Month: July 2021

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Earthquake activity north of Grindavík town in Reykjanes volcano

Early morning of 11-July-2021 an earthquake swarm took place north of Grindavík town. Largest earthquake in this swarm had a magnitude of Mw2,5. Most of the other earthquakes had a magnitude of Mw0,0 to Mw1,0. There was also an earthquake swarm on Reykjanestá area that is part of Reykjanes volcano.

Earthquake activity north of Grindavík town show as cluster of small orange dots on Icelandic Met Office image.
Earthquake activity on Reykjanes peninsula in Reykjanes volcano. Copyright of this image belongs to Icelandic Met Office.

It is difficult to know for sure what this earthquake activity means for this volcano. Since it has already been proven that eruption activity can start on Reykjanes peninsula without any warning or earthquake activity. Currently there are no clear indicators that suggest anything is about to happen but that can change without warning.

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Update on Fagradalsfjall mountain eruption on 9-July-2021

This is a short update on the eruption in Fagradalsfjall mountain that is part of Krýsuvík-Trölladyngja volcano system (currently, this might change in the future).

  • Since 23:00 UTC on 5-July-2021 the eruption has been on the low side and no lava has been seen leaving the crater when the fog is less dense in the eruption area. This is the longest break in the eruption activity since it started in 19-March-2021.
  • Small amounts of lava has been seen in the crater and it is speculated that it might be flowing from the crater in tubes in the lava field. This remains unconfirmed at the writing of this article.
  • Currently the eruption is not over. It is ongoing as is.

The following is a speculation on my part.

This lack of activity and amount of lava in the crater suggests that the deep system that has been feeding the eruption is for now close to being empty or is completely empty. That system of magma chambers needs time to fill up. This lack of activity is also common for this type of volcano and magma system. Since eruptions go trough a cycles of high and low activity. This might result in the eruption starting in a new fissure in next few weeks to months along with continuing in the current crater. There is also a equal chance of the eruption just continuing in the current crater once the eruption starts at full energy again. But that might be weeks until that happens.

End of speculations

Summer is fog season in Iceland when there is no strong wind and this has been a problem for monitoring the eruption on Reykjanes peninsula in recent days. This is going to continue until September or October depending on the weather pattern.

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Fagradalsfjall mountain eruption refuses to stop (2-July-2021)

In a surprise move the activity in Fagradalsfjall mountain (part of Krýsuvík-Trölladyngja volcano system) started to increase again around 16:00 UTC and around that time the first lava was seen in the crater after it had emptied it self out during the night as was mentioned in last article.

I have been following eruptions for a long time and this is the first time that I see this happen in a crater eruption. Normally when they collapse in this way the eruption is normally over. In this case the magma cleared out the rock from the collapse over few hours (it just goes down the stream with the lava) and the eruption started as the pressure did build up again in the deep magma system. Harmonic tremor has increased again since 16:00 UTC. I don’t know if it has reached its maximum yet. That is possible, but difficult to be sure.

Red hot lava from the crater flows down on Rúv web camera. Small drown is in frame of the shot.
The eruption as it appeared on Rúv web camera. Copyright of this image belongs to Rúv ohf.

It is impossible to know for sure what this eruption does next. Since this eruption seems to be breaking a lot of the normal rules that happens during an eruption.

Harmonic tremor going almost vertical up on the SIL station Fagradalsfjall.
The harmonic tremor on the SIL station Fagradalsfjall. Copyright of this image belongs to Icelandic Met Office.

Currently there is a lot of lava flowing into Nátthagi and possibly also into Geldingadalir that is already full of lava and is about to overflow at lowest points in next few days.

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Possible end of the eruption in Fagradalsfjall mountain (2-July-2021)

At the writing of this article the eruption in Fagradalsfjall mountain has possibly ended (please note that Icelandic Met Office has not officially called the end of this eruption). This is part of Krýsuvík-Trölladyngja volcano system.

Around 03:43 UTC on 2-July-2021 the crater started erupting a cloud of volcano ash. What was unclear until earlier today was that the eruption had ended in the crater. The reason for the ash cloud was the the crater was collapsing in on it self and sealing up.

Cloud of volcano ash from the crater at around 03:43 UTC.
The volcano ash cloud as it appeared on Rúv web camera during the night. Copyright of this image belongs to Rúv ohf.

The harmonic tremor has also dropped at the same time as there is no lava flowing from the crater.

Harmonic tremor on SIL station Fagradalsfjall. The lines are showing up and down pattern and in last few hours the lines drop down to background noise. Few spikes have appeared in the last few hours but unclear what they mean.
The harmonic tremor noise on SIL station Fagradalsfjall mountain. Copyright of this image belongs to Icelandic Met Office.

What happens next is unclear. It is unlikely that eruption is going to start in the crater that stopped erupting. Normally they almost never erupt again. Magma is going to find it self a new path to erupt once a pressure has build up again in the deep crust. Once the pressure is enough it is highly possible that new earthquake swarm is going to start before an new eruption happens on the Reykjanes peninsula. How long this is going to take is impossible to know for sure.

This is the last article about Fagradalsfjall until an earthquake or a new eruption starts in Fagradalsfjalli mountain.