Category: Earthquakes

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Interesting earthquakes north of Askja volcano

There is a interesting cluster of earthquakes north of Askja volcano. What is most interesting is the fact that this earthquakes are shallow This cluster of earthquakes is most interesting for the fact that it is shallow. The depth of the earthquakes is from 8.4 km and up to 0.1 km (~100 meters). This suggests that this is a dike intrusion is making. But appears to be growing slowly (a bit unclear at the moment however). But at this time it is impossible to know if this possible dike intrusion makes it too the surface or not.

History tells that it is not unclear for Askja volcano to erupt in small fissures. But that last happened in the Askja eruption in the year 1961.

Currently it is unclear what is going on north of Askja volcano. But this is for sure evolving into something in my opinion. But the question remains how long this is going to take. But this process has already been ongoing now for about 14 months and counting.

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Interesting earthquakes 20 km WSW of Laki in Eldgjá volcano canyon (Katla volcano fissure system)

There are interesting earthquakes about 20 km WSW of Laki. The locations of the earthquakes suggests strongly that they belong to Katla volcano fissure system. Last eruption in this area took place around the year 934. When the Eldgjá volcano canyon was formed. That eruption did destroy a older volcano canyon located in this same area (lava flows volcano ash did fill up that canyon far as I know).

The earthquakes that have been taking place in this area are small. The largest so far has the automatic size of ML1.2, but only ~4 earthquakes have been recorded so far. But what is most interesting about this earthquakes is the depth. The earthquakes that has the best automatic detection by the SIL system has the depth of 0.7 km. But that makes the depth of ~700 meters and that is a shallow earthquake. Given that this area has only fissures and no activate volcanoes. It is not unheard of in Iceland that a fissure eruption to start with no warning at all. Last time this did happen was in Gjálp eruption in the year 1996. Before that a dike intrusion into the bedrock did manage to get to the surface in Askja eruption in the year 1878, when a 25 km long volcano fissure did open up (small compared to Eldgjá eruption around the year 920).

I do not know what is going on in this area at the moment. As the activity so far has been too small to make any clear picture of it. But Katla volcano is a big volcano and it is not out of volcano league to make a new fissure eruption instead of the regular caldera eruptions under the glacier as Icelanders have gotten used to over the past 1000 years or so. Last time this did happen there are suggestions that there was a also a eruption at the same time in Katla volcano caldera. But that this has only been revealed during research over the past 50 years or so in this area.

I have also noted that there is a small increase in earthquakes inside Katla volcano caldera, not far from Austmannsbunga. But at this moment it is too early too know what it means for sure. There is no eruption is imminent in Katla volcano when this is written. Just too be clear on that fact.

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Quiet scene goes into third week

The quiet scene that has been taking place in Iceland over the last two weeks is still ongoing and is now entering it’s third week. Over the last two week there have been less then 300 earthquakes during a single week. In Iceland that is quiet.

All volcanoes in Iceland have mostly been quiet. But there was a unconfirmed earthquake swarm in Grímsfjall volcano. But due to extremely bad weather it was not observed properly by the SIL network. North of Iceland there also has been a unconfirmed earthquake swarm. This earthquake swarm is somewhere north of Kolbeinsey volcano. But due to distance and bad weather it is unknown how big it was. But the largest earthquakes that have appeared on the SIL network did manage to go up to ML3.0 in size. But that is mostly a underestimate on the size of this event. But underestimate on a earthquake size happens when it is far from SIL network and not properly recorded due that.

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Update on the crack in Þingvellir (Thingvellir), Almannagjá fissure

Tonight Rúv did have a news about the fissure that did open up in Þingvellir (Thingvellir) few weeks ago. Now scientists have started to explore this new fissure. So far they have measured that it is about 10 meters deep. It is still unclear how long it is. The current theory is that this new fissure started to open up after the Mw6.8 and Mw6.7 earthquakes in SISZ in the year 2000, or the Mw6.3 earthquake in the year 2008. But that is however unclear at this time.

What appears also to have happened is that ground water have cleaned out loose material in this new fissure. This might possibly have deepened the fissure. But this aspect of this new fissure is still a bit unclear one. But what is the most amazing thing is that the road has not started to collapse earlier then it did. Due how big this new fissure appears to be.

News on Rúv about this. Use Google translate at own risk, as Google does not know what Icelanders are saying.

Furðulegt að ekki hafi hrunið fyrr (Icelandic, video (Windows Media Video), picture, Rúv.is)

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Few earthquakes in Iceland, interesting events at Kverkfjöll volcano

Currently it is quiet in Iceland when it comes to earthquakes. It is also quiet in Icelandic volcanoes. As no volcano shows clear signs that is about to start erupting. But in this quiet period it is easy to miss the earthquake signs that appear in Icelandic volcanoes.

A volcano named Kverkfjöll has been showing increased signs of unrest over the past few years. So far the largest earthquake swarm took place few years ago. When a cluster of ML2.5 to ML3.5 earthquake took place in it. But since then it has been rather quite. But it is my opinion that Kverkfjöll volcano are on the path to a eruption. But so far it is unclear how and when it might take place. As Kverkfjöll volcano is continues to be a rather quiet volcano, even it is showing slightly higher activity then compared over the last few years. A better SIL network in this are accounts for some of the few earthquakes. But not all of them far as I can tell. In the last 48 hours there have been two earthquakes at rather uncommon place in Kverkfjöll volcano. Both events where small, less then mag 2.0 in size. But those events are part of a pattern that did start in Week 12 of 2011. But even it doesn’t look like a lot. There has been continues activity in Kverkfjöll volcano over the past few weeks and this activity appears to be continuing. I am going to write a better post about it later, when I have better picture of what is going on in Kverkfjöll volcano.

Last earthquake swarm that was in the larger size took place in October 2010. My review of it can be found here, Kverkfjöll volcano shows sign of activity (2010).

Other then this it remains quiet in Iceland. That is why I don’t have a lot too write about at the moment.

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Quiet time continues in Iceland

The quiet times that have been ongoing in Iceland for the past few weeks continue. It has been been my experience over the past few years that when this type of long quiet happens. Usually there is a medium to large event that follows it. Sometimes it is volcanic. But in most cases it is a medium (Mb5.0+) sized earthquake that follows it.

But while the quiet time continues I am going to write a short story and publish it on Amazon as a e-book. More on that when I set-up a special blog about my story publishing.

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Overview of Hjofsjökull volcano activity

Hofsfjökull volcano is not among the most activate volcanoes in Iceland. It has never erupted since Iceland got inhabited. The last eruption that took place in Hofsjökull volcano is undated, but took place sometimes in the last 12.000 years or so.

Here is a short overview of the activity since the year 1999 in Hofsjökull volcano. All pictures are from the web site of Icelandic Met Office and copyright of them belongs to them.

Last earthquake swarm took place in Week 47, in the year 1999.

In Week 21, in the year 2008 a harmonic tremor pulse was detected from Hofsjökull volcano. This started at 13:30 UTC on the 24. May 2008.

SIL stations in Iceland showing the harmonic tremor pulse. Picture number one.

SIL stations in Iceland showing the harmonic tremor pulse. Picture number two.

Spectrograph from the SIL station Saurbær (south Iceland, located on the SISZ).

Spectrograph from the SIL station Skrokkalda. This station is located closest to Hofsjökull volcano, along with the SIL station at Hveravöllum hydrothermal area.

During this episode of harmonic tremor one earthquake was detected in north Hofsjökull volcano.

The one earthquake detected in Week 21 in the year 2008. On the week overview for Week 21 in the year 2008 they think that this might have been a swarm of small earthquakes that they where unable to locate. But I do not agree with that, given the data that is published on this event.

Other then this there have been few earthquakes every now and then in Hofsjökull volcano. But besides that it remains quiet and is most likely to be so for the time being.

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Possibility of dike intrusion in Hamarinn volcano

It appears that there is a chance of a dike intrusion in Hamarinn volcano (Loki-Fögrufjöll area). What suggest that there is a dike intrusion starting in Hamarinn volcano is a earthquake swarm that is unusually dense and has a really narrow area. But normal earthquake swarms usually spread over a small area in the align of the fault line.

How this is developing is a good question. But due to lack of earthquakes it is hard to know for sure at the moment. But at the moment it is worth to keep eye on Hamarinn volcano area.

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Deep earthquake in Hofsjökull volcano

Among the most quiet volcanoes in Iceland is Hofsjökull volcano. It has not erupted in at least 12.000 years from it’s main crater (far as I know). But minor fissure eruptions have taken place in the last 12.000 years in the area around Hofsjökull volcano. But they are undated far as I know. Because of that it is now known when the last eruption took place in Hofsjökull volcano. In terms of Icelandic volcanoes, Hofsjökull volcano is more complex then most. South of it lies the Kerlingafjöll volcano. A volcano known for it’s heavy hydrothermal activity. But Kerlingafjöll volcano has not erupted in historical times in Iceland. But they might have erupted in the last 12.000 years without me knowing about it. In the case of Hofsjökull volcano looks are deceiving. According to a geological map that I have of Iceland, in the case of Hofsjökull volcano it has a second magma chamber and a central volcano inside the SW part of it. That volcano is unnamed for oblivious reasons. That volcano might well behave differently then Hofsjökull volcano it self. But I would theorise that this intergrated central volcano inside Hofsjökull volcano is going to be active when Hofsjökull volcano is.

The icecap in Hofsjökull volcano is deep. At it’s deepest point it is 650 meters deep at the most. The deepest points of the icecap are in the main caldera of Hofsjökull volcano. If Chaitén volcano in Chile has teaches geologist anything. It is that a long dormant volcanoes don’t need a long time to go from dormant to active eruption. That is why I find it worrying that deep earthquakes have started to appear in Hofsjökull volcano, even if they are extremely rare so far.

Over the past ten years or so there has been a slight increase in earthquake activity in Hofsjökull volcano along with increase in hydrothermal activity. But so far it has just been a minor earthquakes. The strongest ones getting up to ML3.0 at the strongest. No earthquake swarm have ever been recorded in Hofsjökull volcano to my knowledge (since recording begin in Iceland).. Last earthquake swarm was recorded in Hofsjökull volcano in the year 1999, then a earthquake swarm of 22 earthquakes took place, all of those earthquakes where just minor earthquakes. Besides being one of Iceland largest volcanoes, its location also makes it extremely dangerous. As it is located in the middle of Iceland, and a glacier flood from it could go many different ways down to the ocean and over large populated areas in Iceland. The increase in hydrothermal activity started in Hofsjökull volcano in the year 1994 or about that time. It was at least first documented in that year. A sulphur smell was recorded when the homoeothermal vent was checked out that year in Hofsjökull volcano. Increase in hydrothermal activity in Hofsjökull volcano is interesting as it is followed by a slight increase in earthquake activity over a long period of time.


Location of the two earthquakes. The deep earthquake is the one closer to the caldera. This picture is from Icelandic Met Office web site. The copyright of this picture belongs to them.

The earthquake that started me to get worrying about Hofsjökull volcano is the earthquake that took place 10:11 UTC on 5. April 2011. That earthquake had the depth of 27.6 km. It’s size was ML1.4, so it was a small earthquake. I do not believe that this depth is a result of a error in the SIL system (can happen sometimes). A second earthquake took place at 10:13 UTC, its size was ML1.6 with the depth of 1.6 km.

Whatever that is happening in Hofsjökull volcano is worth watching. Even if it not going to erupt just yet. It is also my opinion that Hofsjökull volcano is not part of Western Iceland Rift Zone (pdf). But its is the most southern part of a failed rift zone often called Skagafjörður volcanic zone (pdf). It is a failed volcanic zone that is mostly extinct, only Hofsjökull volcano and Kerlingarfjöll volcano remain active in that volcanic zone at the most southern end of it.

Other information.

Jarðhiti í Hofsjökli (Tímarit.is, Icelandic, 1996, pdf) – Article with picture of where the hydrothermal vent was found in Hofsjökull glacier.
Hofsjökull (Wiki, english)

Text updated at 18:11 UTC on 6. April 2011. Minor fixes in the text.

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Overview of the earthquake activity in Grímsfjall volcano

Here is a short overview of the activity in Grímsfjall volcano in Week 08 and Week 13 for a comparison. A quick review of the earthquake data on the Icelandic Met Office web page suggests that the current path to a eruption started in Week 07.

It is clear on the pattern that has been evolving over the past four to five weeks where the eruption is most likely going to happen. That location is almost directly below the SIL station that Icelandic Met Office.


Week 08. Picture is from the Icelandic Met Office. Copyright of this picture belongs to Icelandic Met Office. Click on the picture to get full size.


Week 13. Picture is from the Icelandic Met Office. Copyright of this picture belongs to Icelandic Met Office. Click on the picture to get full size.

The evolving cluster of earthquakes can clearly be seen in this week overviews, and other in between them (Week 07 to week 13). It is clear that the magma has found a collection spot inside Grímsfjall volcano. But the question remains where it is going to break it self when a eruption starts. It is rather that question rather then when it happens, given the earthquake pattern that I am seeing coming from Grímsfjall volcano at current time.