Check out these amazing images of the ashy flood deposits from Chaiten volcano that have buried Chaiten town. The Volcanism Blog, by the way, is extremely consistent in quality and focus, and I tip my hat to them for doing such a great job. If you haven't already discovered that site, you should spend some time checking out their other posts too.

Labels: blogs, south america, volcano

And here's the view hiking back down the canyon to the car:

It's a classic U-shaped valley, the signature of alpine glacial topography. Here's the Google Maps "terrain" view of this valley:

View Larger Map

Labels: glacial landforms, montana, volcano

Last night I attended my first meeting of the Potomac Geophysical Society (PGS). The PGS meets on Thursday nights, and I usually can't make it because I teach on Thursday nights. (I do however attend meetings of the Geological Society of Washington quite regularly, but those are on Wednesday nights.) Now that the semester is over, I was able to make it to the final PGS meeting of the spring.

The meeting was held at Fort Meyer Officer's Club. It's on a military base adjacent to Arlington National Cemetery, and before entering, my Prius had to be searched for bombs (as did all other civilian vehicles). The Officer's Club was about what you would expect, I guess -- kind of 1950's decor, elegant once. I noticed they had compact fluorescent light bulbs in all the sockets, which pleased me. PGS meetings consist of: (1) beer downstairs in the lounge, (2) dinner upstairs in the "Campaign Room," (3) business details, and (4) a talk by a guest speaker.

Last night's speaker was Bill Burton, from the USGS's volcano hazards and monitoring program. Bill's office will be launching a comprehensive new volcano website later this year, and he gave us a brief preview of its features in last night's talk. If you'd like a look for yourself, they have a beta version of the site online now.

Labels: gsw, meetings, pgs, volcano, websites

Holy cow! Chaiten is continuing to erupt, and witnesses are posting some incredible photographs of the event.

I highly recommend you check out these two sites, which I am only aware of thanks to James Annan who posted the links at his Empty Blog.

Seriously: check them out. It's like Independence Day down there.

Labels: news, south america, volcano

Whoa! Chaiten volcano in Chile has been erupting for a few days. It's a big'un: Argentina's getting some ash from its extrusive neighbor. Check out the coverage on the volcanism blog, or via NASA's Earth Observatory. UPDATE: also from the volcanism blog.

Labels: south america, volcano

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

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

It's funny how one thing leads to another. In promoting our Climate Change Symposium on Friday, I wrote to Cerphe (pronounced "Surf"), probably the best DJ in the world, who's on air in the afternoons on 94.7 The Globe, our DC-area "world-class rock" station that also features a green message. Cerphe wrote back, saying he'd get some mentions on the air this week, and also mentioned that his wife has a small business building green homes. I noticed that the business is headquartered in Bentonville, Virginia, out in the Shenandoah Valley between Massanutten Mountain and the Blue Ridge. And it occurred to me that I've looked at a bentonite layer out there in the Valley (see photo), not too far away from Bentonville. Bentonite is a common clay mineral that in stratigraphic layers is usually interpreted as weathered volcanic ash. (The one pictured above is possibly the "Big Bentonite" that accompanied the onset of the Ordovician Taconian Orogeny in eastern North America.) Could it be that bentonite is named for Bentonville, Virginia? Well, Wikipedia tells me that "The absorbent clay was given the name bentonite by an American geologist sometime after its discovery in about 1890 ...after the Benton Formation in Montana's Rock Creek area." So that took me to the entry on Fort Benton, Montana, which was named for the first 5-term U.S. Senator, Thomas Hart Benton. He was an advocate of westward expansion by the United States, the idea that later was dubbed "Manifest Destiny." So: as near as I can follow, bentonite is a mineral named for a place, which is in turn named for a man. What this has to do with world-class rock and climate change is anybody's guess.

Labels: appalachians, history, montana, volcano

It appears that researchers have located a volcano under a thick mantle of Antarctic ice. They found the volcano's approximate position by mapping a layer of ash and glass shards within the glacial ice. The volcano erupted in or around 325 B.C., say Hugh Corr and David Vaughan, based on their study. (Both men work for the British Antarctic Survey.)

They initially detected the layer of volcanic debris through airborne radar-reflectance measurements. (At first they thought the reflective layer was the bedrock at the bottom of the ice, since it provided such a strong reflection.) Then they looked at the thickness of snow overlying this layer and correlated the ash deposit with eruption-linked acid-rich snow strata in ice cores that were taken in adjacent areas. The image here shows the radar-wave reflectance profile.

(According to my rough calculations, the vertical exaggeration of the cross-section is about 6x. )

This has been billed as the first time we've seen clear evidence of a volcano pushing its way up through the ice sheet in Antarctica, though similar eruptions have been observed in historical times in Iceland (like Grimsvotn in 2004). However, just this past weekend I watched an episode of the PBS series NOVA, which showed scientists working on a big ice coring project near what they interpreted to be a sub-ice volcano. There was a big depression, and ice was flowing into the depression (downhill) from all directions. Ergo that ice had to be going somewhere. NOVA's scientists posited it was being melted, and that meltwater was greasing the skids of the bottom of multiple ice streams which were cruising out of that area of the ice sheet. (These ice streams are just faster-flowing areas of the ice sheet, like currents zooming through ocean water, sometimes 50x as fast as the "background" rate of flow.)

The show got me thinking about another study, coincidentally also published in Nature Geoscience, although this one was in the inaugural January issue. It's a study of the Kennicott Glacier, in Alaska's Wrangell-St. Elias National Park:

The study was conducted by three researchers, all associated with the Institute of Arctic and Alpine Research: Timothy Bartholomaus, Robert Anderson & Suzanne Anderson. They measured a bunch of variables on the Kennicott Glacier, seeing which of them correlated with a rise in the glacier's speed. They found that an annual flood event from Hidden Creek Lake (HCL in part d of the diagram, orange line) occurred at the same time as the glacier's maximum speeds during the measured interval, the maximum discharge of the (downstream) Kennicott River, and a maximum electrical conductivity of the water in the Kennicott River (the bedrock beneath the glacier is halite-bearing). As this whopper of a graphic shows, Not only does the glacier speed up its horizontal motion during the flood (part b), but the whole thing actually rises up vertically too! (part c) Also, Donoho Falls Lake (DHL in part d of the diagram, blue line) downstream experiences a huge surge in water as the flood passes over it. Conductivity spikes during this same interval. Bartholomaus and the two Andersons propose that when the ice dam of the lake gives way and all that water surges into the glacier's channel, it overwhelms the capacity of the sub-glacial network of channels & raises the pore pressure of water within the ice. This extra pressure "inflates" the space between glacial ice & underlying bedrock, and the whole thing slides like an air hockey puck. At least, as long as the super-high pressure lasts. Once the flood ebbs, pore pressure in the glacier drops back down to levels that are easily counteracted by friction. The glacier slows once more to a "normal" pace.

This is very reminiscent to me of studies done on how an increase in pore pressure along a fault plane can trigger movement along that fault. When I took structural geology in college, the professor described an example from Colorado (I think) where the Army (I think) was injecting nerve gas down into the ground to get rid of it. The nasty nerve gas was dissolved in water, and the periodic injections of this solution correlated with a series of earthquakes (movement) along a previously-unknown subterranean fault. The injections increased fluid pressure in the pore space of the rock, and that "inflated" the space between the fault blocks, and the relatively minor shear acting on them was then enough to get the two to slide. I won't get into the whole Mohr Circle here, but I do recommend you check out the famous Beer Can Experiment to get an idea of how an increase in fluid pressure can cause an otherwise "stuck" fault to slide. Anyhow, I guess the base of a glacier is essentially a big fault, with one kind of rock below and another (ice) above. Same phenomenon, in other words, but different geologic context.

The Bartholomaus + 2 Andersons study also has some big global warming implications. The recent surge noted in Greenland's glaciers (e.g. Zwally, et al., 2002) may be explained by higher rates of surface melting (due to elevated Arctic air temperatures) which then produces lots of meltwater, which flows down through the glaciers to the bottom via meltwater channels which plunge through the ice. Via the mechanism explained above, the great ice sheet atop Greenland is reduced more rapidly than without the surface melting. One of these meltwater channels was featured prominently on the cover of the June 2007 issue of National Geographic.

So, with that, I think I'll end this blog post -- my thoughts went from volcanoes to ice streams & subglacial meltwater to fault slippage to global warming. I reckon that's just about enough... just about... but I also noticed something else...

A tangent about publication: The Corr & Vaughan findings will be published in the second issue of the new spinoff journal Nature Geoscience, but they were posted online over the weekend in advance of the actual print publication of that issue. An article in the New York Times alerted me to the study. I'm not surprised that Nature, like the Proceedings of the Royal Society, has taken to hatching specialty sub-journals to convey more articles each month. (An "about the journal" page appears on their website, if you're curious.) The image shown here with this post is from the Times, not the actual Nature Geoscience article.

References:
Hugh F. J. Corr & David G. Vaughan. (2008) "A recent volcanic eruption beneath the West Antarctic ice sheet." Nature Geoscience. Published online: 20 Jan. 2008. doi:10.1038/ngeo106

Timothy C. Bartholomaus, Robert S. Anderson & Suzanne P. Anderson. (2008) "Response of glacier basal motion to transient water storage." Nature Geoscience 1, 33-37. Published online: 20 December 2007 doi:10.1038/ngeo.2007.52

H. Jay Zwally, Waleed Abdalati, Tom Herring, Kristine Larson, Jack Saba, & Konrad Steffen. (2002) "Surface melt-induced acceleration of Greenland Ice-Sheet flow." Science 297, 218-222. doi: 10.1126/science.1072708

Also see:
Kenneth Chang. "Scientists find active volcano in Antarctica." The New York Times. Published online: 21 Jan. 2008.

Labels: antarctica, global warming, tv, volcano

Geological travels in Northern Ireland, part II:

Mammatus clouds hanging over Lough Erne, in western Northern Ireland. Our friends Jodie and Rory have a caravan on this large lake. After our tour of the cathedrals of Armagh, Jodie drove us out here to have a hike at the lake (which was great in spite of ending in darkness and rain) and to rest up in their modish accomodations there.













This is Mount Slemish, an eroded volcanic neck in Northern Ireland near Antrim. This "basalt plug" was once the center of a volcano which erupted lava all over this vicinity. Because the massive basalt in the volcano's "throat" was tougher than the surrounding stratified rock layers, it stood up strongly to erosion, and now rises to 1,457 feet (437 m) in elevation, dominating the local landscape.

Labels: clouds, northern ireland, slemish, volcano