December 3, 1:02 p.m., Pacific: I’m updating posts and haven’t seen any new ones for Ljosufjoll yet.
October 7, 2025, 6:43 a.m., Pacific: There is still no sign of magma moving up but quakes continue. Here is the latest update (autotranslated).
April 15, 2025, 2:34 a.m., Pacific: About an hour and a half ago, there was a M3.7 quake here, the strongest thus far.
RUV reports (autotranslated) that it was a single shock, not a swarm, although aftershocks can be expected, and they say that the Icelandic Met Office (IMO) is following developments closely.
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.
It doesn’t sound as though the volcanologists who were interviewed expect an eruption here any time soon, but the article is about more than that. Even if you’re not a geonerd and just are curious about Iceland, or about the Snaefells volcano that Jules Verne sent his explorers down to begin their journey to Earth’s center, it’s well worth the read.
- Current status: Not erupting. Increased monitoring level but Aviation Code still Green.
- Icelandic Volcanoes catalog information.
- Global Volcanoes Program page.
- Snæfellsnes Police Commissioner Public Security Risk Survey (Icelandic, PDF download)
🌋🌋🌋
Original post, December 24, 2024.
Another unfamiliar Icelandic word, but I love it: Light Mountain!
If you have checked out the post on other restless Icelandic volcanoes (besides the Reykjanes fires), you’ll have encountered Ljosufjoll before. The Icelandic Met Office (IMO) did an update on it a few days ago and so I added this one to the list, even though it isn’t one of the “big guns.”
This volcanic system on the Snaefells Peninsula, a bit north of Reykjavik, is waking up but does not yet show signs of imminent eruption.
Since it’s not literally hanging fire, I was going to wait on doing a post for Ljosufjoll until IMO eventually raised its alert level — something not likely to happen any time soon. However, the South Iceland Volcanology and Natural Hazards Group published an excellent post on Facebook yesterday about Ljosufjoll that’s definitely worth passing along.
Google Translate does a better job at translating Icelandic, though it went over their 5,000-word limit. Here is the gist of GT’s version in English (note — “hraun” is the Icelandic name for a single eruption’s lava flow field):
Volcanic activity in the Ljósufjalla system
The Ljósufjalla system on Snæfellsnes has been the subject of much discussion in recent days. Seismic activity there has increased significantly in recent months and there is evidence that it is caused by magma accumulation at considerable depth. ENSu has been regularly discussing this activity since it began in the spring of 2021. Before that time, earthquakes had hardly been observed there for decades.
The Ljósufjalla system is one of three volcanic systems on the Snæfellsnes Peninsula. The name of the system is derived from the Ljósufjöll, which is a cluster of 900-1050 meter high, light-colored liparite mountains in the western part of the system. The mountains are expressive and visible from many places. Throughout geological history, the system’s activity has been greatest at Ljósufjöll. However, the seismic activity that is now occurring is far from that mountain range, or about 30 km to the southeast, in the areas where volcanic activity has been greatest in recent millennia.
Research has revealed that at least 23 volcanic eruptions have occurred in the system since the end of the Ice Age, or on average every 400 years.
The most volcanic activity has been in the areas where earthquakes now occur, near Hnappadalur and Hítardalur. The last eruption occurred 1000 years ago, just after settlement, and Rauðhálsahraun was formed. Hólmshraun, deep in Hítardalur, may also have formed just before settlement.
A number of modern-age volcanic vents are found in the valleys and mountains up from Mýri. Activity northwest of Ljósufjallar has been less in recent millennia. However, there is the famous Berserkjahraun, which is actually three lava flows – all younger than 4000 years.
Main lava flows in the lowlands (see map):
1 – Berserkjahraun, younger than 4000 years
2 – Rauðamelskúlur in Hnappadalur, about 2600 years
3 – Gullborgarhraun, 7000-9000 years
4 – Rauðhálsahraun, shortly after settlement
5 – Eldborgarhraun, 5-8000 years
6 – Barnaborgarhraun
7 – Hagahraun
8 – Hólmshraun, shortly before settlement
9 – Hraundalshraun
10 – Hraun in Kvígindisdalur
11 – Grábókahraun, about 3400 years…
Updates:
January 28, 2025, 8:12 p.m., Pacific: There are no news updates from IMO. Jon Frimann did a post on Ljosufjoll’s likely current state.
January 20, 2025, 8:54 p.m., Pacific: No news on further developments in the system, but IMO’s Benedikt summed up the uncertainty involved in monitoring quite nicely during this interview (autotranslated) with mbl.is:
When asked, Benedikt always says there is some chance of an eruption, but on what time scale it will be can be difficult and there is really no way to predict.
“We can be talking about years or decades, but we can also be talking about shorter periods of time.”
He then gives an example of the time this can take. Deep seismic activity began in Eyjafjallajökull around 1992, which later turned out to be a harbinger of the famous eruption in Eyjafjallajökull in 2010.
“So it took about two decades. So we can’t say anything about the timescale of things like this, we’re just observing it,” says Benedikt.
January 17, 2025, 7:41 p.m., Pacific: Respectable earthquake swarms continue, IMO reports (autotranslated), but these are still quite deep.
January 9, 2025, 5:11 a.m., Pacific: IMO has increased the monitoring level, noting:
Magmatic intrusion at great depth beneath Grjótárvatn likely
Continued seismic activity in the area
9.1.2025Updated January 9 at 11:20
• Turmoil on Thursday, January 2nd
• Continued seismic activity at great depths
• No signs of deformation according to GPS measurements
• The probable explanation for the earthquake swarm is magma intrusion at great depth.
• No evidence of magma rising to the surface
• Monitoring level raised in LjósufjöllOn Thursday, January 2, a continuous disturbance was measured between 5 and 6 p.m. originating at Grjótárvatn. The disturbance, which lasted for about 40 minutes, is formed by continuous small earthquakes, most of which are too small to be located, but only two earthquakes within the disturbance have been located. They are at a depth of just over 15 km and of magnitude M1.5 and 1.8. In total, there were about 20 earthquakes that day, all at a depth of 15-20 km and of magnitude M0.1-2.0.
…
Earthquakes are not usually measured at such great depths in this country, but there are some examples of such in volcanoes such as Eyjafjallajökull in 1996 and at Upptyppingi in 2007 in connection with magma intrusions, and also quite regularly east of Bárðarbunga.
In these volcanic systems, the process that causes deep earthquakes and microseismic activity is believed to be increased pressure in the crust due to magma intrusion, which causes it to fracture.
Yesterday morning, the Icelandic Meteorological Office held its monthly meeting to review recent volcanic activity in the country. The activity at Grjótárvatn was discussed and possible explanations for it were presented. Further analysis of earthquake data from 2021-2024 at Grjótárvatn was recently conducted. The analysis shows that the activity has a high b-value (~2), similar to the deep earthquake swarm at Upptyppingi in 2007. High b-values are often associated with earthquakes in volcanic areas and describe an unusually high proportion of small earthquakes.
…
Analyses of satellite data from 2019 to the summer of 2024 do not show measurable surface deformation. InSAR measurements are of limited use at this time of year because the area is heavily snowbound, which hinders the use of InSAR.
In early November last year, a GPS station was also added in Hítardalur, just over 4 km NW of Grjótárvatn. Since then, no surface deformation has been measured, but this does not rule out the possibility of magma being present at great depths. If magma is accumulating deep in the crust (> 16 km), models indicate that deformation is unlikely to be measured at the surface until the magma volume has become considerable.
In addition to the unusual depth of the earthquakes and their b-values, the duration of the activity, recent turbulence, and comparison with historical activity in other volcanic systems suggest that the most likely explanation for this seismic activity is magma intrusion at depth rather than crustal movement. However, current monitoring data show no evidence of magma reaching the surface.
While seismic activity continues at a similar depth, more earthquakes of magnitude 3 can be expected, but it is unlikely that earthquakes larger than 4 can occur at this depth.
In light of increased activity and indications of magma intrusion at depth, the Icelandic Meteorological Office has raised the monitoring level in Ljósufjöll. A new monitoring plan for the area is being developed.
January 3, 2025, 9:19 p.m., Pacific: From Visir — the whole article (autotranslated) is interesting.
Via Google Translate:
A seismic pulse was measured at Grjótárvatn in West Iceland yesterday afternoon. The Icelandic Meteorological Office has been monitoring the area closely due to high seismic activity and has reported indications that magma is accumulating at great depths. The seismic pulse was measured at a seismometer in Hítárdalur and is said to be the longest so far, lasting forty minutes.
Featured image: The Light Mountains behind Stykkisholmur town and harbor, by dconvertini via Wikimedia, CC BY-SA 2.0
Flight To Wonder 