The VSI scale

Guest post by Tallis

Humans have always had some fascination with rankings, some of the most popular videos and articles on the internet have dealt with comparisons and rankings. However, this doesn’t mean that it is just another useless fad, on the contrary, a well thought-out “Top 10 list”  can be very informative. For disasters, we have created scales, and we are all very familiar with these scales, the Fujita scale, Safir-Simpson scale, Moment magnitude, and the VEI scale. Just like us, these scales are imperfect, they don’t factor in all of the variables, most of which you would only know right when the disaster is taking place or afterwards but they get the job done. We don’t need to understand all of the variables to understand that when an EF5 is coming, that means get into a basement. However, volcanoes aren’t like most disasters, we don’t really see disasters that produce such varied and extreme consequences on so many levels. For example the Laki eruption, a VEI 5, killed more than 30,000 people directly, and the explosivity of that eruption had negligible effect on the actual population. The VEI scale is a great scale for scientific purposes, easy to understand and easy to apply but when it comes to the effects that is where it’s reliability breaks down somewhat. For instance a VEI 7 can cause less direct death and damage than a VEI 3.

My VSI scale will have it’s focus completely dedicated to the consequences of eruptions, and will serve as an excellent way of estimating the scenarios born from volcanoes. What does it mean? VSI stands for Volcanic Societal Impact, and it’s focus is dedicated solely to direct volcanic impacts, so climate consequences are not a factor. Climate effects of larger eruptions are chaotic and unpredictable. When a large eruption takes place, by the time it takes to get a general idea of the volcanic winter, the eruption could have already ended. The damage done by a on-going eruption does not include subsequent climate effects (although it could be factored in for historic eruptions).

For the VSI scale, lahars, ashfall, tsunamis, landslides, shockwaves, gas emissions, glacial flood outbursts, and pyroclastic flows can all be factored in with relative ease. The two primary factors are range and impact. Both are split into 4 categories, Short range: 0-30 km away from the volcano, Medium range: 30-70 km, Long range: 70-100 km, and Distal: 100+ km. The impact categories are, None or negligible, Minor, Moderate, Severe, and Catastrophic. If climate consequences were to be factored in, they would go under the Distal range.

The scale goes from 0-12, but how would we discern whether an eruption is a VSI 1 or 12? We think about what impacts the eruption would cause over any of the ranges listed above. We convert the impact categories to the numbers 0, 0.5, 1, 2, or 3; we then add all the numbers to get where the eruption lies on the scale. For instance, the recent eruption of Fagradalsfjall would be VSI 0 as it has negligible consequences on all ranges, so 0+0+0+0=0 and a truly Catastrophic eruption be 3+3+3+3=12.

Now this is where the problem shows, the definition of a moderate, severe or catastrophic impact would vary depending on who is using the scale, which would lead to some conflict on where to place certain eruptions, the Enhanced Fujita scale has similar issues. Another issue is that the scale doesn’t tell you what the primary hazards are, a VSI 8 over land and VSI 8 over water will have different hazards. Another issue is that this scale focuses on impacts and with some good preparation, the impacts of a massive eruption can be reduced substantially and as such the eruption would rank lower on the scale then a smaller eruption that took place without good prep. The largest eruption of the 20th century, the eruption of Novarupta ranks at 1.5! Needless to say, the population and infrastructure surrounding the volcano plays a crucial role in finding out what it’s potential ranking is.

Now that I’ve explained the scale, I will rank some past eruptions and I know the perfect place to start!

The 1883 eruption of Krakatoa

The town of Anjer, after the eruption

This eruption is one of the most infamous in all of history, and it was the first disaster to grab global attention, so naturally it’s the perfect place to begin. The eruption produced several explosions that were more energetic than most nuclear weapons and while the cause of the explosions are fascinating, it doesn’t matter for the ranking. Most of the deaths were caused by the four massive tsunamis produced by the eruption. Each explosion also caused massive pyroclastic flows that reached distances of up to 40 km in some areas. This eruption is one of the deadliest in Human history killing more than 36,000 people. In Anjer alone, 7600 local inhabitants and 14 Europeans died.

This volcano ranks pretty high for a low end VEI 6. The Short and Medium range impacts were all Catastrophic due to the tsunamis and pyroclastic flows, Due to the tsunamis, the volcano produced severe Long range impacts, and the ash fall and the tsunami would’ve produced moderate distal impacts. So this eruption would a VSI 9 (3+3+2+1=9)

The June 1991 eruption of Pinatubo

The most recent VEI 6 eruption, this eruption was one of the most important in the history of volcanology. It was the first VEI 6 and volcanic winter to be analyzed with modern technology, and this event greatly broadened our understanding of large volcanic eruptions. The response to this eruption was a triumph, as the preparations prevented 1000s of deaths. Still, this volcano killed more than 800 people due to falling ash. This eruption did substantial damage to the Philippine economy and it produced lahars for years but consequences for the country were nowhere near as bad as it could have been. As such his volcano ranks a bit lower on the scale. Short and Medium range impacts were severe, long range and impacts were moderate, distal impacts were minor. So Pinatubo would be a VSI 5.5

The April 1815 eruption of Tambora

This eruption was one of the largest and deadliest of the past 4.000 years, killing more than 75,000 people directly and causing global famine. All life surrounding the volcano was destroyed by the massive pyroclastic flows. Despite being 10s of km away from the coast, the pyroclastic flows still displaced enough water to cause a moderate sized tsunami that would kill over 7,000 people, the ashfall was so severe that it plunged several major islands into famine and the extensive rafts of pumice would hinder sea travel for years.

The short and medium range impacts were catastrophic, with severe consequences for Long and Distal ranges so this eruption would be a VSI 10

There are several big candidates for VSI 12 eruption, some you already know about but there are some that don’t get talked about but that’s an article for another day and in fact I would like that series to be a joint venture.

With this scale we can have a better gauge of the societal effects of major eruptions but it’s not perfect. If you have any suggestions on how to make the scale better, I would like to hear them in the comment section. No scale can be perfect, since the scale makers aren’t perfect. Perfection should be sought after but never expected.


380 thoughts on “The VSI scale

  1. Charts :



    • those links didn’t show up, try again …


  2. Found a working link 🙂

    It does look to be more promising now, unlike any of the other times the blue has gone up sharply and the green is actually doing the same, just like when it was erupting or leading up before. It is probably a good few hours until anything happens but this looks promising.

    Question is if it will erupt in the crater, or if we are in for something a bit bigger 🙂

  3. Might be worth keeping an eye on the Mila Keilir thermal cam too (just for a bit of variety) – if this shows up, just copy into the URL field in a new tab.

  4. The highpass drumplot is looking intriguing.

    The Keilar thermal cam is sure as heck showing more than it has in days, so this can’t be just a seimo artifact. That volcano is doing something. The only question is, what? Is it just teasing us again, or might we see actual lava soon?

    • I think something happened in the conduit after 9:15 this morning. The blockage I have banged on about may have been cleared?

  5. Would guess there is probably some lava in the crater, there is a helicopter circling and a lot of heat. I must say if this is true I am a bit disappointed we didnt see the whole cone rift open with a curtain of fire but if the supply hasnt changed we might see this next episode evolve into something quite spectacular. Even if everything is normal having flows liek we saw before lasting multiple days will be significant, that is the sort of thing that can plausibly fill both valleys to overflowing.

    I expect this is also a new cycle, long pauses and larger paroxysms perhaps. It is evolving, getting more powerful 🙂


    This is not new, from September 2, the last time lava erupted. Shows the north flank breakout very well and in clear detail though by this point it was much subdued from the peak. I wonder if this weak spot will still exist for the next flow.

    • Its sooo fluid too! Looks like the very most fluid of Kilaūea Ikis lavas .. this stuff is so runny .. even more runny than Holuhraun

    • And it is interesting to see in their video that lava is also pouring out from about half way up the inside of the vent.
      We saw the earlier video of the dry vent and the “door to hell”. This shows there may be a number of lava pathways through the edifice.

      • And, in fact, already leaking out of the structure west into Geldingadalir.

  7. There seems to be yet another expression Giggle translate is not tackling well: “goslok”. It means “end of an eruption”.

    We have a term for that.

  8. I put the article through Yandex, and the person making the statement is translated as “Egil Squarepants”. There wasn’t a photo of him unfortunately.

      • The text google translates a little differently as:

        “Until this morning, Böðvar says that experts have not begun to consider declaring eruption”

        It also says that activity started at 5am today. The video looks to be to illustrate the volcano, not the event.

        • Also that at around 12.37 on the RUV close-up cam, steam/smoke started up from just to the left of the cone and which now extends quite a bit further away from it.

  9. So far I have only been a silent reader.
    But what is going on behind the theater hill?
    Lots of smoke to see on RUV cam

    You are very welcome. First-time comments are held back by the deamon for approval by a dragon. Sadly this is necessary – blogs attract spam. Hereby released from the dungeon – admin

  10. I’m not seeing anything but vog emissions from the cone. Are you using a different camera than the Langihryggur one? If so, what is the Youtube URL for it?

    • No there is no live cams showing the lava, it is from an overflight. I dont think we will see very much of anything on any of the existing cams either until the episode peaks, because the lava is flowing out of a vent on the far side of the cone completely out of view. It will have to flow all the way to Natthagi to get within view of a webcam now, that will probably happen but maybe not for a few hours or days yet.

      • On the Reykjanes cam (Mila) there is indeed smoke to be seen in Geldingadalir.

  11. This lava is even more runny than Holuhraun
    Fagradalshraun is so very fluid near the vent perhaps as fluid as Halema’uma’u

    Have fagradalshraun produced any peles hairs yet?

      • Yeah, it’s flowing from a hole at the bottom of the crater

        • In which direction? Or inside the crater?
          The main thing, is that he woke up

      • There is lava fed from possibly a hole in the crater into Geldingadalir and spattering out of some holes in the lave field:

        • Here’s the lower part of the crater with the outbursting lava:

          So the helicopter video was indeed from today.

        • Thanks. That explains the smoke behind the theater hill that I saw.
          Hope for exciting days and weeks.

      • You don’t need a facebook account. If you are on a desktop click “Not Now” when it asks you to login or create an account. If you are on a phone or tablet you may have to click “Desktop mode” in browser first.

        • Unfortunately, no. In the past you could watch without accont. They changed the conditions.

          • Trust me – I am watching it not logged in. 🙂

            If it thinks you are on a mobile device it doesn’t let you though and wants you to use the app which is why you need desktop mode first. If it says content is no longer available – click play button again.

            I’ve tested in both Firefox and Chrome and I can play video full screen with no account.

          • I’ve just retested on an Android and it seems the Chrome browser no longer works in desktop mode to bypass the app. However Firefox still works fine on the same phone in desktop mode and I can watch the video with no account.

          • Hmm Firefox keeps cutting out on Phone. Stick to a desktop seems to be best if you can.

          • Ah the video is no longer live which is why phone cut out 🙂 Maybe a new stream back soon.

    • Was working, but now it’s frozen buffering with a message that says it “should resume shortly”. It didn’t resume “shortly” though. It’s been several full minutes without resuming.

      Didn’t change anything at my end. Resource monitor doesn’t show any sudden bandwidth hogging from background processes (Windoze Update, e.g.). Any ideas what might be causing this?

        • If it ended, it would obviously not say it “should resume shortly”. OTOH it’s clearly not recovering on its own. What do I need to do to fix it? Reload the page?

          • The stream ended, the guy who was streaming’s phone battery died. It will not resume.

          • If that’s true, why does it explicitly say that it will resume?

          • The facebook algorithm took a guess that it was a temporary pause and didn’t bother to tell you that option had now timed out.

        • It does seem you need a facebook account to watch the replay though. Not sure if that’s a settting they cay change on video visibility setting as I can play other videos on the same page. Hang on if I don’t switch to full screen mode and instead pop out a picture in picture window and then enlarge to full screen it works but if I click the full screen icon facebook asks me to login which it doesn’t for other videos on the page.

          It is all a bit hit and miss. Stupid facebook.

          • not stupid, it is facebook trying to force you to create an account. sell your soul, or something similar

          • Yes I know what they want me to do and I do have a rarely used account I can login a private browser window (never on the phone app) if absolutely no other option. If I go to (desktop not logged in) then everything seems to work and I can browse and play live video set to public just fine. I suppose it is possible they might throw random failures every so often which explains why something works one minute but not the next and then works again later.

            Whether a feature or a bug I still consider it stupid 🙂

    • That shows it is erupting from a vent in the crater wall, so the lava is flowing half into the crater and half outside of the crater

      • Possibly the main conduit is now blocked and it forced a new one through a pipe that was subsidiary. Would explain the lengthy delay. It might almost be like ‘starting from scratch’.

  12. This looks substantially weaker with less volume than formerly. Carl has suggested elsewhere that the fissure/dyke has partially closed up.
    The lava looks to be flowing on top of and into the previous lava lake, producing some fountaining as the new stuff degasses.

    • I totally agree.
      My much vaunted (and much derided?!) theory has been that the conduit collapsed on 3 September at 5km down after some kind of disturbance, and this caused the failure of the eruption cycle.
      There was another disturbance this morning (Island time) that may have opened some of it up. But only partially. The tremor graphs are weak and the inflow of lava looks rather sad.
      Alternatively, it could be lava is burrowing a new path up from the blockage and it is still being established as a route.

  13. Yes, on the still photos you can see that the lava that leaves the crater is collecting in the lake from the last eruption.
    The vent FLO can be clearly seen. A bit in the direction of NAR you can still see the tip of HEL? I think SIF is covered.

  14. We can see the huge crack on the crater’s mantle very well in GutnTog’s video from 7th September:

  15. I find this tremor graph quite interesting in light of today’s developments –
    See the sgi chart:

    • Can we safely assume at least 3 new fissure vents have opened up in the lava field?n Lots of helicopters flying overhead today.

      • Nono, just lava fed by the fissure at the crater, popping up from under the crust.

        • People are noticing that the 4 vents seem to be in a line (almost)

          • My guess is that the lava is flowing mainly below the surface. The lava lake that had formed now has a solid crust (do not walk on it though..). Lava is pushing in below where it is still liquid. It can’t get out well and so it is pushing up a bulge. The venting happens where the solid surface has cracked. Note that the vents fountain but do not (yet) form surface flows.

    • There are many questions now:
      1. Does the volcano further ramp up or will it go on like this?
      2. Will it be periodically (which seems reasonable)?
      3. Will the crater rim collapse, if the lava keeps pushing from below?
      4. Is the motoway now in danger again, if the lava continuous to run into Geldingadalir.
      5. What is the meaning of life/universe/everything?

  16. In one of the videos one sees a ring of observers at the toe of the lava and that lake further back sloshing as the lava spurts upward. If what ever is retaining that mass decides to let go, there’s going to be one helluva BBQ and perhaps this event won’t be considered such a ‘Sunday in the park with George’ any longer. Volcanoes earn respect the hard way. By killing people.

    • Just FYI for anyone trying to play this; for me, I was able to get this working only by using an older, unsupported browser (old versions of Firefox and Opera). On newer stuff, it would not play without a login (which I do not have).

      • I can play it on the most recent version of opera. However, facebook has blocked the add-blocking build into opera and this can stop opera from working. Installing a separate addblocker gets it going again.

  17. So, why do we have fountaining lava out in the ‘old’ lava fields? Is this degassing from new lava pouring in from the vent, or have we some new rift opened up below the lava field?

    • Sorry, see this has been asked before. Captain Hindsight is my middle name.

        • 🙂

          Not to mention another track…

          Through a crack in Mother Earth,
          Blazing hot, the molten rock
          Spills out over the land.
          And the lava’s the lover who licks your boots away. Hey! Hey! Hey!

  18. With the new vent located directly below the crater wall, we might see an impressive flank collapse of the northern wall.

    • Even more so since there is this huge crack just above it.

      From one of GutnTog’s videos.

  19. The first small fumarole is now showing on the still cam from the Storholl (18:44). It moves towards the slope to Natthagi.

    • Well spotted! Perhaps just fume pushed trough empty channels? But then maybe lava will follow …

      Listen to the ground
      There is movement all around
      There is something goin’ down
      And I can feel it

      • Yes. It’s just smoke at first. The advancing lava displaces the gas from the run out tubes.
        But then when the eruption is long enough, LAVA.

    • Judging from the light it seems it was posted almost immediately after filming.

  20. Oh wow… just when I thought it had gone to sleep, and had been looking up Askja and Kilauea etc…

    Is there a possibility that one or more of the fountains in the new valley floor could actually be new vents? The furthest south would seem to be on the same line as the previous vents, heading straight for the south coast, but the others seem to be on a line of their own. But that line would look very much like where we saw the possible failed intrusion many months ago, towards the dent in the hillside where all the grass fires were?

      • There have been some rumbles on the drumplots. But it is extremely hard to suggest this is evidence for a new fissure. That said, there have been jolts over time during the main eruption, and signals of a new conduit or crack opening may have been lost in it.
        Hard to say.

        I’m guessing the main structure of the vent has become cracked and leaky, has offshoots through its structure, and torrents of lava are entering the lava pools under the hardened crust and kicking up the fountains.

        These are the crusts that people like to walk on with their fancy ski poles and light trainers….

  21. Whether those new “vents” are real new fissuring, or old lava tubes, it looks to me like almost all the new flow is going into Geldingadalir, and it looks substantial.

    If this keeps up, any idea how long until we see flow into Nathagi again? (via the western route, would be my guess – so those berms might get tested.).

    I also don’t recall ever seeing the eruption so clearly from the Nathagi (MBL) camera as I am right now.

    • Probably in the next day and if it lasts a few days that is what will get the filling done.

      Going back to last article I wonder if this is the beginning of stage 3, where we get radial venta and slower more sustained effusion to create tube fed flows? If that is the case then that wall is as good as gone, stands no chance. And if it breaches the other wall at the top of the hill it actually could put Grindavik at risk, really for tube fed flows anywhere downhill within 50 km is fair game…


    Maybe already posted but here is a good overview of the area. To me it looks that these are new vents, they are not incredibly productive but the lava is definitely being erupted here not just flowing over an empty cave. Back at the start of the month there were fountains here too, I think it is possible that when the flank breakout happened it was an actual deeper diversion just like Narlet, and when it went through the stack of new material it intruded north as a sill, there is no rockbreaking because it was within shallow levels either recent lava post-March or it was through hyaloclastite which is basically gravel. The fountains in this case are actual real vents. There was never any tube this direction.

    • The “new vents” theory is IMHO strengthened by what’s seen on the Nathagi camera; two distinct gas columns. One is over the crater (Nar), the other is to the left, which is a fit for the largest of the “new vents” seen on the RUV cam.

      My guess is that for it to be emitting that much gas, it cannot be previously erupted lave from the main cone via lava tube. IMHO, it’s got to be a deeper source. I know lave tubes outgas, but this is a LOT of outgassing.

      So…. is NAR doomed after all? It might be… new vents forming was how it formed, and then made “Bob” extinct. If the new vent takes over, Nar could end up like Bob (the original vent).

      • I guess it depends on where you draw the line, this is only a slight diversion with added flank vents. But the cent in the crater seems dead, if that is what is defined to be Nar then it is dead. But if it is the cone as a whole it is still alive.

        It looks like a plug formed and lava diverted around it, at the same time there was another diversion further north, how deep I dont know but probably under the new lava I would guess.
        The north wall is doomed, it is getting eroded from below by what could actually be a powerful fountain, a new vent will be narrow with the same flow rate, and lava was being ejected into the crater early on at high velocity sideways, and the vent at the base of the cone also has a sideways component too.
        I think soon it will open up and release the lava in the crater, then as it is now unobstructed it will turn into a proper high fountain until the episode ends. Intervals are probably going to be long now, more weeks without lava, but spectacular eruptions.

    Hopefully this will post a great fb livestream, showing how the lava is forcing a way through the vertical cracks behind the gusher in the wall. I’ve watched it get higher, and a second intermittent splashing becoming stronger, as the height of the lava within the main crater has risen.
    I wonder if some of the wall will give way with this undermining?
    We’ll see what happens…

  24. The recent drone videos show the ‘Door to Hell’ vent visible in the empty cauldron is no longer issuing lava.
    The current cent is on the other side of the volcano edifice. (See picture). So I guess something did block the original conduit, hence the delay, and now lava has forced its way into a new outlet. How far below the edifice, who knows.

    • Argh face-palm. ‘Cent’ should be Vent.
      It’s difficult to head-butt any one key at any one time on the keyboard.
      (Source: an ancient Guardian Steve Bell cartoon from his Normal Tebbit Diaries in the 1980s).

  25. My Sister is not to far from the RUV Geldingadalir cam right now. She said it is like being at the beach with massive waves during a thunderstorm and you can feel all of the pulses going though you and pushing you back. Bucket list thing.

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