Eldgja: Feeding the Fire

Eldfell, the fire mountain, overflowing  Vestmannaeyjar town in 1973. Photo/Valdís Óskarsdóttir/Reykjavik Museum of Photography

Eldfell, the fire mountain, overflowing Vestmannaeyjar town in 1973. Photo/Valdís Óskarsdóttir/Reykjavik Museum of Photography

The facts of Eldgja are well established. We know approximately when it happened, where it happened, how much lava, tephra and sulphate was ejected. We have found the tephra in Greenland. We think we know the human impact over much of the northern world, arising from three years of winter. But on other aspects, our understanding is on thinner ice. We don’t know anything about the human impact in Iceland itself. We don’t know what caused the fire, or why it erupted as much as it did (and no more). We don’t know which volcanoes can feed such a fire. And we don’t know when the next one will be.

Let’s first clear up a separate confusion. If we accept shifting the Neem and NGRIP ice cores by 5 years, there is no longer any sulphate peak at 934 AD. The evidence for a long-lasting event came from the need to reconcile the 934 and 939 peaks, seen in different ice cores. Now there is only one peak, lasting 2-3 years, securely linked to Eldgja by the tephra in it. But this is not the full story. The NGRIP core still shows a second, weaker sulphate peak, some years after the main one. In the original dates, this second one approximately lined up with the later peak of the GISP2 core. In the new dates, it doesn’t. So by solving the Eldgja problem, we have created a new, later eruption. What was this?

Sulphur in Greenland ice cores. Data from Sigl et al. 2016.  Plotted is the total sulphur, in parts per billion, excluding that coming from sea salt. The assigned dates assume the revised time line.  For the old time line, subtract 5 years.

Sulphur in Greenland ice cores. Data from Sigl et al. 2015. Plotted is the total sulphur, in parts per billion, excluding that coming from sea salt. The assigned dates assume the revised time line. For the old time line, subtract 5 years.

The VEI7 that wasn’t

The two sulphate peaks in the ice core record are separated by about 7 years. In the revised chronology, the second, weaker sulphate peak occurs around 945 AD. Could this have been a final flourish of Eldgja? It turns out that this is not the case. The ash from the first peak has been securely identified with Eldgja. But the ash in the second peak, found both in the NEEM and NGRIP cores, is different. In particular, it has a higher iron content relative to calcium than found in Iceland. A paper by Sun et al. in 2013 showed that the composition of these fragments was a close match to Changbaishan volcano (also known as Baitoushan or Paektu), on the border between North Korea and China.

Changbaishan has a crater lake called ‘Tianchi’. The name means ‘heavenly lake’, and it is the source of three different rivers. But its formation was far from heavenly, unless from a very upset heavenly creature. The lake formed in a massive eruption, a VEI 7, about a thousand year ago. (The North Korean nuclear test explosions are done very close to this inflating volcano. Military stupidity knows no end.) The VEI 7 classification makes it one of the largest events of the millennium – I have seen it listed as among the 10 worst eruptions of recent history. It is sometimes called the millennium eruption, not because of its size or age, but because some estimates have dated it to 1000 AD.

Amazingly, for such a major eruption in a highly developed and literate region, there are no written records of it. In this, it is just like Eldgja. There are indirect mentions. In Kyoto, an explosion (thunders like a drum) was heard in February 947, and white ash fell in Nara, Japan on 3 Nov 946. In Korea’s capital Kaesong, drum-like thunder was heard in 946. The 14C dating has not given a unambiguous date, but the best determinations also put the eruption around 946, within a few years. The identification of its ash from Greenland now confirms this date, and the second sulphate peak can be identified not with Iceland, but with Changbaishan, a continent away.

Changbai mountain, after the milliennium eruption

Changbai mountain, after the milliennium eruption

It is a funny coincidence that there were two major eruptions from entirely different volcanoes, separated by about the same amount of time as the uncertainty in the dating of the ice cores. Science can be difficult. (For some reason, major eruptions more often happen 7 years apart: volcanoes do a 7-year itch. This happened in the double event of 540, the double event of 1453/1495, and the two big bangs of 1809 and 1815. Coincidence is like the lottery: funny things happen.)

But if Changbaishan occurred in 946/947, why was there no volcanic winter after this? A VEI 7 is massive and all known VEI-7 eruptions have had major effects. It turns out this eruption may have suffered from a numerical error. A VEI 7 eruption is defined as more than 100km3 ejecta. Changbaishan indeed erupted 100-120 km3 in tephra, but the DRE value is much less, 30 to 48 km3 – making it a ‘run of the mill’ VEI 6. The relatively small caldera, 5 km wide, agrees with this assessment. It was big, but not world shattering. That “Tianchi” was a VEI 7 appears volcanological fiction.

The sulphate deposition in Greenland from Changbaishan’s millennium eruption was much less than that of Tambora, and even less than Krakatoa. Those two eruptions were tropical and a northern eruption such as Changbaishan should deposit more sulphate in Greenland, not less. Oppenheimer lists it as ‘only’ M6.8 (about a third smaller than the smallest VEI-7), but even that may be a high estimate. It was a significant eruption: downwind in Japan the ash layer was 10 cm thick. But Changbaishan was too small for major climatic consequences.

This is no excuse for making it the only volcano in the world subject to experimental nuclear detonations!

Feeding the fire

After this Korean diversion, let’s get back to Iceland. There have been four major ‘fires’ in Iceland since the ice age, all four in the East Volcanic Zone. Two were in historic times: Laki and Eldgja. The third was around 8000 yr ago, the Holmsa fire, with a volume of at least 5 km3. Its lava is mostly buried making it hard to accurately measure the volume. Holmsa occurred on the same NE trend where Eldgja also erupted, but the exact source region has not been found and may have been covered by Eldgja lava. The fourth, and largest, was the Thorsja lava flow, 8600 yr ago, estimated at 22 km3. The Thorsja fissure is to the north of Eldgja.

The Thorsja lava flow. Source:  Árni Hjartarson (wikimedia)

The Thorsja lava flow. Source: Árni Hjartarson (wikimedia)

The fact that each of the fires here comes from a different rift shows that the EVZ is a wide, weak zone which can break in numerous places. It is pulled apart, breaks, stitches the break with solidifying magma (the ultimate poly filler), and breaks somewhere else. It doesn’t offer much resistance! Half of all lava erupted in Iceland since 900 has come from here. And this is in spite of the EVZ not having any major volcanoes itself. It is a conduit for volcanoes located elsewhere, and is being fed from its edges: Holmsa and Eldgja came from Katla, Laki came from Grimsvotn, and Thorsja came from Bardarbunga. Each of these three major volcanoes produced one (at least) massive fire in the EVZ. Iceland is truly a land of equal opportunities.

Why doesn’t the EVZ have a big volcano of its own? Perhaps it is too weak to hold down a big enough magma chamber. That it lacks a big magma chamber is shown by the topography: the area is much lower than the raised peaks of Mýrdalsjökull (Katla) and Vatnajökull (Bardarbunga/Grimsvotn). Hot magma has lower density than the surrounding rock, and therefore lifts up the land above it. Just by looking at the topography you can already get an idea where the magma chambers are. (This only works well for liquid rock: solid rock can be out of equilibrium. But it works well for magma.) Gravity reveals what’s hidden below, and it shows that although the EVZ may not be devoid of hot magma, it lacks huge reservoirs.

A matter of gravity

It is an interesting fact that each of these three main eruptions along this rift zone produced similar amounts of lava. Effusive eruptions are fed by a pressurised magma chamber. In the case of Holuhraun, the main force pushing magma to the distant exit was gravity: the exit point was a kilometer lower than the top of the mountain, and the weight of the mountain pushed it out. Could this be true for the three main fires as well?

Let’s estimate the pressure on the magma chambers from the weight of the mountain. The magma chambers are typically 10 by 10 km, with a surface area of 100 km2. The magma chamber carries the weight of the mountain above; the rift next door has no mountain on top of it and carries much less weight. The magma chamber is therefore over-pressurised with respect to the rift: if it can connect to the rift, the magma will flow towards it, just like the communicating vessels from school physics lessons. This is true even if the leak is much deeper than the rift.

The top of the mountain is about 1 km above the rift. The total volume which gives the excess weight is the surface area of the chamber, multiplied by this height, which becomes 100 km3. This is the most magma that can be pushed out by the mountain. In the case of Holuhraun, perhaps a quarter to a third of the magma coming out of Bardarbunga ended up on the surface: the rest was used to fill up the rift. If the same ratio holds for these very large fires, the most that they can erupt becomes about 30km3. The numbers make sense. Eldgja was not far off the largest fissure eruption Iceland can support.

Mýrdalsjökull ice-free topography:  a view from the North East. Helgi Björnsson  University of Iceland

Mýrdalsjökull ice-free topography: a view from the North East. Helgi Björnsson University of Iceland

Katla’s caldera is about 140 km2 large and 750 m deep. This gives a volume of 100 km3 (a bit overestimated), consistent with the numbers above. The bottom of the caldera is at about the same height as the Eldgja rift, perhaps not accidentally. Bardarbunga’s caldera covers 80 km2 in area and is 700 m deep: it has a volume of 56 km3. The bottom is at 1100 m, which is a bit higher than its fissure eruption but the caldera may have recovered a bit since its fire. Grimsvotn’s caldera is a bit smaller, at 50 km2. I have not found a value for its volume, but the smaller area would be consistent with the fact that Laki was a smaller eruption than Eldgja or Thorsja. The numbers hold up: it is conceivable that the Icelandic fires are gravity fed.

This implies that these three calderas may have formed in their respective fires. Grimsvotn’s caldera in particular would be very recent, and is the missing hole left from feeding Laki.

Caveats Two disclaimers are needed. First, the fires are not the only way Iceland can form calderas. Individual volcanoes can also have large explosive eruptions, which are pressure driven and can eject vast amounts. But in recent centuries, the major fires have been dominant and the current calderas would be due to the fires. Calderas can form suddenly, but can also disappear rapidly, within centuries, as the magma chamber refills.

The second disclaimer (speculation alert) is on the maximum eruption size. By keeping the rift narrow, it is possible to use less magma to fill the rift so that more is available to be erupted. That could double or triple the erupted volume, from the same amount of magma. But it wouldn’t be a fire: because of the narrower rift (or dyke) it would erupt at a lower eruption rate, effusive but without the flow volume needed to maintain the enormous fountains over an extended fissure. The lower eruption rate would tend to build a shield volcano, slower to grow but potentially reaching a large volume. The EVZ notably lacks shield volcanoes.

Katla’s state of the nation


Katla has a long history of eruptions. Over the past 8400 year, it has erupted 350-400 times, about four times per century. The large majority were explosive: only about 10 effusive eruptions have been identified, and 8 of these were minor. Eruption rates were high between 2000 and 4000 yr ago (when the two largest explosive Katla eruptions occurred), and between 7000 and 8000 yr ago. The modern rate is only half of the average: Katla has gone a bit quiet (this should not be overstated: it is a bit like a teenager with ADHD having a better day.) This better day may have started after Eldgja.

It is worth noting that Katla had a significant eruption around 920, 15-20 yr before Eldgja. There was no quiet period before the fire. Katla ‘fired’ without needing time for any extensive preparations. The eruption came from its normal supply of magma, without the ominous silence that other volcanoes use to signal danger ahead. It happily continues to erupt in its usual regular irregularity, and suddenly wipes out Iceland. It is as predictable as that North Korean – the one trying to detonate a volcano the nuclear way.

Katla’s eruptions invariably melt vast amounts of ice, which comes out as large floods. The jokulhlaups carry several times more sediment than the eruption ejects! Large ones occur twice a century but small ones, caused by geothermal melting, happen every year. Before Eldgja, the jokulhlaups emerged in various, unpredictable directions, but afterwards they have only appeared from the eastern glacier. Something has changed at Katla. The Eldgja rift may provide a channel for the melt water, breaching the caldera, and that still rules the floods.

The reduced eruption rate and the cavernous caldera suggests that Katla is still recovering from Eldgja. It is unlikely to put in an Eldgja repeat performance any time soon.

As I write this, Katla is responding by shaking its insides, clearly protesting against this assessment. Everything Katla does is pre-eruptive, because Katla erupts so often and by definition is always in an pre-eruption state. Even the summer snow melt is pre-eruptive activity. Even a butterfly settling down could set it off. It is the angry young man of volcano-world. If these are Katla’s quiet years, imagine what it was like in the times when it erupted twice as often. But the chance of the current shaking leading up to an Eldgja-II is somewhere between slim and zero. It isn’t yet ready.

Back to the future

Icelantis By Tjeerd Royaards

Icelantis By Tjeerd Royaards

There are two remaining questions. Why, when the smaller Laki eruption was so devastating, do we not have historical records of the Eldgja disaster, and second, when will it re-occur?

The first question can only be answered with speculation. It is hard to believe that Eldgja would not have badly affected the Icelandic population. The region most affected, in the south, may have been thinly populated (although the Book of Settlement claims otherwise), or largely illiterate. Similar to Laki, agriculture in large areas of Iceland would have been hard hit and the population declined, although perhaps the food supply was more reliant on the sea than on produce from the land. Eldgja began just after the official end of the 60 year of settlement. Perhaps this period ended because Eldgja had made further immigration unattractive. The lack of written records could be directly due to the economic and human damage. But it really is an unanswered, and important question.

As to the future, we have been very unlucky to have two of the three major fires happen during the brief time Iceland has been occupied. It was bad karma. On average, they have happened only once every 3000 years. There is only a 3% chance of a Laki within the next century. No worries. Unless, that is, if the last 1200 year are the new normal.

Looking deeper, the three main source volcanoes for the EVZ may not yet be able to repeat their performance. The calderas are still too deep for gravity to act its full power. Of course an area offset from the existing caldera could act up, but eruptions do tend to come from the existing calderas, either directly (Grimsvotn) or indirectly by feeding a fissure (Bardarbunga). But there is one question mark. Because this area of Iceland does not have three major volcanoes, it has four. And the fourth is quietly biding her time.

Hekla is the one volcano in the region which could feed a major fire. Will it? Probably not. She may have a fiery temper, she does not have a fiery habit. But do be wary of the Lady.

Olaus Magnus Historia om de nordiska folken. 1555.

Olaus Magnus Historia om de nordiska folken. 1555.

Eldgja: The End

The search for Eldgja has been a fascinating experience. So little is known, and what is there is scattered over the literature. Pulling it together revealed the holes in our understanding, and isn’t that what research is all about? But a better understanding is important. What Iceland did once it could do again. What Iceland did twice it will do again. Two of the six worst volcanic affairs over the past 1200 years have come from Iceland. To be prepared, we need to know what happened. The next step in the Eldgja saga should be to solve the dating problem: with a precise date we can look for its impacts around the northern hemisphere. And finally, archaeology of affected Viking sites would tell us how it changed their world. It could change ours.

Albert Zijlstra, September 2016


T. Thordarson G. Larsen: Volcanism in Iceland in historical time: Volcano types, eruption styles and eruptive history. Journal of Geodynamics 43 (2007) 118–152

Book of Settlement

Ash from Changbaishan Millennium eruption recorded in Greenland ice: Implications for determining the eruption’s timing and impact. Chunqing Sun et al. Geophysical Research Letters, 41(2), 694-701. http://pure.qub.ac.uk/portal/files/13968752/Sun_et_al._2014.pdf

M. G. L. Baillie and J. McAneney: Tree ring effects and ice core acidities clarify the volcanic record of the first millennium. Clim. Past, 11, 105–114, 2015. http://www.clim-past.net/11/105/2015/cp-11-105-2015.pdf

Michael Sigl et al. A new bipolar ice core record of volcanism from WAIS Divide and NEEM and implications for climate forcing of the last 2000 years. Journal of Geophysical Research: Atmospheres, 118, 1151–1169, 2013

Michael Sigl et al. Timing and climate forcing of volcanic eruptions for the past 2,500 years.  Nature, 523,543–549 2015

Gregory Zielinski et al., Evidence of the Eldgjá (Iceland) eruption in the GISP2 Greenland ice core: relationship to eruption processes and climatic conditions in the tenth century. The Holocene, 5, pp 129-145 (1995) D. McCarthy & A. Been: An evaluation of astronomical observations on the Irish Annals. Vistas in Astronomy Vol. 41, No. 1, pp. 117-138, 1997

Magdalena Schmid et al. Tephra isochrons and chronologies of colonisation. Quaternary Geochronology (2016) T. Thordarson et al. New estimates of sulfur degassing and atmospheric mass-loading by the 934 AD Eldgjá eruption, Iceland. Journal of Volcanology and Geothermal Research, 108, 33–54 (2001).

T. Thordarson et al. New estimates of sulfur degassing and atmospheric mass-loading by the 934 AD Eldgjá eruption, Iceland. Journal of Volcanology and Geothermal Research, 108, 33–54 (2001).

319 thoughts on “Eldgja: Feeding the Fire

    • Glad I’m not stationed in Mayport any more. That would have entailed a frantic drive to Pensacola to get the wife away from there and then back to get on the ship to get underway. It’s not a hard drive, just a real pain in the arse. Used to do it twice a month. The hard part is the segment from Marianna to Jacksonville. Lots of nothing after you clear Talahassee.

      Dunno what sort of surge this thing is pushing, but don’t think downtown Jacksonville is collocated with a sewage treatment plant. Pensacola didn’t fare to well after Ivan. Downtown Pensacola reeked of feces and fish for three months.

    • I’ve got family down their. I hope they will stay safe. You and your family too Geo.
      PS I love potatoes too. We used to grow them. Always joked how big they were. Texas sized. 😀

    • Sorry – not trying to duplicate Luisport’s announcement earlier. The story in this rag made me laugh.

      • reminds me of our time “Bob watching” and the ensuing pantomime! “There is no eruption! It’s quite safe to sail and swim”

    • Not taking sides here, I have no dog in this hunt, but of all the systems in the Canaries, Teide is the one with a history of throwing up every now and then.

  1. My thoughts are with you Lurking and to all on the coast of Southern USA & Cuba too now. Stay safe my friend and all your family too.

    • There is a stalled front just off the coast of Florida’s east coast. Once it tangles with that it will start it’s transition to extra tropical and head off towards the Icelandic low. While it’s doing that, the east coast will be pummeled. Very rarely are they able to punch through to the back side of a front. (If it’s even possible). As long as it stays out of the gulf of Mexico I have no worries about it

      • That’s good Lurking. I am taking my bean poles down soon because we tend to get the remnants of hurricanes on their way to Iceland. These are commonly called “Autumn Gales” and are a feature of the UK weather that tells us, when they stop, winter has arrived and frosts and snow is allowed to come in from the North and continental East.

        • We in the Pacific NW of the Us tend to get Typhoon remnants this time
          of year, too very similar to the UK.. Had an old friend pass this summer.
          he was from Surrey when he moved to the US due to his Job, he couldn’t wait to get American West.-He ended up in Seattle, working for Boeing.
          “The place is like Surrey only colder and wetter.”
          He moved to Eastern Oregon and the High Lonesome, when he retired…

      • And the opportunistic parasites are out. There was a news report of $15 bottled water in Jupiter Florida. The funny bit is that they did that after the gov announced a state of emergency. That means that ultra heavy fines and penalties can be applied. The state attorney general and her army of lawyers are out actively researching and assembling lawsuits. Florida takes a dim view of price gouging. Doing that price hike after the state of emerg declaration puts them in a very bad legal situation. I’m also p[retty sure that DBPR is gonna be looking around for unlicensed contractor activity, those scum tend to flock to damaged areas and bilk people out of thousands of dollars. The cool bit about Florida, is that we have been hit so many times by storms, that the legal system is well prepared to deal with these criminals. We also have a state wide prison and work camp system that is more than happy to accommodate them.

        Also on the news, a couple of gas stations are out of gasoline. This will also be looked at by state legal to make sure the owner is not just hording it for himself and freinds. We had a couple of gas stations here in pensacola disappear for legal reasons when they pulled that stunt after Ivan in 2004.

        The messed up bit about Mathew, is that the projected track appears as if it’s gonna stay in close proximity to the Gulf Stream. That’s lifes blood for a tropical storm and keeps it supplied with convective energy. Years ago, Hurricane Hugo(1989) was a faltering system until it got to the Gulf Stream… then it ramped up in power and nailed South Carolina. Likewise, 1969’s Camille rode on top of an eddy of warm Caribbean water strengthening all the way until it hit the Mississippi coast.

        Caveat: I’m not making any predictions. This storm (Mathew) could just as well become entangled by a weak stationary front that is parked right along that path and transistion to extra-tropical. That won’t necessarily make it any less dangerous, it would just change the structural dynamics of how it uses energy. To see the CMC model of how it functions, see this. (Shows the expected transition from warm-core low to cold-core low.)

  2. What a fascinating read Albert. I have noticed the dyke that runs from Bardarbunga towards Askja. At one point we wondered if there would be an outflow of magma along that track. There is still restlessness there. Your theory makes sense to me. It may also answer the question of “Where did all the water go?” There maybe no large subglacial lake because the water follows the lines of older and deep “Lava Tubes” that run down and away from the main calderas. Does some of this heated water emerge along the dead zone where there is a big Hydro-electric power station? It’s 2.30 am and not my best time for sensible thinking but Reading this has not been conducive to resting my brain cells. Only one question arises from anxiety. Has anyone suggested what effect a nuclear explosion may have on an active volcanic area? Logic tells me resultant ground shaking could upset a filled magma chamber but then I am not an expert or a doom monger ,I am just an aging hippy who is very anti nuclear testing anywhere. Peace and Love to all….It’s time to try to get back to sleep. Thanks again Albert . A lovely trilogy. We are so lucky to have you and so many excellent writers in VC. Your time and effort is really appreciated.

    • Could the Dyke running from Akja north Eastward also be a source of a fire do you think? Could Baardy be linked to Askja and beyond to this dyke? Eventually could a major movement from the rift open it or part of it up.

      • I think on the these lines Diana:
        – In 1875 a major rifting event happened in Askja and north all the way to almost Krafla. This was a major fissure and rifting event.

        Also it was the major caldera event in Askja for probably a few thousand years.

        Naturally we should expect to see all kinds of reorganization in decades following this, in the north volcanic zone, which runs from Bardarbunga towards Tjornes.

        I noticed that eventually Krafla rifting events could be part of it. And Holuhraun too.

        Herdubreid region, northeast of Askja might be also responding to this. I heard from an IMO expert that the region there is a fragment of a transform zone, so we can expect many earthquakes always but eruptions are scarse and little there. So I dont expect a ´fire´ there.

    • PS ignore my comment about power plants. 2.00 am is not the best time to ponder and the power plant I was thinking about is NOT Geothermal (at least I don’t think it is)

  3. Have you ever wondered how the people of Iceland managed to keep warm in this cold country, I found a video which explains things, enjoy.

    • In The Netherlands these houses are called plaggenhutten. They were very common around Emmen in south east Drenthe when peatland was exploited for fuel.

    • Here is a picture of a Western Kansas sod house.:

      Near my mom’s family cattle ranch. Mom’s family built them when they moved west
      and homesteaded that part (NW) Kansas..

  4. Wednesday
    05.10.2016 08:22:39 64.677 -17.451 3.3 km 3.7 99.0 5.5 km NE of Bárðarbunga

  5. Another one…
    05.10.2016 08:29:49 64.684 -17.386 0.1 km 3.0 99.0 8.3 km NE of Bárðarbunga

  6. And for the fun in Florida. Evacuations are in place for some regions there. You can watch the traffic festivities here. Zones D, L, and E are where people are leaving from. Zone E is the one that is the worst. (southern tip)


    I keep harping back to Ivan, this is because it was the worst that I’ve had to endure. The main highways tend to turn into parking lots. About a year after Ivan, I opted to voluntarily evacutate for a different storm. I didn’t clear traffic until I got well north of Montgomery Alabama. The only reason I was able to make it to I-65 is that I knew the backways out of here. Though backroads are less traveled, they have their own dangers and should you have trouble, you’re pretty much stuck where ever you are at.

    • Oh, and despite my reputation for not making predictions, I will make one single prediction about Mathew.

      Someone will die trying to surf in it.
      → It’s almost a universal constant. ←

      • Yes, probably, I’m sorry to say.
        But that also needs some qualification. There are people out there who have the skills and the knowledge to surf major storm surges and ride huge waves. Surfing is one of those pastimes where responsibility for an individual’s safety has to reside solely with the individual. I know this every time I get in the water.
        Every time we have a major storm here in the UK I see some article reporting that some people actually paddled out and surfed. And I read comments from readers about how irresponsible they are. Well in some cases that is true, but in general the only people with the cojones to go out in extreme conditions are those who know they can handle it.
        I have heard more than once on my home wave (The Severn Bore) onlookers saying things like “How irresponsible… Think of the risk they might put the rescue services in !”
        Actually, in that case, the rescue services phone us… because we ARE the experts who know where boats can safely pass through the sandbars, where the currents will take a board and rider and so on. And we became the experts by doing exactly this thing.
        Quite often, the people seen attempting to surf in extreme conditions are lifeguards and experts… and that is how they became experts.
        If they’re not up to the mark, Darwinian principles will soon sort them out.

  7. Been following the blog ever since the Holhuraun event. I’m just a chemist from
    Norway and have no knowledge about volcanology (exept from what I have learned from you guys).
    So after the last unrest of Katla I started checking vedur.is again occasionally and after the 3.7 and 3.0 wednesday morning the whole of Iceland has been almost eerily quiet. I’m used to seeing background of 1-2 quakes all the time. Is quiet periods like we’re seeing now a common thing in Iceland?

    • Iceland waves up and down, every few weeks, in periods with major seismic activity and then almost no activity. It´s normal. Quietness always leads to seismic unrest eventually, because that needs to be released.

    • Irpsit is correct: part of this is just statistical fluctuations. The human is very good at picking out patterns (it is a survival thing), but can see patterns in random fluctuations. But the weather may also play a role. In windy weather, it is harder to detect faint rumbles. With the caveat that I don;t know the current weather situation in Iceland, apart from windy wet and cold being more likely than the opposite. (Saying that, Greenland seems to have had a record breaking summer)

  8. News twit just reported central pressure down yo 954 mb. Thats not a good thing. That ramps up what the wide speed can get to.

  9. And we have a 3,2 at Katla, again, same shallow depth as past weeks swarm.

  10. … and just as you think you have a handle on what it’s doing, you get conflicting indications. Another news twit just reported that the cloud tops have warmed a bit. That’s an indicator of decreasing convective strength. How that fits with decreased pressure is difficult to understand. It could be that the stalled front that it’s headed into is having some effect and causing some dficulty with the systems structure. (A good thing).

    All I really know from watching these things all the time, is that those two phenomena don’t go together. Something funky is happening to the storm and the question us can it deal with it and power along, or will it be a gut shot and adversely hurt the storm? Once you get up into this power range, the storms usually dictate their own local environment. Time will tell.

    • I think Florida must be careful with this hurricane.
      It reminds me two weeks before Katrina, when the hurricane already dangerous by then, was on route to New Orleans.

      I think Matthew will intensity once it gets past Cuba, and could reach intensity 4 or 5 as it hits Florida coast, and it could even result in a direct hit to Miami.

    • “All I really know from watching these things all the time, is that those two phenomena don’t go together. Something funky is happening to the storm … … …” Pitching a new disaster film to SyFy Lurking? I’d watch it 🙂

      And very much looking forward to watching this latest film, Earthtastrophe: ‘Disaster strikes and civilisation as we know it collapses when Earth is sucked through a wormhole and the planet is turned INSIDE OUT.’

      Must admit, these type of films are my guilty pleasure. The more bad science and cliched characters / plot lines the better. Heh, somethings got to fill the void left by the cessation of the volcano riddles that used to entertain me when getting home from the pub on a Friday evening 😉

      Stay safe Lurking!

      • My comment feels callous given the unfolding tragedy in Haiti and to others affected by the hurricane. An edit by an admin would be welcomed if possible. Thanks

        • I understand your feelings but re-reading the comment, I don’t think it crosses the line. You do not make light of the people affected by Matthew but are talking about the disaster movies. If there was any doubt, your new comment makes your humanity pretty clear. When talking about volcanoes, one always needs to acknowledge the effect they have on people.

        • “effect on people” … the effect on me is I stay away from them. The one thing that I have learned from hanging out here, is that the only full proof way to avoid being killed by them, is to not go near them. Works every time.

          Even watching them from a “safe” distance can get you killed. Mt St. Helens proved that, and Hekla proved that she can whack you even further away than that.

          • Fat lot of good “stay away from them” did the numerous Britons who died from Laki’s SO2 in 1783.

            P.S. I’ve run the numbers, and it seems we are statistically overdue for the eruption of a new top-level article here at VC. 🙂

          • I understand your point Lurking, but nevertheless people in Iceland are crazily brave and despite keeping strong respect and preparedness about volcanoes, they do not fear them.

            Icelanders do not avoid or stay away from volcanoes.

            In fact it all comes down to luck, statistic or fate, or whatever you want to call it.

            I lived 50km away from Hekla for 5 years.
            In 1000 years, only 1 person was once reported killed at such a distance by a Hekla lava bomb in 1510. It does happen, but its rare.

            I would never live less than 25km away from Hekla or Katla. It is asking for trouble. And within 50km you can run the risk of being inside the full blown volcanic night, as it happened in 2011 in Grimsvotn. That is enough to kill you by lightning if you are outside during such period.

            The gas its fine. I survived Holuhraun. We all did. Laki-style events only happen in Iceland every few centuries. The risk is real but low.

            When you live in Iceland you must be an optimist. In 2014, I experienced daily M5s earthquakes, months of SO2 choking haze, snowstorms one after another, every few days, some with hurricane winds, summertime snow and frosts, and so on… it´s nature on its full power!

    • Lurk ! What happens when Nicole gets up close and personal with Matthew? (Please keep answer clean and not smutty!) Could they combine an become a single intense hurricane or would one counteract the other and lose energy? I hope you and Mrs Lurking stay safe and make sure the dogs are secured. I would hate to see a flying rat dog!

      • Honestly? One of the two will be dominant and sap the convective potential energy from the other. Happens a lot.

        The thing that worries me is thst the latest NHC discussion says that it might slip under that trough that I have mentioned. That could be good and bad. The bad part is that it would be free to turn to the west. The good is that would take that “loop” motion out of the equation. The end point of that model forecast would leave it in a similar track position of Erin, a storm that crossed s florida and made it to the Gulf. Erin eventually made landfall here as a low powered hurricane. On the other hand a west turn now would point it towards the gulf as well, and the next frontal boundary is still a few days out before it could conceivably get here to block it. But, there is a wad of fairly dry air here, so that could sap it of strength a bit.

        • Cape Canaveral is in the firing line, and that is off the coast. I wonder how vulnerable it is. It must have survived these hits before though.

          • There have not been many hurricanes that have hit this area of Florida surprisingly. And of those that have impacted this region, none were close to the magnitude of Matthew.

            With that said, I would personally imagine that it is very well-built, and probably constructed with hurricanes as a threat in mind. This however is just a guess, and not any real knowledge of the situation.

          • According to what I’m hearing, that section of coast has not had a direct strike from something this large in the historical record.

            For the other data mongers…. the HURDAT file and it’s reanalysis can be found from this site. HURDAT has 6hr data points (when available) on everything going back to 1851.


            Spoke to my grandson just a few minutes ago. He noted that the interstate through here is packed with traffic. Dunno if it’s South Florida people or not, but it wouldn’t surprise me. The odd bit is that there are two other main north-south corridors east of here. One near Talahassee, the other in Jacksonville. I guess I shouldn’t be surprised. On one voluntary evacuation I wound up in Monroe Louisiana via Birmingham. This was highly stupid on my part since I have family in Mississippi and could have easily stopped there. The main reason I didn’t was that I couldn’t get off the Interstate at the required turn and I don’t know that section of backroads. I didn’t want to be lost in the middle of the woods on some nondescript road during a hurricane.

    • Hi Peder. The lines below the 3+ signal is wind or rain. The best way to check if a signal is weather is to look at the drum plots across the country. If there is a similar pattern on most stations facing the wind direction then it’s weather. If the signal is only to be found on the drum plots in a localised area they could be something else happening within that area or a localised heavy shower/thunderstorm. The IMO has issued a gale & heavy rain warning to be found in a yellow box on the home page and above other pages.
      Weather signals are linear & small. Volcanic signals do become linear when there is a harmonic tremor often shortly before and during eruption. They are bigger signals and you will know when you see them! They will not appear so large and clearly on Drum plots far away from the source. When we watched the eruption off the coast of El Hierro in the Canary Islands (We called the volcano Bob) the signals resembled a rather attractive knitting pattern! Quite regular and filling the whole page with green and red signals (The colour is not important it is just use to distinguish the base timelines)..No gaps.
      It’s very difficult though to interpret seismic signals but it gets easier in time. At least it gets easier to guess more correctly! Years on and I still get confused!
      This page is helpful but not all signals are classic in shape so difficult to interpret unless you are expert, but it’s a good starting point.


      PS you wont probably see many signals from human footsteps or moose on the Katla drum plots. See the rather good illustration in the above link!

      • Good answer! Furthermore, on the front page the IMO eq chart says “Warning Strong gale force wind is expected at the south coast and in the southern highlands tomorrow” which is another clue. 🙂

    • There’s heavy rain in SE Iceland, so I’d say it’s weather related.

    • Predictions of any natural event cannot be exact but at least these days there are warnings which are as accurate as can be. Sadly there is a generation who either completely disregard warnings, the “I am invincible” brigade or “The end is nigher”s who want to survive at all costs right down to buying food they will not actually need, in bulk, to overloading the motorhome with said provisions thus breaking down on the highway and causing evacuation hold ups and putting more people in jeopardy. The Icelanders have got it so right. Everyone knows what to do because they have been educated about natural disaster scenarios from an early age and take it all as part of life and act accordingly .

  11. Just to give an hurricane how is the eyewall of a major hurricane. This is what a part of coastal Florida is going to be experience.

    No one should ever be in the line of the eyewall, unless of course you´re a crazy and well prepared storm chaser!

    • It is only now becoming clear how badly Haiti was hit. A humanitarian disaster.

  12. Meanwhile Iceland is experiencing a major storm. Winds are near tropical storm intensity. 108 km/h

    This is why most earthquakes are not being detected at the moment.

    And that´s really a major warm and moist air mass. Temperatures in north and east Iceland have reached almost 19°C today. It must have been an October record! This is an insane temperature in Iceland at this time of the year.

    • Also insane weather here in the Faroes, clear skies, not a wind, temps in the double digits, bbq etc. It’s supposed to be snowing/sleeting and storming this time of year.

      • Our local farmer next door has just cut and brought in another harvest of silage. I have never seen grass being cut and stored at this time of year before.!

      • Bjarki as it should be in the North Atlantic. Maybe we will suffer later in the winter to make up for it! 🙁

    • Occasional commenter Bruce here.

      It’s always worthwhile having a look at the jet stream in such cases. ” rel=”nofollow”>Here is the map for about the time of your comment. The jet stream is coming right up over Iceland nearly from Spain…!

      The CRWS site is nice that it has an archive by date and time you can always look up.

    • A bit of a strange one – I wonder what it is feeding on. And Matthew is really going for it. At the current track, it could even hit Florida twice – a second time on its return journey on Wednesday.

      • I remember back in ’94 Hurricane Gordon looped around and hit Florida twice. Matthew’s a much stronger hurricane though.

        My children’s grandmother lives not far from Kissimmee, FL. I’m concerned about her tonight and if Matthew loops around she’ll get it twice. There’s a hurricane warning for her until 7:15am and continued bad weather until 11a. One of my son’s name is Matthew. We’ve been having teasing how the wrong Matthew is visiting his grandmother. Keeping it light, trying to ease their worry. They’ve reported as of now nearly 215,000 are without electric.

        Then My cousins live out and in the area of Venice, FL. She said they have a tropical watch until 8:15am, so tonight it’s to be wind and rain, but if it loops around it’ll be a whole different story for them.

  13. To all: The next pressure strain along the Reykjanes ridge along the path to us will make me more angry than ever. As you wonder, there is a connection! Stay tuned!

  14. “And now we take you live to our dip#### reporter, standing on the beach…”

    Who then spews the same report about what happens for every hurricane. Supplies are short, roads are horked, water is coming.

    The spooky bit about this is that it appears that it’s gonna be a nighttime landfall. (Or “land ho” as i heard the local weather twit state one time)

    At night, it gets really creepy in major storms. All you hear is wind and stuff banging around. You don’t know if it’s nothing or a T-Rex rummaging around outside. You want to look, but you know that if you stick your head out it might get taken off. During Ivan, while hunkered down, I noticed headlights shining into my garage. I peeked out the window and saw the tractor part of a rig turning around I’m my driveway. Shortly after that an oak tree ate my bronco…. but the bronco prevented it from rolling into the house. Yeah, storms will make you question your reality. Your mind races trying to figure out what you are hearing.

    And according to the most recent press conference, as of 3 pm Eastern time zone, they have 280,000 that have evacuated so far. Lane reversals on the key evacuation routes will be in effect until tomorrow just in case there are any last minute “maybe I better leave” people. Also, the bridges will remain open until winds get to 40 mph. (Typical, that’s what the criteria was here for our storm in ’94).

    • Watching from afar Lurking. Fingers crossed for you all. Stay safe. What is a bronco? Your pet dinosaur? I know they have pythons introduced and indigenous reptiles of the alligator variety but T-Rexs are there too? Maybe an escapee from Disney World or Universal?

      • Bronco II to be more specific. A form of fully enclosed truck. Ancestor to the SUV species. Bronco II had a bad rap with roll over hazards, but that was mainly from people who were not familiar with driving high center of mass vehicles. I had mine for 14 years and typically put it to use hauling my assortment of stuff back and forth to various duty stations. (which is was perfectly suited for, it could hold a couple of seabags and assorted stuff quite well)

        The Bronco II was just a much smaller version of the Bronco, which was based on a “full sized” pickup chassis. Bronco II is about the size category of the Ford Ranger. (even used the same engine family)

    • I appreciate that night time noise worry, my Oregon coast experiences were similar.
      No hurricanes but when the guy wires holding the chimney on started humming
      steady it meant the wind was at least 60kt. 95kts were not unusual in a good sou’wester..
      One night while wife and I were in bed , we heard a crrraaakkk, and our big shore pine
      split in two and the top was swinging out side the bedroom sliding door…I got out a line
      tied it to another tree and as I was doing that the top came loose and fell smack on the deck. Still howling I came in took off the rain gear, poured a nice big shot of hot
      Saki and took a hot shower followed by a shot of Jack Daniels..
      We slept much better. Took out the rest of the shore pines close to the
      house after that -all infested with termites..
      Now I worry about wild fire….

      • In the UK this would not normally be possible. You have to get permission from the council, and its virtually never given. Trees are like gods here. Got one massive beech within 12′ of a 1700’s listed house which will be destroyed when it falls (its roots will be right under its non-existant foundations). Nobody realises that a 70 year old tree can be remade in 70 years, but a 1700’s house cannot.

    • Know the feeling. Houses on my island at Swedish west coast got a lot of damage in a 2004 storm. Happened in night. Sounded like a never ending train passing by on the roof, interupted by shattering of glas windows and twisting metal. My house got partially destroyed. I cannot sleep in stormy nights after that..

    • I know the stormy night feeling. Houses on my small island, Swedish west coast, were badly damaged in a 2004 storm. It happened at night. Sounded like a never ending heavy train passed over the roof, interupted by crashing windows and twisting of metal. My house was badly damaged. I can not sleep stormy nights after that.
      Hope you are safe over there!

  15. Hmmm.. Something is happening at Hekla.

    A M1.0 earthquake, quite shallow was detected this evening around 19:30 and then I suspected a second smaller earthquake happened, but it was not shown due to the stormy weather, but it seems to show in the tremor plot.

    Borehole data is still normal but some GPS stations has shown slight sudden shifts in the last few days. It seems to show some movement to the west of Hekla summit.

    I suspect that the risk for an Hekla eruption in the next hours or few days is increased! But this is a very unpredictable volcano.

    • Meanwhile an earthquake swarm is just developing in Katla. The largest earthquake seems to have been around M3.0 and all have been shallow. I think this is just the beginning of a new swarm and it might have a larger earthquake eventually.

      • Thursday
        06.10.2016 23:08:05 63.620 -19.095 0.1 km 3.4 99.0 4.5 km N of Hábunga followed by smaller ones yet to be verified

      • This swarm seems to be mostly in a pretty tight area. It will be interesting to see how that one behaves, so shortly after quite a promising swarm about a week ago.

        • Strongest quakes very shallow, according to Carl on the top of the caldera lid, but now there a some activity going a little deeper. Calder lid said to be 1,5-2 km. Also earlier in week some much deeper activity. Maybe Katla has got some more stuff to boil…

    • The second Hekla quake is listed now.

      Fimmtudagur 06.10.2016 19:52:43 63,978 -19,660 9,8 km 0,9 99,0 1,6 km SSA af Heklu

  16. Yep. It’s sizable. For scale, Pensacola to Jacksonville is about 365 miles. (the far west end of Florida to the Atlantic)

  17. Remember my reply to Peder further up when he asked about lines of small signals re Katla?. I replied that to assess if it is weather, if most areas have similar bands of signals over a wide area then it’s weather. If the signals are only in a local area near a volcano something other may be going on. I fear for my little Dalek on Burfell next to Hekla. As Irpsit says earlier something is different there. Here’s the drumplot signal this morning.

    A band of activity that does not match the wind action in other areas . I know this is on a mountain and catches the wind but other wind signals ,like on top of Katla, are not so intense. I know there is a gale warning in force and most drum plots show that windy weather is starting. Hekla is different. Plus as Irpsit says ,increase in strain and seismics moments This is the the most intense unrest I have seen in the few years I have been watching .As ever in Iceland Volcano watching we play the waiting game. Katla too seems very irritable. . I think if the MAR gives a little yawn it may wake up those resting next to it!
    For those who do not have the drum plot map it is here to compare signals…..


  18. Carl is unwell at the moment so I have taken the liberty of sending him an eCard on behalf us all at VC telling him to get well and back to us soon.

  19. Looked in on Hekla’s webcam. The clouds are rushing past so it looks pretty windy there. Perhaps that’s the reason for Hekla’s low level signal?

  20. A small question if I may. We here all love reading and talking about volcano “stuff” but can I ask you all why we love Icelandic volcanoes so much . Lurking I have sympathy for u and your fellow Floridians. But it’s just a breeze . I slept through hurricane Dennis when I was on holiday there.

    • Why Iceland’s volcanoes? Well, speaking for myself – a Brit – I have loved Iceland and (Icelandic) volcanology since visting the Krafla Fires when I was a student in 1980.

      More generally, I suspect that for many Europe-based, English speaking volcanophiles (both professional and amateur), Iceland is a kind of living laboratory. There’s good, accessible data and literature in English, and there’s a lot going on.

      Also, some of the pros on here have done research in Iceland.

      But, all sorts of views are represented here, and are equally welcomed. We learn together.

    • “slept through Dennis”

      Yeah, agreed. I’ve slept through missile launches also. Even though the magazine and handling space were next to my berthing compartment. Machinery I can sleep through with no problem. An erratic large thump in the middle of a storm… not so much. Generally though, the best sleeps are during heavy rainstorms (with lightning) for me. The biggest problem is the Pekinese will try to crawl on me seeking refuge from the thunder.

      • My years flying airtankers was similar -to this day I can sleep through C-130’s hot loading 20 ft from the pilot’s shack, Wife running vacuum cleaner-no problem.
        -Bit quieter than the 130’s
        But let a gate go thump or the mini poodle pounce on the bed at 3:00 am I bolt upright.. Yet I like a good thunderstorm and rain too. I like to sleep with the window
        open, wife says its my Neanderthal/Highland Scot/Cherokee blood…
        BTW the Springer could sleep though D-day, he is the most laid back dog I have ever seen. The Poodle on the other hand, she is the Alpha of the pack and he
        lets her-less work for him..

      • Heh… C-130s. Duke Airfield is one of Eglin AFB’s C-130 main base of operations. It’s corridor goes right over Okaloosa Correctional Institute. You can usually see one orbiting around the area logging flight hours. For the weird, Hurlbert has the V-22 Ospreys. One really funky looking aircraft to see putting around. Hurlbert’s approach pattern goes right over US-98. Every time I see a V-22, it just doesn’t look right to me. It’s low speed normal flight dynamic is essentially a twin rotor helo going sideways. H-46s sliding in sideways to drop or pick up a pallet are poetry in motion. The V-22 is just “AHHH!” I’m just guessing, but I am pretty sure that their wind envelope for shipboard operations is about the same as the H-46 or H-53. They make their own wind envelope and don’t really care what the wind across the deck is… until you get into out right stupid territory, in which case you should not do flight ops.

        • Few years ago V-22’s visited the area. local Air Guard base in Pendelton, Or. hosted them. CH-47’s are based there. Agreed
          strange aircraft. USFS tried them for bucket ops, downwash is
          a big problem. Our local emergency room doc is a former USAF
          Para rescue- Major. Command Pilot in both Helos and
          C-130’s. had a bit of time in the V-22 his opinion:
          “Potential-lots of potnetial..”

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