Öraefajökull – A challenge for volcanology

/ 18/11/2017

Öraefajökull from the air showing the cauldron. Picture from Icelandic Met Office.

A couple of years ago I was asked on a radio show which volcano in Iceland I wanted least to erupt. I quickly answered Öraefajökull. It confused everyone, and I got bogged down in explaining why an unknown (to the layman) volcano would be that bad.

It is though true, if there is a single volcano in Iceland that I do not wish to see erupt, it is by a longshot Öraefajökull. And that for a great many reasons that I will try to explain down below.

At the same time, it is also a great challenge for volcanologists to decipher, also something that I will get back to down below. But first, let us get into the nitty-gritty of this severely understudied volcano.

The background of Öraefajökull

Cumulative Seismic Moment plot showing the rapid increase in released energy indicating an increase of magma in the system. Do especially note the events in late 2005 and August 2011, these two are intrusions. Image by Andrej Flis.

Most people interested in Icelandic volcanoes know that Öraefajökull is the tallest volcano in Iceland with it’s 2110 meters above the ocean. The actual top of the volcano is called Hvannadalshnúkur. The volcano has a 14 square kilometres caldera that is five by four kilometres across.

It is the second largest volcano by bulk in Europe, only surpassed by Etna, and it is the largest volcano in Iceland. But it is not the size that is the real problem here.

But, before we get into the problems, let us instead talk about age. For being an Icelandic volcano Öraefajökull is really old. We know this since there are two layers that have reverse polar magnetization. The upper reversed layer is fairly weak, and this places it as more than 41 400 years old. In other words, we have stumbled upon the “Laschamp event” – a failed magnetic pole reversal that only spanned 440 years.

GPS trajectory confirming rapid inflation, and a rapid dip as the cauldron formed and the Jökulhlaup releasing water causing the mass of the water to counteract the inflation signal. Image courtesy of Icelandic Met Office and the University of Iceland.

Above and below that reverse magnetic layer we find normal magnetic polarization. But, as we go deep down into the bottom layers of the volcano we find that they are strongly reversed in magnetic polarization. This put’s the origin of the volcano prior to the Brunhes-Matuyama Reversal 781 000 years ago. (And no, a polar reversal is not an extinction event.)

So, even if we do not know the exact age of the volcano, we do know that it is by far the oldest active volcano in Iceland. But, first we must talk about the location.

Öraefajökull is situated outside the ordinary mainline volcanic belts in Iceland. Instead it forms its own volcanic belt called the Öraefajökull-Snaefell Volcanic Zone (ÖSVZ), alternately also called Öraefajökull Volcanic Belt (ÖVB). This belt contains 3 old volcanoes. From north to south we find Snaefell (not the same as the famous Snaefellsjökull), and Esjufjöll.

Caldera perimeter plot filtered at M1. Image by Andrej Flis.

Snaefell is most likely extinct, or heading that way. No known Holocene eruption has occurred from this volcano. It is also seismically inactive. Esjufjöll is an active volcano that may have erupted as recently as September 1927 when a large jökulhlaups came gushing out from the volcano, and there was a light sprinkling of ash on the glacier. It is also seismically active with infrequent earthquake swarms.

As Öraefajökull Volcanic Belt was pushed towards the East from the main volcanic line in Iceland it started to have more infrequent eruptions. In the beginning the volcano was constructed of thick layers of regular Icelandic basalt, but as time moved on it started to produce ever more evolved magmas richer in silica, transcending through andesite, dacite into the rare realm of erupting mainly rhyolite.

The rhyolites at Öraefajökull contain between 70 and 75 percent silica, depending upon if the sample is taken from the tephra falls, or from extruded domes or spines on the top of the volcano. Normally this would be rather sticky, but due to a neat trick of nature the rhyolite at Öraefajökull is both rich in gasses and unusually hot. This is caused by repeated intrusions from depth into the system of basalt that delivers the usual for Iceland high content of volatile gases, and also functions as an ample heat source keeping the rhyolite merrily boiling.

Satelite image showing Öraefajökull and the cauldron. Do note that the cauldron looks like a mound instead of a depression. Image from the Icelandic Met Office.

Sometime during the last interglacial the volcano suffered from a major eruption in the form of a large VEI-6 eruption that gouged out the caldera. During the end stage of that eruption several rhyolite spines and domes were extruded, among them Hvannadalshnúkur.

After that the magma system revamped itself and the bottom of the caldera started to suffer from resurging dome building in the middle and eruptions resumed.

During the Holocene there have been no less than 5 known eruptions. The first 3 are badly constrained in time, all we know is that they happened after the last ice age, and prior to colonization.

One of those was yet another VEI-4 explosive event from the caldera, and the other two were flank events with rhyolite lava flows and dome extrusions.

June 1362

This infiltered seismic timeline shows the increase in earthquakes over time, but all the small earthquakes hides things. Image by Andrej Flis.

Thanks to the crafty Icelander’s there are an abundance of written records about the coastal area below Öraefajökull prior to the devastating eruption. We know that more than 30 farmsteads existed in the region, and that there where 4 main churches. We also know that there where more than 220 people of age living there. So, with the normal abundance of children we can safely say that there were between 400 – 500 men, women, children and priests (these where not counted in the same journal as the farmers).

The eruption caused a major Jökulhlaup with a maximum discharge estimated to be between 100 000 and 250 000 cubic meters of water per second. That amounts to between 1 and 2.5 times what the Amazon can produce as a maximum. Roughly two thirds of the farms and three churches was unceremoniously picked up and dumped into the ocean complete with all hands and animals. The other farmsteads were eradicated by between 1 and 2 meters of un-compacted tephra.

A distance of 160 kilometres of the coastline was completely destroyed or massively changed. Most likely not a single soul survived the ordeal, but there are anecdotal tales of either an old woman and her mare, or a priest, surviving. If a priest had survived we can safely bet he would have written down an account of his ordeal, that did not happen, so we can strike a surviving priest. There may have been a woman on her mare, but in all likelihood, she was out travelling and did not witness the destruction of an entire Icelandic region. As such this was the deadliest eruption in Icelandic history.

Here is a longterm seismic timeline showing that M2+ earthquakes becomes deeper over time. The recent shallow ones are related to geothermal field inception, that in turn caused the cauldron. Image by Andrej Flis.

Several sources state that there was a smaller Jökulhlaup coming out of the mountain in 1331, so we can safely assume that this means that there was a hydrothermal event back then, or even a minor sub-glacial eruption. There are though no mentions of earthquakes or tephra from that year, so whatever it was, it was minor compared to the later event.

My interpretation is that there was an intrusion from depth occurring in 1331, quite possibly like the one we are seeing now. And that heated up a geothermal field enough to melt a considerable amount of water that leaked out as a Jökulhlaup.

This eruption changed the coastline, an area of 50-meter-deep ocean was after the eruption covered with debris and tephra and became a new piece of land extending the Icelandic coast quite a bit outwards.

This seismic timeline highlights the deep intrusion pushing upwards from depth. Image by Andrej Flis.

The total amount of ejected tephra was between 2 and 5 cubic kilometres, placing the eruptions as a solid VEI-5. Even though both Lakí and Veiðivötn ejected more ash and tephra, those eruptions were not per see explosive events. Therefore the 1362 eruption is counted as the largest explosive Icelandic eruption since settlement.

In the annals the eruption is said to have lasted for almost a year, but the later stages were said to have been low level activity compared to the main phase of the eruption in the beginning.

August 1727

And here is a crossection and from depth image showing the path of the deep intrusion, and the silent area that most likely is a deep magma reservoir. Image by Andrej Flis.

Even though this was a far smaller eruption rated as a mid VEI-4, it was still almost as deadly as the first one for the residents that had picked up farming below the mountain.

Once more a major (but smaller) Jökulhlaup roared forth and swept away farms, churches and assorted people and animal. And once more ash and tephra took its toll. It is estimated that a full two-thirds of the residents perished this time. At least one priest survived and wrote a highly chilling account of the devastation.

This eruption was also long lasting, and did not end until well into 1728.

Timeline of the current events

Lidar image showing the caldera and the resurging dome at the centre. The cauldron is above that dome.

During the summer seismic activity under Öraefajökull picked up and transcended normal background levels.

It all began with the for Iceland usual deep (20 to 30km) earthquakes that indicates that magma is being pushed up from the depth. These earthquakes occurred to the south-west of Öraefajökull, but trended as they progressed upwards in under the caldera.

The origin of the upwards mobile magma was either from a deep magma reservoir connected to the MOHO via an open conduit, or came directly up from the MOHO. The earthquake data seems to support a deep elongated magma reservoir (wedge), but more earthquakes are necessary to say that for certain.

After this initial intrusion there was a month-long hiatus in activity before the main ruckus began. This time shallower earthquakes were the main ingredient of the seismic swarm indicating rising magma.

What is apparent is that there is a silent zone between the deep earthquakes and the later upper earthquakes. This indicates a slightly off-centre magma chamber roughly the size of 20 to 40 cubic kilometres at about 17 to 14 kilometres depth.

It is quite likely that there are smaller chambers higher up filled with extremely evolved rhyolite, but those would not be visible on these types of plots, and would need far more earthquakes to find and accurately reproduce.

All of this indicated that the volcano was reactivating, but nothing thus far pointed towards an impending eruption. It is after all quite common for Icelandic volcanoes to have several large intrusions prior to an eruption.

Yesterday a pilot found an astonishingly large cauldron inside the caldera of Öraefajökull. A cauldron forms as ice is melted from below by increased geothermal energy, and as the water leaks out in the form of Jökulhlaup the ice above sags down. A cauldron is easy to mistake for a caldera by laypeople, but they are not the same.

In Iceland cauldrons are often a sign of either a large geothermal event, or a small sub-glacial eruption. As of writing this, we do not know which of the two types of events have happened, but it was most likely a very large geothermal energy increase and not an eruption since there is a lack of seismic signals associated with an eruption.

The Jökulhlaup is rather slow and small compared to previous Jökulhlaups, but according to locals the water is reeking with the smell of sulphuric compounds.

The size of the cauldron is prodigious and should have caused a larger hlaup, so it is entirely possible that one will follow and that the water is trapped somewhere on the road down the mountain.

All of this lead the Icelandic authorities to declare a phase of uncertainty for Öraefajökull, and later on they also declared a Yellow alert for all flights in the area.

It is though important to point out that there as of now are no signs of an impending eruption, and that the seismic levels are currently low.

As Andrej Flis churned out his exquisite plots of the seismicity two previous events stood out. It is with perfect hindsight easy to see that two previous intrusions happened. These originated from the main magma chamber and rapidly went upwards. During those two, no new magma seems to have arrived from near MOHO-reservoir. This indicate that the system has been active down through the years, unclear how long.

Conclusion and thoughts

Öraefajökull from air.

It is important to once more state that volcanoes can have large intrusions that does not cause eruptions.

But, as I said in the beginning, this is a volcano that I do not want to see erupt. Because this is as far as we know the most dangerous volcano in Iceland for the local inhabitants. I am though certain that the competent Icelanders can solve the problems with eventual evacuations of both people and animals before an eruption occurs. It would still though be an economic disaster for the country.

The reason for it being so dangerous is that the magma type it erupt is highly prone to be explosive, and we do know that it is full of volatile gases and that it is hotter than usual. This is a bad recipe, nobody likes turbo-charged rhyolite.

The second problem is the lack of knowledge and historical records of how the volcano behave prior to an eruption. The small few things we do know indicates that the current behaviour is how the volcano behaves prior to an eruption, but that there can be decades long waiting time from reactivation to the final eruption.

And due to our technical knowhow, we do not only face a potential disaster stretching 160 or more kilometres in south eastern Iceland, we also risk losing the ability to fly for weeks or even months. Because this would be a very ashy history indeed.

One way to try to comprehend Öraefajökull is to go beyond the scope of Iceland, because it more resembles a large subduction resurging caldera, than the typical Icelandic volcano. Yes, it is not going to super-erupt, but it will produce a similar eruption on a smaller scale with similar characteristics.

I still hope that the volcano will calm down, but if not, I wish all the people in the region the best possible outcome. I know that the Icelandic authorities are the best in a crisis, so they are in good hands. Remember, better to be safe than sorry for eternity.

CARL REHNBERG

Related posts

164 thoughts on “Öraefajökull – A challenge for volcanology”

    • That was definitely not my intent 🙂
      As long as everyone follows the directives of the authorities I am quite convinced that everyone will be safe.
      But, if an eruption would occur the property damages might be severe.

      Bjarki had the gist of it: “Basically, if you are in the area when the danger starts to become real, run fast, yesterday preferably”.

  3. Considering the subject matter,here’s a paper (three chapters) on the flooding dangers of Öræfajökull

    I. Volcanogenic floods in Iceland: An
    exploration of hazards and risks
    http://www.vedur.is/gogn/vefgogn/jokulhlaup/haettumat/oraefajokull_markarfljotsaurar/bok_en/chapter_I.pdf

    II. Öræfajökull volcano: Geology and historical floods http://www.vedur.is/gogn/vefgogn/jokulhlaup/haettumat/oraefajokull_markarfljotsaurar/bok_en/chapter_II.pdf

    III. Öræfajökull volcano: Eruption melting scenarios http://www.vedur.is/gogn/vefgogn/jokulhlaup/haettumat/oraefajokull_markarfljotsaurar/bok_en/chapter_III.pdf

    Basically, if you are in the area when the danger starts to become real, run fast, yesterday preferably

    • Thanks Bjarki – I am sure that the interested reader will find these useful. I didn’t know they were publicly available 🙂

      Magnus Tumi is one of Iceland’s foremost authorities on volcanoes, and has been a key figure in providing expert advice and reassuring the public about most recent eruptions in Iceland (roughly from Gjálp 1996 onwards). His daughter is called Katla by the way….

      Magnus published the paper on ice thicknesses within the caldera, which can be downloaded at http://www.hi.is/~mtg/pdf/2000Jokull48_MTG_Oraefaj_massbalance.pdf

      All good wishes,
      Dave

    • There looks to be a smaller vent now open on the left hand side of the crater that is also now steaming.

      • Every day that we can see the plume it appears to get larger and stronger. Sad that the seismo isn’t working anymore

        • By the way Carl, I really enjoyed reading your article, that volcano has been bugging me since it was mentioned as it has been so quiet in previous years that I hadn’t even realised it was there. Mind you because of poor health it has been a few year since I came here to watch volcanos so perhaps I was missing a lot of what was happening in Iceland.

          • I am sorry to hear about your health problems. I hope that they will sort themselves out soon. 🙂

            Not much has happened in Iceland. We have though been following Öraefajökull for a time behind the scenes, but due to workload the article became 4 weeks late. Ahem…

  5. Frances can you see the new vent on the left hand side I don’t think I have seen this before.

    • Look from 05:57 you can clearly see it start from this time.

      • Janet, I can’t be certain if it is a new vent or just the wind moving the steam sideways but most certainly that plume seems to have a much wider base than a few days ago.

        • It certainly is an impressive plume today, bigger, better, stronger! I really don’t believe all that increase in steaming is down to rainfall alone as the rain has been heavy for weeks now but Agung just keeps puffing more every day. It is getting to be a habit now!

      • Well Janet, from 6:36 I am sure I saw a small plume from close to the spur at the left of the main plume. You could be right about that second plume. Hard to be totally sure as it was small and could possibly even be cloud coming up from behind the mountain but it certainly looked like a separate small plume to me. I so wish we had the other cam back online to see what is happening on the other side of the mountain then we would have more chance to be sure of things and I SO miss the seismo. Hopefully they fix it soon.

  7. Thanks for a fascinating article about Öraefajökull. A few short years ago we were all concentrating on Eyafjallajökull, Katla and Hekla, without hardly a care in the world for the larger volcanoes like Bardabunga and now, Öraefajökull. It’s interesting how things have moved along with the increasing 120 year activity cycle.

    PS – in MS Edge, my posts keep being rejected with “Invalid Security Token”.

    • It is interesting I agree, but Bardarbunga was expected to put in an appearance during the 120 year cycle, since it follows that cycle to a Tee. Öraefajökull is more of a “I do not care about cycles and crap like that, I will erupt out of blue moon when I feel like it”.

      I also have a problem with posting from MS Edge. I have been promised that one of our Tech Magicians will have a look at it later.

  8. Is oraefajokull a stratovolcano or a pyroclastic shield volcano? Most sources that actually categorize it say it is a stratovolcano but it doesnt look very steep when compared to well known stratovolcanoes like those found in subduction zones.

    Ive always thought that the term shield volcano and stratovolcano refered to how steep the cone was, as it didnt take me long to find examples or flat looking low angle volcanoes that werent made mostly of lava and were explosive, as well as steep conical basaltic volcanoes that erupt fluid lava and dont generally erupt violently.

    • It’s a stratovolcano, as in strata – multiple layers of lava, scoria, ash, etc. that can form nice conical peaks, but in Iceland the weathering action soon alters the classic shape.

    • Öraefajökull is a Complex Volcano.
      That is a volcano that features several different traits and does not fit the Strato- or Shield-meme.
      Öraefajökull started its life as a layered basaltic shield volcano, but over time it sprouted forth both strato-volcano features, domes, spines, parasitic cones, fissure rows and so on and soforth, making it almost into the epitome of the term Complex Volcano.

      • Fully agree with Carl on this – Öraefajökull does not fit any classic definition! Ice has played a major role in shaping the volcano and also in controlling the pathways of lavas – especially the more evolves ones (e.g. rhyolites).

        I suspect that the basaltic ‘shield’ forming the basement is the highly eroded remnants of a much older pre-Öraefajökull volcano, as we have unpublished Ar-Ar ages of 2-2.5 Ma from them. The oldest rocks from Öraefajökull itself are sheet-like basalts (subaerial and subglacial) and described in John Stevenson’s 2006 paper. But we don’t have ages for them – though they are normally magnetised. See https://goo.gl/excEdv

        We also have unpublished Ar-Ar ages from the oldest rhyolites exposed, that go back to 200 ka. I really must get round to writing this stuff up sometimes….

        Thanks for an interesting article Carl…!

        Warm regards,
        Dave

        Found in the pending queue for posts which require approval. Sorry – it happens to new or infrequent commenters. Future comments should appear without delay

  9. For those of us who uses Edge instead of Gargle Dome or the other boonfangled surfing platforms that suck our souls…

    Currently there is a problem, and we Edgians get “Invalid security token” as we try to post comments. It has been suggested that it will work better if we post in a InPrivate-window for the time being.

    I have been promised that the more technical minded of our administrators will take a look at it during the day. They normally wrinkle out these things quite swiftly so for the time have patience.

    /Admin

  11. Thanks Carl

    I make it to be the fourth largest active volcano in Europe (by bulk or by height – it gives the same result). Elbruz, Etna, and Beerenberg are larger.

    • Thanks Albert – I think that you are correct, and I have also seen a calculation that puts Bárðarbunga as larger than Öraefajökull. If you add the output from its fissure swarms, then Bárðarbunga has to be larger.

      I believe that it was the legendary Icelandic geologist Sigurdur Thorarinsson who first claimed that Öraefajökull was the second-largest volcano in Europe, in his massive 1958 paper on the Öraefajökull 1362 eruption.

      • Thanks Dave. If the fissure swarms count, other Icelandic volcanoes should also be larger than Öraefajökull as it doesn’t seem to do long-distance ones. If the base area counts, Hofsjokul becomes the clear winner in Iceland. By volume, I wasn’t sure but Bardarbunga is sitting on top of a large bulge and if you discount that stolen height, Öraefajökull should be quite a bit larger. But measuring the volume of a volcano covered by deep ice can’t be easy.

      • I happily admit that I got that from Thorarinsson.
        The bulk of Beerenberg is smaller, even though it is higher. This due to the steeper edifice. Elbrus I am not entirely sure of since I haven’t been studying it up and close.
        Bardarbunga may be of the same size. But it is hard to compare those two due to ice.

        And in answer to Albert, if we counted fissure swarms Bardarbunga would be larger than Etna. I did though not take those into account when I wrote this.

  12. The four step evacuation plan the police is currently working with in case things start to heat up, stuff will be added and more finely tuned as more info comes along from scientists, locals and other authorities

    Step a:
    • Roads leading from highway 1 closed
    • External closures installed
    • Closures will be at Lómagnúp in the west and Jökulsárlón in the east
    • Only residents, scientists, emergency services, transports and other necessary traffic are allowed to enter the area
    • Transfer of livestock prepared

    Level b:
    • All tourists and others who do not need to be in the area should leave it
    • Livestock moved away
    • Block all traffic into the area other than for emergency services and scientists

    Level c:
    • Full evacuation of the area

    Level d:
    • Closures moved west and east with respect to forecasts of ash fall
    • Evacuation area re evaluated with respect to forecasts of ash fall

    http://www.visir.is/g/2017171118713/rymingaraaetlun-utfaerd-med-hjalp-ibua-vid-oraefajokul

    • Giggle translate does a fairly good job of translating.
      Center of Volcanology and Geological Hazard Mitigation again perform the monitoring of Gunung Agung crater using drones. This monitoring is done to find out the gas contained in solfatara smoke, which keeps coming out of the crater of Mount Agung.
      Post downgraded the status of Mount Agung to level 3 or standby, on Saturday (18/11) PVMBG team continues to perform the crater of Mount Agung using drones. This is done to determine the gas contained in solfatara smoke that keeps out of the crater of Mount Agung, using a multi-gas sensor. This gas data which will be evaluated to know the gas substance contained is magmatic or only water vapor. Until now the crater of Mount Agung still smoke smoke solfatara with a height of 300 meters from the crater lip, while the seismicity continues to decline.

  14. Swarm under Öræfajökull seems to be picking up again. A handfull of small quakes (<M1) at the moment.

  15. Has IMO a public drumplot (tromlurit) map yet, please? The old one I have is now all broken links. I can dig and find the individual charts, but it is so much easier to click on a map! Thanks.

  16. Civil protection is now saying flooding can reach humam settlements in 20 minutes.

  17. I would love to know what is going on just west of Maré Island. There are a few under sea volcanoes in that area. Just a continuous swarm of 4 to 7 tremors.

    • Are you talking about Maré Island in New Caledonia or Mare Island in Indonesia?
      Maré Island is not known for any volcanic activity since it is an uplifted coral island.
      Mare Island is on the other hand a holocene volcano located next to Tidore.

      4 to 7 earthquakes sound more like a small tectonic event than a volcanic tremor swarm. Could you please confirm which place you are talking about?

  18. From ruv.is

    A flood from Öræfajökull could reach a human area in a shorter period than it takes to clear the area. Civil protection has prioritized the creation of a new evacuation plan. About two thousand people go around the area every day during the winter season. That number multiplies in the summer.

    The Public Prosecutor’s Department of Civil Protection described the level of uncertainty on Friday due to evidence of increased activity in Öræfajökull. Civil protection has today been preparing a space plan for the area under the glacier, but such a plan does not exist.
    “We thought there was a good reason to put it ahead of other projects we are conducting. A project we were supposed to be able to conduct in the second half of next year, but these changes call for a hurry, “says Reynisson, Project Manager, Civil Protection Project Manager in South Iceland. Among other things, the work aims at creating a plan on how to react if an eruption begins without delay.
    “We want to be prepared for it, although there is no indication that it’s happening, we want a ready plan so we can do something right now.”
    2,000 people a day
    If volcanic eruption begins there, how long can it last until floods down the highway and to the countryside?
    “The best time we can see on these watercourses that can occur when eruption comes from the glacier is 20 minutes and even shorter times at some places on the highway. So time is awesome, awesome shame. ”
    However, it takes more than 20 minutes to clear the area.
    “We are talking about the risk assessment we are working after it can take 40 minutes to clear the largest part of the area if everything goes well. But the changes since the work was done up to today regarding the number of tourists and the other means that we do not have that time. “

    • The archipelago of New Caledonia, which includes Grande Terre, Belep and Île des Pins, was born as a series of folds of the earth’s mantle between the Permian period (299-251 mya) and the Paleogene and Neogene periods (66 – 1.5 m ). This induction of the mantle created large areas of peridotite and a rock rich in nickel.
      The Loyalty Islands, a hundred kilometers to the east, are islands of coral and limestone, built on the old collapsed volcanoes that originated from the subduction of the Vanuatu Ditch.

  21. does anyone, anyone know what is happening in the southern pacific with the 6+’s and 7+ ??
    https://earthquake.usgs.gov/earthquakes/map/#%7B%22autoUpdate%22%3A%5B%22autoUpdate%22%5D%2C%22basemap%22%3A%22grayscale%22%2C%22feed%22%3A%221day_m25%22%2C%22listFormat%22%3A%22default%22%2C%22mapposition%22%3A%5B%5B-30.694611546632277%2C-207.13623046875%5D%2C%5B-10.552621801948709%2C-174.2431640625%5D%5D%2C%22overlays%22%3A%5B%22plates%22%5D%2C%22restrictListToMap%22%3A%5B%22restrictListToMap%22%5D%2C%22search%22%3Anull%2C%22sort%22%3A%22newest%22%2C%22timezone%22%3A%22utc%22%2C%22viewModes%22%3A%5B%22list%22%2C%22map%22%5D%2C%22event%22%3Anull%7D this is a catch from the map of eq’s…

    • Appears to be thrust faulting. From the Magnitude, it appears the average displacement was about 0.66 meters along the fault plane.

      (using Wells-Coppersmith, but they note that reverse slip relationships are not significant within the 95% conf interval.)

      This also occurred along a subduction zone, so the thrust fault quake fits the normal realm of things. This whole region of the globe has a lot of interacting plates, plate shards and jumbled structures. In fact, Fiji had to relocate a village due to one side of the island dropping while the other side rises. Plate shards don’t just rotate on the horizontal axis, some compress and push up mountains.

      • i sent You a Thanks last night but i guess i pushed the wrong keys (happens a lot) and it didn’t appear here…. i’m trying again… Thanks! Best!motsfo

    • I think two large earthquakes, one triggered by the other, and a sequence of aftershocks. The size of the events seems normal for this area

  23. Looking at the drumplots around Oraefajokull, it steadily becomes more noisy… weather related or related to current unrest?

    • I find the relationship between Oraefajokull, the areas A&B and the line marked interesting.

      If you watch the animation maps these areas all seem to become active together until about August of this year. Then, the activity at Oraefajokull shifts more to the east side of the caldera and the other areas remain quiet.

      • I’ve been wondering for a long time, what’s going on at “A”? Is it a geothermal area or something?

  26. Possible glacial flood out of Kverkfjöll? It shows on several drums so must be large

  29. Thank You Ian, that is wonderful, I just wish the Icelanders would find a name and stick with it, all the maps are different and you kinda need to know where things are located to find it, why is the name of a peak more important than the name of a volcano 😀

  32. Help request :
    Some users are reporting issues commenting on the blog when using Microsoft Edge.

    Can we have some other Edge users comment to see if we can isolate the problem.

    Please let me know if you’re successful or not, and copy (screen shot if possible) any error messages.

    If unable to post in here, please visit the Facebook group and comment on my post there, or drop an email to volcanocafeorg@gmail.com.

    Thanks

  33. Taken from fb https://www.facebook.com/Natturuva/ there are more images than the one below, the one below is however the only one with descriptions

    “Radar images from the SENTINEL-1 satellite of ESA. At the end of last month, 27.10.2017, no crevasses were visible in the center of the Öræfajökull caldera. On November 8th quite a few have become visible, and even more this morning, on November 20th. Radar images can be tricky to interpret; they tend to show surface roughness. This selection has not be georeferenced taking landscape into account, but are shown here for preliminary comparison and to study the development.”

    • Wow – Bárðarbunga is certainly not keeping quiet. Being English I had to use Google translate on the article. I had to smile over this line: “The pictures that Björn took on the trip could be considerable geothermal heat in the Bárðarbunga sails. In one of them one sees water in his bottom and from the other one rises up steam.”

      I know what it meant, but I still felt a little sorry for Björn.

      Interesting developments at Bárðarbunga. Thanks for the article, Bjarki!

    • Steam is expected when heat from below is melting snow. It is effectively a snow geyser.

    • If bardarbunga erupted through the cauldron (or cauldrons) that has rock exposed at the bottom of it, would it count as subglacial or subaerial? I would imagine it would probably be not as ashy as it would have been starting under ice. But lava fountains through the ice is something that would be pretty epic.

      It would be interesting if it became a somewhat long lived eruption and became a future table mountain but that might be pushing it.

  36. 20/11/17 23:41 GMT

    Earthquake : Indonésia, A 137 Km De Sinabang

    • Not sure what it is, but on the spectrogram it looks like some higher frequency noise (5-6Hz), so magma seems to be out of the question. But I wouldn’t speculate further without more info.

      • Look at the cams now, looking like smoke and dropping down the mountain not going up as steam would. Saw a couple of the volcanologists go sprinting down the garden to look and heard the drone detected sulphur. Could soon be game on with Agung. Wait and see as always as very little real information coming out yet.

        • No wind so steam would rise not drop at the plume is doing today surely? Would that indicate smoke in the plume?

          • Yes, it is now official, Agung erupting volcanic ash, see below at bottom of page.

      • Something different occurring -https://www.youtube.com/watch?v=Zb_daYtr5TQ&feature=youtu.be&a=

        • Gunung Agung in Karangasem Bali erupted black smoke on 21/11/2017 at 17.35 WITA. Standby Status (level 3). People are encouraged to remain calm. Do not panic. Stay away from a 6-7.5 km radius as recommended by PVMBG.

          • “Don’t panic Mr Mainwaring, Don’t panic!” Fans of UK’s Dad’s Army will understand that joke. 😉
            The priests in their mountain retreat are clearly not panicking, their lights are on as usual. Mind you they did go up the mountain and got incinerated the last eruption in ’63 so I personally wouldn’t follow their example.

  38. Askja is having deeper activity, as IanF has pointed out, and it has it regularly for quite some time. It has had so much intrusions actually, that its feeder system shows up on tomography models as a zone of reduced velocity, from all the molten material in there.

    here is a quick one from my part.

  40. Agung is officially erupting volcanic ash!

    Current Aviation Color Code:
    ORANGE
    Volcanic Activity Summary:
    Eruption with volcanic ash cloud started at 0905 UTC (1705 LT). Eruption and ash emission is continuing.
    Volcanic Cloud Height:
    Best estimate of ash-cloud top is around 12294 FT (3842 M) above sea level, may be higher than what can be observed clearly. Source of height data: ground observer.
    Other Volcanic Cloud Information:
    Ash cloud moving to east – south east.
    Remarks:
    Seismic activity is characterized by volcano tectonic earthquakes.
    VONA Detail :: VONA Archive

  41. Pretty clear small scale eruptive looking black cloud on the cam from about 17.29.50

    • Looks like a phreatic puff, or like a throat clearing puff. The seismos were far from a full blown explodive eruption, and the frequency didnt match (too high).

      • Yes, that seems very clear. Not exactly dramatic.
        Isn’t this in keeping with the activity of the last eruption?

        • Yes my understanding was the 63 eruption took a little while to escalate to the full monty. Think someone posted on here that old magma was extruded first then once that was cleared the eruption got going proper.

          It could however be nothing more than a phreatic event as Andrej has suggested, ground water making its way to somewhere a little too hot? This is of course just hopeful speculation on my part, based on this being a volcano that no one wants to go off big time. Google was showing a headline that it has already cost the Bali economy over £100 million.

          Out of interest, did anyone manage a screen grab of the seismo? I do not appear to be able to access it at the mo.

          • You won’t be surprised to hear that I didn’t.
            In any case, they seem to have subsequently turned down the gain, or in some way filtered the signal. What I saw when I asked for advice was much more unrelenting noise than is normal for the daytime cycle of activity.
            I wouldn’t have described it as Maxed out, but it was well on the way.
            The same time period on the seismo now looks perfectly normal, although the up to the minute reading is showing more constant noise (at a reasonably low level ) than we might expect for this time in the evening.

          • Now have access again. No expert but the current signal noise has to be concerning. Assuming the seismo time stamp and that of the you tube cams are in sync then the noise over the past 30mins is much higher than that when the ash cloud appeared earlier.

    • Agung 20171121/0939Z
      (1) VOLCANO OBSERVATORY NOTICE FOR AVIATION – VONA
      (2) Issued : 20171121/0939Z
      (3) Volcano : Agung (264020)
      (4) Current Aviation Colour Code : ORANGE
      (5) Previous Aviation Colour Code : yellow
      (6) Source : Agung Volcano Observatory
      (7) Notice Number : 2017AGU15
      (8) Volcano Location : S 08 deg 20 min 31 sec E 115 deg 30 min 29 sec
      (9) Area : Bali, Indonesia
      (10) Summit Elevation : 10054 FT (3142 M)
      (11) Volcanic Activity Summary : Eruption with volcanic ash cloud started at 0905 UTC (1705 LT). Eruption and ash emission is continuing.
      (12) Volcanic Cloud Height : Best estimate of ash-cloud top is around 12294 FT (3842 M) above sea level, may be higher than what can be observed clearly. Source of height data: ground observer.
      (13) Other Volcanic Cloud Information : Ash cloud moving to east – south east.
      (14) Remarks : Seismic activity is characterized by volcano tectonic earthquakes.
      (15) Contacts : Ministry of Energy and Mineral Resources
      Geological Agency
      Center for Volcanology and Geological Hazard Mitigation (CVGHM)
      Tel: +62-22-727-2606
      Facsimile: +62-22-720-2761
      Email : vsi@vsi.esdm.go.id, gunungapi@vsi.esdm.go.id
      (16) Next Notice : A new VONA will be issued if conditions change significantly or the colour code is changes.
      Latest Volcanic information is posted at VONA | MAGMA Indonesia Website
      Link : https://magma.vsi.esdm.go.id/vona/
      Agung 20171121/0939Z

        • Those people are surely way too close. If anything bigger happens, they are in trouble.

          • Translation of Pyter’s link:-

            Date: November 21, 2017

            Mount Agung eruption Tuesday, November 21, 2017 at 17.05 WITA

            Mount Agung eruption occurred in Karangasem regency, Bali province at 17:05 WITA. Smoke is observed with medium pressure with a thick gray color and with a maximum height of about 700 m above the peak. The blasting ash blows weakly towards the East-Southeast.

            The eruption is still ongoing. Communities remain calm, but always follow the recommendations of the Center for Volcanology and Geological Hazard Mitigation (PVMBG), Geological Agency, Ministry of Energy and Mineral Resources (ESDM) in Level III Status (Siaga).

            Recommendation:

            Communities around Gunung Agung and climbers / visitors / tourists not to be on, do not climb and do not do any activity in the Estimate Zone of danger in the area of ​​the crater of Mount Agung and in all areas within a radius of 6 km from the summit crater of Mount Agung and added sectoral expansion to North-Northeast and Southeast-South-Southwest as far as 7.5 km.

            Estimated Zone The dangers are dynamic and continuously evaluated and can be changed at any time following the most recent / latest Gunung Agung observation data. Areas affected include Br. Br. Belong, Pucang, and Pengalusan (Desa Ban); Dusun Br. Badeg Kelodan, Central Badeg, Badegdukuh, Telunbuana, Pura, Over and Sogra (Sebudi Village); Dusun Br. Kesimpar, Kidulingkreteg, Putung, Temukus, Besakih and Jugul (Besakih Village); Dusun Br. Bukitpaon and Tanaharon (Desa Buana Giri); Dusun Br. Yehkori, Untalan, Galih and Pesagi (Jungutan Village); and some areas of Dukuh Village.

            If the eruption occurs then another potential danger that can occur is the occurrence of heavy ash rain that hit the entire Estimated Danger Zone. Heavy ash rain may also extend its impact beyond the Estimated Danger Zone depending on the direction and speed of the wind. By the time this recommendation is lowered, the wind blows predominantly towards the South-Southeast. Therefore, it is expected that this can be anticipated early especially in determining the location of the refugees.

            Given the potential dangers of volcanic ash that can cause acute respiratory distress (ISPA) in humans it is expected that all communities, primarily living around Mount Agung and on the island of Bali, immediately prepare masks cover the nose and mouth and eye protection in an effort to anticipate the potential danger of ash volcanic.

            Local Government and its staffs as well as BNPB to immediately assist in establishing the communication network via cellular phone (WhatsApp Group) as well as integrated radio communication to overcome the limitations of cell phone signal among the parties related to Mount Agung eruption disaster mitigation. It is expected that a routine and fast information dissemination process can be well organized.

            All stakeholders in the aviation sector continue to follow the progress of Gunung Agung’s activities on a regular basis as observational data can be rapidly changing so that preventive measures to ensure air safety can be done.

            All parties to maintain the atmosphere atmosphere on the island of Bali, do not spread false news (hoax) and not hooked issues about the eruption of G. Agung is not clear source.

            PVMBG, Geological Agency, Ministry of ESDM continue to coordinate with Local Government, BNPB, BPBD Bali Province and BPBD Kabupaten Karangasem in giving information about activity of Gunung Agung.

            Communities around Gunung Agung and climbers / visitors / tourists are expected to remain calm while maintaining vigilance and following the appeal of Local Government, District / City Government, Provincial / District / City BPBD and other related apparatus in accordance with recommendations issued by the Center for Volcanology and Geological Disaster Mitigation, Geological Agency, so that if rapid strategic mitigation efforts are needed, it can be done immediately and without waiting for a long time.

            All communities and local governments, BNPB, BPBD Bali Province, BPBD Kabupaten Karangasem, and other relevant agencies can monitor the development of activity levels and recommendations of Mount Agung at any time through the application MAGMA Indonesia which can be accessed through the website https: //magma.vsi.esdm. go.id or through the Android MAGMA Indonesia app that can be downloaded on Google Play. Community participation is also highly expected by reporting events related to the activities of Gunung Agung through the Disaster Report feature.

            I like the ‘if rapid strategic mitigation efforts are needed, it can be done immediately.’ I would be out of there fast already.

  43. Agung, tremor appears to be increasing a little, let’s hope it gives people time to get out after this initial small eruption. I would leave, but then being a devout coward I would never have gone back.

      • You’re right about the noise picking up. There’s no doubting it now. This is something we haven’t seen previously on that seismo.

        • It is good in a sense that it has happened when they aren’t working at the sand mining as at least it is clear what is happening.

        • Oh dear! A BIG chug on the seismo now. Please let those people get out before anything bad happens. Still I will just trust the the emergency services will be well into emergency mode by now. Let’s hope they aren’t needed!

  44. Looking at the seismo, it got a gain correction. The orange areas are likely human activities, some heavy machinery I think it was said. There was a lunch break in between. The high frequency also agrees with it.

    The red area tho, is something else and likely caused by Agung.

    • Hi Andrew, look at it at 20:10-ish it is looking like magma moving for sure in my view.

        • definitely volcanic tremor now. Doesn’t that usually precede the main phase?

          • Someone who lives there, I don’t know how close but in Bali, is reporting feeling constant small tremor.

          • Actually able to feel the tremor! That is not something that inspires confidence moving forward.

          • @Swebby, it appears one person is 30km away and the other 80km. Both feeling tremors, obviously the one at 80 km describes it as less but almost like a wave passing through. The one at 30km said that the frogs that usually make a tremendous racket after sunset were quiet that evening.

  45. Hi Andrew, llook at it from 20:10-ish starting to look like magma moving up in my view.

  48. Can the experts pipe in on what seems to be winding up at Agung? We had tremor and ash for a couple hours. I has stopped now. Does that likely mean it is done given that the tectonic activity has been dying down the last month or does it mean that the bigboomboom is now a real threat?

    I have read that episodes like this can lead to explosive depressurization. Am I misreading things? Just curious as to what people who have seen things like this before think.

    • Volcanologists are elves, not dragons…. And you know what that means ?
      “Go not to the elves for counsel, for they will say both no and yes ”

      Now tell me I’m wrong 😀

    • Sutopo Purwo Nugroho
      @Sutopo_BNPB
         1 minhá 1 minuto
      Mount Agung erupts phreatic. Phreatic eruption can occur in all volcanoes above normal status. Phreatic eruption is difficult to predict. Eruption with ash, sand and gravel.

      • Bali condition is safe. Ngurah Rai International Airport is normal. Tourism is safe except the dangerous radius in a radius of 6-7.5 km from the summit of Mount Agung. Pascaletusan phreatic condition is still normal. There is no increase in seismic spikes.

        • The last sentence of that BNPB statement seems odd given that we have had two hours of what appears to be continuous tremor?

          Seems they are settling on this being a phreatic event and i have to say that they have had a lot of rain over the past week so maybe a chage in water table has caused this. However, the tremor signal only started some time after the appearance of the ash cloud. Gas/Sulphur emissions would be informative at this point.

          • I have heard that the local people that got the ash were also saying they could strongly smell sulphur. I also thought that last sentence odd!

    • You can see the phreatic eruption on the seismo plot. It looks like there were two events a few minutes apart. Regarding the tremor, if you see such a plot a few hours after a phreatic eruption, it does sound like a warning that there could be more to come. But let’s see what happens over the next few hours. It seems to have gone to sleep again.

  50. Big quake on Bardarbunga but still low quality…

    Tuesday
    21.11.2017 13:53:04 64.690 -17.350 1.1 km 3.8 50.5 10.1 km ENE of Bárðarbunga

    • Tuesday
      21.11.2017 13:55:33 64.681 -17.444 3.1 km 3.0 99.0 6.1 km NE of Bárðarbunga
      Tuesday
      21.11.2017 13:53:04 64.703 -17.444 4.6 km 3.0 99.0 8.0 km NNE of Bárðarbunga

    • One of the stars I think outside the caldera plugg. Not plugg adjustment? New dyke?

      • Yes, it does look like it’s outside of the main ring fault, though I haven’t really checked if that’s the case. Could be a radial fault or a concentric fault. These could of course form dykes, but I would suspect that dyke formation is a lot noisier with many small quakes. This looks tectonic to me.

Comments are closed.