Þórðarhyrna – Iceland geology

June 29, 2023

Earthquake in Þórðarhyrna volcano

Today (29. June 2023) at 07:48 UTC an earthquake with magnitude of Mw3,1 took place in Þórðarhyrna volcano. This was just one earthquake and a minor Mw1,3 earthquake happened at 08:17 UTC and since then its been quiet. Þórðarhyrna volcano is inside Grímsfjall volcano fissure swarm but is an independent volcano in this setting. Sometimes Þórðarhyrna and Grímsfjall erupt at the same time.

Green star in south part of Þórðarhyrna volcano. Not many other earthquakes on the map. Time on map is 29. June, 23, time 13:20 Icelandic time. — Green star in Þórðarhyrna volcano. Copyright of this image belongs to Icelandic Met Office.

Last eruption in Þórðarhyrna volcano took place around late 1890 or early 1900. I am not sure what year exactly, because eruption often attributed to Þórðarhyrna volcano took place in Grímsfjall volcano and sometimes the reverse happened. Last eruption took place around 120 to 140-ish years ago.

May 11, 2023

Earthquake swarm in Þórðarhyrna volcano

Today (11. May 2023) there was a earthquake swarm in Þórðarhyrna volcano. This are small earthquakes, but their location and depth suggest that this is a dyke intrusion taking place at this location.

Earthquake swarm in south-west part of Þórðarhyrna volcano. This volcano is located in Vatnajökull glacier, just few km south of Grímsfjall volcano, is part of the Grímsfjall volcano fissure swarm. Time on image 11. May. 23 13:10. — Earthquake activity in Þórðarhyrna volcano. Copyright of this image belongs to Icelandic Met Office.

Þórðarhyrna volcano is part of Grímsfjall volcano fissure swarm, that connects to Laki eruption fissures. Last eruption in Þórðarhyrna volcano was in the year 1902 to 1904 and had the VEI=4 according to Global Volcanism Program report that can be read here.

June 11, 2020

Increased gas and hydrothermal activity detected in Grímsfjall volcano

It was reported yesterday (10-June-2020) in the news at Stöð 2 (Channel 2) that hydrothermal activity and gas output from Grímsfjall volcano has been increasing in recent months. This has been followed by increased earthquake activity in Grímsfjall volcano. There is now a risk of an eruption following a glacier flood from Grímsvötn lake but according to the Vísir news the lake is getting close to full or at the point where it can flood and empty the crater. That can start an eruption because of the pressure drop of the magma.

Seismic energy released by earthquakes in Grímsfjall volcano since last eruption in May 2011. Copyright of this image belongs to Icelandic Met Office.

It is expected by experts that next eruption in Grímsfjall volcano is going to be a normal eruption but the eruption in May 2011 was the largest eruption in Grímsfjall volcano in 138 years. Since last eruption of this size took place in the year 1873 and then it took 10 years before next eruption took place.

There has also been a minor increase in earthquake activity in Þórðarhryrna volcano but because of lack of data it is difficult to know what that means. Last eruption in Þórðarhyrna volcano ended in January 12, 1904. It erupted at same time as Grímsfjall volcano according to historical documentation.

Icelandic News in Icelandic

Merki um aukið útstreymi kvikugass úr Grímsvötnum (Vísir.is)

April 11, 2019

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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December 3, 2018

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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September 17, 2017September 17, 2017

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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March 5, 2017

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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RSS feed

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.

September 5, 2016September 5, 2016

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.

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

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.

June 3, 2014

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.

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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November 27, 2013November 27, 2013

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.

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.

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

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.

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