Earthquake activity in Grímsvötn (Grímsfjall) and Þórðarhyrna (Thordarhyrna) volcanoes

Sorry for the late article. I’ve been busy in other project that involves taking a lot picture and putting them up on my Instagram that can be found here.

Two earthquake swarms have appeared that I am now keeping an eye out for. This is earthquake activity in Grímsvötn (Grímsfjöll) volcano and then in Þórðarhyrna volcano (Thordarhyrna). Last time Þórðarhyrna erupted was in the year 1902 and that was at the same time an eruption took place in Grímsvötn volcano. Over the last few months there has been increase in earthquake activity in Þórðarhyrna and Grímsvötn volcanoes. Its not completely symmetrical increase in earthquakes, but close to it as of writing of this article. Last time Þórðarhyrna erupted without an eruption in Grímsvötn volcano was in the year 1887 (15th August) to 1889 (?).


Earthquake activity in Grímsvötn and Þórðarhyrna volcanoes. Copyright of this image belongs to Icelandic Met Office.

It is going to be a serious problem if an eruption happens in Þórðarhyrna volcano because that volcano is completely covered with a glacier that is up to 200 meters thick or thicker. Other risk factor is that Grímsvötn volcano might erupt outside of the caldera resulting in glacier floods and other problems.

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Earthquake activity in Þórðarhyrna volcano (Thordarhyrna)

During the night of 3-December-2018 earthquake activity started in Þórðarhyrna volcano (no GVP profile, under Grímsvötn volcano profile). Largest earthquake in this swarm had a magnitude of 2,1 and second largest earthquake had a magnitude of 2,0.


Þórðarhyrna volcano is located south-west of Grímsvötn volcano. Yellow dots on this image. Copyright of this image belongs to Icelandic Met Office.

Last eruption in Þórðarhyrna volcano was in the year 1902 December to 1904 12-January and was a VEI=4 eruption. An eruption happened in Grímsvötn volcano at the same time.

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Two strong earthquakes in Bárðarbunga volcano

Today (17-September-2017) at 14:23 UTC two magnitude 3,9 earthquakes happened in Bárðarbunga volcano. This earthquake activity was at the north-east part of Bárðarbunga volcano caldera where earthquake activity has been taking place since September-2015. This earthquake activity is happening due to inflation in Bárðarbunga volcano.


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

Since September-2015 the rate of activity has been dropping. Now earthquake swarm happens every 11 – 18 days or so. Currently there are no clear signs that an eruption is imminent.

Small note on Þórðarhyrna volcano

On the map above a small earthquake with magnitude of 1,3 can be seen in a volcano named Þórðarhyrna. That volcano is part of Grímsfjall volcano system. Last confirmed eruption in Þórðarhyrna volcano was in the year 1902 (December) and it lasted until 12th January 1904. Not many earthquakes happen in Þórðarhyrna volcano and that suggests that an eruption might happen in this volcano without much warning. The eruption before 1902 – 1904 eruption was in 1887 and that eruption lasted until 1889. Suggesting that when eruption happen in Þórðarhyrna volcano they are long lasting and create a lot of damage as this volcano is completely covered with glacier. I make note of this because I suspect that Þórðarhyrna volcano might erupt without much warning in next few years.

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Possible dyke intrusion in Þórðarhyrna volcano

Tonight (05.03.2017) an possible dyke intrusion has taken place in Þórðarhyrna volcano. It’s a small volcano south-west of Grímsfjall volcano and on Global Volcanism Program website it is counted with Grímsfjall volcano eruptions. Last eruption in Þórðarhyrna took place in 1902 at the same time there was an eruption in Grímsfjall volcano (size VEI=4). Before that eruption, the earlier eruption in Þórðarhyrna took place in the year (August 15th) 1887 and lasted for two years (ended in 1889).


Possible dyke intrusion in Þórðarhyrna volcano (south-west of Grímsfjall volcano). Copyright of this image belongs to Icelandic Met Office.

Largest earthquake in this swarm had the magnitude of 2,5 and the second largest earthquake in this swarm had the magnitude of 2,4. Other earthquakes where smaller. It is not possible to know how this is going to evolve since there is a lack of data on Þórðarhyrna volcano due the fact no eruption has happened since the year 1902. That means for now, it is just more wait and see what happens next.

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If people want to keep up with articles in real time (in case of an eruption), it is possible to do so with an RSS feed that WordPress supports. Both for new articles and new comments as they appear. Its an alternative with the email list I currently support.

Harmonic tremor change close to Grímsfjall volcano

There seems to be a harmonic tremor pulse or a change around Grímsfjall volcano. This might be nothing, but the change appears on several SIL stations around Vatnajökull glacier. The harmonic tremor is strongest on Húsbóndi SIL station and Jökulheimar SIL station. This might be something else then magma, glacier movement or sudden flood are an possibility.

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Húsbóndi SIL station. Copyright of this image belongs to Icelandic Met Office.

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Jökulheimar SIL station. Copyright of this image belongs to Icelandic Met Office.

Currently I don’t know what is creating this change in harmonic tremor. I know it is not weather and this is on too many SIL station to be local noise. The SIL station at Grímsfjall volcano doesn’t show any change, so everything is quiet in that volcano. But this is within Grímsfjall volcano fissure swarm that contains the volcano Þórðarhyrna, it last erupted in the year 1902 and has been quiet since (information about eruptions in Þórðarhyrna volcano can be found under Grímsfjall volcano eruption history).

If anything happens I’ll update this article or post a new one.

Earthquake activity in Þórðarhyrna, Bárðarbunga and Kverkfjöll volcanoes

Today (03-June-2014) there was a lot of minor earthquake activity in several volcanoes in Vatnajökull glacier. This is normal earthquake activity and so far nothing to worry about. This appears to be normal micro-earthquake activity in this volcanoes and I don’t see anything suggesting that volcano eruption is going to happen soon.

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Earthquake activity today in volcanoes in Vatnajökull glacier. Copyright of this image belongs to Icelandic Meteorological Office.

Þórðarhyrna volcano

Þórðarhyrna volcano (No GVP link. It is under Grímsfjall volcano GVP information) has been having interesting activity for the past few days. It might have been ongoing longer without being noticed until now. This earthquake activity is interesting since there is normally no earthquake activity in this volcano. Last eruption in Þórðarhyrna volcano took place in the year 1902. Activity in Þórðarhyrna volcano is often connected to eruptions in Grímsfjall volcano.

Bárðarbunga volcano

Some minor earthquake activity has been taking place in the area around dike intrusion location in Bárðarbunga volcano. This is just a minor activity and nothing to worry about.

Kverkfjöll volcano

Some minor earthquake activity is taking place in Kverkfjöll volcano. This earthquake activity is just minor. It is unusual to have earthquake activity in Kverkfjöll volcano. This earthquake activity is clearly a signal of increase of activity in Kverkfjöll volcano, it however does not signal that an eruption is imminent in Kverkfjöll volcano. So far everything remains quiet and might be so for a good while longer. Last eruption in Kverkfjöll volcano was in the year 1968.

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Harmonic tremor detected in Þórðarhyrna volcano

On the 21-November-2013 there was an earthquake swarm in Þórðarhyrna volcano (part of Grímsfjall volcano). This was not large earthquake swarm or a strong one. With the largest earthquake just having the magnitude of 1,9. While I did just suspect it I did not have it confirmed until today that following this earthquake swarm was an harmonic tremor pulse. This harmonic tremor lasted from 03:30 to 06:10 UTC. Based on nearby SIL station this was not a strong harmonic tremor, but this is important because it suggests that something is taking place in Þórðarhyrna volcano. If this is going to lead to an eruption is unknown at current time. This might be a dike intrusion into the volcano at depth, but that has not been confirmed.

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The harmonic tremor pulse can be seen at 21-November date on this tremor plot from Icelandic Meteorological Office. Copyright of this image belongs to Icelandic Meteorological Office.

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The harmonic tremor pulse as it did appear from Grímsfjall SIL station. Copyright of this image belongs to Icelandic Meteorological Office.

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Harmonic tremor pulse as it did appear on Jökulsel SIL station. Copyright of this image belongs to Icelandic Meteorological Office.

This activity might not lead to an eruption, but given the past history of this area and the eruption in Grímsfjall volcano in the spring of 2011 I find it to be highly likely outcome that eruption is going to take place in Þórðarhyrna volcano in near future, it is not possible to know when such eruption might take place. Last eruption took place in Þórðarhyrna volcano in the year 1902, it is not known if any later eruptions have taken place in Þórðarhyrna volcano.

Blog post updated at 14:47 UTC.

Minor earthquake swarm in Þórðarhyrna volcano

Today (21-November-2013) an minor earthquake swarm took place in Þórðarhyrna volcano. All of this earthquakes were small, with the largest having just the magnitude of 1,9. Depth of this earthquakes was from 6,0 to 0,1 km. This minor earthquake activity is now detected for the first time due to a new SIL stations in the area. How long this type of activity has been ongoing is impossible to know since in the past there have been fewer SIL stations in the area.

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Earthquake activity in Þórðarhyrna volcano. Copyright of this image belongs to Icelandic Meteorological Office.

This earthquake activity is not ice-quake activity, since the glacier is frozen now and with temperature down to -19C it is not going to move a lot. Last eruption in Þórðarhyrna volcano was in the year 1910 and it was connected to an eruption sequence that took place in Grímsfjall volcano at the same time (or that is at least the theory).

I am not yet sure what this means long term for activity in this volcano, since I know so little about how this volcano works due to lack of documented eruption history. If this earthquake activity intensifies from what is now taking place there is a small chance of something happening in Þórðarhyrna volcano. For the moment however, this is just a minor earthquake swarm and does not mean anything special. There have not been any changes in harmonic tremor on SIL stations close to Þórðarhyrna volcano.

Historical eruption of Grímsfjall volcano of the year 1783 to 1785

The year 1783 is something that is going to live in historical memory of the Icelandic people for long time to come. The historical memory of Icelanders still remember the eruption of Laki that took place 229 years ago. This eruption is among Iceland biggest eruption in historical times and since Iceland got populated around the year 600 (or around that time, according to new data). It is unclear when the exact eruption started in Grímsfjall volcano and in Þórðarhyrna volcano (a smaller volcano south-west of Grímsfjall volcano, it is inside Grímsfjall volcano fissure swarm). But what is known is that this eruption started sometimes in May.

The eruption started in Grímsfjall volcano it self, it is unclear where exactly it started. Creating a glacier flood that did go down Þjórsá that same month in some part. But was documented that Þjórsá was darker and had worse smell then normally and had more water in it. It was also documented that Skaftá did have more water in it and was darker and had bad smell early spring in Iceland (that means late April or early May). But the glacier flood that must have taken place after an eruption started are not well documented in history best to my knowledge. From what I can read it seems that the eruption of Grímsfjall volcano started in the main volcano (unknown where exactly). The years 1755 and to the year 1785 seems to have been extremely active in terms of volcano activity in Iceland. But that year there was also an eruption on the Reykjanes Ridge that created a short lived Island. It did however only last few months at the best. It is possible that the eruption on the Reykjanes Ridge was in the area of Eldey or close to it. But it is impossible to confirm it for sure.

It is not known when the actual eruption started in Grímsfjall volcano or in Þórðarhyrna volcano. But it has been assumed from what I can gather that Þrórðarhyrna volcano was also erupting during this eruption. But the reason for that might well be due to dike intrusions from Grímsfjall volcano might have started an eruption in Þórðarhyrna volcano. But best to my knowledge, there have not been many eruptions in Þórðarhyrna volcano since the eruption in the year 1783 (or around that time).

According to documented history, the fissure eruption started around 8. June 1783. This fissure eruption had growing earthquake swarms before it took place. This was due (but they did not know this at the time for obvious reasons). When the eruption started, it started with a large ash cloud that did go down Skaftárhrepp and nearby area. Following this ash cloud was a lot of gas pushing up with the erupted material. But blue haze was reported in historical documents about this eruption. The problem with the carbon-monoxide did not get any better . Given the year this did happen, there are holes in the event as they did happen. But by 12th of June 1783 the lava had already filled several canons at least and had already destroyed a lot of farmland and farms. But it is documented that lava bombs where known to have been found up to 112 km distance from the eruption. The total fissure length is around 25 km long. It is among Iceland longest eruption fissure in historical times. But Askja volcano had an fissure eruption that was around 20 km long in its eruption episode around the year 1875 to the year 1961, when it took a break that is continuing to this day.

Based on historical documents. It seems that this eruption had two phases. The the first one started with an eruption in the south part of what is now the eruption fissure of Laki. The second one was when eruption craters did open up north part of the fissure after several months of eruption on the south part of the eruption fissure. But by that time the eruption had already diminished in strength at the same time, or before that. It is hard to know from historical documentation what actually did happen at this time. But the eruption is believed to have stopped on 26 May 1785.

Many of the eruption craters did make ash, not lava. The ash layers from those craters where up to 2 meters thick at the distance of 500 meters in some areas. It is also believed that the eruption strokes from many of the craters where up to 800 to 1400 meters high when they where at the tallest. During this eruption there was a sour rain, along with other deadly effects that did follow this eruption. It did also happen during this eruption that many animals did die due to ash poisoning, and gas poisoning from the eruption. Just as humans did at this time. But at this time Iceland did not have any functional government that was able to handle this type of natural disaster. The amount of volcanic gases also had effects around northern hemisphere. But this effects did create huge problems in Europe, Canada, U.S and in Russia from best of my knowledge (it might however not be correct).

Many people might believe that after such a big eruption Grímsfjall volcano would stop for a long time. This was not the case. Only 22 years after the major eruption of the year 1783 to 1785 Grímsfjall volcano had an new eruption. This was smaller, only having the VEI scale of 2. But Laki eruption has the VEI scale of 4+. Before the Laki eruption, there had been an other eruption in the year 1774, but it was an minor VEI=2 eruption. Last eruption in Þórðarhyrna and Grímsfjall volcanoes was in the year 1902. That was an VEI=4 eruption that lasted from December 1902 and until January 1904.

For this reasons I classify Grímsfjall volcano (including also Þórðarhyrna volcano) one of the dangerous volcanoes in Iceland. I do think it might be even be more dangerous the Katla volcano all considered. But this is just my personal opinion and nothing else.

Based on following references

Skaftáreldar 1783 (Icelandic)
Grímsvötn (Icelandic)
The eruption that changed Iceland forever (BBC News)

Blog post updated at 01:49 UTC on 22.03.2012.