term that has been replaced (sort of) with Paleogene. The Paleocene is the first epoch in the Paleogene period. The sedimentologically-defined boundary between the two formations is the lowermost "significant" coal layer. We found this coal, the so-called "Z Coal," and you'd think that would be the K/Pg boundary, but it ain't that simple. True, there are dinosaurs below and no dinosaurs above, and it's also true that the Z Coal has been shown (rather shoddily, by the description we got) to have an iridium anomaly at its base. But there aren't any dinosaur fossils at all for 3 meters below the Z Coal, so the dinosaurs could have gone extinct well before the Z Coal was deposited (and before the iridium-rich clay layer was deposited). And of course, there's nothing in the deposition of a layer of coal that indicates it should be contemporaneous with a mass extinction -- it's just coal. Furthermore, the coal is lake coal, and the lake wasn't necessarily regionally extensive. It's a funny way of defining a critical geochronologic boundary: by the lowermost layer of lake coal in an area -- a criterion which could vary temporally from one place to another. Tricky business!

Anyhow, we prospected for dinosaur fossils. The course had two instructors, Jim Schmitt and Frankie Jackson. Frankie is a paleontologist, and she had a permit for collecting fossils on behalf of the Museum of the Rockies here in Bozeman. We found a lot of vertebrae, some five or six inches across. Plus, we found a bunch of leg bones, some rib fragments, and one of our team actually found the top of the frill on the back of a Triceratops skull! It was all pretty impressive.

In the evenings, we discussed scientific papers about field technique, the Hell Creek Formation, taphonomy, and the extinction of the dinosaurs. All our meals were cooked for us by Frankie's cool husband Bob, and so it was really ideal: Go out and learn all day, come back to camp to a hot meal, a cold beer, and a discussion of big picture ideas. My fellow teachers and I also played a lot of horseshoes and frisbee. To top it all off, when we got back to Bozeman yesterday, a group of us rented Jurassic Park and watched it over pizza and ale.

Next up: tomorrow I begin my Wildlife Ecology of Yellowstone course. Ought to be a similar high-octane experiential blast! More at the end of the week...

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Friday, June 20, 2008

One down, and off to the south

It's been a busy week for me. I've really enjoyed my first MSSE class of the summer, Dave Lageson's "Northern Rocky Mountain Geology." Dave led us on a series of field trips within driving distance of Bozeman: the Bridger Range, the Paradise Valley, the Spanish Peaks, the Hebgen Lake earthquake scarp and Quake Lake, and today out to Ringing Rocks, the Lahood Conglomerate, and a descent into Lewis and Clark Caverns. It's been a lot of cool geology, as well as a lot of driving! In the evenings, I've been keeping busy with Shakespeare in the Parks, seeing the B Side Players, and socializing with fellow MSSE teachers. All good stuff, but it leaves little time for blogging. Tomorrow morning, I'm off to the south. I'll be on the road for another five days or so, going to Las Vegas to pick up my father and brothers and then we're going rafting down the Grand Canyon starting next Wednesday. Along the way, I hope to visit some sites in Utah, and I hope to post some updates en route. After the Canyon float, I'll head back north, again through Utah and probably western Colorado (Black Canyon of the Gunnison), before returning to Bozeman for another three MSSE classes ("Dinosaur Paleontology of the Hell Creek Formation," "Life in Extreme Environments," and "Wildlife Ecology of the Greater Yellowstone Ecosystem"). Then back east, hopefully with some Niobrara Chalk and Pierre Shale site visits along the way.

Also, along similar "rock and road" lines, I had an article published in Geotimes this month on the roadtrip I did two years ago from DC up to Alaska and back. You can check it out here.

FYI, I got a new camera for this trip, and haven't been able to download any pictures off it yet (a stupid software issue), so that's the reason for the lack of photos lately. My apologies!

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Wednesday, June 18, 2008

The rest of the way

Sooo.... I've been "delinquent" about posting (if five days off counts as delinquent). But the long and the short of it is that I made it to Bozeman, and started classes, and have settled into life up here. After leaving Denver, I spent a couple days in Fort Collins, Colorado, staying with my undergaduate mentor professor Larry Wiseman. When I was at William and Mary, I forged a strong relationship with Larry, and that persisted even though I defected from biology (he's a developmental biologist, and chair emeritus of the department there) to geology (basically because they had more field trips). Anyhow, he and I would gather once a month or so for coffee and talk about life, the West, Ed Abbey, art, and science.

Now he's retired and pursuing bird rock art and also teaching cell biology at Colorado State University (in Fort Collins). We drove up to Rocky Mountain National Park and toured the various microbreweries and restaurants of Fort Collins (and Lyons). It was, in short, a good time.

Departing there on Saturday morning, I drove north through Wyoming, and camped at the end of the day at Buffalo Bill State Park, on the east flank of Yellowstone. On Sunday morning, I drove through the park, marvelling at six-foot-deep snow on Washburn Pass, and cruising along past tourists and bison galore. I stopped once, to look at the single petrified tree there, and then rocked and rolled on up the Paradise Valley to Livingston, and thence westward on the interstate to Bozeman.

In Bozeman, I'm enrolled in the Master of Science in Science Education program at Montana State University. It's essentially all science educators who are taking graduate coursework to become better science educators. And it's fun! This week, I'm taking Dave Lageson's class on the geology of the northern Rocky Mountains. More on that later, perhaps, but the point for now is that I'm enjoying it, and enjoying interacting with my fellow MSSE educators.

Tonight, I had a bonus, when we had a mini-conference of geobloggers. I guess there's somewhere around 50 geobloggers out there now, but we had four of them sitting at one table in Montana Ale Works, talking rocks and fossils and blogging and whatnot. That's got to be a record for the geoblogosphere. It was a lot of fun. Thanks to Mel, Brian, and Jeannette for making it happen!

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Wednesday, May 28, 2008

Annotated photos from Glacier NP

Cleaning up my hard drive today, before switching over to the laptop for my summer travels. Thought I would share a few annotated photos from my "Geology of Glacier National Park and surrounding areas" class that I took last summer.

Here's Chief Mountain:
chief_mtn

On the trail to Firebrand Pass, here's the contact between the Altyn Formation (lowest of the Belt Supergroup exposed at Glacier) and the overlying Appekunny Formation:
altyn_appekunny

The Purcell Sill is a readily recognizable feature high on the glacially-carved walls of Glacier National Park. This shot is from the trail on the way up to Grinnell Glacier:
sill

Here's a shot from Sun River Canyon, showing one of the many imbricate thrust faults there, with some glacial till thrown in as a bonus feature:
fault

Just outside of Sun River Canyon, we saw some nice recumbent drag folds on some thrust faults in the Cretaceous rocks:
recumbent_anticlines

This one was from early in the trip, on the road from Helena up north towards Glacier. Specifically, we stopped in Little Prickly Pear Canyon, near Wolf Creek, and saw these chevron folds in the Cretaceous rocks there:
anticlines

Along those same lines (folded Cretaceous strata), here's a gorgeous fold just outside the park's boundary, on the road leading north from Two Medicine towards Many Glacier:
big fold

No annotations on this one, but I wanted to share it anyhow: a blind thrust / drag fold complex, in the Grinnell Formation (exposed on the trail up to Grinnell Glacier):
blind_thrust

Lastly, some snow photos. I took this shot on my way up the trail to Grinnell Glacier, because the holes in the snow reminded me of the scary mask face from the Scream movies. But then on the way down, I realized I had the opportunity to document how much snowmelt occurs in six hours of Glacier NP summer weather. Hence, the bottom "after" shot:
snowmelt

That's it for today... Enjoy!

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Friday, May 2, 2008

Glacier N.P. and surrounding areas

Ahhhh.... the semester's just about over. Yesterday, I gave my last lecture and delivered two lab practical exams, and now all that's left to do is give the final exams on Tuesday. Not a moment too soon! It's been a very busy time over the past couple of months. What with my regular teaching duties, my Audubon class, my online MSSE class, GSW, various talks (like Wednesday's "Geology along the C&O Canal" at NSF), supervising homeschoolers visiting the NOVA chemistry lab, grant finagling, writing projects, and just life, I'm dog tired. I'm seriously ready for a nice break.

This ought to mean I'll have more time for posting on this blog, and hopefully that the posts will be richer and more thoughtfully composed.

Anyhow, let's share some pictures today. These are photos I took last summer on Dave Lageson's "Geology of Glacier National Park and Surrounding Areas" course at Montana State University - Bozeman. Dave is a great field trip leader, and I'm looking forward to another of his courses this summer: "Northern Rocky Mountain Geology."

For the Glacier course, we loaded up the vans in Bozeman and drove northwest through Helena and up to Sun River Canyon, one of the best areas in the world to look at multiple imbricated thrust sheets. Dave's been taking students here for a long time, and in fact "wrote the book" on it as a field trip location. In the photo below, the prominent cliff is Paleozoic limestone. The gently-sloping hill in the foreground, however, is Cretaceous shale. As is often the case, tectonics trumps superposition. Compressional tectonic forces have shoved the older rocks up on top of the younger rocks. (An analogous situation in the east is the Blue Ridge's Grenvillian rocks thrust up and to the west over Cambrian and Ordovician carbonates of the Shenandoah Valley.)
Sun River Canyon

Here's a map showing how the Canyon trends east-west across the north-south strike of these mutliple thrust sheets:

Next up: Waterton Lakes Park, Alberta. We slipped over the border and spent an evening drinking beer in the southernmost of the Canadian Rockies. ...Purty.
Waterton Lakes National Park at sunset

Here's us looking at the next day's field stops.
Talking maps in Waterton Lakes National Park, Alberta

Still life with fun stuff:
Maps, etc.

The next day, crossing back into the U.S., we stopped to get a good look at Chief Mountain, another scene of thrusting older rocks on top of younger rocks. Again, the lower unit is Cretaceous, but this time the upper rocks are older, much older. They're Mesoproterozoic rocks of the Belt Supergroup, thrust eastward along the Lewis Thrust, which underlies the base of this mountain. Chief Mountain is an erosional remnant of the Lewis Thrust sheet: that is to say, erosion has cut into the thrust sheet and left behind this one isolated outpost of what was once a continuous sheet of allochthonous rock. (It's a klippe!) The thrust sheet picks up again in the mountains of Glacier National Park.
Chief Mountain

Next day: a hike up to Grinnell Glacier, a classic glacier in a park named for classic glaciers. Like all of Glacier's glaciers, however, Grinnell is melting. It's receded quite a lot, as repeat photography shows:


Here's a view looking down the Grinnell Valley at a string of pater noster lakes blue with "glacial flour."
View down the Grinnell Valley.

Here's what's left of Grinnell Glacier:
Grinnell Glacier's remnants

Where the glacier once stood, there's now a new lake. Several of my classmates decided that they would go for a dip. Note: all these guys are from Montana...
Fools

As for myself, I stayed out of the water, amusing myself with the amazing sedimentary structures displayed by the Belt rocks. Here's an outcrop of the Grinnell Formation, showing amazing Mesoproterozoic mudcracks. (As David Byrne said, "Same as it ever was, same as it ever was...")
Precambrian mudcracks

Glacier's Belt Supergroup rocks are reknowned for their stromatolites, fossilized cyanobacterial mats. Here, a stromatolitic layer in the Helena Formation was exposed in cross-section by glacial erosion. Penny for scale (atop middle stromatolite).
Stromatolites

And here's another view of the same stromatolitic layer, exposed in map-view section (a horizontal slice, as opposed to the vertical outcrop above). Enthusiastic geologist for scale, imagining doing the backstroke through the Proterozoic Belt Sea.
Stromatolite worship

And... that's it for today. I'm off to the Blue Ridge this weekend, so I won't be posting again until Monday or so. But hopefully I'll have some cool new images from Virginia's oldest rocks to share at that time. Be good.

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Wednesday, February 20, 2008

Joining NAGT

I've added a new organization to my roster of professional affiliations: the National Association of Geoscience Teachers.

Joining NAGT has been on my list of things to do for a while -- The Journal of Geoscience Education is the journal that they publish, and I'm told that it's an excellent source of information about how to teach geology well. Teaching geology well is the motivation for my current pursuit of a science education master's degree from Montana State University. For my capstone project, I think I'm going to look at the effect of field trips on geology learning, and I suspect that the Journal of Geoscience Education will have some relevant articles to enlighten my thinking on that topic.

I'm a geologist today because of the wealth of field trips offered by my alma mater, the geology department at the College of William and Mary. I'm convinced that their educational value is positive, but I'm curious to know how positive. It astonishes me that some geology educators don't hold this conviction, but I'm undoubtedly missing something. I'll undoubtedly have more to report on this topic as time goes by.

I'm also psyched about joining NAGT's ranks because they offer a series of grants. Getting small educational grants is my new hobby, so I'm looking forward to making some good stuff happen at NOVA with some sum from NAGT.

The image above shows the distribution of NAGT members (red dots) in the United States in 2006. Google Earth overlay by Jeff Tolhurst, from the NAGT website.

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Friday, February 15, 2008

The Bridger Range, Montana

We've had a cold week in the mid-Atlantic this week, and increasingly my thoughts turn to warmer conditions and the summer. Last year, this year, and next year, I'm scheduling time in Bozeman, Montana, to take classes at Montana State University. I'm working on a second master's degree in science education. It's a pretty cool program which mixes educational practice and "action research" with science elective courses, including plenty of geology offerings.

Today in the blog, I thought I would begin the process of share some images from my time out west last summer. I'll start with the Bridger Range, north of Bozeman. Here's a meadow where we parked the vans before hiking up into the hills on Dave Lageson's excellent Alpine Field Studies seminar:
Meadow below Sacagawea Peak

Once we had huffed and puffed up about tree line, we started to see some pretty cool geology. Here for instance, you can see tilted, folded, faulted Mississippian-aged strata that have been carved into by a glacier. A few minutes after this photo was taken, the class walked straight down into this cirque and climbed up the other side: there's some serious gravity-fighting going on with a route like that. We had lunch on the other side at the top of that orange-colored chute in the upper left:
First day of class

In the photo below, my hands bracket a tilted zone of paleo-karst in the Mississippian-aged Madison Limestone. With massive limestone above and below, this orangey zone speaks of a time when the limestone deposits of this area were exposed at the surface. Caves and sinkholes developed, as did an iron-rich paleo-soil. It probably looked a lot like modern-day Florida, without the strip malls and retirees. Later, the sea returned and deposited more limestone on top. The paleo-karst is obvious because it contains big blocks of limestone from cave-roof collapse, and is stained by hematite and limonite:
My hands bracket a zone of paleo-karst

Fellow DC resident and geology educator Nez Nesbitt follows Dave Lageson (the instructor) south along the crest of the range. The drop to either side was substantial, including the headwall of a cirque to the left (east). The loose scree we were walking over added an additional challenge: Walking the arete

In all that scree on the slope we're walking over, there were some cool fossils, including this awesome crinoid calyx ("head" region) - front and back views:
Crinoid calyx (front side)Crinoid calyx (back side)

Atop a peak, we paused for a break, and Dave unfurled his Tibetan prayer flags to flap in the wind. I was struck by how a simple little string of cloth imparted a really cool aesthetic to the mountain-top:
Tibetan prayer flags

This is the trail leading down Sacagawea Cirque. There's some substantial switchbacking going on here:
Trail up Sacagawea Cirque to the Peak

Here's me atop the highest peak in the Bridger Range, Sacagawea Peak. The views are pretty good from up there:
Me on top of the mountain.

The class spent the next day mapping glacial landforms in Sacagawea Cirque: it was fun, but I didn't take as many pictures then. When the mapping was over, I prowled through the lateral moraines for fossiliferous chunks of limestone, and found some awesome rugose corals and other treasures. These samples now reside in the NOVA Historical Geology teaching collection.

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