Wednesday, December 2, 2009
Wednesday, November 11, 2009
The one I want to discuss today is on the southwestern corner of this intersection. It's currently a Unification Church, but the structure was built in 1933 as the first chapel of the Church of Jesus Christ of Latter Day Saints (the Mormons) in DC. According to Chris Barr, an attorney and amateur paleontologist who is compiling an "Accidental Museum of Paleontology" about DC's building stones that include fossils, "two grandsons of Brigham Young contributed to its design and artwork, and the church consciously echoes the design of the Mormon Temple in Salt Lake City." Not only that, but they opted to use exterior buuilding stone shipped in all the way from Utah!
Chris's website about all the fossil-containing DC building stones is nearing completion, and I will post a link here when it is live. In the meantime, I wanted to share some of the information he compiled about the rocks which makes up the exterior of the Unification Church: Utah Bird's Eye "Marble."
Here's what it looks like:
The elliptical shapes you're seeing here are oncolites (sometimes called "oncoids"), and they are essentially little ellipsoidal stromatolite balls. A little grain of this or that gets encrusted by calcifying algae / microbial slime, and layer upon layer gets added with addition growth of those slime layers, growing up through the calcite they trap. It's not a true marble, in other words: it's a limestone.
These limestones with oncolites originated in a large freshwater lake called Lake Flagstaff, approximately 66 to 58 million years ago (Paleocene). The lake was present in northeastern and central Utah. According to Chris Barr, the stone used on the exterior of the Unification Church was quarried at "8,000 feet in elevation, in what is now the Manti-La Sal National Forest in the mountains more than 60 miles south of Salt Lake City."
Some of them have partial void spaces internally, which have since been filled by sparry calcite:
The horizontal layering of the non-spar gunk inside these voids provides a little paleo-horizontal "level" to help reconstruct which way was "up" when these sediments were deposited. (This particular block is on its side in the wall of the church; I've rotated the photo to paleo-up using Photoshop. (That's also where the arrows come from!)
For some perspective on the recent history of the building where these cool rocks are displayed, I'll quote from Chris Barr's soon-to-be-released website: "Changes in the neighborhood, the growing needs of the Mormon community, and the prospect of costly repairs to the walls, led to the end of services in 1975 and the sale of the chapel, which was purchased by the Unification Church in 1977. The Mormons constructed a new, larger chapel in suburban Bethesda - a structure that also provides a visible reference to the temple in Salt Lake City."
Sunday, September 20, 2009
Another five old maps
Wednesday, May 20, 2009
Massive set of concentric ribs (arrest lines)?
My MSSE advisor John Graves (previously mentioned here) went on a float down the Green River in Utah last weekend.
This appears to be a huge set of concentric ribs (a.k.a. "arrest lines") on the face of a big joint in massive quartz-rich sandstone. Bedding runs ~horizontally across the image, though not to be confused with the perfectly horizontal "bathtub ring" waterstains from the river. John says, "My best guess from the guide book is that it's Entrada Sandstone, Carmel Formation & Navajo Sandstone top to bottom." The fracture appears to have started in the middle of the cliff and propagated downward and outward. Note how the ribs "flare" out at the far edge. I guess an alternative hypothesis is that this is some weird kind of dune cross-bedding in the Navajo Sandstone: the inside of a barchan dune, perhaps? (though barchans wouldn't form in the "sand sea" situation in which the Navajo was deposited)
Anyone else want to offer another interpretation for this? I think that's what it is.
Thursday, January 15, 2009
Ancient Landscapes of the Colorado Plateau by Ron Blakey & Wayne Ranney
Over the winter break, I read the new book Ancient Landscapes of the Colorado Plateau, by Ron Blakey & Wayne Ranney. This is an excellent read, and a terrific introduction to the geologic history of one the world's most dramatic landscapes. Blakey's maps have been featured on this blog before, and he has been kind enough to allow me to modify some for use on my field course websites (like here and here and here). The book goes through geologic time and makes extensive use of beautiful paleogeographic maps to reveal the story of mountain-building, transgression, regression, sand-dunes, faulting, volcanism, and erosion that characterizes the Colorado Plateau. It's not just paleogeographic maps, by the way: there are also plenty of shots of fossils, Colorado Plateau landscapes, and comparable modern depositional environments to enliven the story. It's a graphic story, well told with excellent graphics. I recommend you get yourself a copy if you've ever been to the Colorado Plateau, or if you ever plan on going there.
Tuesday, September 2, 2008
This was the scene at the campground I stayed at this summer on my first day south from Bozeman to Las Vegas. This is a campground south of Huntsville, Utah, in the Wasatch range west of Ogden (map).
It's not snow you see on the ground, despite being white stuff that accumulated in a layer several inches thick, and blew into drifts like snow would.
These are the seeds of the cottonwood tree (Populus fremontii), which like dandelions, have a bunch of fluff emerging from them to catch the wind. This allows the species to spread its range by letting the wind carry its seeds to new locations. While cottonwoods are ubiquitous in wet areas of the west, I've never seen this kind of accumulation of cottonwood fluff before.
It was like warm snow -- quite magical to see.
PS - Prius note: The fuel mileage out west this summer wasn't as good as the regular commute back home in DC, but it was still pretty good. The total roadtrip (~10,000 miles) ended up averaging 52.6 miles per gallon of gasoline. Can't complain about that.
Monday, July 7, 2008
The route back to Bozeman
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.
Tuesday, June 24, 2008
Bozeman to Zion
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.
Friday, June 20, 2008
One down, and off to the south
Also, along similar "rock and road" lines, I had an article published in Geotimes this month on the roadtrip I did two years ago from DC up to Alaska and back. You can check it out here.
FYI, I got a new camera for this trip, and haven't been able to download any pictures off it yet (a stupid software issue), so that's the reason for the lack of photos lately. My apologies!