The Reykjanes Fires

Now that Fagradallsfjall has finally erupted it is clear that a new eruptive period has initiated in the Reykjanes Peninsula, we can expect many more eruptions to come in the following few centuries, but what should we expect? and what about the eruption that has already started?

The last time the Reykjanes Peninsula was active was during a series of eruptions, roughly in the 950-1240 year period. Although there were people around, there was of course no one to take scientific notes,  so the information is very sketchy. In an attempt to fill the lost history I have looked at a couple of lava flows in Google Earth and tried to interpretate their origin. And how do I do that?

Volcanic landforms reflect the kind of eruptions that created them, for example the height of a lava fountain is about the same as the diameter of the top of the cone that it creates. There are also various types of lava flows, pahoehoe sheets, aa sheets, tube-fed pahoehoe, toothpaste lavas, raised lava channels and ponds, all of this together, and with the relationship between the various features, the volume and complexity of the lava flow, it can give clues as to how the eruption happened.

Before getting into the individual eruptions I should mention the two general progressions that fissure eruptions generally follow.


Two types of fissure eruptions

We are used to used to seeing Piton de la Fournaise, Kilauea, Galapagos, or Bardarbunga erupt, their fissure eruptions follow one general pattern. First, the curtain of fire, when a long fissure bursts into a chain of lava fountains and for a short time the highest eruption rates are reached. Then the eruption focuses into one or a few vents and stays there, the effusion rate falls exponentially until it stops, or it enters a prolonged phase of slow activity at just a few cubic meters per second. From a curtain of fire to a single vent is the typical sequence of a fissure eruption.

However there is another important end member, this is a somewhat rare type and not many examples come into my mind, but there is a big one, the Timanfaya eruption of 1730-36 on Lanzarote, in the Canary Islands. This is a very dramatic case, but that’s why it’s a good end-member example.

Timanfaya started from one single vent initially, but then over the following 6 years, the focus of activity kept shifting from one vent to another, countless times. By the time it was over there were many vents lined up in a row, so that it looked like a fissure, but no one would have thought that when it started. There was no clear reduction in activity either, it just kept going, a terrible deluge of ashes and lava with no end in sight.

It’s not easy to tell apart the two types from looking at moss covered lava flows from ages ago, however, I do get the impression eruptions of Brennisteinsfjöll and Hengill may follow the Timanfaya type, whilst eruptions of Svartsengi follow the curtain of fire type, I’m not sure about the others.

And now, with that explained, we should start where the Reykjanes Fires started, with Brennisteinsfjöll.


Brennisteinsfjöll eruptions. ~950 AD.

There are four different historic lava flows in the Brennisteinsfjöll fissure swarm. All of them formed in slow eruptions, from fissures that were less than 500 meters long with one to a few active vents, and fountains that only reached up to 100 meters high at most. From what I’ve seen each of the flows must have been erupted in a period longer than a month.

Hellnahraun is an example of a very slow eruption. Lava moved inside lava tubes, it inflated from within and formed many small breakouts of glassy pahoehoe lavas. It was the sort of activity that was typical in the Pu’u’o’o eruption of Kilauea. Lava reached what is now the small coastal town of Hafnarfjörður, on the outer edge of Greater Reykjavik. Taking into account the volume of around 46 million cubic meters, and effusion rates that must have been in the range of lava tube eruptions, 1-10 m3/s, I estimate the eruption most likely lasted around a few months.

Example of pahoehoe lava breakouts. From Wikimedia.


Another nearby flow, Húsfellsbruni, was possibly the longest and most voluminous eruption of the Reykjanes Fires. It forms an extensive apron of lava flows that is extremely complex. It was hard to understand its origin story because at places there are as many as 4 or 5 flow sheets that seem to lie on top of each other. The eruption involved mostly channelized flows and aa sheet flows, but there were also lava tubes, ponds, inflation plateaus, and toothpaste lavas.

Toothpaste lavas, also called rubbly or spiny pahoehoe, are a higher viscosity form of pahoehoe. Although Reykjanes lava flows have a very low viscosity the cooling lavas within the core of aa flows can erupt again from breakouts and form fields of toothpaste lavas, these look a bit like a mix of pahoehoe and aa.

Lobe of toothpaste lavas formed in the Húsfellsbruni eruption, it is shaped like the roots of a plant.

The volume of the Húsfellsbruni lava flow is hard to estimate because of how complex it is, however I wouldn’t be surprised if it came close to or exceeded 1 cubic kilometre. This eruption I’d say most likely lasted one to a few years. There is also the question of whether the historic lava flows of Brennisteinsfjöll represent separate eruptions, or rather just stages in a long eruption with a shifting focus of activity.

Example of a lava tube skylight. Every Brennisteinsfjöll eruption had some of them. From USGS.


Svínahraunsbruni. ~1000 AD.

This eruption happened between Brennisteinsfjöll and Hengill in an unnamed fissure swarm. There are three lava flows that are considered historic, according to the geologic map I’m following. They lie close to each other with vents that line up.

Each of the flows issues from a fissure that is only 250-500 meters long. One fissure is unnamed and seems to have had only weak spattering and a very small flow.  Two bigger flows issue from fissure vents called Nyrðri and Syðri respectively, and both had lava fountains that probably reached 50-80 meters high at some point, issuing mainly from 1 or 2 vents. Syðri erupted on top of Nyrðri.

Nyrðri craters feeding a lava channel. This eruption happened around 1000 AD. From Google Earth.

It is hard to know if they formed in one or multiple eruptions. If we follow the Timanfaya model it could have been an eruption with three stages in which the vent focus shifted, but it can’t be ruled out that they were different eruptions altogether.

I shall describe Nyrðri, the biggest flow. Most of the time the lava erupted from a single circular spatter cone, bubbling up or making low fountains that spilled into a lava channel 30 meters wide. Lava streamed down this channel, raised above the ground with flanks covered in shiny pahoehoe. The channel shifted its path a few times throughout the eruption. The lava was channelized for 2.5 kilometres, then it was distributed over a branching system of blocky aa lobes and toothpaste lava outbreaks.

Example of a raised lava channel with pahoehoe overflows. From Wikimedia.


Considering the three lava flows as stages of one eruption then the volume is 110 million m3. I thought eruption rates of 10-20 m3/sec were reasonable for its level of activity, that gives a duration of 65-130 days. This is a guess. The flows may have formed in separate eruptions, but still most likely the duration would be in the range of one to a few months.

Aa lava flow with a folded surface and toothpaste lavas around the edges. Syðri eruption. From Google Earth.


Eruptions of Trölladyngja and Krýsuvík. 1151-1188

Fire is reported near Trölladyngja mountain in 1151 and again in 1188. These reports probably refer to three historic age lava flows that exist in this area. Of these, Ögmundarhraun and Kapelluhraun were large eruptions. Each formed large lava channels running into the ocean in opposite sides of the Peninisula. The other smaller flow was short lived and may have been part of the Ögmundarhraun eruption; their fissure systems line up too.

These lava flows, as well as many other prehistoric eruptions of both Trölladyngja and Krýsuvík, are stronger than those of Brennisteinsfjöll and Hengill: they erupt curtains of fire with tens of lava fountains bursting at once over a length sometimes exceeding 1 kilometre, and very rarely some fountains can reach up to 200 meters height.

1984 Krafla eruption, the Kapelluhraun lava flow from Krisuvik volcano may have looked similar.

In the eruption of Ögmundarhraun intermittent fissures opened over a length of 9 kilometres, I don’t know if there was an initial phase of fire curtains affecting the entire length or if the various segments were activated at different times. The vents opened along the valley of Mohalsadalur, flooding the entire floor. Lava poured in rapids where the valley was narrow, and then dived below the smooth brilliant crust of lava lakes that collected where the valley was flat and wide.  Lava entered the ocean in massive flows of aa lavas. It seems the system of winding channels extending towards the coast reorganized multiple times, so it was probably a lasting feature and a significant volume of lava must have ended up underwater.

In the late stages of the eruption activity had focused in a 500 meter long fissure, on the order of 10 fountains were playing to low heights, or some perhaps up to 50 meters, their streams merged into a singular mighty river slowly flowing towards the ocean 6 kilometres away. The flow broke into two branches, each half a kilometre wide, and entered the ocean 2 km from each other, amidst what must have been boiling seawater, dead fish, and towering columns of snow-white steam.

Example of an ocean entry like those of Kapelluhraun and Ögmundarhraun. From USGS.

It seems difficult to make any guesses about the volume or duration of Ögmundarhraun, other than it must have lasted more than a few days, but could have been much more, and that the volume must be more than 100 million cubic metres.


Eruptions of Svartsengi and Reykjanes. 1210-1240 AD.

We arrive to the last volcanoes of the Reykjanes Peninsula as we travel westward together with the migrating activity of the Reykjanes Fires. These two fissure swarms produce intense eruptions with curtains of fire similar to those of Trölladyngja and Krýsuvík, or even more intense. For example, one prehistoric eruption included a kilometre long unbroken curtain of fountains shooting to heights of 100-200 meters.

Example of a fire curtain, a line of fountains, which are probably frequent in Svartsengi eruptions, the lava flow is a sheet of pahoehoe which typically forms in eruptions of >100 m3/s. From USGS.

Svartsengi produced three lava flows, Arnarseturshraun, Illahraun and Eldvarpahraun, I will focus on the first two, which I think are parts of the same eruption.

Illahraun erupted from a 200 meters long fissure, but the eruption was very intense. An area of 8 km2 was rapidly flooded by a sheet of molten pahoehoe lavas, including the present location of the Blue Lagoon. The surface flowed as a mass of crustal plates carried by the molten rock below, as it moved the slabs clashed against each other lifting into broken ridges.

The cones that fed the eruption barely have any prominence and the flow is one simple sheet, this is all probably because the outbreak was very short lived. The total volume was 38 million cubic metres and eruption rates must have been on the order of hundreds of cubic meters per second, so that the effusion can’t have lasted much more than a few days. Illahraun however may have taken place concurrently with the opening of fissures along the same line to the northeast which fed the longer lived Arnarseturshraun flow.

Arnarseturshraun must have opened with a line of fountains and a rapid outpouring of pahoehoe lavas, although this initial stage is largely buried under later activity. The eruption rate declined progressively. For some time a raised lava channel kept supplying lava towards the north which fed a massive slowly advancing wall of aa lava, crustal plates from the initial lava flood as large as hundreds of meters across were rafted downstream and collided with each other raising up meters high ridges of rubbly scoria, much like tectonic plates that collide to form mountain ranges. Activity kept decreasing and some more lava channels were formed to the north, however activity focused more and more around the vents.

Large crustal plates in the Arnarseturshraun lava flow, they are separated by ridges of broken up lava. From Google Earth.

Because the ground is mostly flat, lava had ponded around the fountains of the Arnarseturshraun lavas, this evolved into three lava lakes raised slightly above the ground by overflows, the largest with a triangular shape and 200 meters wide. Small fountains and dome fountains probably played in the lakes and distributed lava over an intricate system of channel and lava tubes leading up to small lava flows nearby. It is clear that this must have been long lasting, more than a few weeks, but it is hard to know how long.

Example of a raised lava lake, similar to the lakes of Arnarsetur. From USGS.

Lastly the historical records mention some submarine eruptions offshore Reykjanes, or by the coastline. An eruption in 1211 formed new islands, called Eldeyjar, meaning islands of fire. An eruption in the winter of 1226-27 is said to have produced darkness at midday, it must have been an explosive phreatomagmatic eruption with ashfall. New eruptions happened in 1231, 1238 and 1240. This last event was the final of the Reykjanes Fires and then the whole region entered a prolonged dormancy that was only broken now that Fagradallsfjall has erupted.


The future

The story of older eruptions can help understand what is to come. I can now make some general predictions. For example, if Reykjanes of any offshore volcano erupts it might be explosive phreatomagmatic and ashy, if Svartsengi erupts it will start with a very intense eruption with curtains of fire and be followed by an exponential drop in effusion rates, but if Brennisteinsfjöll or Hengill erupt then expect slow eruptions at near constant rates.

Problem is that the current eruption doesn’t belong to any of these volcanoes, in fact it opened in a very strange location and it turns out the magma is coming straight from the mantle. According to scientists this is quite extraordinary, and extraordinary magmas bring fantasies of extraordinary eruptions.

There is one very rare type of Icelandic eruption known as a lava shield, or a dyngja. These eruptions are thought to feed from primitive magma from great depths, and they are not associated with the shallow magma chambers of central volcanoes that feed the large fissure eruptions. Many commenters have already been discussing that we may be witnessing the birth of a shield volcano, Irpsit I think was the first to mention the possibility. The reason to think this is that the magma is from the mantle and the vent has opened outside the fissure swarms. A shield is a huge eruption that produces multiple cubic kilometres and lasts decades, it is a slow tourist-friendly eruption with lava tubes and inflated pahoehoe flows. The magma coming from the mantle is certainly a good sign, the last time an eruption came from the mantle was in Mayotte… 5 km3 or more, and still going. But while it’s true that shields erupt magma that is very primitive, it is not true that every eruption that brings out primitive stuff is going to be a shield.

Sandfellshæð, a lava shield of the Reykjanes Peninsula, formed 14,000 years ago, it seems to have had a lava lake or shallow sill intrusions, or more likely both, at its summit. It is cut by normal faults from many grabens that form when dykes intrude. From Google Earth.

So far the Fagradallsfjall eruption has followed a similar pattern to those of Brennisteinsfjöll and Hengill, a short fissure eruption at a slow steady rate. If it is similar in the other respects, the eruption should probably last on the order of some months, but it could also last years if it is a large eruption like Húsfellsbruni, or even decades if it becomes a dyngja. If it is Timanfaya-like then dyke activity may keep going and new vents could open elsewhere as much as months or years from now.

We shall see what comes to be of Fagradallsfjall, but in the meantime we can understand the eruption from a much more full perspective knowing about previous fissure eruptions of the Reykjanes Peninsula in their rich variety.


559 thoughts on “The Reykjanes Fires


    Just before noon, there was a significant change in the craters in Geldingadalur, which could be the first step in merging the two craters into one whole.

    This is stated on the Facebook page of the Volcanology and Natural History Group of the University of Iceland.

    “Flow out of the North through a gap facing southwest (or thereabouts) and merge with the flow that is in the channel from the South and out into the main lava river,” says the site.

    Eldfjallafræði og náttúruvárhópur Háskóla Íslands
    3 hours ago
    Rétt fyrir hádegi varð veruleg breyting á gígunum. Flæði út úr Norðra um skarð sem snýr gegn suðvestri (eða þar um bil) og sameinast rennslinu sem er í rennunni frá Suðra og út í megin hraunánna. Þetta gæti verið fyrsta skrefið í sameiningu gíganna í eina heild.

    A significant change in the vent constructs took place just before noon today. Lava is now issuing through a breach in Norðri facing southwest and joining the channel from Suðri in feeding lava to the main lava river. This may well be the first step in merging the vents into one.

    • Taal is restless, it can mean many things can happen, but for a real eruption, there usually are more, precursory, larger earthquakes. Definitely one to keep an eye on!

    • Probably pressure building up. Curious if this is decompression-related after the drainage event last year! Taal always gives me the chills..

      • I am leaning towards pressure build up since there is still inflation at this volcano. I am unaware on the scale though, Gas emissions are fluctuating but there seems to be a downward trend. I am concerned that this volcano could develop a plug. Thankfully Phivolcs has it’s eyes sharpened thanks to the eruption last year.

  2. Completely off-topic… how common are earthquakes on Tenerife? I have just had a look at the canary islands on volcano discovery and there have been quite a few quakes particularly focussed on Tenerife, albeit small <2.5, within the past 48hrs.

    It could be nothing, there does seem to be an uptick in activity worldwide…


    • Don’t worry about that too much, small swarms are par for the course for this volcano! Now if we start seeing some bigger quakes then you can loot as you please.

  3. The main camera just zoomed. Looks like the fountaining is still going strong, it looks like less flow than yesterday, but the lava field is bigger so it will absorb more without showing it, possibly.
    The back camera looks similar to one of the views of the crowd looking at the Isle of Wight rock festival 1970.
    Sounds like a festival atmosphere, just with volcanic music instead of Jimmy Hendrix!

    • In fact if you just added digital effect of film scratches and a bit of noise it would look like it was actually shot in 1970 on Kodachrome Standard 8mm film. Although 8mm had higher resolution!

    • Brings new meaning to a “rock” festival. 😀
      I’ve collected my coat and I am now in a taxi leaving the neighbourhood…

    • There were the beginnings of the collapse during the ‘zoom-in’ sequence….unfortunately the camera returned to status quo about a minute or so ‘too early’.

      Seemed to have broken off just about where that steam was venting.

  4. The lava lake just breached it’s channel right in the center of the camera view ..
    Lots of folks moving uphill and of course right in front of the camera ..

    • At around 16:37 and onwards you can see that people clear the area closest to the lavafield

  5. Some tremendous fountaining going on now that the cone walls aren’t hiding the action – lovely stuff!

    • There was some definite fountaining in a new spot just behind the ridge, to the left of the two vents, about an hour and a half ago. (See my posts above for the timestamps). More than just lava flowing – low-level fountaining. I haven’t seen anything since, so if it was a new vent starting maybe it’s given up already.

    • I though so as well!

      The collapse of the wall (and it sliding into the lake), seems to have changed the direction of the flow. It seems that part of the flow is now directed towards the “exit” begind the cones.

      The webcams are not very clear (and the people in front of them are very annoyingly blocking the view), but I hope one of the thousands of people has some pics of this?! Haven’t seen any yet though.

      Btw. Someone posted a image a couple days ago, that showed the geography of the valley, including the current size of the lavafield. Could that person post an update? 😇

  6. Really nice show with amazing lava fountains. The end of the day is always my favourite in this incredible event.

  7. The latest timelapse, from yesterday 6 am to today 12 am.
    It waits until the last minutes to reveal it’s new shape.
    It also looks like there’s an ant plague in the area 😉

    • Great, thanks for making this time-lapse. Clearly shows that there was no big collapse of the craters, more a slow slumping to the side.

      Definitely looks like an ant plagues in the time-lapse, but I’m just envious that I can’t go…

  8. What was that thing closest to the camera, timestamp 20.36.20 ish – a drone sent up by the guys there?

    • that’s a living (?!?) proof that “No drones were harmed” shouldn’t be use here…but opposite..what about a dead drone counter?

      • there must be some dead and melted drones out there ….. maybe that’s what some of those flashes and bubbling are ?

  9. The rocky lava pool,
    is nice and warm,
    so juicy sweet!
    Our only wish,
    to catch a lava fish,
    so juicy sweeeeeet!!!! Cough Gollum!!!
    Sssshhhhhäääää … ssssshhhh cough

    • it always looks more spectacular and more active at night, you don’t get the glowing in daylight

  10. What about this 3.7 quake at Reykjaness that does not show up as a star?

    • Hasn’t been checked by a scientist yet. Will probably be sub 2.0 looking at the seismograph.

  11. This video is an explanation of why dykes and sills propagate in the way that they do:

    The basic conclusion is that although the physics behind it is fairly well understood (the principle of least action), actually doing predictions of where dykes and sills will propagate is nigh-on impossible at the moment. There’s a bit of maths, but not too much for most to deal with, and the general message can be understood whilst largely ignoring the calculus in any case.

    There are four videos on the channel in total: the one about dyke paths, a second on if preventing large eruptions is possible and a third and fourth which are the start of a series about the geology of Iceland.

    • I found Professor Gudmunsson’s comments at 10:52 to be particularly germane to discussing how dykes get started. He addressed a very common misconception that most people have regarding the initial formation of dykes.

    • Really spectacular fireworks display tonight. The volcano is playing to the crowd.

  12. The folks on the YouTube webcam feed seem to have christened the new volcano ‘Bob’. How do we tell them that we beat them to it a decade ago on El Hierro…!

      • I think it is ok, it will most certainly receive a real name in time now that it is getting bigger.

        I am going to call it Chadagigar 🙂

        • Excellent idea… among a few friends, i had a vent in Hawaii. Enjoy Your volcano. 🙂

    • It looks like it, each vent is about as powerful as the entire original fissure now from what I can see, and the area of the lava pond is bigger than the whole first days flow. I do recall it had a volume of 1 million m3 after the first two days, but now it is at about 8 million m3 after another week, so it has gradually increased to about double the daily output it had when it started by those numbers, which fits well to what I said above.

      1 million m3 a day is an average of 11.5 m3/s, which is rather more than the 5 m3/s often given. It is also too high for a pahoehoe shield, those form at or under 5 m3/s, so if a flow does escape the valley it will be a slow a’a flow instead, as such it is unlikely to flow a long way immediately.

      Thing is if this is a slow but exponential increase. I really dont remember much on how to do algebra but I think that situation would be (a x 2) + a, but knowing my personal history with maths this is probably not the right expression… 🙂

      This is a very long way of saying that yes it is increasing.

      • I guess if you go by an increase of doubling every week, then after 4 weeks the effusion rate will be about 80 m3/s, which is not extreme but is getting towards a major eruption for this type of activity. The fact there is no deflation anywhere nearby shows that this eruption is being fed by mantle decompression, not by a magma chamber draining. The very high temperature also means the lava is going to be melting the walls of the dike rather than solidifying, it obviously would go solid if it was just as it is but with new magma coming up it is not likely.

        I guess we will have to wait, but probably not that long. I really dont think this will be a standard Reykjanes eruption at all now, a shield or otherwise. I get the feeling that the professionals might be thinking the same.
        It is small now but I think by 2030 most of that area of the peninsula will be flooded under lava, from Grindavik to Keilir maybe even further north. One thing I noticed about Timanfaya is that it happened in a part of the island away from the previous recent activity, which was smaller and on the northeast side. There was no Holocene or even late Pleistocene volcanism in that area of Lanzarote before 1730.
        I get the feeling that is an important detail, there was a lot of magma accumulated at the base of the crust and all it took was one eruption to trigger a cascade, even if it could have been small at the onset. I think that is what we are seeing here.

        • This volcano looks similar to Surtsey, but without its two tuff cones. How big was the effusion rate of Surtsey when the west crater was erupting lava in 1964-1965?

          • 1 km3 over 3 years is about 5-10 m3/s, im not going more specific than that because I dont know exactly what the volume of the Surtsey eruptions is but I have seen it is generally around this, maybe a bit less. The eruption rate of Bob now is about the same.

            The most important thign about this is the lava composition, Surtsey was an alkaline basalt, though it was pretty hot for lava in that part of Iceland so it made fluid pahoehoe, Eldfell 10 years later erupted the same magma but cooler and it made a big a’a flow that was something like 20 meters thick. Bob here is erupting picrite basalt which is almost above the liquid point of all of its components, it is sourced from the mantle but the mantle under this location is nearly a total liquid to erupt lava like this. That is why I think it will get bigger but really who knows.

            Lanzarote erupted about 1 km3 of lava a year in the Timanfaya eruptions, whic hcomes to an average of about 30 m3/s, so it was not excessively huge like Laki just very persistent.

      • Surtsey also started much More vigorously than Fagradalsfjall 2021.If 1963 was on Land it woud be a hell of a sight with Puu Oo like tall fountaining forming a tall cinder cone and huge roaring lava rivers feeding distant huge Aa flows.

        That was before Surtsey turned into a slow pahoehoe shield.. and because it was in the sea it became pheratoplinian at start.

        Fagradalsfjall is much hotter and feeds much deeper .. yet started out small with not alot of gas. I do think that Fagradalsfjall may produce multiple km3 in the end. Picrite Basalts are quite rare to see erupting.

        Will Fagradalsfjall turn into Kupaianinaha like overflowing lava lake shield If the dyke widens and gets conduit like ?

  13. I still think that Gemini is a better name than Bob. This is basically two volcanoes for the price of one.

    • Ísólfur.

      After the poor Viking Ísólfur frá Ísólfsstöðum that allegedly got his grave there becouse he liked this valley that much.

    • Nooo the two vents are named …

      Gollum and Sméagol the joined personalities…

      Western vent .. Gollum .. are seeking the preeecuuioss

  14. Looks like it’s not too far from swallowing its spatter cones and becoming an overflowing lava lake in the process of building a shield.

    • I happened to notice them as well…..perhaps they are simply looking for anyone that might be unable to leave the area (for whatever reason?). The SAR personnel seem to be pretty decent (and professional) types.

    • They closed down access to the site and herded the remaining people down so the SAR volunteers could get some rest for the night

  15. It looks like the left vent is the only source now, it has a big fountain now and the right vent is spattering but not visibly erupting lava now. It could be the night glow but that fountain is something like 30-40 meters tall now.

    • I seems that both vents are independent from each other-and from my observation the two will not become one! Could be proven wrong.My guess is the larger crater-on the left,is still venting out lava at the base,out of cam view.

    • The contribution from the right/top vent appears to be hidden behind a ridge. You can see it clearly from the Beint camera; and it is still a significant flow.

      • When I made that comment it was definitely just the left vent erupting a flow but it seems to have been very temporary as the right vent started flowing again a few minutes later. I would guess maybe a lot of the lava from that vent flows through tubes inside the cone while the left vent is open.

        • At the moment the lava flow come mainly from the first vent (George Sr?). The younger vent fountains more and has a decent flow but not as high as Sr. It seems that Sr. and Jr. have the same pressure head, judging from the fountaining, so somewhere underground they are connected

        • When that South slope collapse happened yesterday, large boulders blocked the exit point and the vent has been overspilling from a much higher elevation than the North vent, which looks like it’s building itself an inner cone.
          My observations lead me to think that, after the large collapse overnight 27/28 March, both cones set about rebuilding spatter mounds between the vents and the old walls. The degassing/steaming appears to be coming from the gaps between new and old ramparts.

    • I have been watching for the last few hours and it seems the right side is still sourcing , the right side of both look weak.

    • From what I’m seeing on the webcams the right side is weaker than the left side, but still sourcing quite nicely.

    • Very curious to see updated mapping/photos showing current extent of flow towards east exit region.

      • My guess-current flow is about the orange corresponding to 15m on the key

  16. Just about to get coffee # 2 . I am watching some spectacular fountaining from both vents this morning. Sadly this is unlike our single drain that cannot emulate this kind of activity , not even a little spurt. However the Drain man cometh ,hopefully, tomorrow or Wednesday. Today I dig up some plants that are in danger of being excavated along with the drain. I watch with envy and interest and read the many hypotheses, suggestions, theories , ideas , and other general speculations on the development of this fascinating eruption. I have nothing to add but all your comments are keeping me from seriously reacting to my and my drain’s lockdown situation.Thanks everyone.

  17. Right now we have a small swarm in between the Hengill and the Brennisteinsfjöll systems.
    I wonder if the east part of the rift zone will join the party soon? And if a large EQ near Brennisteinsfjöll like supposed by the IMO is about to happen.

    • This is what I’m wondering about as well. Could it be that this won’t be confined to the Fagradalsfjall area?

      • The normal Reykjanes cycle starts at Hengil, although most cycles seem for whatever reason t oskip this step and begin at Brennisteinsfjoll instead. The fissure swarms progressively activate further west towards the end of the peninsula over the next few centuries.

        Fagradalsfjall is a part of Krysuvik, but most eruptions from Krysuvik have been from the part that was active in the 1100s, around Trolladyngja (which probably needs a different name, maybe whoever named it was a bit less than sober 🙂 ). Bob is fed thoug hfrom way deeper in the mantle than the normal Reykjanes cycle, so it probably isnt actually a part of it necessarily. I expect though because it has ruptured part of the fault that it could have rapidly accelerated the first half of the cycle, Brennistenisfjoll or Hengil (or both) might well suddenly become very active if that expected big quake happens, Krysuvik will apso probably erupt in its normal location in this century too. Reykjanes and Svartsengi I am not so sure, that location is the last to erupt, but really who knows now. I think there is quite a possibility this cycle has been severely disrupted by Bob and all the volcanoes could be active simultaneously over the next few centuries, which would be exiting but possibly dangerous for Reykjavik.

        • Hengil is not part of the Reykjanes system. It is a central volcano at the triple point where the fault changes character. Obviously stress does transfer between the systems, but the magma supply is different.

          • Yes, that is true, but I did want to cover all the possibilities.

            I did actually leave out one more remote possibility, that the tectonic shifting goes through the entire transform fault, and what is at the eastern end? Hekla


    • The Worm Moon. There’s thousands in my compost bins. My main task today is digging out and sieving into bags, and starting some seeds.
      There may also be some volcano watching :-}

  18. Thank you for all the nice informative posts. I just wonder, if there will be a new camera filming the exit flow out of the valley and at which time that will happen.

    • For me this looks like the whole of Reykjanes is being elongated resulting in cracks/dykes all over the place that once big enough might be filled from below. Could this be the case?

  19. What would a sudden drop in Taal’s seismicity mean?

    Just for data’s sake:
    Mar 23 to 27 — 1201 Volcanic Quakes, including 943 tremors, and 220 LF Volcanic Quakes.
    Then Yesterday and Today — 23 Volcanic Quakes, including 16 tremors, and 7 LF Volcanic Quakes.
    In between came a 34 hour low-level background tremor…

    • That would normally be a good sign. The stress has been released, although not entirely as there are still some quakes and tremor. If this is hydrothermal activity, it means some of the water has moved on. It may be temporary, with stress building again. For instance, the Iceland eruption came a few days after a swarm at the location of the eruption, with silence in between. But in general, decreasing quakiness is a good sign. I would still not recommend to go anywhere near Taal island though. It is not at risk of future explosions, but at certainty. But whether that comes tomorrow or in 50 years time we cannot know. Yet.

  20. anyone else watching the persistant fume from the upper right of the lower vent? Could it be the middle vent’s fumes have finally found a way out? or is it just a chimney of sorts? i’ve watched toooo long… 😉

  21. Small crater-wall collapse in the Suðri crater at 08:27:30 visible on the RUV camera. Was followed by more intense fountaining for a few minutes.

    • South is still fountaining from a perched pool created by yesterday’s ashy collapse. Huge boulders blocked the vent and forced the lava to pool at a higher elevation. The overflow lip is easily seen after this little collapse.
      Slightly OT, can anyone confirm if the eastern lava pond is higher than the rest? Or is perspective playing tricks on my eyesight?

  22. The area highlighted here in yellow is constantly turning over at the moment on the mbl cam.
    by Andrew Roberts, on Flickr
    It goes all glowing as the crust sinks, even in the bright sunshine, then rapidly cools and darkens again. The process repeats within a minute, there’s a huge flow there from right to left.
    Small fountains are an occasional result.

    Edited to remove links. Replaced by address. Links should point directly at the image, and only at the image. If you see anything else, wordpress will remove the link. Signed: A minor dragon

  23. are there any good volcano/geophysics podcasts out there? recommendations welcome!

  24. The left cone has a ring fault, it is doing a rotational slip into its lava tube.
    I think it is being undermined. The ring will gradually rotate backwards and slip down.
    Just like the landslips near where I live.

  25. In the middle of the picture below, you can clearly see a chunk which slid from the spatter cones to the left.

  26. I think it’ll be a very lovely lava-waterfall when it breaks through to Meradalur. Just look at the gradient!

    • Fountaining on the right of the view stopped now.
      Masked couple speaking English just took pictures and disrupted the signal.
      Will COVID really be a risk out there?

      • lava field fountaining is back again and this time a new one near the left hand cone.
        its like bubbling and spitting.

      • Covid had been eliminated from Iceland until a few days ago when new community infections started showing up. I don’t think volcano watching is a particularly risky activity in terms of covid. There is usually a stiff wind that will carry the virions out to sea along with the volcanic SO2 and people will generally be able to keep their distance. Still, wearing a mask is a sensible precaution.

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