Soufriere a VEI 4

La Soufriere in ashes

Howdy all. Long Time no Sea… 😀

I am one of your dragons. I lurk around in the back channel conversing with the other Moderators. My claim to fame here on VolcanoCafe is that “I plot stuff.” One topic that we have been kicking around, is just how large is the La Soufriere eruption. Albert threw out VEI 4 range as an estimate, I had no idea since I hadn’t been watching. I felt remiss in that, so I spent the evening rummaging around the VAAC reports. Now, first a note. VAAC Reports are SPECIFICALLY for the purpose of providing warnings and alerts for the aviation industry. They are not intended for any other purpose. What I do from time to time, is to use them for an unauthorized or sanctioned purpose. To estimate the eruptive rate of a volcano. Since my estimates serve no purpose other than for us to get a handle on what size an eruption is, and that I make NO CLAIMS as to their usefulness in a scientific or official realm, I think I may be able to slip under the radar and get away with it. The first thing you need to do is to weed out some of the errors.

First of all, VAAC reports are for giving appropriate aviation warnings. These guys are going to error on the side of caution. Warning boxes are of no use for what we are doing. The only data you want are actual reported plume heights. Note the yellow areas in this sample.

Sample VAAC report

This is the only data that is of real use to us. FL100 means “Flight Level 100” Essentially, hundreds of feet. TGMCoy may be able to elaborate on this since aviation is his field. (If he is still using that moniker). In order to convert that plume height to cubic meters of dense rock equivalent, refer to Mastin et al appearing in Journal of Volcanology and Geothermal Research. doi: 10.1016/j.jvolgeores.2009.01.008. The long title of the paper is “A multidisciplinary effort to assign realistic source parameters to models of volcanic ash-cloud transport and dispersion during eruptions”

Essentially, it is a method of getting usable data from what you can find. Their method is derived from work done by Sparks and is generally in close agreement with it.

What I do, is gather all the VAAC reports I can find for a particular eruptive sequence and convert all of the time stamps and data points to the number of seconds from a reference point. To fill in the gaps, I run a linear interpolation from point to point on a per second basis. This is a potential source for error, so keep that in mind. {note, I am not a glutton for punishment, so I used a software tool to do this… specifically DPlot by Hydesoft Computing.} → (Full Disclosure; this is an unpaid endorsement. He is based out of my home state and I’ve had great customer support from him.) Upon completing this step, I now have an eruptive rate estimate for each second of the eruption. I then run an integration step (same software) to obtain the cumulative DRE of the eruption on a second by second basis. This is what it looks like.

See that 4/10/2021 15:55 time stamp? (midway along the curve) that is where the column was reported above FL350, an eruptive rate of 639.68 m³/s.

At over 1.2 x 108 m³… I think it’s safe to say we are in VEI 4 territory now.

A VEI 4 is defined as between 108 and 109 m3 of ash and tephra. Tephra is a lot less dense than dense rock: you get a larger volume out than fits in the hole. To convert, we can use a factor of 2. That makes the current eruption 2.4 x 108 m³. We are in the lower half of that range. A VEI 5 may in the end be possible, if this continues long enough and especially if there is a bigger bang still to come.

Enjoy. Feel free to discuss.

Carl added some notes on misleading information doing the rounds on the wwww, in his inimitable style

I have to write about the eruption at Soufriere Volcano after all of the click-bait that has been written in the last couple of days, and to inject a piece of science into the debate.

But, first I wish to recognise that it is a disaster for the residents on the island. Especially the risk of there not being enough water is scary indeed.

There are 3 things that need to be addressed that is circulating around on the internet and that is amply wrong.

“VEI-5 oh my god we are gonna die!”

No, this is not even close to being a VEI-5 eruption. It is currently slowly moving towards a small VEI-4. There are not many videos of large eruptions, the closest that we have to a VEI-5 eruption is the 2011 Grimsvötn eruption that was borderline, but still not big enough. Please compare that video to what you are seeing Soufriere. The column is taller, and it goes into the stratosphere, it is continuous at this size for 24 hours before it slowly dwindles, total ejecta from the eruption was 0.9km3 of tephra. If you watch the video you will notice that Soufriere is not even scratching on being close size wise.”

“SO2 will cause a volcanic winter/global heating/my grandmothers cat to die.”

No, the eruption is too small for that. In the real world the current eruption in Iceland is about as gassy as Soufriere, and that is a small eruption. None of them will have any effect, you need almost 40 times more, and it must be injected straight into the stratosphere, and be converted into sulphates to have a cooling effect. We know this since Pinatubo injected 19MT+/-4MT into the stratosphere, and that caused cooling. So, way to little, and way in the wrong height…

Ash column is 60km high!!!!!!

Sigh, no… The tallest column registered was 17km, and it was short lived.

Now over to the video of Grimsvötn 2011, it is from the opening stage. It is taken from the edge of Vatnajökull 20km away from the eruption for scale.


VC is always happy to provide the facts and the fact checks. We do like to have our heads in the volcanic clouds, but with our feet on scientific ground!

490 thoughts on “Soufriere a VEI 4

  1. There is a lack of mainstream coverage of this eruption – I’m seeing Twitter reports and satellite animations that show some extreme action going on, but very little as to how the people there are faring. Hopefully VC can help by gathering info

    • A lot of ash and loss of power for most, with a directive to stay indoors.

      NEMO had reported a few days ago more than 3,000 in evacuation centres; the rest of the evacuees with friends or relatives. OTH some may still be in the red zone – hopefully not where the pyroclastic flows went.

      Try It’s a local St Vincent news site. is a site for Barbados.

    • I think it has a lot to with agendas sadly, I am being deeply cynical here. They keep trying to push the climate change agenda about greenhouse gasses and humans are responsible for greenhouse gas emissions… La Soufriere kind of destroys that notion… Look at the Sulphur Dioxide output from La Soufriere and compare that with China…

      Big volcanoes can cause volcanic winters. The laki fires were a contributing factor in the French Revolution.—add-more-layers/overlays?tcso2,25.642,52.910,3

      Not to mention that only vaccinated people are being evacuated.

      • Volcanoes are major but intermittent sulphur emitters. They cool the climate for a few years after a major eruption, about twice per century but individual volcanoes have no long-term effect. The effect of Laki is clear around the Atlantic but not elsewhere in the world. It remained a local polluter. To get worldwide effects you need a tropical eruption. Volcanoes are not important greenhouse emitters, though. Humanity emits very much more.

          • It is very hard to be certain that Laki caused effects elsewhere. The paper proposes a combined strong el nino with the laki eruption to partly negate each other. That does not make a particularly strong argument, and more data will certainly be needed. Even in Europe there is disagreement whether the hot summer was related to the Laki sulphate or not. Laki emitted its sulphate at low altitude: absorption of sunlight by the sulfate would explain the warm weather, but a persistent high pressure block would do the same. Overall, that the weather of 1783/84 in Europe and New England was related to Laki is generally accepted (but not by all). Effects elsewhere in the world are far less certain.

          • It is because of that uncertainty, we concretely can’t say that Laki was climate dud or climate catastrophe. This makes estimating the death toll of the eruption incredibly frustrating. Recent studies have agreed that the hot summer during the eruption wasn’t actually caused by the eruption, in fact Laki probably lessened the heatwave which makes you wonder how bad it could’ve been in the absence of the sulfuric aerosols.

      • Let’s not peddle weird conspiracy theories please.
        This is a place to admire science and nature. Not destroy it.

        Volcanoes do emit a lot of greenhouse gasses. But by doing so they keep the levels at normal levels. Which in turn prevents the climate from cooling as greenhouse gasses slowly leave the atmosphere. Humanity however greatly adds to this number so the amount of greenhouse gasses grows to high with negative effects.

        Its like arguing that we don’t need to learn to swim because we need water to survive.

      • This volcano is no where near large enough produce a large or even mid scale volcanic winter. At the best you could hope for a small scale volcanic winter. There could be plenty of other reasons why this eruption is not getting mainstream attention like it should.
        Only vaccinated people being evacuated by cruise ships as far as I know, is simply repulsive. This volcano could kill more people on this island then Covid ever could. It makes no sense and shows that people have there priorities wrong.
        Conspiracy shouldn’t be a dirty word, governments, corporations, and people can’t be trusted and I could list 10 events to back my words up off of the top of my head.

      • This volcano is irrelevant on climate timescales. Even a hypothetical much larger volcano that could cause a volcanic winter is mostly irrelevant on climate timescales. The cooling effects of all but the most powerful eruptions don’t last more than a few years to perhaps a decade, and many effects are localized. When discussing anthropogenic climate disruption, we’re talking about continuous emissions spanning over a century now, and which will have climate impacts for centuries to come. Unless we’re hypothesizing over a Yellowstone-esque eruption, volcanoes don’t belong in a serious discussion about climate change and what to do about it. That does not mean they shouldn’t be taken seriously.

        It’s unclear what relevance you think a comparison of the sulphur dioxide emissions of China and La Soufriere has to anthropogenic climate change. For reference, humanity emits roughly 100x as much CO2 per year as all volcanoes in the world combined. La Soufriere won’t change that relationship in any meaningful long-term way, barring some wildly unforeseen escalation.

        Pertaining to volcanoes and CC: (old, but no less correct…although back then they severely underestimated long-term warming caused by human activity)

        General CC info…in case you (or anyone reading this) are interested in learning about it:
        Humans cause it:
        Consensus on consensus:
        Flawed contrarian research:
        Historical climates:

        Hope this helps 🙂

        This was put in the dungeon by our suspicious demon, probably because it has so many links. Admin

        • CO2 forcing from the increase since pre industrial times is ~2w/m2 with a doubling being 3.7w/m2.
          Thats about 1.2 deg before feedback, which according to Le Chatelier’s principle would be expected to be of the negative variety, as the observations of declining water vapour in the upper troposphere support.

          For CO2 to have a significant effect (more than 1 deg) requires a massive positive feedback that has never been demonstrated.

          Please show empirical evidence of positive feedback before making claims of impending disaster.

          • The drop in polar ice coverage alone is a big positive feedback.

          • Look at the sea. There is all the evidence you need. It is rising by 3-5 mm/yr, due to thermal expansion and initial ice melt.

            Your negative feedback is imaginary, I am afraid. The IPCC reports have all the physics, the confidence levels and the uncertainties. They are a good starting point.

    • Yep looks like a new vent near the original vents. Bubbling lava to the right of the smokey new? vent it on the original Cam.

    • Looks like steam to me. From the same spot that steamed from the beginning. More water in a spring from recent storm runoff?

  2. Note. This was initially put up as a comment but Albert felt it deserved article status. The last paragraph was added by Albert and he is spot-on about Tephra. Besides, he has better references than I. I just plot stuff.

    In the dark hours last night while I was cursing a pair of wayward Owls making a lot of noise… La Soufrière had another go at it. I have yet to update my plots but I will get to it later today. I have to go figure out what exactly supposed to do by Friday. (All they really gave me was a deadline)

    • Albert was spot on too about the comment having article status.

      Thank you to both of you.

    • Really glad this was promoted to an article, the original comment was worth reading a couple of times to be sure I had understood it.

    • They are adding the possibility of lahars now.

      & the professor noted that pdc s are likely to go out to sea so fishermen need to avoid the nor west, north and north east of the island – they were discussing a buffer zone of 2 -3 miles.

      • Good advice. PDCs have no obstacles when over water. They can move quite fast.

        One added problem… PDCs are typical of column collapse and can easily be in the 800°C range. They could easily have a blast of entrained steam within them.

  3. The lava level seems to be sinking infront of the twins, I belive this is due to the main stream now reaching around the cones, and wanting to go into Meradalir(or just around the cone and then to the south)

    • it wouldn’t surprise me if a lot of the lava was entering lava tubes and heading who knows where …

  4. With this and other volcanos erupting in the past several months, I have seen a lot of conjecture that we are in a period of significantly elevated frequency of eruptions around the world. I haven’t seen any charts and don’t know if there is any trend lines being developed out there.

  5. There has been a lot of smoke emanating from one small area to the left of the twins. Nothing more exciting that that so far.

  6. Thanks Geolurking, Albert, Carl. I have hard time tell friends about this. They scared summer going to be bad. And i say no its to small. Can be bad summer anyway 🙂 But localy it can or already are a big bad thing. Hope they can bring out people from the danger zoon in time.

  7. Did something happen? I just logged on and see a bunch of quads driving and a jeep with lights. Someone needs to be rescued?

  8. It would be interesting if someone could measure the ashfall in Barbados……not just thickness, which is very sensitive to compaction, but the mass per unit area. That might help nail down the total tephra mass when detailed measurements are possible close up on La Soufriere itself. Total tephra mass will be difficult to estimate in a case like this as so much of it is falling at sea.

  9. I’m not sure if this will work. It’s a tweet I’m trying to copy over showing
    “gummih @gummih
    Gosið hefur sést vel úr Kópavogi í kvöld. Þetta er svo furðuleg staða
    Translated from Icelandic by
    The eruption has been clearly seen from Kópavogur tonight. This is such a weird situation”

    Imagine looking out your window and seeing that!

    • It has found the second gully. I am wondering whether the same may happen on the other side of the hill. Certainly there are a lot of cars there, as if they are clearing the area.

  10. @Carl; I have not seen the SO2 numbers from Iceland thus far and since it is effusive it is obviously near groundlevel. But so is chinese industrial output. So why does not Icelandic SO2 levels show up in the WindySO2- chart while La Sourfiere (and Chinese) does?

    I see Simon Carn now puts daily SO2 output at 0,4 – 0,6 Tg for La soufriere. I misread that as total thus far yesterday. But wording suggest total today for the number (and similar for yesterday). In a tweet 30 min ago.,45.151,-29.531,3,m:feCahSR

    And is max SO2 gas column height equal to ash/dust max height? Seems the ABI Mesoscale2 instrument puts column height at 18-20 km (~1 km resolution) and other instruments I have seen places SO2 tracing at below -80 deg. C. in other imagery.–MESOSCALE2::sat:GOES-16::image_type:RGB1112or13um_3911um_11um_Ash_Retv::endtime:latest::daterange:60

    Do you have any input on this? It does not add up, so clearly I am missing something (what?). Thank you. 😉

      • Yes. And it covers absolutely zero area compared to the So2 emissions from La Soufriere. Barely shows up in the Windy-chart. 120 by 30 km with mostly green levels some 10’s km away. While SO2 from La Soufriere covers, well, vast areaes with levels well above 100 ug/m2. Can not see how Icelandis SO2-emissions remotely are close to the levels we see from St. Vincent. Even Hawaii is notable in the map.

    • I can’t answer your questions but give some ideas. Regarding the height, the highest I saw in the ABI maps was 16-18km. Higher values seemed to show in only one time stamp, suggesting measurement uncertainties. Soufriere certainly emits much more sulfur per day than Iceland. But Iceland has been going on for a month. I believe that presents a model, not actual data. I don’t know whether Iceland is included in that model.

      • Thank you Albert. Copernicus delivers data to Windy. Forward (in time) is of course projections. But existing timestamps are based on data delivered from them every 11-12 hours. So latest hours might be somewhat inaccurate, but since this has gone at it since friday there are plenty of data. You will find this under the i button on the page while SO2 is chosen.

        I track SO2 (among others) fairly often and have not seen any alarmingly high readings around Iceland since the start there. But three days and a month is of course different. Are there available data of total output of SO2 in Iceland thus far? Using Simon Carn’s estimates we are at 1,0-1,6 Tg for La Sufriere so far.

        Of course at a very different altitude then in Iceland, but the data also shows ground-up emissions like I mentioned for China.

        Here is a link to the different ABI instrumentation. Only difference I find between ABI and ABI Mesoscale2 is the lens scaling(1000×1000 km for the latter). Fairly same tech but resolution seems to be different with down to 0,5 km for ABI and 1 km for ABI Mesoscale2.

        Best from Norway!

  11. #LaSoufriere erupting properly for the first time in over 12 hrs…


  12. Are they evacuating at Reykanes volcanic site? The gas cloud looks likeit’s hanging low and not dispersing on the mbl cam.

    • That answers one question… Untill the 7. of April (21 days) the eruption in Iceland has emitted (@3.000 ton/day) 63.000 tons SO2. Extrapolated at same rate till today that might be ~78.000 tons SO2 so far.

      La Soufriere stands at 1,0 – 1,6 Tg so far which is 1.000.000 – 1.600.000 tons of SO2. So stands at 13-20 times more SO2 emitted than in Iceland so far.

      1 Tg(Teragram) = 1 Megatonne (Mt) = 1.000.000 tons.

      Might be worth a correction of the article.

      • Your numbers seem correct. I got a similar number yesterday. Soufriere is of order 10 times Reykjanes in terms of SO2. That is consistent with the DRE volume of Reykjanes being around 0.01km3 so far, and Soufriere being around 0.1 km3. Reykjanes will need a year to catch up.

  13. Pre bed-time check up. Thank you Lurking (and Albert & Carl for the additions ) As ever I am in awe of Lurking’s figuring and graphs. Some is a little over my head but I get the gist mostly. (I am Math phobic ! ). I too will continue to call them Pyroclastic flows . I dislike acronyms/initialism as it makes for either CC ( complicated confusion ) or YANACAMS (You Are Not As Clever As Me Syndrome ). One has to be careful with acronyms as some IT Bots will cut them out as being offensive.
    Looking at K100 cam and seeing so many flashlights indicating many people wandering about. over a wide area. Either there are some Numpties who won’t heed warnings or there is something disturbing the official Volcano Safety watchers.Someone lost? New vent widening?
    I do hope all are safe in St Vincent. What a worrying time for them. Hats off to the St Vincent government they seem to be doing a first class job under appalling circumstances. I hope it stays at VEI4.
    I fear that if any more Volcanoes decide to join the party there will be an abundance of Doomsday Prophecies and Conspiratory Theorists. We are certainly being kept on our toes on this site at the moment.

  14. I see Mauna Loa has reached the newspapers. USGS observing a number of low-level earthquakes.

  15. There are occasionally sharp decompressive bursts of lava from the north/south cone complex tonight. The last time this tephra production occurred, we had fissure #2 open up a day or two later. The bursting needs to be watched, it is different from the normal sloshing or bubbling we commonly see.

    • Before the new fissures opened the lava level also dropped in the original vent, presumably because it is an open conduit rather than a fissure still. Fissure 2 I suspect is also an open tube now being the most productive vent and a week old by now too. Effusion rate seems sustained higher than before, so it might not need to open a new vent for a while now, these ones might just keep going for months until they are too tall, or the hell machine increases. If the vents last a long time though new vents will become radial around them which will change the risk.

      • Randall, I’m always so happy when that sort of thing happens. It means that we are getting somewhere!

  16. There was some satellite radar imagery that showed the Dome had been destroyed with an equivalent sized crater dug out by the blast. So your minimum DRE size is an ovoid approximately 950m X 250M X 200M. That is ~25 million m3 or about 1 tenth of Mt Saint Helens, which was just VEI5 and thus this eruption is probably a small VEI4 at the moment.

  17. … rough day. It didn’t help being awake for 24 hours straight cursing the owls that were putzing around the neighborhood. Then the @#$ roster woke up. Poking around reading comments and chatting with the other moderators plus the owls kept me wide awake.

    BUT…. as promised. Here is an intermediate plot showing the data points I start with. The x axis is in seconds from 4/9/2021 0:00 UTC… my reference point before it started emitting ash.

    The peak rate so far is 1834.54 m³/s when the plume was reported at FL440 (13.4 km) As Carl updated earlier. This is a FAR cry from Pinatubo 1991 at 40 km. Pinatubo’s eruptive rate was so large that it “breaks” my formula and I do not trust what it gives me. Modeled curves are like that. Get too far away from the range of data it was built from and the underlying formula begins to show it’s true nature and you can not trust the output. 7 x 1017 m³/s? likely bullshit. Mastin et al and the earlier Sparks equation it was based on were looking at thermal transport, not jetting. Pinatubo had both going on…. as well as a Tropical storm dumping water into the vent during the eruption. Pinatubo was the geological Menthos in the soda bottle.

    Now for the running total.

    So far my estimate is 1.62642364 x 108.

    For anyone questioning the precision of this number.
    Don’t get caught up with it. I was taught to provide the full output if a program spit it out. There is way too much slop in my method to assume it is that precise.

    Now… if you want to compare the plume height for a few eruptions.

    La Soufrie – 13.4 km (so far)
    Pinatubo 1991 – 40 km
    Vesuvius 79AD – 33 km (generally accepted)

    • When considering plume height you made me aware of the difference between FL advisory and observations. Logical destinction.

      But looking through all the VAAC reports (Twitter) the wording clarly relates to observations (obs) in several instances. From oldest to newest; Apr. 09/2020Z

      Except: “RMK: New EM showing cloudtop temps at -78C, which convey height at 52kft.”

      Then two advisories suggesting FL500 and FL550 (not obs). 09/2320z + 10/0500z.

      Then; Apr. 10/0940Z

      Excerpt: “RMK: …Main plume at FL470 movg ENE with the highest tops to FL520 movg ENE…” Apr. 10/1530Z

      Except: “RMK….Main plume at FL350 with hihest tops at FL500….” Apr. 10/1930Z

      Except: “RMK: Frq explosive ems lofting VA to to FL520 near summit region…” Apr. 11/0030Z

      Excerpt: “RMK: Periodic explosions lofting VA to FL520 near summit region…”

      Then no obs wording;

      -VAAC adv. Apr. 11/0610Z seems to be adv. to FL400/470/520 with no wording to suggest obs.

      -VAAC adv. Apr. 11/1130Z. Same. (To FL400/520)

      -VAAC adv. Apr. 11/1710Z. Same (To FL400/perhaps FL520)

      -VAAC adv. Apr. 11/2230Z. Same (To FL100/400/470)

      -VAAC adv. Apr. 12/0400Z. Same (To FL 100/3507400/480- most recent obs to FL350)

      -Mostly advisories from Apr. 11/0610Z as you can see and very similar going forward up untill now with VA adv (some obs) at FL400 – 440, with most at FL400/420.

      But there still seems to be obs of plumes to FL520 – 52kft . For the calculations you have made I totally agree. La Soufriere has not ejected the plumes constantly either. More like in episodes.

      The SO2 has probably mainly leveled out at ~40.000 ft and poses no long term threat based on the data. But there could be problems related to acidic sulphur rain in quite a few areas. Levels of SO2 of 100 ug/m2 to above 700 ug/m2 in the cloud spanning from western Colombia til Algeria as of now is something to look out for.

      To conclude, as per now La Soufriere has a low intensity VEI4 eruption based on observations. And it seems to have cooled its temper for now. For the life on St. Vincent that would be the best too. The water situation has started to bother many for instance.

      Our demon considered this suspicious (it is a very suspicious demon), because of the many links. Hereby released from the dungeon – admin

  18. Considering how most of us reacted to a geologically speaking modest VEI 4, it’s safe to assume that if we where to witness a VEI 7+ or Laki-esque eruption, our heads would explode and enhance the volcanic winter. The greatest honor for a volcano-phile.

    • If that is to happen, I just hope I am not driving around the southern end of Lake Taupo at the time. On an Auckland to Wellington road trip a couple of years ago (when NZ was still accessible!) it was quite a shiver of recognition when passing the place name “Hatepe” by the side of the road.

    • Someone somewhere on t’interwebs used the term ‘volcano chaser’ which quite tickled my fancy. I want to take my son on an official tornado chasing some day. But first I have other virtual chasing to do.
      @Col going to places that I have read about since childhood and which have become legendary to my brain is the best experience. I know I’m highly privileged to have no barriers (apart from DH’s longterm health) to resuming my globetrotting after the pandemic finally subsides. Eagerly awaiting my second AZ jab. #soimpatient

  19. Darn it’s going all misty& cold again – how many seasons are there in Iceland per day?

  20. Eruption rate in Iceland is reported to be 5 m3/s again, I think we will see more vents open soon. I have not been able to find anything about the deep supply since way back when the dike was first forming, but it never changed from the 15-25 m3/s rate, so I would be surprised if it has decreased now there is an actual outlet. Still very early in this eruption, a normal eruption of this scale would have not lasted so long.

  21. Eruption rate in Iceland is reported to be 5 m3/s again, I think we will see more vents open soon. I have not been able to find anything about the deep supply since way back when the dike was first forming, but it never changed from the 15-25 m3/s rate, so I would be surprised if it has decreased now there is an actual outlet. Still very early in this eruption, a normal eruption of this scale would have not lasted so long.

  22. Tremor just dropped down like before. Wonder if a new crack will be born soon.

  23. Activity seems more subdued than it has been over the last few days, too. I can only see the occasional spatter thrown over the edge of vents 1 and 2, hardly anything even from 3 and nothing from 4.

    I agree that these are signs that have preceded new cracks the last few times, but only time will tell.

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