Why the VEI is Wonked

Eyjafjallajökull 2010-04-18.

The VEI scale might be the most ill-begotten piece of quasi-physics ever devised in the history of mankind. One thing becomes abundantly clear and that is that Chris Newhall and Stephen Self might be good volcanologists, but they are not in any way physicists.

Let us start with a basic problem. Eyjafjallajökull was a VEI-4 calculated on primarily the amount of tephra ejected, and secondarily on the height of the ash-plume. Grimsvötn ejected as much tephra, and had an even higher ash-plume. Both are VEI-4s according to the Volcanic Explosivity Index (VEI).

The basic requirements for a VEI-4 is that it ejects between 0.1 to 1.0 cubic kilometer of tephra, and has an ash-plume that is anywhere between 10 and 25 km high. Eyjafjallajökull ejected 0.25 cubic kilometers of tephra and had a peak ash-column of 9 kilometers. Grimsvötn is not fully tallied up, but it released the same amount of tephra in its first 24 hours, and had an ash-column that was 20 kilometers high. Eyjafjallajökull took 60 days to erupt the tephra, and only for a couple of days had a 9 km ash-column. But let us say that they both released the same amount of energy during the mentioned time spans, just for arguments sake (at least for now).

What is an explosion? It is the almost instant release of pent up energy. 1 quarter kilo stick of dynamite is the same amount of energy as 2 Mega-joules of energy, or the power equivalent of a 550 watt travelling hairdryer running for 1 hour. Guess which will blow up your car?

And here we hit the head of the VEI-nail with a stupendous physics hammer. If we go back to an explosion being your basic energy release over a specific time, then the time issue gets rather critical quickly. Why is this important? Well, the energy release over the specific time frame decides how destructive an explosion is. Dynamite is destructive, a hair dryer is not destructive (unless your stylist is a moron).

Photograph by Hrafn Óskarsson 2011. Grimsvötn seen in the evening from Reykjavik, height 20 kilometers.

Now some of you will have tallied up things and come up with a huge difference between the eruptions. If you are a normal sane person you have now calculated the difference in destructive force between Eyjafjallajökull and Grimsvötn being 60 times larger. With sane I mean that you did not study physics. To loft up the same amount of tephra in a sixtieth of the time poor Grimsvötn needed to use Eyjafjallajökulls total energy squared. This is actually simplified; Grimsvötn erupted through a 16 times wider muzzle and lofted the load to twice the height.  For those of you who own guns, you know what I am talking about. But in the end the number of 240 times more destructive will suffice. (Dear colleagues, I am simplifying things here.)

To go back to the analogue, Eyjafjallajökull was not a travelling hairdryer compared to Grimsvötn, it was more like a professional hairdryer used for half an hour. It will still though not blow up your car; it will just make your hair look un-natural quicker.

As you by now know, all VEIs are not equal, and sometimes physics is good for tearing down idiotic scales created by people who just want to have a scale named after them. When I have the time I will create a scale that actually measures how destructive an explosive eruption roughly is, but that would still not take into account all sorts of destructive forces involved in an eruption. It would just be a small component of the problem, because in the end the non-explosive Laki eruption killed more people than any other volcano in the history of mankind. VEI, yeah right! I think I will acronym my poor formulation into Destructive Index of Eruptions.



457 thoughts on “Why the VEI is Wonked

  1. News snipplet… one Páll Einarsson (geologist) of Eyjo/Katla “connection” fame is currently at Reunion in Indian Ocean. He is researching “highly active volcano on a hotspot,,, like Iceland has” but when he arrived all went quiet!!!! Doh, speaking of luck…
    (Source: RUV Rás2 telephone interview with him on today Sumatra Quakes.)

  2. Hi all, are there any Juan de Fuca / Cascadia geeks on here??
    I’ve been intrigued lately to find out what the future may hold for the Subduction beneath the west coast of North America.
    The Juan de Fuca / Gorda plates being the remnants of the Farallon plate now lying as a big mass beneath North America, is it to be assumed that the De Fuca spreading centre will be subducted under the west coast? and if so, will the subduction zone be continued with the Pacific plate taking over, or will the cascades region be dominated by a new transform fault system / rifting associated with the subducted spreading centre??

    Maybe I could be lucky enough for Erik K(?) to read this and provide info! 🙂
    Great work Carl + team.

  3. Probably one or both are false – old 350 kg WW2 German submarine mine was blown up around that time at Stapafell Quarries. It had been caught in trawlers nets off Reykjanes.
    It was slow-explotion (age?) and can be seen on RUV.is news at 19:00 UTC.

    11.04.2012 17:47:40 63,681 -22,803 1,1 km 2,2 80,24
    10,2 km SA af Eldey á Reykjaneshrygg
    11.04.2012 17:47:31 63,629 -23,550 1,5 km 2,6 90,01
    14,1 km VSV af Geirfugladrangi á Reykjaneshrygg

  4. Off topic abit, I have found the iceland review a good source of info in the last year and abit. The info from the link below is not alarmist by any fashion. My thinking is the team that went to Askja found out that its getting more active as is the rift zones and this is a little scoop or letting us adjust
    slowly to the info.


    Now i understand that many of the people that visit the site is aware of the news from this, forgive me if i have doubled posted. I did check.

    • “Rewamp of older news” – Real news of Askja situation are not out, so far as I read there – and links are to older articles.. My own personal opinion on Iceland Review news in general is, that they are aimed at “to be tourist friendly” but often are “old” news for us. (*talk that way to Icelanders and they think you are talking to children*)

      • I wish that one or two of our Icelandic friends could go and jank the tail of RÚV a little, I wanted to watch the 40 000 year old Mamoth clip, but they do not allow me to watch Icelandic News… 😦

        • Jank tail on RÚV is impossible – its “non”-political you know.
          Try that with Swed TV. No offense meant.

          • If enough people complain even the non-political listen after a while. After all, they do want to be watched really…

  5. Here is a link to yet another EQ mapping app. It is a little bit different and might be useful or at least interesting to some. There is always some other server you can get on. This one shows different ground sources that you can click on. Not all of them show something, but enough do to perhaps keep it handy.


  6. Don’t you just luuurve news agencies…

    There’s an article on Morgunbladid (mbl.is) titled “Icelandic Volcanoes Said to Be Growing Restless” quoting The Telegraph as its source. The Telegraph article in turn is none other than our beloved “Iceland volcano: and you thought the last eruption was bad…”

    Kin’L! 👿

      • It’s not you, it’s those fu…, erm…, bloody journalists so no need for you to apologise on their behalf. But I agree, the poor command of the language displayed in both cases have the Icelandic volcanoes as saying. Wonder how they managed to get them to talk…?

        • No worries. Irony on my part 😉 Yea, I do know, we are fed on crap (and we most often know better), You should really COMPLAIN to the editor. The more, the better.

          • Editors do not care about facts.

            They care about sales. In the news business this means eyeballs. The more eyballs you have, the more you can charge the advertisers.

            Facts and accuracy be damned.

            That’s why no retraction has as much space or a prime a location as the article in error. They care nothing for accuracy.

    • Whatever it was she posted (and said it wasn’t confirmed), it looks like USGS “unconfirmed” it 😉

      • Magnitude

        mb 5.5



        Date time

        2012-04-11 19:04:20.0 UTC


        1.22 N ; 92.07 E


        10 km


        779 km W Medan (pop 1,750,971 ; local time 02:04:20.0 2012-04-12)
        555 km SW Meulaboh (pop 35,062 ; local time 02:04:20.0 2012-04-12)
        602 km SW Banda aceh (pop 250,757 ; local time 02:04:20.0 2012-04-12)

        Source parameters not yet reviewed by a seismologist

        More information at:

        USGS/NEIC Denver, USA
        Badan Meteorologi & Geofisika Djakarta, Indonesia
        GeoForschungsZentrum (GEOFON) Potsdam, Germany

      • Hello Judith 🙂
        Do you think you could use the backspace and “edit” them a bit so that they are shorter?
        Now they are rather “tall”.
        The quakes are interesting, no problem, it is just a bit of esthetics 🙂

        • Morning Carl

          Ok will do the ones I posted this morning hopefully are ok they were shorter with the link showing.

    • There is no tornillo recorded. I notice the word tornillo here very often, but people should realise that tornillo’s are very rare and have only been recorded at several volcanic systems. A tornillo usually lasts for minutes; starts of at it’s highest amplitude after which the amplitude slowly decreases over time.

      • It fits the description and examples given by Erik Klemetti over at Eruptions last year – it lasted some 2 minutes and 15 seconds and it “corkscrews” in amplitude. If you know otherwise, please explain exactly what, in your opinion, it was and, after looking at the record again, why it displays two of the chief characteristics of a tornillo, yeet isn’t one.

        • The tremor you refer to has a clear peak amplitude somewhat halfway through. Tornillo’s start at their peak amplitude and slowly decrease, as I said.

          a) Tornillo
          b) ‘Regular’ tremor

          The second tremor here is like a tornillo (it is however an ice-quake in reality, which are very similar).

          • That is a de-gassing. It works like a chain reaction with a slow build up to peak, and after peak gas (when the gas suspended starts to drop compared to gas expelled into free form) it slowly drops away untill the gas is loose for the time being.
            Big wet Ruiz fart…

            But!!! Since this is Ruis, it could also have been the acceleration, peak, and run-off of a lahar. I am not saying it was though.

  7. I still find this graph suspicious. Do not know why. Hunch? Like runup to Eyjo was, I got it wrong by mere five days. But Hekla, Vatnajökull (Bárðarbunga/Grimsvötn) or Dead Zone are likely be next, I think. Katla is in limbo (except Páll Einarsson is abroad) and Askja is still unconfirmed. http://hraun.vedur.is/ja/oroi/dyn.gif

      • I do not know exact co-ordinates, only at north-edge of Bárðarbunga, Iceland, about mid-way between “skr” (Skrokkalda) and “ask” (Askja). Many of them do not show on other SILS, so I think very local (maybe) within Bárðarbunga / Kistufell region but main ones are from the weekends swarm, that appears ongoing of sorts. Its the step-up that bothers me. But I am not expert.

    • What is it specifically that makes you think something is about to happen?
      I see the quake swarms a couple of days ago, and I see the two Sumatran large quakes. But if I take away that I see nothing unusual.

    • Pity I can’t get the thermal image webcams. Seen a couple of smaller hot spots (presumably fumeroles?) come and go this evening.

    • USGS gives me a headache, the have the Magnitude at the wrong place. So, I just saw a 10.2 outside of Oregon 😳

  8. Semi OT… mainly answering a question from a page ago (or so)

    forestred’s question answered by Carl le Strange and henrilerevenant.

    Subject: Cascadia Subduction Zone, and the San Andreas Fault system.

    As noted, the Farallon plate went under. Estimated place this as about 20 to 25 mya. Current position is postulated at being somewhere under the Eastern Seaboard. In order to accomplish this, the Farallon would have had to become separated from the spreading center and may have undergond “slab detachment”.

    The location of the subducted spreading center… if it is still intact, would likely be have contributed to the start of extension in the Basin and Range province and the Rio Grande Rift.

    Taking the 30 million year contour of the Pacific Seafloor, and treking over to where the spreading center should be at if the whole structure were intact, yields this.

    Another notable item is that the Yellowstone hotspot started it’s trek at about 18 to 19 mya ago, and has (in some literature) been said to have sliced part of the Farallon in two as it went by.

    • Hope the news doesn’t see this…
      Hot News!
      Yellowstone upgraded to Welding torch status. Scientist says it i going to cleave the Cleaveland!

    • Great, thanks for the input. The whole western half of the USA is amazingly complex and active geologically. Rifts, volcanism, super earthquakes and volcanoes.
      I remember going through California, Arizona & New Mexico on the Greyhound bus, as part of a coast to coast trek and being blown away by the geology on display.

      I’d love to see some active volcanism in the basin and range province, was there not some talk of pending eruption(s) in east / southern california last year??

      BTW – Not sure why it brings my name up as forestred – This is James 🙂

      • Hello James!
        Well, do you have any acount with WordPress at another blog using the same email?
        I do not know if you are logged in when posting or not.
        Give a bit of detail and we might understand what is happening.

        • Hey, Yeah.. I’m sure its due to my new Gravatar / WordPress account, which I set up to replace the glum smiley that I’ve been allotted on here and also previously on Jon’s blog.
          I’ll get around to changing it when I get the chance 😉

  9. I find if you open another browser window, then half both you can have a look at things and use the other for posting, a bit old fashioned but works a treat.

  10. Just a tought regarding the scales (from around the first page of comments), but I got reminded of the Absolute and Relative Magnitudes (don’t remember exactly what it was… luminosity (?) of ‘stars’, and at 1 pc or something for absolute) when you were talking about the dangerousness of an eruption…, maybe if you put it hypothetically in a ‘isolated’ place, but in the equator, to measure a possible effect?, or something in the middle…, Nabro and Merapi are along the extremes when it comes to isolatedness, and that gives a way too wide margin.
    Maybe a ‘unified’ scale for volcanoes is something that can’t be achieved as of now, but you might fit them more nicely if put in 2 or 3 lists (and Hekla), with their own specifications?…, I don’t know if something already exists on that line…

    Oh, and regarding the ‘volcanoes at ~100 kms from the subduction line’, someone posted this here (I think) some days ago: http://www.tectonics.caltech.edu/outreach/highlights/mase/ , just in case someone didn’t saw it.

    • According to the definition supplied by Pieter, no, and at the moment I accept those. I am however skeptical because of the rareness of the observed (true) phenomena and its confinement to just a few volcanoes. Why? Let me illustrate with an example from gemmology:

      In 1889, a new variety of garnet from Mason’s Branch, North Carolina, was described in a paper. It was described as “pink and purplish”, the colour of the rose bush flower hence “Rhodolite” and was not as saturated meaning larger gems could be cut without appearing too dark. Scientific investigation proved it to be a pyrope-almandine intermediate and set apparent limits to the range of R.I. possible for this variety. Naturally, with finds limited to a single locality and it being desirable, price was high.

      Then deposits of garnets that shared the colour, optical and chemical properties were found in Macon and Jackson Counties, NC, and the dispute about what was a Rhodolite began. It was not until gems that were indistinguishable from the original were found in large quantities in the gem gravels of Ceylon (Sri Lanka today), Madagascar, Rhodesia (Zimbabwe today) and Tanzania that, finally, the unscientific and commercial definition based on locality was abandoned and a scientific one of physical; chemical and optical, properties accepted.

      Now, what has this to do with “tornillos”? Tornillos like Rhodolites were first described at one locality, in this case Galeras. Grudging acceptance has since been given for their occurence in a few, select volcanic systems other than Galeras. Their definition is based on optical appearance, how they appear to the eye on a webicorder, same as once Rhodolites unscientifically were on colour and saturation thereof.

  11. Well, I went to town and filed my income taxes. Then, when I came home I checked out the amazing two new EQs in my relative neck of the woods, then I secured my two baby goats, who never stop eating, then checked out the TWO NEW LARGE QUAKES…I guess the experts are correct, no need to worry, but I am sleeping downstairs tonight, with a flashlight, just in case…it has been raining on and off all day, the cloud ceiling is very, very low, and so it goes. Tough enough…checked out Rescue Remedy, it seems to be 27% alcohol, no wonder it works, but I think I’ll drink a glass of wine instead. Bottoms up!

    • Your neck of the woods?
      I think that if you live in the neck of the woods the Tsunamis has charged by a long time ago (and they where not big at all), or have died out before reaching you. I would not be afraid of those quakes now really.
      Hope you got a nice sleep.

      • No, Carl, I live on the other side of the ring, where the EQs are closing in. I am not afraid of tsunamis at all. I see today that Mexico is rocking and rolling. I have EQ nerves, I guess. Not to worry, Lucy said so!

  12. Good morning/night everyone. I collected a whole lot of links for the treasury from last night activity here. But i dont have time to work them in till the weekend. So please be patient with me.

  13. I know I mention the modification of the historical temperature data as evidenced in this link


    and how it seems that certain organizations appear to be pushing their agenda through data manipulation… evidently to support their preconceived notion. You know, adjusting the data to fit the model, rather than adjusting the model to fit the data.

    Well, it isn’t just that.

    Sea Level Data Corruption – Worse Than It Seems
    Posted on April 11, 2012 by Steven Goddard

    The graph below shows changes in Envisat Northern Hemisphere sea level made this week. Previously, sea level was decreasing -0.241 mm/year, and now it is increasing by 2.37 mm/year. The most recent data magically went from lowest on record – to highest on record.


    • A little known fact is that the worlds longest running and well researched measuring spot is in my neck of the woods. It measures the record Isostatic rebound at the Swedish High Coast. They have been at it since 1750.
      That station (upgraded many times) still has old gismos to compare that the new equipment is also on the up and up.
      For various reasons it has the most stable readings on the planet due to hydrogeological setting of the “Östersjön” a northern part of the Baltic Sea.

      It works as a naturally filtered oceanic gauge.
      From 1750 to 1997 it showed the same data, uplift of 10.2mm annually. Watching that one bored the living daylights out of the scientists at SMHI (Swedish IMO). Then something happened and it started to show erratic values below 10.2, with a high-reading as the calving in the antarctic peaked around 2006 of 6.1mm in isostatic rebound. After that it has recouperated, probably due to various solar cycles. 2011 value is at 8.4 mm IR.

      So to see what the hell was happening they checked the GPS-network to see if the IR flex-curve had changed (Ie, if the IR had started to drop at the High Coast). It had not.

      I trust that value, it might not be exact for every spot on the planet, but since the oceans are interconnected fluid dynamics give that you over time can do measurments with very few gauges. And use one as a control, after a while the level will have evened out enough to influence The One.
      To put it bluntly, when data is reported to be whonked at places, I go to those I trust, and SMHI would never fub data. It is one of those boring organisations that I trust with my life on an almost daily basis, and yes, they might get a forecast wrong, but they are the types that would do anything to raw data, exactly the same as IMO.

      If you want data that is even less likely to be fubbed with, call and ask the Fins. Fins are impossible to influence or warp, and they are genetically programed to not be corruptible. Seriously, do not try to bribe or coerce a Fin…

  14. Time to take a deep breath and read this article posted by Sherine over EB.
    It explains a bit about the weirdness of the Sumatran quakes:
    “This happened in the middle of the boundary between the Australian and Capricorn component plates of the Indo-Australian plate. The Indian-Australian plate is twisting apart into three pieces about rotation poles contained within very broad boundary zones.”
    Food for thought, indeed…

    • I think that this will be the first of many articles about this weird EQ.
      “That is little comfort to many geologists, however, who I suspect are going to be scratching their heads over the precise geometry of this one for some time.” Totally agree!

  15. And another stronger 6.3 mg

    Magnitude Mw 6.3 Region BAJA CALIFORNIA, MEXICO Date time 2012-04-12 07:15:55.7 UTC

    Location 28.78 N ; 113.18 W Depth 60 km

  16. USGS reports 2 new earthquakes,

    M7.1 – Santa Isabel, Mexico 2012-04-12 07:15:52 UTC, 10km
    M6.9 – Santa Isabel, Mexico 2012-04-12 07:15:48 UTC, 10,3km

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