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

(Parts 1, 2, 3, 4, 5, & 6 of this series...)

Today's episode: The route down the mountain, and the long way back to camp.

After our "summit" of the arete between Hanging Canyon and Cascade Canyon, we begin carefully picking our way back downhill, switching between talus piles and snowfields, and back again:




We popped over the threshold, and started dropping down towards Jackson Hole. As the sun was dropping lower and lower in the sky to the west, we were pretty much in shadow from here on down... but the light still lingered on the highest peaks, like Teewinot Mountain, Mount Owen, and the Grand Teton itself:


By the time we got all the way back down to Jenny Lake, the sun was pretty much gone. However, it was illuminating a tall cloud north of us, sitting atop the Yellowstone area. We joked that this was the big one: Yellowstone had finally blown up and the orange color we were seeing wasn't "alpenglow" but incandescence from the long-awaited eruption of the Yellowstone volcanic center...


It wasn't, though. Just a little jest to take our minds off the fact that we had missed the last ferry across Jenny Lake, and so that meant adding an additional "2" (it sure felt more like 3) miles to our hike. As darkness closed in, we hoofed it along (only Pete had been prepared enough to bring a headlamp). For me, a highlight of this long slog came when Joel and I spotted an animal I'd heard of but never actually seen before: a pika! They are very, very cute animals that live in talus piles and make little squeaky noises. But they're quite elusive, at least in my experience. I've seen plenty of marmots and other alpine rodents, but this was my first Ewok pika.

We eventually got back to the vehicle and rolled back to camp, getting there about 10pm. We wolfed down some dinner, quenched our thirst, and sacked out. What a great day! In spite of being dog tired, I felt mentally rejuvenated and ready to take on the second half of the Rockies trip.

This post concludes the Hanging Canyon series. Thanks for coming along!

Labels: mammals, nova, travel, volcano, wyoming, yellowstone

(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

Another in the photo/sketch series...

This is an outcrop I saw in the Teton range (Wyoming) this summer. It's a nice example of relative dating, I think...

Labels: art, geologic time, structure, wyoming

by Anastashia Cuddihy*

Eleven miles south of Mammoth Hot Springs, and at the northern end of Beaver Lake in Yellowstone National Park, lies a geological wonder¹: Obsidian Cliff. Although it is only half a mile long, it has been a source of confusion and contentious debate for years.

Map of the Obsidian Cliff area (Google Maps):


Obsidian Cliff was formed when a rhyolitic lava flow traveled down the plateau and formed the 200 foot cliff. What is so unusual about the cliff is that obsidian is characterized by being a quickly cooled glass; the quick cooling prevents any crystals from forming, leading to a glassy rock. However, the bulk of the obsidian found at Obsidian Cliff is just that - a tall cliff made of obsidian - and it is far too massive to have cooled quickly enough to form obsidian in the 'traditional' way. Since there is no possibility that this amount of obsidian was cooled quickly, geologists theorize that the rhyolitic magma that formed the cliff had an extremely low water content, which would have hindered the formation of crystals. A feature found at the cliff that is associated with relatively slow cooling is columnar jointing. Columnar jointing occurs when lava shrinks during the cooling process, forming cracks, and it contracts to form 6-sided columns¹. Without the formation of crystals, the magma would have cooled to become the obsidian found in the cliff.

Columnar jointing at Obsidian Cliff:⁴


Another solution offered is that the lava could have come in contact with a large body of ice, such as a glacier¹. Upon contact with the glacier, the lava would have been able to cool rapidly and form the obsidian, although probably only at the contact margin. However the low-water-content explanation is the more widely accepted. Underlying the obsidian is a purplish-gray rhyolite, which is visible along the cliff face². Upon close examination of the obsidian, one can see the swirls left in it by the lava before it cooled¹.

Flow-banding in Obsidian Cliff obsidian:⁴

(also note the spherulites)

While Obsidian Cliff is not the only place in the park to find obsidian, it is most abundant at that site. Obsidian can also be found at locations called Tanker Curve and Cougar Creek.²

Obsidian Cliff is known for more than just being an anomaly in the formation of obsidian. Obsidian was prized by Native Americans for making tools, and there was no place better to find obsidian for these tools than Obsidian Cliff. Since obsidian fractures conchoidally and has sharp edges when fractured, it was best used in arrowheads and spears and blades for hunting¹. Scientists can use the chemical composition of obsidian (such as the concentrations of trace elements like rubidium and zirconium; See figure) to trace it to its source.

Scatterplot of zirconium (Zr) plotted versus rubidium (Rb) for 143 samples of artifact-quality obsidian collected in Yellowstone National Park.²


Archaeologists have concluded that obsidian from the cliff was being used as far back as 10,000 years ago, up until the arrival of Europeans in the area in the 1800's, when explorers found the Shoshone tribe using obsidian-tipped arrows³. Obsidan from the cliff has been found as far away as the midwestern United States, and it is inferred to have arrived there through the extensive Native American trade routes, where the high-quality obsidian would have been highly valued.

Obsidian Cliff is obviously an important site, both for American heritage and science. It gives us a wonderful idea of how the volcanic structures of the park work and how varied volcanic effects across the park can be. It is not suprising that a park with such a varied and explosive geological history would be home to such an intriguing structure.

__________________________________________________
* Rockies course 2009 student

1. http://www.nps.gov/yell/planyourvisit/upload/Yell250.pdf
2. http://www.obsidianlab.com/research/research_yellowstone.html
3. http://wyoshpo.state.wy.us/aamonth/2000.asp
4. Photo by Charlie Corrick.

Labels: volcano, wyoming, yellowstone

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

All photos in this post by Rockies student Charlie Corrick.

Talking S-folds, vergence, and Pumpelly's Rule in the Bridger Range:


Hiking uphill and down-sequence in the Bridger Range:


Describing the Kootenai Formation:


Jared gets eaten by Big Mike:


Joel with a few columns of basalt:


Post-M.O.R.-tour, with the guide:


Victoria and a Triceratops horn:


Group at M.O.R., with Tyrannosaurus for scale:


Calcified bat, Lewis & Clark Caverns:


Inside the cave:


Beartooth Plateau:


Amanda enjoys the view:


Camp at Pebble Creek in Yellowstone:


Watching for wolves, Yellowstone:


Bison:


Obsidian at Obsidian Cliff:


Longhorned beetle that landed on our geologic map of Yellowstone:


More to come...

Labels: arthropods, dinosaurs, fossils, glacial landforms, mammals, montana, wyoming, yellowstone

Working through my backlog of e-mails, I find that I have a few more Rockies course final projects to share with the world:

Laurie's website on Yellowstone geothermal features.

Jared explores Ringing Rocks.

Kevin suggests "more study is needed."

Ken discusses Grinnell Glacier:

Amanda reviews the Tetons:

Labels: glacial landforms, glaciation, montana, mountains, stromatolites, volcano, water resources, wyoming

Following on this morning's video from Jason, here are a few more Rockies class final projects:

Ringing Rocks (Bob)
Lewis & Clark Caverns (Charlie)
Gros Ventre Landslide (Chris)

Labels: montana, nova, teaching, websites, wyoming

These days, I'm busy getting things organized for my upcoming Regional Field Geology of the Northern Rockies class -- held next month in Montana and Wyoming. I'm taking the students to two new places that I've never been before, and so a lot of my prep time is learning more about those sites. One is Specimen Ridge in Yellowstone, where there are some petrified trees.

In researching Specimen Ridge, I came across the photos of thorton_3041, who posted an album of images online at Webshots. Look at this beautiful detail!



You can see the tree's rings in gorgeous detail, as well as the silica which filled in a rip (a dessication crack perhaps) in amorphous white, unconstrained by cell walls. My favorite is that little chunk of wood at the bottom, rotating into the void space like a xenolith stoping into a pluton. Check out Thorton's full album! I can't wait to see these trees myself this summer!

Labels: fossils, plants, wyoming, yellowstone

Started by Lockwood, perpetuated by Silver Fox... [UPDATE: Geology Happens, Geotripper, Hypocentre & Phreatic Ramblings have chimed in, too. The latter even posted about a huge paleofalls...] As per the geoblogospheric standard, the idea is to bold the ones you've been to.

#10 Lower Calf Creek Falls, Escalante National Monument, Utah
#9 Lower Falls of the Yellowstone River, Yellowstone National Park, Wyoming
#8 Upper Whitewater Falls, in southwestern North Carolina
#7 Snoqualmie Falls, between Snoqualmie and Fall City, Washington
#6 Havasu Falls, Supai Village, Havasupai Indian Reservation, Grand Canyon, Arizona
#5 Shoshone Falls, Twin Falls, Idaho
#4 Multnomah Falls, Columbia River Gorge, Oregon
#3 Bridalveil Falls, Yosemite National Park, California
#2 McWay Falls in Julia Pfeiffer Burns State Park, Big Sur, California
#1 Niagara Falls, Niagara, New York

Bonus Waterfall #1 [via Lockwood]: Salt Creek Falls, Oregon
Bonus Waterfall #2 [via Silver Fox]: Palouse Falls, eastern Washington
Bonus Waterfall #3 [from me]: Deer Creek Falls, Grand Canyon, Arizona (photo above)

For the record, I kind of don't get the appeal of waterfalls. I mean, they're cool and all, but they don't strike as particularly complex (and therefore, not particularly interesting)... I mean: gravity, right? ...It pulls water downhill... What's the big deal? (I had a conversation this summer along these lines at Waterfall #9 on this list, with a similarly-minded fluvial curmudgeon.)

...But people love them - When I poll my Physical Geology students at the end of the semester about what their favorite part of our Billy Goat Trail geology field trip, only a third or so invoke the migmatite, a third or so cite the physical challenge of climbing "The Traverse," and a third or so claim that viewing Great Falls was their favorite part. To each their own, I reckon: I'm glad they got something meaningful out of the trip... but I can't claim to understand it.

In my twisted worldview, Deer Creek Falls is interesting not merely because it's scenic (and a great place to go swimming), but because the waterfall issues from the Great Unconformity, and thus has geologic significance: It satisfies the intellect as well as aesthetic sensibilities.

Labels: arizona, california, grand canyon, new york, wyoming

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:

Labels: montana, msse, wyoming, yellowstone

Here's a couple of more photos from my travels out west this summer. This is in Jackson Hole, the large valley that abuts the Teton Range immediately to the east. If you've never been to the Tetons, you must go and check them out for yourself. They are an awesome, singular mountain range in the United States. Their shapes and sheer relief remind me of the Karakoram, or Torres del Paine, or some other awesome mountainous region of the world. It's really jaw-dropping.

Here's a shot of the Tetons from the northeast, visually pairing them with a line of coniferous trees in the foreground. Photographically, I like this parallelism in their shapes:



So what's up with the Tetons? What geologic processes give rise to their readily-apparent awesomeness? There's two main things going on here: faulting and glaciation. First, there's a major normal fault along the base of the range. The Tetons have moved up as a block while the Jackson Hole basin has dropped down as a block. As the rocks of the Tetons (some as old as 2.8 Ga) have been eroded, sediment was generated, and that dropped down to fill in the hole to the east. Jackson Hole is full of of sediment (over 20,000 feet deep), and then the peaks of the Tetons rise an additional 7000 feet beyond that. Based on offset of the Cambrian Flathead Sandstone on either side of the fault, total displacement is estimated to be 30,000 to 35,000 feet (Love, 1987). Even relatively young geologic units in Jackson Hole, like the Yellowstone-erupted Huckleberry Ridge Tuff (2.1 Ma), dip significantly towards the fault (Good and Pierce, 1996). Movement along this fault is ongoing, raising the mountains on average ~1 centimeter per year, with most movement having taken place over the past 9 million years. The Tetons are generally regarded as the youngest range in the Rockies.

Here's a shot coming north from the Gros Ventre landslide area (subject of a future post) towards the main road. A photogenic herd of bison was grazing on the grassy sagebrush flats, purposely maneuvering between me and the mountains so they would have a nice backdrop:



Once the Pleistocene ice ages began, the tall Tetons accumulated a lot of snow, which packed into glacial ice. Alpine glaciers started flowing downhill, and carving the rock of the mountains as they did so. That created the distinct U-shaped valleys seen in these photos, and left pointy little nubbins between them: the glacial horns like the Grand Teton and Mount Owen. The rocky debris scraped off the Teton block was deposited in Jackson Hole along with till from the Yellowstone ice cap to the north. These piles of glacial till are easily demarcated by the coniferous trees that grow on them, unlike the grasses and sage of the outwash plain.

References:

Good, John M., and Kenneth L. Pierce (1996). Recent and Ongoing Geology of Grand Teton and Yellowstone National Parks, Grand Teton Natural History Association, Moose, Wyoming, 58 pages.

Love, J. David (1987). "Teton mountain front, Wyoming." In: Geological Society of America Centennial Field Guide - Rocky Mountain Section, Stanley S. Beus, ed. Geological Society of America, pp. 173-178.

Labels: faults, geology, glacial landforms, travel, wyoming

Just now getting around to reading last month's issue of National Geographic, but it's a good thing I got to it yesterday rather than tomorrow -- because today's the day I talk about comets, asteroids, and meteors in Physical Geology class, and one of the topics that people always love to talk about is what happens when those big dumb space chunks smack into Earth.



The article's a good read, and illustrated with magnificent images, like this classic 1972 image of a fireball over Jackson Lake, Wyoming. That's the Tetons in the background. Check it out.

Labels: meteors, news, wyoming

On Saturday, June 14, I drove from Fort Collins, Colorado northwest across Wyoming, ending up just west of Cody in Shoshone Canyon.

Here's a few photos I took along the way:

Hogbacks (or "incipient hogbacks?") north of the Interstate (not sure whether this qualifies as the Laramie Mountains or the Medicine Bow Range, or some other range altogether).

Regardless, what you're seeing here is what happens when tilted sedimentary strata are incised by streams. The stream valleys develop at regular intervals along the slope, and notch the sedimentary layers, which themselves have different resistances to erosion. As a result, these triangular-shaped slabs end up poking up along the flanks of the mountains (the Flatirons outside of Boulder, Colorado, are perhaps the best known example).

The Wind River Range appears in the distance. Seeing big bad mountains makes me happy.


Road trip man!


The Prius at the southern (upstream) end of Wind River Canyon, between Shoshoni and Thermopolis:


...And looking downstream (north):


Unconformity between Archean basement rocks and overlying Cambrian sandstone:


The Wind River:


An outcrop on the way north, somewhere south of Meeteetse. Got some cool green concretions here, and coasted downhill for more than ten miles:


Camp at the end of the day. This is at Buffalo Bill State Park, between Cody and the eastern entrance to Yellowstone (Sylvan Pass, subject of a photo I put up yesterday). The body of water seen here is the Shoshone Reservoir. I enjoyed a pleasant evening here of drinking wine, writing a letter, and watching grebes in the water.


Dark clouds came over later, hastening nightfall over the park. Note the addition of the rainfly to the tent. Turns out we just got a sprinkle, no real downpour.


Life on the road is (was) good. Months later, it makes me happy to look at these photos and think about rolling along across the great North American continent, checking stuff out, seeing new places. Classes start on Monday for me, and I'll be locked down in DC for a bit... a fair trade, it seems to me, if my job allows me to go out and see places like these during the summers.

Labels: birdies, travel, wyoming

...No kidding!

This photo was taken in early June, when I drove through Yellowstone for the first time this summer... there was still snow eight feet deep along Sylvan Pass at that time!

Labels: snow, travel, wyoming, yellowstone

This summer, I saw "the Great Unconformity" in a couple of locations.

An unconformity is a break in the local geologic record -- a period of time which elapsed without being recorded by the deposition of rock units. Often unconformities mark places where erosion has erased part of the local rock record, but sometimes they just mark periods of non-deposition. (Analogy: You can get a blank page in your diary two ways. You can either take a day off from writing, or you can write that day's entry and then later go back and erase it. Either way, you end up with a day going by and no journal entry.) People call the major break between metamorphic and igneous "basement" rocks and overlying sedimentary layers the "Great" Unconformity, though it's not the same age everywhere. It's just shorthand, really.

Anyhow, here it is in the Grand Canyon (photos provided below are both unadorned and annotated versions):





Give or take, there's about 1.2 billion years missing along this ancient erosional surface. Intuitively, this probably makes sense, since metamorphic rocks like schist and 'distilled' intrusive rocks like granite are characteristics of mountain belts, where they form at depth. In order to get those interior-mountain-belt rocks to the surface takes lots of erosion over lots of time (though not necessarily that long -- in DC, for instance, we have interior-mountain-belt rocks exposed that 'only' took 360 million years to make it to the surface). In the above photos, the metamorphic rocks and granites below the unconformity formed about 1.7 billion years ago, during the Mazatzal Orogeny, and the sedimentary layers on top (both quartz sandstones) were deposited in the Cambrian period, about 543-488 million years ago. They represent passive margin sedimentation along an ancient transgressive seashore, something like modern day beach sands along the east coast of North America. So, to get something like the Great Unconformity, take something like coastal Maine (Acadia National Park, say), and bury it beneath something like Virginia Beach.

And here "it" is again, in Wyoming's Wind River Canyon (between Thermopolis and Shoshoni):





A zoomed-in look at this same outcrop:





This time, however, the rocks below the unconformity are much older* metamorphics (schist & amphibolite) and granite. According to Maughan (1987), these are the oldest rocks exposed in Wyoming, having formed about 2.9 billion years ago. They were then metamorphosed at 2.75 billion years ago. These truely ancient rocks (Archean) were then eroded and exposed at the surface, where quartz-rich sand was laid down atop their burnished roots. Aside from the difference in the age of the underlying basement rocks, the story is very similar to the one at the Grand Canyon.

* Thanks very much to Kim, who pointed out my error in under-stating their age in an earlier, more-poorly-researched version of this post.

Reference:
Maughan, E.K. (1987) "Wind River Canyon, Wyoming." In: Geological Society of America Centennial Field Guide - Rocky Mountain Section. S.S. Buess, ed. p. 191196.

Labels: archean, cambrian, dc, grand canyon, primary structures, proterozoic, unconformities, wyoming

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

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!

Labels: archean, astronomy, cold, hot springs, microbes, montana, msse, wyoming, 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

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!

Labels: field trips, montana, msse, travel, wyoming, yellowstone

In preparation for my time out west this summer, my friend Michelle loaned me her copy of Cruisin' the Fossil Freeway, by Kirk Johnson and Ray Troll. It's a great read, and it's got me really psyched to start driving around the west, looking at geology. It also makes me wish for an informed local guide to clue me in to good outcrops.

I really liked this book. Johnson, a paleontologist with the Denver Museum of Nature & Science, narrates a 5,000-mile roadtrip travelogue about zipping around the western U.S. in search of fossils. Joining Johnson is Troll, a celebrated artist who makes clever art in several media. The book is light-hearted, well-informed, funny, and relaxed. I really liked it, and would recommend it to anyone with an interest in natural history, fossils, roadtripping, or Ray Troll's art.

Coincidentally, Geotimes reviewed the book in their May issue.
...And NPR beat them to it last fall.

Labels: books, colorado, fossils, kansas, nebraska, wyoming