Monte Somma & Vesuvius

Painters rendition of the 79 AD Pompeian eruption of Vesuvius.

The World’s most ill-begotten real estate, Part II

Monte Somma is an old volcano, activity started 400 000 years ago. Over the next 375 000 years a massive strato-volcano was built up at around the same location as todays Vesuvius. The main geological component is guarinite, an epitaxy of hiortdahlite, wöhlerite and låvenite. There is no known record of any caldera forming events during this long period. At the end of the period Monte Somma had an edifice containing four times the rock volume of today’s Vesuvius (calculated conservatively).

The volcanicity in the area is driven by the back-arc subduction zone caused as the African plate slams into the Eurasian plate, and then being pushed under. On the European side melt from the friction of the plates is being released through the Campanian volcanic arc. Other close by members of the volcanic arc is Campi Flegrei and Mount Epomeo (Island of Ischia).

25 000 years ago Monte Somma suffered the Codolan eruption, an ultra-plinian eruption that eradicated almost the entire volcano in a cataclysmic failure of the magmatic chamber. The Codolan ash lies on top of the Campanian Ignimbrite caused by Campi Flegrei 34 000 years ago, making the Codolan eruption the youngest of the cataclysmic events caused by the Campanian arc. The highest remaining point after the eruption is today known as Punta del Nasone (Tip of the Nose), an 1 132 meter high edifice on the caldera rim. The eruption probably had a significant effect on the population size in southern Europe.

Google Earth Image of Vesuvius. On the upper left you can clearly see the caldera wall of Monte Somma with the Tip of the Nose (1132m).

Vesuvius is born

From the ashes of Monte Somma a new volcano started to grow almost immediately. During the first 8 000 years the new volcano had a fairly unevolved magmatic chamber system. As such it could not cause large eruptions, instead it slowly, but steadily built up.

That changed about 17 000 years ago when a cycle started consisting of frequent small to medium eruptions interspersed by Plinian eruption ranging between VEI-5 and VEI-6. To date there has been 8 of these larger events in the current cycle. Calling them large might seem ridiculous compared to the Codolan ultra-plinian event, but one should compare within the cycle. These eruptions are believed to range between 5 and 15 cubic kilometers of ash counted in Dense Rock Equivalent (DRE). Compared to the 0.25 cubic kilometers (DRE) of Eyjafjallajökull these eruptions are rather large.

These larger eruptions take place roughly every 2 000 to 3 000 years. This time interval makes sense if one takes into account that the magmas needs time to fractionalize enough to evolve to the highly explosive magmas involved in these eruptions.

The latest plinian eruption was of course the 79 AD eruptions that eradicated the cities of Herculaneum and Pompeii. I will cover this eruption in a separate article in the series about Neapolitanean volcanicity. This eruption is the reason we call these eruptions plinian. The reason for that being the historian Pliny the Younger (Plinius), writing down the quintessential record of the eruption.

The plinian eruption before that was the Avellino eruption (Pomici d´Avellino) that took place 3 800 years ago. Archaeologists have noticed that this eruption had a large effect on the regional Bronze Age population.

After the 79 AD eruption Vesuvius has had numerous small to medium sized eruptions ranging from VEI-1 up to VEI-5. Some of these have been notoriously ashy. The 472 and 1631 eruptions yielded ash that travelled as far as Constantinople.

Vesuvius today is rapidly getting known as the Garbage Dump of Italy. This is due to a large amount of both legal and illegal dumping of garbage and industrial waste in old flanking vents and cones. This has raised the toxicity around the volcano to a level where one should not eat anything growing on or around the volcano. Even the fabled wines of Vesuvius are now deemed not fit for human consumption. It is sad that Man’s folly is destroying one of the world’s most beautiful vistas.

Technically Vesuvius is a somma-volcano, a type of volcanoes named after its parent volcano. The term refers to a fully developed strato-volcano that has formed inside a caldera of an older destroyed strato-volcano.

Photograph by the US Air Force. Eruption of Vesuvius 1944 taken from a bomber plane.

Risks of Vesuvius

Vesuvius can theoretically have 3 types of eruptions if we look historically. These are in order of threat-level the regular eruptions, the plinian eruptions, and a possible recurring ultra-plinian Somman event. Let us look at them one at a time.

Before we go on I would like to say that the projected death tolls for the respective eruption sizes are from figures that have been calculated by INGV, The Italian Government, The regional government of Naples, independent catastrophe mitigation experts, EU and the UN Decade Volcano Program.

The lower end figure is the best possible figures. Basically it would require functioning scientific volcano predictions, and a high-powered highly ordered Government ruthlessly enforcing evacuations and other protective measures. Basically we are talking about northern European style Government with heavy military aid here. The high figure is based on INGV being disregarded for political reasons, week or no mitigative measures taken, lack of functioning roads being accounted for, and the general nonchalant attitude in the region. I would here say that INGV will do their work; they are highly capable and very diligent in performing their duties. I just hope that they will be allowed to do it by the highly corrupt Neapolitan local politicians.

The risk is of course heightened by the high population numbers, and that people live close to, or even on the flanks of Vesuvius.

Central crater of Vesuvius.

Normal Vesuvian eruption

Vesuvius is a highly prolific volcano, and it is known to have had several instances of magmatic intrusion since the 1944 eruption. The last major intrusive episode was taking place between 1996 and 1999. So far this is the largest of the intrusive events post 1944.

It is highly likely that Vesuvius will have an eruption during this century. When it happens it will almost certainly be in the range of VEI-2 to VEI-4. One should though note that there have been two out-layer small VEI-5 eruptions since the 79 AD eruption and also that there has been a few VEI-1 eruptions. Median eruption (most likely) would be a VEI-3 size. Ash, volcanic bombs and pyroclastic flows would be the largest risk for the population.

Death rate would be between 0 and 100 000 depending on size of the eruption, and the amount of protective measures taken.

Vesuvius in the background photographed from Herculaneum.

Plinian Vesuvian eruption

Vesuvius is from a short geological time-frame ranging in on a plinian eruption. Nothing points towards that the eruptive cycle that started 17 000 years ago has changed to the better. Judging by previous behavior the next plinian eruption will occur during the coming millennium.

The risk of a plinian eruption is driven by the rate of fractionalization of the magmas. Normally this type of explosive eruptive behavior requires the volcano to not erupt for a few centuries before the plinian eruption, thusly giving the magma time to evolve as intrusions bring in new material that mixes with older colder magmas to revigorate the explosivity until the volcano quite literally explodes. This seems to not be the case with Vesuvius. One suggestion might be that there are different magma chambers that are responsible for the larger eruptions and small shallow chamber responsible for the smaller eruptions. Be that as it may, do not expect a long period of repose between a normal eruption and a plinian. Risks for a plinian eruption would be large amounts of ash, large pyroclastic floods, and lava bombs ejected up towards 40 kilometers. There is also risk of tsunamis causing additional deaths in the low laying parts of the Bay of Naples. Larger pyroclastic flows can rush over the water’s surface and hit areas that are not close.

Death rate between 10 000 and 1 000 000 depending on prevailing wind and the amount of people evacuated.

Photograph from Whiteynet. Vesuvius encircled by Monte Somma caldera.

Ultra-plinian eruption

This option is highly unlikely in the foreseeable future. Why? Compared to the size of the Monte Somma edifice we know what the maximum size the volcano can grow to before it suffers a catastrophic fail. Even if we count in the secondary caldera formation normally are smaller than the first one due to damages to the crust we still known that it will take quite some time to build the volcano up sufficiently both above ground and below ground.

If we calculate the growth rate of Vesuvius and compare it with the size of Monte Somma before the caldera event we see that it will take a minimum of another 75 000 to 100 000 years to grow to comparable size. Statistically we know that secondary caldera formations are 50 to 75 percent of the original event size. So, we are most likely looking at something in between 25 000 to 75 000 years of continuous growth before we need to worry about it.

The major risk of an ultra-plinian eruption would be ash covering a very large area, the explosions involved would instantly crush anyone within 25 kilometer. Think a hydrogen nuclear bomb shock-wave here. Between 25 and 50 kilometers there would be an initial 50 percent mortality rate due to high aerial ash content, lava bombs, and enormous pyroclastic flows covering large parts of the Bay of Naples. After the event pretty much no buildings within the 50km radius would be left standing up. Nationally deaths would occur due to ash and gas contamination. The coming year southern Europe would suffer crop failures. There will be an increased likelihood of hemispheric rapid cooling causing additional deaths and famine.

Death rate, 100 000 to 4 000 000. Supervolcano as a term is nuisance, but if one would erupt in a population the size of Naples it would have major impact. Regardless of the term, the effect on the population of southern Europe would be truly “super”. Remember, it is highly unlikely to happen.

This was the second installment in a series that will be five posts long. Remaining are the two other supervolcanoes encircling Naples, and of course the mentioned Pompeian eruption.


190 thoughts on “Monte Somma & Vesuvius

  1. Thanks Carl. In itself it is not ranked as one of the most “Dangerous” volcanoes, it just does what volcanoes do very well. . It is what can be seen in that last photo, the huge urban sprawl all around it that is dangerous. It is a catastrophe waiting to happen. I could rant on but most has been said in other TV programmes, posts and blogs.

    • I totally agree, this is not a particularly dangerous volcano, and it will most likely remain like that for a very long time.
      And as you say, the dangerous thing is the idea of locating 4 million people around 3 volcanoes with ultra-plinian capabilities.
      I would also like to add that Vesuvius is the least dangerous of the 3 volcanoes in question.

      • I am looking forward to the next installment. I have a soft spot for Campi Flegrei area . Everyone’s heard of Vesuvius but this one is not well known outside of the Volcano studying fraternity. I shall be interested to see your take on it….Been there, done that but they didn’t sell T shirts way back then!!!

    • Katla is tremoring like a jelly this morning.All the SIL around Katla stations are showing increased activity. Please note I am NOT saying there is an eruption starting..
      I am merely stating what can be seen after a relatively quiet period. I would say that if an eruption was beginning there would be many more quakes than this and ongoing very obvious heavy tremoring.

      I have been wondering about the “new ” SIL stations right on top of the Katla “Cauldera”, Austmannsbunga and Enta, Are they sort of sacrificial stations which are likely to be destroyed as soon as an eruption starts but will record important data during a lead-up? Are they a new generation of recording equipment?

      • Neither Austmannsbunga, nor Enta is inside the caldera. They are positioned on Nunataks on the caldera-rim.
        Depending on the size of a future eruption quite a few of them could become “sacrificial” SILs.
        Yes, they are a new breed of stations paid for mainly by EU.

        • Hi Diane, they get rebroadcast on floodwarn and have been down for few hours. the RUV ones are still working and show current weather to be wet and fairly windy. Alot of the Sils showing increase in tremoring but im not sure if thats weather. Infact can anyone give a quick lesson on what to look for to spot earth tremor or weather related on the charts.
          If this is not weather related then perhaps something entertaining is starting.

          • A quick introduction would not be really meaningfull. I plan to write something a bit more extensive, but sofar I have not had the time.

            Currently there is nothing exciting going on in Iceland. Except the usual waiting and guessing 🙂

      • I think Katla is getting close to the eruption. I am sorry to go against the stream 🙂

        I think the eruption will happen anytime between this summer or one summer of the next 2-3 years. This is deep magma coming to fill the sills located at 3-5km, creating extra pressure in the volcano.

        In my oppinion we will see a repeat of at least last summer activity, with many larger swarms, even some high tremor events linked to minor VEI0 activity. Lets see what happens.

        To me Katla, Bardarbunga and Askja are the major candidates for the next eruption, as well as a repeat of Grimsvotn.

        • Hello Irpsit!
          I never said that she will not blow. I actually agree with you that Katla is going to have a medium-sized normal Katla eruption in the next few years. My guess is withing this decade.
          But as you know I am a firm believer that we will see loads of activity before an eruption, something we have not yet seen. I also know you agree with me on this.

  2. @all:
    Lately the blog have been hit with up towards 50 spams per day. This is not something that the readers and commentators in here notice due to the very effective spam program (Akizmet) that we are running.
    The reason for us getting hit this hard is that we have passed 6 months as a blog, and during that time had rather stumping average visitor figures. As a comparison we are running more than 3 times the viewer numbers that Jón has openly published. My guess is that we have higher numbers than Erik does. This puts us in the highest cathegory of Google-searches. So every spam-bot on the planet finds us.
    The effect of this is that Akizmet seems to be ramping up the level of protection incrementally. This caused a rather high number of comments to be spamboxed during the evening and night. As we de-spam things this should make the self-learning algorithms of Akizmet learn that our true commentators are “friends”. But, it is an ongoing process. From time to time people will sadly go into the dungeons.
    Rest assured that we will release your comments as soon as we can. Even if you get blocked it should be gone in just a few hours (worst case) since we are pretty many working the spambox.

    The only viable alternative would be to turn Akizmet off, but that would make up to 50 (mostly porn) spams a day pop up on the blog, and that is much worse than trying to teach Akizmet manners.

    Kindest Regards

  3. Great article. At least Vesuvius is a decade volcano so whatever she does, her high profile may focus attention on the need for action.

  4. The effects of the ash from an eruption of Vesuvius might be the least of the population’s problems. How would you like all that garbage raining down on your town containing God only knows what?

      • Disinfect… yeah, 800°C pyroclastic flows will do that… but it won’t get rid of mercury, lead, arsenic and other elemental contaminants.

        Imagine the difficulty of having to deal with rocky material lofted from the volcano… as well as flaming couches, toasters, drums of waste oil (which might produce a nice napalm effect on impact), old cars, or pretty much anything else that might be squirreled away in a landfill… including squirrels or stuffed cats turned into helicopters.

        • the ones dumping think along those lines, out of sight out of mind and when she blows we won’t have to worry about it anymore, humans really are a dismal lot, present company excluded

    • Depth makes this most likely into an ice-quake. Also many of the others seem to be icequakes.

      • Swarm depth so far in last 3 hours

        0.6 km
        2.2 km
        0.9 km
        5.9 km
        11.3 km
        4.3 km
        6.7 km

        All 99.0 confirmed

        Kinda deep for ice quakes

        • Of the 15 quakes today, 15 are at shallower depth than 3 km which means they are hydrothermal or glacial in origin. There are however five quakes at depths below this which means they are relevant and need to be checked for their signature; tectonic or magmatic, before we jump to conclusions!

          • Sorry, that’s 18 quakes today with 13 hydrothermal or glacial in origin and 5 deeper which could be either tectonic or magmatic.

          • Katla has 500-700 max thick ice. So anything deeper than 2km is definitively hydrothermal, tectonic or magmatic, if confirmed to 99%. However, any magmatic move will likely be a small one. But the deep earthquakes are possibly of a bit more concern.

  5. Small swarm on Katla continuing this morning:

    07.06.201211:58:58 63.569 -19.152 1.1 km 0.2 48.85 2.8 km WSW of Hábunga
    07.06.2012 11:57:19 63.610 -19.114 2.8 km 2.4 99.0 3.4 km NNW of Hábunga
    07.06.2012 11:56:38 63.642 -19.262 1.3 km 1.3 90.01 0.6 km WNW of Goðabunga
    07.06.2012 11:56:37 63.607 -19.128 1.1 km 1.0 90.03 3.3 km NNW of Hábunga

      • M2.5 was at 2.5 km and now 99.0 confirmed

        Many more smaller ones have been added that were not there an hour ago

        looks like something brewing!!

  6. Largest Katla swarm this year? All quakes are quickly revised by IMO (i.e. first values are automatic values) – and in my opinion no need posting all up on VC as “an event” – This is “normal Katla in summertime” has arrived. It seems slightly possible that very small intrusion happened this morning, but so far nothing larger is expected. Hovever I like pointing out one thing relating Páll Einarsson and his Eyjó / Katla connection. His 18 month prediction for Katla showed only one (or two) glacial floods (that probably were small eruptions under the ice), so was he right? Yes, “there wil be rain (eventually)”. Today? Nobody knows.

    • Remember, this activity (once checked) is at the same location as the 1755 eruption, an area where several ice-pits have been noticed in the glacier. The quakes were deep at first and shallower now – once you’ve deducted the quakes associated with the glacier and the hydrothermal zone. But, nothing out of the ordinary shows on the working SILs exept for God (which for once is showing activity at Katla). I too share your sentiments that it may have been a minor intrusion but that there is no need for an alert.

      Re Páll Einarsson – as I pointed out in my article, he himself did not claim the possible July 2011 subglacial eruption as proof of his prediction. It was not the type of eruption he had postulated and you can be damn sure that if he had thought it was proof of his being correct, he would have said so!

      Just drop the idea of an Eyjafjallajökull – Katla connection. It’s not there, except in the minds of those guilty of wishful thinking. 😉

      • Henri, You are barking up wrong tree. I for one is not PE, Eyjo / Katla “mongering on a connection” and am fully into downtoning Katla today. Remember I am only two hours drive away from Katla, Eyjo, Hekla etc., and am abowe age 10 too.

        • One of the hardest things to communicate through letters is to accurately convey what you mean. While you and I see eye-to-eye, there’s the third party to consider and said the third party comes in many shapes, forms and hues. My second and third paragraphs were written with them exclusively in mind and not directed at you!

          • I like adding, there are winds aloft in Hekla & Katla areas, and these can be confused to be a runup, BUT it seems lots of low frequncy components in swarm (on Hekla seismicity it shows), so it can contain some magma signature. *not expertTM applies here*

  7. @ Carl
    Good food for thought this!
    If I may quibble, tho’, the minerals listed (guarinite, hiortdahlite, wöhlerite and låvenite) are rare Fluoride species, not rocks; I always thought proto-Vesuvius was syenitic in composition.
    Thinking back to Turkey, there seems to have been a major period of widespread volcanism 300-400 k years ago.

    re the Spam issue, would the Akizmet be able to recognise a ‘secret code’, issued by VC to us regular posters, could use so as to direct comments here?

  8. Thanks Carl for answering all my queries this morning. Thanks also to the dragons for fighting off the Spam. All you work is appreciated.

  9. June 6, 2012

    Volcanic activity from the American West to Colombia
    – Volcano-tectonic earthquake swarm continues at Popocatepetl (Mexico) with somewhat reduced gas and ash emissions during the past week at the volcano.
    – Eruptions have become smaller and less frequent as well at Fuego (Guatemala) during the past few days.
    – Tremor with small earthquakes have re-appeared (after a few days hiatus) at Galeras (Colombia).
    – Strong, but reduced amplitude (compared with last week) hydrothermal tremor continues at Ruiz (with some minor ash emission).
    – The most exciting volcano-news from the western USA is that an inflation episode (which began about this time last year) continues at the resurgent dome in Long Valley Caldera, CA. Inflation is also continuing near the Three Sisters volcano in Oregon (but at a very minor rate compared with Long Valley).


      Monday, June 4, 2012 4:08 PM PDT (Monday, June 4, 2012 23:08 UTC)

      Current Volcano Alert Level: all NORMAL
      Current Aviation Color Code: all GREEN

      Activity Update: All volcanoes monitored by CalVO’s telemetered, real-time sensor networks exhibit normal levels of background seismicity and deformation. Real-time monitoring networks are in place at Mount Shasta, Medicine Lake Volcano, Clear Lake Volcanic Field, Lassen Volcanic Center, Long Valley Caldera and Mono-Inyo Chain.

  10. Hi

    interesting and clear article Carl which has the merit of putting things into perspective.
    If I may quibble like Alan is not the view from Pompei rather than Herculanum?
    As for the garbage dumps it is a sad and criminal thing.

  11. When is it time to be concerned by what’s going on at Katla? Personally, I’d be as worried as perplexed if there were sudden bursts of hypothermal quakes in conjunction with epicurean tremor.

  12. Katla volcano (Iceland): earthquake swarm under icecap

    Thursday Jun 07, 2012 12:20 PM | Age: 3 hrs

    BY: T

    Earthquake swarm at Katla volcano on 5-7 June 2012 (Icelandic Met Office)
    A new swarm of earthquakes has started Tuesday (5 June) evening at Katla volcano. Until now, 34 quakes up to magnitude 2 have been recorded beneath the volcano, at mostly shallow depths around 3-7 km. The quakes are clustered in the SE part of the caldera, and could indicate that a magmatic intrusion is taking place in this area. Whether this is a precursor to a possible eruption of the volcano remains speculation.

  13. Curious question – If Carl or Henri were to make a “revamped” decade list of volcanoes, what would they include on it (lets cap the list at 10 or so).

    • A very good question indeed.
      I actually need to ponder upon that one. Let me just say that Campi Flegrei would be high on the list.
      I would also put in The Dead Zone onto the list. A thing to remember with the dead zone is that we have mostly seen centenial and millenial eruptions, but we do know that the hotspot has created far larger eruptions than that, and not that long ago. There are some lava field in Iceland that is well above the 100 cubic line associated with the rift.

        • Definitely so. Like Carl, I wouldn’t want to jump in and name volcanoes straight away. First, I’d like to establish guiding principles to decide candidate volcanoes – scientific principles only. Second, I’d ask “does the country have the know-how and can they pay for adequate monitoring”? There’s no question that countries such as the USA and Italy both can and should pay for it themselves whereas countries such as Vanuatu, Papau New Guinea or Zaire probably cannot and therefore should be prime candidates.

          Then again, it’s very hard to decide as we rarely know enough about certain potentially dangerous systems. As an example, should there be a repeat of the 12,900 BP Laacher See eruption, Europe would struggle to make it through although in direct numbers it might not be as “impressive” as some other systems. The problem is that we don’t even know if it’s impossible or not – the EEVF (and the others too) isn’t monitored at all.

          • I think one could do it on a number basis.
            Maximum deathrate at median eruption if it happens undetected divided by years in likely repose between eruptions, and then vectoring in (by division) if the country has an effective mitigation service rated on a scale from one to five.

            The unknowns are as always a problem of course. But, one can not always take them into account.

            For me a Decade Volcano is not about the biggest and badest, it is about the volcanoes that is most likely to whack a large amount of people. Hekla is an example of a ludicrous decade volcano. It is fairly unlikely to kill people (except tourists in the summer).

            And it would be a hell of a job going through them all.
            For instance, Vesuvius gets a value of 200. Ischia 80 and Campi Flegrei 25 if we count median eruptions. Highest number is worst. Why? It is the volcano most likely to whack 100 000 people. By far. Why the 100 000 people? Because that is what an undetected median eruption would be likely to kill. Then divide that with the 100 year average repose time, divided again by the maximum of five for INGV (they are good). One could of course factor in that the politicians are buffoons…

            It kind of gets gruesome…

          • And the rub of it all is that it’s the one noone knew about or considered seriously beforehand that’s the deadliest. A system thought “extinct” or “dormant” such as Chaiten (or Pinatubo for that matter) with the early signs not noticed because there’s no monitoring leaving detection and understanding until it’s on the final day or few days of the run-up before the eruption. Well-behaved volcanoes that erupt regularly to semi-regularly every decade to century or so such as Hekla, Etna, Popocatepetl, Merapi pose little danger if people choose to live at a sensible distance. But a Pinatubo-style scenario at Colli Albani or an Eldgjá in Aukland or Canterbury… …(shiver)

          • Perhaps it would be better to split the list into two separate categories- One being “worst case” scenarios of non-supervolcanic origin, and the other being based off a more traditional scale that’s based off a likelihood to erupt probability

            Then again, the “worst case” category would just be more food for 2012’ers, not that it wouldn’t be interesting to think about..

  14. I know i repeat myself but the steam column over Etna is getting more and more imprssive in the last days.
    Cam 2 is pretty good.
    Is this a usual effect between 2 paroxys? I mean this is much more then only a few fumeroles or anything Popo does, not?
    On cam 2, from the left to the middle of the picture should be serveral kilometers.

    • @luisport – I consider Katla quakes under 2,5 not be significant when there is ongoing swarm *please consider what maybe important or not – only my opinion*

          • Magnitude is most important, after that depth, and third would be location.
            Remember that it takes 1000 1M quakes to make the same damage as 1 3M quake.

          • And Katla is placed in a rifting region. So earthquakes can be related to tectonic process, with no big magma moves connected to it. These earthquakes have been happening for years!

  15. Well…. that answers that. Somma peaked my interest when it came up in the other installment.

    Mentioned in the last thread:

    First Phlegraean Period: 39.28 ± 0.11 ka. bp
    Second Phlegraean Period: 35,000-10,500 bp
    Codolan eruption: 25,000 bp
    Laacher See: 12,900 bp

    Apparently, being a hominid in Europe during this period was a ‘long row to hoe.’ (difficult task)

    And in poking around at this… the Laschamp Event was from about 41.5 ka to 39.75ka (*eyeballing a chart)

    Now I am wondering if one of the ideas behind Geomagnetic excursions may have some coincidental support from the high level of activity in Central Europe’s rather festive volcanic provinces.

    From Wackipedia:

    Scientific opinion is divided on what caused geomagnetic excursions. The dominant theory is that they are an inherent aspect of the dynamo processes that maintain the Earth’s magnetic field.


    A minority opinion, held by such figures as Richard A. Muller, is that geomagnetic excursions are not a spontaneous processes but rather triggered by external events which directly disrupt the flow in the Earth’s core. Such processes may include the arrival of continental slabs carried down into the mantle by the action of plate tectonics at subduction zones, the initiation of new mantle plumes from the core-mantle boundary, and possibly mantle-core shear forces and displacements resulting from very large impact events. Supporters of this theory hold that any of these events lead to a large scale disruption of the dynamo, effectively turning off the geomagnetic field for a period of time necessary for it to recover.

    • Note: the Codolan event was added to my short list from the last thread, it wasn’t in the original.

      • I have another one for you 33 000 years ago. Size of the Phlegrean Ignimbrites. Most likely worse on the killometer though. Oh, another of the neighbour of Naples of course.

        While I am at it, I love the name Vulcano Vultura. Smack in the middle of Italy. Dead as a door-knob, but cool name non the same.

        • I am beginning to hate Italy.

          Every damn place you turn is a volcano that has erupted in the last 60 thousand years.

  16. Regarding Katla!
    Yes there has been quite a lot more activity at Hábunga than there has been the last half a year.
    But still this is nothing that really exites me. They are far to few (think 100ds per day), with at least 50 above 2M and 10 above 3M, and that is per day. And I would like it too run for weeks before the eruption starts.
    What we have now is too shallow, too small, and far too few.

    Also, after a few days when Lurking did one of his plots we would see that the quakes form a column down into the deep.
    There would also of course be rapid and very large GPS movement starting.

    We would not be guessing if it was really happening, we would know. And I promise to write a post about it before the eruption starts.

      • I always stand for my bets.
        But the part about me being in Adams costume while doing it, and then dancing was entirely an idea of Dianas :mrgreen:

        • Sounds like a tradition in the make. Every time an Icelandic volcano erupts we will eat our hat and dance around in weird costumes. 😀

          • Well, let us say that Adam was not that great as a clothes designer. It was first after getting some aid by the snake that he invented the fig-leaf.
            (Adam’s suit = naked)

          • Me? I’d be entirely philosophical about it but if you were thinking along the line of “unusual foodstuffs”, I’m ready to offer a deal: The choice of two dishes; a) a bag of fried cockroaches, and b) a can of fermented herring. The witnesses choose what I should eat and make a meal of the other one.

          • Carl, I’d happily eat the cockroaches as long as my judges swallow their delicacy without wincing! 😈

        • I though have one allready… 😉
          But I agree, it is a long way off still.
          I though have to give it to the fans of Katla, the 3.2M is the first promising quake in about a year.

    • Yepp, we have a Star.
      Reason for it probably being because it was really long period (magmatic). That is why it took time to calculate it by hand.
      Yes it is fairly shallow, but it is above the limit for an icequake, and the type of quake gives it as magmatic.

      (Thanks to Islander who pointed my nose in the right direction)

      • Something smells Fooonky with this quake though.
        The 11.57 quake (2.8M currently) is longer, and larger. Either they mixed up the time, or that one will soon be bopped up into the 3.5M+ range.

        • And now the star is downgraded again…

          Is it just me or is the duty officer reading my comments? Sometimes it feels like it.

        • someone is undecided in Kingdom of Mine, revised again in steps in last couple minutes, *ah, so not attract Daily Fail clan*

          • I am a bit surprised at this running up and down.
            IMO is normally a bit more assertive than this, and they never seem to give rats bone about the Daily Fail clan.

  17. I must say, the Italian volcanism is really interesting to me. I never realized it until doing a bit of mild research how active the volcanism was all across Italy. I had always figured all volcanism was centered around the coastal islands, the Naples area volcanoes, or Sicily (etna).

    Lo and behold, as you go further north, there are four to five more massive calderas from past ultra-plinian eruptions, all that are around 10 km in diameter. Not all of these are super-active, but I don’t believe they’re extinct either. As you would expect from caldera systems of this size, they don’t blow up that often, but when they do, it’s pretty big.

    Is this just the nature of mainland Italian volcanism? Just seems like it’s an area where they don’t blow often, but they do blow big.

  18. Concerning Katla: in a nutshell, I think this activity is still nothing special. It does not make me worry the least. Its normal summer time activity. But the increasing slowly number of deep earthquakes means we are slowly getting close to an eruption. My bet is anywhere from this late summer (still unlikely as of now) to until end of this decade. I think Katla will most likely do its show in 1-2 years from now, I bet for summer 2013 or 2014.

    Until then, I expect many false wows, and a period of several months of deep earthquakes, kinda of Geolurking plot showing a column upwards. If Eyja is any indicator, this can last for several years! So, the wait might be long still!

    Personally, I dont want to see Katla erupting, while living in Iceland. Too messy.

    Quake magnitude downgrading: well, one thing I always heard is that earthquakes there are often quite hard to determine their magnitude, I don’t know exactly the reason why. I have personally felt two 3.0 near Katla, in Thorsmork in separate ocasions, in one ocasion I was at top of Myrdalsjokull. Well, its a shaky place, and increasingly more so in recent times.

    • Irpsit. This morning shows how right you are! All quiet. It was possibly a magma intrusion. I have seen far more dramatic Katla sessions so all I do is comment when there are more than a few quakes and of course with Magnitude and depth. The reason for this is to see if a jökulhlaup follows. For those who are not sure what this is, it is a glacial flood, full of boulders of ice that sweep down the river valley. They cause major damage to roads bridges, livestock and of course anyone in their way.You can find more dramatic videos of Jokulhaups or Lahars as they are called elsewhere. However this clip shows the extent of damage by just the relatively small flood last July when ice on Myrdasjokull, above Katla suddenly melted. Whether this was just the result of geothermal activity or a small eruption that never made the surface is unknown. The flood washed away a bridge and part of the main Iceland Ring road .I chose this clip to show how dangerous these floods are. They come with little warning and carry not just huge blocks of ice but also as you see from the clip boulders and other debris. We did see an earthquake swarm prior to this and there was dramatic change in the SIL recordings. But in the scale of things this was a “minor” event in Iceland. a new bridge was built and the road open within the week! Again Iceland shows how to “keep calm and Carry On”

      • PS. This is for the benefit of Volcanocafe guests who are just learning. The name Jokulhaups is Icelandic for Jokul = Glacial Haulp = flood burst………. maybe our icelandic friends can translate this better than I. 😀 Lahars are slightly different but often these two terms are wrongly lumped together. Lahars are made of muddy debris which tends to solidifyas opposed to the jokulhaup which contains more Ice than small rocky particles.

        • Hi all. That’s an interesting clip, Diana. Certainly some real power there.

          here’s the new bridge 🙂

          I’m sure one of the resident Icelanders will correct me if wrong, but I believe there were/are plans to replace this rather temporary structure (put up, as you say, in a week) at some point, but they are not doing it just yet. Now … are they waiting for Katla to do something first?

          • eh, yes and no. It was planned building a better permanent bridge (with two lanes), but the temporary bridge probably is just good enough for now than, and its common sense waiting setting up new one, untill after next Katla event(s). Reason for this is also, the sands may change dramatically in next event(s) and then it be troblesome tame river to run under new bridge (might lead to another location if built too soon).
            re: Jökulhlaup, its “Jökul” and “hlaup”. Glacial-Run is exact word for word translation, (alternative is Fast-Glacial-Water-Runoff) and as everyone knows its exactly what you need do if you happened be there in its path. They are formed by two basic processes, dictated by time/magnitude. First “normal” Hydro-Thermal melt forming pockets (lakes) under the Ice and run off periodically, the other by sudden melt when Magma (Thermal) intrusions pentrate the crust and (like blowtorch) make sudden pockets of melts, say in 30 min, 1 hour etc. and then this runs off. Then you can have variations on these, depending on time, amount of event and runoff properties of the area in question. Normal summer melts usually run off in constant way but making dayly spikes, more in evening and less in morning.

        • Ah ha! islander. I think you have explained this rather strange looking repetitious paattern in the last few days on the Askja SIL. Correct me anybody if I am wrong here.
          Quote from Islander. June 8, 2012 at 11:32
          “Normal summer melts usually run off in constant way but making dayly spikes, more in evening and less in morning”.

          Look at the patterns from 30/05 to 04/06. This area is remote, far from the coast and there are not many vehicles or other human “noise” that could explain this

    • Its 229 years now and time does tick.. Jepp, GeoLurk has “average” at 142 (I think). Correct me if wrong. BBGN all

      • Haven’t double checked.. but that’s about right.

        And a note for all… Volcanoes do not care about Normal Distribution or silly mathematical trends.

        They do what they want, when they want, and not one moment sooner.

  19. A short note on Italy…

    Over on the Eastern side of the Adriatic, several phases of subduction, reversal, subduction, reversal (rinse-repeat) have gone on. In Italy, I think at least one cycle like this has occured. A seemingly vertical slab segment may be hanging under the Northern Appenines (see Adriatic Bop).

    All this, plus the ever moving monster plates of Africa and Eurasia make for a lively and active setting. Some of the magmas are carbonite (Vulture) and that points at the incorporation of limestone like material from ancient seafloors.

    • That is interesting! IIRC you had a figure showing just that in relation to the Italian quakes. With a slab that deep down, it will eventually melt, and the melt will eventually surface – over geologic timescales. The Earth is not as peaceful and tranquil as we imagine it to be, nor will our, the European one, be so forever…

    • Interesting.

      When I plotted the EQs in the area, I did not see many (if any) deep EQs at the northern end of the Apulian Plate. Does this mean that I need to change the parameters for my plot or is the dangling slab at the northern end relatively aseismic? Off to check Adriatic Bop again.

      There is a lot of limestone in the Alps. Is the limestone from the bed of what was the Tethys Ocean?

      • You will probably not find the slab in the quake plots. It only showed up in a couple of papers that had done tomography of the area.

  20. I have just had my very own personal doomsdayers visitation, on my front door step,
    “We would like to discuss how bad the world has become since you were a girl. I am sure you will agree all those years ago things were much better”…..
    I let them have it with both barrels!!!
    I am furious that they assumed I was soooooooooooooo old for a start! “All those years ago”? GRRRR!
    I then told them roughly the following…
    I can look up at a plane flying over and not worry it is carrying an atomic bomb.
    Non of the children here are likely to die from TB, diptheria or Polio.
    Thanks to the internet there are better world wide communications and knowledge sharing and I am lucky I can buy any foods I need. Nothing essential is rationed and people are living longer.
    Here in the west at least, things are better. Time will get the rest of the world back on a forward track.
    Reading Henri’s comment above, everything is put in perspective. No matter what human follies occur, the plates grind on, magma rises cools and is recycled, We are less than a microbe sized part of a vast whole.
    ………..and I need to get ready for my Tai Chi class.

    • oooo, door knockers – not something that happens in the UK too much, we had our first one a month or two ago, exciting times!

      Your story reminds me of my old Geology teacher who used to invite them in for a 2 hour “lecture”, and also reminds me of my English teacher who happened to be chopping onions when they knocked and answered the door wearing safety goggles and carrying a large kitchen knife – I’m sure she made a lasting impression 🙂

      A belated thanks for your post on the effects of seismic air guns on animals – it was worth the wait!

      • Mormons while butchering half a moose… I was wearing an apron and wellies, not much else.
        Imagine their look when an almost naked man covered in blood opens the door with a bloody knife in his hand.
        I tried to invite them for coffee… :mrgreen:

        • I had some fun with the local branch of the Witnesses some 30 years ago. I offered them the hospitality of the house, let them plead their case at length and insisted they return which they duly did with back-up. Then, at their entreating, I went to one of their services after which I had their head honcho agree that after a weekly dose of sin and heresies, a generous dose of brainwashing was just what they needed.

          They never cottoned on…

          • Hitched a lift once (Newbury to Oxford I think) with two very, I mean very, smartly dressed guys in a tiny car, speaking American…
            Inevitably I asked them what they did…
            Missionaries from the Church of Jesus Christ and the Latter Day Saints (Mormons)…
            So I said ” I guess you’d better tell me all about it…”
            Anyway, the gist of it: there’s already been a second coming, South America, some time since 1 A.D. 🙂

        • an old guy was walking along the road and on the other side a couple of Mormons where also walking, the old gentleman waved them over and they started talking,
          the old timer then said: you are Mormons, they said: yes we are,
          the old timer said: you are allowed to have many wives, they said: yes we are
          the old guy said: you should be bloody well hang for that, they said yes we are

    • Diana! 😆

      But what if they had said: “Apart from from sanitation, medicine, education, wine, public order, irrigation, roads, a fresh water system and public health…” ?

      • Answer… Hitler, Stalin, Pol Pot, Mussolini, Mao and farting pillows as the end all of humour.

  21. Hi People, Maybe we noticed we have a new RSS Feed in the sidebar linked to Claudes Blog . Because he is following so many voclanoes of the world so closely and he is so up-to-date and…
    if you check that link right now… He is mentioning that Etnas tremor seems to be rising fast.

    So maybe …

    Woohoo, i was wondering where that comment went, I LANDED MYSELF in the spambox. rofl
    As i am trying to teach Akizmet i am setting it free now, so maybe it learns, i am not spam but a dutyful dragon
    ( ALL: Excuse the double comment)

      • arg missed that. I have quite a collection of animals on volcanocams, Bird, Butterflies, Geckos, but most likely i would not have been fast enough to grab a screenshot.

  22. Great post from beginning to end. Thanks all.
    I can’t believe my eyes that the small area around Vesuvius is jam-packed FULL of people, property, streets. There’s no way out. Just nonsense to live there. I’d rather live on the New Madrid fault, in a high rise, on the river IN St. Louis. No, make that Kansas City, etc.

      • I mentally changed it back to St. Louis. Anyway, my best friend lives in…uhhhhh…one of those. LOL I’ve been hearing I’ve lost it. Whatever. I told my friend to move away from the river. Awesome house though. So she got another place up some hill somewhere, still a-lookin’ at the Ol’ Miss. I said DAYUM, Sandy, my God. Now you will get totally shaken up, AND your hill will collapse into the river and, well, figure out the rest. She just said there’s no pleasing me. Now she has two houses.

  23. Hi People
    We have a new RSS fed to Claude Grandpeys blog in the sidebar. He is always very up-to-date when it comes to volcano news.
    And if you check it right now, he says Etnas Tremor is rising.
    Keep an eye on that maybe.

  24. I hereby solemnly declare and swear that todays lava picture is not Photographed by the famous author Robert Jordan. Alan is though more diabolic than ever to compensate this.
    Name that Lava XIV will be published at 16.00 BT (Blog Time).

      • Mount Rainier was named by an explorer who really loved his dog, but not how it smelled when wet. So, we he christened the Mountain with the words;
        “Oh my God, let it not be Rainier”.


        • There’s a rather impressive volcano in the ring of fire whose name when translated means “your finger you fool…”
          The europeans arrived, pointed repeatedly at the mountain and asked over and over again; loudly and slowly: “What is it called?” 😀

        • Your gonna have to cough up the name. The only reference I know of is from Terry Pratchett, in “The Light Fantastic” of the Discworld series.

  25. And…
    I absolutely did not know what I just learned… It was surprising, but not illogical. And no, it is not about crumpets.
    All will be clear on Sunday.

  26. And I did not know that either…
    There is only one place one can find a volcano with the largest ever eruption in the mediterranean… In the pants.

    I think I will have to add yet another post to the Italian Job…

  27. Pingback: Not drowning, just waving | Zoopraxiscope

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