Earthquake activity in Brennisteinsfjöll volcano (Bláfjöll)

Yesterday (26. January 2024) and today (27. January 2024) an earthquake activity took place in Brennisteinsfjöll volcano, in the Bláfjöll area. The first earthquake had a magnitude of Mw2,4 at 22:54 UTC on 26. January 2024 and the second earthquake had a magnitude of Mw3,1 on 27. January 2024 at 05:28 UTC. Smaller earthquakes started later today. That earthquake activity seems to have ended at the writing of this article.

Green star in Bláfjöll area in Brennisteinsfjöll volcano to the east side of the Reykjanes peninsula.
Earthquake activity in Brennisteinsfjöll volcano and other areas on Reykjanes peninsula. Copyright of this image belongs to Icelandic Met Office.

This earthquake activity, at least in the case of the Mw2,4 and Mw3,1 earthquake did show a sign that they where created by magma movement, among those signs was a strong vertical movement and low period signal that only happens when magma creates earthquake. At this point in time, I don’t think an eruption is going to happen any time soon. It is possible that magma has started to collect in Brennisteinsfjöll volcano. It is going to be several years until something more happens, it might even take decades before anything serious happens.

Earthquake swarm in Brennisteinsfjöll volcano

I am sorry that I am late on writing this article. I was moving from Denmark to Iceland and that was a lot of effort and I’ve been tired after this move.

On Sunday, 24 September 2023 an earthquake swarm took place in Brennisteinfjöll volcano, in a area called Geitarfell (Goat Mountain) in Brennisteinsfjöll volcano. Largest earthquakes had a magnitude of Mw3,0 to Mw3,2. A lot of smaller earthquakes took place at this same location.

Yellow dots at the location where the Sunday earthquake swarm took place. There's a lot of earthquake activity on the Reykjanes peninsula at the moment. Shown with two green stars, one at Svartsengi and the other in Kleifarvatn lake.
Yellow dots show the Sunday earthquake activity. Copyright of this image belongs to Icelandic Met Office.

This earthquake activity didn’t have any short term signs that an eruption is about to happen at this location. I don’t know when last eruption took in this location, but it was clearly more than 6000 years ago.

Earthquake webicoders

Since I have moved back to Iceland. I am now recording earthquakes again. The webicoders are going to go online tomorrow (if no delays). They can be found here once they are back online.

Dyke intrusion into Brennisteinsfjöll volcano

During the night of 26. August 2023 an dyke intrusion started in Brennisteinsfjöll volcano. This was in the form of many small earthquakes, most of them did not reach magnitude Mw1,0. What gives this away as an dyke intrusion is the fact the deepest earthquake in this swarm had a depth of 21,1 km. There was interestingly, a lot of surface earthquakes. I am not sure on why that is.

Yellow dots in Brennisteinsfjöll volcano the east of Fagradalsfjall volcano on Reykjanes peninsula. A lot of smaller earthquakes all over the Reykjanes peninsula on this map. Time on map is 26. August 2023 at 17:00 Icelandic time.
Earthquake activity in Brennisteinsfjöll volcano. Copyright of this image belongs to Icelandic Met Office.

There’s no risk of eruption at the moment from Brennisteinsfjöll volcano. Earthquake activity is too low and this process is clearly not far along now for an eruption too happen. That might change without much warning at some point.

Small earthquake swarm in south part of Brennisteinsfjöll volcano

Today (13. April 2023) there has been a small earthquake swarm in south part of Brennisteinfjöll volcano. This location had an earthquake swarm few weeks ago at this same location. It also was small in magnitude. Depth of this earthquake swarm has now decreased from 7 km to around 3 km. At least that is what it seems, based on the current earthquake data.

Red dots in south of Brennisteinsfjöll volcano showing the minor earthquake activity now taking place in this volcano. Nearby volcano also have minor earthquake activity, shown in orange to red dots.
Earthquake activity in Brennisteinsfjöll volcano. Copyright of this image belongs to Icelandic Met Office.

This earthquake activity shows a sign of magma movement. It is my opinion that the magma is now pushing it self trough the crust at this location. That can take a while, up to several weeks before an eruption starts. I did see something similar happen before the Bárðarbunga volcano eruption in 2014. That process took good three months before the eruption and was marked by small earthquake swarm like this one. How long this is going to take is impossible to know, because what type of crust is at this location is not well understood (outside of types of rock it is made out of at the first top layers). This is in my view an earthquake activity that needs to be monitored, because of possible eruption risk at this location. This is directly north of a small lake south of the earthquake swarm. If an eruption happens and the lava flows into the lake, that might create a lot of problems.

This earthquake swarm can be viewed here in more details. The website is Skjálfta-Lísa and is only in Icelandic.

Earthquake swarm in Brennisteinsfjöll volcano (Bláfjöll mountain)

Earlier this week, an swarm of earthquakes started in south of Brennisteinsfjöll volcano, also known as Bláfjöll mountain. This earthquake swarm started on a west to east fault north of a lake called Hlíðarvatn. This earthquake swarm has only been minor earthquakes, with magnitudes in the range of Mw0,0 and up to Mw2,3 but at the writing of this article, nothing above that magnitude. Over the week this earthquake swarm has evolved into a single area that seems to be circular, based on current earthquake activity. This strongly suggests that magma is the reason why this earthquake swarm is happening.

Red dots in south of Brennisteinsfjöll volcano. Showing the earthquake activity in that volcano. Red dots are also visible in Hengill volcano in a unrelated earthquake swarm.
Earthquake activity in Breinnisteinsfjöll volcano. Copyright of this image belongs to Icelandic Met Office.
Dots in different sized showing the earthquake swarm in Brennisteinsfjöll volcano. This is a image from Skjálfta-lísa website from Icelandic Met Office.
Earthquake as they appear on Skjálfta Lísa website from Icelandic Met Office. Screenshot from Icelandic Met Office website Skjálfta Lísa.
Google Earth image of the area where this earthquake swarm is taking place. It shows the road, the Hlíðarvatn lake and other feature in the landscape. Including a old lava flow the west of the current earthquake swarm. The landscape also seems to show older craters at this location, but those are weathered down to almost nothing.
Google Earth image of the area where the earthquake swarm is taking place. Picture is from Google Earth.

At the writing of this article, the earthquake activity is too small to start an eruption. Since this area is cold and the crust is too hard for the magma to flow freely inside it. Current depth of the earthquakes is around 5 to 7 km at the writing of this article and has not changed a lot during the week. While the Skjálfta Lísa image does not show this, it is possible that the earthquake activity has started to spread more east, compared to earlier in the week when this activity started. This earthquake actiivty might stop, as often happens in the early stages of a new eruption cycle in a volcano.

Earthquake swarm in Brennisteinsfjöll volcano

Today (21-October-2022) an earthquake swarm took place in Brennisteinsfjöll volcano. Largest earthquake had a magnitude of Mw3,0 at 10:23 UTC. This earthquake swarm is possibly over, it is however difficult to be sure.

Red dots in Brennisteinsfjöll volcano on Reykjanes peninsula, located just south of Reykjavík city and east of Kleifarvatn lake. A lot of yellow and orange dots on the map in few volcanoes showing smaller earthquake activity
Earthquake activity in Brennisteinsfjöll volcano and other nearby volcanoes. Picture is from Icelandic Met Office.

This is probably just a tectonic earthquake activity. But it is worth noting that volcano activity as has been seen in Fagradalsfjall volcano (Iceland newest volcano) is going to move east on Reykjanes peninsula. How fast and how long that change is going to happen is not known because of lack of data and written records from 700 to 900 years ago are incomplete and vague on details at best.

Strong earthquake in Brennisteinsfjöll volcano

Today (14-May-2022) at 16:56 UTC an earthquake with magnitude of Mw4,8 took place in Brennisteinsfjöll volcano. This earthquake was clearly felt in Reykjavík, Selfoss and large parts of south and south-west Iceland. Depth of this earthquake seems to be 7,8 km.

Green star on the east part of Reykjanes peninsula in a area called Þrensli. With several red dots around showing smaller earthquakes. To the west there is a dense swarm of earthquakes in Reykjanes volcano and green stars to west of that
Earthquake activity in Þrensli, just south of Reykjavík city. Copyright of this image belongs to Icelandic Met Office.

It is unclear in my personal view if this is just a normal fault earthquake that might be possibly connected to SISZ or if this is because of stress changes from all the inflation of Krýsuvík and Fagradalsfjall volcanoes. There is a chance of larger earthquake in this area following this earthquake. When that earthquake might happen is impossible to know.

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Article updated at 04:56 UTC on 15-05-2022.

Earthquake in Brennisteinsfjöll volcano

On 24-May-2021 at 21:36 UTC an earthquake took place in Brennisteinfjöll volcano. The magnitude of this earthquake was Mw3,6 and this earthquake was felt in Reykjavík area.

Green star in the middle of the image of Reykjanes peninsula showing the location of the earthquake that was felt in Reykjavík.
The location of the earthquake in Brennisteinfjöll volcano. Copyright of this image belongs to Icelandic Met Office.

There have been few smaller earthquakes in this area since the largest earthquake, but other than that it has been quiet. This earthquake is believed to have happened because of stress changes on the Reykjanes peninsula because of the eruption in Fagradalsfjall mountain.