Category: Magma

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Strong earthquake swarm in Bárðarbunga volcano (30-June-2017)

Today (30-June-2017) a strong earthquake swarm took place in Bárðarbunga volcano. This earthquake swarm was in the north-east area of the Bárðarbunga volcano caldera, area that has showed the most earthquake activity since this started in September-2015. Why that is the case is unclear at the moment.


The earthquake activity in Bárðarbunga volcano. Copyright of this image belongs to Icelandic Met Office.

Strongest earthquake in this swarm had the magnitude of 3,6 but other earthquakes where smaller, one earthquake with magnitude 3,4 and one earthquake with magnitude 3,1. All other earthquakes where smaller in magnitude. This earthquake swarm seems to be over for now, but one new earthquake took place at 22:29 and had the early magnitude of 2,7 (or 2,8).

North sea earthquake

I don’t often record an earthquake this close to where I live in Denmark. This is a magnitude 4,8 earthquake (EMSC information) that happened in the North sea. This earthquake was felt in Scotland and Shetland Islands, I don’t know about Norway as the closest distance from Norway was 195 km of Åkrehamn village.


The north sea earthquake as it appeared on my geophone in Bov, Denmark. The distance is 644 km. This image is released under Creative Commons licence. Please see CC licence website for more details.

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Strong earthquake activity on Kolbeinsey ridge (26-June-2017)

During the night of 26-June-2017 an earthquake swarm started north of Kolbeinsey island on Kolbeinsey ridge. This earthquake swarm is located around 355 km north of Siglufjörður village making it difficult to know for sure what is going on there. Largest earthquake so far had the magnitude of mb4,4 (EMSC Information), at the moment this is the only earthquake to register with EMSC. Total of 20 earthquakes have been over magnitude 3,0 so far, as this earthquake swarm is ongoing that number is going to change in the next few hours.


The earthquake activity on Kolbeinsey ridge (green stars). Copyright of this image belongs to Icelandic Met Office.

I don’t know yet if there is any eruption at this location. At this distance the SIL network might not register the harmonic tremor of a small eruption or dyke intrusion. Ocean depth at this location is 2 – 3 km and that rules out any major signs appearing on the surface of the ocean. Currently there seems to be a break between earthquake swarms, that is just how it appears as the SIL network is not able to detect any small earthquakes at the distance of 355 km (about) and that means only minority of earthquakes is being recorded. There is also a possibility that this is just a normal rift earthquake activity that happens at this location, the area I think is is a rift valley, but this being a dyke or an volcano eruption can’t be ruled out.

This article is going to be updated if needed.

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Katla volcano earthquake activity – Update 2

Earthquake activity continues in Katla volcano with activity dropping between swarms. It is unclear at the moment if this is going to result in a eruption but at the moment it is my view that chances of an eruption happening soon (maybe in matter of hours) is high. Official view (government) is more conscious about what is going on in Katla volcano and does not yet issues this type of statements.


Current earthquake activity in Katla volcano. Copyright of this image belongs to Icelandic Met Office.

Largest earthquake today had the magnitude of 3,4 at the depth of 0,1 km. Yesterday magnitude 3,6 earthquake had a fore-shock of magnitude 1,9 at the depth of 14,4 km. This is unusual and suggests that the reason for the current earthquake activity is an injection of new magma, rather than moving of old magma in Katla volcano system. For that reason I’m expecting more earthquake activity in next few hours. This change in activity appears clearly in the earthquake activity that has been taking place, the earthquakes that have happened have variety of depth, with most depth at 15,5 km and up to 0,1 km.

There appears to be a cycle of earthquake activity with quiet period between them that last for few hours at the time. The cycles appear to be getting shorter. I don’t know why that is, but this suggest that Katla volcano is getting more unstable as this earthquake activity. I don’t know yet if it does the same thing as last year (2016) when a swarm of activity started and then dropped after few months of activity. Few SIL stations appears to be showing slightly higher tone on 2 – 4Hz band (just two at the moment). I don’t know why that is. Currently the situation is quiet, I am however expecting that to change without warning at any time. If anything more happens remains be seen, but the chances are high at the moment.

Update 1

There has been a new depth record in this swarm. Earlier 15,5 km earthquake has been relocated down to 25,0 km depth. At this depth it is only magma that can make an earthquake, normal tectonic processes do not work at this depth in Iceland since Iceland is not a subduction zone with deep earthquakes. Just three new earthquakes have appeared in last few hours and current activity remains quiet.


Current earthquake activity in Katla volcano. Copyright of this image belongs to Icelandic Met Office.

There is a lot to suggest that this increase in earthquake activity in Katla volcano is not over. This quiet periods where also observed during large earthquake activity in August-2016. I don’t know why this quiet period happens, they just do.

This article is going to be updated today (21-June-2017) if something more happens.

Article updated at 20:56 UTC. Added new information.

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Sharp earthquake activity in Katla volcano – Update 1

Tonight (20-June-2017) there has been a sharp increase in earthquake activity in Katla volcano. Largest earthquake so far had the magnitude of 3,6. At the moment I’m not sure about other earthquakes magnitudes. I’ll update this article once I have them. The current situation seems be less stable than it appears (based on IMO notice earlier this evening).


Current earthquake activity in Katla volcano. Copyright of this image belongs to Icelandic Met Office.

The harmonic tremor plots have not yet updated for the area around Katla volcano. They update only once every 30 minutes that leaves me currently without any harmonic tremor data at the moment. I’ll post an update once I have those updates.

At the writing of this article an eruption has not yet started. That might change without warning.

This article is going to get update or a new written as this situation develops.

Update 1

Activity in Katla volcano has gone back to background levels in the last few hours. This is the second earthquake swarm in Katla volcano in the last two days, the last one being on the 19-June-2017. Nothing unusual is appearing on the harmonic tremor plots at the moment.


The earthquake activity in Katla volcano at 21:35 UTC. Copyright of this image belongs to Icelandic Met Office.


The main earthquake so far with magnitude 3,6. This image is filtered at 1Hz due to wind noise. This image is released under Creative Commons Licence. Please see CC Licence page for more details.


The second earthquake activity. It is strange to look at on this plot. Seems to be one long continuous earthquake until it drops off. This image is released under Creative Commons Licence. Please see CC Licence page for more details.

Currently there are strong wind in south Iceland making it difficult for me to monitor Katla volcano due to wind and ocean wave noise.

This article was updated at 21:45 UTC.

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Earthquake swarm in Katla volcano (18-June-2017)

Today (18-June-2017) an earthquake swarm took place in Katla volcano. Largest earthquake in this swarm had the magnitude of 3,2 and the second largest earthquake had the magnitude of 2,8 (two earthquakes). Depth was registered at 0,0 km. That means it was below the error margin Icelandic Met Office has, that error margin is around 300 meters +-.


Earthquake activity in Katla volcano today. Copyright of this image belongs to Icelandic Met Office.

This earthquake swarm was close to being directly in north-south direction. At the moment the earthquake activity has gone back to background levels and no other activity appears to be taking place at the moment. I don’t know yet if this earthquake swarm activity is part of the normal summer earthquake activity or something else happening. Only time is going to make that clear.

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Earthquake activity in Öræfajökull volcano (13-June-2017)

Today (13-June-2017) a magnitude 2.6 earthquake took place in Öræfajökull volcano. This is the largest earthquake in this volcano for a long time now and it is worth noting that Öræfajökull volcano normally doesn’t have any earthquake activity. This suggests that something might be up if it doesn’t start to quiet down in next few years. Earthquake activity in Öræfajökull volcano is not high as can be seen in this science paper that covers the years 1994 – 2007 in earthquake activity in Iceland.


Earthquake activity in Öræfajökull volcano (to the south on this image). Some of the activity might be glacier quakes due to summer heat or rain. Copyright of this image belongs to Icelandic Met Office.

Tectonic settings in this area don’t allow for a lot of crustal-tension earthquakes and that suggests that the source of current earthquake activity in Öræfajökull volcano can be explained by magma movements. If this is going to end in a eruption remains to be seen. At the moment current low level activity rules that out, since a lot more and stronger earthquake activity needs to happen before magma can reach the surface.

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Sharp increase in earthquake activity in Tungnafellsjökull volcano

During the last few days there has been a sharp increase in earthquake activity in Tungnafellsjökull volcano. Since there has been no eruptions in the last 12.000 years it is not possible to know for sure what is going on. The earthquake activity suggests that this is a mixture of magma connected earthquakes and stress changes due to Bárðarbunga volcano changes. Making it nearly impossible to know for sure what is going on, at least for now anyway.


Tungnafellsjökull volcano is located north of Bárðarbunga volcano. It is marked by cluster of small earthquakes (red dots) on this image. Copyright of this image belongs to Icelandic Met Office.

What is different now, is that after a long period of quiet there was a sharp increase in earthquake activity in Tungnafellsjökull volcano. If past earthquake swarm activity is anything to go by I expect this earthquake activity to die out slowly and activity should go back to normal in Tungnafellsjökull volcano. That means no earthquake activity at all. I don’t think that anything has changed in that volcano, at least I don’t have any hard evidence of that being the case for the moment. That might change since lack of historical eruptions leaves a room for lot of speculations.

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Increasing earthquake activity in Katla volcano

Over the last few days there has been increasing earthquake activity in Katla volcano. The increase is slow, but this is a increase in activity. This holds in line with increased glacier melt during the Icelandic summer. What appears to be different now is the phase the increase is happening. At the moment the earthquake activity has not yet reached last year activity levels.


Earthquake activity in Katla volcano for the last 48 hours. Copyright of this image belongs to Icelandic Met Office.

Largest earthquake in last 48 hours had the magnitude of 2,4 and took place in a minor earthquake swarm inside Katla volcano caldera. Since then there has been minor earthquake activity inside Katla volcano caldera, but compared to last year current activity is low. Other earthquakes that have happened have been smaller in magnitude.

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Minor earthquake activity in Hekla volcano

Today (09-June-2017) there has been earthquake activity in Hekla volcano. Largest earthquake only has the magnitude of 1,0 and greatest depth is 2,2 km.


Hekla is to the right on this image. Copyright of this image belongs to Icelandic Met Office.

At the moment there are no signs that this is going to lead to an eruption. That might change without warning. The source of this earthquake activity might be gas or steam activity in the crust in Hekla volcano, at least when it comes to shallower depth. At more depth it’s slightly difficult and increases the changes the earthquakes at those depth are created either by magma or pocket of gas breaking the crust.

At the moment Hekla volcano is not showing any signs that eruption is imminent.

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Deep earthquake activity in Trölladyngja (volcano)

Today (08-June-2017) there have been deep earthquakes in Trölladyngja (volcano). This earthquake swarm was shallower than last earthquake swarm that took place in Trölladyngja. Several months ago the earthquakes in Trölladyngja where happening at 28 km depth, but now they are at the depth range of 18,6 – 23,3 km, this means that the magma under Trölladyngja is migrating upwards at fast phase, a lot faster then I thought was possible. Earthquake swarm in November-2015 where slight off to the side, those earthquakes had the depth of 15 – 18 km as I wrote about here. Since November-2015 here has been other activity in Trölladyngja, but that has been in the form of one or two earthquakes so I have not written about it (I never bother with just one or two earthquakes at location due to the amount that happens daily in Iceland).


Earthquake activity in Trölladyngja (volcano), north-east of Bárðarbunga volcano fissure swarm. Copyright of this image belongs to Icelandic Met Office.

Last eruption in Trölladyngja was according to GVP (under Bárðarbunga volcano history) was 7000 years ago. Since then nothing has happened. There has been a lot more eruption in Dyngjuháls area and that area is also having deep earthquakes. That area is also covered with ~200 meters of glacier. It remains to be seen what happens next in the Bárðarbunga volcano saga.

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