Category: Katla / Mýrdalsjökull

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Magma on the move in Katla volcano

While the source of the harmonic tremor yesterday in Katla volcano is not immanently clear. It is has been concluded that magma is on the move inside Katla volcano. It has been suggested that the harmonic tremor yesterday in Katla volcano is a mixture of both hydrothermal activity and water flows under the glacier. But hydrothermal activity has increased in Katla volcano since July and seems to be continuing on that path for now.

The earthquake activity in Katla volcano has been growing since July, when a sharp harmonic tremor spike did take place and was followed by a glacier flood that did destroy the Múlakvísl river bridge. But that flood did peak at ~5 meter high.

Currently the activity is quiet in Katla volcano. But that might be because the earthquakes are not being detected by the bad weather that is currently in this area (and all over Iceland for the fact).

Here is a overview of the change in activity since Week 34.


The earthquake activity in Katla volcano during Week 34. The number is the cauldron in Katla volcano. Notice the interesting earthquake activity in SE part of Katla volcano, well outside of the caldera area. Copyright of this picture belongs to Iceland Met Office.


The earthquake activity in Katla volcano during week 35. The earthquake activity in SE part of Katla volcano continues at the same place. Copyright of this picture belongs to Iceland Met Office.


The earthquake activity in KAtla volcano during week 36 (current week, last updated today 7. September 2011). Earthquake activity in SE part of Katla volcano continues as before.Copyright of this picture belongs to Iceland Met Office.

Current activity in Katla volcano is quiet (less detection due the storm is also a factor in this). But that can change without any warning at all and at any time. But there is no reason to scaremonger what is going on in Katla volcano. It is a fact of life and cannot be changed. So the best way is to prepare if people live close to Katla volcano, or if you live far from Katla volcano the best thing is to monitor and learn from what is now happening in Katla volcano. Scare tactics do not any good and serve no purposive at all and never done so.

Icelandic news about the activity in Katla volcano. Use Google translate to understand. But be aware it is not approved by Santa.


Ekki ótvíræð merki um yfirvofandi gos (mbl.is, Icelandic)
Engin augljós skýring á óróa (mbl.is, Icelandic, 6. Sept, 2011)
Flogið yfir Kötlu (mbl.is, Icelandic, 6. Sept, 2011)
Kvika safnast saman undir Kötlu (Rúv.is, Icelandic)
Fylgjast með aukinni virkni í Kötlu (Vísir.is, Icelandic, Video in Icelandic, 6. Sept, 2011)
Jarðhiti aukist mjög mikið undir Kötlu (Vísir.is, Icelandic, 6. Sept, 2011)

Update 1: According to news the local emergency units and police have started to review the evacuation plans and emergency plans in the case of a eruption in Katla volcano.

News about that can be read here, if you risk Google Translate.

Fara yfir áætlanir um viðbrögð (mbl.is, Icelandic, 7. Sept, 2011)

Blog post updated at 00:43 UTC on 8. Sept, 2011.

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Most likely water creating harmonic tremors in Katla volcano (for the moment)

In the news from Rúv at 22:00 UTC it was sad that water is the most likely source of the harmonic tremors in Katla volcano. But it seems that hydrothermal activity in Katla volcano is increasing and melting the glacier. But for the past few hours there have been signs of hydrothermal melt water getting into Múlakvísl glacier river, making the river have more water then normal and increasing conductivity in it. This is not glacier flood as such. The cauldrons that formed in July have not changed according to this news, but it was not reported if they had actually gotten deeper or larger.

Due to cloud cover it was not possible to explore the north part of Mýrdalsjökull glacier. Just the south part. According to the news on Rúv at 22:00 new small cauldron have formed in the south part of Mýrdalsjökull glacier. They are shallow at present time and may have taken few weeks for form to present size (not sure how big they are), but among this cauldrons is a cauldron that has not been seen for past seven to eight years, cracks have formed around the cauldron and he has gotten deeper and water has collected in the cauldron. But with more earthquake activity and increased hydrothermal activity under the glacier. So more monitoring is needed on Katla volcano according to Magnús Tumi Guðmundsson volcanologist at University of Iceland.

Note: When I wrote this blog post. It seems that new earthquake swarm is about to start in Katla volcano. At least I think so.

News about this events in Icelandic. Use Google translate if you want to insult the Easter-bunny.

Telja að vatn valdi óróa (Rúv.is)
Engin augljós skýring á óróa (mbl.is)
Jarðhiti aukist mjög mikið undir Kötlu – dæmigerð einkenni að menn eigi að búa sig undir gos (Vísir.is)

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Strong harmonic tremor pulse starting in Katla volcano

There seems to be a strong harmonic tremor pulse starting in Katla volcano. I do not think that this is anything else for the moment. I do not have any more details at the moment. But I am going to post updates when I know more.

Start of the harmonic tremor pulse on the SIL stations that he appears best on.


Slysaalda, north of Katla volcano. Copyright of this picture belongs to Iceland Met Office.


Rjúpnafell, South-west of Katla volcano. Copyright of this picture belongs to Iceland Met Office.


Lágu Hvolar SIL station. Copyright of this picture belongs to Iceland Met Office.


Álftagröf SIL station. South of Katla volcano. Copyright of this picture belongs to Iceland Met Office.

The start of the harmonic tremor event can be seen on the end of harmonic tremor chart. It stands out as it above the background noise on the SIL station. Next update on the SIL stations (10 or 20 min until it happens) is going to show more how big event this is going to be.

More updates when I know more on what is taking place in Katla volcano.

Update 1: The Public Civil Emergency Authority (Almannavarnir) in Iceland has increased monitoring with Katla volcano. But they have not declared any emergency level yet. Announcement about that in Icelandic can be found here. But scientists where flown over Mýrdalsjökull glacier at 18:00 UTC today (6. September 2011).

According to the news there has been increase in conductivity in Múlakvísl river. But for the moment the water level has not increased. There has been speculation that the tremor was created by water on the move. But that is unclear at the moment, however it is quite possible that more water is on the move under Mýrdalsjökull glacier.

Currently the harmonic tremor in Katla volcano has dropped back to normal levels. For the moment everything is quiet in Katla volcano. But that can change at any time without any warning.

News about this in Icelandic.

Órói undir Mýrdalsjökli (Rúv.is)
Fylgjast með aukinni virkni í Kötlu (Vísir.is)
Eftirlit aukið með Kötlu (mbl.is)
Flogið yfir Kötlu (mbl.is)

Update 2: It seems that a new harmonic tremor episode is about to start in Katla volcano. So far it has remained small. But it is impossible to know if that is going to change suddenly or not. Update 2b: There is also some wind noise on the seismometers around Katla volcano. This wind is increasing background noise. It often look like a tremor increase, while in reality it is not.

Blog post updated at 18:37 UTC.
Blog post updated at 18:46 UTC.
Blog post updated at 20:03 UTC.
Blog post updated at 20:29 UTC.

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Growing harmonic tremor spike in Katla volcano

It seems that Katla volcano is going to keep me busy for coming days and weeks.

At this moment it seems that there is a growing harmonic tremor in Katla volcano. This harmonic tremor started today after the earthquake swarm that took place earlier today. After it stopped a spikes of small harmonic tremor spikes did start to appear. During the past few hours they have been growing in size. But it seems that the harmonic tremor drops for few moments between spikes.


Earthquake swarm that took place yesterday in Katla volcano. Copyright of this picture belongs to Iceland Met Office.

This earthquake swarm was mostly small one. With largest earthquakes going up to around ML2.1.


Slysaalda SIL station. Harmonic tremor appears poorly on this SIL station. Copyright of this picture belongs to Iceland Met Office.


Rjúplafell SIL station. The harmonic tremor signal can be seen here clearly, even if it a small one. Copyright of this picture belongs to Iceland Met Office.


Lágu Hvolar SIL station. The harmonic tremor signal can be seen poorly on this SIL station. But it signalled with minor change in the background noise on this SIL station. Copyright of this picture belongs to Iceland Met Office.


Álftagröf SIL station. The harmonic tremor spike can be seen most clearly here, as it goes clearly above background noise. Copyright of this picture belongs to Iceland Met Office.

From what I can tell this harmonic tremor signal is growing every few hours or so. It is possible that this is a repeat of what did happen in July. But for the moment it is too early to know that for sure at the moment. But for the moment there is no eruption about to start in Katla volcano.

When I was writing this blog post, it seems that a new earthquake swarm is about to start in Katla volcano. But the earthquake swarms in Katla volcano often start slowly with few earthquakes, but they seems to grow with time.

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New harmonic tremors spikes in Katla volcano

This has become almost a daily occurrence. But today there was one harmonic tremor spike (at least) in Katla volcano. It is unclear why this harmonic tremor spikes happen in Katla volcano. But they often do happen just before a earthquake swarm starts, but often several hours before (sometimes). I am not sure why that is. But one idea is that this activity is connected to hydrothermal areas that are under the Mýrdalsjökull glacier.

Earthquake activity has been quiet in Katla volcano today. But it is hard to know for sure if that is going to last. As earthquake activity appears to be on the rise in Katla volcano during the whole of the year 2011 according to news in Iceland (see earlier blog post for details).


Harmonic tremor spike as seen on Lágu Hvolar SIL station. The spike is between 04/09 and 05/09. The spike is a small top in the tremor chart (hard to spot). Copyright of this picture belongs to Iceland Met Office.


Harmonic tremor spike as seen on Snæbýli SIL station. The spike is between 04/09 and 05/09. The spike is the broad band that suddenly appears in the tremor data. It is easier to see then on Lágu Hvolar. Please note that it seems that Snæbýli SIL station has gone offline again, as it has stopped updating. Copyright of this picture belongs to Iceland Met Office.

It is clear that Katla volcano is going for a eruption. But the question remains is just when that is going to be, but it is impossible to predict when a eruption is going to take place in Katla volcano. But the signs have come clear in my opinion in this matter. For the moment it is just waiting and watching. But this might be a long wait until something happens in Katla volcano.

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Increased earthquake activity in Katla volcano during the past year

In todays news at Rúv News there was a report about Katla volcano. This news has a interview with a Einar Kjartansson geologist at Iceland Met Office about the earthquake activity in Katla volcano. Einar speaks about the earthquake activity in Katla volcano yesterday (3. September 2011). But he also speaks about how activity in Katla volcano has been increasing during this year and it is more then it is normal in Katla volcano. But it is important fact that Katla volcano always has earthquake actvitiy, even with earthquakes up to ML4.5.

He also says that this increased earthquake activity in Katla volcano is due to dike intrusion into Katla volcano or some other activity that is currently taking place in Katla volcano.

Flood in Múlakvísl glacier river

During yesterday and during the night there was a glacier flood in Múlakvísl glacier river. This time around it was not connected to the activity in Katla volcano. But due to heavy rain in this area and melting of the glacier in the heat that has been in Iceland for the past few days. Since then the flood has subsided and Múlakvísl glacier river is back to normal and the flood has subsided.

News about all this.

Aukin skjálftavirkni í Kötlu (Rúv.is, Icelandic)
Braut niður varnargarð (mbl.is, Icelandic)
Miklir vatnavextir í Múlakvísl (Vísir.is, Icelandic)

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Earthquake swarm in Katla volcano

Today (3. September 2011) at 16:45 UTC a earthquake swarm did start in Katla volcano. So far this earthquake swarm has been small, with the largest earthquake just with the size ML2.7 at the depth of 1.1 km (automatic data). But the quality of this earthquake was good, so location is accurate from what I can tell.

I am not sure at this moment if there is a harmonic tremor spike following this earthquake swarm or not. As the earthquakes are long period due the fact that they are created by magma movement in Katla volcano. This might be dike intrusion. But for the moment it is hard to know that for sure.


The area of earthquake activity today in Katla volcano. Copyright of this picture belongs to Iceland Met Office.


The ML2.7 earthquake (automatic size) in Katla volcano caldera. This picture is released under Creative Commons Licence, see Licence web page for more details.


Harmonic tremor plot of the current activity. Latest activity is at the end of the tremor plot. Copyright of this picture belongs to Iceland Met Office.


Harmonic tremor plot of the current activity. Latest activity is at the end of the tremor plot. Copyright of this picture belongs to Iceland Met Office.


Harmonic tremor plot of the current activity. Latest activity is at the end of the tremor plot. Copyright of this picture belongs to Iceland Met Office.

I cannot tell at the moment what is going on in Katla volcano. But the earthquakes tell me that the reason why they are happening is because of magma is moving inside Katla volcano. But latest data (not shown here) do however show that no harmonic tremor is currently ongoing, if it ever started during this earthquake swarm. I am expecting the earthquake swarm to continue and last for the next few hours. But I must point out that that is what might happen, as sometimes earthquake swarms just stop when you think that they might be about to start for real.

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Inflation starts in Katla volcano

There seems to be inflation going on in Katla volcano, at least according to the automatic GPS data that IMO has on it’s web site. But this might be error in the data. But for the moment I do not think it is. But please do look at this data with the view that it might be wrong.


The inflation appears clearly on Lágu Hvolar GPS station. Copyright of this image belongs to Iceland Met Office.

The inflation can be seen on Lágu Hvolar and Sólheimaheiði GPS stations. But it appears to be more clear at HVOL GPS station. But that is most likey because that GPS station is closer to the magma pocket in question that creates this movement.


The inflation also appears on Sólheimaheiði GPS station. But not as clearly as on Lágu Hvolar GPS station. Copyright of this image belongs to Iceland Met Office.

What might be the critical inflation before a eruption starts is hard to know until it happens. For Eyjafjallajökull volcano that was 60mm, for Grímsfjall volcano the inflation was actually 350mm. But that volcano had eruptions that did not change it’s inflation numbers. I do not know why Grímsfjall volcano is so different in this respect from other volcanoes in Iceland (that I know of so far).

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A ML3.2 earthquake (automatic size) happens in Katla volcano caldera

At 18:44 UTC a earthquake with the size ML3.2 and the depth of 2.9 km did happen in Katla volcano caldera (this size is based on automatic data and is going to be subject to a change).


The ML3.2 earthquake in Katla volcano. Copyright of this picture belongs to Iceland Met Office.

Currently there is strong wind around Katla volcano. This strong wind is interfering with IMO SIL network around Katla. But so far no harmonic tremor has been detected after this earthquake.

This earthquake appears to have be formed due to magma intrusion into the rock in Katla volcano caldera. It’s signature on my geophone shows that clearly.


The Z component unfiltered. This picture is released under Creative Commons licence.


The Z component filtered at 1Hz. This picture is released under Creative Commons licence.


All the component on my geophone. This is unfiltered data. This picture is released under Creative Commons licence.


All the component on my geophone. This is filtered data at 1Hz. This picture is released under Creative Commons licence.

This might just be part of normal Katla volcano activity. But it is a fact that it has more earthquakes during the summer and autumn then during the winter. But it is close to impossible to know if this just normal activity or something else. All that can be done is to wait and see what happens.

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Minor harmonic tremor in Katla volcano

There seems to have been minor harmonic tremor in Katla volcano this evening. This harmonic tremor seems to have started after a ML0.7 earthquake with the depth of ~3.7 km did happen inside the Katla volcano caldera. Last harmonic tremor spike did take place on the 24th of August according to the tremor plot on Icelandic Met Office web page.


Harmonic tremor mixed in with the earthquakes from Katla volcano on this tremor plot. Copyright of this image belongs to Icelandic Met Office.


Here is the harmonic tremor that I see on the tremor plot. It is the second spike. But the first spike is actually a earthquakes that did happen earlier today. Copyright of this image belongs to Icelandic Met Office.


This harmonic tremor can also be seen on this SIL station clearly. Copyright of this image belongs to Icelandic Met Office.

On other SIL stations around Katla volcano the signal is not so clear. But this is really a small event and unlikely a pre-eruption event. But it is hard to know it for sure, as Katla volcano has done this before and there was no eruption following this type of events. All that can be done now is to wait and see what happens next. It is also important to notice that Icelandic Met Office has not confirmed this harmonic tremor spike yet.