Iceland's Fagradalsfjall Fires

[bjdeming]

These waits before expected activity are hard (expensive, too, because of warning measures).

Here is IMO's update today (don't know why Google says "Norwegian" -- if anything, one would expect "Danish"):

Magma accumulation under Svartsengi remains stable​

The total volume of magma in the magma chamber under Svartsengi has never been higher since before November 10. Additional scenarios need to be considered if magma accumulation continues without a magma flow or eruption​

17.5.2024







Updated May 17, 2024, at 17:10

• Magma accumulation under Svartsengi remains stable
• About 16 million cubic meters of magma have been added to the magma chamber since March 16
• Increased probability of a new magma flow and another eruption in the coming days
• Most likely to erupt on the Sundhnúks crater series
• Eruption warning may be very short

About 50 earthquakes were recorded in the area around the magma tunnel yesterday, May 16, most of them below 1.0 in magnitude. This is similar to the seismic activity that has been recorded in recent days, but around 50 to 80 earthquakes have been recorded in a 24-hour period, most of them in the areas between Stóra-Skógfell and Hagafell on the one hand and south of Þorbjarna on the other.

Magma accumulation continues under Svartsengi and land is rising there at the same rate as before. At the moment, there is no reason to estimate other than that there is still a considerable probability of a new magma run and another eruption in the Sundhnúks crater series in the coming days.

The last eruption of the Sundhnúks crater series began on March 16. In the 62 days that have passed since then, about 16 million cubic meters of magma have been added to the magma chamber beneath Svartsengi. This is the longest cycle of magma accumulation since this scenario began in late October 2023.

Updated risk assessment and scenarios​

The Norwegian Meteorological Agency has issued an updated risk assessment that is valid until May 21 with everything unchanged. The risk due to gas pollution in area 7 has been increased in connection with the increased probability of a new eruption in area 3. Due to the change, the overall risk in the area is now assessed to be considerable (orange) but was previously some (yellow). The risk due to gas pollution in all other areas is unchanged from last week and assessed as considerable. Due to increased microseismic activity within zone 4, the risk of seismic activity has been increased there.





The Norwegian Meteorological Agency has also updated the most likely scenarios:

Scenario 1 - Eruption between Sýlingarfell and Stóra-Scógfell (Middle of zone 3 on hazard assessment map) Similar location to eruptions that started on December 18, 2023, February 8, 2024 and March 16, 2024.

• A probable cause is a local series of small earthquakes between Stóra-Scógfell and Sýlingarfell, acceleration in deformation and pressure changes in boreholes in the area
• Very short notice (less than 30 minutes), even no notice
• Lava could reach Grindavíkurvegu in 2 to 4 hours

Scenario 2 - Eruption south or southwest of Hagafell (Southern part of zone 3 on hazard assessment map) Similar location to eruption that started on January 14, 2024

• A likely precursor is a series of small earthquakes that start near Stóra-Skógfell or Sýlingarfell and move south, acceleration in deformation and pressure changes in boreholes in the area.
• It is likely that the eruption warning in this area would be longer than in scenario 1, but by how much is uncertain.
• Lava could reach the defenses at Grindavík in about 1 hour.
• A magma intrusion extending south of Hagafell will probably cause significant fissure movements in Grindavík.

The total volume of magma in the magma chamber under Svartsengi has never been higher since before November 10. Additional scenarios need to be considered if magma accumulation continues without a magma flow or eruption​

Until now, the amount of magma that is added to the magma chamber between magma flows or eruptions has been considered. When it is said that magma pressure is increasing in the magma chamber under Svartsengi, it is good to look at the total amount of magma that is estimated to be present.



From October 25 to November 10, 2023, more than 10 million m 3 of magma accumulated under Svartsengi. When a 15 km long magma tunnel formed on November 10, it is estimated that around 80 million m 3 of magma left the magma chamber . Therefore, it can be assumed that about 70 million m 3 of magma was present in the magma chamber under Svartsengi at that point in time. Magma accumulation has continued uninterrupted since then, and magma has flowed at least five times from Svartsengi to the Sundhnúks crater series. Four of these five times have ended in eruption.



Each magma flow or eruption has not exhausted the magma accumulation area, and therefore the initial position of magma accumulation under Svartsengi is different in each cycle after November 2023, as shown in the figure below.

A graph showing the evolution of magma accumulation and the estimated total amount of magma in the magma chamber under Svartsengi from October 25. Each magma flow has not exhausted the magma accumulation area, and therefore the initial position of magma accumulation under Svartsengi is different in each cycle after November 2023. Here it can be seen that the total amount of magma has never been greater since the magma tunnel formed on November 10.​

There are some similarities between the sequence of events in the Sundhnúks crater series and the one that happened in the Kraflufires that started in 1975. In a 10-year period there were 20 magma flows and 9 of them ended with an eruption. In Kräflueld, the magma flows all entered the same magma passage, but were of different magnitudes. The experience from Kraflueld shows that as the number of magma flows increases, more pressure is needed to start them. Therefore, it must be considered probable that magma flows again from the magma chamber under Svartsengi to the Sundhnúks crater series, but there is some uncertainty as to when sufficient pressure will be reached to start a new magma flow and for magma to reach the surface.

The picture shows the interaction between the formation of magma tunnels and the land elevation in the middle of the Kraflu crater. The lower picture shows the elevation of a measuring point within the Kraflu crater, while the upper one shows where the metamorphic zones were in each ridge. In the upper picture, the red color represents an eruption. (Páll Einarsson and Bryndís Brandsdóttir, 2021)​

It has now come to a point that the total volume in the magma chamber under Svartsengi has never been higher since the magma tunnel was formed on November 10. As time goes by without a new magma flow moving into the Sundhnúks crater sequence, the probability of magma moving to other areas where there is a weakness in the earth's crust increases.

Small-scale seismic activity has persisted in recent weeks in the area south of Þorbjarna in the large sigdal at Grindavík. In this area, there are weaknesses in the Earth's crust that magma could exploit to reach the surface. A magma flow from the magma chamber to the area south of Þorbjarna is at this point a less likely scenario than the ones mentioned above. Therefore, this scenario is not taken into account in the updated risk assessment. The Norwegian Meteorological Agency will collect and process data in the coming days to shed more light on this possibility.

 

[bjdeming]

Here is more info on the Krafla fires they are comparing the Sundukhnur eruptions to.

Of course, IMO knows best. This layperson can't help noticing, though, that there appear to be some differences, particularly:

• The Fagradalsfjall events, fed by this same sill. And the continued presence of magma at depth there.
• The way those previously cyclical episodes at Sundukhnur changed after Thorbjorn shifted west in early March, followed by a dike intrusion and then, on March 16, what turned out to be a Fagradalsfjall-style lengthy eruption. In 2019-2020, people thought the Thorbjorn area would erupt. What role does Thorbjorn play in all this, if any?

And what's up with repetitive swarms in adjacent systems from Eldey to the west almost all the way eastward to the Hengill triple junction? Is it all just triggered tension release from the Svartsengi deformation or is something else -- I have no idea what, in this hotspot-influenced oblique peninsular rift of a tectonic plate boundary deformation zone -- going on?


Well, we must wait and see.

 

[bjdeming]

IMO's update today:

Magma accumulation under Svartsengi remains stable​

21.5.2024











Updated May 21, 2024, at 12:30 p.m

• Magma accumulation under Svartsengi remains stable
• About 17 million cubic meters of magma have been added to the magma chamber since March 16
• Increased probability of a new magma flow and another eruption in the coming days
• Most likely to erupt on the Sundhnúks crater series
• Eruption warning may be very short

About 200 earthquakes were recorded in the area around the magma corridor during the Whitsunday weekend, most of them below 1.0 in magnitude. This is similar to the seismic activity that has been recorded in recent days, but around 50 earthquakes have been recorded in a 24-hour period, most of them in the areas between Stóra-Skógfell and Hagafell on the one hand and south of Þorbjarna on the other.


Magma accumulation continues under Svartsengi and land is rising there at the same rate as before. At the moment, there is no reason to estimate other than that there is still a considerable probability of a new magma run and another eruption in the Sundhnúks crater series in the coming days.








The graph shows the estimated amount of magma that has been added under Svartsengi between the eruptions or magma flows that have occurred since November 2023. The slight changes seen in the graph are within the margin of error and have been seen previously during the magma accumulation process.

The Sundhnúks crater series is still most likely to erupt​

In the news last weekend, there was talk of small earthquake activity that has been ongoing for the past few weeks in the area south of Þorbjarna in the large sickle valley west of Grindavík. In the news, it was mentioned that there might be weaknesses in the earth's crust that magma could possibly use to reach the surface. Magma flowing from the magma chamber to the area south of Þorbjarna is considered an extremely unlikely scenario at this point. That assessment is based on new model calculations and other data that were discussed at a meeting of scientists this morning. This slow increase in seismic activity is probably a sign of tension release in and around the magma passage on the Sundhnúks crater series due to increased magma pressure in the magma chamber under Svartsengi.


There is still an overwhelming probability that there will be a repeat of magma flowing from the magma chamber at Svartsengi and into the Sundhnúks crater series.

Pay close attention to see if magma is on the move​

The Norwegian Meteorological Agency has monitored pressure changes in HS Orku's boreholes in connection with monitoring the activity in Svartsengi. A sudden change in pressure has been one of the warnings that magma is running from Svartsengi to the Sundhnúks crater series. It has previously been stated that the signs of a new magma flow were local small earthquakes in and around the magma tunnel, acceleration in deformation together with pressure changes in boreholes in the area. This morning, a minor pressure drop was measured in HS Orku's borehole. No seismic activity or change in deformation was observed to accompany these measured pressure changes. Therefore, the Norwegian Meteorological Agency did not activate contingency plans for possible magma flow.

 

[bjdeming]

Still inflating, still waiting -- interview with Benedikt (autotranslated).

Sill estimated volume was around 19 million cubic meters when the plate boundary shifted on November 10.

An obvious question is, will the plates shift again? An answer is not obvious at all, probably not for the experts, either.

From reading I know that plate boundaries in Iceland aren't at all like the typical rift axis atop a mid-ocean ridge (because of interactions between the ridge here and the Iceland hotspot, according to many authors).

Here the North America-Eurasia plate boundary, from the Reykjanes Peninsula in the southwest all the way to the northern coast and offshore where it leaves the hotspot and turns into another ridge segment -- this plate boundary in Iceland is in segmented zones of broad deformation. (Let's not even get into microplates or how North American and Eurasian plates sometimes trade chunks of crust.)

It's very complex and there is no similar place on Earth to compare it to. Krafla is up in that northern zone, and the boffins are using its recent fires, particularly from 1975 to 1984, as a possible precedent.

An incredible amount of energy was released in that plate jump last November. It's hard to imagine that any more exists to be released in further separations -- at least in this general area

IMO has noted a couple times that plate movements control magma flow (there are other views, but the details are academic and IMO is calling the shots).

So is magma not moving much because of some remnant plate lock? It seems far-fetched.

Too, reading also shows that historically once there is a magma run (a/k/a a "rifting episode"), what happens next is multiple smaller eruptions/dike intrusions ("rifting events") from that newly formed magma body. It would be unusual to have another rifting episode, instead.

This would all be so academic, if this were out in the boonies of Fagradalsfjall...

Police have told reporters that people shouldn't stay in Grindavik, but the town is open; businesses are in operation there and reportedly 20-30 houses are occupied.

Magnus Tumi has said Grindavik is no place for children or for parties. Also, it's not necessarily the case that the next eruption will be much bigger, though it might start out that way and nobody should be near the eruptive fissure area.

The few tens of people staffing the power plant were evacuated the other day when borehole pressures dropped a bit, but no volcanism followed. The plant can be operated remotely.

Still waiting...

 

[bjdeming]

IMO's latest via GT -- the sill's estimated volume was 19 million cubic meters before the first eruption on December 18th, they have said.

---

​

From the Civil Defense patrol flight on May 9. No lava splashes are visible in the crater, although smoke continues to pour out of it. (Photo: Civil Defense)

---

No signs of magma accumulation slowing down​

28.5.2024







Updated May 28, 2024, at 18:30

• Deformation data show that landrising at Svartsengi continues continuously
• About 20 million cubic meters of magma have been added to the magma chamber since March 16
• Continued likelihood of a new magma flow and another eruption
• About 400 earthquakes have been recorded in the last seven days
• Eruption warning may be very short

In total, around 400 earthquakes have been recorded in the last seven days near the Sundhnúks crater series. The largest earthquake was 2.2 magnitude at Sundhnúk. The activity spreads from Grindavík northeast to Stóra Skógfell along the magma corridor. Yesterday, close to 100 earthquakes were recorded in the area, and so far today, almost 70 earthquakes have been recorded. Since the end of the eruption, on May 9, most days between 40 and 60 earthquakes have been recorded, but on occasional days around 80 earthquakes, with the exception of May 24 and 25, when significantly fewer earthquakes were recorded due to strong winds. Therefore, there seems to be a visible increase in the number of earthquakes since yesterday.

Landris at Svartsengi continues at a constant rate indicating that magma continues to accumulate in the magma chamber beneath Svartsengi. Model calculations estimate that about 20 million cubic meters of magma has been added to the magma chamber since the eruption began on March 16. There is no evidence to suggest that it is reducing the flow of magma into the magma chamber. All that can be estimated is that there is still a high probability of a new magma flow and another eruption. However, there is considerable uncertainty in the system about when it will happen and also exactly where it will occur. However, it is most likely that a magma eruption will take place in a similar direction to the six magma eruptions that have occurred since November 2023. It is likely that the warning will be short.



A graph showing the evolution of magma accumulation and the estimated total volume of magma in the magma chamber under Svartsengi from October 25. Each magma flow has not exhausted the magma accumulation area, and therefore the initial position of magma accumulation under Svartsengi is different in each cycle after November 2023. Here it can be seen that the total amount of magma has never been greater since the magma tunnel formed on November 10.

Last week, minor pressure changes were measured several times for a very short time in HS Orku's boreholes in Svartsengi. Such changes have not been observed in the last three days. It has previously been stated that the signs of a new magma flow were local small earthquakes in and around the magma tunnel, acceleration in deformation together with pressure changes in boreholes in the area. It can be assumed that greater pressure changes will be measured in the run-up to magma flow, along with changes in other measuring systems.

The risk assessment is unchanged from the last version, which is valid unchanged until June 4.

Since the earth's crust in the upheaval zone between Stóra-Skógfell and Hagafell is heavily fractured, it is likely that magma will have an easy way to the surface, and therefore the upheaval will not necessarily be accompanied by high seismic activity. The warning of a new eruption can therefore be very short or even non-existent. It is therefore very dangerous to be on the road in zone 3 as defined on the Norwegian Meteorological Agency's risk assessment map.

(Click on the map to see it larger

I don't recall ever reading of such a situation. What is keeping the magma down there?

Probably whatever kept it down there when the dike opened on November 10th and there was this HUGE subterranean rush of magma -- but what was that?

Of note, mbl.is added a livestream of the power plant area -- I haven't seen anything in the news about that, other than that they evacuated the plant for a time when the borehole pressure changes first occurred.

A brief background summary:

From reading I understand that there is an aquifer in the first 800 meters below the surface under that plant, and then an excellent and large geothermal area below 800 meters that they've been using on a large scale since 1976.

It is sealed by a very impermeable layer of good clay materials that this basalt rock weathers into.

The sill -- reportedly at a depth of 3-5 km -- arrived under Svartsengi in 2020, I believe, although the peninsula was rocked by seismicity from at least 2019 on. Magma first surfaced in Fagradalsfjall in 2021 -- a region miles away that hadn't erupted in more than six thousand years.

The Svartsengi/Eldvorp area hasn't erupted since the 1200s, and the Sundhknur crater has been cold and quiet for more than two thousand years.

If you can see a clue in any of that as to what's happening now and what will happen next, congratulations!

 

[TornadoFan]

A new eruption has commenced.

 

[TornadoFan]

 

[TornadoFan]

 

[TornadoFan]

Oh good grief. Keeps opening up towards the south.

 

[bjdeming]

40 minutes ago, per RUV (autotranslated):

The eruption has not yet reached equilibrium​

Benedikt Ófeigsson, head of deformation measurements at the Icelandic Meteorological Office, is interviewed during the eruption watch on Channel 2. He says that the flow from below is still increasing and the eruption has not yet reached equilibrium.
The crack has extended to the south and is approaching Hagafell. "However, it seems that this extension is slowing down so maybe we're seeing it start to stabilize somewhat, it's just too early to tell right away."
A quarter of a year ago, it was estimated that it would take about 45 minutes for the lava flow to reach Grindavíkurvegi. "So maybe it's that infrastructure that's most at risk right now."

 

[bjdeming]

Those fountains are still impressive and gas pollution is a major concern. Per RUV, they're putting gas monitors in every urban area of the Southland; plume is expected to reach Reykjavik tomorrow.

There is a flow heading west and the power plant staff are reviewing options.

Three people reportedly refused to leave Grindavik, and all RUV said is that police have never had to use force yet.

Certainly no one A few civilians reportedly are in Grindavik now, along with emergency responders and journalists. the power plant/Lagoon complex, reportedly were evacuated.

Poor Grindavik, in the path of that gusher. There has been seismicity in west Grindavik, too, but not as strong.

There has been construction of inner barriers for when the outer ones are topped, but ? if it is completed or if it's big enough to divert this.

And that's if fissures don't open in this 1,100-year-old Millenium'-Falcon-shaped town.

 

[bjdeming]

Magnus Tumi, per RUV, who did a surveillance flight about 20 minutes into the eruption:

"We watched the crack grow steadily and it is about 3.2-3.4 km long. The eruption was actually moving upward most of this time."
Magnús says the greatest power is in the south of the eruption now, as the crater was in its last eruption and south before that. "There, lava flows down Hagafell, but it spreads a lot," says Magnús Tumi.

He estimates that after an hour and a half, the extent of the lava may have reached 5 to 5.5 square kilometers. He expects the eruption to subside soon. "Because more than half of the magma that had accumulated under there is already gone, more than 20 million cubic meters."

He says the eruption is clearly the biggest of the eruptions in this series.

 

[TornadoFan]

Southern vent is trying to kick in again.

 

[bjdeming]

Isak's live stream is jumpy but commands an overview of the whole scene:



Visir cam is on the northwestern sector.

 

[TornadoFan]

 

[TornadoFan]

Not sure what is happening here.

 

[bjdeming]

I got the same screenshot! I think it's magma and groundwater making contact. This will widen the eruption's effects considerably, might even bring VAAC into it more deeply.

 

[TornadoFan]

Wow!

 

[TornadoFan]

 

[bjdeming]

Looks like there might be new fissures opening to the south, too?