Highly Allochthonous

Is tweeting bad for blogging?

Category: bloggery

It's been pretty much a year since I first climbed aboard the Twitter bandwagon, and I've been musing of late of how it has gone from being something I didn't really get at all, to becoming a fairly central part of how I interact with the Internet. It's usually where I first get wind of big events (the Haiti earthquake, for example), it guides me to interesting news both within and without the world of science; and it keeps me up to date with the doings and thoughts of a lot of my online friends. But, I realise, not all of them, and I am starting to wonder if a problem is brewing - a disconnect between those who choose to tweet, and those who do not. Thus I've been thinking fairly seriously about what effect my changed online habits have had in my interactions with the world of blogs, particularly the geology-centric part of it. There have certainly been changes that may potentially have had a negative impact: whereas before I used to check my aggregated geoblogging feed over breakfast, now I'm much more likely to check my Twitter feed. Time I might have spent writing a comment on somebody's post might now be spent writing a tweet (or retweet) about it instead - which might drive some traffic to said post, but does potentially divorce some of the conversation about a post from the post itself (and by extension, the author).

Read on »

Posted by Chris Rowan at 4:04 PM • 15 Comments

Stuff I linked to on Twitter last week

Category: links

Google Maps alphabets
http://www.telegraph.co.uk/technology/picture-galleries/5757548/The-Google-Maps-alphabet-UK-an-A-to-Z-of-the-British-Isles.html
http://www.telegraph.co.uk/news/picturegalleries/howaboutthat/5214494/Rhett-Dashwoods-Google-Maps-alphabet.html

NOVA Geoblog reviews "Reading the Rocks" by Marcia Bjornerud [adding to Amazon wish list in 3..2..]
http://nvcc.edu/home/cbentley/geoblog/2010/02/reading-rocks-by-marcia-bjornerud.html
(via @Geoblogfeed)

More geotagging propaganda:
http://geofroth.org/?p=475
[You can do things like this
(via @drjerque)

The Other California: Be a Geotripper Geoblogger for a Day! Crowd-sourced geoblogging!
http://geotripper.blogspot.com/2010/02/other-california-be-geotripper.html
(via @Geoblogfeed)

Shell's David Hone on iPad vs CRU pseudoscandal: We love tech, but science not so much...
http://tinyurl.com/ydssrnh
(via @mtobis, @EnergyCollectiv)

Icy volcanic breccia [as in, ice clasts WITHIN volcanic breccia...]
http://nvcc.edu/home/cbentley/geoblog/2010/02/icy-volcanic-breccia.html
(via @Geoblogfeed)

Renaissance of Technicolor dinosaurs continues. Last week's researchers were "in the Stone Age".
http://scienceblogs.com/notrocketscience/2010/02/the_renaissance_of_technicolour_dinosaurs_continues_and_the.php
(via @edyong209)

New maps of Pluto! Best until New Horizons within 6 months of 2015 flyby
http://www.nasa.gov/mission_pages/hubble/science/pluto-20100204.html
(via @elakdawalla, @plutokiller)

How can we bridge between geologic and human timescales to help avert disaster? Read AGU's Haiti blog:
http://www.agu.org/blog/Haiti/?p=48
(via @theAGU)

Free access to AGU papers on Caribbean plate for a limited time.
http://www.agu.org/news/archives/2010-02-02_CarribeanPlatePapers.shtml
(via @theAGU)

OK, that's pretty darn cool : Termite Mounds from Space: Myrmecos Blog.
http://myrmecos.wordpress.com/2010/02/04/finding-termites-on-google-earth/

Must-red Eureka column on science and journalistic balance by @markgfh.
http://www.timesonline.co.uk/tol/news/science/eureka/article7011355.ece

Why the denial camp is winning (and we're all losing) the climate wars.
http://scienceblogs.com/islandofdoubt/2010/02/why_the_denial_camp_is_winning.php?utm_source=selectfeed&utm_medium=rss
(via @ScienceBlogs)

Searching for Africa's Last Glaciers in the Mountains of the Moon, Uganda.
http://www.e360.yale.edu/content/feature.msp?id=2237
(via @highlyanne, @YaleE360)

Cool, if small, picture: Fukutokuoka no Ba Undersea Volcano Erupts.
http://mdn.mainichi.jp/mdnnews/news/20100204p2a00m0na017000c.html
(via @GeologyDotCom)

Some nice photos of dikes that fed Deccan flood basalts, India.
http://suvratk.blogspot.com/2010/02/plumbing-beneath-deccan-volcanic.html

Excellent post at Eruptions setting recent Yellowstone eq swarm in context. All structure, no magma.
http://scienceblogs.com/eruptions/2010/02/the_structure_of_calderas.php

To end this week's space budget discussions on a cheerier note: Cassini Mission extended until 2017. Huzzah!
http://www.nasa.gov/mission_pages/cassini/whycassini/cassini-20100203.html

Ediacaran animal trails? Evidence of 'anemone-like' movement in 565 Myr rocks from Newfoundland
http://www.sciencedaily.com/releases/2010/02/100203085914.htm
(via @geosociety)

Single-celled organism grows into 'monstrous beach ball' 20 cm diameter. A single cell!
http://www.newscientist.com/article/dn18468-zoologger-living-beach-ball-is-worlds-largest-cell.html
(via @rowanNS)

Wind abraded ventifacts on Mars and Earth: IAG Planetary Geomorph image of the month.
http://www.psi.edu/pgwg/images/feb10image.html
(via @highlyanne)

Wow. Another incredible Hubble image... of an asteroid collision in space!
http://blogs.discovermagazine.com/badastronomy/2010/02/02/hubble-captures-picture-of-asteroid-collision/
(via @DiscoverMag, @BadAstronomer)

Airborne Radar Image of Post-Quake Haiti . Some interesting background: 40km fault rupture, propogating W from epicentre.
http://www.jpl.nasa.gov/news/news.cfm?release=2010-037

If civilisation collapses, how much of our knowledge would future humans be able to retrieve? Not much...
http://www.newscientist.com/article/mg20527451.300-digital-doomsday-the-end-of-knowledge.html
(via @rowanNS)

Such an important point: Writers are Made not Born
http://serc.carleton.edu/earthandmind/posts/born.html

Simulations suggest rocky Earth-mass worlds could have formed in Alpha Centauri binary system. But in what orbits?
http://www.newscientist.com/article/dn18451-what-alien-worlds-orbit-our-nearest-star.html

Chemistry Creates Self-Stirring Liquids (w/video). Wonder if this relevant for core/mantle?
http://www.wired.com/wiredscience/2010/01/self-stirring-liquids/
(via @ScienceSoWhat)

Something rotten in the state of palaeontology. Decay removes acquired characters first. Interesting!
http://www.nature.com/news/2010/100131/full/news.2010.45.html/ [subscription only]
(via @NatureNews)

Online gallery for geology & art exhibit. Interesting, wish was more description of pieces.
http://www.twowallgallery.com/geosapiens.html
(via @clasticdetritus)

Posted by Chris Rowan at 6:30 AM • 1 Comments

Man-made mud volcano starting to look like a real volcano

Category: Lusi • geohazards

It's been a while since my last update on Lusi, the allegedly/probably drilling-triggered mud volcano near Sidoarjo, Indonesia. But the NASA Earth Observatory has just released this image, taken last autumn:

Lusi,October 2009. Source: NASA Earth Observatory

My first thought on seeing this was, "Woah, where'd that mountain come from?" In the last images I had seen, Lusi had from above was effectively a big muddy pool, contained within man-made earthworks, with a steaming vent in the middle. This had been pretty much the case for the previous couple of years.

Lusi, October 2008. Source: CRISP

Now, it's a big muddy pool with a big steaming hill in the middle. By looking through the satellite snapshots put out every couple of months by the Centre for Remote Imaging, Sensing and Processing at the University of Singapore (of which the October 2008 image above is one), you can see that over the last 12 months or so Lusi appears to have started building up instead of out, with the causeways and dams around the vent being gradually swallowed up by the grey ooze.

Lusi, May 2009. Source: CRISP

Lusi, September 2009. Source: CRISP

Lusi, December 2009. Source: CRISP

It seems, then, that Lusi has entered a new phase of its life. I wonder if this growth has anything to do with subsidence in the area?

Geotagging (View all geotagged posts)

Posted by Chris Rowan at 12:55 PM • 5 Comments

Haiti's seismic future

Category: earthquakes • geohazards • geology

It's now been just over 3 weeks since a magnitude 7.0 earthquake hit Haiti, devastating the capital Port-au-Prince and many other surrounding towns and villages. The sheer scale of the disaster - the tens, even hundreds of thousands who have lost their lives, or their homes and families - has been quite overwhelming. As the country struggles to recover and rebuild, and with aftershocks still occasionally shaking things up, one question that people want answered is, are we safe yet? When is the continued seismic activity going to stop? Will there be another devastating earthquake in the future - and if so, when? And what about the rest of the northern Caribbean?

Let's start with the aftershocks. When a fault ruptures, the surrounding crust will be deformed by the motion. The upper crust is brittle, so will accommodate this deformation by rupturing at further points of weakness like minor faults and fractures, causing aftershocks. As of February 2nd, there have been 62 significant aftershocks powerful enough to be picked up by the global seismograph network. The USGS provide a handy map (which is being updated over time; this is a static snapshot):

Source: USGS

If we plot the frequency of aftershocks over time, we see that the vast majority occurred in the 24 to 36 hours following the main shock (which occurred quite late on the 12th January). This period also included about 15 aftershocks with a magnitude greater than 5, whilst there has only been one (a magnitude 5.9) since.

This makes sense: most of the response to the local redistribution of stress in the crust following a large earthquake will occur almost immediately, as weak points are pushed beyond their point of failure. But there will be some places where stress was increased almost to the point of failure, but not quite over it, and will finally fail a bit later. This means that although there doesn't seem to have been a significant aftershock for a week (although there were probably smaller ones that weren't properly picked up by distant seismometers), there's still the risk of a strained part of the crust finally giving, producing a sizeable aftershock, for some time yet. Which is why this USGS assessment predicted, based on statistical modelling of the aftershocks in the week or so following the mainshock, 2 or 3 aftershocks of magnitude 5 or greater would occur in the 30 day period after 21st January, with a 25% chance of a magnitude 6 or greater aftershock.

However, focussing on just the aftershocks ignores what seems to be the real concern about future seismic risk in Haiti: namely, that only an approximately 40 km long segment of the Enriquillo Fault ruptured on January 12th, and in the same way that stress redistribution around the ruptured section causes aftershocks, stress transferred onto adjacent, and as yet unruptured, sections of the Enriquillo Fault might well trigger large earthquakes on them. This worry has a precedent. In the aftermath of the magnitude 9.0 Boxing Day 2004 Sumatra earthquake, John McCloskey and his colleagues at the University of Ulster calculated that this rupture had placed more stress on the subduction megathrust further to the southeast. Less than a month after publishing a warning of the increased seismic hazard, there was a magnitude 8.7 earthquake in the area in question. It seems that a similar process may possibly be at work in Haiti; here's a map of the stress changes resulting from the January 12th earthquake, as modelled by Eric Calais (I originally found this on a brilliant collection of scientific imagery for the Haiti earthquake being collated by the Group on Earth Observations). Note that the aftershocks (circles) are clustered in the red areas indicating the largest stress increases, but also note the stress increases in the region surrounding the Enriquillo fault both to the east and the west.

Modelled stress changes for the Jan 12 earthquake: thick line marks the modelled rupture length.

As always when talking about triggering earthquakes, it is important to emphasise that this is just giving already strained bits of crust an extra nudge that might cause them to rupture a bit earlier than they otherwise would. The worry comes from the fact that these fault segments might just have enough strain stored up on them to be primed for such triggering. The historical map below shows that a large section of the Enriquillo-Plantain Garden Fault system running through southern Haiti and the neighbouring Dominican Republic last ruptured in a sequence of earthquakes concentrated in a 20 year period between 1750 and 1770, meaning that prior to January 12th, more than 250 years' worth of tectonic movement between the North American and Carribean plates (or, more precisely, the fraction of that tectonic motion that is accommodated by this fault) was being stored as elastic strain across the Enriquillo fault.

Source: New York Times

Eric Calais was co-author of a 2008 paper (pdf) that used GPS measurements to estimate the rate that strain was building up on the Enriquillo fault, extrapolated from that the total elastic strain accumulated on the Haitian part of the fault zone since the last big earthquake, and calculated that if it was all released in a single earthquake, it would have had a magnitude of approximately 7.2. Some of that strain has now been released by the magnitude 7.0 three weeks ago, but it might be less than you instinctively think: the earthquake magnitude scale is logarithmic, so a magnitude 7.2 earthquake represents about 1.6 times more energy than is released by a magnitude 7.0 earthquake. This leads to the conclusion that the unruptured parts of the Enriquillo fault, particularly the part to the east of January's rupture (which is still very close to Port-au-Prince), still represent a significant seismic hazard.

Another look at the earthquake history of Haiti and the Dominican Republic also reveals a second potential earthquake hazard. The northern Septentrional Fault System seems (from current, GPS-derived, deformation patterns), to accommodate just as much tectonic motion as the Enriquillo system. The part of the Septentrional Fault that runs through Haiti last ruptured in 1842, and has built up enough strain to potentially cause a magnitude 6.9 earthquake if it all ruptured in one go. But there are no historically recorded earthquakes on the part that runs through the Dominican Republic, and paleoseismic studies (which look for disruption of datable horizons in trenches dug along the fault) indicate it probably last ruptured almost 1000 years ago. If that's right, there's enough strain stored up on this section to cause up to a magntiude 7.5 earthquake.

To sum, up then, despite January's quake releasing a fair amount of the strain built up at the plate boundary, there's still plenty more yet to be released in this part of the Caribbean. Seismologists can't really predict if the recent earthquakes have increased the chances of this remainder being released sooner rather than later; more data is definitely required about how the crust has responded to the last month of shaking and stress changes, both through close study of comparative radar imagery (several examples are up at the Group on Earth Observations site), and getting on the ground to make more GPS measurements. However, what should not be ignored is that regardless of the details, this region is always going to be at risk from these sorts of earthquakes. The strain still being stored on the Enriquillo and Septentrional faults is going be released at some point in the decades to come, and it's just a question of when, and how (multiple ruptures, or one big one?). But even then, the danger will not disappear - the slow yet inexorable motion of the North American and Carribean plates will place strain across these faults again - including the segment that caused so much carnage three weeks ago - and eventually they will rupture again. After that, the earthquake cycle will restart once more until they rupture again, and again, and again. The tectonic rhythms of our planet are slow, and a few hundred years of inactivity on a fault is a mere eyeblink when its lifetime can be measured in hundreds of thousands, even millions, of years.

Whilst geologists can not - and may not ever - be able to predict exactly when an earthquake will hit, we are getting to the stage where we know where they are most likely to strike, and roughly how big and how frequent they are likely to be. The northern Carribean is seismically active, and will remain so until what is, for us, an unimaginably distant point in the future. Making the people who live there aware of the seismic risks is important: even after 50 years pass and last month's tragedy fades from the Haitians' memories, geologists need to press home the fact that it will happen again, and people should plan and build - and live - accordingly.

Geotagging (View all geotagged posts)

Posted by Chris Rowan at 2:50 PM • 5 Comments

What is a manned space programme actually for?

Category: general science • planets • ranting

Today President Obama announced that in his next budget he was going to cut funding for NASA's Constellation Program, and with it the plan to send people back to the Moon. This is no doubt going to lead to a lot of noisy protest; but I can't help wondering if it isn't the correct decision, because I was never entirely clear on what, exactly, they were going to do when they got back to the Moon beyond a "well, gee, we're on the Moon!" and we managed that 40 years ago. In fact, the story of the Apollo program contains a salutary lesson about the consequences of gearing your space programme totally around the simple goal of reaching somewhere: once you've got there, that's it.

It's normally around this stage of an argument about manned space flight that someone plays the "inspiration" card. But I can't remember when I was last inspired - really, truly, left awestruck - by something an astronaut did. The most exciting thing that I can recall any of them doing in the last couple of decades is fixing up the Hubble Space Telescope three times, and the inspirational bit came from what Hubble did after it had been made even better than before. Most of the time the astronauts just head up to the International Space Station, stay in orbit for a few months, and then come back home again. They take the odd pretty picture, it's true, but what's their primary function? Yes, we get more data on the effects of long-term zero gravity on human physiology, but are they really doing anything that wasn't being done on Mir 15 years ago? I can't help feeling that - much as it pains me to admit it - they're there just so the ISS seems like a bit less of an orbiting albino pachyderm. Either way I would bet a fair sum that more people currently know the name of a valiant little Mars rover than know the names of the current astronauts on the ISS. Because Spirit has done things.

From this, you might reasonably conclude that I'm completely against the idea of sending people into space. I'm not: I'm just against the idea of doing it on the cheap. If we're going to revisit the Moon, and go on to Mars or near-Earth asteroids, it shouldn't be just to commit the worst form of checklist tourism - to go just so that we can say we've been. It should be with a purpose - with the aim of actually doing something new and interesting whilst we're there, or at least as part of a wider strategy of establishing a useful human presence in space beyond the tiny and impotent foothold we maintain at the moment. That would be inspirational. But I suspect that it would also be much more expensive than I think we're willing to countenance right now - and, more importantly, probably beyond our current space technology.

But perhaps I'm wrong about all this. What do you see as the point of manned space flight right now? What point do you think it could have?

Posted by Chris Rowan at 7:40 PM • 25 Comments

Coal and the fossil record of climate change in the Canadian High Arctic

Category: Cenozoic • by Anne • climate science • environment • fossils • photos

For more than 55 million years, Ellesmere Island remained in one place while the world around it changed. Fifty-five million years ago, verdant forests grew at 75° North latitude. These wetland forests, [comprised] of species now primarily found in China, grew on an alluvial plain where channels meandered back and forth and periodic floods buried stumps, logs, and leaves intact. Today the forests are preserved as coal seams that outcrop on the edges ...[of] modern Ellesmere Island, [where] there are no forests, and the tallest vegetation grows less than 15 cm high. Large parts of the area are polar desert, subject to intensely cold and dark winters and minimal precipitation.

These are the opening lines to my M.S. thesis, in which I contrasted the Paleocene-Eocene and modern hydrological environments of Stenkul Fiord, on southern Ellesmere Island in the Canadian Arctic Archipelago. My thesis goes on to describe a world that no longer exists, except in the fossil record preserved at sites in the High Arctic. This former world may provide clues as to how polar flora and fauna and their physical environment responded to global mean surface temperatures that were 2-4 degrees warmer than they are today, yet are right in line with the predictions for the end of this century. These clues, recorded in the fossil and stratigraphic record in coal and sediment layers on remote Ellesmere Island, well north of the northernmost civilian settlement in North America, are under attack. The same human demand for energy for that is driving up global temperatures is threatening to erase the very fossils that record polar life under a warmer temperature regime. The government of Canada's Nunavut territory is currently considering claims by Westar Resources, Inc. to mine the coal beds in one of the most spectacular of all the fossil localities in the High Arctic.

During the Paleocene and Eocene, tropical vegetation extended to 50° N, and broad-leaved evergreens reached 70° N. There was no permanent polar ice, and large parts of the polar regions were covered by forests dominated by cypresses and angiosperms. Fossilized remnants of these forests are found in locations such as Spitsbergen, Greenland, the Yukon, northeastern Asia, and the Canadian Arctic Archipelago. This widespread Arcto-Tertiary forest nearly disappeared as the climate cooled over the past 30 million years and modern temperate forests. Today the last remnants of this flora are preserved in the mountains of China's Sichuan province.

Among the signature trees of the Arcto-Tertiary fossil record is the Metasequoia, a genus which was thought to have gone extinct in the Miocene until an isolated grove of Metasequoia glyptostroboides, or dawn redwood, was discovered in Sichuan in 1944. Metasequoia grows to 60 m tall and unlike sequoias, it is deciduous and loses its leaves in the winter. This would have been quite handy for life in the High Arctic, where in the Paleocene-Eocene winter temperatures might have hovered just above freezing, but would still have been dark for six months of the year.

At the site where I worked on Ellesmere Island, there were large Metasequoia logs and tree stumps still rooted in situ in the coal layers. Picking apart the coal layers, I could pull out Metasequoia leaves, twigs, and male and female cones. The siltstones between the coals preserved beautiful fossil impressions of a variety of tree leaves and stems.

My field site on Stenkul Fiord yielded only plant fossils, and for now, is safe from the development plans of Westar Resources and the Nunavut government. But a bit north at Strathcona Fiord, plants are second fiddle to the best vertebrate fossil locality of the Canadian High Arctic. At Strathcona Fiord, the fossil record shows that those Eocene forests were inhabited by alligators, giant tortoises, primates, tapirs, and the hippo-like Coryphodon. There have been over 40 papers published on the Eocene fossils of Strathcona Fiord alone. It's not just the Eocene that makes Strathcona Fiord an amazing fossil locality either. Pliocene layers at Strathcona Fiord have yielded plants, insects, mollusks, fish, frog and mammals such as black bear, 3-toed horse, beaver, and badger. It is the only known Pliocene Arctic site with vertebrate remains.

Strathcona Fiord is one of three sites where Westar Resources, Inc. plans to mine the coal. Mining the coal will permanently destroy the embedded fossils and the possibilities for any additional discoveries at this site. The other two Ellesmere Island areas in which Westar has applied for mining permits are the Fosheim and Bache Pennisulas. We don't know as much about the paleontology of these areas, but the little work that has been done on the Fosheim Peninsula has already discovered Eocene leaf beds and Pliocene fossils.

Paleontologists and geologists around the world are raising their voices in opposition to the proposed coal mining at Strathcona Fiord and the other sites on Ellesmere Island. The Society of Vertebrate Paleontology has issued a press release expressing concern and urging the preservation of the fossils resources. There is also a coordinated letter-writing campaign to the Nunavut Impact Review Board. I've just sent a letter to the review board, which I've appended below. If you are a paleontologist, paleoclimatologist, geologist, Arctic lover, fossil lover, or otherwise moved by the incredible story of alligators and towering trees at 75° N, I urge you join me in writing to the government of Nunavut and encourage them to at least require more study of the localities before mining is approved. Letters can be sent electronically to info@nirb.ca.

To the members of the Nunavut Impact Review Board,

I appreciate the opportunity to write to you concerning the proposed Westar coal project on Ellesmere Island. I am a geologist at the University of North Carolina at Charlotte, and my research focuses on the intersection of hydrology, landscapes, and climate. My graduate M.S. thesis research focused on the paleo-environments of the Eureka Sound Group exposed at Stenkul Fiord on southern Ellesmere Island. I used the coal and sediment layers, and the fossils they contain, to understand variability of hydrological environments that existed in the Arctic 55 million years ago. Today, I work on issues of water and modern climate change, but my perspective was profoundly influenced by the time I spent on Ellesmere Island walking amidst the coal layers and fossilized tree trunks.

The proposed activities by Westar Resources, Inc. could damage or destroy fossil sites that form an important part of Nunavut's history and environmental legacy. These fossils tell us about the history of Arctic plants and animals, and they are recognized internationally for their scientific importance. They also provide important evidence from a time when Earth, especially the Arctic, was warmer. The fossils of the Ellesmere Island sites proposed for mining by Ellesmere Island provide clues as to how polar flora and fauna and their physical environment responded to global mean surface temperatures that were 2-4 degrees warmer than they are today, yet are right in line with the predictions for the end of this century. Ultimately, I hope that evidence from Nunavut's fossil record can help us better estimate and prepare for future climate change.

If the fossil sites in the Westar coal project areas are destroyed the evidence is lost forever, therefore I recommend that the Nunavut Impact Review Board advise the Minister, pursuant to article 12.4.4(a) of the Nunavut Land Claim Agreement, that the project proposal requires review under Part 5 or 6. I believe that much more paleontological and paleoclimatic research can be conducted at these sites before any coal is extracted from them and we lose the opportunity to learn all that we can.

I thank you for your consideration, and request that you keep me informed of the results of this screening process.

Geotagging (View all geotagged posts)

Posted by Anne Jefferson at 1:26 PM • 14 Comments

Where I've been

Category: bloggery • conferences • outcrops • photos

It's been a bit quiet around these parts since I posted on the Haiti earthquake. Those of you following me on Twitter know that at that point I was actually spending a few days exploring New York: its parks, its almost stupidly tall buildings, and its rather nifty natural history museum.

Central Park, in which I was a lone stroller in a sea of joggers.

From the Empire State Building, the rest of Manhattan looks like a model village.

Very cool rocks on display at the American Museum of Natural History: samples of the 4 billion year-old Acasta Gneiss (oldest known bit of Earth's crust) and Jack Hills Conglomerate (contains oldest known, 4.4 billion year-old zircon crystals).

A fair amount of artistic license has gone into this particular fossil exhibit...

After that, I headed onwards to North Carolina. The chief purpose of my US visit was to attend the ScienceOnline 2010 conference, of course, but it was also a chance to catch up in person with my talented hydro-coblogger Anne Jefferson, who hails from Charlotte. I spent Friday in her department (probably totally confusing her hydrologist and geographer colleagues with a talk about the wonders of palaeomagnetism), before she drove me over to Raleigh-Durham and Sigma Xi for the conference itself.

Last year, I indulged in some conference blogging; this year Twitter served as my primary means of online note-taking. Whatever the wider value of conference tweeting, I find that two or three 140 character points from a session is enough to distil the major points, without distracting me too much from events at the podium. I also had my own Sunday morning session discussing geospatial data and other geoscience web applications to prepare for, although I fully confess that my co-convenor Jacqueline Floyd was more responsible for the coherence and value of the session than I was (and I must also give a special shout out to Cameron, Christina and the other participants for what turned out to be a good discussion in the unconferenced part of the session).

I had a good time at the conference: I especially enjoyed the sessions on promoting diversity in science (which Anne expertly helmed, and drew upon the very interesting results of the woman geoscientists and blogs survey), rebooting science journalism, reporting from the Great Pacific Garbage Patch, and Web Science (study of the web, rather than with the web). It was also nice to share a room, and great conversations, with so many online friends and colleagues: Ed, Arikia, Janet, Zuska, Brian (whose promise to send me a copy of his book I will remember!), Scicurious, Pal, KevinZ, Miriam, Bora (of course), and many, many others. However, in the aftermath Anne and I both mused over the fact that just as the boundary between new and old media (or bloggers and journalists) becomes ever more blurry, so this conference has become less of a blogger meet-up and more of a media conference, with the requisite evolution in feel and focus. I'm not passing judgement on this, although part of me (with my little niche geology blog) feels a bit left behind by this mainstreaming of the online science community. Nonetheless, this will not stop me doing my best to return next year.

The end of the conference did not mark the end of my time in North Carolina, as I persuaded Anne to spend her Martin Luther King Day on a little field trip into the foothills of the Appalachians. Fortunately our chosen destination, Caesar's Head State Park, was well furnished with both rocks (a granitic gneiss, if you must know) to divert me, and waterfalls to appease her. Also, as the park is perched on the edge of the Blue Ridge escarpment, there were some rather fabulous views for us both to enjoy, particularly as our excursion coincided with a fabulous mini-warm spell.

Caesar's Head.

Raven Cliff Falls

The view from Caesar's Head

Sadly, my fun could not last, and by Wednesday I was back in a somewhat less sunny UK. But at least this means that some more posts may appear in the not to distant future.

Posted by Chris Rowan at 3:35 PM • 2 Comments

Tectonics of the Haitian earthquake

Category: earthquakes • geohazards • geology • tectonics

A magnitude 7.0 earthquake struck Haiti this evening, causing extensive damage to the capital, Port-au-Prince, and probably causing many casualties. The map below shows where the main shock occurred (red), as well as the epicentres of the numerous aftershocks (orange) that occurred in the following 5 or 6 hours (and continue even as I write).

The main shock appears to have initiated less than 25 km southwest of Port-au-Prince; this close proximity meant that the city would have endured the maximum possible shaking intensity from an earthquake of this size, leading to extensive damage. Here's the focal mechanism, courtesy of the USGS:

With the help of my recent post on focal mechanisms, it is hopefully obvious that the rupture occurred on a primarily strike-slip fault, with the crust on each side of the fault moving horizontally relative to the other side. To understand why there is strike-slip faulting in this area, we need to step back, and look at a simplied map of the entire Caribbean:

The Caribbean is contained on its own separate little plate; a rather diminutive part of the tectonic jigsaw that is the Earth's crust. It is surrounded on three sides by the much larger North and South American plates, both of which are moving approximately westwards with respect to the Caribbean plate at around 2-3 centimetres a year. On the eastern edge of the plate, the boundary runs perpendicular to the direction of relative plate motion, so there is compression and subduction (and subduction volcanism, exemplified by the likes of Montserrat). However, as the boundary curves around to form the northern boundary of the Caribbean plate, where the Haitian earthquake occurred, it starts to run parallel to the direction of relative plate motion, making strike-slip faulting along E-W trending faults the most likely expression of deformation in this region. This is exactly what the Haitian quake appears to record.

Note also that deformation across the northern plate boundary appears to be distributed - some motion is accommodated on faults that are located a little bit away from the actual plate boundary, further inside the plate interior. The Haitian quake appears to have occurred on one of these faults: based on the position of its epicentre the rupture is extremely close to the Enriquillo Fault, which appears to be a major strike slip fault running across the southern end of Haiti. This is the fault most likely to have ruptured.

Tectonic map of the Northern Caribbean (Source)

There is nothing particularly unusual about this earthquake given the tectonic context. Unfortunately, however, Haiti is a very poor country - one of the poorest and least developed in the world - so unfortunately, its government was not in a position to really do much to prepare for the inevitable large earthquake, leaving tens of thousands to suffer the consequences.

Geotagging (View all geotagged posts)

Update from Anne: Chris has been featured in a Nature News Briefing: "The Haiti Earthquake in Depth" along with more information about the faults in question and the known seismic risk of the area.

Further update: I've written a follow-up post that discusses the risks of further large earthquakes in the North Caribbean.

Posted by Chris Rowan at 1:30 AM • 69 Comments

Geospatial data and the web (#scio10 preparation)

Category: fieldwork • general science • geology

After busting my gut in the last couple of weeks to put out 12 posts in 12 days - and many thanks for the positive feedback, both public and private, that I've received for the series - it's now more than time to look ahead to the fast approaching ScienceOnline 2010 conference. Amongst all the fantastically interesting sessions and discussions on offer, I'm co-chairing a session with Jacqueline Floyd entitled Earth Science, Web 2.0+, and Geospatial Applications.

For people working in geology and other field sciences like oceanography and ecology, the geographic context, and the 2D or even 3D spatial distribution of our data, is often extremely important, and the ability to store, access and visualise this information using web tools is gradually developing. This therefore seems like the ideal time to get a dialogue going about how web and social media tools might be used to distribute, use, and in the latter case even generate, geospatial datasets. I am hoping with this post to get some discussion going here which can feed into the session next weekend, but Jackie and I are also hoping that the conversation will continue in the next few months, with some moves towards realising some of the ideas that seem to be floating around this subject in the geoblogging community (and beyond). We believe that the discussion can be focussed around three questions:

• What's available? With help from other geobloggers, I've been trying to compile a list of currently available geospatial datasets. Even though it's still far from comprehensive - please feel free to suggest any additions, either on the wave, the wiki or in the comments here - it does show that quite a lot of interesting data available on the web already. However, availability doesn't necessarily mean usability, so we'd also like your thoughts on the good, the bad and the ugly of the nascent geospatial web. By contrasting good sites where data are easily and intuitively accessed and visualised (something like ClimateWizard springs to mind), against sites where getting the data is still a bit fiddly (such as the USGS earthquake search page, which is a stark contrast to a lot of its offerings), we can try to identify 'best practices' which would be useful when developing geospatial resources in the future.

• What would you like to see? What data are not available that could/should be? This could be in terms of specific datasets, or in types of data - should we be geocoding papers, blog posts, photos? In the second case, I have been playing around with this idea, but it's still a bit ad-hoc. As a subsidiary question, there is also the issue of what other contextual tagging is required in addition to geocoding (e.g., age is just as important in many geological contexts).
• What tools are we missing?. If the geospatial web is going to take off, we need to make more user-friendly tools to encode, access and visualise geospatial data sets, so that people not familiar with the inner workings of web protocols will use them. We need easy searching, perhaps using a graphical map interface where you can select areas you want to search for data in. We need ways of integrating different data sets into the same visualisation (perhaps through broad mash-ups like a Google Earth geology layer or the excellent, if tightly focussed GeoMapApp). And there is also the prospect of the ability to construct new geospatial databases from geotagged data harvested from the web - crowdsourcing efforts like the USGS's Twitter Earthquake Detector, and the #uksnow twitter aggegator demonstrate two different ways of collecting data with a geospatial component. There's probably all sorts of other data you could collect in a similar fashion: but how can we make it easy for people to submit data? What I'd like to see is some sort of generic app that makes allows you to add geocoded photos/notes/voice memos/videos/other data such as structural to a specified feed that can then be viewed on Google Maps/Earth - either a personal one for a particular field trip project or a collective one for crowdsourcing projects. Perhaps a bookmarklet for your browser that allows you to geocode things you encounter on your browsing via a map interface.

  One potential consideration here is that there may be a difference between using such data for simple sharing, and possibly using it for research. What is required to make web-harvested datasets scientifically useful? For example, how to you determine the accuracy of the location provided? How to you filter out bad or irrelevent data?

I'll be interested to hear everyone's thoughts and ideas - remember, even if you can't make the session, you can still help to make the discussion more fruitful there, and give it some momentum in the aftermath.

Posted by Chris Rowan at 5:00 PM • 4 Comments

Anne's picks of the December literature

Category: by Anne • climate science • geochemistry • geomorphology • hydrology • paper reviews • planets

I'm a few days behind on sharing my picks from December's journals, but Chris has been doing such a stupendous job of sharing absolutely wonderful geology posts (and of deconstructing terrible science reporting), that I hardly feel guilty waiting until he's occupied with travels before sneaking this post onto the blog.

Without further ado, here is the odd assortment of articles that hit my email box in December that I found most intriguing. They reflect a mixture of my past, present, and future research and teaching interests and should not be considered a reflection of anyone else's tastes in science.

Burbey, T.J. (2010) Fracture characterization using Earth tide analysis, Journal of Hydrology, 380:237-246. doi:10.1016/j.jhydrol.2009.10.037

Tides are popping up all over in the geology literature these days, from the Slumgullion earthflow (atmospheric tides) to the San Andreas fault (earth tides). Here Burbey uses water-level fluctuations in fractured rock confined aquifers to quantify specific storage and secondary porosity. Fractured rock aquifers are notoriously tricky to understand, and this method gives hydrogeologists one more tool in their arsenal for understanding places like the Blue Ridge Mountains and the Piedmont. Since I'm getting interested in the fractured rocks in just those areas, this paper caught my eye.

Burnett, W.C., Peterson, R.N., Santos, I.R., and Hicks, R.W. (2010) Use of automated radon measurements for rapid assessment of groundwater flow into Florida streams Journal of Hydrology, 380:298-304. doi:10.1016/j.jhydrol.2009.11.005

Radon is a conservative tracer with concentrations several orders of magnitude higher in groundwater than surface water. That means that it can be used to evaluate the groundwater inputs into different stream reaches, though it is often used in conjunction with other tracers to get quantitative estimates. In this paper, Burnett and colleagues lay out a method for using radon as a sole tracer to quantify groundwater discharge. I'm looking around for tracers to separate overland flow, flow through the soil/saprolite, and groundwater from rock fractures, so this paper piqued my interest as radon is one candidate I'm learning more about.

Garcia-Castellanos, D., Estrada, F., Jiménez-Munt, I., Gorini, C., Fernàndez, M., Vergés, J. and De Vicente, R. 2009. Catastrophic flood of the Mediterranean after the Messinian salinity crisis. Nature, 462, 778-781, doi:10.1038/nature08555.

5.6 million years ago the Mediterranean basin was nearly dry and highly saline in the midst of a period known as the Messinian salinity crisis, but 5.33 million years the Atlantic Ocean rapidly refilled the basin by overtopping and incising through the sill at the Straits of Gibraltar. How fast did that sea refill? How big was the peak discharge? And what did all that water do the straits itself? Those are the questions tackled in this paper, which combines borehole and seismic data with hydrodynamic and morphodynamic modeling. The story that Garcia-Castellanos and colleagues tell as a result of their work is truly astounding. The Atlantic Ocean overtopped the sill and slowly began to refill the Mediterranean, but as the sill eroded, discharge (and incision) increased exponentially until peak discharges on the order of 10⁸m³/sec were reached and sea levels in the Mediterranean were increasing by up to 10 m per day. While the beginning and the end of the flood may have stretched out for thousands of years, the modeling work suggests that the vast majority of water transfer and the incision of greater than 250 m deep canyons across the Straits of Gibraltar was done on a time scale of several months to two years. That peak discharge is ten times greater than that estimated for the Missoula Floods, themselves not trifling events, and there may have been profound paleoclimate repercussions from such a significant change in the region's hydrological status.

Grimm, R. E., and S. L. Painter (2009), On the secular evolution of groundwater on Mars, Geophys. Res. Lett., 36, L24803, doi:10.1029/2009GL041018.

Grimm and Painter created a 2D pole-to-equator model of subsurface water and carbon dioxide transport, initiated the model by simulating sudden freezing, and then looked at the effects over geologic time scales (secular evolution). According to their abstract, their model predicts water to be found in different places on the Martian landscape than previous ideas had suggested. I guess we'll just have to go look and see who is right.

Jiang, Xiao-Wei; Wan, Li; Wang, Xu-Sheng; Ge, Shemin; Liu, Jie Effect of exponential decay in hydraulic conductivity with depth on regional groundwater flow Geophys. Res. Lett., 36, L24402, doi:10.1029/2009GL041251.

In soils and in the Earth's crust, hydraulic conductivity (K) generally decreases exponentially with depth. This phenomenon is the result of the compaction and compression of the overlying strata. In this paper, Jiang and colleagues examine the implications such decreases in K on local versus regional groundwater flow systems. They find that the more quickly K decreases, the less water makes into the deeper regional flow systems and local flow systems extend deeper into the subsurface. They suggest that when hydrogeologists try to interpret regional flow problems, that we need to bear in mind the effects of decreasing K on the systems.

Knight, D.B. and Davis, R.E. 2009. Contribution of tropical cyclones to extreme rainfall events in the southeastern United States. J. Geophys. Res., 114, D23102, doi:10.1029/2009JD012511.

Knight and Davis used 25 years of observational, wind-corrected, and reanalysis data for the southeastern Atlantic coastal US states and found that extreme precipitation from tropical storms and hurricanes (TCs) has increased over the study period. They find that this increase in TC contribution to extreme precipitation is a function of increasing storm wetness and frequency, but not storm duration. If TCs are producing more precipitation, their flood hazards are also increasing, and flooding is already the leading cause of deaths associated with TCs.

Meade, R.H. and Moody, J.A. 2009. Causes for the decline of suspended-sediment discharge in the Mississippi River system, 1940-2007. Hydrological Processes. 24, 35-49. doi:10.1002/hyp.7477

Dams on the Missouri and Upper Mississippi Rivers have been blamed for trapping almost 2/3 of the sediment that used to reach the Lower Mississippi and Delta. Here, Meade and Moody show that the dams are only trapping half of the missing sediment, while engineering practices such as bank revetments and meander cutoffs, combined with better erosion control practices in the drainage basin, probably account for the rest. Meade and Moody suggest that this river system, in the largest basin in North America, has been transformed from transport-limited to supply-limited, which is a pretty amazing fundamental shift in the behavior of the river and its ability to deliver sediments to the Gulf of Mexico. [Note that there's another article in the same issue on "A quarter century of declining suspended sediment fluxes in the Mississippi River and the effect of the 1993 flood." Both articles are in the public domain and not subject to US copyright laws, though there doesn't seem to be an obvious way to take advantage of that from the Wiley website.]

Neumann, R.B., Ashfaque, A.N, Badruzzaman, A. B. M., Ali, M.A., Shoemaker, J.K., and Harvey, C.F. 2010. Anthropogenic influences on groundwater arsenic concentrations in Bangladesh, Nature Geoscience 3, 46-52. doi:10.1038/ngeo685

The story of groundwater of southeast Asia's deltas, where tens of millions of people live at risk of arsenic poisoning from their drinking water, is perhaps the most compelling contemporary scientific story of how geology, geomorphology, hydrology, and humans intertwine. It's also an extremely complicated story, with arsenic-laden sediment from the Himalayas settling in the deltas , irrigated rice fields and ponds changing the local groundwater flow patterns, and microbially mediated oxidation of organic carbon driving the geochemical release of the arsenic into the groundwater. This story has been being pieced together in many papers in the last several years, and in this paper Neumann et al. show that groundwater recharge from the ponds, but not the rice fields, draws the organic carbon into the shallow aquifer, and then groundwater flow modified by pumping brings the carbon to the depths with the greatest dissolved arsenic concentrations. Add some biogeochemistry data, isotope tracing of source waters, incubation experiments, and 3-D flow modeling, and this paper adds some important elements to our understanding of how this public health risk came to be - and how we might be able to mitigate the risks for the people who have little choice but to drink the water from their local wells. [Also note that the same issue of Nature Geosciences has another article on "arsenic relase from paddy soils during monsoon flooding" as well as an editorial, commentary, backstory, and news and views piece on the southeast Asia arsenic problem.]

Pritchard, D., G. G. Roberts, N. J. White, and C. N. Richardson (2009), Uplift histories from river profiles, Geophys. Res. Lett., 36, L24301, doi:10.1029/2009GL040928.

In rivers that have adjusted to their tectonic and climatic regimes, the long profile of a river is smooth and concave. The interesting places are where river profiles don't look like that ideal. This paper interprets river longitudinal profiles as a way to understand the tectonic uplift history of the area, through a non-linear equation. They check their interpretation against an independently constrained uplift history for a river in Angola.

Stone, R. 2009. Peril in the Pamirs. Science 326(5960): 1614-1617. doi: 10.1126/science.326.5960.1614

Dave Petley at Dave's Landslide Blog has the must-read summary of this article on the risks associated with the giant lake impounded by the world's tallest landslide dam. This is seriously fascinating stuff. I already talked a bit about the Usoi Dam in my dam-break floods spiel in my Fluvial Processes class, and now I have more ammunition for this year's crop of students. In the same issue of Science, Stone also summarizes some of the other water issues facing Central Asia.

Please note that I can't read the full article of AGU publications (including WRR, JGR, and GRL) until July 2010 or the print issue arrives in my institution's library. Summaries of those articles are based on the abstract only. UNC Charlotte also does not have access to Nature Geosciences.

Posted by Anne Jefferson at 5:28 AM • 2 Comments