Prelude to Krakatau. II

In part I, we discussed the geology and current state of Krakatau. Now it is time to look at events before the Big Eruption. Was it hiding in the shadows, or did it make its intentions clear to all?


For centuries before its destruction, Krakatau was a familiar landmark. At least some of the time it was occupied. It is surprisingly difficult, though, to find good descriptions of the island from before the cataclysm. Partly this is because the company that governed the area, the VOC, was secretive, and partly because Krakatau wasn’t seen as important. It was just one of the many islands in the area. Between the Sunda Strait and Batavia was the region of the ‘thousand islands’ (in fact there are about 350) and these were more useful and received the attention.

Krakatau first appeared on charts around 1600. After 1700, it became included on published maps of the Sunda Strait although not in great detail. Better (or at least prettier) maps were made by the VOC, but these secret archives were kept hidden so well that they never resurfaced (with one exception described below). After 1800 the Dutch and British governments took over control of the region and the secrecy became less but they too paid little attention to Krakatau. In between, we have drawings made by several passing sailors showing the profile of Krakatau, and several brief descriptions including that of the 1680 eruption. The most detailed description comes from two visits during the Cook expeditions, providing painting of scenes on the island but sadly no map. Only after the main eruption had started, was someone finally send to measure up the island – but that was too late.

The most familiar maps of Krakatau were made in the decades before the 1883 eruption. One was republished by the Royal Society, in its Krakatau report with the famous cover picture of the eruption. A Dutch map from the same area is essentially identical, but has some longitude errors. The map shows the main peak of Rakata (800 m), the lower peaks of Danan (450 m), and the final peak of Perboewatan (100 m) forming a line running SSE to NNW, but they lack detail. The alignment seems to be an in-build direction for Krakatau: when Anak Krakatau first appeared, on January 3, 1929, initially the eruptions came from 6 vents on a line with a length of about 500 meters in the northwest-southeast direction.

Willem Lodewijcksz, 1598. Krakatau is top right, and is shown in profile with its three main peaks. (Source:

How do the maps from the 1800’s compare to earlier depictions? The oldest published drawing of Krakatau is from 1598, and is not a map as such but an orientation drawing which shows the horizon. it was drawn by Willem Lodewijcksz who was a member of the expedition of Cornelis de Houtman, the first Dutch trading attempt in the region. On 17 June 1596 he passed Krakatau (which he called Carcata and Cercata) and noted that it was densely wooded, but that sulfurous fumes rose from a barren, reddish coloured spot. He didn’t tell us which spot! In view of later events, it must have been Perboewatan. His drawing shows a profile with three main peaks, probably Rakata, Danan and Perboewatan. (Long island is actually taller than Perboewatan and its peak can also show up in drawn profiles.)

Various drawings of the profile of Krakatau are available over the time until its final eruption. A compilation is shown below. There are some differences but they probably represent different viewing directions rather than real changes! The accuracy may be debatable. The middle peak, Danan, apparently was a double peak and in some drawings the secondary peak is made into its own mountain. Verbeek mentions that Danan had several summits, which may have formed part of an annular enclosure of a crater, and that Perboewatan was not a single mountain but a hilly piece of land (although that was after the eruption had begun and Perboewatan had been disrupted). The drawing from Mueller in 1836 is the most detailed. It shows Long Island in detail, and shows Perboewatan rising above Long Island. That is interesting, because Long Island peaks at 162 meters while Perboewatan was later reported as 100 meters. The drawing is too precise to allow for this, and it appears that Perboewatan was considerably taller than 100 meters before 1883.

Top left: 1596. Top right: Braad, 1748; bottom left: Mueller 1836; bottom right: Rataka, prior to the eruption

Buijskes, 1849

Maps of Krakatau from before the 19th century are scarce. Pierre van der Aa included it on a map of the Sunda Strait but showed little detail. However, it turns out an older map does exist. And it appears to have come from those secret company archives.

The most famous atlas you have never heard of is the Blaeu-Van der Hem Atlas, finalized around 1670. It is the prize-possession of the Austrian National Library, and is listed on the UNESCO Memory of the World Register. A facsimile copy should set you back about 100,000 euros – the original is priceless (and that doesn’t mean cheap). The original work was from Joan Blaeu, who published it as the Atlas Maior between 1649 and 1673. It was the most expensive book published that century, with almost 600 plates. As each volume appeared, Laurens van der Hem bought a copy and had the plates hand-coloured by the top artists in Amsterdam. He also added many more plates. Van der Hem was rather wealthy, and he had turned his house into a treasure box. Amongst others, he owned Rembrandt’s David and Jonathan, nowadays in the Hermitage. Visitors would come from far away to see his collections. He is remembered, though, for this atlas, enlarged and beautified considerably from Blaeu’s version. He included whatever maps he could find or could commission: on completion his version contained 2400 plates and drawings! And it appears that Van der Hem somehow had access to the secret VOC archives in Amsterdam, and that his additions included their maps. His access may have come through Joan Blaeu who held the exclusive map maker contract for the VOC, but it wasn’t authorised by the VOC. During his life, Van der Hem never showed the plates of Indonesia to anyone; according to his daughter, this was to avoid getting the people in trouble who had given him the maps, without knowledge of the company. It shows he didn’t make this atlas as a show-off: he made it for posterity and as a work of art.

The plates are marvellously detailed. One of the additional plates shows both a map and a profile of Krakatau. The beautiful watercolours deserve space on this blog! (Click on the images for higher resolution.) The scanned originals, at better resolution, can be viewed at the atlas of mutual heritage.

A comparison between the maps from the 1800’s and the Van der Hem atlas. The former is rotated and scaled in order to get an approximate match.

Comparing this old map to the later ones shows surprising differences. There is an extra island, and the satellite islands seem to be further north of Krakatau than they should be. The small rock of ‘Polish hat’, forming a separate island, is visible, larger than it perhaps should be, and rather far from Krakatau. There are clearly major distortions in the map: the orientation and location of different parts are off, and the wiggly outlines indicate the sketchiness. These maps must have been made from a distance, and were not made for geographical exploration. After all, the VOC was there to make money, not to do science. But a separate island is harder to explain, as maps used by sailors should be reliable at separating land and water. A more detailed look, comparing the map from 1883 by Ferzenaar to this old map by scaling and rotating, suggests that the additional island is Perboewatan. The map makes a bit more sense that way although there are still significant mismatches. For confirmation, an independent map would have been useful. The drawing of 1596 also indicates a channel between Krakatau and the final peak. Later drawings do not show such a channel.

Map by Ferzenaar made in 1883.

Could it be that the northern half of Krakatau was a bit lower in the early 17th century, some tens of meters, leaving part of the island under water? Afterwards, the land in the northern half rose a bit, and the channel between Krakatau and Perboewatan fell dry. This is speculative as the evidence is insufficient. The map of Ferzenaar made in 1883 indicates a low corridor between Danan and Perboewatan, albeit still 50 meters above sea: for it to be flooded would require changes in ground level by that much. But the map is puzzling.

The drawing of the island in the atlas shows that the last peak was barren. It is not fully clear which peak this is, as the viewing angle is not indicated: it could be Rakata or Perboewatan. However, Perboewatan is more likely. This also fits with the earlier description of Willem Lodewijcksz of a barren, reddish, sulfurous spot. The lack of vegetation here (and only here) suggests something was stopping plant growth. Sulfurous fumes will do this quite nicely! Rakata, in contrast, appears to have been extinct since historical times with no reports of any fumaroles. Note there is no indication of a channel on this drawing.

The only documented eruption of Krakatau before the Big Bang came in 1680, shortly after the Van der Hem Atlas was made. The documentation is a bit thin on the ground though. It mainly comes from a German employee of the Salida gold mine on Sumatra, Johan Wilhelm Vogel, who reported that passing Krakatau in Feb 1681, the previously overgrown island had become barren and burnt. He said that large lumps of glowing lava were seen being thrown out on four places. Vogel also tells us that according to the captain, the eruption had begun in May 1680. He gives a description of that eruption which he obtained from the captain who had been near Krakatau when it erupted: it involves an earthquake, a cracked island (it is not clear what that meant), sulfur smell and pumice. Verbeek discusses Vogel’s report with some scepticism. Verbeek had checked that the ship did indeed pass Krakatau on that day in 1681, but the ship’s log makes no mention of an eruption or glowing lava being thrown out. If an eruption had been on-going, that would certainly have been written down. Neither does the log of the ship’s journey in May 1680 (the ship “Kasteel Batavia” which arrived in Batavia on June 12 1680) mention anything, even though the most minute details were normally recorded: the captain would have reported the actual eruption had he witnessed anything at all. Considerable embellishment of Vogel’s story seems likely. Elias Hess, in November 1681, reported seeing rising smoke and burned trees, and mentions an eruption a year before. He passed Krakatau on the north, and Verbeek in 1880 drew attention to a young looking lava flow on the north side of Perboewatan. (Verbeek mentions that there were several other such flows around Perboewatan.) It seems plausible that there was indeed an eruption from Perboewatan in May 1680. However, there is no indication that it was large or long lasting as this would have been mentioned in many ship logs – it appears no one saw it. Vogel’s report of glowing lava belongs to the land of creative writing.

The eruption produced lava flows and was effusive. We don’t know whether whether it began with an explosion. We don’t know whether Perboewatan changed its appearance after this eruption: was the mountain higher or lower, or had the shape changed? The lack of reports can be taken as indication that there were no obvious changes, and that this was what it appeared to be: a limited lava flow.

There are later reports of fumarole activity, but until the start of the final calamity there were no further eruptions and Perboewatan appears to have quieted down.

According to Hesse, Krakatau was uninhabited in 1680. That changed later, as we know from visits made by the ships of two of the Cook expeditions. In January 1771 the first expedition anchored here but did not go on shore. They reported that ‘there were many houses and much Cultivation upon Cracatoa‘. In February 1780 the last expedition spend a day here on the way back to England, without Cook himself who had died on another volcanic island. The reports describe a green island with some inhabitants, a coral reef, and a hot spring. John Webber made drawings of the village, which he later made into paintings. The mountain in the background in these paintings may be Danan.

Drawing of Krakatoa, John Webber, February 1780

John Webber, from a sketch made in Feb, 1780

The 1780 expedition wrote “Cracatoa is esteemed very healthy, in comparison of the neighbouring countries. It consists of high land, rising gradually on all sides from the sea; and the whole is covered with trees, except a few spots which the natives have cleared for rice fields. The number of people on the island is very inconsiderable.” Over the nine years between the two visits, it seems that the population had notably decreased.

The “healthy” part was stated with some reason. On the first journey, the expedition had bought water for the return journey to England in Batavia. Over the next weeks, quite a few people on board died, including the ship’s astronomer. The cause is not stated, but given the water-borne diseases which were rife in Batavia, it seems plausible that they carried the agents with them. The water (which needed to last them several months) came with a guarantee of cleanliness. (The locals had warned the crew not to trust that guarantee.) But let’s continue the Cook report:

Off the north-east end lies a small island, which forms the road where the Resolution anchored; and within a reef that runs off the south end of the latter, there is good shelter against all northerly winds, with eighteen fathoms water near the reef, and twenty-seven in the mid-channel. To the north-west, there is a narrow pass for boats between the two islands.

“The shore, which forms the western side of the road, is in a north-west direction, and has a bank of coral stretching into the sea, about one third of a cable’s length, which makes the landing difficult for boats, except at high water ; but the anchoring ground is very good, and free from rocks. The place where the Resolution watered is a small spring, situated abreast of the south end of the small island, at a short distance from the water-side. A little to the southward, there is a very hot spring, which is used by the natives as a bath.”

Half a century later, 8 September 1832, the US sloop-of war Peacock visited. On board was Edmund Robert: his official title was Captain’s Clerk but in reality he was President Andrew Jackson’s “special confidential agent”. This early James Bond was a gifted writer (his pen perhaps mightier than his sword), as shown by the vivid description he gave in his 1837 book ‘Embassy to the Eastern Courts’:

At daybreak the following morning a boat was despatched in search of inhabitants, fresh water, and yams; but after three of four hours search, returned unsuccessful. Two other boats were then sent under the command of the first lieutenant Mr. Cunningham: after a fruitless search, that officer returned at sunset, after visiting Long Island and Crokatoa. It was found difficult to effect a landing anywhere, owing to the heavy surf and the coral having extended itself to a considerable distance from the shore. Hot springs only were found on the eastern side of the latter island, one hundred and fifty feet from the shore, boiling furiously up through many fathoms of water. […] In reconnaitring between Forsaken [Verlaten] and Crokatoa islands, we were struck with admiration at the great variety, both in form and colour, of an extensive and highly beautiful submarine garden, over which the boat was smoothly and slowly gliding. Corals of every shape and hue were there – some resembling sunflowers and mushrooms; others, cabbages from an inch to three feet in diameter, while a third bore a striking likeness to a rose. The water was clear as crystal. […] The sides of the hills, to their lofty summits, were clothed with all the variety of fruit, forest and flowering trees common to intertropical climates: large flocks of parrots, shaking the dew of night from their downy pinions were seen wending their ways to the palm trees, in search of daily food, and monkeys in great variety were commencing their lively gambols amid the wild mango and orange groves. Again, gazing in delighted wonder beneath us, we viewed the superb scene of plants and flowers of every description, glowing in vivid teints of purple, red, blue, brown and green – equalling in richness and variety the gayest parterre. A variety of small fish, spotted, striped and ringed, possessing every colour and shade, were sporting in these regions of unsurpassed brilliancy and beauty. […] Above, beneath, around us – all was in harmony.

In spite of this beauty and harmony, the island was devoid of habitation. The small spring used by the old village was no longer there, and the (very) hot spring they had used for bathing had moved off-shore, become plural and was ‘boiling’. The village had lost its fount. Had volcanic activity increased since 1770? The lack of water caused by the off-shore relocation of the springs can explain the failure of the settlement. The coral and trees (and monkeys) show that there had not been a major eruption for a very long time, although it should be noted this was on the other, western side of Krakatau. The east shore seems to have been quite steep: the hot springs were 50 meters out from the coast, but ‘many fathoms’ deep. A fathom is 6 feet, so ‘many’ fathoms (5-10?) was perhaps 10-20 meters.

Drying springs can be an early indicator of increasing volcanic activity. An example is Budiao spring at Mount Mayon, which is the main source of water in the town of Daraga. In the year before recent eruptions, this spring produced notably less water. The reason is the inflation of the mountain which dilates the water-holding layers. Pressure drops, ground water level drops, and springs loose part or all of their supply. It can recover before the eruption begins, when inflation focusses on the actual summit and surrounding areas deflate again. One wonders whether this had been happening at Krakatau as well. The spring bubbling up 10 meters lower can point at lower ground water levels. But whilst Mayon shows this a year before an eruption, Krakatau was affected a century before the end.

We are left with the image of an idyllic island, worthy of The Blue Lagoon, with dense tropical forest, perfect coral, and warm running water. But the island may have been rising, the water supply had become intermittent, and the fumaroles and hot springs were signs of danger – in hindsight.

But in spite of all this harmony and beauty, barely 50 years later Krakatau would be gone – a paradise lost. No one saw it coming – only one person may have had an inkling. What happened? Had this all happened before? And why is Krakatau the sole source of activity in the Sunda Strait? All will be revealed.

Part III

(Ok, perhaps not everything. But we can give it a try.)

Albert, May 2019

No one saw it coming – but perception is a funny thing. For some light relief: can you count the black dots?

79 thoughts on “Prelude to Krakatau. II

  1. Part III is tentatively scheduled for Tuesday. It was harder than I had expected to locate the reliable sources!

    • I have had the same problem with sources for the several things I have tried to write as articles, turns out there just really isnt much even HVO knows about kilauea before 2000 years ago, not surprising but it has lead to me abandoning at least 2 article drafts to date… 🙁

      I wonder if it is plausible for future eruptions at krakatau to happen in the ocean, and so extend anak krakatau towards one or more of the other islands, the old island had probably been there for a good long time (probably at least a few 1000 years) and looks like the eruption center was migrating to the north over time but now anak is already in the north so the opposite might happen now, but probably not really soon.

      • Before 2000 years?! I don’t even think about that, it is already hard to reconstruct what was going on 300 years ago from what is known. The Kipuka Nene flows of about 200 BC marks to me the beginning of from when we have a faint idea of a few things about Kilauea’s history.

        • Kilauea is an absoutley hyperactive volcano .. most of previous eruptions are covered quickly in fresh lava flows
          Young surface masks its history of eruptives

        • Surface exposure is fairly well documented for the period before the current east rift episode, about 400 years ago to now because puu oo accounts for most of the burial and observations of the rift exist from before the 1980s so we know what is there, and the age goes up to 500 years for the rest of the volcano and pre-holocene on the hilina pali at the ocean. There are also papers and other information on larger eruptive events further back than 500 years, namely the uwekahuna tephra, which was about 2000 years back, but in that case I suspect that paper highly underestimates the volume, and it is quite old regardless. In general though stuff older than 10 years is a bit contradictory.

          It would be surprising if I did all this research over the last year and didnt manage to figure some things out 🙂

          • Well Uwekahuna is basically Kulanaokuaiki now, plus some small undated explosive events at some point between 200 BC-500 AD. Kulanaokuaiki tephra would be one of the oldest more or less well studied events, but for example what was going at the east rift at that time? well we don’t know, I say the Kane Nui o Hamo eruption, Puu Kaliu, but that is just speculation.

          • One day I will write something on kilauea, it would be out of character for me not to. At the moment though the only way I think I could make a good post that is actually interesting and engaging like this current article would be to coincide it with kilaueas next eruption so it is actually on topic and has something to keep everyone busy… 🙂

      • I had that problem too quite a while ago when I had planned to do a piece on Hualalai- I gave up quickly! Doesn’t help that I’m not that good at writing interesting things anymore…

      • whether anak krakatau could connect toward other islands may be covered in Albert’s articles – it will depend a lot on the underlying geology and until we’ve seen the rest of the story Albert is producing it’s going to be hard to know whether that gives us any tweaked understanding of what’s going on there. I’m guessing that in order to make enough land to connect islands the volume of eruption needed would be too big for the magma not to have evolved and become too explosive – unless perhaps there were lots of smaller constructive eruptions that Albert might tell us about.

    • Even though I am salivating at a part III I know how hard it is to do 3 big articles in a short time.

      Looking forward to your next instalment, now off for reading Krakatau II.

    • Jesper and Turtle:
      The subject of the article is Krakatau, and the comment you guys are replying to is about article scheduling. We have had this discussion previously.
      Please ponder what and where you guys Kilauea things.

      • Carl I was actually talking about how it is hard to find good sources sometimes that arent 40 years out of date and then relating it to my several unsuccessful attempts to write something about hawaii that is actually interesting. I havent tried to write about anything else so I cant use any other examples 🙂

        Then I also actually asked a question about krakatau but it has gone unanswered so far.

    • look forward to it, I remember some sketches and eye witness accounts on a video well before the eruption

  2. I am writing this comment mid reading.
    I have a suggestion to where you could source a possible part 4.
    The VOC was not the only such organisation.

    Sweden employed a large number of Dutch captains and shipbuilders in the 16th, 17th and 18th century. Many of those came from VOC and later Dutch organisations.
    They brought along substantial amounts of naval charts, personal logs and paintings of their travels.
    There is also the not so well known fact that the VOC allowed the SOIC (Swedish East Indies Company) rights to co-trade along their routes and to utilize their harbours and ports. Some of the Dutch installations was even manned by Swedish mercenaries. The ties was quite close back then between the countries since only together could they match the English naval power.

    The big difference is that every single scrap of paper, map, chart, logfile, and economic data of the SOIC and their associated Dutch naval captains remain in the Swedish National Archive. At least for the Dutch captains that had the good fortune (for historical reasons), to die in Sweden.

    Some of the oldest documentation might have been lost in the Three Crowns Castle Fire, but the rest is there somewhere in all those endless kilometres of the National Archive catacombs and vaults. Problem is that it is not that well catalogued and searchable in digital form.
    But, a visit there should give a surprising wealth of information if you apply your considerable charm upon the custodial clerks.

    This actually applies to quite a bit of history, the National Archives are extremely underused as a source of international history. I guess that the language barrier is a problem for most researchers when it comes to digging about for the nuggets pertaining their company.

    Another place to look would be in the Carl von Linné Collections, a lot of his disciple rambucted about on Dutch ships during the 18th century. And they where very diligent researchers trained in observing every little detail, and they also made massive amounts of maps and descriptions of all sorts of odd places.
    Obviously only the parts pertaining to the massive Linné project ended up in the official books, but the rest covers kilometers in the above mentioned archives, and at the Royal Academy of Science.

    I seriously suggest you book a few extra days in Stockholm the next time you give a lecture or attend a conference. There might also be a bit of additional things about the SOIC at the Naval Museum in Gothenburg since the SOIC headquartered there.

    Best wishes on hunting Dutch naval secrets in Swedish Archival Catacombs… You are on a great hunt for a fantastic piece of unknown history.

    • Here is a list of keywords, people and organisations that might be fruitful to research in the National Archives, either by yourself, or any other itinerant volcano historian.

      1. Willem Usselincx, 14 June 1626 the king awarded him a letter of privilige pertaining to;
      2. Söderkompaniet
      3. Ostindiska Companiet av 1672
      4. Solen, Ship
      5. Trumslagaren, Ship
      6. Johan Leijonbergh, ca. 1660, Swedish representative in England
      7. Olle Borg, 18 year service at the VOC.
      8. Knut Kurck
      9. Peter Schnack
      10. Friedericus Rex Sueciaes, the first successful Swedish ship to the east indies 1735.
      11. Ostendecompagniet
      12, Colin Campbell
      14. Niclas Sahlgren (Yup, that one)
      15. You should also ask for any papers containing to the names mentioned in this article. You can probably find a lot of ways to look further via records about the VOC itself.

      • The profile made by Braad comes from the Swedish archives. Obviously I haven’t looked at those myself but someone (Pandang) did.

        • Now I am confused, do we have a commenter named Braad who went there already?

          With Pandang, do you mean the guy with listing all the worlds volcanoes?

          I would either way visit the place myself. Because with each archival search you would get a different result, and Pandang probably did quite a broad search at a single place.

          Doing a standard electronic search could give things, but to really get to the bottom of the place you would need one of their archival experts to help out with the digging. I could perhaps get one to help me a bit with a lot of begging, but I pretty much bet that they would throw open the doors and give you the keys to the place Albert.

          • Top-right profile in the figure with four profiles in the post above. It came from a paper by Neuman van Padang who found it in an obscure publication. So there may be more hiding. But if you are sailing past an island, it is much easier to sketch the profile than to make a map. That is probably one reason for the scarcity of available maps. Even the one used by the Royal Society in their Krakatau report (and used in all the ‘then and now’ overlays showing where Anak is located on old Krakatau) has inaccuracies. I tried to reproduce that overlay and did not quite get the same result.

    • And after finishing my reading session (alternating between googling)…
      Albert, quite simply stunning. Now I will go back to biting my fingernails waiting for the conclusion.

    • And here is the English language version link to the National Archives (Riksarkivet in Swedish).

      And since they have millions of maps archived, and discover new every day in their catacombs, it is pretty much a given that there will be at least one unknown of Krakatau pre-boom.

      Who would’ve thunk that Swedes are such diligent filing clerks?
      A mid 16th century ancestor of mine was inducted into the nobility for his military filing system. He later vomited in the Kings soup during a party and was banished to Northern Sweden to rule the Samí people as the first Lappfogde. What followed is a particularly dark part of the Swedish history, only surpassed by the slavetrade. The last Lappfogde was my great-great-grandfather, who was shot and killed in the Kautokeino Uprising. My maternal grandmother vividly described how his bones clonked in the breeze as the bag containing them moved in the barn they where hanging in. The winter was to cold that year to bury him.
      Another of my esteemed and extremely nasty ancestors performed one of the largest land grabs on the planet as he stole 1 200 square kilometres of land, at least if you count land grabs that has withstood the test of time. Not even I know how many he killed while performing that feat. Afterwards the King gave him a Letter of Deed for the land, sealing things for perpetuity.
      This has kind of put a stopper in my hamper in regards of researching my ancestors, they are just a series of unfathomable arseholes.

      • Its okay. A friend of mine found that one of his ancestors had a habit of crashing wedding parties and getting into knife fights as a hobby. Yes, he is Finnish by decent.

      • Carl this made me spend an hour trying to find this cartoon. Turns out it is from a Jon Stewart book but your complaints about your ancestors brought it to mind.

      • So what you’re saying is basically that this volcano lair dwelling bond super villain kind of thing is actually in your genes…

  3. Tropical paradise indeed
    And sounds like the perfect place for a pirate to bury his stolen gods and things

    • Any gold buried would have been spread quite thinly in the big eruption 🙂

  4. 🙂 at first reading my mind thought Volcano Cafe at VOC because i have a living room full of Grandkids playing on video games on the tv and they needed some supervision and i will admit only half a brain was on either but i didn’t want to wait any longer to plunge into “Krack-a-toe-a”. (one never knows when a trip to the emergency room will interrupt) which is usally one of my goals for their visits (avoiding a trip to the emergency room). Will reread appreciatively later too! Love going to distant places via this blog because not only do we get to see the present but we can visit the past and not only know WHAT happened but also WHY it happened. Best!motsfo

    • and an additional 48 if counting the big black square dots…. (do dots have to be round?? ) 😉

      • No.
        But if I cover each “dot” leaving any individual one exposed, it ceases to be a black dot. So I tentatively deduce that it is an optical illusion of some sort.

      • That was actually a reply to Gaz. Neil is right, there are no black dots. (Big black squares, yes. Black dots, no.)

        • I was being rather facetious with my answer; the optical illusion, when viewed through tired eyes, is somewhat magnified.

  5. Another great one! Just as it gets more and more interesting, you get to the “to be continued” part, and then there is that optical illusion to piss one off even more. 😀

    The research on this probably took some insane long hours of work and reading.

    It is fascinating how the very shape of the island changed as there were some insane things going on below ground. The inflation must have been insane. This would probably raise alarms today. But back then, how could one know that (or even consider) there is a large body of molten rock below the island, going into overpressure?

    Over and over again, it seems that the greatest survivability tool is science and knowledge.

    Looking forward to more.

    • P.S.
      Add “common sense” and logic to the list of survivability tools ( meant on a population scale), since that seems to be lacking in our current times.

      • Add ‘community’ to the list and you have got the anti-thesis of the current society. VC excepted, of course.

        • Of course, “the power of numbers”, how could I forget. 🙂

  6. Swarm in Grimsvötn… makes me very happy…
    There is many 100 s of km3 of thoelite basalt inside that needs to be waken up

  7. There are no black dots but there are white dots, the black squares and greyish lines trick your brain into colouring the white dots when they arent. 🙂

  8. The map of Ferzenaar made in 1883 indicates a low corridor between Danan and Perboewatan, albeit still 50 meters above sea: for it to be flooded would require changes in ground level by that much.

    Not out of the question with these subduction arc stratovolcanoes. There’s inflation of that magnitude going on at Iwo Jima now. Perhaps what’s happening there now was happening at Krakatau in the early 1800s, and what happened at Krakatau in the late 1800s will happen at Iwo Jima in the last few decades before 2100.

    And all of that is a joke compared to the size of ground movements during quiet, inter-eruption periods at the really big restless calderas like Campi Flegrei … there are whole neighborhoods of Roman cities deep underwater that were high and dry 2000 years ago around there. And much of that uplift and subsidence is just from the hydrothermal part of that system …

    • And perhaps they didn’t see the whole corridor flooded. A deep inlet, from a distance, will give that impression as well. That would not require as much inflation.

      There are two strands of evidence pointing at inflation: this map, and the moving springs. The two together are more convincing that each on its own.

      I am convinced that some better maps were made: if anyone can locate one, please let me know! Find the one on Van der Hem was quite a surprise. The person who drew my attention to it apparently had no idea maps of Krakatau were rare: it was mentioned just because the name Krakatau was well known.

  9. Posted on TwitteR. thoughts? There doesn’t seem To be a time range associated with these images

    ‘Amazing InSAR derived velocity field of Iceland presented by Vincent Drouin of @uni_iceland at #LPS19 today. My highlight image of the week. Countrywide #InSAR is so much easier these days.’

    • Hard to judge. Left is the horizontal velocity and shows the plates moving apart. I assume that right is vertical. As the entire icecap is surrounded by ‘up’, I assume what it shows is the response of the land to the melting of the icecap: the immediate area goes up, more distant areas go down in response. That suggest this covers one or more years.

      • Am only I confused that the MAR (zero E/W movement line) north of Askja is a bit more east than you see in your average textbook?

          • Sounds reasonable. The seismicity does put MAR on the proper line, which makes this InSar plot interesting. And I am not sure that 100% of the uplift at Vatnajokull is isostatic rebound from ice melt. Ice melt was fairly uniform, while the uplift is not. East Vatnajokull for example. A lot of it is of course from the loss of ice mass, but some could be from the plume pressing on the crust. Not all of it of course, but it should be detected. Other glaciers do not have the same pattern, despite also having loss of ice mass. Granted their size/numbers are far less than Vatnajokull’.

  10. Enjoying the articles Albert. Eagerly waiting for Tuesday to get here.

  11. Off topic. Why are there so many eq in new zeland? There are some big volcanos on and around the island.

    • Most of North Island is covered by large calseras. White Island, to the north. Is one of the more recent manifestations. Lake Taupo is one of the later Large Caldera events… but even it is just a daughter feature from a larger Caldera event from thousands of years before it.

      If I remember correctly, one of the odd things about Taupo’s last event, was that it showed “almost no zonation” in it’s eruption. That roughly means the whole chamber went up at the once as a well mixed and homogeneous unit.

      • Most of the TVS is just bedrock that has been melted by the enormous heat source below + the thinning of the crust. The trigger event I believe is often just a vigorous injection of basalt into the now-melted bedrock. Breaking the roof likely also would lead to further decompression melt.

        I think this is part of why you don’t get lots of zonation… the TVS isn’t like a traditional volcanic zone as we’re accustomed to with many arc volcanoes where the magma source is mostly newly accumulated magma slowly percolating into a magma chamber, while acquiring *some* assimilated magma on the way up from the mantle wedge. Most of the source magma in the TVS is simply already there since it’s the bedrock itself.

        This is another reason why I personally am not of the belief that many of the supervolcanic eruptions would be preceded by massive inflation as many here have speculated. For supervolcanoes, most of the supervolcanic material is not new magma coming up from depth, but rather melted bedrock from a combination of heat + decompression melting from spreading. It’s not a coincidence that almost all the enormous caldera eruptors also exist within localized thinning / spreading zones.

      • The thing that “worries” me is that there a quite a few ‘supereruptions’ to be found and these are often/always inside an existing larger one. Presumably the existing larger one blew somewhere that would have been unexpected at the time (if anyone had been around to monitor it). So its likely that the next really serious ‘supereruption’ will happen where there is no pre-existing volcano.

        Of course a series of ever-larger eruptions on the same site would look just the same, each one eradicating the previous one.

    • One of the reasons that area doesn’t come up as much here on VC is that it is hard to talk about them without seeming like a scaremonger.

      When the North Island systems go. They go big. That’s their history.

      • And fast, which I think is the even scarier thought…. *not trying to fear monger.*

      • Definitely. A nearby system probably took about 12 hours from initiation to full on eruption. The 1886 eruption of Mount Tarawera.

        Many accounts state that seismic activity began 2 hours prior to Tarawera splitting open Hekla style and erupting from each peak.

        Now, this is about as spooky as I want to get; the melt formation region is right about at the 110km contour of the subducting slab.

        ASSUMING that this is where the feeder dike originated, that puts the travel speed of that dike somewhere between 9.1 and 55 kph… or just over 15 meters per second on the high end. The nasty bit is that this could be considered typical of volcanic systems in that region.

        Now, to quell things a bit, it is most likely that magma began from a shallower chamber that had accumulated melt and the travel time for the final feeder dike was much lower in velocity. Either way, the place can get vigorous quite fast.

        Note: ALWAYS be careful when assumptions are made. My look at it assumed a worst case situation. The only thing that can be drawn from this is that the volcanoes on the North Island can be just as surprising as Hekla if you don’t pay attention to them.

        Some light reading…

        • It is quite a common meme here that hekla blows up without warning but really any volcano that erupts frequently will do that. Heklas recent eruptions were sudden but probably not its older eruptions that occurred after decades or longer of dormancy.
          In my opinion the tarawera eruption is a way more scary and serious event than even heklas worst case scenario, hekla was silent in 2000 but an eruption was far from unexpected and was even predicted pretty accurately, tarawera did an explosive eruption of low silica picrite basalt on a mountain formed out of effusive rhyolite domes, in a volcanic province composed of 90% silicic igneous rocks, you dont get much more unexpected than that, hell even a VEI 7 was more likely than erupting hawaii-type basalt in a plinian eruption…

          One other thing that really interests me about this eruption, the way this would have actually looked if you were near it. This eruption is often written as a plinian eruption, which makes leople think of pinatubo, but there is one big difference. This was not cold silicic rhyolite mush, this was fresh hot basalt right from the mantle, probably even hotter than the lava in hawaii, the vents of this eruption would have been glowing like a blast furnace, think of all the pictures of fissure 8 at night and how strongly it glowed over the whole area and then now make fissure 8 10 times longer and with 2000 meter lava fountains, and a dense black mushroom cloud above everything… ._.

          • Yet surprisingly few people died and mostly in the crater itself. It is quite an impressive hole, particularly when you take a rather long boat ride in a quite large boat on the lake.

            Not something to have been very closeto when it happened, Mt St Helens was minute by comparison.

          • The Tarawera fountains where so intense and tall and simply energetic that no clastogenic lava flows where formed I think
            It all became tephra and ash and lapilli I think peles hairs been named in a few sources about Tarawera and thats a strong clue that it was a fluid basaltic eruption with immense fountains and huge ammounts of gas
            The lava all became gas foam spray. Tarawera was extremely gas rich
            Skaftar Fires woud have been very similar at start …

          • The most ominous part of it though is the implication that erupting basalt has in this area. TVZ is basically a massive batholith, and a large basalt intrusion is probably what makes this erupt as large calderas like taupo, with the amount of magma heated to the eruption point being the limiting factor in eruption size. The thing is, the tarawera intrusion didnt make this happen, the intrusion went right through everything and erupted on its own which seems to be a very unusual thing. That also means this spot still has all the same potential to erupt big as it did before 1886, it is as though nothing ever happened here at all… That is the really dangerous part, if we see signals of small deep quakes large enough to be felt (this did actually happen in 1886, but was not recognised until later) then leave, fast. It is not often that you can say this is more likely to lead to a VEI 8 than a repeat of the last eruption… basically eruptions here are rare but if they do happen it really goes all or nothing, when even the starting intrusions can be VEI 5 in their own right you know this place means business…

          • TVZ is a massive seriers of Rhyolite chambers feed by diffrentiating basaltic magmas.
            This is feed by both by the subduction and decompression melting of the TVZ back rifting generating massive ammounts of magmas.
            Each 100 s of km3 to over 1000 s rhyolite magma body either blow out during major plinian and tuff phases or becomes intrusive granite batholiths.
            Tongario and Mt Doom likley acts as pressure valves for now
            But its questionable how effective they are

            TVZ haves one of the largest concentrations of VEI 7 and VEI 8 explosive calderas on this entire planet
            the whoel area of North Island is covered totaly covered in tuff and igmigbrites and ashfall a small sillic explosive LIP
            There si also many shields of thick sillic flows and buried calderas

          • Tongariro and ruapehu are probably not side vents of TVZ, they are basalt-andesite stratovolcanoes, pretty standard island arc volcanoes. Taranaki is also a pretty normal volcano though it is displaced from the rest of the arc but probably not so far that it is necessary to explain it separately.

            TVZ maybe the most impressive thing to watch though woukd be if a large scale effusive eruption happens, preferably without a big explosive start. Yellowstone has done rhyolite flows in the 10s of km3 range 3 times since its caldera firmed, its like an entire mountain formed in one go. Same has happened in the andes with the chao dacite. Tarawera is actually a smaller version of this sort of eruption that formed in about 1320 AD, so imagine that but 10 times bigger. Santiaguito is also a small version of this eruption type too, and one that is still ongoing so you can see how long these things can last.

          • Note for the casual reader. “clastogenic” refers to the Ashfall that is so hot that the material sinters (welds) into place as soon as it stops moving. “Ignigbrite” is another common term. Think “the end result of a pyroclastic flow”. Generally these come from a silica rich eruptive column such as what entombed Pompeii and Herculaneum in 79 A.D.

        • Yeah, it does send a chill down your spine when you sit and think about it.

          The only reason Hekla has such a reputation around here, is that in it’s 2000 event, the seismic precursors would not have been felt by an unaided (non-instrumented) human standing on the summit until about 10 minutes before it went up. Basically, if you didn’t get a text message or some other alert notification, you would have been toast.

          Just going by seismos, the quakes didn’t start until 60 to 90 minutes before showtime.

          From the tale I’ve heard from Carl and the others, IMO found out about it when someone happened to be getting a cup of coffee and noticed the strain-meters going ape-shit.

      • That’s not really true. North Island has been the most productive rhyolitic system of the last ~50,000 years at least – but still, most eruptions in the TVZ are small. Large ones are more frequent here than elsewhere, but they’re still the exception, not the rule.

        • Irs more that what happened in 1886 was very atypical of tge area, and compounded that it was also atypical of basaltic eruptions in general. My quote of a VEI 8 being more likely than an 1886 repeat has no base either I am just not aware of any similar event recently, and there is no evidence of other basaltic eruptions there either (fissures or lava flows alike). From what I can gather there has been at least 4 VEI 8s and more than the equivalent of VEI 7s, and that only 10% of the rock is not rhyolite. If the province has 20,000 km3 (probably way more but I dont know) then that is 200 km3 of not-rhyolite, and in reverse to basically everywhere else mafic rocks are the most rare products, maybe 1%, 20 km3. That means with those numbers maybe only 10 eruptions like 1886 in 2 million years. No idea if im even close with any of those numbers but it sounds at least plausible.

          Another thing, 1886 was at least 1 km3 of dense magma and was 550 years after the last eruption, that is an average supply of 0.02 km3 of base melt per year, in just that area. The entire area of the TFZ could be getting volumes of 0.2 km3 a year or more, which is going at hawaii levels. Its obviously a much larger area so there is no concentrated 1500 C heat source like there is at hawaii but even still this is an enormous supply rate for a silicic volcano, if it wasnt under a thick section of continental crust with lots of granite to melt the TVZ would be like the klyuchevskaya complex in kamchatka.

          Lava temperature was indeed very high too, and also wasn’t entirely explosive, there are dikes in some places from the 1886 eruption showing at least sone places were more or less fire fountaining vents, only the vents under the lakes and on the far northeast end were explosive, it is probably the shirt duration of the eruptiin why there are no lava flows. At these dikes the rhyolite of the old domes was completely melted and turned into obsidian on contact, so these vents would have been very hot, glowing bright orange or more. It doesnt appear there was anyone close enough to see that who survived the eruption though… :I

  12. First paper on Ultima Thule

    Initial results from the New Horizons exploration of 2014 MU69, a small Kuiper Belt object


    Both MU69’s binarity and unusual shape may be common among similarly sized Kuiper Belt objects. The observation that its two lobes are discrete, have retained their basic shapes, and do not display prominent deformation or other geological features indicative of an energetic or disruptive collision indicates that MU69 is the product of a gentle merger of two independently formed bodies.

    Fig. 2 Shape model for MU69

  13. I have added a profile drawn by Buijskens in 1849 to the post.


    Found this just now, for anyone who wants to see what a real curtain of fire looks like this is one of the best videos ive found.

    About 1 month later, it looks like this eruption also moved into the stage where the vent became an open hole into the magma chamber, much like fissure 8 and holuhraun, there are no reports anywhere but I wouldnt be surprised if there is some sort of large collapse feature at sierra negra now because of this, probably not a caldera collapse proper but at least faults on the floor.

    • Very pooooor colour in the uppermost video
      Camera is overexpoused and everything is white
      Thats how a komtatite eruption woud look like white hot

    • Apparently the 1979 eruption was similar in size, I think that the eruption last summer was a typical Sierra Negra eruption.

      • Yes sierra negra is a serial big erupter. 2005 was small by its standards but still it was what I would call a ‘big’ lava eruption, 0.12 km3.

        1979-1980 was actually bigger than last year, about 1 km3, which is about twice as big as last year and similar in size to fissure 8 and holuhraun, but erupted in less than 2 months.
        Big difference is that eruption was not gravity driven, it happened close to the caldera and not the flank, 2005 was also like this but slightly within the caldera. Last year was the first distal eruption from sierra negra in at least a century, and by far the biggest in the time it has been observed. The fact it coincided with the same sort of eruption on kilauea is even more interesting, especially with how similar the eruptions were.

        • Turtlebirdman
          The East African Superplume thats the largest mantle plume on Earth for moment

          If it popped up under pacific s oceanic much thinner litosphere
          It woud make a huge oceanic LIP or something like Tamu Massif I think?

  15. New quakes at Herdubreid in the past few hours, some of them at interesting depths. I don‘t have time to check the drumplots but I‘d not be surprised if they indicate a new influx of magma into the system.

    • One more quake to complete the circle and we have a caldera!

      don’t worry – just kidding..

      • It would be ultra cool if we had focal solutions for them… but they are a bit too small for that.

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