Ongoing earthquake swarm close to Keilir mountain

The earthquake swarm with Keilir mountain continues today (2-October-2021) and largest earthquake at the writing of this article had a magnitude of Mw4,2. This might change without warning.

Green stars on Reykjanes peninsula close to the mountain Keilir. Shows where the current activity is.
The earthquake activity close to Keilir mountain. Copyright of this image belongs to Icelandic Met Office.

Based on what I am seeing it is my view that magma is the reason why this earthquake activity is happening. The magma seems trapped, based on the earthquake activity and that is interesting. This suggest that the feeder channel, that possibly started at this location has closed up and that is the reason why the eruption in Fagradalsfjall mountain stopped. At least that is the working idea, if it is true I don’t know.

Department of Civil Protection and Emergency Management and Icelandic Met Office has warned people against going to Keilir mountain because of risk of volcano eruption or large earthquakes.

It is unclear at the writing of this article if there are changes to hydrothermal activity close to Keilir mountain. There have been reports about it, but they remain unconfirmed at the writing of this article.

There is now a risk of an earthquake with magnitude of Mw6,0 in the area of Keilir mountain. The earthquake activity shows a pattern of high and low activity every few hours. Why this happens is not well understood at the writing of this article.

11 Replies to “Ongoing earthquake swarm close to Keilir mountain”

  1. Jón, many thanks for your article. The mention of a possible upsurge in geothermal activity are particularly interesting. I can’t remember whether it was Þor­vald­ur Þórðar­son or a different expert. But some knowledgeable person said the reason for steam emissions around Keilir was that geothermal heat was closer to the surface, and thus, heating the ground water to boiling. I imagine you would relate the unusual harmonic tremor graph patterns (seems odd to have the ‘main block’ of the pulsing pattern consistently between 2000 and 3000, with multiple needle spikes) to your idea of a blockage in the magma ‘supply infrastructure’?

  2. Hi,
    the Nasa Worldview fire/hotspot picture doesn´t show any hot areas around Keilier, as of 02 Oct. .
    Don´t know … we´ll see.

  3. If the water of the Keilir geothermal field is involved, could this result in a phreatiomagmatic explosion? Eventually creating a maar?

  4. A While back it was reported on a BBC Horizon TV Show that Volcanoes tend to Pressurise before the Blow with 2 forms of earth quake the sharp rock cracking wave that happen fast then die a away quickly and the Slower Pressure wave

  5. I am taking few days off in Reykjavík. I’ll only write a new article if something major happen. Like a new eruption starts or an large earthquake happens.

  6. There are a few things that are obvious. There is still gas escaping from the main vent so some small amount of magma is still being transported to the site but likely leaking out under the surface and is not visible. As the existing lava cools, it creates a lot of cracks due to shrinking and this small amount of lava could be filling those cracks. But we do see gas coming from a couple of different places in Geldingadalir.

    So far as can be determined from satellite data, there is no surface deformation associated with the latest quake swarm so there is no rapid/massive intrusion of magma. In fact, the latest graphic I saw showed what looked like possibly a slight drop in surface height in the area.

    It appears the quake activity as of today is starting to reduce but that can change suddenly. As I type this there has not been a quake of any size in almost 2 hours. It is possible that these quakes are due to a reduction in pressure causing stress in the opposite direction. The rock will move when pressure increases and it will also move as the pressure declines. Only time is going to tell us what will happen. If I had to place a wager, my gut says the chances are greater that this eruption is coming to an end than the chances of any major new eruption but thank goodness I am not a gambler because every time I say something like that, the opposite happens.

  7. George B – I certainly agree that it would not be good to wager money on anything connected with this eruption!!!

  8. Jón, I imagine the peculiar thin lines on the Harmonic tremor plot yesterday were due to an equipment issue?
    I hope you enjoyed your break in Reykjavík – at least the Sunday/Monday offered better weather.

    1. The break was good. I got to see one film and that film was Dune. I am now back to working and I am working on few things connected to my seismometer network. I am going to keep one seismometer in Iceland, in Hvammstangi after I move to Denmark. With current hardware and limitations that is all I can do. I need to fix the computer that I plan on using and update its install of Debian Linux (Windows is unusable for this task).

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