The great eruption of Krakatau

Recently, I ran across a fascinating document about the potential damages from a New Madrid quake and had planned on doing an article about quakes… but since this is a Volcano oriented blog, I was quite pleased when Albert offered up this  piece on one of the more catastrophic eruptions in modern history.   I still remember spending hours reading about this eruption in the local library when I was much younger.  This is still the textbook example of “having a bad day.”

Guest Post by Albert:

It is one of the most famous volcanic eruptions in history. The loudest explosions ever recorded, dust spreading worldwide affecting sunsets for years, and it occured in a densely populated region, with many passing ships with captains adept at making scientific observations. It wreaked devastation. In spite of this, it was not a particularly large eruption. As a VE6, there were larger ones in the 19th century, and in the 20th century Pinatubo was possibly larger. But Krakatau is more famous than any of these eruptions.

The uninhabited island of Krakatau is (or rather, was) located in the Sunda Straits, between the large islands of Java and Sumatra. Even in 1883 this was a busy shipping lane, and the onset of the eruption was well observed. But the island was not seen as a threat. Apart a fairly minor volcanic eruption in the 17th century, there was little sign of active volcanism. The location is interesting, between the major island of Java and Sumatra. The main volcanoes in Indonesia lie along a line traced by these islands. Krakatau is at the place where this line makes a sharp bend.


Krakatau island was roughly 15 km2 in size, and had three, comparatively small, volcanoes. The tallest one was Rataka, on the southern end. The two lower cones were Danan and Perwoebatan. The word ‘Rakata’ means ‘crab’ in the old Javanese language, and this became ‘Krakatau’ in Dutch or Krakatao’ in Portugese (in English ‘Krakatoa is often used). This name became attached to the entire island. Two other islands, Verlaten island (‘deserted island’) and Long Island formed an arc, with Danan at the centre. Rataka also fell on this arc.

The arc around Danan was the remnant of a crater or caldera, 14km across, with Danan the central volcano. A large eruption would have been needed to form such a caldera. There are ancient stories about a massive eruption around AD 416 causing the opening of the Sunda straits but these seem mythological. A large eruption has been suggested to have occured in AD 535, to explain the decadal cooling at this time, but again there is a lack of evidence. Ash deposits in the Sunda straits indicate that no eruption larger than the 1883 one has taken place for many thousands of years. The caldera shows that a large event happened at some time, but it has not been in historical times.

 [ Krakatau Island, pre-eruption ]

Smaller eruptions did happen on Krakatau. An eruption took place from May 1680 to November 1681, probably from Perwoebatan, although one report states that activity occured at four different locations on the island. The eruption destroyed the forest on Krakatau. However, the eruption was not a large one. Afterwards the island remained quiet for 200 years. The forest regrew and became almost impenetrable. One landing party reported a hot spring, a reminder of the fire below. A lack of fresh water meant that, although people visited and occasionally settled, it did not become permanently inhabited. By 1880, no-one lived there.

In 1880, Krakatau came back to life. Frequent and strong earthquakes began to occur, one of which severely damaged a light house on Java. The first eruption occured on Sunday, May 20, 1883. Explosions were heard in Jakarta (named Batavia at the time), 150 kilometers away. Ash began to fall the next day, as far away as 500 kilometers. Over the next few days, ships in the area reported a column of ash, 11km high. The eruption continued, but not as violent as the inital eruption. On May 27th a landing noted that the explosive activity came from a 50-meter wide cavity within Perwoebatan, located within a 1km crater. Older lava flows suggested this was the same location as the 1680-81 eruption. A photograph of the eruption was taken, coloured in by an eye witness. This is the most famous picture of Krakatau.

 [ The May eruption ]

The eruption weakened over the next month, but on June 24th a second column was seen to rise from the centre of the island. By this time the summit of Perwoebatan had disappeared, presumed destroyed in the explosions. The two ash columns existed throughout July but the activity was not seen as exceptional — for Indonesia!

A landing party on Aug 11 found that large columns were now rising from three separate locations: Perwoebatan, Danan, and a site north of Danan, near the base of the cone. Lesser activity was seen at no fewer than 11 locations, all from the northern half of the original island, some only meters above sea level. This is the last detailed report prior to the great explosions. Over the next days ash fall was seen up to 80 kilometers away, with reports of loud explosions: the eruption probably intensified during this time.

The critical phase begain on the afternoon of Sunday, Aug 26, leading to a terrible night and morning.

to be continued

92 thoughts on “The great eruption of Krakatau

  1. Many thanks to Albert for bringing this beast back into the limelight!

    And before anyone gets on the 535 AD bandwagon, just remember to post your evidence (or a link to it) that shows actual dated geological evidence for it having happened. Though some people make the statement quite often, I have yet to see any reference to the actual data, so any link to it would be most appreciated.

    I’m not saying that it didn’t happen, but something that phenomenally large should have left some pretty glaring evidence other than a passing reference in a Kings list.

    • The AD535 bandwagon was set rolling by David Keys in his book ‘Catastrophe’. I can’t comment on his historical evidence, not my field of interest, but while he certainly proved that SOMETHING happened that year, quite possibly volcano-triggered cooling, his evidence for Krakatau is IMO pretty thin. Just for a start, he didn’t even mention, even to dismiss, any other volcanic candidates, and there were several – Rabaul, Ilopango, Alaska’s Churchill even. Or possibly an as-yet unknown and undated paroxysm from some volcano in the SW Pacific region


        Here’s Mike Baille on his comet theory – which he fully expounds in his book ‘Exodus to Arthur’. The dendrochronology seems to prove pretty conclusively that there was a sharp decline in tree growth over several years. What caused this is the problem – comet? volcano? several volcanoes? I have no idea, but whatever happened probably caused a great deal of death and misery across the world.

    • Pinatubo does have a magmatic feed system that could be just as prolific as Krakatoa. Generally, melt is believed to form at around the 110 to 125 km contour line of a subducting plate, but under Pinatubo (and the Philippine Mobile Belt) the plate hangs almost vertical down into the mantle. If ringwoodite undergoes dehydration melt at around 670 km, then there could be a second deeper source also feeding the systems there. As for Pinatubo 1991, the major difference may be the lack of seawater flooding of the freshly emptied chamber.

      • I remember reading an account of an Australian missionary who witnessed Krakatoa from the top of a relatively (about 40 Km ) close island mountain.
        one thing I recall was the major explosion/Tsunami that eliminated most of the foliage, structures and -people of that particular island..
        Yep, seawater probably contributed to the explosive eruption…

        • One video that I saw about it noted that there was a mixing of mafic and felsic magma. The felsic magma being quite sticky and gas rich was mobilized and lead to the destructive explosion. Yet another account mentioned that one of the vents was near the waterline and may have been submerged in the period leading up to the detonation. I have no idea which account is the most accurate, but flooding an emptied but still quite hot chamber would not make for a sedate event.

          • Mafic magma from deep below often reheats and remobilises felsic magma inside a magmachamber. That causes these large VEI5 or larger eruptions. Mafic magma triggering large felsic eruptions happened at Tambora and at Pinatubo.

          • Yes, and that was one of the fears about the reactivation of El Hierro. Even the restolingas (Bob’s floaters) showed the marked contrast in the two materials. (Trachyte/Rhyolite with mafic swirls.)

            I mention the possible flooding of a magma chamber only due to the rather dramatic destruction of the island in 1883. Many other systems undergo the magma remobilization scenario without the total destruction of the edifice. Mt St Helens being a possible exception, though the basal structure remained.

            The Trachyte vs Rhyolite issue of El Hierro remains unresolved and depends on which geological agency’s report you read. In all likelihood, the heavy silica content was caused by the underlying Jurassic era sediment layer that the magma had to pass through. It probably has the consistency of phyllite due to the pressure being to low to make schist. If that is the case, then the material is probably not magma that fractionated to Rhyolite.

    • Both are listed as VE6 although clearly for Krakatau this is not as well measured as for Pinatubo. So they are comparable. But in my opinion Pinatubo had a larger effect on global temperatures. This to me suggests a larger eruption.

      • great lead in, waiting for part II, just a minor typo “In spite of this, it was not a particularly eruption.” should probably say “In spite of this, it was not a particularly large eruption.”

  2. One of my favs/ waiting for “The Rest of The Story.” Best!motsfo ((ps/ for Lent, i’m giving up reading internet during the week.)) See You next Sunday.

    • You could always employ a program like Jaws to have the computer read the screen for you. One of the clients that the shop I used to work at had it set up on all of his PC’s. For a sighted person, it was a pain in the arse, but he could whip through programs with ease as long as his screen reader was up and running. {in fact, he was faster than I was at getting into some of his network settings, and I have full vision} My reason for being there was to troubleshoot his network. Network cards don’t give an audible indication as to their state… just LEDs.

      Note: Yes, I did throw a link to the software’s site. If anyone has a relative or acquaintance who is vision impaired, that link may help them find a solution. Uncorrected I am 20/400. I dread the day that I ever wind up sightless.

  3. Just to give you guys a bit of reference as to how loud Krakatoa was…. recently, Kelud, another Indonesian volcano, exploded, the sound from that blast was reported as being heard 200 kilometers away. Looking at the size of the dome, and comparing it to the size of the subsequent ash particles, then roughing the data through some milling formulas, showed that the energy expenditure somewhere in the size range of a Magnitude 6.2 earthquake.

    Based on the reports of how far away Krakatoa was heard, it had to have been a stupendous explosion.

    Wikipedia {Krakatoa}: “The explosion is considered to be the loudest sound ever heard in modern history, with reports of it being heard up to 3,000 miles (4,800 km) from its point of origin.

    … so, 24 times the distance of how far away Kelud was heard, and I believe sound looses energy as a square of the distance. (but I could be wrong). That likely puts Krakatoa at several orders of magnitude larger than Kelud’s comparatively anemic blast.

    Kelud’s dome before it detonated. It had already evaporated the lake by the time this photo was taken.

  4. And I have been banished from the living room.

    My wife didn’t like me heckling the movie “Volcano” on TV.

    I’ll give you a hint…. the magma (as depicted) would probably be mafic, and have a density of about 3000 to 3100 kg/m³. Concrete, the stuff that makes up the Jersey barriers that they use to direct the flow, has a density of about 2400 kg /m³. In other words, it would float on the magma quite well. Then you have the issue of spalling, which most concrete does when it is heated up to temperatures that high. Based on the “runniness” of it (as depicted) it would have to be quite hot, probably higher than that seen at Holuhraun. (which has had an actual river of magma, and we have all seen how it behaves).

    • I feel your ban is a little unfair, it is almost impossible not to heckle “Volcano”. The only thing that might stop you would be rolling on the floor laughing. Of course Hollywood tends to make a hash of all sorts of subjects.
      I am sure you have the same problem with movies involving ships.

  5. Good Morning all and thank you Albert. OH! I am on the edge of my seat here and I have to wait for the next episode!
    It must surely have been a terrifying event for those living in Indonesia.
    Water and Magma together is not a good mix. reading the accounts though it took some time before the Big Bang.
    Perwoebatan had disappeared or was that just the peak that had collapsed? There seem to be several vents and several explosions prior to the big one. Why didn’t it explode before? Had the sea not entered any of the vents? No Doubt all will be revealed in the next gripping instalment.
    Another thought. How lucky were those souls who made up a landing party? Not only were they able to witness (as we have done from the safety of our living rooms) a major geological event but they managed to time it right!.
    So thank you again Albert for greatly appreciatedr Post in a true Volcanocafe style 🙂

    @ Lurking. Back in the 1950’s I went to see “Journey to the centre of the earth” with a gentleman called Edwin J. Beer. He was a geologist and Chemist and was one of the inventors of Rayon. It was he who encouraged me in my interests in All things rocky. He died at the age of 107 . At 105 he took my children on a tour of his garden pointing out trees he had brought back from around the world. He remembered Rudyard Kipling too as he spent much time in India.
    Now imagine him watching that film 😀 Whenever I see re runs of it on TV I too laugh and comment. In fact I tend to comment on any “Volcano” film . I have announced to the family also that No way will I jump into acid water to save their lives. I may be a granny and lived my life, but I want to carry on living it & they are capable of saving themselves & their kids now (Ref. to Dante’s Peak) besides I would want to follow the eruption and see how it progresses.

    • Ah, Dante’s Peak. I was based in Cour d’alane Idaho when they filmed that
      movie . Notably they parked the UH-1 m(Huey) helo used in the filming waay too close to our DC-7 tanker. spent a lot of time keeping the hatches closed and avoiding rotor wash . We were glad to be sent to Billings, Mont. to keep out of the road…. Billings was our favorite “Briar Patch” that year..

    • May I recommend the film Krakatoa: East of Java to you all. Starting as it means to go on (Krakatau is west of Java) it is one of the funniest films I’ve ever seen. It has everything: rafts of pumice, tsunami, pearl fishing divers (scantily clad ladies), nuns rescuing a school full of orphans, convicts, hot air balloons etc. etc. etc. I cannot do justice to the story line – you have to see it for yourself. 😀

      • You are so much braver than I recommending that one Talla 😀 I didn’t dare 😀 😀
        If I had a fortune I would get the cast of Airplane to star in my film of “Journey to the centre of Dante’s Volcano South of The Iron” 😀

      • Well, there usually is a cult following for the really horrendous movies. Generally these fans are the ones who “get it” and know and revel in the discrepancies (both factually and theatrically) that are on blatant display.

        Yeah, you know who you are… ← Obligatory 4th wall break 😀

      • I have a theory that the Movie Moguls responsible for that epic knew perfectly well that Krakatau was west of Java, but changed it for box-office purposes (you know, the romance of the Mystic Orient and all that)

    • Good old disaster movies. I have quite a collection on them and nothing eases the mind more than a good B movie.

      Volcano is not even that bad. Sure the eruption may be laughable from a knowledgeable position and the poor volcanologist would probably be rapidly fired. But at least it somewhat stays in the realm of realism by doing what people expect of a volcano..
      Unlike some of the volcanoes conjured up by groups like Asylum. Which has people igniting into flames due to the heat being emitted by the eruption far away or the ground getting to hot. Or ice storms forcing people to flee towards the volcano to stay warm.

      Qua realism, the winner would probably be one of those “docu”movies. Such as Last days of pompeij. As long you ignore its a documentary.

      As for crazy stories about Krakatoa. I always liked the Uncle Scrooge story “The Cowboy Captain Of The Cutty Sark”.

  6. Revisiting that comparison to Kelud and extracting the energy drop off from 200 to 4800 km using the Impact Effects Program, it appears that it’s a factor of 28 or so times less energy intensity for the additional travel distance. That would place Krakatoa’s detonation somewhere in the 3,589.22 TeraJoule range and about the same as a Mag 7.17 quake in energy release. (56.9 Megaton TNT equiv)

    GL Edit: corrected
    GL Edit: NOTE: This is a rough estimate.

    • Even though it’s a rough estimate, I think it’s pretty close. At least I followed a logical train of thought to come up with it. The greatest sources of error come from my initial estimate of the energy release of Kelud, and the energy drop off rate due to the additional distance that the sound traveled. My estimate on the sound comes from running two separate meteor impact scenarios and comparing the difference in the pressure wave from those fictional impacts. If the energy release doesn’t have a direct bearing on the intensity of the sound from it, then the whole idea is shot to hell and back. With what I have available, I think it’s a good estimate.

  7. Thank you – fascinating stuff. My grandfather (b.1883, a missionary for some of his life) knew someone who was out there when it happened and used to horrify us relating his predecessor’s tales. Sadly I can’t remember anything much, except a frisson of horror at the mere name, even just of the Sunda Straits.

    • I so much wish now I could talk to my grandfather. I have seriously thought about writing down my ruminations and storing them somewhere. Just thoughts when something happens and descriptions of happenings,
      I have had a wonderful day 🙂 My dearest husband has bought me a lovely DAB radio for the kitchen and tonight the Meat & Potato pie was created with Elgar’s Nimrod and the swedes and carrots mashed to Tchaikovsky’s swan lake :D. The Cheesecake was created to bach’s Fugue in D minor :D.
      Poppy will soon be a classical Lurcher as she howled to the overture to The Magic Flute 😀 😀

      • Genealogy is my serious hobby and finding the writings of any ancestor is like finding a diamond. I have a few writings that just made the hours of research well worth it and the insight gained was incredible.

        I would highly encourage you to do this!

        • I agree. I’m into genealogy too. A couple of my children are interested also because of my searching through the years. It’s so exciting to have information or a point of view from someone who is family from long ago. 🙂

      • I use to listen to my great grandmother tell me about things long ago. She told me about the sinking of the Titanic. She wasn’t on it, but remembered how horrible it was. She knew a lady that saw 2 of her children die in their backyard during the San Francisco earthquake in 1906. The great depression here in the US. When someone would visit her she’d always ask if you wanted something to eat, because of it. She said she hated to see someone go hungry. She was a good cook too. Those are only some of the things. I’m sure if you do write things down there will be someone who appreciates it. 🙂

        Eddie, my little Jack Russell, sounds like he tries to sing when I play certain songs on the piano. 🙂

  8. I have been unable to visit for a long period, but when I returned this place seems dead. Where is everybody? There’s a lot of non-volcanic chatter by a few regulars, but the interesting volcanic discussions and debates by the usual others seems to have evaporated. Did I miss something in the last 6 weeks? Should I to go back and read the missed discussions and events?

    • The blog has always been discussion driven. What do you wish to bring to the fray? Radial dikes traveling along fissures and transitioning into a regional fissure system? Theoretical energy yield of an eruption? My calculation for Krakatoa pieced together a couple of different lines of evidence from unrelated fields, and hasn’t really been vetted as to it’s merits. I’m open to kicking that around.

      The whole region is subject to about 18mm a year expansion, and the eruption seems to have been triggered by that. We haven’t seen anything down along the “dead zone,” and it only stands to reason that it should see some effect from the northern leg having opened up. You don’t happen to know if there was any activity in the Holuhraun area prior to the Laki event of 1783 do you? That could be an indicator if there was. Volcanoes tend to behave in similar fashions to previous activity.

      • Whoa! I guess I did miss something and touched on a sensitive issue. I was just wondering where the diversity of opinions and people went. I was not aware there was a fray. I have enjoyed reading this blog immensely, even before Holuhraun, and noticed a change when I returned from a lengthy field experiment. My background is physics and I grew up in California where I experienced many earthquakes. Since being a kid I enjoyed hiking and tracing the seismic “footprints” earthquakes left behind all over the state. Then doing so elsewhere in the world as my profession allowed me to travel. Volcanoes are a much more recent addition to my interests. The only in-depth thing I have done related to volcanoes was researching the history of Ascension Island’s volcanic history. I have felt unqualified to openly comment or participate in this blog. I have been simply covertly and passively participating in “sponge mode”, aka “learning”. I publish papers in my own fields of expertise, but don’t waste others time by trying to engage in areas I don’t feel qualified. I have enjoyed your passion and knowledge and find it unfortunate that I somehow have provoked your ire. I apologize and withdraw my questions and observations.

        • No real nerve to be hit. And a lack of “official” knowledge in the area is not a requisite to be here on the blog. If we can’t give an answer, we can give an idea. And… questions asked here could very well enlighten someone else who was just too shy to ask. In that respect, this blog is a store-house of knowledge with easily accessible people from many different disciplines.

          The overall cant of my response was to elicit discussion. My estimates from earlier have not been scrutinized for their merit. They could be totally off mark, so, they are valid topics. My use of an r2 loss is based off of my experience in RF electronics. Acoustic waves may have a different power loss scheme altogether.

          • Careful, you had it right the first time. Don’t mix power and energy interchangeably. You said ” I believe sound looses energy as a square of the distance. (but I could be wrong)”. You are correct because you said “loses energy”. 1/r squared is correct for energy. If you had said “sound loses pressure at 1/r squared”, you would have been incorrect. Pressure is a field quantity (power) that must be squared to equate to the intensity or energy quantity. So the sound pressure decreases by 1/r. This usually messes people up as it seems counter intuitive that with a doubling of distance from the source, the sound pressure is reduced by 50%, but the energy (intensity) is only reduced by 25%. Now, does the ear measure power or intensity? The clue is the ear is a logarithmic sensor and the sound sensitivity of the ear is expressed in the Decibels scale.

          • That’s what I’m talking about! (not the subject, but the discussion)

            I was quite aware that my energy loss vs range could be erroneous so I used whatever had been built into the Impact Effects Program to come up with what I think is a more reasonable way of calculating the drop off.

            Using the Impact effects program, I came up with 2720 Pa of peak overpressure at 200 km for a 300 foot rock impacting at 45 km/s (arbitrarily chosen just to make a bang). For the same rock, at 4800 km, that’s down to a Peak Overpressure of 95.3 Pa. About 28.54 times smaller than the 200 km pressure peak.

            I think my greatest assumption (and potentially the source of the most error) is in trying to equate that to an energy release 28.54 times as great as Kelud.

            Using the milling formula method that I did when Kelud exploded, I came up with about 1.26E+14
            Joules. 28.54 times that yields 3.59604E+15 Joules.


            • At those distances, I presume curvature of the earth is a big consideration. Any sound reaching hundreds of km has to be an echo off of a physical discontinuity. Don’t know much about sound, but i presume it gets pretty complicated if the discontinuity is gradual, like the atmosphere layers. I would expect the level of sound to be very unpredictable at long distances, sometimes eerily so. Like unknown-source sonic booms. Think antenna beam side-lobes?

            • A more concise treatment would have to take that into consideration. You have made a very valid observation. Anomalous propagation can be a real bear to deal with, even at radar frequencies. I think the longest ducting that I personally have observed was the intercept of a surface to air missile site at a range of about 400 nm. The longest that I have heard stories of was of a surface search radar/nav radar at 1000+ nm.

            • Ideally, the pressure loss at 4,800km should be 24 times less, but the impact effects program likely also includes losses due to refraction and diffraction so the 28.54 times smaller value is a much more accurate number. Pressure (Pa) reflects work per unit area not energy. One Pa = 1Newton/meter squared. One Joule (energy) = 1 Newton * meter So, by unit analysis, you need to multiply your pressure in Pa by a volume (cubic meters) in order to convert the value into energy. Previously we had determined that pressure falls as 1/r while energy falls at 1/r squared. What volume do we use to convert from Pa to J? So the problem becomes a bit more complicated. The range is actually the arc determined by moving 4,800 km along the curved surface of the earth and some altitude that defines the acoustic height of the atmosphere. But the sound bends and reflects as it moves through the atmosphere as well which could reduce the losses below a simple 1/ r squared + other nonlinear and not insignificant atmospheric effects that could enhance sound transmission. All of this makes my brain hurt so let’s just pick a simple and easy 1 cubic meter “test cell” at any range and your 28.54 will suffice with some real world losses.

              Atmospheric physics will dictate how the sound will propagate. If there was a heavy cloud cover or a strong inversion over the region when it erupted, a lot of acoustic energy would be reflected back down and out horizontally, enhancing the sound heard at the surface. There will certainly be some reflection off the tropopause. If the eruption was preferentially in one direction, like Mt. St. Helens, the sound propagating in that direction will be enhanced. But assuming a generally hemispherical bang, refraction, reflection off inversions, and ducting will prevail as propagation enhancing mechanisms. An good question is: What was the weather locally and synoptically when it went bang?

              An interesting example of sound and the atmosphere: The bombing done by the Marines and Air Force at the bombing range in Yuma AZ would at times rattle windows in Tucson Az 220 miles away because of “ducting”. Bombs used were Mk82 500lb bombs that are rather small boom-wise. The window rattling was caused by the sound waves being reflected off atmospheric boundaries and tunneling between temperature inversions in the atmosphere that allowed the sound to propagate without normal losses before reflecting back to the ground. Such ducting is very common over the ocean and a similar situation exists below the oceans and is exploited by submarines trying to avoid sonar. I recall reading that such ducting can increase the delivered energy at extended ranges by two orders of magnitude (100x). I’m not saying there is amplification going on, but rather a reduction of loss by a factor of 100. It would be reasonable to assume that ducting of the Krakatau sound could have preserved the intensity significantly before it reached land. Maybe by a factor 10x greater than would otherwise be expected. Since the explosion is supersonic in nature as well, pseudo solid surface reflection off the ocean surface and a maritime cloud layer will also preserve the pressure wave front much further than an initial subsonic pressure wave. In some of the declassified Pacific nuclear tests you can see this pressure front propagating with little attenuation.

              I am not familiar enough with your milling formula to comment on it. But I will point out that a one megaton nuclear detonation has about 4.2 E+15 joules released. That indicates to me that you may just have enough energy in your results to obtain the observed results 4,800km away if the overwater enhancements I mention come into play. You are in the right ballpark as some of those mega bombs were allegedly heard thousands of kilometers away at select locations.

            • Well, “ballpark” was my goal, so I guess we are there. I’ve used formulas based off of Pappus’s centroid theorem to work out the energy dissipation of ocean waves from a point source while battling the La Palma tsunami crowd. If we were to push this to a more analytical level, it might serve well in dealing with area of a unit wave-front. The problem, as noted, will come from dealing with refraction/reflection and trapping.

              One issue that came up during those nuclear tests, was the phenomena of the precursor wave to exceed the speed of sound. The answer came when they realized that the air in front of it had been radically heated, raising the speed of sound that the surge front was passing through.

              The really insane thing with nukes, is that the practical upper limit of a nuke is where the fireball exceeds the thickness of the atmosphere.

    • There has been a lot of interesting reading, I always go through the archives when I’ve been away for awhile, & so would recommend that to anyone.

    • Hi seismicstalker, your observation of this blog being very quiet is right… for two reasons. Firstly, it has always gone quiet here when nothing exciting volcanically happened in Iceland. Unless Carl was here to spark the attention with his interesting ideas/observations. As most of the readers here are Icelandophiles, with Barda declining and Carl seemingly having disappeared, there is not much Icelandic stuff to discuss in times like this.

      Secondly, at the end of last year, almost the entire crew of moderators, except for two or three, have left this blog. A group of eleven (of which I am one) have last week opened a new wordpress blog, Volcano Hotspot. We have a slightly different approach to moderating and running a blog, and the toppics will be more on worldwide volcanic events, infos on present eruptions etc. rather than mainly focussing on Iceland. It is no competition to Volcanocafe, my hope is that perhaps some time in the future the two blogs can work together.

      @Albert – this was a very refreshing read, thank you!

  9. GRF does actually look intefesting. Nothing tooo out of the ordinary, but there were a few quakes at Grims in the past few days, and a M2.7 today, not too far off.

  10. I should probably introduce myself. Have been reading this blog for about 6 months. My interests include Vesuvius (specifically Pliny the Younger’s account.) What prompted me to make this comment is that I have a signed edition of William Pène du Bois _21 balloons,_ which has an interesting “Account” of the Krakatoa event.

    • Welcome aboard. Any filler info that you run across or can provide is most welcome.

      The thing about Krakatoa that first caught my attention was about the ship that was pushed far inland and stranded. At the time I was simply amazed that something like that could happen… but following the Sunda trench quake and tsunami, and then the 2011 Tōhoku earthquake and tsunami, the idea isn’t quite as bizarre now. With Tōhoku, we got to see it live on TV.

        • I am not sure the book is well known outside the English speaking world. It is sort of a 1940s “Steampunk” book, lavishly illustrated, similar to the more modern “Hugo.” What makes this one fun is that it is based on real “science” of the 1890s. Although I doubt that there was a Utopian Society of millionaire inventors living on the island at the time. According to Wikipeda the book won major awards for children’s literature, so It should be available from the usual sources.
          The subject of “volcanos real and imagined in fiction” could be an interesting one. Until Modern times Pliny the Younger’s account was just that. The novel also fits in here as they had a Gourmet government. with the coat of arms a frying pan over the volcano. The motto on the illustration is Non Nova, Sed Nove.

    • Hello Julie

      When I read of other’s difficulty with not heckling the movie “Volcano” (is “to heckle” related to Hekla?) I thought of how impossible it was for me to not heckle “21 Balloons”. My father gave that book to me (not a signed edition) because he had fond memories of his mother reading out loud to the family after dinners.

      At the time I read it, I knew nothing about volcanoes or Krakatoa. What really irked me is how the residents of the island said that they had eliminated all work. But SOMEBODY had to do the cooking and run the laundry machines, dust and sweep, keep their clothes impeccably pressed, etc…. I guess I’m over sensitive to people who don’t notice the word “work” in the phrase “women’s work” (which of course by itself is a bad enough phrase.).

      But I’m glad you mentioned the book; it saved me from having to figure out how to do so 🙂

  11. And there is always the possibility that Grímsvötn could have a leaky spot where the Bárðarbunga dike entered it’s swarm and made a left turn…

    My interpretation is that the rock toward Grímsvötn was under a higher pressure and more resistant to cracking open. (greater hoop strength)

      • When I look at the way the fissure fields are laid out in Iceland it makes sense that rifting would create dikes that run parallel and generally in a north/south direction.

        But when you look at the dogleg in the MAR it almost makes the east/west region of the dogleg appear to be like a transform fault area, so dikes running east west should not really be too surprising, the way I see it.

        • It is very much like a transform fault. The MAR is prone to jumping back and forth by a few hundred kilometres. The same happened on Iceland.

  12. OT and poking around with biology since I know at least one of you are well versed in that area.

    I was talking about the Red Queen Hypothesis with my wife the other day, and made mention that evidence for a high speed North American predator exists in the fact that the western US still has an existing species of potential prey animal called the Pronghorn. From Wikipedia: “pronghorn is the fastest land mammal in the Western Hemisphere, being built for maximum predator evasion through running. The top speed is very hard to measure accurately and varies between individuals; it can run 35 mph for 4 mi (56 km/h for 6 km), 42 mph for 1 mi (67 km/h for 1.6 km), and 55 mph for 0.5 mi (88.5 km/h for .8 km). It is often cited as the second-fastest land animal, second only to the cheetah. It can, however, sustain high speeds longer than cheetahs.”

    In all likelihood, the Pronghorn developed this speed ability in response to the now extinct American Cheetah. Now it’s just a blisteringly fast land animal with nothing that can really chase it.

    Also from Wikipedia “Pronghorns are built for speed, not for jumping. Their ranges are sometimes affected by sheep ranchers’ fences. However, they can be seen going under fences, sometimes at high speed.

    As for the discussion, my wife just rolled her eyes and told me to go to bed. 😀

    • It would be interesting to look at the pronghorn in a few thousand years and see if it has actually slowed down. If there is no need to run fast then the energy used is not efficient and does not benefit the animal However I cannot see how reversion to slower speeds would happen unless slower is sexually more attractive.
      Since the prong horn is still fast and the prey now not so fast then that suggests that this trait will not reverse it will just remain stable as the species population growth may have reached equilibrium.

    • A fascinating bird is the kakapo. From NZ of course. A massive parrot, possibly the longest-lived bird species of all. Well-camouflaged, flightless, ground-dwelling, nocturnal. Freezes when alarmed.

      All good defences against its only predator; the enormous Haast’s eagle.

      Unfortunately no-one told the poor kakapo that the eagle went extinct a very long time ago indeed, and its defences are of little use against humans, cats, and stoats…

      Oh, and they’re also possibly the most sex-obsessed creatures on the planet…

    • Hi Rojo and welcome.
      Yes. I think this well documented eruption has captured the imagination and interest of thousands of Volcanoholics and future Volcanologists. No matter how we laugh and scoff at Hollywood’s track record on the subject of scientists and earth sciences, I do think the subject matter in these dramas may spark interest in youngsters for whom this is their first chance at experiencing Volcanic activity. Words in books really cannot compete for the sounds and visuals of an eruption.

      Which brings me to the subject of sound and ducting and submarines ducting and diving sonar. I wonder if sea mammals purposely use the relief of the sea bed/depth/ other differences in conduction of sound waves in communication?

      I love these discussions. I don’t quite grasp the maths or Laws but the content leads me to always to look further. The more people add or question, no matter how basic, the more can be gained from a blog such as this.
      Please don’t be shy in coming in to ask, suggest or ruminate on the seeds of ideas. 🙂

      I make no apology for my very frequent ruminations on Off Topics. The comments may not be volcano driven and but the fact I am “Chatting” on this blog and not in a general chat room bears witness to my deep interest in Earth Sciences and the links with life (Biology). As the recent Volcanic event in Iceland subsides (maybe only temporarily) the comments have also subsided. Other eruptions will and are happening around the world but often it is difficult to follow events closely and data is not freely accessible to amateurs.. This is where the posts and articles are so valuable. They give concise, accurate and informative accounts on a wide range of volcanic subject matter.
      When the next eruption happens that may affect people internationally, the footfall on this blog will immediately increase as dramatically as the lava flows and the ash ascends. 😀

  13. Keep going OT Diana. I like it and it keeps life interesting when it goes quiet on the volcano front. I’ve been a long time lurker but in view of the “split” will now try and add the odd comment.

  14. An FYI. The second installment of the article is present, but I have service call issues to deal with right now. It will be later today before I get it put in. Sorry for the delay.

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