Wednesday, October 21, 2009

GSA update 4

My final day at GSA was fruitful. I started off in the "Earth, et al." session hosted by ODU's Nora Noffke. It was devoted to the Precambrian, and had some interesting talks about fluctuating oxygen levels, mineral evolution, microbially-induced sedimentary structures, and Neoproterozoic glaciation. This last one was most interesting to me: UMD's Jay Kaufman talked about field work he conducted in Siberia last summer, documenting a diamictite unit between Ediacaran strata and Cambrian strata. There's even a carbon isotope excursion to match up with it! Cool... literally.

I had lunch with my friend David Dantzler, who I hadn't even realized was at the conference, until I saw him come in to one of the Darwin-focused sessions. In the afternoon, I attended another eight talks, including some on greenstone belts in South Africa, some on geological education, and a couple about the evolution of orogens, with an emphasis on South America. (One of these was an excellent talk by Brian Romans about his field area in Patagonia.) I finished up with Kim Hannula's talk about the geoblogosphere's role in supporting women geoscientists. Then it was time to bug out: back to the hotel, then to the airport, then to Los Angeles, then to Dulles, where I arrived this morning at 6:30am. On the flight, I took an Advil PM, put in earplugs and wore one of those little eye-masks so I could get some decent amount of sleep... Mixed success on that front. Once I got to Dulles, I got some coffee, and headed straight to work! It's good to be back in the familiar environs of my office and lab again. Thanks for a great conference, everyone!

Also: GSA is maintaining a webpage summarizing the various posts from registered geobloggers. It's incomplete, but a useful idea: a repository for all the stuff being said about the conference from the various attending geobloggers.

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Thursday, October 15, 2009

Summer 2010 classes

I've just submitted a list of the classes I intend to teach for summer 2010. Here they are on NOVA Geoblog, before you can access them in the official Schedule of Classes...

GOL 135 (070N) The Bedrock Geology of Washington, DC. HYBRID COURSE: pre-trip reading, field study and post-trip report. One-day field trip Saturday, June 12. Rain date: Sunday, June 13. Important pre-trip logistical information and preparatory readings located online. This trip will focus on the land upon which the capital city is built, including exposures in Rock Creek Park, Georgetown, and Adams-Morgan. Includes discussion of oceanic sediments, the Rock Creek shear zone, igneous rocks emplaced during Appalachian mountain-building, Cretaceous river gravels, dinosaur bones and recent faulting. Students will be evaluated with a field trip report which will be completed after the trip itself. NOTE: This trip involves moderately strenuous hiking on forest trails. Meet in back of the CT building at 9:00 a.m.; Return by 7:00 p.m. For information about meeting time/place or other questions call (703) 323-3276 or email cbentley@nvcc.edu
HYBRID course
Additional info online

GOL 295 (4 credits) Regional Field Geology of the Northern Rocky Mountains: July 10 to July 25, 2009. Pre-trip meetings Wed. June 9 and Wed. June 23, 6:30pm, in CS 217. Western Montana and Wyoming showcase tectonic, sedimentary, geomorphic, and volcanic features which provide world-class examples of geologic processes. Students in this course will complete field studies of locations in Yellowstone and Glacier National Parks, as well as several other field sites. The course will involve VERY STRENUOUS outdoor physical activity: Students are expected to hike several miles at high elevations in rough mountainous terrain in order to accomplish course objectives. Airfare, lodging, and transportation are covered in the approx. $1400 course fee (does NOT include tuition). For up-to-date information and a complete itinerary, see the course website or contact the instructor at cbentley@nvcc.edu or (703) 323-3276.
Extra fee
Instructor permission required
Additional info online

GOL 299 (071N) (2 credits) Snowball Earth. June 14-19, 2009. HYBRID COURSE: pre-course reading, lab, field study and post-course report. An episode of glaciation 700 million years ago, dubbed Snowball Earth, may have provided for the evolution of multicellular life. The Snowball Earth glaciations stretch our conception of the limits of climate change: the ice apparently reached from the Earth's poles to its equator! Scientists infer that the runaway freezing event was only ended due to volcano-induced global warming. This course examines the geological, chemical, and biological evidence for Snowball Earth, and includes a field trip to local "Snowball" deposits. Course meets four times: three evening sessions (6pm-9pm) in CS 217 and all day on a Saturday (9am-5pm). The schedule is: Monday June 14 (lecture), Wednesday June 16 (lab), Friday June 18 (discussion), and Saturday June 19 (field trip). For further information call (703) 323-3276 or email cbentley@nvcc.edu or go to the course website.
HYBRID course
Additional info online

Anyone in the Northern Virginia area who's interested in any of these classes, drop me a line!

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Tuesday, April 14, 2009

Change of topic: Hoffman lecture

Paul Hoffman is speaking next Wednesday (April 22) at the Geological Society of Washington; I've just recieved word that his topic has changed from Snowball Earth to "The Pleistocene glacial controversy and the discovery of climate warming and crustal dynamics." I'm curious to see what Hoffman has to say about the 160-year old controversy as to whether there had been recent "Ice Ages," and how that relates to his currently-controversial ideas about the Snowball. Whatever he says, it's likely to be thought provoking.

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Friday, February 13, 2009

Cool speaker for Bradley Lecture

It was announced at Wednesday's Geological Society of Washington meeting that this year's Bradley Lecture will be delivered by Paul Hoffman, Emeritus Professor of Geology at Harvard University. The lecture is scheduled for the evening of April 22, starting at 8pm at the Cosmos Club.

Dr. Hoffman is best known for his work promoting the "Snowball Earth" hypothesis. It ought to be an exciting evening of geology!

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Thursday, February 5, 2009

Marinoan sponges?!?

A graduate of my summer Snowball Earth course just forwarded me a link to a news item about a recent discovery which finds biomarkers exclusive to the sponges during Marinoan-glaciation-aged sediments on the Arabian Peninsula. The strata are "at least 635 million years old."

This is significant because the usual line about Snowball Earth is that multicellular animals show up after the glaciations end, not during. So what's going on here? Looks like we didn't understand the thing as well as we thought. For many people, the co-incidence (in the most literal sense) in timing between the end of the glaciations and the first multicellular animal fossils was one of the most intriguing things about the Snowball hypothesis -- we all want to know where we came from, after all -- and this may take some of the wind out of those sails. As humans, we like a good story, and this may be one reason the idea of a Snowball Earth is such a popular notion: it's a dramatic story about where we came from, and one that stretches our conception of the limits of change on our planet. But now that story exhibits a flaw upon closer scrutiny, and it makes it less satisfying. The consolation prize is that event though the story isn't as neat, it's closer to the truth. That's the way science works -- especially earth science, which isn't often as tidy as a fairy tale.

Hat tip to Christina T. for passing this on!

UPDATES: (1) Chuck read the paper and wrote it up at his blog. (2) WIRED magazine is also reporting on this, calling the discovery the world's "oldest animal fossils." I'm not sure I agree with that phrasing -- but that probably stems from my lack of familiarity with the reliability of biochemical signatures over traditional body or trace fossils.

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Tuesday, August 5, 2008

Driving from Montana to DC

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!

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Friday, April 11, 2008

Almost famous

NOVA recently updated their webpage, and now we have a big banner photo which changes every time you hit "refresh." A colleague pointed out that there's an image up there of the Snowball Earth field trip last summer:

I think it's safe to say that now John, Judy, David, Jay, Sam, and I are officially B-list celebrities...

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Saturday, February 23, 2008

Acid oceans & Snowball cap carbonates

The geoblogosphere spawns semi-monthly collections of blog posts on a particular theme, and this time around, Dr. Lemming is hosting with the theme of "things that make you go Hmmmm." The idea here is to write a blog post about something you don't understand in geology -- a mystery. Here's my contribution:

When I was in graduate school at the University of Maryland, I started hearing about a crazy notion that the entire planet had frozen over in the past. Apparently, multiple streams of evidence (chemical, isotopic, geologic, and magnetic) suggested that during the Neoproterozoic era of geologic time, the planet experienced a mega-Ice Age. There were even glacial deposits within a few degrees from the equator. If you've got glaciers operating within a few degrees of the equator, some scientists argued, then that means the Earth would have been entirely sheathed in ice. Its reflectivity ("albedo") would have been so high that most (~85%?) of incoming solar radiation would have been reflected back out into space, and that would have made the planet even colder, promoting more snow and ice. This positive feedback cycle would have reached a tipping point if the planet were covered in ice from the poles to approximately 30 degrees latitude: once it got that white, the "runaway albedo" feedback would have reached a tipping point, and wham, you've got a planet that looks like a great big snowball.

This led Joe Kirschvink (of Cal Tech) to dub this episode of glaciation the "Snowball Earth," which is about as catchy a name as a scientific hypothesis is every likely to get. The idea was then heavily promoted by Paul Hoffman (of Harvard), who was seeing strange stratigraphic patterns during field work in Namibia. Among the evidence Hoffman eventually accumulated for the Snowball were the following: "dropstones" (boulders, presumably dropped by icebergs into fine-grained offshore marine deposits, squishing the layers beneath them); conformable stratigraphy of "tropical" carbonate topped by glacial tillites, topped by more "tropical" carbonate; carbon isotope anomalies in overlying "cap" carbonates indicating a massive inorganic dumping of precipitated CaCO3; delicate crystal fans (some meters tall) precipitated rapidly in the post-Snowball ocean; and the temporary reappearance of banded iron formations (BIFs), which had not been seen since the Paleoproterozoic (and indicated an anoxic ocean, such as one sealed beneath a layer of ice).

When Kirshvink pitched the initial hypothesis, he also proposed how the Snowball could have ended (in a deliciously short, non-peer-reviewed paper): he noted that just because the surface of the planet was frozen, that would have meant diddly to plate tectonics. Radiogenic heat from the Earth's interior would have continued to drive plate tectonic processes, and that meant subduction would have continued, beneath the icy rime. If subduction continued, that meant that volcanoes would have continued to erupt, and as Iceland and Antarctica show us today, volcanoes can erupt underneath glaciers. This is important because volcanic outgassing has a substantial percentage (~15%) of carbon dioxide (CO2), and CO2 absorbs reflected infrared radiation: it's a greenhouse gas.

But with the entire surface of the planet frozen, what would have happened to this degassed CO2? If the planet's surface is frozen solid, that means the hydrologic cycle would be shut down, and the usual means of removing CO2 from the atmosphere (e.g. photosynthesis & also deposition of carbonate sediments like limestones) would be non-functional. Any CO2 emitted by volcanoes would therefore likely linger in the atmosphere, building up in concentration over time. Eventually, Kirshvink suggested, it built up to levels that caused global warming which compensated for the ice albedo effect, and the absorption of all that radiation by the CO2 melted the Snowball.

As evidence for this audacious idea, Kirshvink pointed to the cap carbonates: all that limestone ("cap carbonate") deposited on top of the glacial units needed a lot of CO2 to be dissolved in seawater (and a lot of Ca+ too). The cap carbonates, it was suggested, represented the stratigraphic removal of all that built-up CO2 from the atmosphere. Once the levels of CO2 were drawn down to a non-hothouse level, the cycle could repeat itself. Modeling calculations suggest that it would take about 5 million years of CO2 buildup to melt the Snowball.

And this is what I don't get: if you've got an atmosphere full of CO2, I can see how that would melt the Snowball. But wouldn't it then acidify the ocean (with carbonic acid, like we're seeing today), making calcite dissolve, rather than be precipitated? If the ocean is undersaturated with respect to CaCO3, then that ocean should not host accumulations of limestone. How could the voluminous worldwide cap carbonates be deposited in an acidic ocean?

On the Snowball Earth website, a list of suggested reasons why Snowball Earth could not have happened are listed, along with Hoffman, et al.'s scientific rebuttals. But when they come to the question of acid oceans and the deposition of cap carbonates, you can almost see them shrug: "These are serious criticisms," they note. Hmmmmm.

Post-script: The idea is intriguing not merely scientifically, but also in terms of the way science gets done: by people, sometimes people with outsized personalities. Paul Hoffman promoted the idea with an "evangelical zeal" (according to Gabrielle Walker, who wrote a book about the whole idea and the scientists involved). Hoffman's relentless pushing of the idea ruffled a good many feathers. Some scientists fought back, motivated in part by these chafing interpersonal dynamics. There's nothing like a little scientific controversy, and this is what Walker's book focuses on, more than the details of Snowball science.

When I found that Jay Kaufman (of UMD-College Park) was interpreting a local diamictite(near Aldie, VA) as a Snowball Earth tillite (and the overlying marble layer as a cap carbonate), I thought "this could make a great class." Last spring, I applied for and received a grant from the Virginia Community College System to develop a 2-credit class for NOVA utilizing these local rocks as a gateway to understanding the Snowball Earth hypothesis. I offered the class for the first time last summer, and I'll be offering it again this summer in August. We were fortunate to get rock samples from Virginia's two putative Snowball deposits as well as a suite of samples on loan from Gene Domack of Hamilton College. These "Snowball Suite" samples include tillites and dropstones from Namibia, Greenland, Mauritania, and Canada, as well as international BIFs and cap carbonate samples. I have to tip my hat to Dr. Domack and his colleagues: making these samples available is a terrific service in support of geoscience education.

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