Askja, 1875

Photograph by Hreinn Skagfjörð Pálsson. Öskjuvatn on March 27, 2012. At the time the lake (unusually) was ice free.


Askja is a lesser known major Icelandic volcano. The north volcanic zone (NVZ) where it is located is not as touristy as the east (Bardarbunga, Grimsvotn), the south (Katla) or the southwest (Fagradalsfjall) volcanic zones of Iceland, but it should not be ignored. The Krafla rift eruption here lasted (intermittently) for nine years, from 1975 to 1984, while Askja erupted (also intermittently) throughout the 1920’s.

The NVZ begins immediately north (some say south) of the infamous Holuhraun eruption of 2014. There are 5 volcanic centres in the NVZ, of which Askja is the most southerly – and the largest. Askja would be a major attraction in any other region: it has an unearthly beauty, a volcanic oasis in an uninhabited lava-desert landscape with a large caldera and two scenic lakes. Quite a few tourists still manage to get there during the summer, but only after several hours of almost off-road driving. Most come on organised trips. You can get there yourself, but will need to rent a superjeep (four-wheel drive with enough clearance to get over the rubble that pretends to be a road). Be aware that you will need to ford the unbridged rivers that cross the road, preferably when the rivers are not in spate. Many pictures of Askja show the same view of the two lakes, from the same vantage point. It is close to the point where the road gives up.

Askja has had several eruptions in the past 200 years, making it a relatively active volcano with mainly basaltic lava eruptions. This post will focus on the large -and unusual- eruption of 1875. More recently there were small eruptions in the 1920’s and in 1961. In some ways the 1875-1929 activity may represent a single episode.

Since the Krafla eruption Askja has been deflating. There is no direct connection between Askja and Krafla, although they lie along the same rift. Inflation at Askja resumed around 2010. At this time the lake became ice free, evidence of increased hydrothermal activity. There were earthquake swarms. Everything calmed down again when Bardarbunga reactivated. But since a year or so there again has been earthquake activity at Askja. This coincided with Grimsvotn entering an unexpected quiet period. Deep below the brittle crust, the volcanoes here are connected. They live off the same magma supply, drawn up through their individual conduits and stored in separate chambers. They are like different banks, dispersing the same government-issued money but with their own vaults and with different terms and conditions. If Askja is a bank, its caldera may perhaps be viewed as a ‘hole-in-the-wall’ created to dispense magma.


Inside Askja caldera

The volcano rises 800 meter above the surrounding area. Most of it is taken up by a large caldera, measuring 8 km across: in fact the word ‘Askja’ means caldera (or ‘box’). There are two more craters here. The larger one measures 3 by 4 km, has a large lake, and is young: it first formed in an explosion in 1875. Just a few meters north of this crater lies Viti crater, formed in a smaller explosion in the same event. It too contains a lake, and it is near the end point of the road. Brave souls can try to swim in it. But be aware: these lakes can kill. That is a story for later.

The large lake is called Öskjuvatn. It is deeper than the main caldera. The lake is 3.5 km across; the surface is 50 meters below the caldera floor and the lake is 220 meters deep. The small Askja Víti crater is a scenic, deep hole filled with a small lake. Its lake is suitable (kind off) for swimming because it is geothermally heated. Öskjuvatn tends to be frozen and should be more attractive to polar bears than to tourists for their swimming lessons. But its water is possibly cleaner. A swim in Víti crater is certainly memorable – the stench of sulphur will cling to you for days. Stay away from the boiling vent and from falling rocks, and be aware that the slippery path is easier down than back up. In rain it may be next to impossible to get up. If a trapdoor spider would run a bank, this is what its branches would look like.

The bank of Askja

The terms and conditions of the bank of Askja are hard to read. This volcano-bank offers different products at different times and at different branches. It has eruptions at the central branch (the cauldron), in the suburbs (the ring fault and flanks), and out of town (distant fissures). The main product is basalt, but the 1875 eruption produced rhyolite – a bit like the Bank of America suddenly issuing Russian rubles from its cash machines.

Askja is a shield volcano, as might be expected from the fact that it normally erupts basalt. The caldera is enormous and it takes up much of the area of the shield. It is also remarkably deep. The main way a basaltic volcano may form a caldera is by emptying the magma chamber underneath through a distant dike. This happened at Bardarbunga which collapsed at precisely the rate at which Holuhraun erupted, leaving little doubt where the magma went. The same happened at Kilauea during the Leilani eruption. It is therefore natural to expect the same happened at Askja. The caldera is 8 kilometers wide and 300 meters deep, which gives a volume of 15 km3. The sides may have been much higher before being eroded by the ice, making the caldera more than 1 km deep. Such a large volume requires large lava fields (‘hrauns’).

Some have suggested that the caldera is a fraud. It is perhaps 200,000 years old, and for 80% or more of its life has been covered by ice age glaciers. Almost all of its eruptions were subglacial: Askja is an ice-age volcano. Effusive eruptions underneath a thick glacier form hyaloclastites and indeed much of the area around Askja’s caldera is covered in these. Lava underneath thick ice cannot flow out, but forms steep ridges above the erupting fissure. The argument is that the ridges around the caldera are hyaloclastite ridges on intersecting faults, giving the impression that the enclosed area is a caldera.

Askja is now commonly viewed as a combination of both: there was also some subsidence of the central region, but the surrounding ridges are mainly hyaloclastites, perhaps on a ring fault. The bank of Askja has boosted its appearance with a big building funded with some drastic quantitative easing.

The ridges around the caldera reach around 1200 meters in elevation, and the floor of the main caldera is at 1050 meters. It used to be deeper: there is at least 50 meters and perhaps as much as 500 meters of post-ice-age lava and volcanic debris in the caldera.

From Carey et al. 2010

The black dots show the large caldera. The lake forms an extension to the southeast, formed in the recent 1875 eruption. The centre of the new crater is on the edge of the old caldera: it used the same fault that created the caldera ridge. Shallow earthquakes (typically 2-4 km depth) now occur mainly around the southeastern edge of Öskjuvatn. This area also has hydrothermal activity. There is also at times some earthquake activity at much greater depth, up to 30 km.


Askja is mainly, but not exclusively, a basaltic volcano with effusive eruptions both at the caldera and further afield. The largest lava fields are to the northeast, as far as 30 km for the centre of Askja. Together they contain perhaps 10 km3. There are numerous small lava flows are all around the flanks and inside the caldera. Seven such flows erupted between 1910 and 1929, fed from rifts and fissures. To the south the lava flows just reach the area of the 2014 Holuhraun lava, up to 15 km away. Askja’s rifts are lopsided, extending much further to the north than to the south. That is of course a consequence of the lie of the land: the big bulge of Vatnajokull stops the rifts going south. As they would have to flow uphill, it is a no-go area for Askja. To the north, the rifts can continue a long way, running along the side of Krafla’s rifts .

But there is more to Askja. Since the ice age there have been at least three explosive eruptions producing rhyolite. A layer of tephra up to 2 meters deep is dated to 10,000 years ago. Distant 2000-year old tephra (‘distant’ meaning that it was found in Sweden) seems to come from Askja, although it has not (yet) been found at Askja itself. The third rhyolite explosion was in 1875: it left white tephra up to 5 meters thick around the crater, and even 15 km downwind the layer was still 50 cm deep. The rhyolitic explosions produced perhaps 1 km3 (DRE) (or a bit less) in total. They were a pyrotechnic sideshow to the far more numerous basaltic eruptions .

Digging below the surface shows that Askja is more active than it may seem. This is one of the big banks of Iceland. 175 separate eruptions have been identified for the past 7000 years. This is about one eruption per 25 years. (In reality the eruptions occur in clusters, and the clusters are further apart.) In Iceland, only Grimsvotn erupts more often than that, whilst the rate is similar to that of Katla and Bardarbunga. Since the ice age, Askja has produced at least 40 km3 of lava. Not bad for a bank – Askja is a decent volcanic investment. More than half of the caldera floor is covered by lava flows younger than 1510.

The 1875 explosions

The 1875 explosion is a warning not to take this volcano for granted. In fact, the crater lake already indicates there is more to Askja than a friendly fire. Any crater lake should be viewed with suspicion. It means that something made a big hole, recent enough that it has not yet been filled with sediment. The water makes a volcano even more dangerous than it already was. Iceland has two such large lakes: Öskjuvatn and Grimsvotn. You have been warned.

Öskjuvatn formed in the third largest rhyolitic explosion since Iceland’s settlement. This is the oldest eruption at Askja where we are certain of both the date and the time. The eruption column was seen throughout Iceland.

The explosive eruption on 28/29 March lasted 17 hours. It started with phreatic precursor activity (i.e. steam clouds were seen: ‘phreatic’ means water). At 9pm a rising column was seen for an hour (until night fell) and tephra began to fall as far as 50 km away. This is considered a subplinian explosion. A larger, phreatoplinian explosion followed at 5:30am in the early morning, lasting about 1 hour, with a column up to 30 km high. It deposited a 2 meter thick ash layer in the caldera, and send tephra as far as Scandinavia. The ash was wet and sticky. The explosion was followed by pyroclastic flows in the region. After a 30 minute pause a new vent opened and another plinian explosion followed with again a 30-km cloud, this time dry rather than wet. Even 150 km downwind the tephra was still 2 cm deep. Local tephra shows that the explosion was accompanied by fountaining from the rifts or vents.

The eruption was entirely within the area of the modern lake. The lake did not exist at the time but we know that a small pond had formed. When people came to see some time after the explosions, there were three rifts visible which apparently had been the sites of the explosions. They are indicated by the white bars in the image above, and the labels indicate the alphabetic order of the explosions.

The explosions had formed a triangular depression, but it was much smaller than the current crater. The deep crater formed by stepwise collapse lasting almost 50 years, either by magma drainage or by rifting. This ended only with the flank eruptions of the 1920’s.

The 1874-1876 rift

Source: Bryndis Brandsdottir, 1992, 42, Hartley & Thordarsson, 2013

This was a very busy time for the area. The first rumblings were in January 1873, with a large explosion at Grimsvotn. This is not particularly unusual as Grimsvotn erupts often but this eruption was a bit larger than most. Some tephra of this explosion reached Askja, and formed a layer just below the ejecta from 1875.

The first signs of renewed activity at Askja itself were early in 1874 when steam clouds were seen above the volcano. We don’t know what actually happened: no one lived close, and the nearest farmers were tens of kilometer away. Earthquakes were felt in north Iceland in the autumn of 1874, and these became stronger and numerous in late December of that year. (There had been two M6.5 earthquakes of the north coast of Iceland in 1872, but this is too far from Askja to have had any effect, and they also were on a different fault.) New fissures were found in the ground north of Askja. In hindsight, a dike had been forming from Askja running towards the north, and this had caused the earthquakes and the ground deformation. But this was not known at the time.

On Jan 2, 1875, the earthquake activity became so strong that damage occurred to some farm houses. The location of the earthquakes is not entirely clear, but the damage was most severe around the Sveinagjá and Veggjastyki grabens, 50 kilometers north of Askja and the reports indicate that the activity was centred near here.

On Jan 2-3, the earthquakes culminated with an eruption at Askja. There are no eye witness reports other than the eruption cloud, and the size of this event is not well recorded but it may have been a significant explosion which produced a notable crater. It appears that at the same time there was an eruption at Fjárhólahraun a few kilometers north of Askja, as two separate eruption columns were seen. The lava field of Fjárhólahraun has been attributed to this eruption, but it appears that this is much older, possibly from the 14th century. Tephra found at Fjárhólahraun does coincide with the 1875 eruption, and there may have been fountaining activity here but without large lava flows. After these eruptions, the earthquakes diminished but did not fully cease.

The first visit to Askja (remember this was mid-winter, with deep snow, and the area was difficult to reach) was on February 16. They found new craters in the area which is now occupied by Öskjuvatn, just outside the caldera, with intense hydrothermal activity. Remember that this was before the large explosions in March, and the large new crater had not yet formed.

On February 18, 1875, activity suddenly moved far north, to the area where the earthquake activity of December and January may have been focussed. A rift eruption now occurred in the Sveinagjá graben with actual lava. A second site in this graben erupted on March 10, a third one on March 18 and a fourth one on March 25. There were eruption sites along the entire graben, although each seems to have been short-lived. A report from March 25 describes 40 active craters. This sounds more like a continuous fissure which did not develop a single dominant cone. The eruptions here produced the Nyjahraun lava field.

The next event was the major eruption at Askja of March 28/29 which has already been discussed and which affected much of eastern Iceland.

After this event, the main activity continued to be at Sveinagjá. Eruptions here were reported on April 4, 10, 24, July 2, August 15 and October 17. Weaker activity may have continued into 1876 but this was winter when it was difficult to visit. Askja itself also had some activity, with an eruption cloud on May 19, and unconfirmed reports of further activity and in the autumn and winter. In early 1876, the action ceased.

The magma vault

It is interesting that the main activity was not at Askja, but 50 km north in an area with rifts but no central volcano. It was a fairly normal fissure eruption, with lava erupting from separate locations along an extended rift. During this time Askja had hydrothermal activity and major explosions, but less evidence for lava. The eruptions seem related but they were quite far apart. Did the activity come from Askja? Or was Askja just a side show?

The composition of the lava and tephra show a relation between the two events. However, they are not identical. Whilst the tephra at Fjárhólahraun is identical in composition to that at Askja and clearly comes from the same source, Nyjahraun’s composition is a little different. It appears that the new magma mixed with an existing magma reservoir at Askja, but at Sveinagjá only the new magma erupted, not the mix.

The earthquake activity provides a second clue to a connection. The December and January earthquakes (which may have reached M5.5) were focussed on Sveinagjá. But it diminished after the January eruption at Askja. The earthquakes indicate a dike was growing, but it stopped growing after the pressure had been relieved at Askja. From this point the magma underneath Sveinagjá was trying to find a weakness to the surface. This took 6 weeks. After this the activity continued intermittently for a while (9 months) but eventually petered out.

We can speculate on what had happened underground. New magma had begun to collect underneath Askja, initially at a depth below the brittle crust. From there, in December a dike formed towards Sveinagjá. The earthquakes traced where it entered the brittle crust, near Sveinagjá. There was no reported activity in between Askja and Sveinagjá.

While the dike was forming, the magma also began to interact with an existing shallower magma chamber underneath Askja. The interaction rejuvenated this stale magma, by heating and mixing. This rejuvenation caused the rhyolite explosion of March, and also pushed some of the magma through an existing fault towards Fjárhólahraun.

The explosion removed the pressure below Askja, and the dike now no longer received an inflow of magma. The magma at Sveinagjá was still pushing up, and this caused several eruptions along the entire length of the graben. But without new magma they lost their oomph, and finally ceased after 9 months. This model is speculative but seems to fit the events.

Traditionally there have been two ideas for how rifting eruptions occurred. In the first idea, magma was assumed to collect underneath a central volcano, and a dike extended sideways from this chamber under a shallow or steeper upward angle. Where the dike reaches close to the surface, extension occurred and magma began to rise to the surface probing for the weak spots. The second idea began with the rifting, allowing deep magma to rise vertically into the vacated space. Here each part of the rift in a way has its own magma supply, albeit all are connected at depth.

Illustration of the two main models. A third model is like the one in part a), but with a second, deeper dike flowing from the deep magma reservoir. Hartley & Thordarsson 2013

The second version has not received much attention recently. The well studied rifting eruptions in Holuhraun and Kilauea left little doubt about where the magma came from, and this fitted the first idea. The Krafla eruption (close to the 1875 activity) also operated in this way. However, the first idea may not be perfect. If the main magma chamber underneath the central volcano is fairly shallow, then a dike may form below it, bypassing this chamber. It seems plausible that Laki formed in that way. For Askja also, a deep dike well below the main magma chamber may have intercepted some – or most – of the new magma and diverted it 50 km away.

The reason for the explosive activity is that Askja had been inactive for some time, perhaps centuries. The magma chamber had gone stale but not solid. These are the most dangerous volcanoes.

The final question is why the explosions were both wet and dry. Some of the activity was in standing water, and some was on dry land. It appears that water had ponded in the depression (caused by the rifting?) but not everywhere.


Before 2014, Holuhraun was seen as part of the Askja rift system. This is relevant here because there are two lava fields in this area dating from around 1875. These have at times been considered as part of the Askja eruption. Of course, nowadays we know that this area is under different ownership, and is within reach of Bardarbunga’s rifts.

The two lava fields are conveniently called Holuhraun-1 and Holuhraun-2. They erupted in slightly different locations: Holuhraun-1 was 15 km south and Holuhraun-2 erupted 23 km south of Askja (adjacent to the glacier). It now appears that these flows formed before the Askja 1875 eruption. Holuhraun-1 is almost a century older, and likely formed in the winter of 1797. Holuhraun-2 is much closer in time to the Askja eruption but still a bit too early: it formed around 1863. Holuhraun-2 coincided with the eruption in Veidivotn which formed Tröllahraun.

The lava of the three Holuhraun eruptions (including 2014) is identical. We can safely blame Bardarbunga. The closeness in time between 1863 and 1875 may suggest that this was a time of general rifting in the NVZ. It started from Vatnajokull, and reached as far as Sveinagjá, a length of 100 km. Askja may not have been the driving factor: it just happened to be on the rifting path and provided a convenient and existing conduit.


Askja’s beautiful lake holds deadly secrets. Volcanologists have disappeared without trace while investigating it. That is notable in a nation where volcanic eruptions very rarely cause casualties: in one event, Askja killed as many people (2) as all other Iceland’s volcanoes have done together since.

The killings happened in 1907. Two Germans went on to the lake in boat to investigate the caldera, on July 10, 1907. They were never seen again, dead or alive.

The Germans were Max Rudolff, a painter, and Walter von Knebel, a geologist. Knebel was 27 years old at the time, and engaged. The expedition was for his research – Rudolff was there to provide the illustrations. When they did not return, Knebel’s fiancee organised an expedition to find him. The chase was not sucessfull but at least it gave her a new life as she subsequently married the person who accompanied her on the journey.

Memorial to the disappeared

Her name was Viktorine Helene Natalie von Grumbkow; she used the name Ina. Her partner in the attempt to find her fiancee was another volcanologist, Hans Reck. Ina had to proof she could do the trip (being a woman), and did so by traveling around the Reykjanes peninsula where she visited Krysuvik and Keilir – which she climbed. Having managed that journey, the two set off on a trip that went via Hekla, Laki , Myvatn and Herdubreid – the volcanology interest of Hans Reck showed – before reaching Askja.

Ina wrote a book about the failed search. Arriving at Askja, she writes

The Askja crater has in all directions almost the same diameter of around 9 km. The diameter of the almost round lake sunk in the southeast corner of the basin and named in memory of my fiancé Knebel-lake is 4-5 km. Despite the distance, we often saw the dust from the avalanches on the south wall opposite our tents and the water splashing up on the edge of the bank when particularly large blocks had fallen into it. As already mentioned, the lake is enclosed by steep walls in the south and east. Especially on the south wall they are completely inaccessible. The over 300 m high wall here consists of a fusion of rugged almost 100 m high palagonite cliffs, the tips of which stand out sharply against the sky, with heaps of rubble that stretch from the foot of these cliffs to the lake level – the paths of the never-stopping dangerous rockfall. There is not a foot of flat land at lake level

On the west side, the lake is bordered by an approximately 60 m high bank. In its entire length it shows the colourful stratification of basaltic lava and coloured slag with the generally golden pumice covering in the Askja basin. The north side of the lake has the 80 m deep Rudloff crater (named after the young painter Max Rudolff who had an accident with Dr. von Knebel), at the bottom of which green-yellow sulphurous waters boil with alternatingly strong steam. The crater is very close to the lake, so only a very narrow ridge allows it to pass between it and the lake.

After a difficult and fruitless search, the party left again, with one final look at the place where her fiancee had disappeared:

A wonderful distant view presented itself once more from here. Towards the south the wide Askja basin, filled with black lava flows and white patches of snow, framed by multi-shaped, colourful mountains trimmed with snow. Far, far beyond, beyond the whole width of the southern Ödahraun the Vatna Jökull in light beauty. And on the whole, the transfiguring appearance of inviolable majesty, the highest solitude and original perfection. As the early morning mist melts under the rays of the rising sun, so all the glimmers of the modern world fade before the unsophisticated grandeur of this pure nature. The same word that was coined for millennia for the lilies in the field is still valid here today, in view of all this silent splendour: that Solomon in all his glory was also not clothed as this one.

The names that she bestowed on the lake and crater have not survived modernity, but the four meter tall pyramid they left as a memorial is still there. The lake is now called Öskjuvatn, and the small separate crater is called Viti.

The in-land tsunami

At the time, the caused of the disappearance remained unknown. A popular suggestion was that they had used a poorly build boat which had sunk in the lake. But it now appears that the two Germans may have vanished because of the frequent rockfalls that Ina described.

On July 21, 2014, a landslide occurred on the southeastern cliff above the lake. The cliff collapsed over a length of 800 meters, between 150 and 370 meters above the water. Half of the debris, or 0.01 km3, slid into the lake, mostly as a single block. It caused devastation. In hindsight, movement on the cliff had started 7 years earlier, and the creep had already reached 25 meters before it gave way. But no one had noticed the change and the collapse came as a complete surprise. The landslide was among the largest in Iceland of the preceding century.

The original cause was probably the long-term subsidence of the crater along the ring fault. The final collapse came after the ground had been weakened by snow melt (asn effect already described by Ina) and by heavy rain.

Luckily, the collapse happened at midnight and no tourists were present near the lake. They would have seen a frightening event, and probably not have survived. The block slid into the lake at a speed of 140 km/h, and traveled 2 kilometers along the bottom, disintegrating along the way. The block pushed up the water, and this wave started traveling out at high speed. Even lakes as small as Öskjuvatn can have tsunamis! And lake tsunamis are even more dangerous than their open water counterparts. The water bulge can’t spread out – instead the water becomes focussed towards a small area on the far side. The wave here can reach enormous heights. The run-up at Öskjuvatn along the shore reached up to 80 meters! The wave traveled at 50 m/s, and reached the opposite shore in 1 or 2 minutes. By the time people exploring the lake would have recognised this phenomenon was not put on for the tourists but deadly dangerous, there would not have been enough time for them to climb to safety.

The debris was sufficient to raise the level of the lake by 0.5 meter. But that was a minor side show compared to the lake tsunami.

Black sand from the bottom of the lake was left on shore by the tsunami, reaching heights of 60-80 meters

Ina reported numerous small rockfalls into the lake. This was at a time when the caldera was still forming through slow subsidence along the faults at the edges. The disappearance in 1907 was at the same time of the year as the 2014 collapse. This is the time when snow melt can destabilize the ground, something also noticed by Ina. The suggestion has therefore been made that the two Germans were on the lake during a collapse, and were swamped by the wave.

Final words

Askja is a highlight of Iceland, worth the effort it takes to visit, at least when the roads are passable in summer. But it is also unpredictable and dangerous. White Island has shown us the dangers of volcano tourism. The lessons also apply to this giant of Iceland’s sleeping beauties.

And activity is on the rise. Hydrothermal and earthquake activity increased in 2010, and for a while the lake even became ice free. After a calm period, earthquakes resumed last year and since a month there is rapid inflation. Magma is on the move. The inflation is centred not at the new crater of Öskjuvatn, but at the centre of the old caldera. This is a significant influx. Will there be an eruption? Will it be in the caldera, along the surrounding ring faults, to further away? Will the bank of Askja collapse? It is far too early to call wolf. But perhaps it is a good thing that the tourist season here is ending.


Gylfadóttir, S. S., et al. (2017), The 2014 Lake Askja rockslide-induced tsunami: Optimization of numerical tsunami model using observed data, J. Geophys. Res. Oceans, 122, 4110–4122, doi:10.1002/2016JC012496.

Hartley, M. E., and Thordarson, T. (2013), The 1874–1876 volcano-tectonic episode at Askja, North Iceland: Lateral flow revisited, Geochem. Geophys. Geosyst.  14, 2286– 2309, doi:10.1002/ggge.20151.

Carey, R.J., et al. (2010), Tephra dispersal and eruption dynamics of wet and dry phases of the 1875 eruption of Askja Volcano, Iceland. Bull. Volcanol. 72, 259–278

Hartely, M.E., et al. (2016), Postglacial eruptive history of the Askja region, North Iceland.Bulletin of Volcanology 78, Article 28

Brandsdottir, B., (1992), Historical accounts of earthquakes associated with eruptive activity in the Askja volcanic system. Jokull, 42, 1

Ina von Grumbkow, 1909. Ísafold: Reisebilder aus Island.

Albert, September 2014

560 thoughts on “Askja, 1875

  1. A great read; thank you, Albert.

    If Holuhraun belongs solely to Bárðarbunga, that would mean that Bárðarbunga and Askja have erupted at roughly the same time. Coincidence? Or something to do with how the plate separate there.

    • In 1875, Askja erupted a decade after Bardarbunga. Whether that is a coincidence: it could be, as Askja erupts fairly often. But if it would happen again now, i.e. Askja erupting a decade after Holuhraun for the second time, then you would start to think about a relation. That could be a rifting event progressing south to north. Stay tuned.

      • Regarding a rifting event going north. In the mid 19th century it activated the fissure swarm of Askja, but that has yet to rebuild enough strain to do so again so soon.
        Krafla has also rifted, that might be an entirely unrelated thing to the others but it has occurred nonetheless. That leaves the last system in between them, Fremrinamar, which to put it lightly is a monster. No central volcano, just a 50 km long polygenetic fissure lined with shields and crater rows, direct mantle eruptions of Holuhraun scale… Seems to only erupt at all during rifting events, so infrequently, but when eruptions do happen they are the stuff of Jesper’s imagination… 🙂

        • My goal is to have Earth, or live on an exoplanet thats a 100 times more tidaly heated than IO!

          Souch exoplanets been discovered

          My ”cravings” for volcanoes haves No limits at all

          I hopes Iceland does an Sakursunarvatn soon 🙂

          Im getting bored
          Fagradalshraun and Leilani – Holuhraun where too small

          But There is No volcano thats big enough for me 🙂 not even Hawaii is.

          Better to live on a massive terestrial planet or a strange entirely sillicate
          ”brown dwarf” If that coud exist

          If Chad coud build a time – machine, then JS woud be in Hadean Era all day long you know

          This is becomming a serious addiction for me large scale volcanism.. and No volcano is massive enough 🙂

          One of my dreams is a full deep eruption drainout of Grimsvötns deep stoorage system ( that coud perhaps release 200km3 of thoelite into the dead zone ) and Grimsvötn gets perhaps silent for 1000 s of years

          Im so silly

          • I think if you went back to the Hadean you would be lucky to still be alive after a day, no oxygen…

            Dont think there is anywhere on land that can erupt 200 km3, Laki was probably the extreme maximum for Grimsvotn, Eldgja and Thjorsahraun were from Katla and bardarbunga which are slightly taller, all are probably representing the limit on land for this area. The fact only Bardarbunga rifts this way outside of the extremes maybe means Grimsvotn doesnt actually rift at all under normal circumstances, just like Katla. Maybe that is why Bardarbunga did its big drainout in the early Holocene while Katla and Grimsvotn were much more recent.

            I think in theory Mauna Loa should be able to significantly improve, it has 4x the height of any of the icelandic volcanoes, but it doesnt have a voluminous shallow magma chamber of the right dimensions.

        • Yes Thats right

          Mauna Loa haves an insane gravity drain potential with magma chambers
          Totaly Dwarfs bardarbungas drain potential

          Its 10 km tall above the seafloor and 20 from its pressed down base

          Most of ML have been produced by non stop pahoehoe shield building

          The summit calderas are products of removal of shallow chambers

          Do you know How Iceland Sakursunarvatn woud look like if it was Ice free?

      • Grimsvötn and Bardarbunga is What I finds most attractive in Iceland

        But really they are too small too .. all volcanoes are even Hawaii is

        I wants really Big volcanoes
        So its better to move to IO where you haves the solar systems most extensive shields and surface lava flows

        I still hopes for a full Vatnajökull drainout 🙂

        End of rating
        Im as Dumb as a jellyfish wanting these stuff .. but whatever…

  2. Cudos Albert. Always the teacher. Another informative essay, detailed enough, yet without the need for a doctorate in geochemistry or the ability to integrate the area under a curve.

    • Oh, and it makes me think there is more than one reason for implementing a drain pipe for that lake that I mentioned on the last post :-/

      I had assumed there was already a lake that caused the big explosion and tephra production in the 18th century. Apparently it was not, not to this extend, so it is scary to think what it could do now…

  3. Great article Albert!

    Albert, September 2014… 2021. 🙂

    I always have some trouble understanding that just one volcano would be responsible for a particular fissure system only.
    The magma in a central volcanoes magma chamber seeks a lower point to erupt. I can imagine that, and it is has been proven true.

    But when a rift is leading in an eruption, the place where the rift spreads most, is the weakest point. So in a rift magma can also erupt in (somewhat) higher altitude, given the pressure is high enough and the rift opens from lower towards higher grounds.

    Caldera fissure eruptions starts with a break through of the chamber in ‘any’ direction, as in the Holuhraun 2014, when a dike seemed to jump in 90 degree to the (what was thought to be) Askja fissure system, and after that almost was entering that volcano before the eruption started somewhere half way the two Bardar and Askja!

    Albert, Isn’t it so that fissures from several volcanoes (in this case Askja and Bardarbunga) are intertwined?

    • There is one clear case of shared rifts. The far end of the Eldgja rift reached the Vatnajokull rifts, and in fact it pushed out some magma that came from the other side. Leilani was an example of a rift first pushing out stale magma. In Eldgja, a bit of that magma came from the far side. There are limits. It is very hard for external magma to push into another volcanic centre, against the pressure gradient. In the holuhraun area, all eruptions seem to come from Bardarbunga. But just a few kilometers north is Askja lava.

  4. Not sure if this has been mentioned already today but Ive seen reports that there’s been around 120 earthquakes in LaPalma on the south side of the island around 10-5km from the surface.

      • I think that swarm is centered pretty much right under Cumbre Vieja, which is pretty much central to the ridge chain of craters that make up the volcanic edifice. The edifice itself is quite long north-to-south, as the road tunnel through it goes through the north flank of the volcano. (at least, that’s what’s claimed on the island, and I’ve been through that tunnel.).

        It last erupted back in ancient times (1971).

        I do think that any volcanic activity there has a strong potential to generate a mega-tsunami, though one consisting entirely of hyperbolic media stories rather than water. 🙂

        • agreed the tsunami thing is media histeria and clickbait, sure it might happen, in the next 250k-500k years…
          But still since a couple of years the volcano is showing a bit more unrest, doubt an eruption might happen in the short term but who knows?

      • If its erupt it will be bad
        Canary magmas can be Highly mobile .. they are Very Alkaline and low in sillica and the slopes are steep too

        But these lavas are quite cool too .. and therfore often more Viscous than Fagradalshraun.. despite the Canaries basalts having lower sillica

        • Will be a lot like at Fogo in 2014, fluid lava but it is gas rich, so you get strombolian eruptions at a high vent and lava erupting out of vents at a lower elevation. Based on historical activity it seems these lava vents can be quite far away from the main one on Cumbre Vieja, several km distant. 1949 the lava flows were very fast, this could be dangerous.

          • They are noisy little birds which are named after the canary islands, are bred mainly to entertain domestic cats and may be the only bird species named after dogs?

        • I meant the magma compositions Albert

          Canaries is a very weak hotspot.. so it should be alkaline and sillica undersaturated.

          Any Nephelinites there? signs of very small melting ammounts

    • Just seen this on volcanodiscovery, big spike over the last 12 hours. They’re all below and to the south of the Cumbre Vieja edifice, and are by and large all between 7-12km depth, so it’s probably an intrusion.

      There were swarms in 2017 and 2020 though less focused than this one. I wouldn’t worry, it tends to do smaller eruptions and usually in fissures out to sea. The tsunami risk, well…it’ll happen at some point in the next million years no doubt.

    • Seems that the swarm has carried on for over 24hrs now and still going. Possible intrusion of magma maybe?

  5. Thank you Albert for having both the science and the human touch to your story. I am fascinated by the very long dikes in this region and how far things can travel from Bardarbunga northwards. It is interesting to see Askja exhibit the same behavior. When I watched Bardarbunga extend its dikes underground, it was a fascinating lesson in volcanology, maybe Askja has some lessons for us here in the near future.

  6. Albert, thanks for a great article of one of the most beautiful and interesting volcanoes!

    I actually took a bath in Víti 2 weeks ago, a very unique experience! Hopefully it stays intact in case there is an eruption. I can confirm on the strong smell of everything afterwards, and also for the need for 4×4 vehicles to get there – the clearance is not only necessary for the roads, but also for the river crossings!

    Askja and the area around is amazingly beautiful, and you are under constant watch of Icelands most beautiful volcano Herdubreid (curious about potential impacts of current events on this system as well, just saying). The 1875 golden pumice can be seen on the black ground everywhere, it is extremely light and obviously “foamed” into existence quite vigorously. It floats when put into water, it must have been quite a bang! The chances for another one of these rhyolite eruptions are low obviously, but given the remoteness of the area it would be the perfect place for such an eruption to happen. Maybe there is some stale magma left from 1875?

    Albert – assuming magma started accumulating 2010 – what are the general estimates for annual influx? This would give a rough idea of how much accumulated deep down ever since and how much can currently be fed into the upper chamber?

    A rifting from south to north would be amazing to witness! Not sure it will erupt soon, it could do an Öræfajökull and just be in the process of wake-up. Heck, even Kilauea might erupt before that haha

    • I love the personal stories. We would be very interested in a travel story about Askja! As to the magma inflow, this is very hard to define for a rifting region. Much of the magma is used to fill in the opening below the ground (creating new crust), a smaller amount makes it into the shallow crust, and a smaller fraction of that eventually erupts. Eruptable magma may flow at on average perhaps 0.01 km3/yr, but it is intermittent.

      • That means that the primary supply To Bardarbungas, Grimsvötn and Katla are gigantic!

        But very very very little of that reaches the calderas

        But Grimsvötn is constantly inflating all the time as well as having No deep Earthquakes and a very large sulfur emission at current .. so perhaps somekind of open pathway to surface have formed

        Grimsvötn, Bardarbunga is the Only open conduit systems I think in Iceland.. But the calderas is still a ring fault erupters and haves solid roofs

        Without the passive MAR rifting stealing all magma, its possible that Iceland woud be a ”Mega Shield” basicaly one giant kind of huge shield that sits on the slow moving seafloor .. much bigger than Mauna Loa.. but perhaps
        a bit less productive than a Hawaii shield at its peak

        What woud Iceland Hotspot be like If it was in the ocean without a spreading ridge?

      • Haha I wouldn´t mind sharing some travel info – it is an amazing area after all! Are you thinking about a comment or an article? Not sure an article would become too extensive since we only spent a few hours at Askja proper, but a total of 4 days in the area of Myvatn.

        Assuming 0.01 km3/yr this would indicate an intrusion of around 0.11 km3 since 2010 which is now going into the upper chamber, which seems a bit like the “standard-size” intrusion (believe Fagradalsfjall is not far above that volume currently after 7 months, maximum twice?). This is of course leaving out any potential slow and “creeping” build-up in the years before 2010, and also ignoring the intermittency you mentioned, which means, once the feed kicks into action, the volume could be above 0.1 km3/year.

        In short, I´d be surprised if something happens at Askja in the next 6 months – unless it by chance hits a pocket of stale magma or it forms a rift (hen-egg question) for Öskjuvatn water to go down into the hotter parts. The chance of that is very slim so far and requires lots of earthquake activity as per the historical records, but the thought of a rifting episode from south to north keeps the imagination wandering about.. Longer term I am very much looking forward to an eruption at Askja!

        • An article would be great. Does not have to be long (mine are far too long..) or of literary value. A description of the trip, how organised, your impressions, your swim…any photos.. A lot of readers would love it, I am sure!

  7. Begs the question is the rift the volcano, and the edifices along it just it’s outlets? Like tentacles with magma drop-off points.
    There must be something in where volcanoes form along a rift system, perhaps stronger crust or rock capable of storing or creating a chamber for a while before the pressure gets a bit much. That said, most volcanoes are slightly offset of the rift, as the ground below is often quite elastic and mushy i.e. the dead zone.

  8. Superb article! I’ve been interested in Askja ever since the dike in 2011 seemed to be heading for it (and wondering what happens when one volcano intrudes on the magma chamber of another).

    I’m intrigued by the current inflationary cycle (which makes the bank analogy even more apt!)

    Thank you Albert!

  9. Askja makes nice Thoelitic Basalt

    Partial melting is this region around the Iceland Hotspot is extraodinary high ( large ) so you Only gets lunar like thoelite basalt and nothing else as primary melts

    Pretty much No alkalines at all .. around Vatnajökull with souch large mantle melt rates

  10. Brilliant article about Askja. I think it’s hard to find good information about Askja, so you did a really great job here.

    It seems like the next volcano in Iceland to feature in an article would be Snæfellsnes. Maybe you have noted that there have been some earthquakes in that area lately? Well, now it’s stated that the earthquakes could be precursory activity for an eruption. The activity is more precisely located in the Ljósufjöll system. If you have traveled by car to the northern parts of Iceland you may have stopped and climbed a volcanic cone, called Grábrók, that sits conveniently just next to the main road. Grábrók belongs to the Ljósufjöll system.

    Don’t expect an eruption to happen there tomorrow though. Last eruption happened during settlement, so there will probably be a very long and noisy run-up. Eyjafjallajökull took 18 years between first sign of reawakening and eruption and due to the long dormancy, Snæfellsnes will probably take similar time or longer.

  11. Excellent…. Hubby wondered what was holding my interest so intently on the computer and i told him You had written a report on possibly the next volcano to erupt in Iceland. i read to him until he couldn’t stand all my mangled pronounciations of the Icelandic volcanoes and he wandered off… 😉 Must have been a rather intense trip for the lady. And the cairn has outlasted them all. How moving.

  12. Jesper, have you heard of the book “The Little Engine That Could”…”I-think-I-can, I-think-I-can”? In my head I call Fagradalsfjall/Geldingadalsgos – the little volcano that could. It keeps coming back with surprises time after time. Maybe it will give you your longed for massive eruption but I hope not for the peninsula’s sake. 🙂

    I wonder what the Icelandic for The Little Volcano that Could is? Anyone?

    • Giggle Translate suggests “Litla eldfjallið sem gæti”, which is probably Icelandic for “My hovercraft is full of eels”

  13. It does look like after this week long break that the new cycle is for more dispersed and larger eruptions. It is curious that instead of high fountaining though it has decided to create radial flank vents, but in any case the eruption now is significantly bigger than previous flows. Tremor plot shows the eruption has held strong for well over a day now, if it keeps this up for a week that is a big deal.

    natthagi livestream seems to have been lost, actually the chats are saying the cams were turned off to conserve power, and it is impossible to see anything because of the weather, but if the lava has not flowed down into Natthagi by next view I will be very surprised. The 12 hour episodes sent lava rivers several km into Meradalir over flat ground, this is already 3x as long and the flow is all confined to go in one direction.

    • IMHO, if this keeps up for a week, we’ll be looking at an ocean entry. I too am surprised that it hasn’t begun flowing into Natthagi yet.

      Actually, I’m not sure it hasn’t. The western route had lava tubes, so perhaps there might be flow in them already? I’m seeing a bit of smoke (maybe) there this morning, from the cam at the top (good view of those berms near where the old trail was cut) looking down into Natthagi. Just a couple of frames are clear enough.
      I’ll attempt to attach the link. .

    • Will fagradalshraun become a Big
      Lava Shield? composition are getting more titanium mineral rich and temperatures have risen to over
      1240 degrees C. The lava been very runny to near the vent

      They say that the magma composition do match the Big Lava Shields in Iceland. The eruption seems now to have entered constant effusion too

      • It has been constant for 1.5 day. That is far too little to say that the eruption has changed to constant effusion. This may just be a longer cycle than usual because of the blockage: it may go back to the previous behaviour. Wait a few more days

    • It’s a bit early calling it “the new cycle”. There has been one long pause and one sustained eruption that’s still going. If it repeats itself in the coming weeks, then sure I can agree to call it a cycle, but in the meantime it’s just a deviation from the previous cycle.

      Regarding the new vents. Couldn’t a slight shift of the main conduit simply have caused undegassed magma to find its way into already existing lava tubes?

      • In theory yes but there was no existing tube at this location, the tube going to Natthagi a few months ago was a bit more to the south, this area has not really been touched at all since the other cones were active back in April. Lava tubes also dont spatter to this level even when the lava flows directly into the tube from the vent, it seems lava tubes are very insulating but do nothing to hold onto volatiles.

        • The satellite images have shown that there was lava in this area before. It was out of sight of the cameras. I very strongly doubt that these are new vents (and IMO has also said so). They are breaks in the surface layer. No lava tubes are in evidence but there is liquid lava underneath the solid layer. It has become a subsurface lava lake.

  14. Something to watch while we wait for the fog to clear (this afternoon hopefully!)


    This is what happens when a tube is pressurized, the flows are voluminous and the fountains can be impressive, 15 meters here, but they are just like a broken pipe, the lava is degassed and there is not much of a run up from a lava tube, maybe a few tens of meters at most, vents are way deeper.

    We have seen tubes erupting before earlier at Fagradalshraun, they also made dome fountains. Narlet back in mid August was a real vent with a gas rich fountain, I expect so are all of the places erupting today too, there is a new vent under the north wall that is partly obstructed and there are now radial vents in the lava field. How deep those are I dont know but they are at least deep enough that degassing is not too significant, meaning they are deeper than the lava lake at Nar and definitely deeper than the local new lava. I think they branch off below whatever obstructed the conduit a week ago.

    Basically these are almost certainly new vents, with a deep origin. I guess we will have to wait until the clouds pass but I expect they are still active, possibly to have made their own cones, or formed lava lakes. Curious that the lava has not flowed into Natthagi, it might have formed a perched lake, a dangerous situation if its rim breaks…

    • RE:”it might have formed a perched lake, a dangerous situation if its rim breaks…”

      I made that observation on a Facebook group and was countered by information that the observers were 33m above the lava. I noted that there were some standing at the toe of the flow which was what prompted my comments and advised the speed at which the lava had been clocked at here.

  16. The latest frame (10:00) from Meradalir still cam shows activity at the crater and well in Geldinggadalir. LAVA!

  17. Great read! Wakes up memories from my trip there some years ago. Adventurous driving sitt large jeep including over bridgeless rivers. But the sights over Askja and her surroundings was rewarding!

  18. I’m nicely updated and aware of Askja now, thank you! I find Viti an interesting little lake.
    Just looking at the activity in Reykjanes today and see there have been some little rattlers under Keilir, which is the north-eastern end of the intrusion (if I recall rightly). All around 6-8km down. My febrile imagination envisages Keilir exploding…

    • Right now, 19 pm, the volcano smog from the cone itself is pulsing, periods of intense smoke, then almost none, but the vent in the lava field seems quite steady regardless of the cone itself.

    • There is this curious new mode of lava spread, which is now advancing on a wide front, very slowly, rather than generating “river” flows. Might have to do with the large lake surface area, and the low slope (so far). Would expect some kind of river to form once the edge of the “lake” reaches areas with larger slope. At that point it can reach one of the exits into Nattahgi or Sydri Meradalir in a day or so, otherwise I think it will take several days, so probably longer than the current episode. (which according to my super qualified guesswork is about five times the usual length, so around three days)

      My impression though is that the output is lower than during prior episodes. But that might totally wrong.

  19. Red shine suggests lava still inside main vent. Lava probably leaks partially hidden under crust and in tubes

    • Yes, still going, but as luck would have it there is now a dearth of live cameras.
      We could do with a camera on the hill west of the edifice so we can see the whole thing.
      I expect they’ll be on the case anyway!

  20. That little Icelandic volcano… love it so much that it’s alive again, right now in that minute <3

    Thanks for all your explanation and sharing of knowledge!
    Greetings from Switzerland

  21. Fagradalsfjall has entered a pulsing phase. The current episode may be drawing to a close

    • The big cone seems to now have a ~15 minute cycle, but at least one of the new satellite vents is remaining continually active (the one visible from the RUV cam).

      • There’s high fountaining too, somewhere in that thick cloud of vog, at the start of a pulse. At 17:38:13 ejecta can be seen reaching easily over 50m above the cone rim.

      • That observation seems to confirm that the satellite vent is likely just an outlet for gases from a tube or lower level lava lake.

    • Looks now a bit like the highly oscillating signal we observed e.g. in June (also before the eruption in March). The fountain is still bubbling anyway.

      Please note that I have no knowledge whatsoever when it comes to volcanic tremors.

  22. It looks like there are a lot (or at least a few) more bubbly lava bubble thingies in the background on the RUV cam now. Too far away in the background to really tell, though. Nice drone or in-person video from that side could be interesting.

    • Yeah, been looking at that too, something indeed seems to have changed last hour or so..

      • Always hard to say how much is because it’s getting darker and one can see more stuff than in daylight.. but it seems to have spread out more than before, really hope some or our providers of views get us some videos about what is happening over there in more close up…

        • It’s a crust overturning event. There were lots of those back in the early days when there were big perched ponds between the cones and the camera and thus in the foreground of the images. The satellite vents are probably still active but lost in the general glare for the time being.

          We need a good camera on the other side there looking across all of that at the cone. I suggest RUV move their BA-9 camera right back to where it was during the Norðri/Suðri days, but aimed a little to the left of how it was aimed back then so the “Ragnar” cone is centered.

        • Albert, this might be from the 12th as you wondered. I tried to examine the video for its timestamp but could not successfully locate it. The person posted it 8 hrs ago, but that doesn’t mean the video is today. I did see another video of the venting area and the lava river, from the 13th, so the area is still active (as of 19:00 pm local time)

    • Main crater seems to be into short periodic eruptions again, glow goes up every 10-15minutes for a few minutes then back down, so if it didn’t have the crater wall in the way I would suspect high fountains again, might break the wall down and become a fire geyser again..

    • The lower MgO in early August indicates cooler magma. It may be because of the eruption cycles, with the drain back bringing cooled magma back into the deeper layers

  23. The 2-4Hz signal has gone rather bonkers on the “Faf Graph”. It’s a solid band covering 3.7 through to 6.1. This suggests some serious tremor and it’s not helicopters or the sea (unless something catastrophic happened!).

    What on earth is going on with Geldingadalir? The one camera left – you know, the one on the bent stick with its lens cap swinging in the air and hordes of pole-waving people around it – is too far away to make sense of what’s going on.

    It almost looks like waves of lava washing up on the hillside.

    • It’s back to the mode of the fire geysers of May I believe.. Then it was also a solid band of “blue”, and like I said in a post above, there is a 10-15minute cycle of the glow in the main crater going back up and down, so probably doing the geyser thing but have the crater wall in the way..

      • Yes, we are definitely in a periodic regime with ~10min/10min on and off periods. That indeed might explain the new signature on the tremor plots.

    • I see Gutn Tog in his recent video explains the four fountains are pressure leaks from lava tubes, and Met Office concurs.
      So it looks like the ‘new vents’ are not vents. What is certain is the old ‘Door to Hell’ is shut and a new one opened nearby. Probably only a detour from the original pipe.

      Looking at the decrepit camera left, it looks like the current phase is ending, though I am puzzled over the tremor signal.

      • As Beni noted: We are back to the pulsing eruption. Look at this (badly made) animation:

        Where are the guys who made the pretty time lapses?

  24. new activity…..all that bubling spots are dead but the main crater shows increasing activity.
    Think that we can have yet another geiser phase….

    • Probably already is underway. There is a distinction made in literature but I dont think there is an actual geological distinction between the Reykjanes volcanism and that up in Langjokull, they just represent two areas of enhanced volcanism along a greater length of rifting.
      The Snaefellsness volcanoes are not directly related, and seem to be local mantle derived using an ancient rift, but the rift does join up to Langjokull, so they are probably related tectonically. The fact there were eruptions in both areas around 1000 years ago is probably not coincidental.

  25. On the Cumbrea Vieja, I always ask it it possible, is it remotely possible or will it happen at some time in the future. I remember that folks were warned that Anak Krakatou could collapse and people pooh pooh that but it did and killed over 400 people. When I look at that massive slide area just adjacent to the earthquake focus on La Palma my mind goes hmmmmm, if I lived there I might worry. Why you ask, because a major crack in the soil in flat field is one thing but on a steep slope it is quite another.. No one wants to be labeled a Chicken Little screaming the sky is falling but no one wants to be the proud recipient of the Darwin award either.

    • no one wants to be the proud recipient of the Darwin award either

      It seems a sizable faction within the Republican Party would disagree with that last statement.

      We are not the best site for political arguments -admin

      • Nice off-topic cheap shot (sorry Albert, Carl and rest of VC). It wasn’t a Republican that was responsible for the loss of Afghanistan, the deaths of 13 U.S. service members, and leaving $85 billion of high-tech weaponry for terrorists.

        Again, I apologize, won;t follow up. but this was uncalled for.

          • There is nothing more absurd then partisan politics, the disaster that was Afghan war was caused by both the donkeys and the elephants. There are no good political parties and don’t you let them fool into believing there are. Volcanoes should be our focus and not pointless back and forths about political b.s

    • Its not so much the risk isnt there but that it is particularly high at this volcano, it isnt really. It likely will collapse but it is a risk on a scale of many millennia. Mauna Loa is probably a bigger threat when you start going that far, it can have a landslide with the volume of the entire island of La Palma and falling twice as far.
      Megatsunami events also really struggle to cross oceans, there have been a lot more than people realise even in modern time and they have done little beyond the immediare area. They are name for the height of the wave but have little volume. Really, even the immense volume of Mauna Loa is tiny compared to the amount of crust that moves in a subduction fault getting shoved 20 meter up in a few minutes.

      • If you check the bathymetry maps on the Hawaiian chain, it becomes obvious that big landslides are the normal for this volcanic chain. Lanai has gravel deposits up about 1600 ft above mean sea level, so BIG slides did occur. There was concern expressed about the Halima slump (sp?) a while back when the big 6.9 quake occurred on May 4th, 2018 near the south flank of Kilauea.

        btw: If you use the bathymetry map from the HVO website, it actually extends worldwide. See the monitoring webpage to get started.

      • Has anyone did a careful measurement of km^3 displacement for the March 11, 2011 Japan superquake? This would be interesting to look at. (displacement 3d map)

      • Chad, I will have to wholeheartedly disagree with you, all the mega-tsunamis in recent memory were extremely localized events, nothing even remotely comparable to La Palma. The Krakatoa eruption produced long-distance tsunamis while displacing around 1% as much water. The 2011 earthquake displace 250 km3 of water while this La Palma slide could displace 500 km3 of water.

        • I looked up the Alaska earthquake of 1964, mag 9.2 and did a rough back-of-the-envelope calculation of land displacement, approximately 1 million km^2 displaced upwards 9 ft or 3 meters average –> 3.3 x 10^6 km^3 displacement, which is truly enormous.

          See page I15 of for the land displacement estimate based upon tidal gauges.

          I used the map 8. to help me make the rough calculations and took the area of an ellipse.

          • ARRGH, I made a mistake on the vertical displacement, it is 0.003 km, NOT 0.3 km, so the volume is 1.1e6 km^2 x 0.003km = 3298 km^3 displacement NOT the 3.3 million stated above. SORRY about that!

        • They are more localized generally, at least up to 1000 miles or so. Even the 2004 Sumatran earthquake wouldn’t have been anywhere near as devastating but there for there being no tsunami warning systems in the Indian Ocean, which was diabolical really. An 8.7 hit near enough the same spot as the 9.2 in 2005 and didn’t cause a tsunami.

          As far as large landslides and collapses go, Agulhas was by far the largest. Krakatau and the proposed Cumbre Vieja risk pale in comparison to the Storegga Slide even.

          • I remember the Storegga slide. The tsunami wiped out the Doggerbank land. Never resurfaced

    • It continues, now also with a bit (1,5 cm) of inflation and earthquakes moving West-Northwest under Cumbre Vieja.

      • Is it still going just as strong??

        If we are lucky .. We can get an eruption of Nephelinite
        A superalkaline rock that requires the smallest ammounts of partial melting

        • Not sure that is lucky, Cumbre Vieja is very steep for a mostly effusive volcano and it is populated, tourist destination but not tourist eruption… 1971 was fairly tame but 1949 was something that a repeat would be life threatening, same for 1712 and 1585, fluid lava and low elevation flank fissures.

          • Something from the Wikipedia entry about the 1949 eruption: “The onset of the eruption was witnessed by a shepherd who was tending his flock of sheep on the flank of the Nambroque – (Bonelli-Rubio 1950, is explicit that the shepherd was only tending sheep).”

            Open-source has its pitfalls…

        • Going to be Basanite – Nephelinite eruption

          Fluid.. but also perhaps cool and viscous

        • In 1971 the more viscous lava that was erupted initially very quickly turned from “flowing” to “rolling” when it met a steep ravine, if an eruption were to occur higher up at cumbre vieja, we could see something similar that could pose a potential risk for people and property downhill? for example here around 12:00 -13:00 minutes

          • Based on current earthquake plots, an off-shore eruption may be a possible outcome

      • This lava is really low in sillica In that video. Its a Basanite with 42% sillica.
        Ultrabasic Alkaline rock

        But its also relatively cool at around 1130 C and that makes it more Viscous than Fagradalshraun Thats erupting now at 1240 C

  26. The pulsing still continues, now spaced by 8 minutes or so. It is amazing how it has gone back to past behaviour. Only the cone is much higher now and the lava fountains (presumed present) do not show above the ridge any longer.

    • But where is the lava going? Back to the black hole or is there an invisible exit at the base that feeds the lava lake? Only a few small fountains to be seen on the lake, this morning.

      • The lava is going out the back, where no camera’s are. The lava is pooling there.

        • If the lava is pooling there, you should see movement in the lake. This morning it is gray and rigid.
          The level would have to rise or spread to the surface. I don’t see any change on the slope to Natthagi.

          • Maybe this is just the dying hours of this episode, the lake in the back isnt spattering anymore so those vents stopped. The vent on the back wall of Nar seems to have stopped its vigorous eruption at least a day ago, and way before the lake vents which held on up to a few hours ago. The only place erupting is the vent in the crater, and only intermitently with seemignly no outflow. I think the vent we see is actually up on the side of the crater wall, so is not actually buried in the lake, that is why we can see it erupting and why it is so frequent.

            I dont know what will happen now, it might well go back to sleep again for a week, only to repeat, this episode has been pretty well continuous for several days which is a long time.

    • The videos of the eruption in its major stage the other day show lava erupting out of the inner rim of the crater, as well as vents on the outer slope. There was no vent in the crater itself, it is blocked. What I think is that because the vent was diverted slightly it is now narrow again, so effectively reset back to a few months ago. The fountaining was very strong the other day, if it was focussed into one vent it would have been as big as the fountains of May.

          • Yes I saw that one too, curious those seem to die out in favour of the ones on the wall. I guess we really need some new footage of the crater to be sure of what has happened, but potentially it is a big change.

  27. I’m not sure we need to assume changes in the deep plumbing to account for what’s happening.
    The main crater vent was always very close to the north wall, to my eyes even coming up from under it under an angle.
    Since this part of the wall has fractured / dislocated /reset, might this not be enough to block/divert the outflow of the existing vent like we see now?

  28. “I think the vent we see is actually up on the side of the crater wall, so is not actually buried in the lake, that is why we can see it erupting …” Yes. But the volume of the crater is limited. We see no outflow of lava on the (out)side of NAR.
    Where does the lava (thrown into the crater) go? Tubes? Then we have to see lava on one edge. The still cams of Meradalur and Valley without name shows nothing. Natthagi the same.

    • It is a mystery.. we need Sherlock Holmes on the case of the disappearing lava. Much of it may be in the lake below the solidified surface behind the cone, at the back end of where geldingadalir used to be. Some of it is in the lava lake that has build on top of this surface, but that seems to no longer receive additions. None of it is going into Meradalir or Natthagi – and many people will be delighted about that. I seem to recall it was the same in the previous fountaining phases: lava was flowing but mainly out of sight.

      • Oh, I didn’t mean my question as a joke. I find the ideas of other users interesting.
        I think an escape of the lava through Meradalir or Natthagi is the gentlest way. You lose a kilometer of road and max. an unused farm. The detour via street no. 42 takes longer, but the infrastructure is there. Should the lava take the route to Natthagikriki, no one will be happy.
        The lava only stays in the valley, if NAR stops working soon

  29. I note Keilir continues to rumble and rattle around the 7km down area…
    Could the intrusion be making a conduit under there?

    • It’s an interesting spot. That’s where earthquake activity focused right after the eruption started. That swarm then persisted until the middle of June. Back then, the focus was at 6km. This is at the same spot, only 1km deeper. We speculated a bit back then if this could be the place where the dike connected to its deep source. The location is also very close to Þráinsskjöldur. A large shield with similar lava composition as Fagradalshraun.

  30. Just saw a puff of dark smoke arising from the vent.I take it that could have been caused by a internal wall collapse.

  31. 14.37.39, watching the crater wondering if it was only gas clouds, there were some chunks flung up as high as the hill behind. Had to rewind and double check it wasn’t the heat haze playing tricks. I only spotted it because I had the magnifier on, looking for any glow.

    • Nice catch!

      The cone is emitting plenty of gas clouds for sure, though!

  32. Fagradalsfjall’s eruption intervals are down to ~7mins, with a spontaneous 17:22 arrival after only 3 mins. Maybe it’s an decoded message from the underworld? A message to mankind?

    One day scientists will encode it:
    “I am Hades, king of the underworld and I am going to…”
    “Rupert! Rupert, who you talking to?”
    “What is it?”
    “Mom, please stop calling me!”
    (recording stops)

  33. The MET Meradalir still camera at around 18:40, 2021-09-14, shows active lava in Geldingadalir near the area where it previously overflowed into Natthagi. Perhaps that is where recent lava flows have been directed. That area doesn’t show up on the RUV Langihryiggur camera.

    • The Meradalhnjukur Stillcams panned a little to the right to show that the lava now makes progress north from Geldingadalur, past the second vent.

      Looks like a perched lava pond in Geldingadalur makes a slow progress north possible. Maybe it’ll flow over the north end (which is just another way into Meradalur).

  34. Soon the last canary bird have singed
    La Palma nears eruption I think

    • I agree, it is heading that way. It will be interesting, hopefully not near populated areas.

      When I climbed La Palma, the weather was bad, I walked round the cone and could see nothing, the winds built round the cone and got up to extreme speeds, probably close to 100 mph. I was glad to get down the other side. Next day, as I sat on the beach looking up at the clear day, I wished I had gone back.

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