Whew! A busy day at the Geological Society of America meeting in Portland, Oregon. I started off the day in the two-year-college session, culminating (for me, anyhow) in my talk about the role that field trips play in my geology classes at NOVA. I believe in spirited presentations, so I moved away from the lecturn and spoke extemporaneously about my images and data, and the talk was well-received by the audience -- or at least that portion that chose to tell me what they thought. After the talk, I was really tired out (I hadn't realized I was stressing about the talk, but apparently I must have been.) I went back to the hotel and took a shower, dealt with some mortgage stuff (I'm buying a condo in DC), and then semi-refreshed, headed back to the fray at the Convention Center.

I've met another several geobloggers: Brian Romans and Kim Hannula. Geoblogger Lockwood Dewitt sent me a rock (natrolite in calcite! likely from a pillow basalt!) via roaming geoblogger "Silver Fox." Cool. I dig it. I had some people come up to me out of the blue and tell me that they read this blog, and that is super cool to hear. Thanks!

In the afternoon, I went to a few sessions about volcanism and the end-Permian extinction, history-of-geology, and I forget what else.

In the late afternoon, the beer began flowing. I started off at the W.W. Norton publishing company's beer bash, where I brushed shoulders with Walter Alvarez, met the author of my Physical Geology textbook, Steve Marshak, and chatted at length with Bob Lillie of Oregon State University about getting the National Park Service better educated about their geological resources. Then it was off to the AGI reception, where I won a bottle of wine and got to chat with David Williams, author of Stories In Stone. Meg Sever, the editor of EARTH, with whom I've e-mailed a zillion times, but never met. Turns out Meg went to William & Mary, like me (and Jessica Ball, also at the AGI reception), so the three of us trooped upstairs to the William & Mary alumni reception. It was good to see Brent Owens, Heather McDonald, and Chuck Bailey there, as well as other W&M geology grads (including Graham, who reads this blog! Hi Graham!).

The evening's final event was the much-ballyhooed geoblogger's meet-up. At 8pm, about fifteen of us assembled at Tugboat Brewing Company, a cozy, charming little pub in downtown Portland. Every time someone walked through the door, a rousing, "Yeeeaaaahhh!!!" cheer went up. And every time someone left, they got booed! It was terrific fun meeting everyone that I've had these online geoblogging relationships with over the past ~1.5 years, and I think a good time was had by all. I'll put some photos up later... [Other online reminiscences about the meetup: Chuck and Jessica.]

Labels: books, geology, meetings, national parks, nova, oregon

Another amazing image from NASA's Earth Observatory. This one shows the smoke plume that resulted from the "Arnica Fire" in Yellowstone National Park. Pretty impressive shot...

Labels: national parks, wildfire, wyoming, yellowstone

As noted earlier, I had the good fortune to spend last week in Yosemite National Park, celebrating the wedding of my friends Jason and Lindsay, and in general poking around in one of the coolest places around. Below, a summary of the three-day trip:

Friday:
Lily and I flew to Modesto, California, and rented a car. It took about two hours to drive up to Evergreen Lodge, where we checked in and then headed out for a short hike in the Hetch Hetchy area. Hetch Hetchy was dubbed "Yosemite's sister valley" by John Muir in an attempt to keep it from being dammed. But the city of San Francisco had been destroyed in 1906 by earthquake-induced fire, and the call for a reliable water source was an important force in overpowering Muir's conservationist ideals. Ken Burns apparently explores this saga, the first instance of "development vs. conservation," in the second episode of his new National Parks series. (I saw the first episode, but haven't caught up on the rest of it yet.) The valley was dammed in the 1920's, creating the Hetch Hetchy Reservoir:


Here's the O'Shaughnessy Dam, named after the chief engineer of the project:


I didn't find it as spectacular as Yosemite, but it was sure a pretty place. Walking along the north side of the reservoir, I reaquanited myself with some fine Sierran granites and granodiorites. Here's a sweet little xenolith (or maybe an MME; how can you tell an MME from a mafic xenolith?):

Back to the Evergreen for the rehearsal dinner (Oktoberfest theme!) and then bed.

Saturday:
Up early, got some coffee, drove an hour to reach the Yosemite Valley. I liked how quiet things were compared to the throbbing pulse of summer. This view of El Capitan, for instance, is typically mobbed with tourists. This day, we had it to ourselves for five minutes or so, then shared it with one other car:


Time to stretch the legs! We decided to hike up to Vernal Falls. On our way up, the base of the falls was still in shadow, with low-angle morning sunlight dramatically illuminating the upper reaches of the falls:


Looking back down the valley we had climbed up... I like the dark shadow of the cliff merging with the dark shadows of the trees below:


But if we set the camera's F-stop a bit differently, we can see what's going on in all that shadow. There's the trail we climbed up, with fellow hikers for scale:


Up top, photographing the waterfall:


On our way back down, with more of the falls illuminated as the sun rises in the sky:


Looking north across the valley from where we parked our car, marvelling at the huge exfoliation joints there: rounding these exposed plutons into granite 'domes.'


... or Half Domes, as the case may be:


A view from further out, again with Half Dome the most striking landform:


Then, we headed back to clean up before the wedding. Great ceremony, amazing meal. Drinks, dancing, rhubarb jam, bluegrass, reminiscing with old friends and new. Ahhh.

Sunday:
Breakfast and coffee with the wedding party, then off to check out some big trees. We drove to the Tuolumne Grove of giant sequoias. It started snowing on the way there, but we didn't let that deter us. On the hike down from the parking area (where, by the way, they had closed the Tioga Road), we found this nice example of spheroidal weathering in an outcrop of granite:


But the real attraction was the enormous sequoia trees. Here's one:


And a dead one, with a car-sized hole cut through it:


I found these trees very impressive: they were just stunning in their grandeur and immense age. Snow continued to fall as we left. We had to get going to make our flight home. Somewhere on the way down the mountain, Garry Hayes and his wife passed us going up the mountain. Ships passing in the night -- sorry I missed you, Garry! We made a couple of roadside outcrop stops, then got back to Modesto and traded in the car for an airplane. Our "redeye" route back to DC took us through San Francisco and Los Angeles, and I ran into Thomas Friedman in the airport. Got back to BWI at 6am, and headed off to work...

Labels: california, glacial landforms, national parks, plants, travel, tv, water resources, xenoliths

My friends Jason and Lindsay had the good sense to get married in Yosemite this past weekend. So I enjoyed visiting the park, including some new places I hadn't been before, as well as the nuptial festivities. More later...

Labels: california, glacial landforms, national parks

Here we have some nice little glacial striations exposed in the Grinnell Glacier cirque in Glacier National Park, Montana. These grooves were carved by pebbles and other clasts within the glacial ice as it flowed over this outcrop of the Mesoproterozoic Helena Formation (part of the Belt Supergroup). Perhaps some of the same pebbles you see in this photo were responsible for acting as carving tools -- though the 'hand' that wielded them, Grinnell Glacier itself, melted away from this point sometime since 1939.

Also of interest to me in this photo is the lingering stain of water around the joint set in the upper right. I'm fascinated at the interplay between physical and chemical weathering, and seeing stuff like this emphasizes how even a simple hairline fracture can help funnel water, with all its destructive effects, deeper into the heart of an outcrop. Weathering is focused on these areas, and in another century this outcrop may look quite different.

Labels: glacial landforms, glaciation, joints, montana, national parks, pleistocene, proterozoic, sediment, snow, weathering

On our hike to Grinnell Glacier this past July in Glacier National Park, I found lots of cool cobbles of float, mainly of the Mesoproterozoic metasedimentary rocks that make up the bulk of the park: the Belt Supergroup. One of these formations, the Helena Formation, is intruded by a diorite sill known as the Purcell Sill. It's a prominent rock unit showing up as a black stripe within the lighter-colored Helena Formation, exposed high on the glaciated walls throughout the park. Occasionally, you'll find pieces of it as float, and I noticed that the higher we climbed up, the more of it we saw. Here's one of my favorites among these pieces of the Purcell Sill:


This cobble shows beautiful slickenlines, small gouges into the rock as neighboring rock ground across its surface, along a fault. These physical gouges are decorated with a chemical accoutrement: the metamorphic* mineral epidote, which is a gorgeous grassy green.

Labels: faults, igneous, metamorphism, minerals, montana, national parks, proterozoic, structure

Took all these images of joint surfaces this summer in Glacier National Park on my Rockies trip. Enjoy!

Appekunny Formation, with two concentric ribs:


Grinnell Formation, showing well-developed hackle fringe (rough area at bottom):


In the lovely fine-grained limestones of the Helena Formation:

Labels: montana, national parks, proterozoic, structure, weathering

(Parts 1, 2, 3, 4, & 5 of this series...)

As we were climbing up a steep snowfield, we saw something that made us rush up to the top:


Interpretive sketch:

At first, we thought this was a big isoclinal synform that was cross-cut by a ptygmatically*-folded granite dike, but closer inspection at the "axis" of the "fold" revealed that it was instead just the trailing edge of a big boudin. It pinched down and then swelled again in the downward direction, hidden in this photo by the snowpack. Not quite as cool... but still pretty cool. And I can never say no to ptygmatic* folding, regardless of the setting.

This is also kind of cool:

What you're looking at here is a gneiss, with alternating layers of coarse-grained mafic and felsic minerals. The view of the photo is orthogonal to the plane of foliation, but the boulder has been weathered so that in some places the uppermost mafic layers has been worn away. There's one spot where you can "see through" the mafic layer into the underlying felsic layer (upper right) and another spot where there's a little isolated scrap of the mafic layer where the surrounding material has been weathered away. This reminded me of a larger-scale phenomenon where the same thing happens to thrust sheets: an erosional hole through a thrust sheet into the rock beneath is a tectonic "window" or "fenster" (German for window). An erosional remnant of a thrust sheet is a "klippe." The Grandfather Mountain Window in North Carolina is an example of a fenster. Chief Mountain in Glacier National Park, Montana, is an example of a klippe. So this little boulder gives us a nice physical analogue for regional-scale tectonic/erosional features.

Ahh... what cool stuff to see and think about. But the sun was setting, and we had to head back to camp and the rest of our team... Tomorrow: the story of the long hike home.

________________________________
* Really, more of a "cuspate-lobate" fold, without the parallel limbs that make for a truely ptygmatic fold.

Labels: analogies, art, montana, national parks, north carolina, nova, structure, travel, wyoming

(Parts 1, 2, 3 & 4 of this series...)

Today we'll look at some of the structural geology photos I took in Hanging Canyon, Teton National Park, Wyoming. These are all rocks of the Archean-aged Wyoming Terrane (or "Wyoming Craton"), one of the most ancient pieces of crust that make up the quilt-like North American continent. They include both metamorphic and igneous rocks that have been suffered enjoyed being deformed by tectonic processes.

Labels: archean, igneous, metamorphism, national parks, nova, structure, travel, wyoming

Parts 1, 2, & 3 of this series are at these links.

Today and tomorrow, I'll share some of the gorgeous Archean rocks that are exposed in Hanging Canyon, Grand Teton National Park, Wyoming. Today: the igneous stuff. Tomorrow: the structural stuff.

There were many pegmatite dikes that we saw along the hike. Here's a lovely one cutting across the metamorphic host rock:


A close up of some big muscovite "books" in the pegmatite:


A couple of parallel pegmatite dikes cutting across granite:


Here's the largest single feldspar crystal I've ever seen in the wild. The crystal starts to the left of my boot and continues for over a foot to the left of that. Its color varies between bluish gray and whitish. Where the left-most and most prominent blue stripe is, that's the edge of this monster megacryst:


Huh... Only four "igneous" photos... I guess I'll make up for that with tomorrow's structural geology post about Hanging Canyon... I have about forty photos of folds and boudins and what-not to share...

Labels: archean, granite, igneous, minerals, national parks, nova, structure, travel, wyoming

Part 1 and Part 2 of this series described the journey up from Jenny Lake to Hanging Canyon. Today, we pop up over the threshold of this hanging valley and see what we can see...



As it turns out, there's some snow up there:


We manage a few clumsy glissades:


And what's going on with this hole?


Aha! A dark rock with low albedo absorbs energy from the sun, releasing it as heat and melting the surrounding snow. Cool!


Times like this, I just love my job:


Ken shows off some glacial striations on the bedrock:


Pointing in the direction of glacial flow:


We then opt to climb up even higher, to peer down into the neighboring valley, the much larger Cascade Canyon...



Steep climb, with tarn in the background; Joel appears to be enjoying himself:


Here's a Google Maps "terrain" view of the area, showing the relative locations of Jenny Lake, Cascade Canyon, and Hanging Canyon.


Wow... Once we got up over that last little knife-edge crest, we had a pretty amazing view.


And what did we see along the way? More on that in tomorrow's post (Hint: pegmatites and old folds)...

Labels: glacial landforms, glaciation, national parks, snow, travel, wyoming

Today, picking up where we left off yesterday, some images from the hike upwards from Jenny Lake to Hanging Canyon...

Joel and Ken take a breather:


The approach to the final lip of Hanging Canyon:


A view down over Jenny Lake and Jackson Hole:

Jenny Lake is dammed by an end moraine (which is characterized by pine trees growing on it here, making for a nice dark stripe around the lake).

We could also see across Jackson Hole to the Gros Ventre valley, where the Gros Ventre lanslide scar was readily visible:


...And lastly, the view to the north, over Jackson Lake (with String Lake in the middle distance):


More tomorrow about what we found once we got up into Hanging Canyon itself... (Hint: it's white and cold and fun to ski on...)

Labels: glacial landforms, mass wasting, national parks, nova, travel, wyoming

One of the highlights of this past summer's Northern Rockies field course was an afternoon set aside as a "choose your own adventure" hike in Teton National Park. Some students opted for Cascade Canyon; others climbed Blacktail Butte. Four of us wanted something really challenging, so we chose Hanging Canyon at the recommendation of my friend Amy Manhart, who lives in Jackson and knows the Tetons like the back of her hand.

We took a ferry across Jenny Lake along with the Cascade Canyon Crew, and then started climbing up. A thunderstorm rolled up Jackson Hole, with much ominous booming and lightning, but we didn't get hit with the storm directly. The climb was very steep, but we entertained ourselves along the way with a geological conundrum: We discussed how best to interpret a hypothetical piece of float that is half granite and half diorite: Is it more parsimonious to guess that the granite represents an intrusion or an inclusion? The implications for the relative dates of the two units are huge: if the diorite is an intrusion, it's younger than the granite. If the diorite is a xenolith (an inclusion) within the granite, then it's older than the granite. Consider the possibilities:



Ultimately, there's no answer to this question without finding an outcrop of the rock in situ, which is why it's entertaining to consider when you're slogging up a 2000 foot hillside. My co-instructor Pete Berquist and I upped the ante by each doggedly defending one of the two indefensible interpretations and sticking to it for the sake of argument. Pete was the xenolith man, whereas I came down fully on the side of the dikes. Our students Joel and Ken were "fortunate" enough to listen to Pete and I bicker about the relative merits of our favored interpretations. Rest breaks came whenever either Pete or I found a boulder along the hillside that showed evidence to support our position. We would stop to consider it, catch our breath, and the resume the uphill climb and the argument. The bad weather passed and the day was beautiful. We were unencumbered by the need to reach a conclusion or acknowledge the obvious: the best interpretation is that such half-&-half clasts "cannot be interpreted."

Here's Pete posing with an obvious dike (I forced him! Ha!):


Here's me posing with an obvious xenolith (Oh well, fair's fair...):


We had a similar ongoing "argument" on the trip about the merits of "Tertiary" versus "Paleogene." I think it keeps students amused to see their professors going back and forth over geologic ideas -- surely if these fellows spend this much energy and thought discussing some geologic question, it must be valid and important... ...right?

More on the Hanging Canyon hike tomorrow...

Labels: archean, geologic time, igneous, national parks, nova, structure, travel, wyoming, xenoliths

Yesterday, I took a hike with some friends in Shenandoah National Park, and we encountered a bunch of interesting insects. I took a couple of photos, the best of which I'll share here.

Monarch butterfly caterpilar:


Moth Butterfly and hover-flies enjoying thistle nectar:

Labels: arthropods, national parks, shenandoah

All photos in this post by Rockies student Charlie Corrick.

Obstacle in the road...


Tetons...


Charlie and Jared on Blacktail Butte:


Luke on Blacktail Butte:


Charlie, Luke, and Jared on Blacktail Butte:


Checking out the fault scarp of the Hebgen Lake Fault, north of Hebgen Lake:


Examining the Grinnell Formation for the first time:


Looking down the St. Mary Valley, Glacier National Park:


Stromatolites in the Helena Formation, Glacier National Park:


Victoria points out the contact of the Purcell Sill with the surrounding Helena Formation (limestone), Glacier National Park:


Callan points out the contact of the Purcell Sill with the surrounding Helena Formation (limestone), Glacier National Park:


Pete and Joel point out the contact of an apophysis of the Purcell Sill with the surrounding Helena Formation (limestone), Glacier National Park. Notice that the sill cuts across stratification down by Joel's legs.


At the Bozeman Airport on the way home, John entertains us with geology songs he composed, which cracked up the instructors:

Labels: glacial landforms, montana, national parks, nova, proterozoic, travel, wyoming

Two examples of plumose structure, beautifully expressed in a small boulder of the Helena Formation (Mesoproterozoic limestone from the Belt Supergroup) in Glacier National Park, Montana. Photo by Bob L'Hommedieu.

Labels: field trips, limestone, montana, national parks, proterozoic, structure

Our third Rockies training hike took place Saturday. Six of us hiked White Oak Canyon, in Shenandoah National Park. It was about an eight mile loop, with six big waterfalls on it. There were a lot of plungepools where other hikers were swimming.

There wasn't an astounding amount of geology on the trail: it was mostly Catoctin Formation, with a few outcrops of underlying Grenvillian granitoids. A few nice amygdules; no columns.

The waterfalls sure were purty, though. Here's Jason at the uppermost falls (86 feet tall):


Me departing from one of the lower falls:

Photo by Chris McMahon

I got home tired and sore from this hike -- it was a good time, but I slept well last night as a result!

Labels: blue ridge, falls, geomorphology, national parks, proterozoic, shenandoah, virginia

Last Saturday was my Field Studies in Geology trip to Shenandoah National Park. Here's a few shots from the day's geologizing...

Garnets in the Pedlar Formation granite gneiss, oldest rock in the park at ~1.1 Ga.


Meta-basalt columns of the Catoctin Formation (photo by Mathina Calliope):


At the end of the trip, I have the students order a series of strips of paper with different geologic events in the park's long geologic history. They have to figure out the proper order based on what they learned that day:





Lastly, a group photo overlooking the Browntown Valley:

Labels: field trips, metamorphism, minerals, national parks, nova, shenandoah, teaching

After the Garth Run high-strain zone and a night hanging out by the campfire at Heavenly Acres with the William and Mary Structural Geology class, the second stop on our Structural Geology trip was in Shenandoah National Park, looking at the deformed meta-basalt columns on the Limberlost Trail. Longtime readers of the blog have seen these unique (in my experience) columns before, in a post from last May.

This is an outcrop of the Catoctin Formation, a series of (mainly) basaltic lava flows that erupted sometime older than 565 Ma (only the youngest, rhyolitic layers have been dated, and evidence suggested that significant amounts of time may have passed between the eruption of each stratum of basalt deeper down in the stratigraphic stack). As the lava cooled, it developed cooling fractures that formed perpendicular to the isotherms. These fractures likely initiated at the top and the bottom of the flow, and propagated towards the middle over time.

Later, during Alleghenian mountain-building (~300 Ma to ~250 Ma, roughly), the rocks were subjected to greenschist-facies metamorphism, and were deformed. The basalt's consituent minerals re-equilibrated and reacted to become other minerals, most notably chlorite and epidote (both of which are green).

Here's John and Joe checking out the columns:


Exquisite! Even arrest lines on the side of each column are preserved. In an undeformed basalt column, these arrest lines would be perpendicular to the column edge. Here, they have a pronounced angular relationship, indicating the shearing of the overall column:


Bobby measures the angular shear along the length of the column:




Goofball professor poses with column:


Jay plays the column like an electric guitar:


We found some nice plumose structure too:


Finally, we evaluated the concentric rings of minerals filling amygdules (vesicles that had been infilled with mineral deposits after lithification) in an attempt to determine whether they could be used as strain markers, or whether they may have attained their ellipsoidal shapes due to stretching of the bubbles in the originial lava (i.e. like this) and then been infilled with minerals:




...and then we were off to Field Study Area #3...

Labels: appalachians, basalt, field trips, igneous, metamorphism, national parks, primary structures, proterozoic, shenandoah, structure, teaching

Today's NASA Earth Observatory image of the day is of a place that is near and dear to my heart, the Etosha Pan of Namibia:



In late 1996, my father and I took a trip to Namibia to study termite mound gas exchange as part of an Earthwatch expedition, and afterwards we rented a car and went off on a little safari. Up in Etosha National Park, the wildlife was pretty amazing. Here's a leopard that crossed the road in front of us, immediately followed by a second leopard:



An oryx (or gemsbok):


...And an elephant, drinking from one of the watering holes that fringe the main salt flats:


Namibia has been getting a lot of water lately, as evidenced in compare/contrast images like these, also from NASA's Earth Observatory:

June 2007:


Last week:


And that brings us back to the first image:


In this picture, you can see a new package of river water coming south into the Etosha Pan from the Oshigambo River of Angola. This is "fresh" water, but it has a dissolved load of sediments in it. As the water hits the hot, baking expanse of the Etosha Pan, it evaporates, but the dissolved ions within don't have that option. So they become more and more concentrated, and settle out in a chemical precipitate. This is where all the salt comes from: even freshwater is a little bit salty, and when you evaporate it repeatedly in an enclosed drainage basin, evaporite minerals accumulate there.

Labels: africa, critters, floods, mammals, namibia, national parks, salt, travel

Almost a week after the field trip to Old Rag Mountain, and the Facebook-hosted pictures keep trickling in. Here's some shots by NOVA student Eileen Lodovichetti, and an ensuing discussion of feeder dikes and supercontinent breakup.

Here's a shot of the upper reaches of Old Rag, showing the characteristic spheroidal weathering of the Old Rag Granite and the relative lack of trees on top:

photo by Eileen Lodovichetti

...And here's a shot that Eileen took which shows the interior of one of the weathered-out feeder dikes we had to hike through on our way to the summit. You can actually see the classic geoprofessorial arm-waving caught in blurry motion!

photo by Eileen Lodovichetti

This is one of the coolest things about hiking Old Rag: after scrambling up on top of spheroidally-weathered granite domes, you drop into these tabular "hallways." The astute observer will note that the floor is made of a fine-grained, dark-green-colored rock, quite distinct from the light-colored, coarse-grained granite that makes up most of the mountain. These are dikes of metamorphosed basalt that intruded the granite during the breakup of the supercontinent Rodinia in the Neoproterozoic era of geologic time.

Here's one of my former Field Studies in Geology students, Mike Nelson, pointing out a similar dike along Skyline Drive, in the main part of the park:


Basically, the story goes like this: Around 1.2 to 1.0 Ga, continental fragments amalgamated into a supercontinent called Rodinia. In Virginia, this is recorded in the rocks of the Blue Ridge province, where the basement consists of granitoids (granites and related rocks) and metamorphosed granitoids (gneisses, mylonites). Among the youngest of these is the Old Rag Granite, which intruded the Pedlar Formation granite gness around 1.0 Ga.

Later, Rodinia broke apart, resulting in an extensional tectonic regime and mafic volcanism. Fractures opened up in the Old Rag Granite and funneled mafic magma towards the surface. Massive eruptions of basalt blanketed the landscape. The resulting layers of basaltic lava are known as the Catoctin Formation. At Old Rag Mountain, we can see some of the plumbing that led to these flood basalt eruptions: these are feeder dikes, because they "fed" the eruption above them.

Because the dikes (which were metamorphosed to greenstone during ~300 Ma Appalachian mountain-building) weather more rapidly than the Old Rag Granite, they are typically recessed into the landscape. That's what makes the "hallways" in the photograph above. Here's two more images, showing these weathered-out feeder dikes:



Check out how there's moderately-developed columnar jointing extending across the dike. These columns form perpendicular to the cooling front, and the dikes would have lost their heat out the sides. In horizontal lava flows, the heat is lost from the top and bottom surfaces, so you get vertical columns. Here, a vertical dike produces horizontally-oriented columns. Hikers appreciate these "steps" as they squeeze through the dikes on their way up the mountain.

Here's a map of part of Shenandoah National Park:


Please ignore the "hover" instructions at the lower right. I've reproduced the "hoverable" image below. Key: the orange is the Pedlar Formation. The pink is the Old Rag Granite, and the green is the Catoctin Formation. Feeder dikes of the Catoctin are shown as green lines.

Now, let's take away the map, and just preserve the orientation of the feeder dikes. This will tell us the overall tectonic stretching direction:
Various plate reconstructions show either Amazonia or the Congo craton offboard of Virginia at the time Rodinia broke apart and the Iapetus Ocean began seafloor spreading. I've illustrated it here as the Congo, but that might be wrong.

So: the hike up Old Rag is great exercise, and offers scenic views, but for those willing to consider the rocks and how they got there, it's an insightful view into the tectonic past.

Lastly, here's a lovely, well-developed weathering rind on the Catoctin meta-basalt (greenstone). When the dark green rock adjusts to the conditions at the Earth's surface, it breaks down, resulting in the tan/"buff" color on the outside. You're watching the rock "rot" from the outside surface, working its way inward:


More on the geology of Shenandoah National Park can be seen at this page on my website.

Labels: appalachians, basalt, blue ridge, field trips, metamorphism, mountains, national parks, nova, plate tectonics, shenandoah, structure, weathering

Last weekend, I took a group of students, mostly from NOVA but also 3 from GMU, up to hike Old Rag Mountain in Shenandoah National Park.

Here's a Google Map showing the terrain (and trails, which is a cool new addition to the already cool Google Maps):


The crew discusses debris flow deposits in the forest on the way up the mountain:

photograph by Charlie Corrick

The first spot where we get a nice view out over the valleys below:

photograph by Charlie Corrick

Spheroidal weathering in Catoctin Formation greenstone:

photograph by Jared Fortner

Spheroidal weathering in granite (the Old Rag Granite, 1.0 Ga):

photograph by Charlie Corrick


photograph by Charlie Corrick

Student Jared atop a spheroidally-weathered boulder of the Old Rag Granite:

photograph by me

Grain-size differences in the Old Rag Granite (balanced atop my leg):

photograph by me

Non-foliated Old Rag Granite (showing lovely "blue quartz"):

photograph by me

And the foliated version of the Old Rag Granite:

photograph by me

Labels: appalachians, basalt, blue ridge, field trips, geology, granite, igneous, mountains, national parks, nova, structure, weathering

Here's some photos from today's Physical Geology class field trip to the Billy Goat Trail. It actually snowed on us a little bit... cold! My student Luke O'Neil took all of these, hosted on his Facebook page, and this is an experiment to see if I can post Facebook photos on my blog... keeping my fingers crossed...

Migmatite:


Il profesore showing tilted tree trunks (knocked in a downstream direction during floods):


Folded graded bed in metagreywacke:


Students circle around an exotic boulder of the Catoctin Formation greenstone (from the Blue Ridge province); the boulder was transported downstream by the ancestral Potomac River when it was flowing on the Bear Island strath, before incision and abandonment of the former river bottom to become a bedrock terrace:

Labels: field trips, geology, maryland, national parks, nova, piedmont, rivers, teaching

The backlog of photos from my hikes several weeks ago still looms. I've showed you exotic cobbles, migmatites, graded beds, flood debris, and boudins, now for some folds...

As with the others, these are images from the Maryland Piedmont, along the Billy Goat Trail in C&O Canal National Historical Park.

Here's two repeats that fall, Venn-diagram-like, into the overlap area between the "graded beds" theme and the "folds" theme:




Now for some fresh, never-before-seen images:







(that's a fold cut twice oblique to its axis, resulting in an elliptical outcrop pattern).

Tiny folds:


Folds in one direction (top to bottom); boudinage in the perpendicular direction (left to right):


Found this one on the side of a cliff I probably should not have been scaling:


That's all for now... have a good Tuesday!

Labels: igneous, maryland, metamorphism, national parks, piedmont, primary structures, structure

I mentioned seeing some cool stuff when I went hiking on the Billy Goat Trail last weekend.

One of the things that really caught my eye were multiple new exposures of graded bedding. These rocks began as deposits of sediment offshore from a volcanic island arc: they consist of turbidite deposits that were then squished and squeezed as that volcanic island arc collided with eastern North America during the closure of the Iapetus Ocean. As a result of this, they were metamorphosed and deformed. But in a few places, you can still see the relict graded beds that originated through the settling out of turbidity currents.

Here's some images:

I count four or five here:





A nice central fault zone displaced the central block downward:




This one is a little more subtle...


Here's one that's been turned upside down (by tectonics):


And there were also some folded examples:




A close-up of the hinge of this folded graded bed:


Pretty cool, eh? The only problem is these samples aren't on the Billy Goat Trail itself, which means I'll really never be able to show them to students except in photographs...

Labels: geology, maryland, metamorphism, national parks, piedmont, primary structures, sediment, structure

Ladies and gentlemen, spring has arrived in the Washington, DC region. It is sublime. I'm very grateful that it's my spring break this week because even though I still have a ton of work to do, I've had the opportunity to get outside every day and enjoy a bit of the weather.

This weekend, I got up early both days and headed out the the Billy Goat Trail, a rugged hiking trail along the Potomac River's gorge about 12 miles upstream from DC. I departed from the trail itself both days, which was great because it brought me to places I hadn't seen before. I found a lot of cool new structures and rocks! Over the next few days or weeks, I'll be sharing some of those images with you, but for today, I figured I'd show you some 'soft' imagery, just to celebrate the fun of being outside on a hike on a lovely day. ...and wearing short sleeves, no less!

Here's a shot of typical scenery along the Billy Goat Trail. This is looking upstream:



One of my side-trips off the trail... because the water level was pretty low, I was able to get to some islands that are often inaccessible. This is the channel between the Rocky Islands (downstream of Great Falls, upstream of Mather Gorge):



This land is all part of the C&O Canal National Historical Park. Here's a spot where rains from Tropical Storm Hanna breached the wall of the C&O Canal, allowing its water to drain downward into the Potomac. Because the canal's towpath was located there, the Park Service has constructed a temporary path which detours around the breach:



I saw some good birds on my hikes there. Red-tailed hawks, double-crested cormorants, Canada geese, mallards, belted kingfishers, pileated woodpeckers, red-bellied woodpeckers, tufted titmice, chickadees, robins, blue jays, and great blue herons. Also, both local species of vultures: the turkey vulture and the black vulture. This is a black vulture (note the black, not red, head):



Here's some tracks: theropod dinosaurs? ...or great blue heron? You be the judge:



Here's a cool fish skull I found:



Of course, it wasn't all scenery, birds, and fish. There were rocks, too. I took a lot of rock photos, and you'll get to see them all in due course... But for now, let me start you off with the tame stuff. Here's some cobbles I encountered along the hike...

Cobble of the Seneca Sandstone (Triassic arkose) showing a mudchip rip-up clast:



Tilting it a bit, you can see other mudchips too:



Cobble of cement containing Seneca chunks:



Cobbles of quartzite of the Antietam Formation showing Skolithos 'worm' tube trace fossils:



I love these Skolithos tubes. It's hard not to love them, and they're everywhere around here. Like the Seneca cobbles, they come from source areas to the west (Culpeper Basin & Blue Ridge, respectively), and were transported to the Maryland Piedmont by the ancestral Potomac River.



My favorite Skolithos-bearing quartzite cobble:



...And the same cobble, end-on:



More to come, tomorrow...

Labels: birdies, blue ridge, culpeper basin, fish, fossils, maryland, national parks, piedmont, sediment

Just got a batch of images from the NOVA photographer, Kevin Mattingly. I particularly like this image of last spring's Field Studies class at the Billy Goat Trail:

Here, we're overlooking the upstream end of Mather Gorge, checking out some ~360 Ma lamprophyre dikes exposed there -- but offset on either side of the river!

Labels: devonian, field trips, national parks, nova, piedmont, teaching

A bill working its way through the Senate right now, S-22, has some provisions you may be interested in. It's called the Omnibus Public Lands Management Act of 2009. Mainly, it sets aside a heckuva lot of wilderness areas. But the thing that brought it to my attention is that it sets aside some money to develop a "national geologic trail" focused on Glacial Lake Missoula, with an interpretive center to be located in Missoula, Montana. The Senate website describes it like this:

The Ice Age Floods National Geologic Trail Designation Act (S. 268 and H.R.
450), would create a trail to document the catastrophic flooding that stretched
across parts of Montana, Idaho, Oregon, and Washington during the last Ice Age.
The designation of an Ice Age Floods Trail follows the recommendations of a 2001
study headed by the National Park Service which found the area suitable for
addition into the National Park System.

This part of the bill carries a possible pricetag of $12 million, with $2 specifically for the visitor center. Though there's no way the trail would be done by this summer, Glacial Lake Missoula's geologic signatures will be some of the highlights planned for this summer's Regional Field Geology of the Northern Rockies class.

Read more about it in this article in the Missoulian.

Hat tip to Babak R. for letting me know about this.

Labels: glacial landforms, glaciation, lakes, montana, national parks, politics

The day before Inauguration, I decided to celebrate George Bush's last day in charge of my country by taking a walk in the woods. Okay... that wasn't really my motivation. I was just procrastinating writing up my Structural Geology labs for the coming semester. Anyhow, for one reason or another, I took a stroll in the woods.

I brought my rootin' tootin' new camera with me, and took a few photos. I've got four things to show you: (1) some differential weathering, (2) some kink banding, (3) some cool effects in frozen soil, and (4) a critter.

(1) To start, check out this close-up photo of a stone bridge where the Klingle Valley merges with the Rock Creek Valley:


Several of the (local) stones used in the bridge are weathering at a faster rate than the mortar (cement) that holds them together. As a result of this differential erosion, the less-stable rocks are recessed into the face of the bridge:



Here's another one, where you can see that not all minerals are equally stable at Earth surface conditions. The large central quartz augen stands out in high relief as the micaceous & feldspathic schist around it weathers away.



Yet another: recessed about an inch into the bridge:



That's not all I saw. I also re-discovered the location of some kink bands along the Rock Creek Park bike path:



These kink bands are similar to the ones that Spring 2008 Honors student Victoria measured and analyzed in Broad Branch (also in Rock Creek Park), but these ones are in a different location, further south in the park.



What's worth noting about these kink bands is that they overprint the regional foliation of these schistose rocks. In order to do that, the force that generated the foliation must have been coming from one direction (call it east-west), causing the mineral grains to line up at right-angles to that stress. That allignment is what we call foliation. Later, a new generation of deformation came in from a different direction (call it north-south, approximately parallel to the foliation), kinking the pre-existing foliation. For more on kink bands in DC, see my "DC rocks" page.



(4) One of the disadvantages to hiking in Rock Creek Park in the winter is that it's pretty monochromatic. One of the advantages is that with all the leaves off the trees, it's a lot easier to see new stuff. It's great woodpecker-watching weather, for instance. I saw five woodpeckers of two species that day. Also, it makes it a lot easier to see where the trails are. I saw a new trail that I had never walked before, and so I decided to check it out. I'm glad I did. One thing that I saw that is pretty cool is this effect in frozen soil:



When water freezes, it expands in volume by about 9%, and that shows up here as the upper layer of wet soil froze, it expanded in all directions, pulling away uniformly from two large cobbles of quartzite. It almost makes it look like the quartzite cobbles shrunk in their "sockets," but really it's the "sockets" that got larger.

(4) Lastly, I was doubly glad to have taken the new trail because it was a "road less travelled" kind of deal. I was the only one there. As I trod along, suddenly I heard a scampering noise. It was a critter! It ran up a little gully and then paused as still as a stump, looking at me:



Can't see it? Try this zoomed-in shot:



It's a red fox! Vulpes vulpes, one of two wild canids we have in Rock Creek Park. Pretty good sighting -- only the fourth time I've seen one here (and I spend a lot of time in this park). And every one of those times was in the winter. Again, it's having those clean leaf-less views that allows hikers to see stuff like this.

Labels: critters, dc, ice, mammals, national parks, structure, weathering

Students! What will you do next summer? I've done some work with the good folks at the Center for Urban Ecology in DC, which works with the national parks in the National Captial Region. I was notified today that they're in search of a GeoCorps participant to complete a paleontological inventory of the area's parks.

Could be fun! The relevant info is below, or you can see it all on the GeoCorps site.

Public Land Name:	Center for Urban Ecology, National Capital Region, National Park Service
Position Title:	Geosciences Research Assistant / Paleontologist
Position ID Number:	208
Location:	Washington, DC
Position Description:	The work of the GeoCorps participant will build upon a paleontological inventory of the National Capital Region’s parks conducted in 2004 which revealed remarkable assemblages containing vertebrate, invertebrate, and plant fossils distributed in four distinct physiographic regions. The participant will conduct paleontological resource site condition assessments, complete documentation, and help establish a monitoring program for fossil sites in the Chesapeake and Ohio Canal National Historic Park (MD, DC), Manassas National Battlefield (VA), and National Capital Parks-East (MD, DC). The position will include both office and field work. Most of the time will be spent conducting field paleontological surveys to fully document localities and to undertake site condition assessments. Site visits will be conducted by vehicle and on foot. While working in the field, the participant will ensure that NPS regulations and safety procedures are being followed. Office duties will include reviewing literature, preparing documentation for entering into NPS databases, building a photographic library, and drafting recommendations for site monitoring. Participants may have an option to use a portion of their time for self-directed research after approval from regional and park staff. Prior to starting this position a government security background clearance will be required. This position is offered through the Geological Society of America's GeoCorps America Program in partnership with the National Park Service's Geoscientists-in-the-Parks Program.
Qualifications:	Undergraduate/graduate coursework and/or field experience in paleontology, with preference given to knowledge of the Mid-Atlantic region. Applicant must have completed at least three years of college-level coursework. Graduates students, faculty, and active and retired professionals are also welcome to apply. Experience in the field, discovery and evaluation of paleontological resources, particularly trace fossils, is important. The applicant should be able to work well independently, both in the office and in the field, have basic map reading and GPS skills, and must be comfortable both working outdoors and negotiating a busy city. Basic computer skills are required. Applicant must have a valid driver’s license and a good driving record.
Position Dates:	12 weeks with flexible starting dates in April-May
Payment:	$2,750.00
Housing Available:	Housing will be provided at no cost to the participant most likely at Brookmont House (George Washington Memorial Parkway) in Washington, D.C. This is a 3-bedroom house shared with up to two other people. There is public transportation available but grocery shopping and other services are limited in this area, so having a personal vehicle is highly recommended.
Physical/Natural Environment:	Parks of the National Capital Region (NCR) encompass numerous sites ranging in size from less than one to over six thousand hectares that provide a diversity of experiences and landscapes. The 15 national parks of the National Capital Region lie within four physiographic provinces: Coastal Plain, Piedmont, Blue Ridge, and Ridge and Valley, and contain significant geological resources. These parks include areas with national icons (the National Mall), national battlefields (Antietam, Manassas, Monocacy, Harpers Ferry), and natural forests (Catoctin Mountain Park and Prince William Forest Park), all amidst the rapidly growing metropolitan Washington, D.C. This unique setting provides great opportunities to gain insights into issues related to urban ecology and integrated management of cultural and natural resources.
Work Environment:	The Center for Urban Ecology (CUE) houses the Natural Resources and Science Division, which is an interdisciplinary team that provides scientific guidance, technical assistance, and education for the preservation and enhancement of park resources in the National Capital Region, National Park Service. Working with resource managers, researchers, and the public, CUE strives to discover and incorporate new ways to understand, preserve, and enhance natural communities within and around the national parks in the metropolitan Washington, D.C. area. CUE is located in the Georgetown area of Washington, DC, in a Rock Creek Park facility. Laboratories at CUE are fully equipped to support research in botany, plant health (pathology), entomology, hydrology, aquatic biology, soils, and wildlife biology.
# of current Applicants:	0

If you have questions about the application and selection process, please contact Anny Jones. If you have questions about any aspect of the position - description, qualifications, housing, dates - please contact the primary or secondary contact below:
PRIMARY CONTACT INFORMATION Contact Name: Giselle Mora-Bourgeois Title: Science Education Coordinator Address: 4598 MacArthur Blvd, NW City/State/Zip: Washington, DC 20007 Phone: 202-342-1443 Ext 220 Email: Giselle_Mora-Bourgeois@nps.gov Website: http://www.nps.gov/cue/	SECONDARY CONTACT INFORMATION Contact Name: Vincent L. Santucci Title: Chief Ranger Address: George Washington Memorial Parkway Turkey Run Park City/State/Zip: McLean, VA 22101 Phone: (703) 289-2531 Email: vincent_santucci@nps.gov Website: http://www.nps.gov/gwmp/

Labels: dc, fossils, jobs, national parks

Contrary to what you may have heard, it's not all basalt. Even the basalt is astonishingly varied: the extrusive rock of a thousand faces... Here I'll share some pictures I took of rocks in Hawai'i:

There's pahoehoe:


...and there's a'a:


Here's a pahoehoe flow oozing over my boot (just kidding; it was cold when I did this):


Pahoehoe lobes can drain out, leaving only the outer skin as rock, but with a hollow center. These are lava tubes (nickel for scale):


Another one (nickel for scale):


Cool texture on the inside of this lava tube (nickel for scale):

...and zooming in a bit closer (it looks like wrinkled cellophane!):


A stack of cross-sectioned pahoehoe flows, showing their tubular (totally tubular, dude) shape:


Some Hawai'i basalt is massive, like this cobble...


...or like this cobble of hawaiite, a dense form of basalt found atop Mauna Kea (where it apparently erupted beneath Pleistocene ice caps):


But the majority of Hawai'i's basalts are vesicular, meaning they contain "Swiss Cheese" type holes that result from gas bubbles. When the lava erupts, it experiences less pressure at the Earth's surface than it was subjected to at depth. As a result, many gases (steam, CO2, sulfur dioxide, chlorine, argon, others) exsolve from the lava solution and make bubbles. If these bubbles don't get a chance to pop before the lava sets up into igneous rock, then they are preserved as vesicles. Sometimes the vesicles are small:


...and sometimes they are big:


Sometimes, they are really big. Here's one I could fit my entire Nalgene water bottle into:


When vesicles later get filled in with mineral deposits, we call them amygdules. Here's some vesicles that have gotten a light coat of a white mineral on their interiors: the first step to converting a vesicle into an amygdule:


Some of the vesicles show strain (almost certainly due to late-stage flow in the increasingly-viscous lava, getting stretched out like air bubbles in pouring honey). Surface tension on the bubble wants to make it spherical, and the lower the lava's viscosity, the easier it will be to attain that perfect spherical shape, minimizing the surface-area-to-volume ratio. So when we find them in cigar-shapes or pancake-shapes instead, that's a clue that they've been deformed. Deformed not by tectonic forces (ductile flow at depth in an orogen), but ductile flow as a result of their formation, in a sluggishly oozing blob of lava:


Another example of stretched-out vesicles:


A lonely vesicle in an otherwise massive basalt:


Not sure what's going on here, but it looks cool (popped vesicles in sticky lava?):


Another thing you see a lot of in these Hawai'ian basalts are phenocrysts of certain minerals. Here, for instance, is a cobble showing nice olivine phenocrysts:


...and another:


Here's one I showed you last week when we discussed Green Sands Beach:


Here's an outcrop which shows phenocrysts of plagioclase feldspar instead:


And a river cobble (also vesicular) bearing a healthy population of feldspar phenocrysts:


Holy feldspar, Batman! This rock has a huge proportion of feldspars (you'll note that it's still vesicular, though: in spite of the overwhelming volume of macroscopic crystals, this is still an extrusive rock):


Here's something else caught up in a finer grained (and yes, vesicular) basaltic matrix: another piece of basalt!

This is a xenolith of slightly-older basalt showing flow banding in its own trains of vesicles, that after solidification got broken off and included in younger flows of basalt. I'll post some additional xenolith photos later this week.

It's not all basalt, though. Here's a breccia made of basaltic cobbles (penny for scale):


And a closer shot of the same outcrop (penny for scale):


Finally, a rock I was surprised to see: an intermediate-composition extrusive igneous rock called benmoreite (nickel for scale, and note the rock hammer impact marks):


Benmoreite is way more felsic that anything else on the island. According to my volcanic advisor Jess, it's the result of late-stage partial melting of basaltic source rocks in the island's oldest volcano, Kohala. In other words, it's a distillation of basalt: concentrating the most felsic components in this decidedly-lighter-complected rock (nickel for scale):

Labels: basalt, geology, hawaii, igneous, national parks, pleistocene, primary structures, volcano, xenoliths

I had planned to write about vog next week, but NASA's Earth Observatory has forced my hand this morning by publishing this:

What you see in this image of the Hawaiian islands is a lot of vog, an acrid mix of sulfur dioxide, water, and oxygen that results when volcanic emissions mix with the atmosphere.

When I was there last week, I experienced some vog, starting with the source. Here's Halema'uma'u Crater (part of Kilauea Caldera), steaming away in Hawai'i Volcanoes National Park, spewing water vapor, carbon dioxide, sulfur dioxide, and other gaseous goodies upward and downwind:

The prevailing winds keep these nasty gases close to the ground west of the crater, resulting in the park service closing down the roads in that area of the park.

From there, the gases drift west and north, mixing and interacting with the atmosphere, forming vog. If the trade winds aren't active, the vog kind of stalls on the western side of the big island, and even drifts along the archipelago to plague Maui and the other islands.

On Thanksgiving day, I was standing on top of Mauna Kea, one of the five volcanoes that makes up the island, and on the descent back down the mountain, looking south towards Mauna Loa, where I could see a curtain of vog on the western flank of the big mountain (obscuring Kona and the coast):


Now here's a zoomed-in shot, augmented with a dotted line to show you approximately where the silhouette of Mauna Loa would be, if you could see it through all the vog there on the western side of the mountain. Honestly, it looked just like a curtain of greyish white hanging from the sky: palpable and with a discrete edge:


Down in the thick of it:


It wasn't as noxious as I thought to be in it and breathe it, but the vog definitely had a distinct scent and taste, and my eyes were watery (though that may have been psychosomatic, because it was kind of freaky how thick it was).

According to my friend Lily in Waimea, the trade winds have picked up in the past day or so, though, and scrubbed away the vog. So: clear skies return to Hawai'i... but for how long?

Labels: clouds, geology, hawaii, national parks, travel, volcano

Here's a quick recap of my cross-country journey, for those who are interested in such things.

I left Bozeman on Saturday morning, July 26, and drove east on the Interstate to Billings, then diverged southeast towards Little Bighorn. There, I verified a comment from a Lakota friend at MSU that with my new bushy mustache (see change in icon above), I look a wee big like George Armstrong Custer (Custer & his men were killed by Lakota and/or Cheyenne warriors). After a short picnic there, I kept driving across southeast Montana, and into northeast Wyoming. My goal for the night was Devils Tower, where I have positive memories from my "North by Northwesty" roadtrip two years ago. I got to Devils Tower in mid-afternoon, just in time for a wicked-looking thunderstorm to roll in. Pendulous looking mammatus clouds were hanging down, and the skies turned a darker grey than Lola. Rain and wind came through, and a big dead branch from one of the cottonwoods in the campground came crashing down, but not on anyone's car or tent. When the skies cleared up, I drove up to the visitor's center and took a walk around the tower. It's awesome: massive columns, some of them twenty feet across. The rock is a porphyritic phonolite, and it's quite pretty to look at: big feldspars (5mm) set in a fine-grained grey matrix. Lovely.

The next morning (Sunday), I headed for Red Bird, Wyoming (along Wyoming's eastern border), where Cruisin' the Fossil Freeway suggested there would be oodles of ammonites in concretions in the Pierre Shale, some a foot across. When I visited the Denver Museum of Nature and Science earlier this summer, Kirk Johnson reiterated to me that Red Bird was the place to go for ammonites. But once I got to where Red Bird should be (according to my road atlas), there were no highway signs indicating that the town existed. Worse, there were no outcrops, and no sign of public land. (And one thing that an amateur fossil collector does not want to do in Wyoming is trespass on a rancher's land.) So, no Red Bird ammonites for me. Oh well, no worries: I had collected ammonites from a tongue of the Pierre Shale (the Bearpaw Shale) earlier in the summer on BLM land near Glendive, Montana, and scored some good specimens there. I cruised south, stopping at the Sierra Trading Post outlet in Cheyenne, Wyoming, and dropping some cash on some new duds (STP is mainly a catalog business, famous ten years ago for their amazing deals, but the company seems to be shifting to more mainstream business nowadays, including multiple brick-and-mortar locations). Then another hour on the road brought me to Fort Collins, to the house of Larry Wiseman, where I stayed earlier in my trip. He and I got some pizza and 90-Shilling Ale (Odell's) and traded tales about our summers.


The next morning, we had coffee on Larry's front porch and watch the sun rise. I packed up and hit the road, heading for Kansas. In my rear-view mirror, the Rockies shrank and vanished from sight, a melancholy fade. Out into the plains... In mid-afternoon, I rolled into Oakley, Kansas, where I headed for the Fick Museum. The Fick Museum is interesting on multiple levels: it's got some stellar fossils from Kansas's Smoky Hill Chalk (member of the Niobrara Formation), like a Xiphactinus (massive fish) and a Tylosaurus skull (even more massive mosasaur). But it's also got some whacked-out art: the founder, Vi Fick, was into making art with local "art supplies," and so the walls show his portraits of eagles rendered entirely in rattlesnake tails (see image at right, from this online gallery), or his geometric arrangements of thousands of fossil shark teeth. There's even an oil painting Fick did of "God making the Cretaceous seas," which shows a bearded diety surrounded by flames (it kind of reminded me of Hindu art) making pleisiosaurs and pterosaurs. Not the usual way you see fossils displayed, or paleontology depicted!

At the Fick Museum, I met up with Ron Schott, doyen of the geoblogosphere, who graciously agreed to show me some cool Kansas geology. Ron and I headed south from Oakley towards Monument Rocks, an outcrop of the Smoky Hill Chalk. Ron was eager to gigapan the outcrop, and he set up the little device: essentially a robot that directs his camera to take high-resolution photos in a systematic grid. Pretty cool, really -- I guess I hadn't realized what a Gigapan really was before seeing it in action. I got to meet Ron's two little plastic elves that he uses for scale, and personally placed them on a ledge of chalk for the photograph. The grid of pictures eventually gets digitally stitched together by software, and available for sharing online.

From there, Ron and I headed back up to Oakley, stopping en route so I could collect a couple samples of the aquiferiferous Ogallala Formation, and then headed east, then south again, towards Castle Rock, another chalk outcrop. Here, we tested out my Prius' shocks on the dirt tracks, and checked out the largest cliff in Kansas (nearly getting blown off it by the intense wind), and then prospected for fossils below. I found some fish scales, and a shark tooth! Also inoceramid clam fragments, encrusted with oysters (apparently a common feature of the bottom of the Western Interior Seaway). No mosasaurs, though... Back to the road, and into Hays, Kansas, where Ron put me up in his guest room. We had dinner and a few beers at the Lb. Brewing Company, and thought about recording a PodClast, but then it slipped our minds. We discussed field trips, tenure, publications, and related topics. A good time! Thanks again to Ron for being such an excellent host.

The next two days (Tuesday and Wednesday) were essentially just driving. On Tuesday, I made it to Indianapolis, Indiana, and spent the night in a hotel there. On Wednesday, I turned north, and drove up into Michigan, and crossed into Ontario at Port Huron / Sarnia. Why go to Canada on my way from Montana to DC? Well, I'm teaching my Snowball Earth class this week at NOVA, and some of the rock samples I needed were stuck at Brock University in St. Catherines, Ontario. Usually they get shipped to educators who want to use them, but because of alleged border complications, I had to go get them myself; a five hundred mile detour! Fortunately, I have good friends who leave in Waterloo, Ontario, so I went and stayed with them. Mike and Natalie Leuty have been friends since 1996, and we had a good evening catching up. They have a sweet house in a suburb full of professorial types who teach at one of the several universities in town.

On Thursday morning, Mike and I had coffee on his front porch while his kids played in the yard, and then I packed up my kit and got rolling. I made it to Brock by 11am, and got the Snowball Suite. Because it's in a giant black case that looks suspiciously like a rifle case, I packed it under a pile of other gear in my car. At any rate, I crossed back into the United States without any static from customs officials, and rolled through Buffalo, New York (twice in one year!) I made my destination for the night Ithaca, New York, where I have a friend who's going to grad school at Cornell. I've never been to Ithaca, but I hear that it's "gorges" from many people. So I called my friend, Kathryn Werntz, and she was indeed around and accepting visitors, so I drove through the finger lakes region (five subparallel glacial troughs now filled with water), and found my way to her bungalow. Kathryn and I took a walk through Cornell's campus (two amazing gorges cutting through it), had some Indian food, and went to get dessert at Purity Ice Cream.

In the morning (Friday), I got up and we went to Gimme! Coffee for some caffeine. Thus fortified, I hit the road for my final day of driving. East to I-81, then south through Pennsylvania. At Harrisburg, I turned onto I-83, which took me to Baltimore, and from there it was a familiar zoom down the B-W Parkway into northeast DC. The dome of the Captiol was visible to my left, and then the comfortable sights of Florida Avenue and U Street. Up the hill, and a left on Harvard Street, and I was back in Adams-Morgan. Home! Finally!

Labels: appalachians, canada, chalk, colorado, field trips, glacial landforms, kansas, montana, national parks, new york, snowball earth, structure, travel, wyoming

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!

Labels: critters, fossils, msse, national parks, yellowstone

After I got off the river at the Grand Canyon, I drove to Moab, Utah, where I have a friend from my days working outdoor education in southern California. Pete and I went swimming in Mill Creek (water + slickrock = awesome plunge pools) and checked out the sunset from the top of a dome of the Navajo Sandstone north of town. We had dinner at the Moab Brewing Company, which was delicious. The next morning, I checked my e-mail and got an oil change, then went up to Arches National Park to pay homage to Edward Abbey by taking a hike to Delicate Arch. They even have a small exhibit in the visitor center about Cactus Ed -- a nice acknowledgment on the part of the park that his book Desert Solitaire piqued interest in the park for many people.

After my hike, I got back in the car, and headed north to the interstate, then east into Colorado. Past Grand Junction and Delta, to the little town of Montrose, where I got final supplies for a couple of days in Black Canyon of the Gunnison National Park. I pulled in relatively late in the day, so just settled into the campsite. It felt good to be camping at high elevation, with cool temperatures, again. The next day, however, July 4th, I spent in exploring the park. I was surprised to learn that there is no trail down to the bottom of the canyon from the rim, but they do let people descend via "the Gunnison Route," a steep-ass ditch full of loose scree and talus. It was pretty sketchy, and pretty exhausting: not much fun. I kept thinking "there has to be a better way to do this." The reward was at the bottom, where the Gunnison River runs cool and fast. The Gunnison has carved an incredible gorge here: steep, deep, and with a steep river profile. It's a classic case of steam superposition over a buried Laramide uplift. During the recent episode of uplift, the Gunnison cut down through overlying sedimentary strata (including the Entrada Formation's pink sandstone, visible on the north rim) and into the underlying Mazatzal-aged (~1.7 Ga) igneous and metamorphic complex. This resistant rock is what makes up most of the canyon. It looks a lot like the Grand Canyon's inner gorge, with pink ribbons of granite leaping through the amphibolite-grade metamorphics. Anyhow, the river was very refreshing. I rested there for a while, and ate some lunch (tortillas from nearby Olathe, Colorado, wrapped around mozzarella and turkey pepperoni.) The hike back up was a big slog, and about as enjoyable as the hike down ("There has to be a better way of doing this!") Up top, I drove the road along the south rim, admiring the various viewpoints into the chasm and taking small hikes.

The following morning, I packed up camp early, and drove all day. I went west back to Grand Junction, and took a cool little road (Route 139) north over Thompson Pass and through some cool BLM land, replete with pictographs. I got some GREAT gas mileage after Thompson Pass, basically crusing downhill at 100 m.p.g. for over an hour. Awesome! Then through Dinosaur, into Vernal, Utah, and then into Wyoming at Flaming Gorge.

At Rock Springs, Wyoming, I went north on 191, through Pinedale (nearby Fremont Lake is the type location for Pinedale Till, the Rocky Mountain version of the Wisconsin Glaciation), and up to Jackson. Man, Jackson's a tourist trap! Yikes! Not as bad as Vegas, but I definitely didn't linger with the sunburnt hordes there. I had a date with the Gros Ventre landslide. Just northeast of Kelly, Wyoming, this is a classic location in the study of mass wasting events. I camped on the lake created by the 1925 landslide, and spent the next morning photographing the scar and debris pile which dammed the Gros Ventre River. Unlike the Madison River's landslide and resulting "quake lake," no one was killed with the initial earth movement at Gros Ventre, but when the dam failed two years later, the resulting flood drowned six people in Kelly. I first learned about the Gros Ventre slide as an undergraduate, and I teach about it today, so it was a real pleasure to see it firsthand.

Next morning, a ho-hum commute through Grand Teton and Yellowstone National Parks and up into Bozeman.

Labels: colorado, montana, national parks, travel, utah, wyoming

I left Bozeman on Saturday morning, and drove for about seven hours. I headed south through Ennis, Montana, along the western side of the Madison Range, passing by the Madison Earthquake Site landslide (from the 1959 Hebgen Lake earthquake), and then south into Idaho. I went through Island Park, Idaho, site of the caldera of one of the three big recent eruptions of the Yellowstone volcanic center. Then into northern Utah, where I got a glimpse of the Great Salt Lake. I headed up into the Wasatch Range to spend the night, just east (and several thousand feet above) Ogden, Utah. I did some birding on the reservoir there, observing the mating rituals of both the woodcock (amazing humming noise produced during flying dives) and the western grebe (neck bobbing following by synchrnonous running across the water).

The next morning, I headed west from there, into the basin, across a range, into another basin, across another range -- you get the idea. I initially intended to go hunt for trilobite fossils in the Wheeler Shale in the House Range, but the 20-mile dirt road rattled me (quite literally) and I turned around after only four miles. I got spooked: what would happen to me if the Prius broke down out here? It's really quite desolate country. I've only ever had that feeling once before, when my Dad and I drove across the Namib Desert. It's a mix of agoraphobia and anxiety over feeling inept at repairing mechanical things, like Prii and other automobiles. I chickened out -- no trilobites for me. But there was a consolation in Great Basin National Park, which was where I headed that afternoon. I did a short hike there in the Snake Range, and toured Lehman Caverns there (my third guided cave tour in two weeks!). I had my best campsite of the trip at Great Basin: montane forest, with a gurgling stream running fifteen feet from my tent. Lovely.

When I woke up, I packed up the car and coasted downhill for eight miles into the town of Baker, Nevada, where I had a great breakfast and coffee at a little cafe there. Then up and over the Snake Range, and down the next valley to the west, south for 93 miles of some of the most empty country I've ever seen in America. In an hour and a half of driving, I saw only 20 vehicles. I crossed back into Utah, and then made my way south to the edge of the Colorado Plateau, and drove up into Zion National Park. Zion is a great canyon cut into a series of sedimentary rocks. The last time I was here, 13 years ago, I walked up the Narrows, and my first order of business was to repeat that hike. There's a new shuttle system in the park now, so after parking at my campsite, I hopped on a shuttle into the park and rode it to the end. I waded into the Virgin River and shuffled upstream. In the Narrows, the Virgin River has cut down through the Navajo Sandstone, but not quite down into the weaker underlying Kayenta Formation, and so the canyon is deep but narrow. (Downstream, when it gets deep enough to tap into the Kayenta, it undermines the sandstone cliffs, and the valley widens.) "Hiking" here is one of the more unique outdoor experiences I've had. Being immersed in the cool river, surrounded by towering rock walls -- it's magical. The further upriver you hike, the less people there are, and it's like a cathedral. I went up and around several entrenched meanders, and marvelled at the alcoves, cross-bedding, and variety of cobbles in the riverbed.

Today, I'm staying in the park and heading up to Angel's Landing, a legendary hike in its own right. Tomorrow morning, bright and early, I'm off to Las Vegas to pick up my Dad and brothers for our Grand Canyon rafting trip. Not sure if I'll be able to post again until after I get out.... late next week.

Labels: birdies, fossils, grand canyon, idaho, montana, national parks, stratigraphy, travel, utah

On Saturday, I was due to take my Audubon class to the Billy Goat Trail. But, since we had so much rain earlier in the week, the Potomac was running higher than normal, and parts of the trail were flooded, so the Park Service closed it. I was ticked off that I couldn't take my students even on the non-flooded portions of the trail to show them pre-Taconian relict graded beds or Acadian lamprophyre dikes. But the NPS are sticklers for the rules, and there was one hyperenthusiastic volunteer standing guard to make sure we didn't venture onto the trail. So we didn't.

We walked another trail, the Berma Road, instead, which parallels the Washington Aqueduct from Great Falls down to the Old Anglers Inn. Along the way we saw plenty of metagraywacke, migmatite, and granite intrusions. Here's me pretending to 'hold up' up a massive metagraywacke xenolith in the Bear Island Granite:

We also saw a lot of structure, including boudinage, folds, and faults. While we didn't get to see some of the more striking features of the Billy Goat Trail proper, we made it work okay. And everybody in the class had a great sense of humor in regards to being kept off the BGT itself.

I thought this was a funny form of political protest:

Both photos by Audubon student Paula. Thanks, Paula!

Labels: granite, national parks, plutons, politics

This weekend, I took a backpacking trip in Shenandoah National Park. Thought I would share a few photos today: scenery first, geology second...

Here's the view looking east from Skyline Drive:


The temperature difference due to elevation was striking. It was still early spring up on the top of the mountains, on Skyline Drive:


...But down below, it was green and lush (and sodden with pollen!):


I camped out for two nights near Corbin Cabin, and did a day-hike around Thorofare Mountain on Saturday, visiting this waterfall at lunchtime:


The geology of Shenandoah National Park is interesting: it records the assembly of the early supercontinent Rodinia at about a billion years ago, and then the breakup of Rodinia about 600 million years ago. The first event recorded is the generation of granite gneisses and granites due to the Grenville Orogeny. The oldest unit in the park is the 1.1 Ga Pedlar Formation, a granite gneiss. There's a slightly younger granite which intrudes it called the Old Rag Granite (~1.0 Ga), but I didn't see any outcrops (or float blocks) of it, so I'll not mention it further. There's a thin, patchy sedimentary cover called the Swift Run Formation deposited directly atop the granite gneiss and granite, providing a nonconformity surface. Atop that is a series of volumnious tholeiitic basalt flows: these mafic extrusions record the breakup of Rodinia and the opening of a new ocean basin: the Iapetus. In many places in the park, you can see "feeder dikes" of the Catoctin cutting through the older plutonic and metaplutonic rocks (see image below). There are also some sedimentary rocks layered atop the Catoctin (the Chilhowee Group), recording the transgression of the Sauk Sea on the North American platform. But I didn't encounter any good outcrops (or float blocks) of them on this trip, so I'll stick to the tectonic story: the Pedlar Formation shows us Rodinia getting put together, and the Catoctin Formation shows us Rodinia breaking apart. Later metamorphism due to Appalachian mountain-building resulted in changes in both of these rocks (development of "blue quartz" in the Pedlar, and the Catoctin metamorphosed to greenstone).

Here's a massive dike (possibly a "feeder dike" feeding surface lava flows) of the Catoctin basalt cutting through the Pedlar Formation granite gneiss, just north of the Marys Rock Tunnel. Note the columnar jointing extending perpendicular to the walls of the dike:


Having covered all that, I now propose to spend the rest of this blog post showing you the variety of cobbles and boulders in my campsite. I camped at the little wedge of land above the confluence of two streams. One stream's catchment basin was Catoctin, and the other drained outcrops of Pedlar. As a result, the "float" in my camp was all either Pedlar Formation or Catoctin Formation. I'll just run through them one after another so you get a sense of the range of variety in each formation.

You'll notice that the Pedlar is sometimes coarse, sometimes fine, sometimes well foliated, sometimes not so much. You'll also notice that the Catoctin varies a lot in terms of its extrusive texture: sometimes aphanitic (fine-grained), sometimes amygdular (formerly vesicular), sometimes it even runs to volcanic breccia. All of these original lithologies have been metamorphosed to various degrees in the Catoctin, which here can be seen by comparing the amount of green in the rock. This green comes from two metamorphic minerals: chlorite and epidote. Enjoy!

Pedlar Formation:



















Catoctin Formation:

Labels: appalachians, basalt, blue ridge, granite, iapetus, metamorphism, national parks, primary structures, proterozoic, shenandoah, virginia

An interesting piece on NPR discusses how joshua trees (Yucca brevifolia) will react to climate change. It revealed a fact I had not previously recognized: that during the Pleistocene, joshua trees habitat expanded thanks to the digestive efforts of the Shasta ground sloth (Nothrotheriops shastensis). Sloth dung deposits are full of j-tree nuts, and since the sloths expired 13,000 years ago, the trees haven't been able to move as far or as fast. Half of their current habitat in California and Nevada may be too hot and too dry within the next 50 to 100 years. The graphic above is from NPR, which produced the story as part of their "Climate Connections" series.

Labels: california, fossils, global warming, national parks