A visual estimate of the proportions of mixtures: pumice vs. lithics

When a volcano erupts explosively, the tephra that comes out is a mixture of material that was molten at the time and bits of other old, cold rock that happened to get caught up in the blast.  These are referred to as the juvenile and the lithic components and consist of bubbly, pumice-like fragments and of chunks of lava and hydrothermally-altered material, respectively.

Lithic-rich deposits from the explosive Hekla 4 eruption. The yellow-grey-white grains are juvenile pumice, the dark grains are lava lithics that were caught up in the eruption. I reckon that there are up to 40% lithics here. How about you? Click to enlarge.

The relative proportions of juvenile and lithic grains can tell us something about the eruption.  For example, if the deposits are full of lithics, it might indicate that the vent where the material was erupting was getting wider or that underground water was coming into contact with the magma and turning explosively into steam, breaking up the surrounding rocks in the process.

The best way to measure the relative proportions of juvenile and lithic grains in a sample is to get out the tweezers and separate them by hand, but this is often impractical, and a lot of time a visual estimate is sufficient.  Visual estimates are a lot better if you have some known values to compare them with.  That’s where the chart comes in.

Visual estimates of the proportions of mixtures

The following chart gives examples of what mixtures of different proportions look like.  Download it, print copies, use it whenever you need to make visual estimates of proportions of mixed materials.

A chart demonstrating the visual appearance of mixtures of different proportions. Click to see the full-size version, or use 'Right-click, Save As...' to download a copy.

Make your own charts

The charts were made using the Python programming language.  The source code is given below so that you can make and customise your own plots.  If you are learning Python, try messing around with the code.  First try changing the numbers and sizes of grains; next change the number of plots and give the grey grains different shapes to the black ones; finally, try plotting mixtures of 3 different grain types, each with different size distributions.  Happy hacking!

import numpy as np
import matplotlib.pyplot as plt

number=1000
x = np.random.rand( number )
y = np.random.rand( number )
percentages=[1, 2, 5, 10, 20, 30, 50, 75]
fig = plt.figure(figsize=(8.27,11.69))

for i in range(8):
    percent=percentages[i]
    black = np.round( percent*(number/100.0) )
    color = np.array( black*['black'] + (number-black)*['lightgrey'] )
    np.random.shuffle(color) #randomise so black aren't all at the bottom
    # define a marker shape here to make something that looks more like rocks
    marker=[(0.17,0.12),(0.15,0.42),(0.14,0.75),(0.35,0.87),(0.68,0.90),
            (0.98,0.86),(0.90,0.29),(0.72,0.14),(0.45,0.05),(0.17,0.12)]
    ax=plt.subplot(4,2,i+1)
    plt.scatter(x, y, color=color, s=60, linewidth=0.25, edgecolors='black',
                marker=(marker,0))
    plt.xlim(0,1)
    plt.ylim(0,1)
    plt.title('%i%% black' % (percent), fontsize=12)
    ax=plt.gca()
    ax.xaxis.set_ticklabels([])
    ax.yaxis.set_ticklabels([])
plt.subplots_adjust(left=0.05, right=0.95, bottom=0.05, hspace=0.15, wspace=0.1)
plt.suptitle('Visual estimates of proportions of mixtures', fontsize=18, y=0.97)
plt.suptitle('http://all-geo.org/volcan01010/2012/09/pumicelithicsproportions',
             x=0.95, y=0.045, horizontalalignment='right',
             verticalalignment='top', fontsize='x-small')
plt.savefig('PumiceLithicsProportions.png', dpi=150)
plt.ion()
plt.show()
Categories: Uncategorized

Ten swimming pools of travel chaos

An article published this week reveals the volume, grainsize and eruption rate characteristics of the tephra (volcanic ash, pumice and other materials) erupted during the eruption of Eyjafjallajökull in 2010.  This information is important because these are the inputs needed by computer simulations to predict where ash from an eruption is likely to be dispersed.  It is also interesting because the volume of ash that caused all that travel chaos in Europe turns out to be surprisingly small.

Ten swimming pools?

The group of scientists, led by the University of Iceland, combined measurements of tephra deposited on the ground, meteorological data, satellite data and theoretical models of ash dispersion to work out how much tephra was produced at the volcano at different times during the eruption, and to where it was dispersed.  I helped out with measurements of ash deposition across Europe.  The results were published as open access, so you can download the article and read them for yourself here.

The total mass of erupted tephra was 480 million tonnes.  Most of this landed in Iceland, however, and only a tiny fraction (0.02%) of this made it as far as mainland Europe.  This ash consisted of tiny grains of pulverised rock between 1 and 50 millionths of a metre (microns) across.  For comparison, an individual red blood cell is about 6-8 microns in diameter.

Now, a cubic metre of dense Eyjafjallajökull magma would have a mass of about 2.6 tonnes.  It would look like rocky grey washing machine, but with no door.  So if you compacted all the ash in Europe back into a single lump, it would have a volume of 36,000 cubic metres.  This would form a cube with 33 metre sides.  It would look like a rocky grey 11-storey building, but with no windows.

To continue in the Olympic spirit, we can calculate how many swimming pools this would fill.  The standard competition pool is 50 x 25 x 2 m, but the one in London was actually 3 m deep, so that waves would be reduced and the swimmers could go faster.  The volume is therefore 3750 cubic metres.

This means that, theoretically, all the travel chaos of Eyjafjallajökull was caused by magma with a volume of only ten Olympic-sized swimming pools.

This seems unbelievable, but remember that huge volumes of air get sucked through jet engines, so even low ash concentrations can quickly add up to trouble.  Airlines now have to take special measures if the concentration exceeds two thousandths of a gram per cubic metre, so to keep aeroplanes out of your swimming pool needs only 7.5 grams of tephra.  That’s about a quarter of a teaspoon.

EDIT (30 Aug 2012): Of course, the chaos wasn’t caused by the ash itself, but by the rules that stopped planes from flying where the ash might be.  These were changed as the Eyjafjallajökull 2010 eruption was ongoing, and the 2 milligrams per cubic metre limit was introduced.  This means that you can now have a much more powerful eruption in Iceland, but with much less disruption.

In fact, we already have: http://all-geo.org/volcan01010/2012/04/an-icelandic-eruption-100-times-more-powerful-than-eyjafjallajokull/

Categories: Uncategorized

Iceland horse fun

Ever the practical joker, Dobbin thought it would be hilarious to rohypnol the water trough…

Iceland horse fun

Click for large version

Categories: Uncategorized

Fieldwork update: Progress map, river crossings and bulldozers

This is a quick post to let you know how the fieldwork is going so far.

Sampling the distal deposits of Hekla’s largest eruptions since the ice age

The aim of my project is to sample the deposits of the two largest explosive eruptions from Mt Hekla since the end of the ice age.  The tephra (pumice + ash) from these eruptions is found all over Iceland, as well as across mainland Europe.  The measurements made this summer will be combined with analysis of the samples to give us a much better idea of what these eruptions were like (e.g. how high the plume reached, how much very fine ash was produced).  Then we can work out the likely results if it happens again.

Because the ash is all over Iceland, I have had to go all over Iceland, as the map shows.

Photo locations for the first 7 weeks

The map was created using the information stored in 'geotagged' photos. The colour of the dots tells when the photo was taken, and the map shows everywhere that I have been in the first 7 weeks. Click to enlarge.

The first two months were very successful, as Iceland has had record-breakingly good weather.  I’ve had a number of babysitters who have come and looked after me along the way, including Al Monteith, who blogged about his time here.  His blog has lots more detail and photos of what we have been up to: http://alasdairmonteith.blogspot.com/2012/07/iceland-round-up.html

Iceland by converted ambulance

My home for my time in Iceland is a Volkswagen T4 Synchro van. It used to be an ambulance, and still has medicine cabinets, a bracket for hanging a saline drip, and the switch to turn on the siren (which has disappointingly been disconnected).  The daily routine of wake, eat, drive, dig, drive, dig, eat, drive, dig, drive, dig, cup of tea, drive, dig, eat, computer, whisky, sleep is a very efficient way of covering the ground.  Additional buy food, buy petrol, hot tub! mixes things up a bit.

As well as being fairly large and very comfortable, the van is also very capable, as the video beneath shows.

Pumice, pumice, pumice

The aim of the first part of the summer was to check that the ash covers as much of Iceland as was previously thought (it does), and to collect lots of samples of it (248 so far).  I had a few days at home this week, where I had my only 3 nights sleep under a roof since late May, and a few days in Reykjavik sorting out repairs and supplies.  Now we are all set to head back out to the field tonight.

This time the aim is to sample material closer to the volcano.  This is where most of the material fell, including thick deposits of pumice.  It’s hard work digging the holes to find the bottom when there is so much material, but if you ask nicely, sometimes you can get a helping hand.

Categories: Uncategorized

Glacier of the mountains of the islands

Everyone has heard of Eyjafjallajökull. Not everyone can pronounce it.

It is almost as infamous for its long name than for the travel disruption that it caused. But the name is much easier when you break it down into its component parts. These are Eyja (islands), fjalla (mountains) and jökull (glacier). The origin of each part is clear when you see the volcano from the air.

Eyjafjallajökull from above

Eyjafjallajökull's name comes from the islands offshore, as seen in this view from above. Click for larger version.

The islands after which the volcano is named are the Vestmannaeyjar (or the Westman Islands). The largest is Heimay, where an eruption in 1973 partly buried a small town and the residents famously pumped seawater onto advancing lava flows in an attempt to divert their course. Out of view, below the bottom of the picture is the island of Surtsey, which was born out of the Atlantic during an eruption from 1963-1967.

In the upper right of the picture is the Myrdalsjökull glacier that covers Katla volcano. Since 2010, Katla has been more widely known as ‘that-volcano-next-door-that’s-even-bigger-than-the-unpronounceable-one’. Katla gets restless every summer, and is rumbling again now. You can see plots of earthquakes at the volcano over the last 48 hours (Icelandic Met Office) and over the last 2 years (Edinburgh University). It might erupt.  Or it might not.  The eruption might be bigger, but the disruption in Europe will probably be less than Eyjafjallajökull 2010, mainly because of changes to aviation rules.

Aeroplane-window geology

A tip for those flying from Iceland to the UK is to take a left-hand side window seat. If it is clear (if….), then you get spectacular views of lava flows, rivers, fault lines, glaciers and volcanoes all along the south coast of the country. Equally, chose a right-hand seat for flights from the UK. On summer evenings, these also provide the rare experience of seeing the sun rise in the (north) west.

This photo was taken in August 2011, on a flight from Keflavik to Glasgow. Erik Klemetti’s recent aeroplane-window pictures of Californian volcanoes on the Eruptions blog were the inspiration to post it now. I also wrote another aeroplane-geology-based post, On Transatlantic Flight, about a year ago.  It explains how the Atlantic ocean is actually younger than the fuel burned to cross it.

Categories: Uncategorized

On the geology of Prometheus

Contrary to the advice of pretty much everyone that has seen it, I went to see Prometheus at the weekend. A big reason for going was that I knew they had filmed part of it in Iceland. I had seen the film crews when I was working in the Hekla area last summer and I was curious to see how it looked on the big screen.

In the film, a spaceship lands upon the black rocky surface of a distant planet. The door opens and the crew drive off across the dusty waste to the alien base, with huge mountains towering above them on all sides.

How much of this is Iceland?

Futuristic all-terrain vehicles race across the dusty landscape of a distant and unfamiliar planet. Steep, dark peaks rise menacingly in the background.

Answer: The soil.

Only the soil is Iceland. A jagged lava flow (aa, or slabby-pahoehoe) covers the floor of the valley, and has since been partly-buried by repeated eruptions of ash and pumice from Hekla.

Everything above the flat plain is computer trickery.

A real-life active volcano

An old landrover races across the dusty landscape of our very own planet, Earth. Hekla rests peacefully in the background.

A look at real-life Hekla shows the part-buried lava landscape. It looks like the dust clouds from the vehicles that they used in the film were probably real. It looks like the mountains of Iceland, however, were not dramatic enough to make it into the film.

Hekla is one of Iceland’s most active volcanoes, with recent eruptions in 1947, 1980, 1991 and 2000. Each of these began explosively, producing pumice and ash (also called tephra), but quickly switched to producing lava. There have also been much larger explosive eruptions in the past, such as in 1104, which destroyed local farms, and two prehistoric eruptions about 3000 and 4000 years ago which covered most of the country in ash. Ash grains from these eruptions can be found in Scotland and Scandinavia.

Further reading

When Googling an image for this post, I came across an article on Alien Prequel News reporting that the Prometheus crew had also been filming in north Africa and the Middle East. It seems that the distant mountains, with their horizontal sedimentary layers, are sandstones from Wadi Rum, Jordan.

The Science Punk blog has a nice article (The Science of Prometheus) highlighting the logical flaws and plot holes of the film. There are many, including the one that annoyed me the most: how did the facehugger grow to giant size with no obvious food source?

See a bit more of Hekla, including the huge scale of the prehistoric eruptions, in a post I wrote about them during my fieldwork last year.

Categories: Uncategorized

Insight into climate debate at the Volcanism and the Atmosphere conference

Last week was the American Geophysical Union (AGU) Chapman Conference on Volcanism and the Atmosphere in Selfoss, Iceland. It covered topics such as explosive eruptions, satellite detection of volcanic ash, aviation hazards and climate modelling. Unlike larger meetings, where sessions run in parallel like the stages at a music festival, all the presentations happened in one room and everyone went to all of them. This way, instead of sticking to the geology sessions (normally filled with pictures of hammers in exotic locations), I saw a lot of talks from other fields. These included a lively debate about how the effects of volcanic eruptions are preserved in the tree ring climate record, which is the subject of this post.

Live tweeting from the conference

Much of the conference was reported live on Twitter.  You can find the conversation by searching for the hashtag #AGUVolcAtm.   After the speakers have agonized over their presentations in order to fit them into the 15 minute time slot, it’s fun to see them subsequently mashed into less than 140 characters by the audience. There are also 300 word summaries (abstracts) of the presentations available online here.

Volcanic eruptions and climate

The connection between volcanoes and climate is a result of the gases produced during eruptions.  These include sulphur dioxide and carbon dioxide. It is the sulphur dioxide (SO2) that provides the main influence on climate, as it reacts in the atmosphere to form sulphuric acid aerosol (H2SO4). An aerosol is a suspension of tiny solid or liquid particles in a gas. The sulphuric acid particles reflect incoming radiation from the Sun back into space. If the gas is injected into the stratosphere, the aerosol can remain aloft for years. In this way, large volcanic eruptions cool the surface of the Earth.  Of course, it’s a bit more complicated than I have just explained, and many of the presentations explored the details of the process.

Climatically speaking, volcanic carbon dioxide (CO2) is of minor importance, as the amount of gas that volcanoes emit is dwarfed by human emissions; the average annual global volcanic CO2 emission rate is equivalent to that of a moderately-sized country such as Poland. Other volcanic gases such as chlorine and fluorine have atmospheric effects such as breaking down ozone in the stratosphere.

Genuine climate debate

A highlight of the conference was a pair of consecutive talks by Michael Mann and Rosanne  D’Arrigo about the signals from past volcanic eruptions in the tree ring record. As a geologist, the exchange gave insight into the topics being debated at the cutting edge of climate science.

That debates exist between climate scientists is sometimes reported as an indication that the foundations of the whole field are unsteady, but this is a misunderstanding of how science works. Arguments over details are common, and indeed necessary to refine our understanding, but often reflect just a fragment of a bigger picture. Two palaeontologists may argue over whether Tyrannosaurus Rex had feathers, but both would agree on the bigger point that they share a common ancestor with the beast.

Here, both Mann and D’Arrigo agree on long term trends in the tree ring record (they must, because Mann’s study uses data produced by D’Arrigo) and that the Earth is warming. But each scientist’s passionate defence of their own ideas shows that consensus on the short term effects of volcanic eruptions on the tree ring record is yet to be reached. Both talks were clear, logical, detailed, and absorbed everyone in the room. This is genuine climate debate and it is fascinating to watch.

Underestimation of Volcanic Cooling in Tree-Ring Based Reconstructions of Hemispheric Temperatures

The <140 character version of Michael Mann’s talk is:

.@MichaelEMann: Tree rings miss volcanic cooling spikes. Cold limits growth, but diffuse light from atmos aerosol boosts it. #AGUVolcAtm

It described his recent paper that suggests that tree rings underestimate volcanic cooling. Mann used a computer simulated climate, which he had shown to do a good job of estimating the cooling effect of recent eruptions, to calculate global temperature from 1200-1980 (red line below). It shows clear spikes associated with eruptions in 1258, 1452, 1809 and 1815. He also plotted temperatures from the same period as estimated from studies of tree ring widths (blue line). The spikes are missing. The new study tried to explain why the tree ring data were underestimating the cooling and missing the spikes.

Figure from the Mann et al paper

Modified version of Figure 2d from the paper by Mann and coworkers published in Nature. Click to visit the journal.

The tree ring width data came from forests that are so high up mountains or so close to the poles that the trees are clinging on to life at the very edge of where trees can survive. The growth of such trees has been shown to respond more to temperature changes than to other effects e.g. rainfall. Mann and colleagues used equations describing tree growth at different temperatures to predict what the trees would record given the temperatures in the computer-simulated climate (green line). They included a threshold temperature below which growth stops, a description of how diffuse light caused by atmospheric aerosols can help trees grow, and random local variations in weather conditions.

The result is that the recorded cooling is reduced and, because the no-growth threshold resulted in some years with missing rings, the cooling appears delayed relative to the eruption. The calculated tree rings now show good agreement with the measured ones, leading Mann to conclude that his equations are describing real effects.

Volcanic Signals in Tree-ring Records for the Past Millennium

Next, Rosanna D’Arrigo took to the podium in defence of dendrochronology (tree ring dating) and launched into a point-by-point rebuttal of a number of Mann’s arguments. In 140 characters, it goes like this:

D’Arrigo: BOOM! Tree ring widths aren’t as good as density and diffuse effect was measured on different forest type to rings. #AGUVolcAtm

Her main point was that Mann’s use of tree ring width data was inappropriate, because tree ring width data are best suited to measuring longer-term trends in temperature. To look at volcanic cooling spikes, they should have used tree ring density data (maximum latewood density: MXD), which is more sensitive to short term changes. She described a study by Briffa and co-workers that picked up the cooling following the Tambora eruption in 1815. Mann had not mentioned this study in his paper.

D’Arrigo said that the diffuse effect was recorded in forests with a thick canopy, which is unlike the areas where the tree rings were measured. She also pointed out studies showing the trees can grow at temperatures below Mann’s threshold, and that the missing rings were less common than he had suggested.

The discussion continues

D’Arrigo and her fellow dendrochronologists have prepared a formal response, so the debate will continue, in full public view, in the pages of scientific journals. At the meeting, it spilled over onto Twitter, with Mann agreeing that tree ring density (TRD) measurements are better than widths (TRW), but that “TRW dominate tree-ring temp recons”. Unfortunately, tree ring density data is more difficult and expensive to collect.

From the sidelines, it doesn’t seem that the scientific problems are so serious. In time, more density measurements will be collected and the reconstructions will be improved.  Meanwhile, Mann’s ideas can be tested further and accepted or discarded depending on how well they stand up.  The real heat of the argument appears to result from Mann’s failure to emphasise that that tree rings CAN measure volcanic cooling spikes.  His study used tree ring widths because the data were most abundant, even though better methods exist. In the wider media, this made tree ring dating sound less useful than it is, which understandably annoyed the dendrochronologists.

Other highlights in 140 characters or less

Here are Twitter-sized summaries of some of the other talks at the meeting:

  • .@volcanofile: tropospheric volcanic sulphate -> whiter clouds -> global cooling. Better estimates of past emissions needed. #AGUVolcAtm
  • Alan Robock, Rutgers: 2011 eruption of Nabro, Eritrea, was largest sulfate producer since 1991′s Pinatubo. #AGUVolcAtm (sent by @alexwitze)
  • Foelsche: GPS signals between satellites bend as pass thru atmosphere; temperature controls bending -> can calculate atmos temp. #AGUVolcAtm
  • Foelsche: Now we need a big eruption to see if we can detect the effects. #AGUVolcAtm
  • Thor Thordarson: 560 cubic km of magma erupted in Iceland in last 11,000 years, since ice age ended. (That’s a lotta magma.) #AGUVolcAtm (sent by @alexwitze)
  • Miller: Baffin glaciers retreating -> 14C-date newly uncovered moss -> shows rapid lowering of snowline in 1450s -> LittleIceAge #AGUVolcAtm
  • Lavigne: named the 1257 (1258) ‘mystery’ #eruption but can’t reveal name due to ‘embargo’ I suspect … #AGUVolcAtm (sent by @volcanofile)
  • Lavigne misunderstands journal embargoes. Nature & Science v clear. Talks allowed. http://bit.ly/qD1lt3 http://bit.ly/KXcqEo #AGUVolcAtm (sent by @alexwitze)
  • Prata: If ash conc < 200 microns/m3, can’t really detect w/satellite, but that’s OK b/c it’s not that dangerous to planes. #AGUVolcAtm (sent by @alexwitze)
  • Prata: #Eyjafjallajokull yielded some 10 sci papers per teragram of ash emitted. #AGUVolcAtm (sent by @alexwitze)
  • Krueger: Strong eruption -> increased winds in Southern ocean -> limits transport to Antarctica -> reduced sulphate in ice core. #AGUVolcAtm
  • Elkins-Tanton: Siberian Traps magma chambers in hydrocarbon+evaporite basin -> adds extra S+Cl+F. To 3000000km3 basalt! Nasty! #AGUVolcAtm
  • Brian Toon: ‘noctilucent #clouds after large #eruptions could indicate that water was injected in stratosphere’ #AGUVolcAtm (sent by @volcanofile)
  • Graf: ‘romantic sunsets after big #eruptions … Need to watch birth rates … with implications for geo-engineering’ #AGUVolcAtm (sent by @volcanofile)

Other reports from the conference

Categories: Uncategorized

Happy Anniversary Grímsvötn

Yesterday was the first anniversary of the 2011 eruption of Grímsvötn.  Despite being the largest eruption in Iceland in 50 years, the day passed without much fanfare as the eruption had a relatively small impact compared to a certain other eruption the year before.  To understand why, read my post from the second anniversary of that one: An Icelandic eruption 100x more powerful than Eyjafjallajökull.

In this post, I want to point out the interesting effects that wind patterns had on the tephra dispersal from the Grímsvötn eruption, and to update you on the analysis of the samples.

Where to go: Greenland or Great Britain?

The US National Oceanic and Atmospheric Administration (NOAA) have a webpage where you can have a go at running their HYSPLIT atmospheric dispersion model.  This uses information on wind speeds and directions to predict where particles in the atmosphere will travel.  It works in forward or in reverse, so if you smell a bad smell, you can find where it came from and if you make a bad smell, you can see where it is going to go.  Except on a global scale.

The Grímsvötn 2011 eruption was interesting, because the final destination of the erupted material was controlled really strongly by the height that it reached in the plume.  Check out these two plots for comparison:

Material from 8ooo m goes north

HYSPLIT trajectory for particles released at 8000 m. These do not include particle settling, but give a good idea of wind direction. Material is carried north across Iceland, then across to Greenland.

Material from 4000 m goes south

HYSPLIT trajectory for particles released at 4000 m. These do not include particle settling, but give a good idea of wind direction. Material is carried south across Iceland, then across to Great Britain.

Where did the tephra go?

The plume from Grímsvötn reached 20 km in altitude, but it turns out that not all of this was tephra.  Much of it was steam and volcanic gas.  To see whether most of the tephra was in the upper or lower part of the plume, have a look at this photograph of the area south of the crater, taken on an monster-truck expedition to the crater last August.

A black sandy desert

A black sandy desert. This is the tephra deposit from Grímsvötn 2011 on top of the Vatnajökull glacier. All this should be white ice and snow. Click the image to read my post about a trip to the crater last summer.

It is clear from the deposits on the ground that most of the tephra from the eruption was carried to the south by low-level winds and was deposited from the lower part of the plume.  There was very little tephra deposited to the north of the crater, but material from the upper plume was carried carried to the north and was detected over Greenland by satellites sensitive to the volcanic gas sulphur dioxide (SO2).

This complicated dispersal of volcanic material is another reason why mapping volcanic ash clouds is HARD.  The main lessons that were learned are:

  • Tephra may not be distributed evenly throughout the full height of an eruption column during a subglacial eruption.
  • It is important to get information from the ground and from satellites as quickly as possible to refine computer predictions made during an eruption.

What happened to the samples?

Some of you may remember that during the Grímsvötn eruption, there was a request from the British Geological Survey for samples of ash collected by the public.  I made a video and wrote a post at the time called An easy way to sample falling ash, and another post showing some of the ash that fell in the UK.  In the end, we received ~130 tape samples from the public and found ash in many of them, particularly ones from Scotland (which is in nice agreement with the particle trajectories above).  The results are being written up, but it will still take months for them to be published formally.  Such is the pace of science.

Thanks again to everyone that sent samples in.

Categories: Uncategorized

EGU2012 Open Source Software in Geosciences

A splinter session yesterday drew a larger-than-expected crowd to talk about the use of free and open source software (FOSS) in the geosciences.  Those in attendance spanned the range from developers to end-users and the main outcome is that there will probably be a dedicated FOSS in science session at EGU2013.

A list of FOSS for geoscientists

A lot of the discussion yesterday was about open source software used in computer models (e.g. Glimmer-CISM, a community-written model of ice sheet dynamics).  Examples of more general use of FOSS in geosciences are using GRASS and QGIS instead of ArcMap, Python instead of Matlab, Inkscape instead of Illustrator.  For a longer list and a discussion of the advantages of FOSS, see the post: All the software a geoscientist needs.  For free!

Showcase of FOSS in research presented at EGU2012

Have you used FOSS in research that you are presenting at EGU2012?  If so, add an advert for your work in the comments (even if it has already been presented).  The list will demonstrate the wide variety of applications for FOSS in the geosciences.  Abstracts for the presentations can be looked up on the conference planner website.

Topics discussed at the meeting

Much of the discussion was led by scientists who are also developers of the software that they used.  Some of the main themes were:

  • The need for reproducibility in science. If people cannot reproduce your results, how can they test if your hypothesis is correct?  This issue was highlighted in a recent editorial in Nature, and it is likely that it will be increasingly necessary to publish code alongside results.
  • Logistical issues with packaging code.  Many open source software projects are built different packages from many sources, each with their own schedule of updates.  Sometimes, using a different version of one of these can cause a model to give a different result.  The need was discussed to ensure that older versions of packages are always available so that results can be exactly reproduced.
  • Getting credit for your work.  If an open source model is used by the scientific community, it has, in effect, been peer reviewed.  Can a system be developed so that the software itself becomes a citable bit of science, e.g. with a Digital Object Identifier (DOI)? How would this system cope with different versions of the same program?
  • Ensuring good documentation.  Scientists often write code for their own use and give little thought to documenting it for others.  If an open-access journal could be created where documentation for a hydrological or climate model could be published, along with an example use case, this would make it easier for others to use the models as well as giving another way of citing the author(s).
Categories: Uncategorized

EGU2012 broken wifi workaround

There is a problem with the wifi in the conference centre at EGU2012.  Some people can log on, but others cannot.  They can connect to the wireless, but trying to browse the web results in ‘Page not found’ or DNS errors. DNS errors mean that the names of servers are not being correctly translated into the IP addresses they represent.

I was in the second group, until I just met some German dude who showed me a workaround:

  1. Connect to the EGU wifi as normal.
  2. Open a browser window.  It will try to connect to http://hotspot.egu2012.local/login, but it will fail.
  3. Change the server name to the IP address, 172.16.0.1, so that the address becomes:
    http://172.16.0.1/login?
  4. A webpage will open with a login button.  If you try the button, it will also fail.  Instead, save a local copy of the webpage.  (File, Save Page As…. in Firefox).
  5. Edit your local copy, changing all instances of hotspot.egu2012.local to the IP address.
  6. Save the changes to your local copy, then open it in your browser.
  7. Click the login button, then surf away…

This just worked for me, I can’t promise that it will work for you.  The German lad also said that you might need to redo it each time that you reconnect.  And of course these instructions are of no use to you if you can’t actually get online to read them.

Categories: Uncategorized