Volcano and earthquake activity in Iceland
This evening on 16-October-2022 an strong earthquake swarm started close to Geirfugladrangur and Eldeyjarboða on the Reykjanes ridge. At the writing of this article the strongest earthquake had a magnitude of Mw4,4 but that might change without warning.
It is difficult to know how this earthquake swarm is going to evolve but there are clues in this activity that this might be a large earthquake swarm. However, activity in this area is also known to just stop without warning.
The police and Icelandic Met Office have now advised people not to go to Mýrdalsjökull glacier. This is after the earthquake swarm earlier today. According to Icelandic Met Office this earthquake swarm is similar to what happened before the minor eruption in Katla volcano in July 2011 that resulted in a glacier flood down Mýrdalssand and destroyed the bridge over the glacier river in that area. All trips to see ice caves in Mýrdalsjökull glacier have been temporarily forbidden by the Icelandic Police.
In July 2011 it took around 24 hours from the start of the earthquake activity then until something happened. If that is going to be case now I don’t know. That this activity is similar to July 2011 eruption is worrying. The eruption in July 2011 was minor and didn’t break the glacier, but it resulted in damage in that area from the glacier flood.
Largest earthquakes now have the magnitude of Mw3,8 and Mw3,0 (few of them). Other earthquakes have been smaller in magnitude but that might change without warning.
Today (16-October-2022) an earthquake swarm started in Katla volcano in Mýrdalsjökull glacier. Largest earthquake at the writing of this article had a magnitude of Mw3,8. I don’t know if it was felt in nearby towns and farms. Second largest earthquake had a magnitude of Mw3,0.
This earthquake swarm is ongoing at the writing of this article and the situation can change quickly. This might be a normal earthquake swarm and nothing more might happen. This type of earthquake swarm is not uncommon and I am not sure what is required for an eruption to start in Katla volcano.
This is a tricky thing to write about. Because nothing has started on the surface and might not start on the surface. It seems that something is going on in Grímsfjall volcano. Since the glacier flood is almost over or has finished the harmonic tremor level should have started dropping, it has not done so and I am not sure why that is. This might be boiling of the hydrothermal systems in Grímsfjall volcano when the pressure on the suddenly drops. Currently the harmonic tremor doesn’t look like it has reached eruption levels, that might change without warning.
It is difficult to know what is going on. Since there seems to have been a change in Grímsfjall volcano after the big eruption in May 2011. What that change is I don’t know. It seems to have slowed down Grímsfjall volcano eruption rate from what it was, its been 11 years since last eruption. It might continue if no eruption starts now following the small glacier flood that just ended.
Yesterday (12-October-2022) an earthquake swarm started south and east of Grímsey island. This is in the same area as an earthquake swarm took place few weeks ago. Largest earthquakes so far in this swarm had a magnitude of Mw3,5. Larger earthquakes remain a possibility. Largest earthquakes have been felt in nearby populated areas.
This area has frequent earthquakes. This earthquake swarm might grow as sometimes happens. It might also equally just stop, since that is also something that earthquake swarm in this area do.
Today (12-October-2022) at 14:18 UTC an earthquake with magnitude of Mw3,5 took place in Krýsuvík-Trölladyngja volcano. This earthquake was followed by few smaller aftershocks. This earthquake seems to be happening because of a inflation that is taking place in Fagradalsfjall volcano and this strongly suggests that inflation in Fagradalsfjall volcano is slowly reaching critical levels. There is no eruption expected from Krýsuvík-Trölladyngja volcano as is.
This earthquake activity suggests that more stronger earthquake activity is possibly on the way. When it might start is difficult to know for sure. This has been the pattern in recent months. Earthquake activity starts to appears like this and then one day a major earthquake swarm starts. What happens now is a wait and see as before.
According to a news on Rúv. A small glacier flood is expected from Grímsfjall volcano tomorrow. This glacier flood is not expected to create any problems for roads or bridges. Last glacier flood took place in December 2021. The glacier flood is expected to appear in the glacier river Gígjukvísl.
Icelandic news and announcement of the glacier flood
Lítið hlaup úr Grímsvötnum (Icelandic, Icelandic Met Office)
Von á litlu hlaupi úr Grímsvötnum á morgun (Icelandic, Rúv.is)
Since yesterday (06-October-2022) the earthquake activity has been increasing in the volcanoes Fagradalsfjall and Reykjanes volcanoes. Please note that Global Volcanism Program has updated the informations regarding Fagradalsfjall mountain and now classifies it as its own volcano, this is after a new report and information from Icelandic Met Office. From now on I am going to use that classification when updating on activity in Fagradalsfjall volcano. I’ll not update older articles (too much work), but this also applies to them as such.
This also means that Fagradalsfjall is a new volcano in Iceland.
Earthquake activity at start of an eruption cycle in Fagraldsfjall volcano are not large. They grow larger once magma has started to push into the crust, until then the earthquake activity only seems to happens with minor earthquake swarms.
Article updated with new information.
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According to GPS data from Icelandi Met Office that can be viewed here for Krýsuvík-Trölladyngja volcano (Þorbjörn) and here for Reykjanes volcano. It seems that a inflation period, at least in Krýsuvík-Trölladyngja volcano started in early September and is ongoing at the writing of this article. Earthquake activity is low at the moment, but the area has already moved a lot in recent earthquake swarms and that might he dropped the crustal stress in the area. It might also explain some of the GPS movements. I have some, but limited understanding of reading GPS data so my assessment might be off, wrong or both.
There also seems to be inflation going on, without many earthquakes in Reykjanes volcano. That seems to be have been going on since start of August. There have not been any eruption in Reykjanes volcano even after repeated inflation and deflation cycles in the volcano. Inflation cycles often have earthquake swarm activity if dyke activity follows an inflation event. That does not seem have happened this time around.
If this inflation continues, in either one or both volcanoes. It is clear a new period of high earthquake activity is about to start on Reykjanes peninsula. When that earthquake activity is going to start is impossible to know. Since recent earthquake and volcano activity has changed how the crust works in the parts of the Reykjanes peninsula where magma has been active. Since hot magma slowly softens the hard rock in the crust at depth and that lowers the earthquake activity. Rather then at the start of an volcano activity, when the crust is cold and brittle, resulting in high earthquake activity before an eruption.
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