Early morning on 9-December-2017 a magnitude 4,1 earthquake took place in Bárðarbunga volcano. This type of earthquake activity is now common in Bárðarbunga volcano after the 2014 (August) – 2015 (February) eruption. The magnitude 4,1 earthquake in Bárðarbunga volcano was the largest earthquake in this swarm, second largest earthquake had a magnitude of 2,8 and happened several hours before.
The earthquake activity in Bárðarbunga volcano is marked by the green star. Copyright of this image belongs to Icelandic Met Office.
This earthquake activity is located in the south part of the Bárðarbunga volcano caldera. Not far from cauldrons (at least two) that are now highly active in hydrothermal activity. If that is going to result in any glacier flood is not known at the moment, but the biggest chance is that the water levels are low at this locations at least for now. After the magnitude 4,1 the earthquake activity has stopped for now.
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Ongoing swarm in Skjalbreidur at the moment too, with a magnitude 3.5
Oldies but goodies: G. Larsson, M.T. Gudmundsson: Eight centuries of periodic volcanism of the Iceland hotspot (1998) https://pubs.geoscienceworld.org/gsa/geology/article-abstract/26/10/943/206805/eight-centuries-of-periodic-volcanism-at-the?redirectedFrom=fulltext
Shows the wider context of rifting episodes and their influence all over the country.
There were a bunch of deep EQs earlier in the same location that caught my attention, but it developing into a swarm like this was very unexpected. Would it be possible for magma to work its way up into this ancient volcano (fissure swarm)?
This is a rift zone. It erupts regularly and last eruption was ~6230 years ago (3350BCE).
https://volcano.si.edu/volcano.cfm?vn=371070 – This area also goes under the name Presthjúkar.
The central volcano of this fissure swarm, Prestahnjúkur, has had some earthquake series in recent years. But the last eruptions as Jón said were a good while back in time.
A new earthquake is appearing on my geophone as I write this. It seems to be coming from the same area in Skjaldbreið.
3 quakes above M3
Laugardagur
09.12.2017 21:25:42 64,407 -20,735 3,7 km 3,9 99,00 0,7 km A af Skjaldbreið
Laugardagur
09.12.2017 19:53:18 64,411 -20,720 5,7 km 3,1 99,0 1,5 km ANA af Skjaldbreið
Laugardagur
09.12.2017 19:20:44 64,412 -20,719 5,0 km 3,5 99,0 1,6 km ANA af Skjaldbreið
Considering how old the magma system there is, this swarm will have to increase a hell of a lot before it can be considered a reawakening.
But does it not look like an intrusion nevertheless: Over 80 earthquakes in a rather short timespan, and depths ranging from around 15 km up to 1,8 km under the summit area of Skjaldbreidur.
I’m curious, Jon,
I don’t have a map, that would show it, handy. IF you drew a line from this 4.1 quake to the volcano at the edge of the glacier near the sea–almost due south–would that line at all approximate any fault in the area, or not?
If you are meaning Bárðarbunga volcano. Then no. South of Bárðarbunga there are other volcanoes not connected to Bárðarbunga volcano.
Not sure about this. Was not an intrusion of Bárðarbunga (and an earthquake over 5 on the Richter) initiating the Gjálp eruption in Grímsvötn volcanic system in 1996? And Gjálp as well as Grímsvötn are situated to the south of Bárðarbunga.
https://www.researchgate.net/profile/Ingi_Bjarnason/publication/274249261_Earthquake_Sequence_1973-1996_in_Bardarbunga_Volcano_Seismic_Activity_Leading_up_to_Eruptions_in_the_NW-Vatnajokull_Area/links/552517050cf2b123c5178183.pdf
Also the text I was linking in before, implies a connection between Öraefajökull and the East Rift Zone (including Bárðarbunga and Grímsvötn): Manning, etal. (2015): Isotopic evidence for interaction between Öraefjökull mantle and the Eastern Rift Zone, Iceland. https://www.researchgate.net/profile/Christina_Manning/publication/263037656_Isotopic_evidence_for_interaction_between_Oraefajokull_mantle_and_the_Eastern_Rift_Zone_Iceland/links/00b4953b442f6a65a6000000/Isotopic-evidence-for-interaction-between-Oeraefajoekull-mantle-and-the-Eastern-Rift-Zone-Iceland.pdf
IMO remarks, “Around 100 earthquakes have been detected in Mt. Skjaldbreidur since last evening, December 9th. At 19:20 last evenning, there was an earthquake of magnitude M3.5. At 19:53 an earthquake of magnitude M3.2 occurred and at 21:25 an earthquake of magnitude M3.7 occurred. The larger earthquakes were felt inland in the south and west part. Today Dec. 10th at 08:48 an earthquake of magnitude M3.8 occured.
Written by a specialist at 10 Dec 09:17 GMT”