Types of Volcanic Eruptions

The tell-tale mushroom cloud of a Plinian eruption.

The tell-tale mushroom cloud of a Plinian eruption.

After lurking about on this blog since the beginning, and seeing so many requests for explanations of volcanic terms, I decided to try my hand at creating some vocabulary lists.  So here’s one on types of volcanic eruptions. Unfortunately, different names have been applied to different eruption types over time, creating a fair amount of confusion.  I have tried to indicate these where applicable.

There are several basic types of volcanic eruptions, which can be broken down by a combination of vent types and volume of ejected matter.  A volcano, through its lifespan, will experience one or more of these types.

Effusive eruptions – eruption column <2 km.  This really covers a range of types, all with the same basic characteristic of gentle flows of lava with low amounts of gas, thus producing low amounts of tephra or ash.  The main types are Fissure, Flood, and Hawaiian eruptions.

Various types of eruptions based on the ash columns they produce.

Various types of eruptions based on the ash columns they produce.

Fissure Eruptions: These eruptions come through a fissure line or set of cracks in the ground instead of coming out of a volcanic crater.  The Laki eruption is a prime example of this.  The lava involved tends to form fire fountains, and be more liquid, allowing it to flow readily.  Fissure eruptions can lead to the creation of a volcanic cone, as happened with Mauna Ulu, Hawaii.

Flood/Plateau eruptions:  These are fissure eruptions, but on a much bigger scale. The volume is bigger and there are repeated large eruptions. The Deccan Traps (India) and the Columbia River Flood Basalt along the Snake River (USA) are a good examples.

Hawaiian eruptions: These are gentle eruptions that tend to come from a lava lake or central point instead of a fissure. Lava fountains several hundred feet high are normal.

Flank eruptions – these are eruptions coming through the flanks or sides of a volcano.  They tend to occur when there is a combination of weaknesses in the rock forming the cone and not enough pressure behind the lava to get it to the top of the volcano. Some consider the ongoing eruption at Kilauea Volcano to be a flank eruption as it is occurring on the east flank of the volcano.  Some have also called these fissure eruptions.

Typical Hawai'ian eruption with fire curtains and lava flood.

Typical Hawai’ian eruption with fire curtains and lava flood.

Submarine eruptions – these are eruptions that occur underwater. When they near the surface, they are indicated by discolored and boiling water, steam, and/or pumice rafts.  The depth of the water at which to eruption occurs will affect the type of lava flow.  This is an area of active research, and I have not found any definitive descriptions so far, though I think in the end that there will be multiple types defined.

Subglacial eruptions – these are eruptions that occur under glaciers. They are often indicated by sudden rapid increases in melt water (jökulhlaup) that are not seasonal.  Icelanders know these very well.  Due to the weight of the glaciers, it takes a substantial eruption to break the ice, and so a bit of steam and the abrupt release of melt water may be all that is visible of the eruption.

Summit eruptions – these are eruptions coming from a volcanic summit. This is the type of eruption most people will immediately think of when asked.  The following are all summit eruption types:

The VEI-scale. The amount of explosivity determines the type of eruption.

The VEI-scale. The amount of explosivity determines the type of eruption.

Strombolian: eruption column <10 km.  These are characterized by repeated small eruptions of cinder (most common), lapilli, and bombs to heights of a few tens or hundreds of feet.  Sustained columns of ash are not created. Lava flows may or may not accompany the eruption.  The name derives from the most common type of eruption at Stromboli in Italy.  Magma tends to be basaltic and of a higher viscosity than that from Hawaii.

Peleean: These are violent eruptions of rhyolitic or andesitic lavas that tend to form lava domes, which then collapse and form pyroclastic flows. The name is derived from Mont Pelee in the West Indies.  Some group these in with Plinian.

Plinian/Vesuvian: eruption column <45 km. These are powerful eruptions of gaseous siliceous lava (dacitic to rhyolitic) that can last anywhere from a few hours to weeks or months, and are the normal type of eruption for stratovolcanos.  If enough lava is extruded, the cone can collapse and form a caldera.  They produce large volumes of pumice and ash, and have a nasty habit of creating pyroclastic flows (such as the AD79 eruption of Vesuvius that took out Pompeii) and lahars.  The name is derived from Pliny the Younger, who first described them via his report of the eruption of Vesuvius.

Sub-Plinian: eruption column <30 km.  Same as Plinian, just smaller.

UltraPlinian: eruption column <55 km.  Same as Plinian, just larger.

PhreatoPlinian/Phreatomagmatic: eruption column <40 km.  This is the eruption of solid rock and steam.  No new magma is released, it is all derived from surface or underground water hitting hot magma. These tend to form maars and tuff rings.

The Strombolian type with rains of lava bombs.

The Strombolian type with rains of lava bombs.

Surtseyan: eruption column <20 km.  This is a stromblian eruption that involves a lot of water.  The moist obvious example is the eruption and creation of the island of Surtsey off Iceland.

Vulcanian: eruption column <10 km.  Gaseous silica magmas (andesitic to dacitic) are usually associated with these. They start with eruptions that clear the vent of old, solidified lava, progress through multiple explosions of ash and tephra, which produce large ash clouds, and will usually finish with a thick, viscous lava flow that tends to form domes.  The SakuraJima eruptions are usually of this type.  The name is derived from Volcano in Italy.


Primary sources of information:

http://volcano.oregonstate.edu/education/vwlessons/kinds/kinds.html.  The primary sources for the classifications are MacDonald (1972), McClelland and others (1989), and Williams and McBirney (1979).




171 thoughts on “Types of Volcanic Eruptions

  1. And straight from being a lurker to making an Article that will end up in the Hall of Fame of Explanation-posts. This is one of those articles we should have done years ago.
    Very nice one Fran!

    • Thankyou Fran, very nicely done, when can we expect the next one? 😀
      You will have to de- lurkificate now…

  2. Good post Fran.

    What about Tangaroan eruptions, the was an article in Nature about them, they are like underwater lava lamps 🙂

  3. Great informative article, although I have small disagreement in one statement. ( I hope I don’t come across as snarky in stating this as this was a great, well written post!)

    “Plinian/Vesuvian: eruption column <45 km. These are powerful eruptions of gaseous siliceous lava (dacitic to rhyolitic) that can last anywhere from a few hours to weeks or months, and are the normal type of eruption for stratovolcanos."

    One thing that should be mentioned is that you don't need Dacite or Rhyolite to form a large eruption, and not all Dacitic or Rhyolitic eruptions are large and super explosive. For example, Tambora's 1815 eruption was predominantly andesitic. Masaya erupted a VEI-6 eruption with Basaltic Magma (source http://www.volcano.si.edu/volcano.cfm?vn=344100), and Colli Albani erupted a VEI-7 with basaltic magma (source http://www.valutazioniambientali.it/download_manuali/The%20Colli%20Albani%20Mafic%20caldera.pdf)

    Similarly, there are very small monogenetic volcanoes that erupt Rhyolite in the american southwest. Having explosive magma does help create large explosive eruptions, but it only will create huge eruptions if there is a huge supply of magma that's ready to be erupted. Basaltic plinian eruptions are also quite rare, but they are indeed possible.

    My other discrepancy is that stratovolcanoes also do not typically erupt in plinian fashion when they erupt. If they did typically erupt in plinian fashion, they would never build into stratovolcano edifices in the first place since there would never be any opportunities for the edifice to grow before being blasted apart.

    Plinian eruptions are not the normal expectancy for stratos, and aren't really the normal expectancy for any volcano in the world. I would typically expect lava flows, strombolian eruptions, or phreatic detonations more often than plinian eruptions. One needs to only look around at the plethora of stratovolcanos that are currently erupting right now, none of which are erupting in plinian fashion (Shiveluch, Klyuchevskoi, SakuraJima, Lokon Empung, Fuego, etc).

    • Although there are the obvious exceptions to everything, it is though still the basic rule. We all need a good rule to break you know 😉

      I think though that everyone will understand that rhyolithic and dacitic volcanoes can have small eruptions.

      One thing to remember is that all out basaltic volcanoes from hotspots also can form rhyolitic magma. Eyjafjallajökull and Askja are splendid examples of that.

        • Basaltic, but parts of the magmatic reservoir system could easilly contain rhyolites.
          Basalt high in volatiles can though erupt explosively, especially if there is a readily available source of water, and Katla has both hydrothermal water and a honking huge glacier ontop to draw water from, and that makes Katlas basaltic supply so explosive.

  4. Frans the man! (well not probably) but a hearty welcome to the community! This place just keeps getting better and better.

  5. Very nice article. However, there is one slight mis-understanding from one of the charts. Specifically, the one under the “summit eruption” topic.

    The VEI scale, for all it’s deficiency, is still volume based. Basically this means that any eruption can reach any VEI level, if it goes on long enough.

    Using the heights of the first graphic that list the types of eruptions vs the plume height, here is a better estimation of the resultant VEI after a few hours of holding that sustained plume height.

    This really highlights just how stupendous a VEI-8 is.

    Remember, this plot ASSUMES that the eruption maintains that height of a plume for the indicated number of hours.

    • And then we should remember that according to stratigraphic layers and other things it took Aniakchak about 48 hours to achieve a VEI-6 (small one), and less than 2 minutes to go from VEI-6 to VEI-7… The really big ones are probably insanely fast, otherwise the orifice of the blasted open magma reservoir would be just to wide to sustain the tremendous output. This is a very interesting subject really.

        • Am I a bit um dense, but shouldn’t the diameter of the vent be considered here? Novarupta was a small vent high volume eruption so probably involved a high eruptive column from jetting with convection doing the rest. But what about a trap-door caldera like the Kaingaroa ignimbrite in the TVZ? Maybe the vents on these things are so huge you just don’t get that kind of height?

        • The Mastin equation is designed as a rough estimate for output volume based on sparse data, such as just column heights. It was intended for volcanoes that are difficult to get observations on.

          Will there be some error in the calculation verses the actual? Yes.

          However, the basis of the calculations are from the heat content of the eruptive material. That was the take off that Mastin did over the Sparks equations.

          As an example, for a 10 km plume, Mastin calculates 794.9 m³/s DRE, The Sparks equation calculates 1002.5 m³/s.

          • Sorry for the re-run. We’ve been here before haven’t we. I knew it as soon as I posted the question. Off to look for those gingko pills.. they are meant to help for this kind of thing.

          • Nothing wrong with a re-work of what the Mastin et al formulas are about. People have a tendency to read numbers like these as cold hard fact, when in actuality they are estimates.

            Giving me the opportunity to point that out is appreciated. I have been toying around with the idea of trying to make that paper, or the logic in the paper, a post, but I am a bit tangled up with work like stuff. Not really work, but negotiating how a 3rd party initiated call will be run and who does the parts support, or whether I am to be paid to drive 134 miles out to the site just to say “yep, it’s broke.”

  6. Trying to figure out how much earthquakes, nuclear weapons, and large impacts, might change the tilt of the planet.

    We know that the Chilean earthquake has changed in 10cm the tilt of Earth. Therefore, the Chicxulub being about 208.000 times more energetic than the M9 earthquake, it probably displaced the tilt by 20km. This is not much, it is about 0.2% of the distance from the pole to equator, or around 0.2º inclination.

    If a body around 1000km diameter (about 100 to 150x larger) would impact the planet, like it did several billion years ago, it would partially destroy the planet and create a moon (like it did) and, if we would keep the same (very very rough) estimate, the tilt of the planet would be changed by around 20 to 30º (which is about the current tilt).

    Going to a smaller scale…

    The largest nuclear bomb (the Tsar nuclear test), probably disrupted the tilt in 2cm, which is still quite astonishing feat, in my opinion. More scary is to realize that a full blown nuclear world war of about 2000 similar-sized thermonuclear bombs could therefore the planet tilt by 40km, about the double of energy of Chicxulub impact, which is something that certainly would result in a 99% mass extinction.

    And the planet shifting its tilt by almost 0.5º, which would probably be catastrophic. That shift is enough to result in big climate change just by itself. Now add that to the nukes and dust impact on global temperature.

    In my opinion, people worried about pole shifts should probably worry more with the possibility of a nuclear war, something that is still very much possible, although highly undesirable! Those doomers would do best to spend their times to lobby against nuclear weapons rather than warning about a possible pole shift.

    • Uhm… No…
      You forgot completely to vector in the not so small factor of angle of impact (or which way the fault faces) for the energy in question.
      Let us start with the Japanese quake. It speeded up the planet and did not change the tilt. Why? Because the faultline released the energy in a direction that accelerated the planet and as such did not change the tilt. Chixcoloub was a straight down impact close to the equator, and as such did not make a big difference on tilt.
      Now on to Tzar Bomba, it was uniformly distributed globular blast, as such about 27 percent affected the surface. And to further complicate things we also need to ramp down the energy level on Tzar Bomba since it exploded far up into the atmosphere. So, after that we are down to about 5 percent hitting in the direction that would induce tilt. Now we also have to recognize that it was mainly air movement together with heat and radiation. Neither heat nor radiation transfer bupkis of movement to the ground, so now we are down to about 1,7 percent of the initial energy. Sadly air movement is very bad at transfering energy into the ground… So, about 0.2 percent of the initial energy would have been transfered, and judging from the time of day it caused a counter-wobble in a 90 degree direction from the tilt.

      Regarding the 0.5 degree tilt change being catastrophic. The tilt will just continue to increase in its own merry time. So, in about 54,5 million years it will have tilted 0.5 degrees, and that tilting will continue untill the North is tidal locked towards the sun. This is not caused by anything except orbital mechanics, some tiny wobble set this off a long time ago, and after starting it is a irreversible process. Nota bene, tidal locking one pole towards the sun is the only end state stable solution in a multi body system.

      • Incidentally the tilt is what drives plate tectonics to mainly drive northwards nowadays. If you ponder it for a while you will now understand why there is so little sub-aerial land below the equator… 😉

        • I don´t quite get it why the tilt should drive the plates to the north. Wouldn´t any differences in centrifugal, gravitational or whatever forces cancel themselves out throughout the year, because the poles alternate in facing the sun summer and winter?

          • Actually there is a very very minute difference to that making the north ever so slightly sunny.
            Now comes the interesting part. Is the tilting caused by the higher mass in the northern hemisphere, or is the tilting causing the mass to migrate northwards. Have not found a good answer to that.

    • Major Global Changes:

      • The Earth is not strongly disturbed by the impact and loses negligible mass.
      • The impact does not make a noticeable change in the tilt of Earth’s axis (< 5 hundreths of a degree).
      • Depending on the direction and location of impact, the collision may cause a change in the length of the day of up to 1.08 hours.
      • The impact does not shift the Earth's orbit noticeably.

      • Impact Effects Calculator

    • “The largest nuclear bomb (the Tsar nuclear test), probably disrupted the tilt in 2cm, which is still quite astonishing feat, in my opinion. More scary is to realize that a full blown nuclear world war of about 2000 similar-sized thermonuclear bombs could therefore the planet tilt by 40km, about the double of energy of Chicxulub impact, which is something that certainly would result in a 99% mass extinction.”

      I’m sorry, there’s a major logic FAIL there.

      Tsar, and Chicxulub, were *point sources*.

      A full-blown nuclear war would be thousands of detonations, *all around the globe* – or at least the northern hemisphere.

      So the *net* effect would be *zero*, or close to it.


    • Hello!
      I read the paper. Sadly the writer missed that it is a bi-tephra and his analyzis method therefore will be flawed. The Thira eruption is definitly set to 1628BC from dendrochronological records and as such is not depending on the GRIP core.
      We know we have two large eruptions within the span 1600 to 1650BC, this from C14 dating, namely Aniakchak and Thira (and Thira we know to be 1628). Well, there should be two ashes in the GRIP but there is not. As we take apart the ashes we see variations in the samples caused by dual ashes. This has also been compared with Ice cores from Alaskan glaciers and Ice cores in Svalbard.
      So, in the end we can with a fair bit of confidence state that both happened in 1628, and the GRIP plays a rather insignificant part in it.

            • Hm…
              I think that is a conglomerate melt. Ie, that it is an icelayer that has the combined dirt of several years ontop of it. And since it is so high up what is above is most likely last years snow. So, probably Grimsvötn, Eyja, Grimsvötn and Hekla. Possibly even more of them… 🙂
              My guess is though that it is ash.

            • Yeah, glaciers can do some pretty amazing contortions. It is nevertheless kind of intriguing.

            • Glaciers are very useful for their ice cores. In Antarctica(Where you cannot radiocarbon date) ash layers will usually give away the presence of an eruption.

            • As always the best is to have several sources for a dating, because ice-cores, dendrochronology, C14 and so on all need verification of the records, and only way to do that is to painstakingly start with “now” and work it’s way backwards. That work has been done for some areas of the world, but for from all. But you can improve the Antarctic Ice cores by calibrating them with known eruptions.

  7. Lost my beer… then I found it. I had misplaced it while putting pepperoni on my pizza. 15 minutes or so and I will be in pig heaven. I think I deserve the beer. Long distance run has been defered for parts, then I find out that they haven’t even ordered parts and want to verify the symptoms…. odds are I’m gonna wind up driving there just to say “yep, it’s broke.” Meanwhile, one of TPTB of the US government seems to think that her problems will all be solved by 31 November because she is in charge of that department and what she says goes.. no “ifs”, “ands” or “buts.” Friking moron.

    If karma is on my side, the old subduction zone for the Atlantic Seaboard will have an event and cause widespread liquefaction and building sinkage… preferably with a few of those rockheads present to experience the structural collapse. Yeah, I’m a total ass for wishing that upon them. I admit it. I’m the one person that you never want to have evil super-villan powers… I appreciate the attitude of the Veterinarian that was asked about a dog that killed the squirrel. “Squirrel probably had it coming…” (credit to tgmccoy I think for that one.)

  8. How about an article about lava types? (composition, viscosity, temperature, sources, etc.) My favorite is komatite.

    • Putting on my Dragon hat here…

      @Matt: If you do have some insight on various types, we would more than welcome it as an article. If a bit of trimming and pruning are needed, we can accommodate. We welcome informative articles. We are, after all, a collection of amateur enthusiasts that dabble in the subject of volcanoes.

      Okay, that was intended to officially invite a submission if you would like to write one up. 😀

      If you do take us up on the offer, please cite relevant sources. Some of us (me for example) love getting out hands on and digging through various papers.

      • I agree, an article on lava types would be swell. I understand that a guide of all lavas could be hard, but your favourites and so on would be a nice read 🙂

    • Hm… with a melt temperature of 1600 degrees it could only happen in a hotter than average mantleplume of very deep origin. And the only spot one of those could come from would be the core/mantle boundary.
      The only other source of Komatite is back from when the mantle was hotter in the archaean time 3.8 to 2.8 billion years ago.
      So… If I can find Komatite in either Norilsk or Kirunawaara ore field, then I have yet another partial proof for coreplumes. Sadly Norilsk is closed off for me, so if any geologist meanders past and have access to Norilsk and know about Komatites there, please tell me.

      • Are those somewhere where they can be easily found by new members? I think those two should be highlighted somehow.
        Alan passed by a couple of weeks ago quite literally riding a big honking steam locomotive 😉
        If we are nice enough to Fran she might use her geological skills to write something on the subject too… 🙂

      • I found them under Archive sorted by Author, so no; not that obvious… A place in the top menu for introductory articles is the way forward I think.

        • I totally agree with you.
          We should have a top-menu with that, preferably with a visible direct button, we should also move all the guides and stuff there so that people easily find them. We have a lot of goodies hidden that should be made readily available.

  9. Knock, knock!
    Who’s there?
    No one!

    No earthquake in Iceland for more than 12 hours. Sometimes it does happen. Eventually this will increase strain and some region will eventually see another swarm or magmatic intrusion, that we all can discuss happily here at VC.

    • Well, if your that bored…. Based on my simple calculations, Comet ISON will have enough solar energy hitting it at perigee that it could achieve a surface temperature of about 608°C. That’s down near the low end of where magma finally solidifies. It will probably be a bit less due to ablative cooling, but with a radiant energy flux from the sun of about 28 kW/m² it’s gonna be dicey.

      …. say, anyone have a paper that delineates what happens to frozen methane tossed into magma?

      Speaking of Iceland, I assume that those 3 or 4 quakes out in the dead zones yesterday were ghosts. They aren’t on the list anymore.

    • Irpsit: There where several quakes, but the weather was so bad that the automatic systems could not locate them even to a degree. I could though see them poking up above the storm noise.

      Lurking: I am not so sure about the Laki one. I sat for hours scratching my head over those. In the end I think that one of them was real. But the signal was “contorted”, my belief is that it was done due to the nature of the ground there. IMO, made the call that they where ghosts. If you use the standard model for the crust of Iceland out in the dead zone, then it was a quake, if you allow for zones of partial melts and a lot of fracturing, then I am probably correct. We will sooner or later see a lot of quakes like this unless IMO places a SIL or two out inside the dead zone. I would place it between Veidivötn and Laki.
      I am not a owner of a pet shop, a geneticist, nor am I a fabricator of fine knitted merkins.

  10. Just checked into Sakurajima as I do nightly prior to going to bed.

    It’s interesting how there is still intense fumarolic activity going on at Minimadake (the crater that was active prior to Showa, and slightly further up on the summit). I wonder if the intensity of the current activity will result in a reactivation of Minimadake. You can currently see two twin plumes emanating from near the summit, both mostly just steam.

      • Might be a few, but one should remember that Taiwan is a country with high building standards and that is used to earthquakes. So the houses are built to withstand them. So no large scale destruction or high mortality.

          • I don’t think so. There isn’t much information to work with to be fair. The only known volcanic area on mainland Taiwan is the Tatun Group, which hasn’t erupted in recent memory. If my memory serves me correctly, there was some information that came out around a year back that suggested that they wanted to research more into that volcanic group as there was some evidence that that volcanic group was rater similar to Pinatubo.

            • Last eruption was in 1775 to 1795. So there is actually quite a bit known about the volcanic activity there. Two active volcanoes, a couple of dormants, and 6 that might be dead.

          • Taiwan has a rather confused tectonic geometry. A stalled subduction zone on the west side, and an active one on the east side… with the 110-125 km depth contour under only a small part of the island…. that’s not conducive to lots of volcanoes forming due to a lack of an active magma feed system… or one that is pretty small.

            This sort of begs the question… is Taiwan a shard of crust that is rolling around in this confused interface… much like a pebble? It’s at the junction of two opposing subduction zones.

  11. I had an idea, to travel in March 2015 to see the total solar eclipse at Svalbard. Perhaps more people here would like to join there. That eclipse is going to occur in the Faroe Islands, but weather if often cloudy there. In southeast Iceland, the eclipse is up to 99% but not total. If I managed to travel there, it will be my second solar total eclipse of my life. And second also in Europe in recent decades.

    Good thing with this one, is that people could perhaps catch auroras during the day, besides polar halos, noctilucent lights, and coronal mass ejections because we will be roughly at solar max by then. Such exciting solar eclipse that will be,

    Astronomy-speaking, the next highlight will be comet ISON which could be very bright by early December this year. Something that could be 1 event of a lifetime. Then, an exciting comet passes extremely close by Mars in October 2014, and earlier in the spring there will be a potential strong meteor shower of a intersection between Earth and very near the orbit of a close passing comet, in late May 2014, another of those unique events.

    Add these to the coming solar max, and astronomers will surely be very happy in years ahead.

    • Solar Max is a cyclical event, and this particular one seems to be extremely lackluster in it’s intensity.

      But… the Carrington event occurred during a lull in activity, and there probably is am existing CME that will hit ISON soon. That should be interesting… provided that NASA gets off it’s dead arse and publishes photos and analysis of it when it happens.

    • Seing and feeling the total eclipse in France 1999 was unforgettable. But when I imagine that the cold darkness of the solar eclipse could be filled with aurora light… sensationel!

  12. Yeah… that’s gonna be fun.

    Note: This is a normal front rolling through. Nothing out of the ordinary. Just a pain in the arse to go out and drive around in it.

    • Crap, this bugger has spawned a tornado in Smith county. I have family there. (its’ also where I encountered a tornado up close and personal as it ripped half of the roof off the house several years ago)

  13. Hate to sound like a Yellowstone monger and this is probably a dumb question, but say like a 6.0 or 7.0 earthquake took place in the Yellowstone caldera, could it possibly open a crack that magma could escape through?

    • Normally you should not get one like these. I read on this blog that in a volcanic system the quakes cannot go over 5 or 5 something.

      • Among the heaviest I know about are the 6+ earthquakes that can happen at Ol’Donyo Lengai. But that is about maximum. Problem with Yellowstone is that it is also a rift zone with an active faultline. So it has suffered a M7.3, but that was purely tectonic.

    • Didn’t do bupkis last time it happened. But theoretically it could perhaps remobilize a little bit of magma. But, it seems like there is just not enough of liquid magma left down there.

      • Yepp, Yellowstone seems to be a champagne bottle that has been left open for too long. However you shake, it will not fizz.

  14. Hello and good evening all!
    The above discussion about which crater is steaming made me think of my old question of how hot it is in a volcano, generally. One like Sakurajima, that is constantly erupting must heat up the whole mountain considerably so that steam will be generated wherever any moisture is existant, be it from magma branching off deep down, precipitation, heated groundwater etc.. This steam has to come out; it comes up more easily than magma, and it will find the ways of least resistance, which in any case will be existing lava tubes and vents. Even if they are plugged up, steam will find cracks and probably end up coming out a crater.

    That was the “logical” explanation I gave myself when watching Etna erupting and seeing the other craters co-steaming happily in a paroxism of the NSE crater. Am I wrong here?

    Btw., that steaming above and behind the Showa crater has been there since I am watching, abt. two years. In other blogs I read that it comes from Miname-dake. It seemed quite normal to me that an erupting mountain should be steaming at all possible ends and corners – after my logic above 😉

    • One should remember that rock is terrific insulator, so something can be 1000C and a few tens of meters away it will be back to normal temperature.
      There is a reason we make insulation out of rock…

          • And that is mainly in rock (or sand, depending on size of them grain or chinks ) .. *Yup, therfore the smart… clause*

            • Six minerals types are defined by the United States Environmental Protection Agency as “asbestos” including those belonging to the serpentine class and those belonging to the amphibole class.

              [Serpentine Group Minerals] have their origins in metamorphic alterations of peridotite and pyroxene.

              And… California is rife with this metamorphic outcropping. Not all Serpentine outcroppings have asbestos, but it is the source material for it.

    • Thank you for your great explanations Granyia! The “white stuff” on the edge of the crater does not seem strange anymore. I’m convinced it is condensed water with very fine material (going downhill) and that the water evaporates and goes upwards again soon after that. Found the video below where the same thing can be seen (starting at about 26 seconds at the left side of the crater), only thousands times bigger than on the screenshots.
      Another question: Do we see the start of a small pyroclastic flow at about 5:46, in the middle of the picture?

      • Hi, My opinion this “white smoke” is not water vapour, merely dust from “shower of rocks” hitting the slope. You can see it forming where there is fallout from the first explosion at left. Many large rolling stones create trails whilst rolling down, see this a little later. Simply stones kicking up dust, dust that is also lofted up by updraft (kind of suction created by the Musroom cloud – basic thermal mechanics, intensely studied by my own eyes over many dacades…).

  15. Hey,

    I want to buy a seismometer. A cheap one, through the internet.
    I found this one, for about 290 dollars. Which is a fair price

    Would someone not recommend it? Or would recommend something else?

    I couldn’t find anything else on the web. What I want is something that could allow me to detect small earthquakes in Iceland, like Jon’s. Like up to M1 within a few kms around, M2 around the south of Iceland, or up to M3 in the entire Iceland, and of course a few of those megathrust quakes around the world.

  16. This is another funny gadjet that seems to work, to warn people a few seconds before an earthquake occurs. Since many costumers say it works, I might give it a try. Its also rather unexpensive and I live in a quite earthquake spot, eventually could event detect harmonic tremor in nearby volcanoes, who knows… I wonder what would be the threshold to detect a local quake here…

    • Well, the scientific principle is sound, but the item in question is not.
      To be able to do what they are stating you need somethiing far more sensitive and that is dug down into the ground. You would need your own personal SIL. On top of that you would need a fast computer and software that can separate P and S waves from each other to not get a lot of false positives.
      The one on Ebay would probably react to local 3s or 4s, and as such, it would locate the shear-waves, not the wave your after. So, you would be woken up now and then by false positives. And, if it detected one that is a biggie it would save you something like 0.1 to 2 seconds since you live right on top of the fracture zone.
      Seriously, I would spend the money on a bottle of Whiskey 🙂
      Or… get a set up like Jón has. He can probably get data accurate enough, still not in time to save anyone, but having it would give you really nice data to look at 🙂

  17. For Carl….

    Michio on Ice.

    From a NatGeo video about Einstein’s brain.

    Again… Michio dives into a field unrelated to his expertise. But.. in this case I think Kaku is dead on accurate since he echo’s Einstein’s own statements about what makes him so smart. To ask children’s questions and then follow them out logically until he gets an answer. Essentially, the power to concentrate so intensely on a topic.

    Note, the video quit working for me, so your success may vary.

    • Well, actually Einsteins brain and so on is much closer to his own subject. In a way it is the only way to get anywhere in Physics. And, if he had only done that with Yellowstone and asked childs questions and then followed the logical leads and facts where they carried him he would probably have gotten a better standing in here… Instead he was lazy and just burped a mental fart on Yellowstone.

      Edit: And I loved the him on ice 🙂

    • I think you will find almost every Icelandic volcano possible in here. Except of course Surtsey… Hm, how did we miss that one 🙂
      You can though starting to go through the about 100 articles on Icelandic volcanism in here. And if memory serves we had one on the Surtseyan eruption that happened around christmas in Jebel al Zubair. Also, quite a lot was written about it when Bob erupted.

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