The changing faces of Fagradalsfjall: fizz, bubbles and slugs

We have had quite a ride. The eruption began unseen, on March 19. The new fissure opened on April 5, after the initial double cone had begun to wane. The new fissures sprouted a series of cones, mostly twinned. By May, all twins had exterminated one of the siblings, and the survivors had battled for supremacy leaving one winner. From now on, this would be a singular eruption.

Remember our adorable cone-let that started the eruption? Now completely buried?

On midnight May 2nd, everything changed. The tremor increased, the eruption went out, and then suddenly the world exploded. This kept happening, as often as 5 times per hour; 400-meter tall fire fountains were visible from Reykjavik. The seismographs remained extremely noisy for a long time, many weeks, while the volcano kept booming and the lava rose and fell around every boom and bust. Over time, the strength of the booms diminished and the eruption became a pulsing one, with a lava pulse (and a boiling lava lake) every 8 or 9 minutes. Amazingly, during all this time the eruption volume remained constant.

There was a general expectancy among volcanologists, volcano watchers and the tourist board that the eruption could continue for years. But on June 28 the eruption suddenly stopped, only to resume a few hours later. This has since become a pattern. The seismographs suddenly go silent and lava retreats out of sight, leaving an empty cone. Then the noise slowly increases, lava rises and a flood of boiling lava appears, looking like a lava tsunami coming down the sides of the cone. The flood diminishes, the seismographs goes flat and the cycle repeats. The duration of the active periods has varied from a few hours to a full day but apart from a lengthening there is no clear pattern. And yesterday the volcano flat-lined and did not come to life again for over a day. Is this the beginning of the end, or is it the end of the beginning? Who knows. GPS measurements show deflation around the eruption: lava is erupting faster than it is being replenished. That can not last forever. On the other hand the remarkably constant effusion rate shows that the eruption is not limited by available pressure but by the carrying capacity of the conduit.

In the mean time, the Iceland Meteorological Office ordered extensive hill fog to blanket the eruption into extinction. That didn’t work. Iceland’s engineers experimented with other types of eruption control. On May 14 they began work to build two walls, in order to contain the lava field. To our amazement it worked for a while but eventually the walls were overtopped. Other walls were build to protect Natthagakriki (June 15) and the coastal road (June 25). These still hold, helped by the fact that the lava gave up and decide to flow the other way. The new walls haven’t really been tested yet. If the eruption now ends, then the engineers will be happy and the government will declare that the battle against the Earth was won and take credit. If the eruption continues, then all bets are off.

The recent eruption has shown four distinct phases, with possibly a fifth just happening

  1. Constant effusion. This was the start when the lava flowed continuously;
  2. Intermittent fountaining. This was an exciting phase, approaching a strombolian eruption;
  3. Pulsing with a few minutes of activity followed by some 5 minutes of quiescence; each pulse produced spattering and mini-fountains, with quiet flows in between;
  4. Intermittent activity, with bubbly lava lakes for a time of several hours or longer with lava flooding, followed by a sudden retreat where the lava disappears and the seismographic first show pulses and then goes dead quiet. After some hours (or longer) the seismograph begins to show a bit of noise, which increases while the lava slowly rises up again. Over recent days the pulsing during the turn-off has become very weak.
  5. (Failure. The eruption interrupts but does not restart)

The amazing aspect is that the average flow rate did not change over this time, at least until the last few days. All measurements have returned 13m3, ever since early May, while the eruption went through these changes. Neither has the lava composition changed much, although there have been some minor variations. What is happening?

Let’s first look at the lava itself. It has a mantle-like composition, i.e. a form of basalt. Basalt may not be what you want in your plumbing, but in fact it flows quite well as long as it remains insulated. It has a low viscosity and is low in silicates (the two are related). The composition has shown that the magma formed at a high temperature of around 1250K at a depth of 15-20 km. It erupts at a bit lower temperature of 1170K. It contains some amount of CO2, and less SO2. This did not change during the changes of the eruption style. The dissolved water content has not been reported but for Iceland eruptions is typically around 0.8%.

The seismograph signal shows the noise that is generated as this magma flows up the conduit that connects to the surface. The signals are shown for high frequency (higher than 2Hz) and low frequency (less than 0.7Hz)

This is an example of the high frequency signal, showing the sudden stop.

Here is the low frequency signal, showing much less of a change.

What causes the noise? First, notice there are no sharp spikes visible. This means there is no rock cracking, which would show up as many small earthquakes. The lack of crackling shows that the conduit (and the dike underneath) is stable. The plumbing in this eruption is now well established and it is not in need of work. That will change only when the magma retreats from the conduit. We do see occasional rock falls on the steep inner side of the cone, giving a drawn-out signal lasting a minute or more. There are none in the plots shown here. Instead, the signal we see comes from magma moving through the conduit.

Magma can flow in two ways. The flow can be laminar, like honey creeping over a surface, or turbulent, like water in a steep river bed. Laminar flows are silent. The honey that is in touch with the surface is almost stationary, and the further it is from that surface the faster it flows. So you never have a fast flow directly over a corrugated surface. Turbulent flows are very different. The liquid is moving at different speeds and even in different directions and there is a lot of interaction between fast flows and surfaces. This seems the noise that we see. When the seismograph is noisy, something is causing turbulence in the flow. When it flat lines, the flow is undisturbed and laminar – or it has stopped.

Two flow types in the magma conduit. The right hand one causes a noisy signal on the seismograph.

Do be aware that the seismographs can pick up noise from other sources. Especially the low frequencies pick up movement over large areas, sometimes including visitors. (They also see large earthquakes across the entire world.) Wind can affect both plots: the plot thickens and becomes noisy. When it storms, eruptions become hard to see.

The signal does not tell us where the flow noise is located. It could be in a deep conduit, it could be on the surface or in a lava tube. If you look hard at the high frequency signal, squint a bit, and use a bit of imagination, you can see a hint of pulsing just before the end, lasting maybe 15 minutes with pulsing repeating over 3 ot 4 minutes. That can only be in the conduit, so I am assuming that the entire signal comes from the vertical pipe through which the magma rises to the surface.

What causes a flow to become laminar or turbulent? The smoothness of the surface is important. A river can be beautifully laminar where it is wide and has a smooth sandy floor, but turbulent where it becomes rocky or changes its width. The viscosity is also important. A fluid with high viscosity (internal stickiness or friction: think honey) tends to flow laminar, while a low viscosity fluid (such as water) very quickly becomes turbulent.

The magma in Fagradalsfjall is a type of basalt which has low viscosity. That is both because of its composition (it has few silicate crystals which easily stick together) and because of its high temperature. The lava channels show a fast flow, and this is indicative of a low viscosity lava. By the time it gets to the end points in Meradalir and Natthagi, it has cooled down and when flowing on the surface it behaves more viscous, although not nearly as much as rhyolite which just refuses to flow and sticks to the ground.

We would therefore expect that our magma can easily become turbulent. It doesn’t in the lava channels: even though the lava flows fast, it is still laminar. That is by and large also true underground, as long as it flows through wide pipes or tubes. Indeed, the seismographs was noisy when magma was still breaking through to the surface and did not yet flow, but they became rather quiet when the eruption was well established. The flow underground was also laminar. But later the eruption became fountainous and after that bubbly. And the noise went through the roof. There was turbulence in the magma. The fact that this happened while the lava was bubbling suggest that there was gas in the plumbing. The gas in the low viscosity magma caused turbulence. Where did the gas come from?

Let’s take a step back, or rather down. The magma rises up because it is buoyant: it has lower density than the surrounding rock. The hotter it is, the lower the density, and so hotter lava (if there is a choice) rises faster. As it rises, the depth becomes less and there is now less pressure from the weight of the rock above. The pressure in the magma decreases. At the same the temperature also drops a bit. To give some numbers, at 15-20 km depth where the magma was sourced, the pressure was around 400 Mpa (4 kbar if you prefer) and the temperature was around 1220 K. (The melt had actually formed even deeper, perhaps 25 km.) By the time it entered the dike, at 6 km depth, the pressure was down to 150MPa and the temperature around 1200 K, and at the point where the dike connected to the conduit, perhaps 2 km depth, they were 50 MPa and 1190 K respectively. The magma erupted at the surface with a temperature of 1170 K.

Source: AGU webinar on Fagradalsfjall: Dr. Eniko Bali.

The origin of the gas lies in the changing conditions during the rise. Liquid magma can contain a limited amount of volatiles, such as water and CO2. If there is more of these then can dissolve into the magma, the excess is expelled and becomes a gas – a vapour inside the magma. The maximum amount that can dissolve in the liquid is called the solubility. It is different for each volatile. To give a rough number, basalt at 1200 K and a pressure of 50MPa can contain around 2% (by weight) of water. This amount decreases rapidly with pressure: by the time the pressure is down to 5 MPa (200 meters depth), the solubility is down to around 0.5%. It scales roughly as the square root of the pressure.

Temperature has the opposite effect: as the magma cools it can contain more water. You can see this effect when heating water in a pan. As the temperature rises, bubbles appear in the water. This is gas coming out of the liquid. Let the water cool and the bubble disappear again, taken up by the water. But in this magma the effect of temperature is fairly minor. The solubility of water scales roughly as 1/T (with the temperature T in Kelvin), and the temperature drops by only around 5% between 15 km depth and the surface. The pressure reduces much more dramatically, and it wins the battle. So while the magma rises, it tries to dry out and expel excess water. You may want to think of a volcanic eruption as a giant dryer.

Icelandic magma is pretty dry to begin with, but not that dry. At 0.8%, the Fagradalsfjall magma reaches a problem at 500 meters. At that depth it becomes saturated. As it rises further the magma begins to expel water and water vapour (steam) develops in the magma. The magma becomes gassy, and just like a human body after a good meal, it becomes windy and noisy.

CO2 goes through the same process as water but it does so at much greater depth. Mantle plumes may contain 1 % CO2 by weight, but this already turns into gas at a depth below 5 km. Some of this CO2 finds its own way to the surface and some remains as a gas inside the magma. By the time basaltic magma is at 1 km depth there is little dissolved CO2 left.

So water in Fagradalsfjall’s magma produces vapour during the last 500 meters of the ascend. This is not an easy process. A phase change (liquid to vapour or liquid to solid) needs something to hold on to. Pure water can in fact be cooled to well below freezing while still staying liquid. But shake it a bit and it freezes instantly. The water was supercooled. Air too can be supersaturated whilst not producing clouds . But when a passing plane disturbs it, instantly a contrail forms. It is the same with magma: it can become supersaturated with water but still reluctant to let it go. It takes time for the water to evaporate out of the liquid. If this is longer than the time it takes the magma to reach the surface, then the water will stay in the magma as an unwelcome passenger.

(I remember a camping trip (in Africa!) when after a chilly night we tried to pour water from a bottle into a cup. It froze on the way, mid-air. The water had become supercooled.)

When the water turns to gas, it forms small bubbles inside the magma in a process called bubble nucleation. Initially these are tiny, microscopic even. Nucleation is much easier when there are crystals in the magma: they provide a surface on which the bubbles can grow with ease. If there are no crystals, bubbles form with difficulty and the magma becomes supersaturated. But take supersaturated magma and add nucleation sites (crystals) and bubbles instantly form everywhere. If a magma rises rapidly, it will become supersaturated because the water has no time to respond to the decompression. But as the pressure continues to fall, at some point the supersaturation may become so high that nucleation accelerates anyway. Suddenly, gas is everywhere. The magma becomes fizzy and turbulent.

The bubbles are very buoyant and try to rise. But the magma is too viscous for that. It is worst for the smallest bubbles: friction with the magma locks them in place. Larger bubbles find it easier to rise, especially in a low viscosity magma. Let’s assume that the magma in the conduit rises at a speed of 1 m/s. That is a reasonable value for Fagradalsfjall: it gives the right flow rate (13 m3/s) for a conduit that is 4 meters across. The bubbles will move up a little bit faster, but not much faster. Even in Fagradalfjall they will only go faster by a few cm/s. The magma now becomes a mix of liquid and bubbles.

As more of the water becomes gas, the bubbles grow and take up a larger fraction of the volume. As the bubbles become mobile, they collide and can merge, or take in more water from the surrounding magma. And they also expand because the pressure is dropping as the magma rises. The bubbles can grow as large as a few centimeters. So as the magma approaches the surface, more and more of the volume is taken up by gas.

When bubbles take up more than half the volume, the bubbles merge into gas pockets. These are called ‘slugs’ and they take up the full diameter of the conduit, pushing the magma out of the way. If 90% of the volume is gas, then the slugs merge into a column of gas and magma is pushed to the side, but this may not happen in real volcanoes. In a bubble flow, the bubbles are stuck and rise with the magma. But in a slug flow, the slugs can rise rapidly because of their low density and because their smooth surface pushes the magma out of the way. The bubbly flow is sluggish and the slug flow is not.

What kind of speed can we reach? Here, the change of density is important. If half the volume is taken up with bubbles, the density of the mixture has halved. The magma now becomes very buoyant. If we start at 500 meters depth and use all the energy in the buoyancy compared to the surrounding rock to accelerate, by the time we reach the surface the velocity can reach 100 m/s. At that speed, a ballistic trajectory can reach 500 meters height. This is about what the highest fountains in early May reached. (The reality is of course much more complex. Much of the energy is lost in friction in the conduit and the slugs don’t travel anywhere near that fast. On the other hand the slugs still expand and this expansion greatly adds to the velocity.)

Slug flows are the dominant cause of strombolian eruptions. Each slug, when arriving at the surface, causes an explosion both because of its speed and because the slug expands fast in the low pressure around it. It throws out the surrounding magma (lava?) with it; it fountains, fragments and falls. If there is debris plug on top of the conduit and/or stagnant lava, the slug can become more explosive, and produce ash. If the conduit is open the fragments are ballistic lava. Fargradalsfjall always had an open conduit.

This degassing of the magma was the driving force during the fountaining phase, and the eruption changed because it began to degas much more. Originally, when the eruption first began, the magma did little degassing: this was the time of the constant outflow which we saw coming from the first cone, and later from the fissure. The magma at this time may have been less supersaturated, so that the bubbles formed slower and never merged into slugs.

There can be several possible causes for the change to slug formation. The magma may have changed, and had a higher supersaturation. This was also the time that the flow rate increased to its current value of 13 m3/s: this is possible with the same conduit if the density or viscosity of the magma became a bit less. The change allowed for faster bubble nucleation.

The eruption became extremely noisy at this time: because of rapid degassing the flow became bubbly on the ascend and therefore turbulent. The whole conduit, from 500 meter down to the surface degassed together. I envisage this as starting near the top. The sudden appearance of many bubbles drives out magma, and this reduces the pressure lower down where the magma now carries less weight. This decompression increases the supersaturation and allows bubbles to form here, and so on. A bubble formation front accelerates downward and the whole column turns first fizzy and then bubbly, before the rising bubbles begin to form slugs. It is just like opening an overpressured bottle of carbonated water.

(No slugs were harmed (or produced) in the making of these movies)

(An alternative idea is that the seismograph noise that we see comes from the bubbles themselves, as they implode, explode and merge, so that the turbulence is not in the flow but in the bubbles.)

Why the 10 minutes between the strombolian fountains? At a speed of 1 m/s, it takes ten minutes for the 500 meters of degassed magma to be replaced by the gas-rich magma from below, after which the process could repeat.

The pulsing that happened later was different. There were no high fountains, and there was no large acceleration. There were no slugs. Also, the seismographic noise happened mainly during the pulse whilst in between pulses the flow was much less noisy. The magma now was less supersaturated and fewer bubbles formed. The same process as before happened but the bubbles never reached the slug threshold of 50% by volume. The magma became bubbly but not sluggy. The bubbly flow still reduced the density of the magma, and this caused the level of the lava at the top to go up. The lava lake filled up and overflowed. The lava degassed over a couple of minutes as the gas reached the surface. This caused the apparent boiling of the lake. Once the gas became depleted, the density of the lava became higher and the level of the lake went down again. The lower noise of the seismograph now showed much less turbulence from bubbles. Over the next 5-10 minutes the magma in the conduit was replaced by fresh magma, and the degassing would start again.

This process explains why the flow rate of the lava did not change. The rate at which magma ascended from below remained constant all through these phases.

The current phase of long quiescent and active periods is different again. The fact that the seismographs are flat during the quiet period suggests that the flow becomes laminar without bubbles. There is no gas: the magma is not supersaturated. The density is therefore also higher and the level of the lava lower. We don’t know whether there still is any lava flow during these periods but it is possible it still flows -silently- through a deeper tube towards Meradalir, below the layer of the rubble that we can see in the cone. However, it is also possible that the magma in the conduit stops flowing and the eruption interrupts. It depends on how buoyant the magma below the conduit is.

Slowly the low frequency noise increases. A bit of degassing is beginning but the volume of the gas remains small. As the degassing increases the density of the conduit decreases, but only a little because there is less water available for degassing. The magma begins to rise, and the pressure below begins to drop. This causes some supersaturation and slowly more gas comes out of the magma and forms bubbles. The density decreases as before, the lava level rises and the cone overflows. The process is slow enough (several hours) that the magma is always in equilibrium, able to shed the excess water and avoiding supersaturation. The new situation with the magma a little bubbly but not very much is stable: it will continue as long as nothing disturbs it. But a rock fall at the top or a slowing of the overflow will increase the weight below, and the bubbles begin to dissolve into the magma. There is a little bit of pulsing at this time, but with a shorter period of a few minutes. This suggests that the gas formed only higher up in the conduit. This is of course what you would expect if the is less water in the magma: the depth at which it become supersaturated becomes less. Once the gas is gone, the situation is stable again.

The volcano therefore can have two very different modes which are both stable: one with fizz and one without.The change from one to the other is unpredictable. In physics, this can give rise to a chaotic system with periods of constant behaviour followed by a random large change. If you are interested, look up the Lorentz attractor.

The changing eruption does not necessarily mean that the flow rate has decreased. However, the supersaturation of the magma is changing. Perhaps there is less water. There may also be a more prosaic reason. The eruption has added a lot of weight to the area. The pressure in the conduit is therefore a bit higher than before, and this can reduce the supersaturation.

What will happen next? The current situations is unlikely to last long. The long periods without lava suggests the eruption is on the edge, and could easily stop completely. If that happens (not unlikely), the conduit may block, the walls will survive and the government will declare victory and call elections. But if there is still flow from the mantle, then the pressure from below will increase again and the magma will look for another way out. In that case, after a while the rock-breaking earthquakes will restart and the eruption may eventually resume in a new location.

This may well be the end. It may also be the start of something new.

Albert, July 2021

463 thoughts on “The changing faces of Fagradalsfjall: fizz, bubbles and slugs

  1. Well well- it’s done a Lazarus! So whats it’s next plan?

  2. Like others saw splattering but then can’t see any signs of it now.Its not a raw back to life-well at least not yet!

    • One of the feeds is about 4 hours behind. Took me 25 minutes to figure that out.

    • The hell machine have started…
      And Sauron is emerging…

      Where is the link to the Vísir webcam?

    • Raging is maybe not even enough to describe it, the flow is so fast it is leaping into the air on the steep slope, like a bolder in a flash flood, it is a shame few will ever see this, but also maybe a good thing it is in an inaccessible kipuka. I did see a helicopter on one of the lives though, so at least someone has seen this flow.

      I expect the flank of the cone above the breakout will probably collapse, and the volcano will be directed into this direction for a long time now.

    • Sneaky little bugger! I guess that is keeping the lava lake level down a bit making it easier for the high spattering that is happening now not having to pass through a 50+m lake of lava..

    • Actually, it is visible on this livestream, not up close though unfortunatly.

    • Yes, it looks as if it’s found an easier way out than staggering up the insanely high lava shield between the crater and former Theatre Hill, the cone has sprung a leak to the side.

      Good news for the authorities I’d have thought, as Meradalir can confine a lot of lava – we may see some new dams being constructed, as it may be worth doing some work on the south side to divert lava north or east.

    • Tremor shows a peak early morning, before or during the outbreak.
      There might be a hole in the wall.

      Credits IMO

      • RE:”There might be a hole in the wall…”

        It would be helpful if a camera could be placed at a different location to afford a more global view of the evolving shield. I don’t see anything informative coming from any of the current positions other than activity in the vent, and the advance of the flows. Using the most often viewed image as example I’d like to see the opposite side of the cone on its far right.

    • While Ragnar may have “quite a voice”…those weren’t swan songs and he sure ain’t no fat lady! Could the contrarians be tone deaf?

        • My bad. Volatile and unpredictable…clearly he’s a she!

      • Prediction is very difficult, especially if it’s about the future

        Niels Bohr

      • @ Natthagi well, Siggi Ragnar, part-landowner, calls her a ‘she’, so… *shrugs*

        • I do find calling the volcano she interesting, and potentially offensive to some. Women were upset when hurricanes only got given female names. That has now changed.

          I also noticed a post by someone who said hey guys where’s the lava as if it is just blokes who post on here.

          I’m happy with it, but some might not be.

          • I remember when my mum wore hotpants in the 70’s builders would whistle from up the scaffolding I even got to drive a train across the Menei straits because all the railway workers that appeared from everywhere wanted to talk to mum LOL’s. It was a diesel multiple unit allocated to Holyhead locomotive shed Anglesey.
            My mother took it as complimentary.
            I am proud of my mother and so is my father who was away fighting.
            How times change.

          • That raises the question how to recognize female volcanoes from male ones? Anak Krakatau used to be translated as ‘son of Kakatau’. Since the 2018 disaster it has become ‘child of Krakatau’. Shifting the blame?

          • It seems to me that in Icelandic, volcanoes are female, I read/seen that about Katla a few years ago, but I don’t know if the rule is general.

          • “Hey guys” and “you guys” when addressing a mixed bunch is I think an American usage – I remember being a bit pompous with a perfectly friendly bartender over there, regret it now, he probably spat in my beer.

            “Hi, what’ll you guys have?”

            “Well THIS GUY will have a beer, and THESE GIRLS will have a bottle of Zinfandel”

            It’s just their way. When in Rome, do as the Romans do.

          • Well, even with a very feminine Mucha lady of the Stars, some people here think I’m of the male gender. Who am I to disillusion them? XD

          • It would not be unusual to have heard Anak Krakatau referred to as an S.O.B. in general conversation. There’s a combination which throws another light on the conversation.

          • As for Anak Krakatau, “Anak” means child and is gender-invariant.
            “Child of Krakatau” feels like a more correct translation to me.

            In Iceland, some volcanoes and volcanic features get male names, some female names. Is there any method to it, or does it just depend on whoever named them?

          • ‘Guys’ has become an umbrella term for people when it’s used in that context and not meant solely at men – at least by younger people (being people under 50 lol).

        • I like to go with local folklore in deciding whether a volcano is male or female.

          Indonesia: Semuru and Agung are male, Batur and Krakatau are female. Toba is male (the legend around that one is interesting and involves a man who was married to a mermaid or fish and didn’t know it. He found out his son was a merman, insulted him for being a fish, and the wife got mad at the husband and turned him into a lake. Yes, someone from Indonesia on a chat told me this.

          Rainier is male, St. Helens is female, both by the western names and by Indian stories about the volcanoes. Rainier is referred to as “grandfather”.

          Sicilians think Etna is female. Popo is male, I think…

          • The pattern is perhaps size? The larger is male and the smaller female

  3. The flow right now seems to be far, far in excess of 13m^3/s. Most of West Meradalir and much of the narrows has been resurfaced with a couple meters added to the depth. A rough estimate is that 1 million m^3 has been added in the last 10 hours. That equals a flow rate of roughly 30m^3/s.

    That makes me wonder if that is the the new mode and that the average is still 13m^3/s. With the four-day lull, this gushing could be maintained for 2 more days. Then another pause, then another gushing, and so on.

  4. Having Youtube problems again. Constant buffering, even at a measly 480p resolution. If I change resolution it works for a short time and then gets stuck again. It doesn’t just stutter, either, it gets stuck and never seems to get unstuck again by itself.

    Any advice? I’m not running anything else that’s using heavy download pipe so I really don’t know why I keep having this problem every few days.

    • Check if your graphics driver needs updating.
      That fixed all sorts of problems with streaming and gaming several times in the past for me.
      I regularly play World of Warships and look at YouTube lots.
      Quite often the drivers are the silver bullets.
      Good luck.

    • Try clearing your Browser cache of images and stuff (not the important stuff like cookies you wish to keep).

    • It’s only happening with the mbl stream. For some reason that now seems to be demanding more bandwidth at 480p than the RUV Langihryggur one demands at 720p.

      And we’re missing a comment again. Between 18:43 and 19:41 the number went from 187 to 191, but I can only find three comments from that interval (on both pages), Clive’s directly above mine here, 67doug’s response to my drone comment farther down, and Albert’s remarks about Meradalir immediately after that one.

      Odd that there are surface flows in Meradalir but not at the cone, which is fountaining intermittently but not overflowing. Partway by tube and then surfacing?

      • back upthread, comments say lava is leaking from the lower east side of the cone and that’s what’s feeding Meradalir, out of the line of sight of the close up cameras. It was visible on the mbl camera on Storihrutur, but they seem to have replaced it with a panoramic camera which is not very high definition.

      • Twisted One, I have problems (on my tablet) if I leave the Visir webcam playing, then any YouTube video only plays a few seconds before stopping and refusing to play. If I then go back and pause the Visir, then everything plays fine.

        • This was happening with no other videos playing anywhere on my machine, which is, also, much larger and more capable than a tablet.

  5. Faf tremor and drumplots shows the pulsing has come back once again. Every 14 minutes now.
    Not a dull volcano. 😁

  6. The flows in Meradalir are quite impressive. Most of the first dale has been resurfaced and the flows are expanding fast.

  7. What is the height of Ragnar’s cone measured from the base to the top?

    • I questioned the data modeller when the last thickness model was published, and she confirmed my calculation of max 65m above the average lava surface (it’s not even, higher to the south, lower and therefore taller to the north).

    • No, that’s been there for a while. Stays zoomed in mainly now, but it is the one that used to pan down Natthagi.

      • ah, ok, so it is the one that has been hidden in fog for days ?

        • Yes that’s the one. Usually the first one to go.

          • It is up high and the clouds are usually low, so that makes sense 😀

            It is a good viewing point from where it is

  8. The lava flow broke out of the cone and flowed into Meradalir within the span of 10 minutes, flowing around a mile in that time. That is a flow advancing as fast as you can run, likely much faster down the steepest part. The channel must be even much faster still. Funny how it dwarfs the flows from fissure 2 that we all thought were so fast, this thing has really grown.

    • I think the channel was already there. The flow will change again. Everything is constantly changing with this eruption.

      There is still a huge network of underground tubes/tunnels for the lava, who knows where and when the lava will go.

      I am thinking of going back ….

      • I think the rest of the flow field is inactive, the lava tube going to Meradalir before was fed at the same point as the lava rivers, and theres no fume along the trace of the tube. Natthagi was fed by the flow that went out of the south end of Geldingadalir, which also seems to be dead. This new flow is the entire output, I expect the side of the cone will fail if it keeps up. In any case the lava will probably build up a lot on this side maybe even for months.

  9. Wow, quite a blast at 23:42 pm, but yellow-white lava is still gushing from high up on the crater wall, possibly magma has intruded up into the cracks of the cone, and has now found a way to come out. Very spectacular lava-technics.

    • something very unusual is now happening with the cone, as lava gushing out high up on the cone wall is not a normal place for this to happen.

    • Now about 2/3 the back wall of the cone has not cooled down, but is glowing dull red with pinpoints of white showing through. It is almost as if this part is being heated?

  10. It looks like there is actually two points of breakout that merge into that lava river. There is the one that formed first right at the thin weak part of the cone, and sent the first gush of lava, but at some point since then another flow has broken out at a point near the base of the shield, and which merged with the other channel.

    Theres also a glowing lava front actoss the valley, slowly surfacing the whole thing, if the flow rate is still as high as before that is going to fill up to overflow probably this week. Will be interesting to see if the channel can form a tube, or if it is too big.

    • Second breakout seems to have started at 22:22:58 July 10, I wonder if it means a bit more lava is erupting or just the cone is not very stable anymore after sitting quiet for a few days. Pu’u O’o often had sattelite vents when it was fountaining, and so does Etna now, but in both those cases the vents are minor and most of the eruption is at the primary, here the flank flows are all of the lava outside the crater, its not overflowing directly.

  11. The 02:52 am burst was really spectacular from this camera as there was lots of white hot lava gushing up. At one point, the viewer could see a really white hot plume, pushing up from below. I don’t remember seeing such white hot lava in quite awhile.

  12. At 3:18am glowing lava is visible at the right hand base of the cone on the MBL overview camera.
    This is lava directly visible, not just reflected in the fumes, and the spot seems to be growing larger with time, so perhaps the breach has migrated upwards a bit.

    • It looks like maybe there are more breakouts, not just the original one. It looks liek maybe there is a shallow sill that has pushed through the cone, and is breaking out at the surface. I think there was a similar flow but a lot bigger at Pu’u O’o in 2011, proper lava flood that was.

      I expect soon that side of the cone will collapse, its mostly tephra and there is lava flowing under it, it is going to erode very fast.

  13. The leak in the side of the cone is allowing all the flow to go to Meradalir (rather than 2/3rds). The northern part of West Meradalir has gained at least 5 meters in less than a day! In the past 12 hours, not only has the area covered expanded, but the flows from earlier today largely covered by new ones (also lift from below occured). My guess is 2 million m^3 or slightly more in 22 hours for a flow rate of ~30m^3/s.

    At that rate, it would overflow Meradalir in less than a week, but I really, really doubt it will continue at this rate that long.

    • Early estimates for the volume of Meradalir valley were 44.7mm3. With over 2/3rds of the lava so far flowing into there it is a bit surprising that it is not full already.

      Clearly whoever calculated the 44.7mm3 got it wrong.

      • Or the estimate of 2/3 going there was wrong, until now all the biggest surface flows went the other way, Meradalir was constant but the surges went elsewhere. Well until now that is.

        • If the total volume emitted is over 80mm3 and the volume of Geldingadalir, S Meradalir(nameless) and Natthagi is a best around 25mm3, less lava has gone South than North into Meradalir.

          I’d be interested to see what others think on this.

          • The lava has built up a thick and now impressively tall cone/shield, which the models never took into account. I think it was just assumed that the first outflow into Meradalir would become a tube and the vent area would become inactive to feed a longer flow, like often happened at Pu’u O’o. The models I know never predicted Geldingadalir would get filled, let alone overflow in multiple places. Based on the size of the shield I think at least there is as much lava to construct it as has filled Natthagi, and that doesnt include the rootless shield that formed back in May.

        • My estimate of 2/3rds going to Meradalir is not for the whole eruption, really mainly for June and the tube stage. Meradalir did not meaningfully start filling until beginning of May, by which time 20 million m^3 had already been erupted. Meradalir and the slope combined have roughly 40 million m^3 by my estimate or about 60% of the volume in the past two months.

    • How do you estimate those 5 meters? Did you find good reference points on the side or something like that?
      It’s not obvious to me from the covering alone, I would guess less than that.
      That lava goes there very quickly, and is very liquid so it is able to make thin layers.

      • I compared how much the flow level creeped up the dark patch in north West Meradalir, then saw what distance that was in google maps and compared to topographic map. The flow recently has been coming from the other entrance, so built up in southern Meradalir and left the north comparatively slightly depressed. The lava front might well have only been a meter or so thick

  14. The wall is definitely collapsing, it seems to have actually cut off the flow a bit and is sliding out. Might be another big flood of lava down that way in a few hours. I wonder too if without a lava lake the vent will go back into geyser mode, or even a paroxysm.

    • Grimsvötn is in constant inflation mode non stop

      Do you think the next eruption will be long enough to form a caldera surtsey Island?

      Grimsvötn is the only constantly inflating volcano in Iceland

    • Brilliant, thank you. This is where we are missing GutnTog. He would have climbed over hell and high water to get a view of the breach.

      • Is it possible that that exit hole could actually be a new vent ???

        If it was an exit hole, would it not get bigger and collapse the crater wall ?

        • It is a leak from the main vent, and one that I think has been in existence for some time

          • Note that the flow from the leak is smooth, there are no gas outbursts. That suggests to me it’s from the degassed pool on the cone.

        • It actually is collapsing the wall, just not catastrophically. The wall clearly moves out from its original position when I looked at it yesterday, but I dont know if it has continued to do so since. Either way it is shallow. I expect if it was actually a new vent it would be fountaining just as much as the one in the crater, but there is no fountaining, there is not even dome fountaining which suggests there is no vertical motion at all.

  15. I notice some small quakes in the system on the Grindavik Highpass chart.
    I wonder what’s going on below? They appear to have happened from 4km up. To my untutored eye they do not look like a conduit collapse. On the contrary, they strike me as rock-cracking signatures from extension. More conduit opening up?

    • They are at svartsengi, two small quakes with aftershocks. I think they are on the Reykjanes fault: right location and depth. That makes them aftershocks of the M5 quakes that started off the current events.

    • Stunning video, probably the best I have seen so far.

    • That vigorous upwelling in the escaping lava stream looks like it could come from a lava lake – suggesting a hidden lower feed from the vent. Or even an off-shoot riser from the main conduit?

    • Great video… showing how fluid this lava is… and bright yellow in daylight
      Its well over 1200 C perhaps.. and as fluid as Hawaiis lavas. This is the hottest lava ever seen in Iceland by modern cameras, even a bit hotter than Holuhraun. Really really fluid …

      • Probaly is as fluid as Halemaumau lavas and even Nyiragongo

      • I wish that someone could get in there with a calibrated IR device and measure the actual temperatures. The camera keeps adjusting itself for the lumens and you cannot get an accurate sense of the lava temperatures.

    • I have never seen lava roll like ocean waves before! Even with a breaking wave on the vent wall!

    • So much goodness here. I heard an interesting tidbit about the thin skins of solid lava that Slough off the vent sides and fall back into the maelstrom. The contact with the walls is less because the inner surface is composed of tiny bubbles, like Aero chocolate. When the outer skin hardens and is more dense, the weight overcomes the strength of that layer, and it shears off.
      There’s a good bathtub ring emerging, showing the level that the lava can now reach, and the tide line about which the level sloshes with the waves from the degassing.

    • First time I have ever seen lava churning around in a circle at the base of the flow. Very nice video.


    Grimsvötn looks tired… less seismic action now… perhaps magma chamber stopped its expansion?
    It coud also be that Grimsvötn is hotter and gives off more earthquakes now

    But Grimsvötn keeps inflating and filling with magmas according to the GPS… perhaps the system is well heated now and gives off less earthquakes. GPS maybe the only way to measure Grimsvötn for now.
    Grimsvötn keeps inflating

    • It is interesting behaviour. It seems to me that Holuhraun may still have an impact. It took some stress out the area and Grimsvotn is affected.

    • Grimsvötn is still inflating constantly…as magma is pushed into the volcano
      The caldera arera have risen a meter since 2011 I think

    • Grimsvötn is one hell of a much more massive system than Fagradalshraun
      But with large established magma chambers… its basalt are a bit more evolved than Geldingadalir
      Grimsvötn remains intensely geothermaly alive, very high SO2 emissions where measured one year ago

    • Why the far side of that edifice has no interest for people doing the recording puzzles me. The nature of that portal at the base and the manner in which the effluent is leaving is relevant.

        • Yes. We have an amazing range of cameras both present and past and a wonderful view of the activity. But I too have been wondering for some time about what we were missing. The cameras are of course mostly placed in accessible regions, i.e. closer to the coastal road. The back view is also the most distant location to put a camera. With unlimited funding you would put up cameras all around the entire flow field. In reality, choices have to be made based on best guesses what may happen next. Volcanoes may not always follow those guesses

          • Indeed you are right. Although the “behind the wall camera” has puzzled all of us I am sure 🙂

            At this point a camera at the east exit of lower Meradalir seem to be in order as well… That now is very likely then next place where new area will be covered.
            In a fairly hard-to-predict way, once through that exit, due to the shallow slopes in that area. It might even back up significantly leading to a rise inside Meradalir to access the next higher exit of Meradalir as well (southeast, I think).

  17. It looks like about 3 mins for the lava flow to travel from a gushing episode to the Miradalir valley. Take a look at the panorama camera around 22:40m pm timestamp in the video and beyond. It is unmistakable to see the gush and then the very hot lava impulse rush into the valley about 3 mins later.

    • 3 min to go 1 km more or less, so flowing at 20 km/hr on average. I think it is flowing way faster than that when it plunges down the steep slope though, and it is pretty slow at the vent, maybe about walking speed.

      • Watching the lava flow splash down the channel, it looked easily 40 km/hr or more.

        • Would not be surprised, such speeds have been measured in Hawaii on less steep slopes. Really this is probably as fast as is possible for the lava to flow, the cases of faster flows than this are also with enormous eruption rate, like at Nyiragongo or Mauna Loa.

  18. A real bummer the weather has been so bad recently, so probably they still have not been able to do proper overflights for a new 3D Scan to determine the flow rate. Would have been nice to have a data point close to the first eruption pause, to see whether the flow has since changed (the average flow rate, that is).

    I wonder whether they can use the radar satellites for this, that data looks high enough resolution for this kind of application. That would give a data point almost every day. I hope that company has continued to record the area, and that this data makes its way to someone who does a proper volume analysis.

  19. I think this video was not posted yet, apologies if it is a repost:

    Very spectacular footage from Saturday evening. it shows quite a few things:
    * Another spectacular view of the lava waves inside the crater during an reuption event
    * A very nice overview of the area north east of the crater
    * It seems that at that point in time, Meradalir still had not quite 10 meters to go until reaching exit level (so a few days worth of lava at the usual rates) – but that was before the huge inrush from saturday night / sunday
    * Some VERY scary views of air traffic (both helos and aircraft) at the same/similar altitude and far too close to the drone. As much as I love these videos, this is *extremely* concerning. It would be terrible to put a blanket no fly zone for drones (after all they can fly in weather that real aircraft cannot operate in in that area), but the risk is becoming serious so some smart system should maybe be put in place. (Altitude separation? East/west split of airspace? Even-numbered hours for helicopters, odd-numbered for drones?)

    • From what I can gather, A large portion of the SE side of the volcano is still inflated from the last period of the unrest. There is a ring of pretty strong inflation over all but in the other regions it still hasn’t overcome the total subsidence from the last eruption. I think that the shallow chamber is losing some pressure while deeper system is gaining pressure

      • Was re-reading the old Carl article (Taal eruption update) and he was discussing the possibility of sill formation at Taal.

        That seems possible given the description (overall extension, middle subsiding).

        These recent weeks the S02 emissions are much higher than they were in the 2020 eruption.

        • I must have been reading your mind when I just posted my comment below.
          Sorry if I jumped on your observation.

          • It was actually Carl’s observation a year and a half ago.

        • I know about vertical deformation but I am completely unaware of the horizontal deformation which plays a key role in decoding situations like this. I am sure Phivolcs are doing everything they can but I would like just a little more information concerning my current muse

      • Or, the magma chamber is expanding laterally..possibly a developing sill? The reduced pressure as magma escapes the primary chamber might explain the observed deflation/inflation pattern?

        • A large shallow caldera somewhat suggests prior sill collapse, especially if a lower magma chamber is still intact. Kind of like a fallen souffle.

          (completely speculating here and not a geologist)

    • Wasn’t there a camera on that hill in the foreground at some point? Close to that measuring equipment? That would be a prime vieiwing location now.
      Interestingly, a helicopter is parked in the lower part of the hill in that video. Might be just a tourist trip, however.

      • Yes…at least two that I can remember. One was a Visir camera….now located as a closeup of the cone’s south side, and the other was an MBL cam – not sure if this one was sacrificed or was relocated too.

      • Langihryggur N still camera, @ 1930, 1940, 1950 and 2040, 2050, 2100.

        What kind of optical illusion would create the visual of the rock face moving back and forth? This is seen just about where the new outflow is.

        • sorry…should have been posted below as a stand-alone post.

  20. Based upon the heavy fog, but persistant orange glow in the two cameras, I am guessing that we have a torrent of lava escaping the east side of the cone, near the base, but I wish the fog would clear.

    • I mean it’s hard to tell what the Point-of-view is, but right at the end they pull back and I think you can glimpse the original exit to the left. Also the foreground of this shot has the smooth ‘mini-shield’ look that has been visible on the still cams sometimes.

      • Looks like a video from May, the cone is a lot wider than it is tall where back then and also in this video it is very steep and prominent.

        • I think you’re right…also just noticed the sky is blue, which means it can’t be recent 🙁

          Please ignore the above…

    • This looks like one of the older vents back in march or april. Note the open ground very close to the cone, which is not the current situation

  21. The seismograph pattern is quite distinctive at the moment. There is a long burst lasting 2.5-3 minutes, followed by a minute of silence and a short burst lasting 1 minute. After that there is 19-20 minutes of flat lining followed by the next burst. This has been fairly consistent over the past 24 hours. I am wondering whether the short second burst has to do with the flow along the side

    • That sort of period reminds me of the bifurcations of ‘dripping taps’ which seems to be quite a common chaotic attractor. Dib-dab – pause – dib-dab pause. Its the one that typically comes after the regular monotonic dripping (as you increase the flow). Soon more complex modes arrive which quickly turn chaotic.

      • I tried this experiment in our kitchen. Sadly it didn’t work. Apparently we have a non-drip tap

        • Its quite tricky to get the right rate between single drops and a continuous flow. The chaotic drop regime is even harder to hit. It also takes several seconds to stabilise.

        • The unfortunate fact is that the washer has to be ruined by over tightening or plain old wear and tare to get a good authentic tap drip, IE:- Dib-dab – pause – dib-dab pause
          Does that mean the Volcano is suffering from a worn or damaged sealing washer?
          This comment requires VC “tap dripping study group” pier review ASAP LOL’s

    • Crater walls seem to be getting a lot thinner towards the exit (SE) side.

    • Thank you very much Doug for posting this. The last 3 days drones have proved an invaluable tool for staying on top of volcanic changes and for providing a better perspective on the overall state of a volcanic eruption. I see them becoming an indispensable tool for the vulcanologist, not to mention that humans can safely view the action from a distance.

      • I wish I was there to make my own video’s, but when I find or see good ones, I will share them here 🙂

    • That sloshing lava lake exerts extra pressure onto the cone walls, by which they can collapse.

    • Vesuvius is watched more closely than my granddaughter needing to use a public bathroom. I’d be looking to the Italians for that one.

    • Technical issues, lack of power, who knows…

      Also, the Panorama cam from MBL is frozen for two days now. Sadly, since that is the only one that sees a little bit of what is going on north of the crater. Probably those solar cells did not really generate that much power these days 🙂

  22. Interesting video taken by a couple, the woman fulfilling her desire to see a live volcano. At 5 min 58 secs into the video, you can see a camera shot of the leakage from the cone, but what is eye catching is the artesian gusher of very hot lava issuing up, some distance down the flow from the cone. Apparently there are at least 2 leaks, one at the side of the cone, and the other at this point, which is exhibiting considerable pressure, to push the lava up into a mound.
    Taken on July 10th and 11th.

    Is this a 2nd leak?

  23. I still think the main “hole” is a new vent. The other side of the crater, the lava field is still being fed as can be seen by the steaming all round, especially at the edges.

    The ‘new’ leak seen by Randall looks to be coming from the old tube network.

    Whatever is going on, it is more complex than we can see from the views we have

  24. On the RUV Langihryggur webcam, 20.22 onwards there’s a smidgen of lava visible at the base, and a good fountaining event follows.

  25. As one could expect Chad was right about the wall not holding up to the leak but the partial collapse has lowered the lava lake and made the fountaining quite impressive again.. would really love some good pictures/video from that side of the volcano to see the extent of the collapse..

    • Hopefully one of the live camera operators will move a few cameras over there as I would assume this is going to be the main direction of the flows for a while now.. building on that shield shape slowly but surely.. Have to admit I had been wondering when it would make some kind of break that way because that wall was as lot thinner than the other directions and the lake was just getting higher and higher as it built up the south side..

  26. Langihryggur N still camera, @ 1930, 1940, 1950 and 2040, 2050, 2100.

    What kind of optical illusion would create the visual of the rock face moving back and forth? This is seen just about where the new outflow is.

    • No illusion. The rock face is being pushed up by the flow underneath. At 21:00 you can see the the lava flood our from underneath. The cone is partly build up from spatter and may be quite low density. It floats.

      • Wow….so…that whole face can (and from the sounds of it – would) just give way? A number of good, strong bursts of lava could simply finish it off?

        The valley would fill as quickly as the vent can have lava pushed up…unless the volcano decides it wants to do something different? It would be like Gollum (from the old days)…just “continuous” flowing lava

        Yet another dimension to the eruption!

        “Camera needed, Aisle 3”

  27. The wall is breached sufficiently to just allow the lava to pour out now

    • ooh ooh, flow was clamped around 23:38 pm and stopped.. something seems to have squashed this channel?? The flow suddenly went dark.

      • Definitely clamping going on.. the flow to the right suddenly turns dark, after about 1/2 way through the gushing episode, the gas disappears, and suddenly dark over the region which showed some lit gas being expelled.

      • I think I know what is going on. The lava is below the banks of the channel it created and cannot shine to the camera which is at a very low oblique angle. When the channel fills up and starts to overflow, the lava becomes visible. When the level drops, the lava drops below the channel bank and the light goes out.
        It is not being clamped, the lava just could not be seen anymore by the camera

    • I’m guessing that is more like a deep pool or obstruction causing the flow to loft up. In later videos, it disappears.

        • I dunno. Watch the middle of the frame, the RUV Langihyggur camera. The cone appears quiet, yet something is fountaining there in the center of the frame.

          That said, if this is a new exit, it is not exactly in line with the others.

          However, the camera is very far away, making it impossible to know what the heck is happening there. But it is interesting.

        • I don’t agree, because the video of the couple showed something acting artesian while things were flowing from the cone.

          • If it was a deep set vent it would be fountaining, just like the main vent. This was just a dome fountain, which can happen over lava tubes, there has been a few such times in the last 2 months this activity has fooled people already, but a real vent would fountain not just well up.

  28. Tremor and LF earthquakes are rising at Taal, with the tremor getting longer it would seem that the more magma trying to reach the surface. More interesting still is the relative decrease in gas emissions despite the clear increase in volatility with the system.

    • Yes. This is not a calm and quiet volcano.

      Excerpt here

      TAAL VOLCANO BULLETIN 13 July 2021 8:00 AM

      In the past 24-hour period, the Taal Volcano Network recorded one hundred seventy-one (171) volcanic earthquakes, including thirteen (13) low frequency volcanic earthquakes, one hundred fifty-seven (157) volcanic tremor events having durations of one (1) to ninety-seven (97) minutes, and low-level background tremor that has persisted since 07 July 2021. High levels of volcanic sulfur dioxide or SO2 gas emissions and steam-rich plumes that rose one thousand five hundred (1,500) meters before drifting southwest were generated from the Taal Main Crater. Sulfur dioxide (SO2) emission averaged 6,134 tonnes/day on 12 July 2021.

  29. Moderators:
    I put a typo in my email address again (post awaiting moderation)

  30. At 01:36 am, can someone tell where most of the glow shining into the fog is coming from? The cone itself, or a flow to right, which is the leak? See and the middle screen on the right hand side.
    From what I can tell, it seems that the glow is coming from the right hand side of the cone, not the cone itself.

    • Rats, the cone went into eruption and the glare from it is overpowering. I guess a person has to wait a few minutes to carefully see this.

  31. So, inquiring minds want to know… at this point, how much longer till the ‘Road Is Toast’. ????

    • The main lava flow isn’t spilling S towards the coast road at the moment and it could be a long wait until it does. So don’t hold your breath.

    • Don’t know. Lava could be flowing under the lava crust. The lava is still thickening up in Nátthagi.

      • On the camera there is no evidence of any thickening in Nátthagi for several days, atl east for the southern half of that lava field, is there some other data somewhere?

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