While waiting to see where and when the next eruption on the Reykjanes Peninsula occurs, we have updated our earthquake plots for the area between 63.746°N, 22.631°W and 63.996°N, 21.864°W from 24th October 2023 to 9th March 2024 – a total of 12,988 earthquakes. We have extended the area plotted to include Krýsuvík.
First, we start with the geodensity plot for the period 24th October 2023 to 9th March 2024. Most activity is still occurring on the magma intrusion / graben between Hagafell and Stóra-Skógafell. The earthquake density plots for the entire period also picks up some activity southwest of Grindavík, west of Fagradalsfjall and at Mount Þorbjörn. This shows best on a topographic map with a lighter background.
Next, we look at the geoscatter plot for the same area and period. This shows the activity along the magma intrusion / graben, that west of Fagradalsfjall, and, also, an upkick in activity in the Krýsuvík area. The last may be local faults accommodating the uplift at Svartsengi. Whether or not this lets magma ascend in the Krýsuvík volcanic system, itself, remains to be seen. At the time of writing, the alert level for Krýsuvík is unchanged at green.
At the time of writing, the eruption has not materialised. The swarm continues, albeit the magnitude and number of the earthquakes has decreased.
The status of Grindavík has been downgraded from “emergency” to “danger”. The aviation code has been reduced to yellow. If an eruption does ensue from this swarm, the most likely location is between Hagafell and Sýlingarfell.
On 21st November 2023, IMO reported significant uplift in the vicinity of Svartsengi. While an eruption may follow here, it is thought that it would be preceded by an increase in seismic activity. There is still a likelihood of an eruption near the magma intrusion. Since then, uplift has continued.
Fig 33: COSMO-Skymed interferogram spanning 24-hours between 18−19 November at 06:41. The broad uplift signal visible in orange/red around Svartsengi is indicative of inflation occurring at a depth of > 5km. Source: IMO
Fig 34: GPS from IMO showing ground deformation at Svartsengi. There was initial uplift at the start of the swarm, followed by large drop when the graben was reactivated / dike formed, which, in turn, is followed by resumed uplift. Source: IMO.
We have updated our earthquake plots from 24th October 2023 to 26th November 2023 13:27. Most activity is occurring along the magma intrusion, although it is focussed more on the area to the east of Sýlingarfell on Sundhnúksgigar.
Our plots show faults responding to magma, with decreasing seismic activity along the possible dyke formation since the reactivation of the graben. This may reflect the fact that magma has reached less brittle layers or most of the seismicity associated with the magma intrusion was in fact due to tearing of the crust in response to the inflation at Svartseni and environs, which, in turn, may or may not have allowed magma to flow into the formation. Time will tell.
Since our earthquake plots were compiled, there has been another small swarm to the east of Sýlingarfell.
We believe that this is the calm before the storm (an eruption) but when will the storm break?
For updates, please consult the relevant authorities, e.g IMO (link below).
The eruption site is closed to the public right now due to the danger from volcanic gasses and smoke from moss fires; some visitors have been affected. Also, some visitors have been taking insane risks (e.g., attempting to climb the crater wall). High winds yesterday also caused issues.
As we know the eruption started on 10th July 2023 at 16:40 with the opening of four fissures with a combined length of c.800m in a north easterly direction from Litli Hrútur towards Keilir. The eruption peaked at c.21:00, diminishing to form a single crater c. 400m northeast of Litli Hrútur.
Lava is flowing south with an average flow rate of 13m3/s (similar to the 2021 eruption) for the period 11 July to 13 July. As of 13 July 13:38, the lava volume is c. 3.4 million cubic metres covering an area of 0.4km2. Calculations were performed by NLSI from Pleiades satellite images.
The lava composed of vesicular glass, microphenocrysts and microlites of plagioclase, olivine, clinopyroxene and spinel, similar to the 2022 lava. Lava is estimated to have a temperature of c.1190°C. The chemical composition is similar to that of the 2021 and 2022 eruptions: MgO wt.% = 8.5, and, K2O/Ti2O = 0.26.
The gas composition is similar to that of the 2022 eruption, with a high concentration of CO2. The CO2 may have accumulated prior to the eruption. SO2 gas emissions range from 5.4-11.5 ktonnes / day and CO2 is 7.1 – 15 5 ktonnes / day.
If lava continues to flow southwards, it may reach the 2022 lavas in Meradalir.
We have updated our earthquake plots to 13th July 2023 02:06, focussing more on the area between Fagradalsfjall, Keilir and Krýsuvík.
The earthquake density plot is still showing most activity southwest of Keilir and close to the eruption site, which we determined from eyeballing the location of the crater. The area southeast of Keilir is also showing more activity. Whether the activity close to Keilir is triggered quakes, the result of faults moving to accommodate the magma intrusion, or magma-related (or, indeed, both) remains to be seen.
The earthquake swarm which started on 4th July 2023 is continuing vigorously as we write, with 7,000 earthquakes detected. InSAR has confirmed that there is a dike intrusion between Fagradalsfjall and Kelir. IMO have said that magma is likely to have reached a depth of around 1 km by 6th July, causing a fracture of a 2.8 km length between Fagradalsfjall and Keilir, centred a little north of Litli-Hrútur. The expectation is that, if an eruption occurs, it will be in hours or days. The eruption may be short but bigger in its initial stages than the 2021 and 2022 eruptions. The alert level remains at orange.
A smaller swarm is also ongoing southwest of the peninsula on the Reykjanes ridge, near the island of Eldey. This may be due to crustal accommodation of the magma intrusion between Fagradalsfjall and Kelir and/or it may be independent activity. The alert level has been raised to yellow. We will look at this in later posts.
The wrapped image (Fig 2) clearly shows a series of multicolored fringes centered bewtween Fagradalsfjall and Keilir. These fringes show ground deformation caused by the new dike intrusion which commenced on 4 July 2023. The maximum observed deformation related to the dike intrusion is up to 18 cm in the satellite‘s line-of-sight (los) in the NW direction.
Although the deformation signal extends over a large area of the western Reykjanes Peninsula, this does not mean there is magma beneath this entire region. The magma intrusion is situated bewteen Fagradalsfjall and Keilir. There is no indication of additional magma movements outside this area.
Several small lineaments are also visible in the interferogram which cut across the fringes. These represent fault movements/earthquakes that were triggered during the dike propagation.”
We have updated our earthquake plots to this morning, 7th July 2023 09:37 using the published earthquakes from https://skjalftalisa.vedur.is .
Local volcanologist have said that the likelihood of an eruption in a matter of hours or days has increased. The aviation alert level has been increased to orange.
So we have plotted the published earthquakes from https://skjalftalisa.vedur.is from 28th June 2023 to 5th July 2023 20:16 to see what is going on.
It certainly looks like a magma intrusion close to the sites of the recent Fagradalsfjall eruptions. Time will tell whether or not and where lava emerges with the current swarm.
Our thanks go again to the Icelandic Met Office, IMO, https://www.vedur.is/, for the raw earthquake data. For updates, please visit IMO.
Seismic activity continues in the Svartsengi area, extending to the Sundhnúkur crater row. The earthquakes in the vicinity of Mount Þorbjörn appear to be getting shallower today as at the time of writing.
The Sundhnúkur crater row erupted c. 2,360 years ago. It is accredited with creating the Hópsnes/Þórkötlustaðanes land spit to the east of Grindavík.
Fig 8: Bird’s eye view of the Svartsengi area and Gringavík. Image from Google Earth; yellow text added by the author.
Here are our updated earthquake plots to 26th May 2022 15:06.
The following video shows both the geoscatter plots by day from 17th April 2022 to 26th May 2022 in the swarm for the western Reykjanes Peninsula, and the scatter plots for the same period for the area around Mount Þorbjörn.
While the earthquake plots are highly suggestive of more shallow magma ascent, we need to bear in mind that this area is on the plate boundary, the Mid Atlantic Ridge. Some of the seismic activity may be existing faults moving to accommodate the magma. Time will tell when and where magma emerges.
For the latest updates and alerts, please consult with IMO or the local authorities.
Armchair Volcanologist
Original Post 24th May 2022
The earthquake swarm that started on 17th April 2022 on the western Reykjanes Peninsula continues. Today we are plotting activity at the Svartsengi area near Mount Þorbjörn, which lies to the north of Grindavík, Iceland. We have used Mount Þorbjörn as the marker for Svartsengi in our plots.
Fig 1: Image cropped from one by Arian Zwegers of the Blue Lagoon looking towards Mount Þorbjörn. Published under CC-BY SA-2.0. Source: Þorbjörn (mountain) – Wikipedia
IMO reports that there has been significant uplift of 40mm to 45mm during the swarm in the area north of Grindavík indicative of magmatic activity.
From a simpler scatter plot and a geodensity plot, we can see much of the activity has occurred near Mt Þorbjörn or Svartsengi in the area enclosed in the green box below.
An earthquake swarm started on the Reykjanes Peninsula on 17th April 2022 and is continuing at the time of writing. This swarm is part of a larger volcano-tectonic episode that started at the end of 2019 on the Reykjanes Peninsula, including the eruption at Geldingadalir.
Local volcanologists are reporting now that recent ground deformation of 3.5cm suggests a magma intrusion in the vicinity of Svartsengi, north of the town of Grindavík. Magma is believed to be pooling at a depth of c. 4km between Mount Þorbjörn and the Eldvörp crater row. This is an area which can produce large earthquakes of 6.5M. People are advised to avoid areas where landslip is likely.
Fig 1: Image cropped from a photo by Roman Zacharij of Grindavik, Iceland (Source: Wikimedia Commons, Public Domain).
We have updated our earthquake plots to show the swarm to date. Our plots exclude an earthquake occurring earlier today with a depth of 40.7km to keep the detail in the plots showing depth; the earthquake omitted is 19/05/2022, 00:11:14, 63.77°N , 22.75°W, 40.7km, 1 magnitude. Since we downloaded the data at 09:55 am today, there has been a 3.0 magnitude, 4.9 km NNE of Grindavík.
Our plots show possible doming in the vicinity of Mount Þorbjörn and the Svartsengi Volcanic System.
The eruption at Geldingalur, Reykjanes, Iceland, which started on 19.03.2021 at 20:25, is continuing unabated as I write. The volcano is happily bubbling away building somewhat unstable but impressive looking cones and covering the Geldingadalur valley floor with lava.
Fig 1: Cones of Geldingadalur, cropped from an image by Berserkur, published under CC BY-SA 4.0
The eruption is steadily increasing at the time of writing; it has a lava output of 5 -7m3 per second. IMO have estimated that the valley would fill enough for lava to overflow into the neighbouring valley, Meradalir, in a matter of days at the current eruption rates.
Fig 2: Image by IMO. Expected path of the lava over the next few days at the current eruption rate.
Scientists at the University of Iceland are analysing the lava. To date, they have reported that the lava is a primitive one (i.e. little magma evolution in the crust), indicative of a mantle source at a depth of 17 km to 20 km.
Geological Setting
The Reykjanes Peninsula lies on oceanic crust created by the Mid Atlantic Ridge. The Peninsula, itself, straddles the Ridge. The crust here is 15 km thick, which is unusual so close to a spreading ridge. However, Iceland is a basaltic plateau overriding a mantle plume. Both the mantle plume and the Mid Atlantic Ridge influence formation of the crust. There are no magma chambers / reservoirs in the crust on the Peninsula; magma tends to ascend directly from the mantle.
The Peninsula is made up of lava shields, móberg hills, table mountains and fissure-fed lava flows and crater rows. The shield volcanoes on the Peninsula formed at the beginning of the Holocene between 10,000 and 7,000 years ago. Shield volcanoes form from hot picrite or olivine tholeiitic basaltic lava flows with rates of c . 5m3 per second. The móberg hills formed from submarine fissure eruptions and consist of pillow lavas, breccias and tuffs. The table mountains were formed from subglacial activity, which had the activity not been constrained by the ice cap, would have resulted in shields. Later Holocene activity has comprised effusive tholeiitic fissure eruptions which formed crater rows and produced large lava flows that now cover some of the earlier formations. Historic activity has been between 940 AD and 1340 AD, including the Reykjanes Fires of 1210 AD to 1240 AD; and, the Krýsuvík Fires of 1151 AD to 1188 AD.
Geldingadalur, itself, is a small valley to the south east of the summit of Fagradalsfjall, a 385m high hyaloclastite subglacial Pleistocene table mountain formed during the Weichselian glacial period, with a subaerial lava cap on its northwest part. It is currently classified as part of the Krýsuvík Volcanic System.
The Fagradalsfjall area is seismically very active, with large earthquake swarms, notably in 1998, 2000, and 2004, and again now as part of the new volcano-tectonic episode on the Reykjanes Peninsula that started in December 2019. Various studies from previous seismic activity have noted extensive faulting under the south west part of Fagradalsfjall; these faults strike N-S and NE -SW. In addition, there are two clusters of faults under the eastern part.
Earlier swarms in the current volcano-tectonic episode have resulted in magma intrusions, such as the one at Mt Þorbjörn which we discussed last year, but no eruption. The latest earthquake swarm which started on 22 February 2021 is the only one to result in an eruption at the time of writing.
Seismicity in the Current Swarm
We have updated our plots for the Reykjanes Peninsula and dividing them between the run up to the eruption on 19 March 2021 at 20:45 and after the eruption to 26 March 2021 15:55.
The plots preceding the eruption repeat the ones shown earlier so we are just showing the geodensity plot for comparison. You will note that the earthquakes do not reach down to 15 km in the current swarm to date. However, there were one or two deeper earthquake in some of the earlier episodes.
The plots for the period after the onset of the eruption (19.03.2021 20:45 to 26.03.2021 15.55) show that activity is concentrated on Geldingadalur and two spots north east of Fagradalsjall. Seismic activity has also extended further south.
14.03.2021: The magma intrusion on the Reykjanes Peninsula appears to be edging further southward. The longer this continues, the more likely an eruption. New plots added (Figs 13 – 15).
Update 14.03.2021
We have moved updates to the beginning of this post. The original post from 9 March 2021 and the earlier update are below.
We have updated our plots to 14.03.2021 17:46 for the area between 63.83314°N, 22.55148°W to 63.96605°N, 21.8566°W . Here are the results; the magma intrusion appears to be edging slowly further southwards, if we use the Department of Civil Protection’s line that the earthquake locations are the best indicator at the moment of where the magma is.
For the current status and advice, please consult IMO.
The Armchair Volcanologist
Update 12.03.2021
Since we wrote [our original post], the earthquake swarm continues unabated with several thousand more earthquakes and some more tremor pulses.
The Department of Civil Protection report today includes the following:
“Earthquake activity now reaches up to the Nátthagi valley south of Fagradalsfjall, which suggests that the southernmost end of the magma path lies there.
The magma path continues to expand although there is some uncertainty regarding the pace of the magma flow. Data has indicated that the magma path has been moving towards the south coast in the last few days, but latest surveys do not indicate that the path has moved notably in the last 24 hours.
With view of the eruption history and geological research, a volcanic fissure opening south of Fagradalsfjall and reaching the ocean is unlikely. Given the current circumstances, an undersea eruption with associated ash eruption is therefore unlikely.
As has been stated earlier in the Science Board’s notifications, while the magma path continues to expand it must be assumed that an eruption may occur in the area. The longer the current situation lasts, the more likely an eruption becomes. “
They also note that gas measurements are being taken in the area.
Our updated plots show the seismic activity moving further southward, notably the geodensity plot in Fig 12. There is also some parallel activity further west on a much smaller scale.
For the current status and advice, please consult IMO.
The Armchair Volcanologist
09.03.2021
An eruption considered likely; magma c. 1km below the surface.
Good Afternoon!
Despite the earlier tremor pulses, the Krýsuvík Volcanic System has not yet erupted. However, as seismicity continues to be intense, with well over 34,000 earthquakes recorded by Iceland’s SIL system now since 24 February 2021, it is thought that an eruption is likely.
The latest report from Iceland’s Civil Protection Service Council on March 8, 2021, states that if an eruption occurs, the most likely scenario is still a fissure eruption between Fagradalsfjall and Keilir. A magma intrusion (they use the term tunnel) is forming in the region, with most recent activity at its southern end. Magma has now reached an upper depth of c. 1 km. GPS and satellite readings indicate that the magma flow has decreased in the past week. If the intrusion continues to grow, further surges in seismic activity can be expected.
The earthquakes trending westward from the vicinity of the magma intrusion are thought to be the result of the crust accommodating the intrusion. No other magma movement has been detected during this swarm.
So where are Fagradalsfjall and Keilir? Here is a map (with directions on how to drive from one to the other, not that we would recommend that at the moment).
Fig 1: Extract from Google Maps showing the location of Fagradalsfjall and Keilir.
We have plotted the confirmed earthquakes for week 8 and week 9 2021, plus a few hours of yesterday, between 63.7°N, 21.0°W to 64.4°N, 23.0°W download from IMO’s site. Here are the latest plots for the Reykjanes Peninsula, 63.7°N, 21.0°W to 64.4°N, 23.0°W:
If we zoom in on the area between 63.83314°N, 22.55148°W to 63.96605°N, 21.8566°W we can take a closer look at the intrusion, itself, (or the earthquakes magma movement is causing). The area was selected to take in Svartsengi, Fagradalsfjall, Keilir and Krýsuvík.
Since we downloaded the data for the above plots, IMO have reported another short-lived burst in seismic activity at 05:20 this morning with a seismic tremor Mt. Fagradalsfjall, south of the intrusion.
IMO have produced a map of the dike intrusion and the areas of seismic activity that are arising due to the increased tension in the crust caused by the intrusion.
Fig 8: Map by the Icelandic Met Office showing the dike intrusion and the areas of stress.
For the current status and advice, please consult IMO.
28 February 2021 (updated 2 March 2021 with the addition of earthquake plots showing rifting / dike formation)
Good Evening!
A large earthquake swarm started on 24 February 2021 on the Reykjanes Peninsula in the vicinity of the Krýsuvík volcanic system between Kleifarvatn and Svartsengi. At the time of writing the swarm is still ongoing with over 7,200 earthquakes record by Iceland’s SIL system. Three earthquakes of 5.0M or more have been recorded: 5.7M and 5.0M on 24 February and a 5.2 on 27 February 2021.
The alert level for the Krýsuvík volcanic system has been raised to yellow following sightings of steam jets in geothermal areas in the region after the 5.7M and 5.0M.
The Icelandic Met Office have attributed this swarm to the recent re-awakening of volcano-tectonic activity on the Peninsula.
We downloaded the confirmed earthquakes from IMO’s site to take a look. We plotted earthquake density for Week 8, 2021, earthquake locations for February 2021 and earthquakes by month from January 2009 to February 2021.
From our plots we can see the awakening of the volcano-tectonic activity with the upkick in number of earthquakes from December 2019. The current swarm is part of this activity.
At the time of writing, it is not possible to predict whether or not this activity will result in a local eruption in the near future. Only time will tell.
Update 1 & 2 /03/2021
Since writing the swarm has continued, with more than 15,000 earthquakes since it began last week.
The Department for Civil Protection has advised on 1 March 2021, that satellite images show deformation in the area has increased more than expected, indicating possible magma inflow.
We can see from the local GPS stations that there has been significant uplift near Krýsuvík.
Fig 5: Composite GPS plots for KRI, SENG and THOB.
We have also produced scatter plots by day for the swarm in week 8, 2021 which show possible rifting or dike formation.
An Armchair Volcanologist 
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