Iceland's Fagradalsfjall Fires

[bjdeming]

Visir (icelandic Fire Departments have a broad mission...):

The settlement in Grindavík is in danger, but everything is being done to minimize damage.​

The Grindavík Fire Chief says in the special news that the settlement in Grindavík is in danger due to the volcanic eruption that began this morning. If the lava reaches the town, everything will be done to try to influence the flow. To this end, all means will be used, both lava cooling equipment and earthmoving machinery to minimize damage as much as possible.

 

[bjdeming]

IMO, just now:

Updated at 12:30

The total length of the eruption fissure is now about 1200 m and continues to extend southward.

The Icelandic Meteorological Office received a report that a hot water pipe has broken in the northern part of Grindavík. This confirms that considerable cracking has occurred within the town.

Seismic activity continues along the entire magma corridor, with the highest activity at the northeastern end of the corridor. The magma corridor now extends about 3 km further northeast than seen in previous eruptions. Deformation data also show continued northeastward movement. This suggests that magma is still moving through the magma corridor.



Seismic activity since 4 am this morning, April 1st.

 

[bjdeming]

Okay, things have turned out incredibly well, overall, as noted in the blog summary pasted in below (along with some links to sources where I got that information).

Reportedly IMO did think it was a plate boundary move at first, given its scale and the volume of magma moving, but later decided not.

There was an intense but brief seismic swarm west of Svartsengi in the Reykjanes volcanic system and just offshore, the largest temblor a 5-pointer felt island-wide, around 5 pm local time. IMO attributed it to triggered stress release from all the Svartsengi goings on. Jon Frimann wasn't sure but noted there would soon be explosions from magma-water interaction if it was volcanic, and that hasn't happened.

Here's the summary of things thus far, as I understand it:

• University of Iceland Southern Volcanoes Facebook page
• New paper about what might be going on underground.
• RUV update summary (autotranslated).
• MBL.is topic page (autotranslated).
• Visir live coverage (autotranslated)
• RUV article (autotranslated) on volcanic hazard to Reykjavik.
• Jón Frimann’s blog.

Updates​

April 1, 2025, 7:37 p.m., Pacific: Well, Grindavik weathered today’s eruption much better than expected, though media report some cracked roads and a broken geothermal pipe in one house from ground movements.

Had this been similar to any of the other Sundhnukur-area eruptions, that would not now be the case, what with the main vents opening just north of the lava berms snd then crossing the berms and continuing southwestward:

• The fountains would have soared hundreds of feet into the air, flooding the area with lava that probably would have overtopped the berms even without the breakthrough.
• Through the berm, and then on toward town, a line of en echelon fissures would have spread quickly, soon sporting impressive fountains of their own.
• Even if the vents didn’t continue into Grindavik, parts of the town and probably that all-important harbor would have been inundated as the line peaked over many hours and then consolidated into just one or more main vents around the original eruption site, and kept going perhaps for months.

Thankfully, that didn’t happen.

Instead, there was a brief Fagradalsfjall-style bubbling of lava up out of fissures that opened more and more slowly until this movement stalled out; some low fountaining, which began to diminish in early afternoon and now, according to the Icelandic Met Office (autotranslated) has now stopped; and relatively little lava flow.

Icelandic Met Office​

Yay!

The magma movement, though, is still going on. It’s huge, in fact — the second largest flow since November 10, 2023.

IMO estimates that some 15 million of the 22 million m3 of magma believed to have accumulated in the Svartsengi sill since that last eruption ended on December 9 has already flowed into this new dike, which is centered around Sundhnuk and at last report was some 20 km long, based on seismicity:

Warmest colors represent the most recent quakes. (Image: Icelandic Met Office)​

As you can see, most activity is happening on the northeast end, and it far outnumbers events to the south. The boffins tell us that magma is still running out of the sill and heading north.

The good news is that it’s deep — almost three miles underground — and all that seismic activity shows that it is having difficulty breaking through its rocky container.

Even more reassuringly, they say that it shows no signs yet of heading up our way.

They can’t rule out another eruption or the opening of new fissures, probably in this northern area, but apparently it doesn’t seem likely in the short term.

Soon after midnight local time, an IMO spokesperson told Visir that the seismicity, while still constant, appeared to be less intense (fewer 3-pointers). Time will tell whether it actually stops, continues, or does something else.

As someone told the media today, nature is in control.

 

[TornadoFan]

Swarm is still going very strong.

 

[bjdeming]

Couldn't see them on the cam, but I knew the scientists would be out there:

 

[bjdeming]

Eldey is rocking, as this excellent graphic from mbl.is (autotranslated) shows --

Ten earthquakes over magnitude three​

Significant seismic activity has been recorded off Reykjanes. Map/Icelandic Meteorological Institute

--but it's probably triggering. Per IMO, Svartsengi Plain has dropped about 10 inches, and 90% of what was in the sill is now sitting in a dike that extends NORTH of Fagradalsfall and its pyramid of a mountain, Keilir.

The dike has really quieted down, as that graphic also shows. Experts don't expect an eruption anywhere on it, although they can't rule it out since there is still low-level seismicity ongoing.

Is this first round of peninsula eruptions over? Volcanologists are waiting to see if the sill begins to reinflate. Even if it does, after this major change, they'll have a tough time working out the new parameters for an eruption.

The broadest displacement in Grindavik yesterday was on the eastern side of town, which is interesting since the western side was the scene of much of the action on and after November 10, 2023. Overall, the town widened by about 20 inches.

Tectonically speaking, geologists note that, just north of town, there is an important change in the directions that faults take horizontally and vertically. It has to do with forces involved in the Reykjanes Ridge and Iceland hotspot interaction and has been mapped for decades.

Thorvaldur once told media that, because of this, he didn't think eruption would occur in town.

What did come up there last year came through underground cracks, likely the ones around Hagafell, I guess, that directed some lava into groundwater and near the barrier during one of the past eruptions.

It seems possible to this layperson that the leading edge of the fissures that came through the berm yesterday marks the point where this tectonic pressure change begins.

Anyway, there's no question about a connection between Fagradalsfjall and Svartsengi now. But the magma that came out of the sill that is so close to Grindavik erupted right away in a very Fagradalsfjall fashion -- I wonder why.

 

[bjdeming]

This interferogram from IMO (autotranslated) shows the typical butterfly dike pattern but also the bull's-eye appearance of that dramatic deformation change as Svartsengi subsided.

Yeah, it was a really big event (though, thankfully, not so much for Grindavik, as things turned out).

They report there is ongoing low-level seismicity at the northern end of the dike, which is now about two and a half miles north of Keilir and the old "tourist eruption" sites.

Given the impact on major highways here, so close to the capital, and possibly on the village of Vogar, if an eruption occurred here, they're still watching things closely. However, eruption seems unlikely, since the almost emptied sill has stopped subsiding and so is no longer pressurizing magma in the dike.

Whether it switches back to inflation remains to be seen.

 

[bjdeming]

Huh. Svartsengi is inflating again, but they can't tell how much. Since the dike contents are still fluid, this raises the possibility that there still could be an eruption eventually somewhere along the new dike, perhaps at that north end.

They did say earlier that the dike came closest to the surface -- about a mile down -- in the Scogafell area, that northerly part where that one eruption happened. If it must erupt, that would not be a bad place.

GPS measurements show that there are indications that land rise has begun again.​

4.4.2025

Updated April 4 at 2:25 PM

• Indications that land reclamation has resumed in Svartsengi
• Seismic activity at the magma chamber has been decreasing
• Deformation measurements show that movements are still being measured at GPS stations around the northern part of the magma chamber.
• There remains some uncertainty about developments in the coming days and magma movements in the corridor cannot yet be ruled out.
• Seismic activity at Trölladyngja last night and overnight, the largest earthquake measured 4.0 in magnitude
• The risk assessment has been updated, valid until April 8th, everything remains unchanged.

GPS measurements show evidence that land uplift has resumed in Svartsengi, as shown in the accompanying image. It is most likely that the ongoing magma accumulation under Svartsengi is causing the land uplift, but part of it is due to the effects of the formation of the magma tunnel on April 1. This is because when magma tunnels form, they push the crust away from them on both sides. At present, it is difficult to assess the rate of magma accumulation and it may be necessary to wait up to a week to assess further development of magma accumulation under Svartsengi.

Deformation measurements also show that movements are still being measured at GPS stations around the northern part of the magma tunnel, including in Vogar and at Keili. Satellite images showing changes between 2 and 3 April at 4 pm confirm movements in this area. The same data also show measurable fissure movements, of a few millimeters, in the eastern part of Grindavík...

Here's the whole update (autotranslated).

 

[bjdeming]

There's no major news, but Visir reports that Benedikt did a television presentation on the situation, and the article goes into some detail on a lay level. Basically, he noted that it's unusually early for the sill to start refilling, but he thinks an eventual eruption is unlikely from it, although they can't completely rule it out. (The Reykjanesbraut that he mentions is the main drag between Keflavik and Reykjavik.)

 

[bjdeming]

Per IMO's latest update, about five hours ago (via GT):

• Continued small earthquake activity at the magma chamber but slowly decreasing
• Clear signs that land rise continues under Svartsengi
• Landris is measuring faster now than following recent eruptions
• It is too early to say how the rate of magma accumulation under Svartsengi will develop.
• About 30 million cubic meters of magma escaped from the magma chamber on April 1, making this the largest magma eruption since November 10, 2023.
• The risk assessment has been updated and is valid until April 15, with everything remaining unchanged.
• While magma accumulation continues beneath Svartsengi, there is a possibility of repeated magma flows and even volcanic eruptions.

Deformation data clearly show that land rise continues beneath Svartsengi. Land rise is now occurring at a faster rate than after the last eruption. This could be explained by the large volume of magma released from the system in this last event.

However, it is still too early to predict the future trend in magma accumulation rates. Experience from previous events shows that magma accumulation rates generally decrease as the magma accumulation period between eruptions progresses. We need to wait at least a week, possibly several weeks, to determine whether and how much the magma accumulation rate will change.

Based on the available data, it is clear that the inflow of magma under Svartsengi is continuing and therefore the sequence of events at the Sundhnúk crater series is not over. While magma accumulation continues under Svartsengi, there is a possibility of repeated magma flows and even volcanic eruptions. The Icelandic Meteorological Office continues to monitor the area and assess possible scenarios based on the latest data

...

The magma flow that formed now is the largest since November 2023​

According to model calculations, about 30 million cubic meters of magma flowed from the magma chamber under Svartsengi and into the magma tunnel on April 1. This makes the magma flow the largest since November 10, 2023. Microseismic activity continues to be measured in the northern part of the magma tunnel that formed on April 1. Trigger earthquakes are also still being measured at Reykjanestá and west of Kleifarvatn. Deformation around the northern part of the magma tunnel has decreased, but deformation is still being measured at GPS stations closer to the magma tunnel and on satellite images.

Risk assessment updated​

The hazard assessment has been updated and is valid until April 15th with no changes. There have been changes in almost all areas since the last assessment. Area 3 (Sundhnúk crater series) goes from high hazard (red) to considerable hazard (orange). Area 4 (Grindavík) and areas 5, 6 and 7 move from considerable hazard (orange) to some hazard (yellow). Although the hazard level in these areas has been lowered, there is still a considerable risk of landslides into cracks. Area 1 is still assessed as some hazard (yellow).

Haraldur Sigurdsson -- now retired but formerly an acknowledged expert on Krakatoa, among other things, and also the descendant of a woman whose husband kicked her out of the house because she kept giving starving people food during the 1780s Laki flood lava eruption, according to the book Island on Fire -- admits his 2024 prediction was wrong (I love how many scientists will do that!) and has some interesting comments (autotranslated) about the powerful earthquakes that occurred during this mostly underground flow.

They concern magma and the ridge. I don't know how mainstream his views today are, but if peers consider them reasonable, that expedition he describes will probably happen.

 

[bjdeming]

Meanwhile, in Grindavik, there is cautious hope (autotranslated) about the harbor.

I realized, once again, just how impressive and scary the Viking era must have been when I read how the lava cooling/compression teams, etc., were gathering in town on the 1st as the erupting fissure line got closer and closer, telling media, basically, that they were going to fight it house by house.

Viking descendants do not give up.

 

[bjdeming]

Gonna put this here even though it's not technically about Fagradalsfjall/Svartsengi but about another system a little ways north -- as you'll see, there could be a link, though that's speculative.

From the blog:

April 12, 2025, 10:57 p.m., Pacific: An earthquake swarm began overnight, but it is still quite deep.

Per RUV (autotranslated):

…According to Bjarki Kaldalón Friis, a natural hazard expert at the Icelandic Meteorological Office, about 30 earthquakes have been recorded in the area this evening, most of which are between 1.5 and 2.5 in magnitude.
Bjarki says the earthquakes are at a depth of about 15-20 km, so there is no chance of magma erupting there anytime soon, let alone overnight. Changes in the area began to be noticeable in 2019, and the Icelandic Meteorological Office is closely monitoring developments.
He says that we can expect a long lead-up to an eruption in the Ljósufjallar system, similar to the first eruption in Fagradalsfjall, as the volcanic system has been dormant for a long time…

A 2.6 quake shows on the vafri.is graphic currently, so let’s watch snd see if the temblors get stronger.

This area is not too far north of Fagradalsfjall, and it stirred in 2019 — the same year that Fagradalsfjall did.

As noted below, there is no known link between the two volcanic systems, but experts speculate about such a possibility.

And with the new Svartsengi dike having extended north of Fagradalsfjall, this layperson wonders, too. Time will tell.

March 18, 2025: I’m bumping this up not because of an increased risk of eruption but because RUV has done a superb in-depth article (autotranslated) on the volcanism of this area...

RUV is giving this top-headline coverage, which they haven't done with earlier swarms there (the system is called Ljosufjoll, and it's on the Snaeffels peninsula, but I might get into trouble for using so many Icelandic words, which ARE tongue-tying ).

It's because that new Svartsengi dike went that way and even went north of Fagradalsfjall, though AFAIK not onto the peninsula where this system is located. Coincidence or connection between that and the start of tonight's swarm?

No one can say for sure.

The thing is, mid-ocean ridges erupt a little differently from the volcanoes that usually make the news. They don't blow the separating tectonic plates apart; they sort of muscle them apart.

As this layperson understands it, generally speaking and in a too oversimplified way, dike after dike after dike fills in the ridge between the plates, which move away from it on either side for that and other reasons.

Granted, Iceland also has that hotspot anomaly, but the Reykjanes and Snaeffels peninsulas are not right on top of it the way the volcanic zone is that includes Bardarbunga, Grimsvotn, and others.

So maybe the two big dike formations we've seen -- on November 10, 2023, and April 1, 2025 -- are only part of this overall rifting event. Maybe something is going on at depth up there between Fagradalsfjall and Ljosufjoll.

Picture unrelated (Source, CC BY 2.0):

 

[bjdeming]

About 1-1/2 hours ago, there was a M3.7 in the Ljosufjoll system.

Again, this is not part of Fagradalsfjall/Svartsengi system, and it hasn't had damaging eruptions in the past according to the geologic record (and RUV and the Catalogue of Icelandic Volcanoes), but with that recent dike headed up that way, it's newsworthy.

RUV again gave it top headline coverage (autotranslated). They say that IMO is following the situation closely.

 

[bjdeming]

IMO has come up with a whole new hazard assessment approach (autotranslated), taking in the whole peninsula (local media reported yesterday that, probably in response to all the seismicity associated with the recent dike formation, cracks are appearing in various places and a sinkhole opened up beside the tourist path at the famous Bridge Between the Continents -- the paved path is reportedly still safe but don't wander off it or your epitaph might be "Fell into the gap between North America and Eurasia"!)

Here's that plus a Svartsengi update, via GT:

Landris continues in Svartsengi​

15.4.2025

• The rate of deformation at Svartsengi has slowed
• Seismic activity across the magma chamber is decreasing
• New edition of hazard assessment card goes into effect today, April 15th

The eruptions at Svartsengi continue but have slowed down in the past week. The rate is now about twice as high as it was just before the last eruption, or similar to the rate at the beginning of this eruption cycle that began in 2024.

The Icelandic Meteorological Office continues to monitor the area and monitor the development of magma accumulation and assess possible scenarios based on the latest data. While magma accumulation continues under Svartsengi, repeated magma flows and even volcanic eruptions must be expected at the Sundhnúk crater series.

There is still some small earthquake activity around the magma tunnel that formed on April 1st, and dozens of earthquakes are being measured every day in the area. The largest earthquake measured last week was M3.3 on April 13th and was located over the northern part of the magma tunnel about 4 km ENE of Keili. The vast majority of the earthquakes are below M2 in magnitude and at depths of 2 to 6 km.

New version of hazard assessment map covering a larger area​

Today, the Icelandic Meteorological Office is putting into use a new version of the hazard assessment map for the Reykjanes Peninsula. The map is valid until April 22nd, with all changes unchanged.

The new version replaces the previous hazard assessment map that has been used and published since November 2023 and showed hazard assessments of seven well-defined areas in the immediate vicinity of the Sundhnúk crater series.

The seven-zone map has been updated and published 108 times since November 20, 2023. It had its advantages, but its shortcomings included, for example, how difficult it was to distinguish between hazards outside the seven defined zones.

Recent developments on the peninsula, where a magma plume formed and reached the northeastern part of the Svartsengi volcanic system on April 1, 2025, and an eruption occurred west of the northernmost part of Fagradalsfjall in August 2024, highlight the need for a hazard assessment for a larger area.

Therefore, a new map has been developed to overcome the limitations of the previous map. The new map is not only useful for hazard assessment on the Reykjanes Peninsula, but a methodology has been developed that can be applied to all other active volcanic systems in Iceland.





The appearance and presentation of the new hazard assessment map, which will replace the seven-zone map as of April 15, 2025. New features on the map include the volcano alert system level (see blue box number 1), the expansion of the mapped hazard area (see blue box number 2), and selected observation areas (see blue box number 3). See text for more information.

The hazard assessment card is made up of three modules​

Considerable changes have been made to the map, but the main innovations introduced in this version are three:

1. Volcano alert level – this reflects the current state of a volcano and is made up of a four-level system, from 0 (green) to 3 (red). The alert level indicates the state of the volcano and governs how the risk is assessed.

2. Mapped hazards – the assessment is based on a combined assessment of seven hazard factors that exist or may arise: 1) seismic activity, 2) landslides, 3) fissure movements, 4) volcanic vents, 5) lava flows, 6) pyroclastic flows and 7) gas pollution. The colored areas on the map indicate the cumulative hazard level of these seven factors. The shape and size of the areas may change, depending on the hazard being assessed at any given time.

3. Selected observation areas – once the different hazards have been geographically assessed, an average hazard level within the selected observation areas is calculated. The hazards that contribute to the final hazard level of the observation areas are listed separately for each area. Hazards that are assessed as either “high” or “very high” are in bold. The size and shape of these lettered areas do not change, although the hazard assessment within them changes.



At this link you can learn more about how the risk assessment is done, the philosophy behind the warning levels of volcano systems, and what kind of data is behind it.

 

[bjdeming]

The vafri.is graphic continues to show intermittent swarms of microquakes (and a few 1-pointers now and then) at various places on the peninsula, including at Svartsengi, the Sundhnuk craters, and Grindavik (though not offshore there, at least when I've checked).

Here's an RUV article (autotranslated) on that, with the IMO spokesperson saying that it's decreasing but they are still watching and waiting, and that the event is not over yet.

Havrn't seen any news on more cracks or sinkholes yet.

 

[bjdeming]

An in-depth article (autotranslated) on the fiberoptic cable monitoring.

...This is a
standard cable, the same type that brings the internet into Icelandic homes.

This is stated in a statement from the University of Iceland.

Unprecedented low-frequency signal​

Never before has a low-frequency signal of this nature been detected on a conventional fiber optic cable in connection with volcanic activity in the world. The signals in the fiber optic cable have been used to measure deformation, comparable to what we know from GPS technology or satellite images...

That's at Svartsengi/Sundhnuk/Fagradalsfjall. Boffins also used the technique a year or so ago at Grimsvotn, which is hidden under an ice cap and thus very challenging to monitor:

 

[bjdeming]

"...Benedikt says that seismic activity is decreasing, but as long as magma continues to accumulate under Svartsengi, a magma flow or eruption must be expected.

"I don't think we're expecting anything to happen there again anytime soon, and it could be a few months before the next event. The system is clearly slowing down, and I doubt it will erupt this summer based on how things are developing, but it's still not out of the question," he says."

-- Source (autotranslated)

 

[bjdeming]

I did not see this as a possibility on April 1st.

"We wouldn't have anything open if it was dangerous"​

There has been a lot of traffic on the golf course since it opened. mbllis/Eggert Jóhannesson


-- Article (autotranslated)

 

[bjdeming]

On a more serious note, RUV has an article (autotranslated) on volcanic risk and other hazards to Reykjavik.

They also looked at this back in 2024 (also autotranslated), when the longheld idea that the Peninsula is divided into named volcanic systems had not yet been so shaken up by shenanigans among Svartsengi, Sundhnukar, and Fagradalsfjall, culminating in the April 1, 2025, dike, which runs parallel to other systems now (why?).

 

[bjdeming]

Hope so!