The eruptive past of Indonesia

Merapi, 2010

Gunug Agung has had impressive eruptions in the past week. So far, in spite of the publicity, the event has remained relatively minor. We do not know whether these are the initial rumblings and in the next weeks and months there will be far larger explosions, or that this suffices to relieve the pressure inside and allows the volcano to go back to sleep. For the local population the second option would be preferable by far! If the eruption intensifies, we also do not know what level it may reach. Based on statistics, smaller eruptions are far more likely than big ones, and Agung is therefore expected to behave. On the other hand, larger eruptions do occur and can never be fully excluded. And if the size reaches VEI6 or higher, the impacts can become global. But even then, it is the local people who suffer most.

From Susan Loughlin, Sarah Brown, et al: Global volcanic hazards and risks, Cambridge University Press, 2015. Fatalities due volcanic eruptions. The red line is the full count, the blue line is without the 5 largest events and the purple line is without the 10 largest events.

The figure (taken from the book ‘Global volcanic hazards and risks) shows why large eruptions are best avoided. It shows documented fatalities due to volcanic eruptions over the past 400 years. Obviously, the older the event, the less complete the record will be. The numbers are dominated by the largest events, and the largest events are dominated by two eruptions, both in Indonesia. These are also the two largest eruptions in Indonesia in recent centuries. It seems likely that past VEI6 or 7 events in Indonesia will also have had massive local impacts. Worldwide, every known VEI6 or 7 eruption since 1600 has resulted in fatalities. And Indonesia is particularly vulnerable: it is a densely populated country, with a high level of development going back millennia, and there is a tendency for people to live close to the most active volcanoes as that is where the land is most fertile. Nowadays, the volcano observatories in many countries do a marvellous job in saving lives. Most eruptions give warnings, through a variety of precursors. In the current decade, the most devastating eruption was from Merapi (also Indonesia!) in 2010, where over 380 people died. But almost half a million people were evacuated before the eruptions, and it as been estimated that this evacuation saved over 10,000 lives. The Indonesian authorities, guided by the volcanologists, avoided a catastrophe.

The risk of eruptions depends not only on the particular volcano, but also on the nearby population. Taken both into account, Indonesia stands out as the country with by far the highest level of danger. It has been estimated that over 60% of the global threat to people from volcanoes comes from Indonesia. This is calculated from the number of active volcanoes, and the number of people living within 30 km of one. The second highest country, the Philippines, accounts for only 10%.

Since 1950, 347 volcanoes are known to have erupted across the world. Before 1950, the records become rather less complete. Over the holocene, 886 volcanoes have had known eruptions. But even for the largest eruptions there are major gaps in our knowledge. It has been estimated that we do not know 85% of the largest holocene eruptions from before 1AD. This makes it difficult to derive eruption rates, and makes it tricky to estimate the likelihood of a VEI6 or 7 per century. The best current estimate is that a VEI6 eruptions happens once every 70 years. The number of VEI7+ eruptions is estimated in the same manner to be once every 3000 years, but that seems an underestimate. After all, there have been several such eruptions over the past 2000 years. And two of the largest three eruptions of the past millennium happened in Indonesia.

Let’s take a quick look at the major eruptions we know about in Indonesia. This is a whirlwind tour, and is very very far from complete. In fact, only a few biggies are listed.

1883 Krakatoa VEI6

Anak Krakatau in stormy weather. Source: Marco Fuller

This most famous of eruptions is also the smallest one considered here. The eruption volume was perhaps 20 km3, and it counts only as a VEI6. The death toll was still horrendous, because of the tsunamis which destroyed the nearby coasts. The pyroclastics flows added to the toll. The volcano has been busily rebuilding itself albeit not at exactly the same place. Anak Krakatau is trying to emulate its famous parent.

1815 Tambora VEI7

Tambora, in 1815, was the most recent major eruption the world has experienced. The volcano is located on Sumbawa island, east of Lombok. The explosion had worldwide impacts, including the ‘year without summer’. The eruption volume was in excess of 100 km3; it left a caldera 7 kilometer across. Before the eruption, the mountain was one of the tallest in Indonesia, estimated at 4300 meter. Afterwards, it had been reduced to less than 3000 meters.

1257 Rinjani VEI7

This mountain on Lombok is the location of the disastrous 1257 eruption. There used to be a mountain here, Samalas, but it disappeared in this explosion leaving a caldera of 7 km diameter. It is claimed to be the largest explosion of the last 2000 years. 25 km away, the pyroclastic deposits are still over 30 meter thick. The volume is not well known but it likely to be around or close to 100 km3. The eruption had worldwide effects, including dry fogs in Europe, and the death of 20,000 people in distant London, caused by crop failures and famine. It may have been to blame for the decline of the Mongol empire. And in Indonesia, it destroyed a kingdom.

29,300 BP Batur VEI7

Batur caldera, hiding behind brooding Agung

Behind Agung, on Bali, lies a much less imposing mountain. And behind this mountain hides an elliptical caldera measuring 14 by 10 km in size. This is the site of another monstrous eruption. The ejecta, called the “Ubud Ignimbrite” covers an area of about 1200 km2. A later eruption, about 20,000 years ago, was four times smaller, and formed the current lake. Both large eruptions were dacitic. The Ubud ignmbrite, which comes from the earlier, larger eruption, has a volume of 84 km3. The full ejecta must have been more. Over time, a new dome has formed in the centre: it still erupts regularly.

33,600 BP Ranau VEI7+

This is another remnant of a very large eruption. Ranau is a 14 km by 8km caldera, rectangular in shape, which is filled by Ranau lake. The caldera formed in an eruption that left its ejecta over a region at least 100 km long. The tuff in one area 50 km from Ranau is still several meters thick! Seminung Volcano has now grown up in the caldera, and is perhaps the reason why the remainder is rectangular. Prior, the caldera could have been as large as (perhaps) 20 by 20 km. However, it is also possible the caldera has been distorted over time by movement along the Sumatran fault and was a bit smaller than that. The eruption was rhyolitic. The total volume is not well known, but is certainly in excess of 100 km3 – possibly by a lot.

Source: Danny Hilman Natawidjaja et al, 2017, Geoscience Letters, 4:21

52,000 BP Maninjau VEI7+

This beautiful lake is located in the Padang Highlands, Sumatra, about 300 km to the south of Toba. The lake is 16 km by 7 km, and has a volume of 100 km3. The caldera is bit larger, 20 km by 8 km. There have been two eruptions here, where the first one formed the main caldera, and the second a few thousand years later enlarged the southern part of the caldera. The first eruption is the major one: it left its deposits over an area of 8500 km². The eruption produced a volume of 220–250 km³.

The caldera formed over a fairly short period of time. There were a series of closely spaced pyroclastic flows and surge deposits, followed by three high volume lava flows going both east and west.

Carbonised palm trees (10 to 15 m high and c. 0.3 m diameter) on the upper eastern flanks of Maninjau caldera. From Alloway et al. / Earth and Planetary Science Letters 227 (2004) 121–133

74,000 BP Toba VEI8

It is too large to comprehend. The lake is 100 by 30 km in size, with a surface area of 1100 km2. The volume of water is a staggering 240 km3 which makes it larger than the Dead Sea. The eruption that caused this lake was equally staggering, the largest known on Earth in the last 2 million years. The volcano that was responsible had had several big eruptions before, but the final one blew everything away. It erupted 2800 km3 although much of this was not explosive. The lava flows reached both oceans! The flows and ejecta cover an area of more than 20,000 km2 with a typical thickness of 50 meter. The explosive phase, producing ash, lasted around one week and produced 800 km3. That is 100 km3 per day! The effusive phase may have lasted longer. It is hard to believe that anything in this part of Indonesia was left alive.

Eruptions like Toba are very rare, and they may only occur once per million year or longer. It is perhaps a midway point between a major eruption and a flood basalt. No worries.


Huge eruptions, of the size of Maninjau or similar, seem to happen here perhaps every 20 thousand years in Indonesia. The ones we know about are all on Sumatra: that island seems particularly prone to caldera formation. Smaller eruptions, say the common-garden VEI7 variety, happen here as often as once every 500 to 1000 years. They tend to occur further east, towards Lombok. VEI6’s, like Krakatoa, can probably occur anywhere and anytime. They happen in Indonesia once every few hundred years at least and perhaps more often.

The lakes left by the largest caldera forming eruptions can last a very long time. These eruptions destroy the magma chambers that feed them and no new volcano will form: there may be rebound which fills in the central part of the caldera, but this is not volcanic in itself and new volcanoes will more likely form further along. The longevity means that we may know most of these calderas. No other Toba-sized eruption has happened on Sumatra over the past million years: we would have known.

But smaller eruptions, say Tambora-sized, appear not to leave lasting scars, or we would see them everywhere. The magma chambers survive these blasts, and over time a new volcano grows and fill the caldera. This may happen within a few thousand years. The new mountain may not erupt as massively as its progenitor: there is no guarantee that VEI7’s put in repeat performance. But in Indonesia, anything is possible.

Albert, Nov 2017

Source: Danny Hilman Natawidjaja et al, 2017, Geoscience Letters, 4:21

202 thoughts on “The eruptive past of Indonesia

  1. The somewhat unfortunate thing is that there are so many more calderas that undoubtedly are the product of past enormous eruptions. A caldera like the Ijen Caldera is absolutely enormous, yet we know very very little about its history. It’s almost as if there are just too many volcanoes here to study that extensively.

    • You are right, that one should have been mentioned. It is a complete mess with new volcanoes everywhere, and the age for the caldera (50 kyr) is actually an upper limit: it could be older. One for a future post! Are you planning anything on it?

      • Great post as always, thought provoking But on Ijen, one very minor detail: one of the small surrounding cones is called Gunung Merapi i e ‘Fire Mountain’ There are no known historic eruptions AFAIK, but I would suggest the possibility that its name indicates activity since the establishment of a human civilisation in Java

      • I would have loved to write more about some of the Indonesian volcanoes, but have been very busy recently. Also, there just isn’t a ton of information on a lot of these, at least in english.

        There are plenty of other caldera systems that are roughly 100 square km or larger in Indonesia that I can’t find much information on…

        Danau Caldera…

        These are just calderas on Java. There are many more elsewhere across Indonesia, many of which may be buried or very hard to see because of erosion.

  2. Great background info to have in mind when we follow Agung. And as allways,. Nicely presented story!

  3. I am as always a friend of Sulawesi and the other brute giant of Indonesia, Tondano.
    Yes, it is a 2.5 million year old supervolcano. I just wanted to point out that not all of them are located at the usual spot.
    In the caldera we have a nested caldera called Pangalombian that erupted around 150km3 27 000 years ago. There have also been a small bunch of VEI-6 calderas, but they have rapidly infilled and are almost visible. It is by far the most active volcanic centre of Indonesia.
    It is though currently enough vented to stay away from anything larger than a VEI-4 or two (at the same time).

    And in regards of the WordPress problem.
    There is now a new one. I am getting booted out every minute and have to log in again… Time to roll back to an earlier version and stop updating so we do not get this kind of crap in the future.

  4. 3.1 quake at Agung. Anyway you can easily picture a future Agung caldera in the picture with Batur in the background!

    • There will be one. One day. That how it goes for stratovolcanoes.

      Meanwhile, Batur will have grown back to its former glory, new home for the Hindu god.

      And Anak Krakatau….well, it won’t be Anak anymore, but a new Perbuatan about to blow itself again to smithereens.

      And yet again,in a heck-of-a-lot of thousand years, Agung will be back, Batur will have again ran amok and be a hole in the ground…. And neighbor Rinjani will be fully rebuilt to its 4000+m pre-eruption, ready for quite a show….

      As soon as there is active subduction, things will go on. And on. And on…

  5. Either an intrepid soul is burning rubbish on Agung’s slope or she has [new] fumaroles.

  6. Important: can all Edge users who had the ‘invalid’ issue please try again?

    Can you also check to see if you get constantly logged out, please?

    • No logging problems for me! I’ll try and create and Invalid Token. Story of my life, really… Clive: the Invalid Token.

    • I am not Carl

      I may appear to be Carl, but this is another Admin logged into his account to test MS Edge and trying desperately not to cause mischief!!

      Hopefully this works

    • It as trembled for prolonged periods before, but this looks really violent.
      There seems to be some kind of storm moving in, so I have no clue as to the cause, Could be wind, could be tremore, could be a clog dancing team on the gantry.

    • It was trembling almost all day yesterday, just as today. I’m 95% sure it’s wind. Also fits the bad weather.

  7. I don’t like Edge.

    I don’t like Firefox either.

    I am not enamored with Chrome but that is what I use because it has an entertaining Gargle Translate function. Thank you Carl for the Gargle term.

    Now lets see if this works when I post it.

    • It hasn’t booted me out and my comment came through fine.

      Microsoft Edge 40.15063.674.0
      Microsoft EdgeHTML 15.15063

      • I should add

        Micro$oft Windoze 10

        Version 1703
        OS Build 15063.726

        • I forgot. Chrome logs me in automatically but I had never logged into Volcanocafe in Edge.

          I am logged in here now in Edge. Lets see if this works.

  8. Interesting – it was reported that this happened in the Bali Tribune, then later they edited the article with other comments refuting that there was evidence of ejecta.

    Some comment in the thread suggesting “cover up” “for tourism”.

    • Hmmm… Difficult to strike a balance between proper prevention and making everybody chicken-out and flee the area needlessly….. So much economic interest at stake….

      Kudos to the awesome team at VSI, not to have bowed to pressure and having kept Agung at level 3 and evacuation still in effect. I’m sure they were pressured to death to dial back down the emergency level to green and give the all clear. Had they done so, there would be people on the slopes, getting pummelled by pumice stones and whatever…. Not to forget that lava now could start to flow at anytime, or the eruption may start producing nuees ardentes….

      Keep that guy under a tight watch.

    • 4 km? Meh. Hekla can out-do that with ease. If I remember Carl correctly, Hekla holds the record for the furthest projectile based death from a volcano.

  9. There’s been another episode of volcanic tremor – the seismo chart has been off-line for a few hours, now it’s back on line and showing only the tailing-off of the latest episode. I guess the shake shown at about 20:18 local time was the M3.1 shake in the news.
    Posting this as hosted image, as connection to magma website is still flaky.

  10. I see my session from when I logged in the other day expired. I recently was ugraded to firefox 57. Never did figure a way to change the avatar.

    The Pemantauan Aktivitas Gunung Agung Bali what I call to myself the “Temple view” seems to not be streaming. Mostly seems to be cloudy that way. The insects/rain at night can be entertaining.

    There has been a lot of interesting Pareidolia, On the “Camera1 CCTV” view, a rather nice Aladin’s lamp this morning. I can see why the old ones thought that they were seeing gods and daemons rising through the ash. A veritable pandora’s box. One has to believe that some of this that comes out is also hope… (Which I think was seen as looking like a butterfly.)

  11. Very surprising, these burst of tremor…. Seems like “stop and go” magma feeding from depth….

    My (non expert) opinion, is that everytime a bout of tremor like this occurs, some lava wells up in the crater, higher and higher…. Might be about to spill over…. Interesting developments to expect…

    Meanwhile, to all the doom-sayers and (especially UK) trash-newspaper who are forecasting an ice age and volcanic Armageddon, please please PLEASE keep your ramblings and ravings to yourself. You’re doing a huge disfavor to accurate science and public education/information by acting like this. Please keep your trash to you, or else it’ll end up being used for what it’s designed for, ie emergency butt-paper.

    There is NO REASON Agung will go VEI7 on us. Probability in our lifetime is so remote it’s nonexistent. It may very well make it to a VEI4+, maybe even VEI5. That’s in its competence, has done before, will do again… but will it do it this time?

    Sorry for the harsh and heartfelt language for those paper-scribblers errr…no I can’t apologize for such a thing, that’s disinformation on a criminal scale. That’s a sin. They should be force-fed their sh..tuff down their throat for all eternity.

    • Trouble is Alcide Cloridrix, these ‘news reporters’ probably haven’t even the slightest idea what a VEI is, let alone be able to understand it! These scare stories sell papers – all they are interested in. Egged-on by their editors, the more macabre they can make them the more satisfactory the end result as far as they are concerned. ‘Facts and truth’ are ignored as immaterial and irrelevant. They are all scum.

      • I´m one of the reporters covering this story. I can assure you that all other reporters I know are trying their utmost to cover it accurately.The problem is, as always, that we have to cover something that we know not enough about. This week we write about volcanoes. It might be the only time during our careers that we cover this subject. We also have to do it fast. Typically we can use half a workday for a story. Some larger media operations have staff members that can cover a more narrow field. Like science and technology. They might cover all the big volcano stories. I have been fortunate enough to ble able to cover one other big volcano story: Eyjafjallajokull in 2010. That experience gives me the possibility to understand a little bit more about this current story. One of my stories was used by ADAV in another discussion thread two days ago on this forum. I find it interesting that people that are refered to as scum, is also used as credible sources. I have learned a lot by reading post on this forum, and i thank you alle for your effort.

        all new members get held by the spam bot for processing until manually added, any new posts should work fine now.

        • You are most welcome here. People get upset by the kind of news stories found in the Daily Express and such, which predicts armageddon about twice a week. But we enjoy the more typical news stories, with interesting facts and human stories, written by journalists who take the time to talk to the right experts. Half a day is about how long it takes to write a post here, if it is on something we know about (posts on something which requires research can take considerably longer!). And still, the VC readers chip in with lots of corrections and additions.

        • Hi Hallvard. You have my sympathy and I hope that the country/publications you write for do show a level of integrity. Unfortunately, some of the mainstream tabloids in the uk are entirely lacking in this respect and are repeat offenders that wilfully misrepresent scientific based stories to achieve lurid headlines and presumably sales. The publication that Albert mentions has a long track record for outlandish meteorological stories, by the same journo, for a number of years now. If you understand the field then such stories can be readily dismissed, but for the less informed readership, these stories may have an impact on their lives if they take them at face value.

          • I should add – i’m being generous in attributing the motive of tabloids to misrepresent science as sales driven. It would be fair to say that one could take the view that this misrepresentation, in some UK publications, may be driven by more than simple sales figures.

        • I actually find this refreshing. The actual fact of a reporter looking into the topic lessens my disdain for them. I just hope that you keep in mind that we, as a whole, are not experts in this field. We’re well read on the topic, and try to stay as up to date on it as we can… we also have a few pHDs and other experts lurking here to smack us on the head if our musings get too far “out there”. But feel free to ask any question about volcanoes you wish. We will try to give you the most informed answer we can. Failing that, we can usually point you at a good source for the answer. Along those lines, my opinion is that Agung will not have a catastrophic event unless it suffers a large scale caldera collapse. A good source for the mechanics involved, is “Caldera formation by magma withdrawal from a reservoir beneath a volcanic edifice” Pinel, Jaupart (2005) → Earth and Planetary Science Letters 230 (2005) 273– 287

          And no, I am not an expert. I also did not stay at a Holiday Inn Express last night.

  12. It appears the Edge issue is mostly resolved with the exception of Carl it appears.

    Anyone else still getting “invalid security token”?

    • Tried on my main Windows 10 machine: everything works OK, from Edge, Firefox and Chrome.
      Tried on my little Ubuntu machine (which should be the one giving problems, due to Linux compatibility issues and whatnot): everything works OK in Chrome and Firefox.

      I’m afraid Carl’s problem is not caused by the website, but by something interfering on his own computer, messed-up security settings, half-done windows updates, or a badly designed extension causing conflict. Hopefully there is no toolbar/adware/browser hijacker he’s not aware of which is causing trouble.

  13. So I was traveling from Bali to Gili Trawangan (on Lombok, approx. 50 km away from the crater) the day before yesterday and was able to see Agung with my own eyes… it really is an impressive and at the same time scary view… Here are two photos I took (and I hope I am putting the image links in correctly):

    (This was the morning view from a speedboat passing Agung)

    (Sunset view from the western side of Gili Trawangan)

    The wind direction has shifted yesterday (Bali airport opened in the afternoon), and in the evening, it was very windy (maybe because of the cyclones building up south of Java). Today it looks overcast and according to the forecast, ash might get blown in our direction…

    Everybody here is watching the volcano closely, but so far people on the Gili Islands have only been affected by flight cancellations and low tourist numbers. I myself have a flight out of Lombok on December 10…

    • Wonderfull and keep us posted… it’s so helpful to have eyes on spot….. Best! and enjoy the rest of Your vacation..

    • Thank you so much, it really is an incredible sight, although I feel sorry for all the refugees on Bali who had to leave their homes. Of course people here also think about what could happen in the worst case. At the moment, the biggest issue is the cancellation of flights.

      On the humorous side, there is a new game here now, “Thunder or Agung?” 😉 , but I guess we’re too far to hear anything from the eruption.

      I will definitely keep reporting from here what I can contribute and what might be relevant, but I’m not an expert and Agung is not always visible… 🙂

    • cyclone is on my weather charts, it will hang around a couple of days and then move of the coast of Australia and south out of harms way

  14. Chugging along.

    Remember, this plot has a lot of room for error. Darwins ash reports are intended for safety of flight, not accuracy of plume height unless it has a specific threat for air travel. In my opinion, this would tend to make them over report height for the sake of safety. What the official DRE (and VEI level) ultimately is depends on the scientists who go out and do the hard work of actually measuring things afterwards. What it boils down to, is that my plot and method is just a semi-educated guess.

    Side note. The actual volume of airfall tephra is going to be about a factor of 4 or so higher than my number. (unconsolidated and uncompressed material.) The actual density depends on just how frothy and energetic the ash was when it was generated.

    • IF Agung continues along it’s average emission rate, VEI-4 might be achievable by the end of the year. If it holds to the lower rate, it will be well into next year before it gets anywhere near that. If it goes freakazoid, well, then it’s a guess. But the reporters will be happy. (They thrive on misery and death)

      • I’ve got this song but hadn’t listened to it for a while. He’s definitely got it right about majority of them. 🙂

    • Oh.. and by the way. In order for a Volcano to be able to adversely affect the climate and do that much vaunted “Volcanic Winter” that the reporters and doomers love to kick about… Agung has barely put an ash cloud halfway to the tropopause. Failing that, there will be no aerosol screening forming in the Junge layer from Agung’s sulfur load. Until Agung can loft it’s plume to the stratosphere, expect minimal effects. Face it, despite how scary it may seem, or the reporters wish… this is a mediocre eruption as far as volcanoes go. Bejing’s daily sulfur emission probably has a greater chance of getting to the stratosphere throgh diffusion than Agungs sulfur load. (stratosphere is lower near Bejing than at Agung, and both are emitting into the troposphere.)

      Troposphere = Weather = lots of H2O, meaning SO2 turns to sulfate and precipitates out before it gets high enough to have an effect.

      I don’t remember the title or author, but there is a paper out there that I ran across that explored the mitigating factor of H2O in relation to low latitude eruptions vs high latitude eruptions. In short, tropical volcanoes have to work harder and faster to have the same effect as high latitude volcanoes. (Meaning that Kamchatkan, Alaskan, and Icelandic volcanoes have much easier access to the stratosphere)

      • Thanks for explaining this. A cyclon is nearing Agung. How will strong winds affect plume height and estimation of emission?

      • With the winds there it has been keeping the plume from getting higher. I’ve only seen it verticle a few times. Most of the time it has been blown to the left on the CCTV Gunung Agung. By the way which direction is that?

        • The one I am watching now is blowing it to the right on the Site Bukit Asah, CCTV Gunung Agung. And now I must hit the hay or go to bed.

  15. Now, white cloud above the Agung remind me Holuhraun eruption. I believe, there is a lava field inside.

  16. Now that we have a clear view of Agung, we can see that the supposed rim collapse did not occur. So why did it look like the large outcrop on the left had disappeared? Well, it is part of the far side of the rim, so it was simply obscured by the ash column. Both sides of the rim can now be seen thanks to the current steam activity.

    • The red part is supposed to be an arrow I drew by hand, but it became a bit blurred by the image compression. There is no lava in this picture 🙂

        • Yes, I realized as soon as I saw the picture in the feed that red was maybe not the best of choices. It just happens to be the snipping tool default pen :mrgreen:

          • At first glance i did think………

            Good spot Tomas. I was wondering the other day if it may have been hot ash over topping the rim and coming down the flank that made me think the rim had been eroded. A trick in perspective on the original photo is obviously the answer. This still means that must be a low point on the rim wall from this view but i believe i saw somewhere that the northern rim is the lowest point..

  17. My penthouse apartment has an orangerie.
    In the orangerie I have a steam driven canon.
    I use that to fire upon ships out at sea.
    My neighbours hate me.
    This I write on Internet Explorer instead of Edge.
    All the hatred…

    • Have you tried running Malwarebytes to see if you have picked up any nasties affecting Edge? Have you tried checking your system files with the command sfc /scannow from the CMS prompt? Have you tried reregistering your apps including Edge with the Powershell command Get-AppXPackage | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register “$($_.InstallLocation)\AppXManifest.xml”

    • Tried posting this in Edge and it prompted an error

      This is to confirm the oranges never hit

      Carl is such a bad shot

      The hatred for MS is real however

      Test to see if posting image crashes

      This unusual waveform at 19:44 does not show in even updated IMO lists, funny looking thing

      • That’s probably a couple of microquakes in rapid succession. Large amplitude and short duration usually means small quake close to the sensor. You see this kind of quake all the time on the KIS drumplot and very few make it to the lists.

  18. Is there any data to show if Agung is still inflating or if the pressure has been relieved by the eruption so far?

  19. What some rain will do to highlight the amount of heat on the Pali and plain of “Kīlauea Volcano, East Rift Zone”


    • I think you’ll find many of us are monitoring the site, checking in several times a day at the moment.
      Thanks Mizar .

  20. Apparently, Agung has gone into idle. It’s mass ejection rate has dropped to about 1.93 m³/s. Total DRE is around 0.0115338 km³ (est)

  21. Looks like Agung has picked up activity on the seismogram since the rumble at 02:45 local time. I have not seen a flicker of light from the CCTV feed since around that time.

  22. And since I am me and we are celebrating something new at Öraefajökull we are playing this song to commemorate the event 😉

    For the newcomers… Lurking will explain the reference.

      • Thanks for the rescue

        To me, it looks like IMO is trying to find the dikes that re activating?

        • Ian or anybody else that can answer. Looking at the maps it appears that there are not many people living in the area. Do we know how many would have to be evacuated/moved if this volcano erupts (depending on the severity of course)?


          • The authorities said a few weeks back that around 2000 people are in the area every day, however only a fraction lives there. During summer, tourist numbers are bound to increase that number quite a bit.

          • There are people in the area and from what I have read they have a very detailed evacuation plan in place, what could be an issue is during the tourist season.

        • Not sure there are obvious dikes there. The linear feature off to the east is too straight to be real and I suspect an instrumental effect (a gap in the seismometer coverage, for instance – there are none on the icecap). An eastward trend over time may exist but will need more data.

          If it remains true to form, the eruption will start in the caldera and only after that possibly move to a flank fissure. It seems not a particularly ‘dikey’ volcano.

        • Looking at the first map, it sticks out that there is a concentration of larger quakes at depth about 2-4 km, east from the caldera.
          Some months ago there has been a remark that with one nearby working drumplot station Fagurholsmyri (fag) it was difficult to calculate a precise location of the earthquakes.
          Since first week of november other stations have been added to the IMO sytem.

          Quote IMO news bulletin 3-11-2017:
          “…The new stations are therefore an important addition to the pre-existing monitoring network for improving the sensitivity of the surveillance system. The current seismic network provides better information on the seismicity, it particularly detects small earthquakes (magnitude between M0 and M1), and also allows a better assessment of either location and magnitudes of the earthquakes. There is still considerable uncertainty in the depths of the earthquakes, but their seismic waveforms are consistent with a source located in the crust at a few kilometers depth. …”

          The second map could be an attempt to relocate/adjust some of those eastern quakes which took place in october and earlier.

          • Mystery solved Rob!

            That is exactly what is going on here

            Here are the relocated positions

  23. And in other news, an earthquake in Philadelphia is getting all my East Coast Faceyfriends excited. What should I tell them?

    • Tell them the long awaited Wilson Cycle has begun. In a few million years, Europe will crash into New York. What you are seeing are ancient faults reactivating. One reason why the moment tensor (beach ball) looks a bit odd is that that area is part of the ring faulting region from the Chesapeake Bay impactor. At 211 km, it’s outside the crater itself (85 km across), but would have felt the stresses quite well. (about 35.3 myr ago)

      Alternatively, if you want to tweak them a bit, tell them it was NKs latest test. A rehearsal of sorts. (Your mileage may vary)

      • I knew one of you’d come up with the goods! I don’t think I can get the North Korea one past them though – they’re all nerdy smart weird musicians (for some reason)

        • Hint. The intelligent ones are the easiest marks if you play it right. Typically the best way is to seize on a preconceived notion and play off of that. Done right, they will buy it hook line and sinker. Used to be one of my favorite past times on active duty.

        • It is the Turmp twitter account significantly widening the Atlantic rift and pushing Pensylvania closer to California Hawaii Russia.

      • Well, I used to be stationed at Earle NJ on an AOE. If it were Weapons Station Earle, it would be all over the news and quite visible. One of the reasons that the finger piers there are so long is that there was a mishap on the USS Solar on 30 April 1946. Anecdotally, there is a very frightened looking piece of twisted steel encased with a base and a plaque memorializing the casualties, reportedly where it landed next to the waterfront admin building. Now the pier is like 3 miles long. No pedestrian or bicycle traffic allowed. Busses only. It makes getting to work a bit of a chore since you have to find an elusive parking spot and then get to the bus stop. The train tracks only carry ordinance, no passenger cars.

        • The parking spot is elusive because the empty one keeps moving around. You have to weigh the likelihood of finding a closer one with the odds that the empty one will no longer be empty by the time you give up on finding a closer spot. The decision can cost you 15 minutes in walking or bus arrival time. I usually started at the closer lot then worked my way to the more distant lots on Normandy road.

          Geologically, the cool part about that is that the upper lots are technically up on the heavily eroded and wooded trap deposits of the opening of the Atlantic. Give or take a few glacial advances from past ice ages.

          • Lurk; you could tie that into volcanoes in a way: the WWII US Navy Ammunition ships were almost all named for volcanoes – Vesuvius, Sangay, Paricutin, Hood etc Given the nature of their cargo, someone had a VERY dark sense of humour

          • Along those same lines, Minesweepers tend to be named after birds or exciting words. Can you imagine the word that gets passed on the ships general announcing system when the captain of the USS Auk returns to the ship? “Auk, arriving”

            AM-161 would be equally perplexing…

          • for some reason I can not reply to Michael Don’s comment. So am replying one up the tree.

            The USS Shasta AE-33 was locally based, Back in the 1960s/1970s. The Shasta used to take the kids from my fathers work out for field trips through the straights into SF bay. There is still memorabilia from the Shasta about the house. One of the large shell casings, I think it is 70mm. about 3 inches in diameter and a foot and a half long. On the bar is an ashtray and other odds and ends, matchbook wine/beer opener. A much different time then.

            I myself briefly worked at the local weapons station in early 1990s. (just after the gulf war thingy.) When I was little this was known as Port Chicago. During WWII two ammunition ships went up fully loaded. The crater is still quite visible. The workers from the Southern US mutinied and have still not been fully pardoned. (They were of African-American ancestry.)

            The Army now runs the Tidal areas of the old weapons station. The inland parts are supposed to be handed over to the City of Concord. This will increase the area by 30 percent population. All the developers want to do is build pack and stack tenements. Well it is 30 miles to downtown San Francisco, but there is a mountain range in between. Sadly there is no direct passenger Ferry service to the city. The area is highly industrial, with a number of major oil refineries. Makes for a rather busy shipping channel.

  24. Now that dawn has broken over Bali, I think the crater area of Agung has had a vertical extension over at the back (as seen from Bukit Asah web cam). Looks like she chucked some rock up onto that area, the edge facing north-west.

  25. My current DRE estimate using Mastin et al and Darwin VAAC reports. Interestingly, it’s starting to look like an RC time constant plot. (The charge on a capacitor-resistor circuit) No, it doesn’t mean anything, it’s not uncommon for similar shaped curves to show up in different settings. In a preface to a book on explosive eruptions, Sparks noted that some volcanoes exhibit activity that can be equated to a sigmoid function. (A curve that generally shows how a system can avalanche from one stable state into another stable state) His description was about the bubble nucleation process in magma. (Think Mentos+Soda) ← The video does NOT show a chemical reaction, the Mentos provides nucleation points for the CO2 in the soda to form. It accelerates the dissolution of the CO2. {Note: back off on your volume first, the music in the video is a bit loud.}

    Safety Note for anyone microwaving water for tea or soup. It is possible to overheat the water if it is in a very clean cup or bowl. If the water is overheated, when you add something to the overheated water, this acts as a ready nucleation material and the water can flash boil, potentially causing injury. Yes, this is a real thing. Phreatic eruptions can be VERY energetic… and that is essentially what it is.

  26. A good-sized swarm at Öræfajökull overnight, and a range of depth where the shallowest quakes were near the caldera. I haven’t plotted it but the numbers sounds like a nice stack.

  27. Looks like a new strong tremor event at Agung has started at 16:45 local time. Drumplot seems frozen, so it’s not visible there yet, but the amplitude graph in the spectrogram shows a large amplitude, similar to previous events.

    un-spammed – Admin

  28. Did I just get thrown in the dungeon? Testing, testing…

    New strong tremor at Agung starting 16:45. Visible on spectrogram, but not on frozen drumplot.

    Yep, you were in the dungeon about to be eaten by gnomes – Admin

  29. I found this paper on the postglacial eruption frequency in Iceland, and it seems to show that only lava shield eruptions actually increased substantially after deglaciation, and that fissure eruptions and explosive events were negligibly effected. It also seems to show that the frequency of fissure eruptions has gone up in the last few millennia, after apparently no major events happened at all for much of the middle holocene.

    I dont know if anyone here has read this paper (probably have), but it seems to show general increase in large lava flood eruptions since the middle holocene, and also challenges the idea of everything going off the scale after the glaciers retreated.
    I have a big interest in icelandic volcanoes but im a bit of a noob when it tomes to specifics and I know some people here have personally studied/seen these places in real life and would have more knowledge here than I do.
    (It is from 2003 though so some of it might be outdated).



  30. 1pm: Mount Agung has ‘deflated’ since eruption

    The volcano has deflated 3cm since erupting on Saturday, according to Sutopo Purwo Nugroho of Bali disaster mitigation agency (BNPB).

    Agung had swelled by at least 4cm in the weeks preceding the eruption.

    Sutopo said that volcanologists are now investigating whether “the critical period has passed”

  31. There’s an update / press release on the Magma Indonesia site:

    Google translate does a reasonable job, although the translation says that there was “lava” flow (into rivers etc S of the crater) which should probably be “lahar”.

    “Based on multi-parameter data analysis, it can be concluded that until now (December 1, 2017) volcanic activity of Gunung Agung is still high and still in the phase of eruption. Therefore, the status of Mount Agung is still at Level IV (Awas). Communities around Gunung Agung and climbers / visitors / travelers are urged not to be, do not climb and do not carry out any activities in the Dangerous Zone Zone within the area of ​​G. Agung crater and in all areas within a radius of 8 km from Kawah G. Agung and added the sectoral expansion to the North-East and Southeast-South-Southwest as far as 10 km from the Crater of Mount Agung.

  32. Interview with prof, Pál Einarsson
    There’s magma movement deep under Askja and Herðubreið. However the pressure under Askja seems to be decreasing and has done so for the last 30 years, though in four areas close to Askja there are deep quakes that can only be explained by magma movement.

    There’s absolutely no reason to be worried though.

    Giggle translate does a soso result

    • Interesting.
      What proces does let the pressure under Askja decrease?
      Is there any theory/thought how pressure can decrease in a rifting episode?
      Magma movement could be caused by “under-pressure”; it ties to fill in to compensate the negative pressure. Just a simple thouht from someone who knows not too much about large scale pressure events. 🤔

      Can someone write about this a bit? 🙂

      • It can be explained by multi magma chambers system. There is shallow magma chamber and deep magma chamber. The movement can be in deep magma chaber, while old shallow magma is cooling, and the pressure is decreasing.

        Agung is in subduction zone, but also has two magma chambers.
        But I am not an expert about volcano. :).

      • “What proces does let the pressure under Askja decrease?
        Is there any theory/thought how pressure can decrease in a rifting episode?”

        Line two answers line one. As the plates move apart, the remaining crust undergoes tension which stretches it and causes it to thin, this in turn, lowers the pressure on any underlying magma mush allowing it to undergo decompression melt.

        I think something along this line is what happened at Holuhraun. The tension stress lowered the confining strength along the pre-existing fissure swarm and as the dike progressed down from the area of bardarbunga, it felt the lower stress holding the fissures closed and moved in that direction.

  33. New report for Agung confirms extrusion of new lava into summit crater- 20 million m3- which means that 1/3 of the crater has been filled up. Volcano has deflated slightly, but is being partially counter-acted by the continuing ascent of new magma, as seen in the periods of strong tremor (which seem to have increased since the drop in activity in the last few days), and deep quake activity. The first day of the “full” eruption was phreatic, where the leftover plug of the 1963-4 eruption has now been fully removed, with the new magma appearing to be mostly fresh (as in not much remnant magma from the previous eruption). So basically it looks like we are right about what is happening, and there’s still a strong possibility of a major eruption.

    • Does the crater have to be full for a larger eruption? Or can lava make its way out sooner via cracks or weak spots?

      • The amount of lava doesn’t really make any difference to what could happen, it’s more about if it causes the main vent to seal.

      • The lava acts as a safety valve: it allows the gasses to escape. The 1963 explosion happened after the lava solidified, trapping gas in the conduit.

      • And if many of you remember.. Kelud was quite energetic when it went off… mainly because there was no real way for it to degas at a slower pace.

  34. And now, just after 2pm local time, the big-time tremor is back on the seismograph. A quick look at the camera confirms that thick cloud has developed. This ‘tremor’ will indeed be caused by the daily deluge of the rainy season, with afternoon storms developing. Perhaps it as simple as the rain drops hitting the seismograph that causes the tremor signal.

    • 20171202/0700Z from Darwin still notes the plume at FL180. (ADVISORY NR: 2017/63)

      Jeebous, retired for 17 years and I’m still referring to date time groups. At least I’m not having to write and route the messages through the chop chain. 🙂

    • Yep I was right… not rain. Official tweet:

      “Continuous seismic tremor has taken place from 28 November 2017 through today (December 1 , 2017). Amplitude of the tremor has ranged from just above the background levels of the CVGHM seismic network to over-scale (i.e., exceeding the recording limits of the instruments used). The tremor is a result of the ongoing gas and ash eruptions through the summit crater.”

  35. According to the live cam on Youtube Gunung Agung is venting steam from its crater now. It seems to be that its conduit has been blocked now, the pressure inside the edifice is mounting, heading for a VEI5+ eruption now?

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