New Scientist gives the full run-down on their findings.

Reference: Matthews, H. D., and K. Caldeira (2008), Stabilizing climate requires near-zero emissions, Geophys. Res. Lett., 35, L04705, doi:10.1029/2007GL032388.

Labels: climate change, CO2, global warming

Just got through watching an episode of the PBS program NOVA (which I like to refer to as the "other" NOVA). The episode was titled "Volcano under the city," and it looks at the volcano Nyiragongo in Congo, central Africa. This was the same volcano that had such a spectacular eruption in 2002, when lava flowed through the city of Goma, on the shore of Lake Kivu. The program follows UN vulcanologist Jacques Durieux on a journey through Goma and into Nyiragongo to evaluate the risk for the ~2 million people who live in the mountain's shadow. The program explores volcanic hazards including lava flows, landslides, lake overturn (a la Lake Nyos), and pockets of CO2 in low-lying areas on land. This last one provided what I found to be the most dramatic footage: Durieux tosses a signal flare into one of the ditches, and the smoke rises and flows on top of the invisible layer of CO2 below: it demonstrates dramatically how there's something invisible pooled in that ditch due to its density. There's also plenty of footage of frothing spewing blobby lava, if that's your thing. As is often the case, the narrator overpitches the dangerous aspects of the situation, and the whole hour-long show feels kind of like a hyped-up movie trailer. Certainly the situation there is dangerous, but I feel like some credibility gets lost when every word is uttered with a sense of looming menace.

Labels: africa, CO2, movies, tv, volcano

On an odd day, a post about an odd place:

Reading David Byrne's blog last week, I was alerted to the existence of The Museum of Jurassic Technology in Los Angeles. When I went to this museum's website, I found a phantasmagoria of odd objects and pseudoscientific farce. It's not supposed to be real; it's supposed to be art. But... why "Jurassic?" Like a lot of McSweeney's works, it seems a little too clever for me to "get." Though not a geologist, Byrne seemed similarly perplexed: "the mixture of the real ... and the imaginary... is a bit of a head twister at first."

Labels: art, museums, websites

So, this is weird: a new insight into the planet Mercury is that it has a big long tail which extends away from the planet, strung outwards by the solar wind (a stream of charged particles shooting away from the Sun in every direction). Comet tails are also due to the solar wind's erosive effect, vaporizing particles & dragging them "down-stream" (i.e., away from the Sun). The tail is long: At 1.6-million miles in length, the streamer of sodium atoms is more than 100 times the planet's radius. Read more here.

Labels: news, planetary geology

Last night at the meeting of the Geological Society of Washington, we were treated to a couple of really entertaining talks. The first was by John Eichelberger, of the U.S. Geological Survey in Reston (formerly of UAF). John is interested in Plinian eruptions -- the ones where volcanoes shoot massive amounts of ash and gas upwards in an eruption column. He made the point that while Plinian eruptions are widely characterized as "explosive," they are actually a steady state phenomenon with a high volume, "like a firehose."

Labels: gsw, volcano

National Geographic has an article online about a cool new fossil from Spitsbergen, Svalbard (the Arctic island achipelago belonging to Norway). It's a plesiosaur, a marine reptile from the Jurassic period of geologic time. The front flipper is almost ten feet (3 m) long! The online article includes a picture gallery (the site, the fossils, and National Geographic's beautiful reconstructions).

Labels: fossils, norway, websites

Picking up from yesterday's post about my hike along Windy Run in Arlington, Virginia...

Just downstream from the waterfall (and crossing the trail) is a recent rockslide. Between D.C. and Great Falls (12 miles upstream), the Potomac River flows through a canyon called the Potomac Gorge. It's hundreds of feet deep overall, and consists of a series of nested straths (bedrock "terraces"), each shaped roughly like (half) a canoe. (At the tip of each canoe is a waterfall leading up to the next strath). Where the vertical distance between straths is great, as it is at Windy Run, mass wasting events serve to break down the cliffs and reduce the crisp profile of the straths.


This rockslide happened in 2005, and the area of "raw" rock up at the top of the cliff reveals the source area for the rock debris below. I wish I had taken a photo of this three years ago when it was really fresh -- it would be an excellent place to do repeat photography to show how the talus pile and cliff face change over time. Upstream are several examples of older talus aprons that have been overgrown by plants and buried in soil. Already, you can see that a few Ailanthus trees (single, upright pole-looking things) have taken root in this fresh landscape.


Once you get down from the Windy Run trail to the Potomac Heritage trail, here's the view of the river, looking upstream. Virginia's on the left; D.C. on the right. A slight "shelf" can be seen on the Virginia side where a notch has been cut to host the George Washington Parkway.


As I hiked along, I found this dead mole. It's a big fat sucker, and it must be quite fresh: probably a casualty from the previous 24 hours. Lens cap is 5 cm in diameter.


More critter evidence: here's a couple of small tree trunks that were decapitated by a beaver. Again, this is recent -- note the fresh curls of wood shavings at the base of the trunk.


But enough with these living entities: let's look at some rocks. This is the metagraywacke rock that makes up most of the Piedmont in our area. This rock is metamorphosed to various degrees up and down the Potomac River, in some places all the way to gneiss and migmatite. In some places, it's schisty, but in others primary sedimentary structures are still preserved. Upstream by Great Falls, for instance, we find graded bedding in isolated less-metamorphosed, less-deformed areas. Down along this stretch of the river, it preserves a diversity of sedimentary clasts, as shown in this image:

Here, you're seeing the graywacke matrix mixed in with a bunch of dark chunks. Today, these dark chunks are mostly biotite, but that's metamorphic. Originally, they were probably mud clasts. Little pebbles of granite and vein quartz are mixed in too. It's worth noting that not only are they metamorphosed, but they're also stretched out in the same direction: foliated and lineated. Many are squashed into X>Y>Z ellipsoidal shapes (where the letters refer to the lengths of the different axes of the ellipsoid), like a mango seed. Lens cap is 5 cm in diameter.

Let's pause for a moment and bring people up to speed if you haven't previously spent any time thinking about Appalachian geology. These rocks are part of the Appalachian mountain belt, which runs from Newfoundland to Georgia (by one definition) or from Texas to Scandanavia (by a more inclusive definition). The Appalachian mountain belt consists of three provinces: from west to east: the Valley and Ridge, the Blue Ridge, and the Piedmont. Two of these are topographically mountainous today: the Valley and Ridge and the Blue Ridge, as their ridgey names imply. But the Piedmont certainly counts as part of the ensemble, and if you compare it to the other two, you'll find that it experienced the most metamorphism, the most deformation, and is intruded in many places with syn-orogenic granites (which neither of "the Ridges" can claim, at least not for Paleozoic orogenies). The Blue Ridge and the Valley and Ridge are deformed, yes, and even lightly metamorphosed, but the Piedmont is really where the action is: this is the center of the ancient Appalachian mountain range. These rocks experienced some serious continental convergence.

So what was the Piedmont before it was the Piedmont? An ocean basin. Before the Atlantic, before Pangea, there was an ocean basin off the "east" coast (it was really the south coast at that point, but no matter...). We call this dead ocean the Iapetus Ocean. The Iapetus was closed via subduction throughout the Paleozoic, and it closed for good when Africa rammed into North America, metamorphosing these rocks and raising the Appalachians. As subduction narrowed the Iapetus, sediments atop the oceanic crust were scraped off in a big jumbled pile called an accretionary wedge. (It is for this mixed-up melange that the infamous geo-blog carnival is named.) You want to see an accretionary wedge being scraped up today? Dive down to the Peru-Chile Trench, off the west coast of South America. You want to see a fresh one at the surface? Visit California's coast ranges, which are a Mesozoic accretionary wedge, raised above sea level. You want to see what an accretionary wedge looks like after it's been tectonically squeezed between two continents? Come to the Piedmont!

Our metamorphosed accretionary wedge consists of a bunch of the sediments that were deposited in the Iapetus Ocean, including what was originally graywacke (a mix of sand & mud). Occasionally, you find a sedimentary clast that's a bit more intriguing, like this one (white arrow):

What intrigues me about this little sedimentary cobble is the fact that it's foliated, which indicates metamorphism and differential pressure, but its foliation does not line up with Appalachian foliation. This cobble was foliated before it was deposited in the accretionary wedge. Therefore, it was derived from some area that had previously experienced mountain building & regional metamorphism (presumably a continent). That ancestral orogenic episode produced a source rock from which this cobble was derived. Then that cobble was deposited by sedimentary processes somewhere and (possibly later) incorporated into the accretionary wedge, which then was metamorphosed (& foliated) itself. Lens cap is 5 cm in diameter.

Here's another one, which shows its foliation a bit better:

When I see something like this, I start to wonder, where did this cobble come from? What was its sedimentary provenance? Is this a North American cobble that attained its foliation in the Grenville Orogeny (~1 Ga)? Is this an African cobble that got squeezed in some pre-Pangea Gondwanan orogeny? Is it derived from a nameless microcontinent that was formerly marooned in Iapetus oceanic crust (a la Madagascar) and is now accreted to some continent as an exotic terrane? Do the answers to these questions change how we think about the (1) closure of the Iapetus, (b) Appalachian Orogeny, (c) assembly of Pangea?

Elsewhere in the Potomac Gorge, there are other clasts in the accretionary wedge complex that encourage similar thoughts (for instance, you can check out the photos at the top of this page). Another question raised by these clasts is this: Does their position amidst such relatively fine grained sediments (the mud and sand of the graywacke) represent original deposition? Or is that simply tectonically-induced "shuffling" in the blender-like environment of the accretionary wedge? The rocks in an accretionary wedge are not stratigraphically coherent, but sometimes they have little areas that are. If these clasts are in their original depositional position relative to the graywacke matrix, what does that tell us? Are these landslide deposits? Or are these "Snowball Earth"-related glacial dropstones? Without the original sedimentary bedding (destroyed via orogenic metamorphosis & deformation), it's impossible to answer these questions, but it sure would be nice to know.

Lastly, I'll note that everything I've talked about so far (metagraywacke, mysterious clasts, quartz veins, granite intrusions, and regional foliation) are all cut by a series of joints, brittle fractures in the rock. These joints are arranged in a series of joint sets which intersect one another, resulting in the "blocky" nature to bedrock exposures in the Potomac Gorge (example). Here, along one Gorge-bounding cliff, I saw that the joints had begun to accomodate some sliding of the blocks of rock on either side. Technically, they aren't joints any longer, but faults, instead. Total offset is only a few inches, but it shows up well in a photo like this. Note the similar sense of motion on the more distant fault "scarp." A housekey (with pink ribbon attached!) is jammed into the closer fault to give a sense of scale.


All in all, an hour strolling along Windy Run provides some terrific opportunities for reflection on the checkered geologic past of the Piedmont and the Appalachians, and the continuing geomorphic evolution of the Potomac Gorge landscape. I enjoyed my little stroll. It was with reluctance that I turned around and headed back to the house to grade exams...

Labels: appalachians, faults, geology, mass wasting, plate tectonics, virginia

This past week, I stayed in Arlington, Virginia. My dad and stepmom were in London, and I was looking after my youngest siblings (both teenagers) by staying at dad's house and serving as the Responsible Adult. It's the same house I grew up in, and it has a lot of nice memories associated with it. At the end of the street, there's a little trail which leads off into the woods and downhill towards the Potomac River along a little creek called Windy Run. ("Windy" as in the weather, not as in sinuous, though it is that, too.) At the bottom, Windy Run launches off a waterfall and tumbles down into the Potomac Gorge. On Saturday morning, I decided to go take a hike down to Windy Run and reacquaint myself with the landscape and its rocks. Here's the view from the top of the waterfall looking across the river into D.C.


Here's a view of the waterfall from the side. The big ice-rimed log at the base is about a foot and a half in diameter, to give a sense of scale:

On the way down the trail, there lies a big boulder of quartzite. This is my first rock. By that, I mean that this specific boulder is the first time I learned to put a name to a chunk of the Earth: my dad taught me that it was quartz, and I committed the name to memory. Today I would note that it's milky quartz, indicating hydrothermal deposition. (Tiny inclusions of water in the crystal lattice scatter incoming light and make it appear white.) Its upper surface is covered in black lichen. Pondering it anew on Saturday, I wondered if learning the name of this boulder in the late 1970s was the first step leading to me towards my ultimate career as a geologist. Lens cap is 5 cm in diameter.


My "first rock" lies at the base of a hill, below a linear trail of other quartz boulders. This array likely represents a subterranean vein of hydrothermal quartz, a common feature in the Virginia Piedmont.


For instance, here's a big vein of hydrothermal quartz (center) cutting across the metagraywacke host rocks at the top of the Windy Run waterfall. It's about a foot wide, and emplaced at a ~20 degree angle to the regional foliation (which strikes ~N25E). The quartz vein is oriented approximately vertically, just east of true north.


Here's some more vein quartz in the metagraywacke matrix. Foliation runs approximately left-right across this image. Note how there are large bodies of milky quartz arrayed semi-parallel to foliation: these are probably best interpreted as boudins: the results when a tabular vein of quartz was broken into chunks, and these chunks were smeared out along along the foliation during mountain-building. Boudinage (the process of producing boudins) is a somewhat brittle behavior (breaking) and somewhat ductile (smearing): under the proper combination of high temperature and directed pressure, quartz can act like pizza dough. It's capable of being molded, but also capable of separating into coherent pieces. We call these "boudins" because they resemble sausages strung out in a row ("boudin" is French for sausage). Here, only one boudin is shown, but click here for some other examples. The boudin is about 3 cm in thickness, to give a sense of scale.

There are also smaller quartz-imbued veins (white arrows, extended with dashed lines) in this rock, cutting across foliation at nearly right angles. Note how the "infusion" of quartz along these thin fractures makes them more resistant to weathering (they stand up in high relief, as seen in the lower left). This set of small quartz veins was likely emplaced at the same time the rock was being squeezed during mountain building, for reasons I explain in the next photograph.

So here's my stress interpretation of this rock. The big blue arrows represent the principal stress direction. To simplify, you could think of one blue arrow as representing Africa and the other as North America, pushing on these poor oceanic sediments caught in the middle. The yellow arrows represent extension. As the rock gets compressed in from "top" to "bottom," it gets squished outwards left to right. This deforms pre-existing quartz veins by rotating them into parallelism with foliation, and also potentially boudinaging them into chunks like the big one. The green ellipse demonstrates this overall process. One way to accommodate the rock's stretching in the yellow-arrow direction is by opening up small fractures (like the ones on the left) which get infilled with quartz.


On my walk, I saw a couple of exposures of hydrothermal quartz that strained the definition: that is, they weren't all quartz. Instead, parts of them (~5%) appeared to be granite pegmatite. In this shot, you can see several large crystals of potassium feldspar set in the quartz. Large flakes of muscovite were also semi-common. Lens cap is 5 cm in diameter.


Here's another shot of the same phenomenon seen elsewhere on the trail: large crystals of potassium feldspar and muscovite set in the "quartz vein." At what point do we stop calling these quartz veins and start calling them pegmatite dikes? Is a single crystal of non-quartz enough to change our perception of the fluid from hot mineral-rich water to wet magma? Like many things in geology, these features indicate that phenomena like dikes and veins are on a spectrum between end-members. In other words, there are shades of grey in how these things form (in addition to how we interpret them). By the way, the greenish hue is algae, not epidote. Lens cap is 5 cm in diameter.


Granite dikes (including pegmatitic ones) are reasonably common in the Virginia Piedmont. Here, as a Windy Run example, is a small granite dike I saw in a boulder on my Saturday walk. Lens cap is 5 cm in diameter.


Tomorrow, I'll explore a rockslide I saw on Windy Run, as well as the nature of the metagreywacke itself. Stay tuned, rockhounds...

Labels: geology, granite, structure, virginia

Yesterday I found my cat Lola pondering a fish fossil from the Eocene Green River Formation. Because she's more of an Appalchian cat, I explained to her that this fish was preserved in flat-lying lacustrine deposits in southwestern Wyoming. The formation is notable for bearing impressions/carbon-films of many species, essentially an entire fossil lake ecosystem. She seemed interested, so I referred her to a travel article I wrote on the topic once for Geotimes. She padded off to read it.

Later, Lola conveyed to me that during a cat nap, she dreamt of her own fossilization in the Green River Formation style:

I replied, as I'm sure you would, that I'm not into the idea of pet cryo-preservation or taxidermy, and that I hoped she'd remain unfossilized for the foreseable future. That made her purr. I also reminded her that most cats don't like water, and hence are unlikely to fossilize in their usual habitat.

Ahh, Photoshop: even better than Facebook for wasting away the hours...

Labels: art, fossils, humor, lola

In this past week's New Yorker, Michael Specter examines the convoluted business of trying to measure a person's (or a product's) carbon footprint. Turns out to be rather complicated. An interesting, thought-provoking article: this is viewed in some sectors as an essential piece of information, but it's amost mind-numbing to try and cover every relevant consideration. I recommend the article.

Labels: climate change, CO2, global warming

Yesterday's post was featured in the geoblogospheroidal carnival "The Accretionary Wedge." Check it out to see what the world's geologists are hmmmming about.

Labels: blogs, geology

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.

Labels: climate change, CO2, geology, global warming, nova, snow, snowball earth, teaching

National Geographic has a news piece about a large fireball seen over Oregon early on Tuesday. A bunch of people witnessed it falling and then explode in the sky. The article suggests that in the days to come, we may find chunks of the exploded space rock in impact sites around the Pacific Northwest (assuming it's not that spy satellite the Navy shot down around the same time...). Check it out.

Labels: meteors

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

Labels: conferences, field trips, google, msse, teaching

Yesterday, Florida's state board of education felt obliged to stick the word "theory" into their description of the teaching of evolution. See this Reuters article for all the moronic details. Of course, evolution is a theory (i.e. well corroborated by many years of scientific testing & explanatory of a wealth of biological phenomena), so I don't have a problem with this definition per se, beyond exasperation with the motivations for its inclusion. I expect we'll see another lawsuit (a la Dover, PA) regarding this move, but in the meantime, it's an opportunity for science teachers to elucidate the difference between "theory" as it's used in science versus "theory" as it's used in casual conversation. So, the battlefield for teaching proper science shifts from Kansas to Pennsylvania to Florida. What would the Flying Spaghetti Monster say?

Labels: evolution, news, politics

Labels: art, dc, ethanol, global warming, humor, politics

Oil has hit $100/ barrel before, but it dropped back down to mere double-digits before the close of the market. Not so today: When the closing bell rang, "light sweet crude" was at $100.01. Blame Hugo Chavez, or blame Hubbert's Peak. It's some expensive stuff.

Labels: economics, oil, petroleum

This is an amphibian that you wouldn't want to meet in a dark alley: Beelzebufo, a monster fossil frog from Cretaceous sediments in Madagascar. It resembles the ceratophryine family of horned toads (sometimes dubbed "pac man frogs") that are now unique to South America, which the authors of a new study published in the Proceedings of the National Academy of Sciences.

Here, artist Luci Betti-Nash's whimiscal painting of Beelzebufo has it facing extant species Mantidactylus guttulatus, the largest frog in modern-day Madagascar.

The discovery of the big croaker suggests that South America and Madagascar were linked landmasses for much later than previously deduced from other lines of evidence. However, the newly-implied gap in time is substantial. Previously, it was inferred that the two landmasses separated 120 million years ago (Aptian), but the interpretation of this new fossil is that it must have been after 80 million years ago (Campanian). I'm not sure I buy that huge jump in separation dates based on a single genus of fossil frog: 40 million years is a substantial amount of time. On the other hand, sometimes "small" pieces of evidence like this lead to the development of new paradigms in scientific thinking. It has the potential to be the proverbial thread which unravels the sweater.

My caution: It's important to remember that fossils which resemble one another don't necessarily imply a continuous population: there's convergent evolution to consider, as well as the possibility of a highly conserved morphology over time. Both of these phenomena could maintain similar looking populations of "pac-man-esque" frogs on unconnected landmasses. And, I suppose, there's even the less-likely possibility of a "rafting" incident, where a few individuals ride a mass of vegetation across the ocean(s) from South America to Madagascar well after the two have separated. It happened to iguanas, after all: getting from South America to the Galapagos. Actually, with amphibians, their eggs can sometimes hitch a ride on bird feet too, colonizing distant new areas with ease. I'd like to know more about the presence or absence of relevant fossil frogs in Africa during the Cretaceous in order to better evaluate this new interpretation.

Read more about it in this New Scientist article. (I couldn't find the "cited" original article in PNAS, for some reason.)

Labels: amphibians, evolution, fossils, plate tectonics

Check out this great German animation called "Das Rad" about the difference in geologic time and human time. It was nominated for an Academy Award ("Best Animated Short Film") in 2003. I think it's pretty clever.

Labels: geology, movies

I have a confession to make. Geology was not my first love: birds were. I spent one summer in college watching cattle egrets. That research project helped me get into ornithology, & I've kept "birding" as a hobby ever since. Even these days, I don't usually manage to get through a geology field trip without pointing and shouting "Look! There goes a pileated woodpecker!" (or a Cooper's hawk, etc.) Birds are everywhere, and they're great.
Accordingly, I was pleased to get these photos Friday from my colleague, NOVA biologist Bill Gorham.

This is a female cardinal (Richmondenis cardinalis). She has a unique look: her head is white! Bill calls her Ms. Whitey.

He tells me that the bird "has been a visitor in my yard for over a year. Last winter she just had a white 'collar' around her neck, then during the summer her whole head gradually whitened."
Bill continues: "I understand the term 'leucistic' applies because it is certainly not albinism but a loss of all pigments in certain areas... I would have to guess that the progressiveness has something to do with maturity. She mated and had chicks this past summer but I think she was a youngster last winter. She is also a member of a local tribe of cardinals that get bald every summer in July and August. First it was just one male (who we called 'Baldy') but now there are several males and several females. I don't think it is mites; I think it is some kind of heat response. When they molt in the fall they get a full head of feathers again."

A few points to be made here: (1) I like sharing images of natural oddities, which is why I'm posting these images [with Bill's permission] here; (2) I like having colleagues who share images of natural oddities [I like the fact I'm part of a community of people at NOVA who are curious about the natural world] and (3) I want to know what the heck is going on with this bird: I think it's weird that it's progressive whitening like Bill describes. I mean, I can see a certain region of the cardinal embryo mutating a gene (which subsequently gets copied & copied) leading to albinism in certain portions of the body (which then remain constant over the bird's life), but I find it truly odd that the area lacking pigment has increased over time. That's remarkable! If anyone has any insights into this "rare bird," let's hear it...

Labels: birdies, evolution, nova

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

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


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


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


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

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


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


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


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


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

Labels: fossils, geology, glacial landforms, montana, msse, structure

In case you haven't yet heard the news, the school shooting that took place yesterday afternoon at Northern Illinois University's Dekalb campus was in a geology class. I don't know what class, but it was in a "large lecture hall" (CNN) and the instructor was apparently a graduate student (Washington Post). The shooter was apparently an ex-sociology graduate student (Post). I can't imagine how awful that must be. There have been plenty of previous school shootings (unfortunately), but hearing that it was in a geology class really clarified in my imagination the horror of such an event unfolding.

NIU's website with updates.
More from The Washington Post.
More from CNN.

Labels: geology, news

In the spirit of the day, check out this article about mating at the National Zoo, here in DC (and a literal stone's throw from my apartment window).

Among the information featured:
when two females cheetahs are housed together, one or both females will shut down their ovulation, which makes it impossible to breed them until they are again separated.

Shanthi, the baby Asian elephant (who's now almost as big as her mom), was the result of artificial insemination. I remember visiting the Zoo shortly after Shanthi was born, and seeing video footage of her birth. Wow! Kablooey! That's a big package to drop!

The male Panamanian golden frog (pictured), which is extinct in the wild, will attach itself to the female for up to 120 days to make sure he's the one to fertilize her. Talk about clingy!

Also, you may be interested to know that some lowland gorillas will mate face-to-face, as the Wildlife Conservation Society reported this week, and was subsequently promoted by National Geographic.

Labels: dc, evolution

A cool feature from Google Maps allows users to create individualized maps with content centered on specific locations. They call them "My Maps." This maps are then viewable in any HTML browser. Check out the "Earth As Art" demonstration map, or this "Oral Histories of Route 66" map for examples of the kind of stuff that you can do with "My Maps." You can also watch the video about how to create them.

It occurs to me that My Maps might be a good way to share geologic knowledge about outcrop locations. One thing that I found frustrating and limiting in my first few years of teaching was that there was no good single source to go to find out about relevant outcrops. It took time and experience to find out where the cool rocks were. Is it a good idea to put this information online in a publicly-accessible format so beginning instructors and interested students/amateurs can visit interesting outcrops? (I sure would have appreciated it four years ago!) Or does that run the risk of letting rockhounds and less-than-ethical geovandals onto previously-secret locations? Is there a benefit to the ancient barriers in outcrop-information flow? Is it better to pass this information on from wise elder to trusted neophyte?

Labels: google, maps, teaching, tech, websites

A new paper in Water Resources Research suggests that Lake Mead, Nevada, may be dry by the year 2021. Authors Tim Barnett and David Pierce (both of Scripps) base this austere prediction on two things: (1) increasing projected rates of water use in the American southwest, as well as (2) climate change projections which suggest the region will receive less precipitation. They also posit a 50% chance that the lake level will drop too low to allow hydroelectric power generation by 2017. That's only 9 years from now!

It would seem that it's time for some conservation measures. When I lived out in California, I was struck by a major design flaw in the aqueducts which transport water from reservoirs in the Sierras and the Colorado River system to the centers of population: they're uncovered! These big long uncovered troughs full of water encourage the active evaporation of much of the liquid they carry. I'd imagine that just putting some tarps over the top of them would make a huge difference in conserving water that would otherwise be lost to the atmosphere. Maybe this has already happened: I left California in 1998, and I recall some post-September-11 (2001) talk about how the aqueducts were susceptible to being poisoned, so maybe they've already been covered up in the name of homeland security.

Check out the picture of the lake in October of last year (by Ken Dewey of the University of Nebraska). A glaring white "bathtub ring" shows how much the lake level has dropped due to the recent string of drought years the west has experienced. In early July, at the end of our Grand Canyon rafting trip, my Dad and brothers and I will float into the upper reaches of Lake Mead, and we'll likely see something like this in person. I'll be sure to post a blog reaction to that when I see it.

Reference:

Barnett, T. P., and D. W. Pierce (2008), "When Will Lake Mead go Dry?," Water Resour. Res., doi:10.1029/2007WR006704, in press.

For more details on the new study, see the press release on Eurekalert.

Labels: global warming, grand canyon, water resources

Labels: canada, fossils, humor, tv

A cool new pterosaur fossil was reported this week in the Proceedings of the National Academy of Sciences. Like so many interesting fossils of recent years, it's come out of China's Liaoning Province, which must be one big Lagerstatte. Unlike previously discovered pterosaurs, it had strongly curled toes, which indicate that it spent some of its time in trees, clutching cylindrical branches. It's small, too: really small, with a wingspan of only 25 cm, about the same as a barn swallow. Even so, it appears to be related (in a basal, primitive way) to the largest pterosaurs that ever lived, giants like Quetzalcoatlus.

Labels: china, fossils

Starting today, DC police are monitoring live images from surveillance cameras in many parts of the city. The District has 73 cameras, with live feeds from 54. The Washington Post published this map showing where they are (supposedly the locations were chosen in historically high crime areas). They also have an article about the new system. My 'hood of Adams-Morgan gets two, it looks like...

Anyhow, I always love maps, so I thought I'd share this one.

Labels: dc, maps

For Christmas a couple of years ago, I gave my family the black death, ebola, flesh-eating Strep, and stomach ache. Lest you think me some horrible person, I should point out that all of these nasty afflictions were represented by cute plush toys, courtesy of Giant Microbes. A picture of their version of E. coli (a.k.a. "food poisoning") is shown at left. They even have a toy version of the "bacterium" found in Mars meteorite ALH 84001!

I recently got an e-mail from the Giants Microbes people, and it reminded me of their unique products. I think they're great, and I just thought I'd pass that on. Several years ago, when I took a cross country road-trip, a Shigella bacterium from Giant Microbes was the Westy's trip mascot. Choose your microbe, folks. Make sure you wash your hands after playing with them.

Labels: evolution, products

A friend forwarded me a link to this interesting article in Mother Jones. After reading my discussion of Prius-induced fuel-conscious driving techniques on this blog, my friend recollected the Mother Jones profile subject, Wayne Gerdes, who gets 59 m.p.g. just by driving really, really consciously. He includes some maneuvers in his repertoire that are pretty dangerous, but the point is that he doesn't even need a hybrid to acheive these sorts of fuel efficiencies. Check it out.

Labels: oil, prius, products

Last night, we went to see the final night of the Banff Mountain Film Festival's world tour, held at National Geographic's headquarters in downtown DC. If you're not familiar with it, the BMFF is an annual event showcasing films about nature and extreme sports. Last night we watched films about rock climbers, kayakers, skiers, and snow-kiters. Oh, and a badger (see video online).

This year's festival was advertised using the image at right, of a climber doing a route on what's called the Totem Pole, located in coastal southern Tasmania, Australia. I'd never seen an image of this thing before, but it's pretty impressive. Does anyone know anything else about it? Via Google, I've seen it described as both a "dolerite column" and a sea stack. I'd like to know more. And I'd like to see it. And I don't want to climb it. Yikes.

Labels: australia, movies

Saw this video yesterday on the "How Stuff Works" website. It shows a crazy number of mammoth fossils being unearthed in Siberia (due to thawing of the permafrost there). I was kind of astonished how casually the fossils were being treated: at one point, a Russian scientist takes two mammoth teeth and grinds them together with vegetation in between, to demonstrate how they chewed. This strikes me as kind of rough treatment for specimens like this.

Labels: fossils, global warming, tv

Labels: alaska, travel

OK, if you watch LOST and haven't seen this week's episode yet, then go do something else. Honestly, what are you doing reading geology blogs anyhow?? There are more important things to be doing... Like catching up on LOST.


(Are you gone yet? DON'T KEEP READING. I warned you. Don't.)


For those of you who watch LOST, umm, wow. Thursday night was what the season opener should have been. Major new insights, major new questions. And: son of a gun, some of them have geological tie-ins. Who'd-a thunk it?


I mean, those of us who've made it through Season 2 know that the island has a weird magnetic anomaly, a feature which not only crashed Oceanic flight 815, but also apparently shields the island from outside observation. Geotimes even wrote a piece on this geological plotline. At the end of Season 2, a team of (apparently) polar scientists in the employ of Penny Widmore even remotely detect a magnetic pulse from the island.


Among the new insights from this week's episode: the location of a sunken Oceanic 815, complete with tail section and wedding-ring-less pilot Greg Grunberg. And not only is it discovered by robotic submersibles, but they show a map of a major subduction zone to show where they found the plane. (See below for a screen capture.) But is it really the real Ocean 815? Or a decoy? Regardless, when was the last time the Sunda Trench appeared in a fictional TV show?