Katla: a retrospective

/ 05/07/2023

After our ‘quantum Katla’ post, it is now time to return to the real Katla. For in the real world, Katla has been showing unusually strong shaking. It turned out that Henrik had already done much of the work for us. Here is a resurrected post from the dungeons of 2012 where young Henrik keeps our Katla feet firmly on the ground. It includes an addendum on the current activity.

Rest in peace, Henrik, and when Katla blows we will raise a glass to you. (Clive, 2019)

Part I

Katla is a relatively young volcano which like so many Icelandic volcanoes formed when Iceland was covered by ice. Hence it is a tuya, steep-sided with a broad, flat top. Like other large Icelandic volcanoes, it has a very large summit crater described as a caldera, but one that did not come about as a result of the collapse of the volcanic edifice into an emptied and very large magma chamber as happened at Mount Mazama a.k.a. Crater Lake in Oregon, at Krakatoa or at Long Valley.

Fig. 1. Herðubreið, a subglacially formed tuya with steep sides and a flat top. Post-glaciation, erosion has made the sides less steep and a small post-glacial cone makes the top appear less flat than it once was. The similarity to Katla, once you allow for the vast differences in size, is obvious. (extremeiceland.is)

One of the keys to understand what goes on at Katla is to have an idea of what lies beneath the up to 700 meters thick glacier that covers her crater/caldera. In schematic representations of Katla, a magma chamber at the very shallow depth of three to five kilometres is often displayed. From reading descriptions of other volcanoes that have suffered caldera collapse or looking up a general definition of ”caldera”, it is easy to assume that Katla too must have a magma chamber that spans the entire width of the “caldera” and which, “once-upon-a- time” collapsed to for the present-day caldera. Nothing could be further from the truth, but alas, there is no direct information available that accurately describes what Katla’s magmatic system, the true volcano, looks like. We have to fill this gap ourselves.

The first thing to do is to look at what she has done in the past. If we look up her “Eruptive History” on the Smithsonian Global Volcanism Program website, we find that Katla is listed as having had 27 eruptions during the period Iceland has been settled by humans, some eleven centuries and counting. Of these, only the larger eruptions seem to have been registered prior to the middle of the 20th Century. Thus the 27 eruptions are divided as follows: Two VEI 0 (1955 and 1999), three VEI 3, fourteen VEI 4 (including the AD 934 “Eldgjá fissure eruption”) and four VEI 5 with a further four not assigned a VEI number. Of the four unassigned eruptions, one is listed as “subglacial, lava flows” and three as “subglacial, explosive”. Please take note of the dearth of smaller eruptions, VEI 0 – 2, as this is important and something we’ll return to later.

From this information, it is clear that Katla cannot have a single, caldera-sized magma chamber because such a chamber would contain several tens to even hundreds of cubic kilometers of magma, which in turn would have led to far larger eruptions. None have occurred. Since VEI 5 is assigned to eruptions that eject between 1 and 9 cubic kilometres of Dense Rock Equivalent (DRE) explosively, and Katla’s VEI 5 eruptions are remarkably consistent at between 1.2 and 1.5 cubic kilometres, anything much larger than some 3 – 4 cu km is rather out of the question. A caveat – given the area covered by the crater/caldera, there could be more than one such chamber responsible for her eruptions, in which case it would be fair to ask the question if Katla really is a single volcano or if not a description of her being several volcanoes rolled into one would be more accurate.

If we look at her eruptive history prior to Iceland being settled, deduced by tephrochronology – ash layers deposited being identified by their physical properties, such as chemical composition and grain size, as belonging to Katla and from the size, distribution and time derived for each individual layer of tephra, an eruption responsible for it is inferred – we find that there have been a multitude of eruptions, but only a few of which have been assigned a VEI number. Interestingly in every such case a VEI 3 or 4 has been deduced. Anything much larger must have left such extensive deposits that such a huge eruption cannot have escaped detection, hence we can conclude that no explosive eruptions larger than a small VEI 5 have ever occurred at Katla.

There have been two exceptions to the rule that Katla’s eruptions normally are in the VEI 4 range volume-wise. Both originate on her NE flank, outside the crater/caldera. Around 5550 BC, Katla was the source of the 5 cubic kilometres “Hólmsá Fires eruption” lava flow. In 934 AD, the four times larger “Eldgjá eruption” spewed forth some 18 cu km of lava and five cu km of tephra, or ash. Even if the total volume erupted in 934 AD, about 22 cu km DRE, is on the order of 50 times greater (25 to 200 times), a lowly “VEI 4?” has been assigned.

As the underlying causes and processes that drive “regional fissure eruptions” are vastly different and as they happen very rarely, seemingly with a time interval measured in several millennia in the same-ish location, fissure or rift eruptions should be considered separately – even if the visual appearance of the Katla crater/caldera suggests that a fissure eruption has at some point in the distant past intersected it. They are mentioned here because an article such as this cannot fail to do so, nor can it fail to give a reason why they are not included in the discussion.

Earlier I mentioned the apparent absence of small eruptions from her eruptive record with only two “possible subglacial eruptions” in 1955 and 1999 listed, to which can now be added the equally suspected or “possible” July 2011 subglacial eruption. As I write this, it seems that there may have been yet another, very minor hlaup. That such eruptions were not noted in earlier days is not surprising as the very small hlaups they resulted in were local nuisances rather than regional catastrophes of a major Katla jökulhlaup and would not have been seen as important enough to be recorded, even had they been observed. But how frequent could this type of small eruption be?

Fig 2. Seljansfoss Waterfall during the 2010 Eyjafjallajökull eruption (Binaural Waves Blogspot). Notice evidence of several minor eruptions on the mountainside above the waterfall.

We know from the 2010 Eyjafjallajökull eruption that it was preceded by two fissure eruptions at Fimmvörduhals that intersected each other. If we look at the topography and geography of Eyjafjallajökull, we can see many areas of monogenetic cones. This indicates that eruptions of the Fimmvörduhals type greatly outnumber eruptions at the main vent. At Askja, a similarly sized volcano albeit glacier-free and with a slightly smaller summit crater/caldera, there have been six small eruptions since the great eruption of 1875 and many prior.

Of the 24 eruptions (not counting the AD 934 Eldgjá fissure eruption) listed before it was realised that there were smaller eruptions that would only show as minor jökulhlaups, 20 are listed as VEI 3 or higher and three of the four not assigned a VEI number are listed as (subglacial and) explosive. At least 17 of the 23 explosive eruptions have been assigned a VEI of 4 or 5. The eruptive record of Katla thus indicates that in order to break through the up to 700 meters thick Mýrdalsjökull glacier, an eruption would need to be at least as powerful as to merit a designation of VEI 3. Thus – the reason for the dearth of smaller eruptions observed is that they are not energetic enough to break through thick glaciers such as Vatnajökull or Mýrdalsjökull to be visually obvious and the minor hlaups resulting have been much too insignificant to have been considered as a result of an eruption that never was seen.

Fig. 3. Pits formed by melting from below in the Katla glacier, summer 2011. The glacier was still covered with tephra from the Eyjafjallajökull eruption which made such features stand out unusually well. (ModernSurvivalBlog, picture may originate with Icelandreview)

With the advent of aircraft, it was noted that there were pits in the glacier as if it had melted from below and the collapsed to form an ice crater. These pits are relatively numerous and vary in size. They have been explained as due to either strong hydrothermal activity or, in the case of the larger ones, as the result minor subglacial eruptions.

The obvious conclusion is that in the case of Katla, small eruptions of the Fimmvörduhals type far outnumber the bigger, recorded eruptions. This is vital for understanding how a volcano such as Katla is built and works.

Let us for a moment return to what I like to call “Katla’s defrosted twin”, Askja. Here we can see, side by side, the effects of the two types of eruption. In 1875 she had the big VEI 5 eruption, about four times as great as Katla’s historic VEI 5s, that would eventually form lake Öskjuvátn. Here we have a magma chamber where magma collected over time, partially re-melting and absorbing the chamber walls which together with fractionating led to the body of magma collected being far more silicic than the basalt injected into the chamber, which provided the heat or energy for the process. This went on for centuries, quite likely millennia as GVP lists the preceding very large eruption at Askja as having occurred about 11,000 years ago, until a final basaltic intrusion was energetic enough to unbalance the magma chamber and the big eruption of 1875 followed. Please note that both before and after, there have been many smaller, basaltic eruptions that have evidently bypassed the main magma chamber on their way to the surface, one of which caused the miniscule crater Vítí located immediately north of Lake Öskjuvátn

Fig. 4. “Katla’s defrosted twin”, Askja. Aerial photograph inside and above the Askja caldera with Lake Öskjuvatn and the miniscule crater Viti barely discernible on the near left-hand side of the lake. (uwmyvatn blogspot)

This too is what I believe must have been happening and is going on at Katla. Sturkell and his co-authors in their 2009 paper “Katla And Eyjafjallajökull Volcanoes” note that the products of Katla’s eruptions are bimodal, comprising alkali basalt and mildly alkalic rhyolites “with intermediates very subordinate”. One, or possibly more magma chambers where magma collects, fractionates and grows more silicic, a process that takes hundreds if not thousands of years which is why more than one magma chamber seems to be required in order to account for the relatively frequent eruptions of Katla, until there eventually is an eruption of “mildly alcalic rhyolites”, accompanied by tens to hundreds of smaller, alkali-basaltic eruptions which due to their location under the ice in a watery environment, gouge out small craters and fill in the bigger ones with mostly small, broken fragments of lava, piles of pillow lava or even small lava flows or easily eroded cones. When a big eruption occurs, the glacier first closes the wound, then the crater gets back-filled with loose rubble which gets pasted over with more solid lava flows from later eruptions.

This process has been going on for as long as Katla has existed. Not only has this constant remodelling inside the crater/caldera left a kilometres-deep zone of clastic, i.e. broken or fragmented, rock mixed with water, it also in my opinion explains how the caldera was formed in the first place. This layer extends down to not much above the roof/-s of the magma chamber/-s. As freshly injected basalt from the mantle makes its way up, it will eventually encounter this water-rich zone and result in intense activity, hydrothermal at first, and if the intrusion continues, hydromagmatic. It is primarily this activity we see when we look at the tremor charts of the SIL-stations surrounding Katla, in particular the one located at Austmannsbunga, on the north-eastern crater/caldera wall.

In the next instalment, it is time to take a look at Katla’s neighbours Eyajafjallajökull and the Gódabunga “cryptodome” and try and separate their activity from that of Katla so that we can finally figure out what she may have been up to over the last few years and how likely an eruption in the near future could be.

Part II

It is now time to have a look at what’s going on and try to paint a coherent picture of what she actually is, is up to and able to do, but first let us recapitulate what we found previously:

  • There is a general interest in Katla because she is and has been regarded as a very dangerous volcano by generations of Icelanders.
  • The presentation of Katla in media is skewered by vested interests ranging from scientists who hope to increase their professional and/or public standing, people trying to cash in on the interest generated such as journalists and bloggers, and finally, there are people trying to increase their standing within the subculture of doomsaying and alarmism.
  • Katla is a massive but relatively young volcano, located on the MAR, and formed when Iceland was covered by glaciers.
  • The records include two large fissure eruptions on the NE flank of Katla; the prehistoric 5 km3 Hólmsá Fires of 5550 BC and ~22 km3 Eldgjá eruption in 934 AD. In historic times, the 1100 years or so that Iceland has been settled, there have been 27 listed eruptions (28 if the inferred minor subglacial 2011 eruption is included), 23 of which have been explosive.
  • Of the 23 explosive eruptions, three have been assigned VEI 3, thirteen VEI 4 and four VEI 5.
  • The four VEI 5 eruptions are remarkably alike in size at 1.2 – 1.5 km3, which is at the upper end of what Katla probably is able to do but at the very lower end of VEI 5 eruptions.
  • Tephrochronology (in some cases complemented by radiocarbon dating) has identified a further 103 eruptions going back ~8,500 years, and in the few cases where a VEI has been assigned, none have been greater than a VEI 4.
  • Katla does not possess a caldera-sized magma chamber.
  • In order to account for the great number of explosive eruptions which involve more evolved magmas, Katla could have more than a single magma chamber.
  • The available evidence suggests that in order to break through the up to 700 meters thick Mýrdalsjökull glacier, an eruption must be at least a substantial VEI 3.
  • Direct and (primarily) indirect evidence suggests that smaller eruptions, mainly basaltic VEI 0 – 2 eruptions are severely underrepresented in her eruptive record and ought to exceed the number of observed eruptions.

Fig 5. Mýrdalsjökull showing the main glacier outlets, directions of jökulhlaups and areas affected. E – Entajökull, S – Sólheimajökull, K – Kötlujökull, M – Markarfljot, Ss – Sólheimasandur, MS – Mýrdalssandur. Eyjafjallajökull is to the left and the smaller glacier above is Tindfjallajökull (adapted from Google Maps).

The greatest danger from Katla comes from the very quick and extensive melting of the glacier caused by large eruptions which results in destructive jökulhlaups. There are three major outlets from the glacier: Entujökull to the NW that empties into the Markarfljot river and valley north of Eyjafjallajökull, Sólheimajökull to the SSW that empties onto the Sólheimasandur and finally, Kötlujökull to the SE that empties in a great arc east through south onto the Mýrdalssandur. What ought to be prime farmland and in fact once was settled, is nowadays an unsettled wasteland because of the devastating jökulhlaups unleashed by Katla. This is the true reason why Katla is considered to be such a dangerous volcano.

The fact that one often comes across the reference that in the days before the Hringvegur (ring road), “people were afraid to traverse the Sólheima- and Mýrdalssandur because of the frequent jökulhlaups” is another indication that smaller and unrecorded eruptions that cause only minor hlaups are far more frequent than the 40 – 80 years often given as the interval between main, and thus visible, eruptions.

Fig. 6. The foundations of the old bridge across the Múlakvísl river destroyed by the July 9th 2011 jökulhlaup are visible to the left. The new bridge was laid down a week later. (photo John A Stevenson, GVP website)

Apart from the postulated connection between the Eyjafjallajökull and Katla volcanoes, one question that always crops up is the Goðabunga cryptodome. Many volcanologists maintain that it is a part of the volcanic system of the Katla central volcano. Others, notably Sturkell and his co-workers, claim it is part of the Eyjafjallajökull volcanic system. In order to shed some light on this issue, I asked our own GeoLurking if he could make a plot of all the earthquakes from 1994 up to and including the 2010 Eyjafjallajökull eruption. The results are quite clear and do throw up a surprise:

Fig 7. E-W cross section, view from south, through Eyjafjallajökull, Goðabunga and Katla. Plot by and courtesy of GeoLurking. The “lines” formed at approximately 5, 3 and 1.1 km at Goðabunga and Katla are most likely artefacts caused by quakes being assigned a poorly defined depth. The latter, 1.1 km, is the default depth assigned by the automatic system in case it cannot compute a depth within the predetermined level of certainty and unless they are manually checked, which is not the case of every quake, automatic depth remains uncorrected, hence these artefacts.

From this cross section, it is quite clear that there is no connection between the Eyjafjallajökull volcanic system and Katla. Eyjafjallajökull has its own, well-defined feeder system from the Moho (first molten layer beneath the Earth’s solid crust) as does Katla, thus they are wholly independent of one another. As can also be seen, albeit not as clearly, Goðabunga too seems to be independent of either Eyjafjallajökull and Katla, the ramifications of which will be the subject of a later post by Carl. Sufficient to say that when we contemplate what Katla herself may be up to, we must differentiate between activity at Goðabunga and activity at Katla. Once we do, we see that while Goðabunga is more or less continuously active, Katla operates in bursts and seems to be most active during summer and autumn when the ice cap is at its, relatively speaking of an up to 700 m thick glacier, thinnest.

Fig 8. Activity post-Eyjafjallajökull. Activity at Eyjafjallajökull is minor and has to do with the system settling down after the end of the eruptive phase. Note that at a depth of 0 to 5 km or so, there seem to be three separate areas of activity at Katla. (Plot by and courtesy of GeoLurking.)

After the Eyjafjallajökull eruption, Katla seems to have entered an active phase with a suspected subglacial eruption on July 9th 2011 and several pits or craters forming on top of the glacier. This activity seems to be localised to three main areas within the caldera:

Fig. 9. Earthquake activity at Katla July 9th 2011, the day of the jökulhlaup and suspected subglacial eruption. Both the 1823 and 1918 eruptions occurred close to but just east of this area. The 1823 eruption occurred close to the easternmost red spot while the 1918 eruption was roughly at the rightmost dark blue spot below it. (IMO)

Fig 10. Earthquake activity at Katla July 17th 2011. (IMO)

Fig. 11. Earthquake activity at Katla July 21st 2011. The 1755 eruption was situated in the same area as the three overlapping orange spots.

As can be seen, there are at least three distinct areas of activity inside the caldera with the one associated with the inferred July 9th eruption well to the south. The pits formed in the glacier also align with these three areas, albeit the pits to the northeast seem more drawn out along the caldera wall and not over the center of activity. These three areas seem to tie in with the three areas of activity noted in fig 4 as do the locations of three of Katla’s major eruptions. Thus there is not a single vent, but at least three at surface distances of approximately 5 to 8 km from each other. It is equally likely to judge from Fig 7. and Fig 8. in conjunction, that at great depth, they do have a common source.

I will now present you with my personal view of Katla, but do not be afraid to disagree or draw your own conclusions (within reason please, no Katlatubos here):

Katla is a young volcano and far more active than has previously been thought. Unlike the similarly aged but much less active Eyjafjallajökull, Katla has had more time to develop her system of sills to the point where they are fewer in number than they originally were but have a substantially larger magma-carrying capacity and approach or may have reached the point where they can be considered magma chambers proper. Since cooking evolved magmas takes a long time, usually millennia in the case of cubic kilometre-sized silica-rich magmas and at the very least many centuries for intermediate magmas, it is highly likely that Katla possesses several pockets of magma capable of eruptions ranging from high VEI 3s to small VEI 5s. Not only do the times between such eruptions argue this, their wide spread of location within the caldera does so too.

The most common type of eruption at Katla is the small, subglacial eruption of a few tens of millions of cubic meters of basaltic magmas. These eruptions are not energetic enough to break through the very thick Mýrdalsjökull glacier and the only proofs of their existence are intense earthquake swarms followed by minor jökulhlaups and later observations of deep pits or craters, sometimes water-filled, in the glacier ice. My guesstimate is that there may be many such small eruptions over any given ten-year period, and possibly in the case of a period of high activity, there may even be more than one in a single year. By back-tracking and investigating old accounts over the past few centuries of jökulhlaups in the area not associated with visible eruptions, it ought to be possible to identify many of these minor eruptions.

While a larger “proper” eruption of Katla in the VEI 3 – 5 range cannot be ruled out, I find one unlikely at present as the current activity mostly is in areas already depleted of evolved magmas by geologically speaking very recent major eruptions. Also there is little sign of the uplift required on GPS. If one were to occur, the odds for one towards the upper end of what Katla is able of ought to be better in the Eastern to Northern parts of the caldera.

Finally, what we do see when we look at SIL-stations such as Austmannsbunga, located on the NE caldera rim (not a coincidence, see above), is hydrothermal activity following a period of possibly still ongoing magmatic intrusion and not signs of an imminent, large eruption.

Fig 12. Hydrothermal activity at Katla as shown on the Austmannsbunga SIL (IMO) (Source: https://icelandgeology.net/?p=3291)

I’m sorry to be such a boring old fart, but if this is unsatisfactory, start looking for intense earthquake activity at some 25 – 10 km depth, showing on the IMO map for Mýrdalsjökull as being in the Eastern to Northern part of the caldera, activity that shows a clear upwards trend and spreads when it reaches depths approaching 5 km!

HENRIK, May/June 2012

Addendum

Henrik wrote this in 2012, after the burst of activity at Katla in the summer of 2011. It is now 2023 and we again had an earthquake swarm at Katla. And again it happened in summer. The activity occurred on 30 June, and was all shallow but far larger than might be expected of normal summer activity caused by ice melt. The strongest earthquake was M4.4 and around 10 quakes were M3. Not huge, but significant.

The swarm continued events from 4 May when there was an earlier swarm in the same general area. That swarm was a bit stronger with three quakes of M4. It briefly caused the status of Katla to be set to ‘yellow’ before returning to ‘green’ which it still is. That sequence was rather uncommon for early spring, normally a quiet time for Katla! Katla comes to life in summer. The last time a similar (albeit weaker) swarm occurred in Katla was in September 2016.

Was there any sign of an eruption? If we look at the tremor plot, a bump in blue line is evident on June 29. It is weak but otherwise similar to what was seen in 2011. The peak frequency of 2-4 Hz can be associated with glacial floods, i.e. increased ice melt. A magmatic eruption (bubbly magma moving up in the conduit) would normally show up equally at all three frequency ranges. However, this particular bump occurred a day before the earthquake swarm so is not directly caused by the shaking.

June 2023, Katla

It is worthwhile looking underneath the ice. Katla has a distinct caldera with a deep central depression, a steep rim which has three gaps where water can flow out, and several flow channels feeding the surrounding rivers. The ice cover reaches 700 meters thickness near the northeastern rim. About half the icecap lies above the caldera; a similar area of ice covers the northeastern slopes. The caldera shows geothermal activity. This is nicely shown by the icecap which contains several cauldrons where the heat has melted some of the ice. The hydrothermal activity is mainly located just inside the caldera rim, along the western and eastern edge. This suggests that the heated water is circulating via the ring fault. There are also two active areas within the caldera.

The ice-free caldera map. This view is from the southwest. Image from Helgi Björnsson et al, 2000, Jokull 49, 29 (https://www.researchgate.net/publication/285499559_Surface_and_bedrock_topography_of_the_Myrdalsjokull_ice_cap_Iceland_The_Katla_caldera_eruption_sites_and_routes_of_jokulhlaups).

High resolution map of the caldera. The circles indicate hydrothermal activity. North is up. Image source Björnsson et al.

The recent earthquake swarm was located just inside the northeast rim of the caldera (see Jon’s post: https://icelandgeology.net/?p=11319). The swarm in May was in the same area. The caldera map shows a narrow gorge just outside the caldera, which curves a bit but generally runs north-northeast. This is the rift that fed the Eldgja eruption. The swarm was located a little south of there, within the caldera. Rest assured: last week’s activity had no relation to Eldgja!

Previous activity after the large 1918 eruption occurred on 25 June 1955, 17 July 1990 and 8 July 2011, all in the caldera. All three were hydrothermal events where magma was either not involved at all or was only a minor byproduct. Notably, all were in the summer, which clearly indicates that they were driven by summer melt: Katla is a summer volcano. We might even call it an august volcano, fitting both its size and seasonality. (The eruption of 1918 though was on 12 Oct, showing its magma is not limited by the season.) In 1955, two ice cauldrons formed on the southeast rim and a small jokulhaup occurred. In 1999, the activity was on the southwest rim with tremor and a jokulhaup. The 2011 activity was larger, with strong tremor, earthquakes in the south and east of the caldera up to M3.4, and a jokulhaup which swept away a bridge. The effect was likely amplified by the fact that water had accumulated in the caldera over the preceding year, causing uplift of the icecap.

The 2023 activity fits with these events. The location is a bit north of the 1955 event. The earthquake activity was stronger but it has not caused a jokulhaup – perhaps because the location is a bit away from the immediate drainage channels.

Was it an eruption? Or perhaps a precursor? Katla is a mysterious beast. It has much to hide – it keeps its icecap for a reason.

There is in fact no evidence that the earthquake swarm was related to an eruption. There may have been a small hydrothermal event, as evidenced by the sulphur smell around the rivers. This may have preceded the swarm. However, the size of the earthquakes and the fact they followed on from a similar swarm from two months before does suggest a pressure change around the ring fault. That could be coming from a dike or from increased water circulation. The time of the first swarm may make the first possibility more likely, at least for that event. Perhaps it was the continuation of the intrusions from the deep which happened a decade ago. If you want to know, see the second link below.

My guess for now (and it is only a guess) would be that the earthquake activity is related to (but not coincident with) a small hydrothermal event. — which may not have happened yet! This may be or may become one of Henrik’s missing VEI 0’s. Whether it will become anything more is just a matter of wait and see. Katla is still a quantum volcano – it remains impossible to predict.

Post by Henrik, May 2012; addendum by Albert, July 2023

Henrik Lovén 1958-2019

Deep magmatic roots of Katla…

The Eldgja Eruption: Iceland’s Baptism by Fire

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686 thoughts on “Katla: a retrospective”

    • No, but not an expert so likely to be wrong. But the 5.2 had a long tail in the drumplots.

  2. I’m not an expert, unless you count an ‘O’ level in geography as a qualification!
    I fully expected to see an eruption in progress this morning but we’re still not there. The drum plots seem very quiet, but I believe they are all scaled for the bigger quakes right now and there’s little fine detail. Are there any better plots, please?
    I’m sticking to my light-hearted prediction of 11 July around 08:45, or whatever time I put in, a few posts back.

  3. Okay, is it just me or is there steam coming out of the bottom half of Keilir? It could be a trick of the light, but it just looks strange.

      • If you look very closely, you could see white streaks across the central-bottom half on the north-facing camera. Either it’s steam or some kind of reflective deposits on Keilir that somehow aren’t there before.

        • Or that I am having some kind of Nelson Mandela effect and that they are always there.

        • I think that may be due to the changing angle of the Sun.
          And the acid test is that it has been several minutes now, and there doesn’t seem to e any further development.
          In fact the only slight excitement I’ve had watching the cam (so far) was when the big quake hit last night… rockfalls and dust thrown up all over that slope.

          • That could be true, unless if we could look back into the days and compare between the days (I wish I could).

          • Matter of fact, I swear, I looked at the different times at the same angle of the livestream and they are somehow there. Am I going crazy over a few streaks?

          • If it is significant, it will develop fairly fast. If it doesn’t, it probably isn’t significant.
            It may look different to yesterday due to a rockslide after the big quake ?

          • Okay, have the live stream at hi-def and zoom into the area where the “streaks” are. You would see them. Then, compare the same angle at different times (I.e. separated by hours), but try to see it at the same angle and you might know what I am talking about.

          • I see them, but right at this moment, and increasingly, I don’t think they’re significant because there is no development.
            But it wouldn’t be the first time I’ve been wrong.

          • I think they are not really significant, either, but I think we should take note, just in case. Matter of factly, I looked at this 8-9 hours ago and they are there. Who knows, we could both be wrong here.

    • It’s interesting to consider Keilir. I recall a while back on here that someone said Keilir is a pretty cold lump of rock these days, sitting like a plug on the rift. However, there are small extrusions around its base that suggest previous magma arrivals revisit the cone from time to time.
      The biggest lump, south east side facing the camera, is the area Just Icelandic highlighted as running very hot in his video and thermal drone camera observations.
      I summary, it would be no real surprise if the final arrival of magma is close to the base of Keilir and the hill to its south east. I guess there is enough deep fractured rock from previous intrusions to assist magma up.
      When it happens, it’ll be evident very swiftly.
      (Note: this wild guess will be rendered laughable when magma comes up anywhere along the rift, including next door to the last breakthrough… 🙂 )

      • That could happen. I mean, seeing those white streaks is quite an oddity and seeing them back 9-10 hours ago makes me think something is going on, non-volcanically or volcanically. Sure, it could be a landslide, but unless if it exposed some bright material, I find that unlikely as Keilir is made of basalt (which would make it dark), unless if there is indeed bright stuff in there. That wouldn’t explain why it is bright in the dark as, if it is reflective in the sun that it would be bright at certain times, unless if it is of a brighter color. Now, if it is steam, I wouldn’t say it as an indication of an immediate eruption, like the one and half a minute time-lapse of Meradalir before eruption, but I should also state about the water well over-flowing a few days before an eruption occurs there, despite being far away. Sure, the eruption would show up without warning, but we should also take into consideration the long-term indicators of an eruption occurring. Now, if I am right and that these streaks are steam, they wouldn’t be an indicator of an eruption but rather a symptom of the magma below, even if it doesn’t erupt. If I am wrong and that it is just a few brightly colored rocks, so be it, but either way, we should take note of it.

  4. There is definitely more steam/smoke from the area of the last eruption in Geldingadalir. This ‘steam’ has been rising for 4/5 days in the very early morning but almost unnoticable during the day. Now it is much increased. The old magma must be really heating up there now.

    • Alternatively of course perhaps the air is cooler today so it is more noticable. It is NOT where the cone initially erupted I think so not right on the fault line.

      • And once again I was fooled! As the sun has heated up so the steam disappears.

  5. Let’s take it one more time. This is what to look for in the webcams:

    https://youtu.be/uPoMXmGOv6E

    It’s the first hour of the 2022 eruption in Meradalir, condensed into a one and a half minute time-lapse.

    • Exactly the sort of thing I’m looking for. I saw this last year, and I suspect this eruption may start in similar fashion (NOT expert).
      So if it doesn’t develop quickly,over a few minutes, I suspect it isn’t anything relevant.

    • Many thanks for that video. I never saw the exact begining of either of the first 2 eruptions so that is really helpful.

  6. Can the current intrusion become the magma chamber for future eruptions? It may build a storage that waits for more intrusions to come and cause eruptions. In such a magma chamber the magma can evolve further and feed shield eruptions.

    • A dike will cool and solidify over time. It is not large enough to remain as a liquid magma chamber. A new intrusion in the next weeks can add to the dike, but wait a year and it will have to find a new path. I guess it is possible for a dike to run out of puff within 500 meters of the surface but I would still think that an eruption is more likely than not. The heat will be weakening the crust. The reason nothing has happened yet is that it is pushing up below a thick layer of old lava, the shield eruption. That is hard to break through. The M5.2 shows that there is considerable stress, although that was deeper. I am wondering whether it was caused by part of the Keilir bulk being pushed up or sinking. That thing is a solid block of resistance.

    • It can and maybe will, but it might take more than just a single cycle. Also seems more likely any sort of magma storage will be deeper down, in the mid depths of the crust, like is probably the case at Krysuvik and Svartsengi, and maybe also at Hengill.

      But if you mean a small scale magma chamber something liek the one that formed under Pu’u O’o eventually, that could well form pretty quickly if it lasts for long enough. If the 2021 eruption lasted a bit longer it probably would have done this.

  8. The seismic noise (tremor) is way down. The dike is full, magma is not flowing but the pressure is still there (or even building).

    • I wonder what that means. I’ve been doing the rounds on local news media, and everybody agrees that there’s plenty going on, the magma has moved even higher, and they’re all surprised it hasn’t popped already.

    • Still inflowing at 50 cubic meters a second ( they say ) It have hit hard ground again and is not cutting
      So the pressure coud perhaps be directed upwards and bam

      The earthquakes are when its cutting through the ground

    • As the length and height of the dyke increases, each cubic meter of magma will widen the dyke less and less, so the lateral displacement will be slower. I think that’s what’s causing the amount of seismicity to decrease. At the same time, like a hydraulic piston, the amount of force pushing on the sides will increase. I think that’s why we see these big triggered quakes near the end of the intrusion phase. Note that this is speculation from my side.

    • Could the 5.2 been tectonic, triggering a blockage to the intrusion?

    • Hah ! Well spotted.
      Yes, it would have had me sitting up and paying attention , for a moment at least..

      • After watching that time slot for 3 times it looked to me like a vehicle driving fast enough to raise a dust cloud. If I had seen that I would definitely sat up to take notice!

    • Why is the landscape Autumn brown rather than the normal Tolkien Green of Icelands summer landscapes?
      Been drought perhaps?

      • It’s because this is lava covered in Moss. There is no grasi yet, Will probably take another 800 years for enough dirt to collect to support vegetation. So in the meantime It’s thick layers of most.

      • You mean the Brown hills But they not erupted for 1000 s of years?

        Iceland is so beautyful really I Hopes to move there in a few years

      • The hills are sparsely vegetated, because there’s hardly any soil. It’s not farm land and it probably won’t be any time soon. Too exposed, any kind of precipitation will just run off, but not be useful to any plant life. It’s a barren part of the country. Very beautiful in a moonscape kind of way, but not Tolkien green.

  10. So it has been going on for 5.5 days at this point. At the stated intrusion rates that means something in the ballpark of 30 million m^3 is hanging out down in the dike already. Who knows how long it lasts, but with its current feed rate should be relatively fast at first. Seems hard to imagine it failing given how aggressive it is.

    • That is what one of the RUV articles talks about, 4 hours ago as of now. The 2021 intrusion that was quite similar to this in a lot of ways took 3 weeks to erupt. Then there was a dike that didnt erupt at all, but also seems to have happened a lot faster, so small volume and high rate. Then there was another faster intrusion last year but this time it went basically straight up so it erupted fast. Presently, we are looking at another fast intrusion but it is also a large intrusion like the 2021 event. I really dont see how this can fail while magma is still being fed, but I can see this realistically not erupting for a week or more.

      It should be said too, but the supply decreases when there isnt an open outlet. Magma flux is very high when there is an open vent, and is often even higher after a collapse even if a vent isnt present. Kilauea is a great example of both now, its supply was already very high to begin with at over 1 km3 a decade but now it has gone up several times higher, although much of it is not surfacing. When there is no longer a pressure release, the supply slows, while the pressure increases instead.

      I think we are at that stage at Fagradalsfjall now, the dike has formed but cant find an easy outlet, so the flux of magma to it has decreased and the pressure is increasing as more magma is trying to push up from deeper down. I would presume the recent big quake and the swarms near Krysuvik are reflective of the pressure the dike is putting on the surroundings and continues to do so. Actually, the point which it just really cant take it anymore could be when all of the quakes stop completely, the magma pushing everything out of the way to its limits, leaving the only option to go up.

      🙂

  11. RuvEnglish
    ·
    31m
    Water from the source used by agency Veitur in Grábrókarhrauni, west Iceland, has turned cloudy after yesterday’s 5.2 earthquake in the south west.

  12. “Now that almost six days have passed since the eruption began at Keili, there is still no bubbling of an eruption. However, the Norwegian Meteorological Agency’s measurements strongly indicate that the magma is slowly working its way up to the surface, and it is therefore only a matter of time before it reaches the surface.

    Seismic activity has decreased significantly in the last 2 days, but last night the largest earthquake that has occurred in the country this year occurred. The earthquake measured 5.2 in magnitude and its source was just east of Keili.
    Almost no seismic activity is measured in the intrusion, and this is considered a sign of how close it is to the surface.
    But what delays the magma? The magma that has emerged in recent eruptions is primitive basaltic magma, which is a relatively heavy magma. What finally drives it to the surface is primarily gas pressure. The high gas content makes the magma smoother than the lava layers the intrusion encounters on its way, causing the magma to look upwards. On its way to the surface, the magma can run into an obstacle, e.g. there may be lighter lava layers or tuff layers that hinder its upward movement.

    If we assume that an eruption will erupt, it will probably happen when the gas pressure in the magma tunnel has built up so much that the last layer gives way to the pressure from below and the magma erupts to the surface. It is impossible to predict exactly when it will happen, and that is why there is uncertainty about when an eruption will start.

    Image: Seismic activity at Keili in the last 48 hours. The greatest activity has been to the east of the intrusion itself.”

    https://www.facebook.com/natturuvasud/posts/pfbid0LHVeGFVgD1Hky3DfHJj5anH5p119qXikCqi6itmc2fXQB91x7A4zfoQh46PKP8iol

    • Thse cracks are east of Keilir not over the intrusion, based on the locations given.

  14. Coming back to the Cafe and seeing no progress yet, reminds me of the television sports event pundits sitting around the TV studio table, trying to discuss new and clever analyses of the anticipated game. Drying up and being silent is not permitted, so they gabble on for hours while viewers just want to see the event!

    Pundit 1: “So, Albert, with the eruption expected in the next few hours, what do you expect we will see?”
    Albert: “Well, I believe we will see an eruption. Magma will come out of the ground.”
    Pundit 2: “The last event was very exciting, with magma coming out of the ground.”
    Iceland Met Office visitor (stern face). “Eruptions occur in Iceland. Magma comes out of the ground when we tell it to do so.”
    Albert: “It is not possible to time an eruption with precision.”
    Iceland Office (very stern face): “Magma does what we tell it to, when we apply our stone tablet system.”
    Pundit 1: “Tell us what that means.”
    Albert: “Well, I believe we will see an eruption. Magma will come out of the ground.”
    Ad nauseam…
    Sorry. I’ll keep quiet.

  15. Almost dead silence now, is this the time or just another tease…..

  16. If the magma were really stuck less than 1km from the surface, I believe we would see changes related to increased heat flux, such as drying out of vegetation or increased steam emissions.
    This was also days before the formation of Paricutin Volcano, Mexico.

    • It has only been at that depth for a few days, for all we know the Paricutin magma could have risen really slow and sat in the upper 50 meters for a week or more, most of the data on the intrusion is kind of interpretive for that eruption seeing as it wasnt possible to view it in real time like we can now.

      Paricutin was also more intermediate, starting as basaltic andesite and probably being just andesite by the end, so the magma was not as fluid and probably wouldnt behave like this dike forming in Iceland now.

      I would guess that if this doesnt erupt then over the next few months some thermal areas will probably form above the shallowest parts.

      • I was going to say, it seems logical to assume there can be major differences across what happened at Paricutin and on the Reykjanes peninsula. Volcanoes and their respective eruptions are unique and the factors that drive individual events may be wholly unique as well.

        Obviously this is very general, but that’s kind of the point.

        • Of course there are similarities across similar systems with similar magma types, but the minutiae of individual events can still be wholly different.

  17. Lines in the drumplot are thickening. Tremor plot went up. Wind?

      • Some shallow quakes in just the right area and tremor rising. I think it’s time to watch the RÚV stream.

        • Looks like there was about 20 minutes of tremor and then quake activity resumed and the line became thinner again. It’s getting closer for sure.

        • Looks like the operator for the RÚV cam read my comment. Moments after I posted it the camera panned and zoomed in on a good view of Keilir and has stayed there since. If that’s indeed the case I say thank you to the kind RÚV webcam operator for the good service!

    • Tomas:

      Which highpass seismometer is that, FAF ? Just now I noticed that it is showing small quakes that are not visible on others (like GRI or VOS or ??)

        • Now that the eruption has started, are the small quakes above indicating the final push?

        • FYI
          I noticed at least 3 times on this seismometer thicker traces possibly indicating harmonic tremor and also contacted the IMO asking for realtime data if possible. Retrospective analysis will most likely show that small harmonic tremors were recorded.

  18. Faster eruption like the 2nd but with the volume of the 1st? Obviously ‘we’ll know when we know,’ but curious regardless.

  19. Icelandic news are now reporting an aseismic zone between Keilir and Fagradalsfjall. That zone appeared on Saturday according to the news report. #Iceland #earthquake #volcano

    • After seeing a picture of the fissure on the other side of the mountain, I’d say the camera is safe and could possibly be moved to the other side of the hill.

  28. Oh wow! yes smoke from the base of Litli Hrutur just were I guessed,

  29. seems too localised for clouds/fog on the webcam Nordur

  31. I know it looks like fog/low clouds on the other camera so I know there’s some in the area.. having said that, there REALLY looks like a vapor plume starting off camera to the right on the keillir north camera

    • Also, it gets too intense too quickly to just be a moss fire. There would have to be significant combustibles to have that much smoke so quickly.

    • I carefully backed up the Reykjanes Nodur feed and recorded, the first wisps of smoke occur at 16:41:07 pm, and at 16:42 approx a bigger puff of almost white smoke appears announcing more breakage on the fissure. However the smoke seems to indicate a not too big breakage, if I can guess sizes from the camera, say 100 feet long or so? We need someone with a camera to take a look. see https://www.youtube.com/watch?v=yJfiMhqLgTY

    • More like 7 hours this time of year. 23:38 to be exact, local time.

    • Ah, the fissure is just on the other side of Litli-Hrútur, just out of view from the webcam. They choose to cover the wrong side of the hill. Looks like it’s putting on some steam.

  43. Lol so ot actually did erupt right in the place I predicted, on the back of Litli Hrutur and almost completely out of view 🙁

    • Great prediction, Chad! I find those small quakes on the FAF highpass seismo trace intriguing.. perhaps the last breakage and push through?

  47. Seems very similar to last year, not really huge but enough to make a proper curtain of fire type eruption, so pwrhaps dont expect it to last half the year but it will be quite photogenic while it is alive 🙂

    Looks like the fissures are opening further southwards right in view on those drone shots, you can see the steaming ground ahead of the propagating line of fountains. There is also a visible offroad car trail too so finding a near exact location should be pretty easy.

  50. Pictures from the Icelandic Meteorological Office:
    It is believed that the crack is about 200 meters long and you can see magma jets rising from it. The Norwegian Meteorological Agency’s scientists are in the area taking measurements.
    The walk to the eruption is long and the terrain challenging.
    https://twitter.com/RUVfrettir/status/1678458025823051905

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