Seismic and volcanic activity in Iceland.
Apologies for not posting for a while now. Illness in the family has made more demands on our time than anticipated.
We have missed the eruptions of Mauna Loa and Kilauea, to name but two, and two catastrophic earthquakes: one in West Java in Indonesia and the other in Khost, Afghanistan.
Even when we are not posting, our thoughts remain with all those impacted by volcanic and seismic hazards.
Greetings of the season,
Armchair Volcanologist
Eruptive activity at the new fissure in Meradalir stalled on 21st August 2022 at around 6:00 am. The seismic tremor ceased following the emission of a blue grey plume. Lava was seen on webcams to be still flowing from the crater just before then. We await to see whether or not this is the end of this eruptive episode.
To quote IMO, “A new chapter is about to begin in the Fagradalsfjall fires, but whether the seismic activity will recur and it will erupt again in the near future or not, time will tell.”
What do we know of the eruption so far? The eruption started on 3rd August 2022. The initial discharge rate was c. 32 cubic metres per second, dwindling to 2 cubic metres per second by 16th August 2022. The total volume of lava emitted by 16th August 2022 was 12 million cubic metres, c. 8% of that emitted by the Geldingadalir eruption last year. At the crater the lava is 20 to 30 metres deep and 40 metres deep by the crater rims, themselves. Over the rest of the lava field the lava is between 5 and 15 metres deep. The new lava has displaced cooling older lava causing it to rise by 3 to 5 metres in places.
The lava composition is similar to the basalt emitted by Geldingadalir in September 2021. The K2O / TiO2 ratio ranges from 9.3 to 9.4 and the MgO is around 8.4 wt(%).
Armchair Volcanologist
© Copyright remains with the author; all rights reserved, 2022.
Sources: in the text
So, it was hours, not days! The eruption started near Fagradalsfjall / Meradalir yesterday at around 13:18 about 1.5 km north of Stóra-Hrut on a north-easterly southwest fissure. The onset was detected by a local webcam and later confirmed by scientists. The alert level is currently orange (Volcanic eruption is underway with no or minor ash emission.)
Like the previous eruption, lava is contained by the local geography so no infrastructure is currently threatened. Gas emissions are, however, a hazard. The lava flow is estimated to be 5 – 10 times that of Geldingadalir at 32 cubic meters per second in the first 24 hours; gas emissions may well be similarly larger.
Visitors are advised not to approach the site at the moment. When the site is open, bear in mind that it is not an easy walk, so for the fit only, and visitors should be properly prepared, including having gas masks and metres.
A video made by Reykjanes Grapevine shows the eruption site yesterday: RVK Newscast #203: New Volcanic Eruption In Iceland – YouTube
Seismic activity has decreased since the onset of the eruption. We have now updated our earthquake plots to 4th August 2022 10:27- see below.
Updated earthquake plots
At the time of updating, we did not have confirmation of the coordinates of the eruption site, so we have guessed based on maps of the fissure. The plots will be updated when more up to date information becomes available.
Happy volcano watching and stay safe.
Armchair Volcanologist
© Copyright remains with the author; all rights reserved, 2022
Sources: within the text
Updated 04/08/2022, Fagradalsfjall
A new eruption started at c13:18 yesterday, 3rd August 2022. We are following this on a new thread, A New Eruption Near Fagradalsfjall, Iceland, Started 3rd August 202.
Update 02/08/2022, 20:39:46, Fagradalsfjall and Grímsvötn
The earthquake swarm near Fagradalsfjall continues unabated. The aviation code for Grímsvötn has been raised to yellow following increased seismic activity there.
Fagradalsfjall
At the time of writing IMO were reporting 3,000 earthquakes in the last 48 hours detected by the SIL Seismic Network.
Rising magma has caused some large triggered earthquakes where existing faults slip to accommodate the strain, the largest so far being 5.47 on day 2 of the swarm.
The Icelandic media are reporting that new satellite images taken on 1 August 2022 show magma movements located between Fagradalsfjall and Keilir. The magma intrusion is shallow at c. 1 km below the surface. The magma influx is close to double the rate of the previous eruption. The chances of an eruption near Fagradalsfjall in the coming days or weeks have therefore increased and are considered to be significant.
We have updated our earthquake plots using confirmed earthquake data from IMO’s Skjálfta-Lísa for the area 63.75°N, 23.0°W to 64.0°N, 22°W (the western Reykjanes Peninsula). The geodensity plot shows that most of the action is centred north east of Fagradalsfjall.
Grímsvötn
The image from IMO below shows the earthquake activity at Grímsvötn.
Hopefully, eruptions are not like buses – wait for ages, then several show up together. On a more serious note, if Grímsvötn does erupt, ash may be problematic for Europe depending on the size of the eruption and the prevailing wind direction. A jökulhlaup caused by melting of the ice-cap is another hazard. An eruption near Fagradalsfjall is less likely to produce a lot of ash unless magma encounters an aquifer or other body of water; lava and any gas emissions depending on volume and location are likely hazards. Seismic activity remains a hazard for both; the public are advised of the risk of rockfall and landslip.
Armchair Volcanologist
© Copyright remains with the author, all rights reserved, 2022.
Source:
Raw earthquake data: Skjálfta-Lísa
News report: Kvikugangurinn liggur mjög grunnt | RÚV (ruv.is)
Original post 31/07/2022
A large earthquake swarm started yesterday (30/07/2022) lunchtime north east of Fagradalsfjall, Iceland. At the time of writing, IMO had reported 1,597 earthquakes in the last 48 hours for the Reykjanes Peninsula from the SIL seismic network. This network automatically detects and locates earthquakes in Iceland and the surrounding offshore region. 199 of these earthquakes had been confirmed.
At the moment the swarm is being likened to the swarm in December 2021, which did not result in an eruption. The local authorities are warning of the increased risk of rockfall as a result of increased seismic activity.
We have downloaded the earthquakes reported from the Table tab and plotted the confirmed earthquakes (quality 99.9%).
For more up to date information, please consult the Icelandic Met Office, Home-page – Icelandic Meteorological Office | Icelandic Meteorological office (vedur.is)
Armchair Volcanologist
Sources: in the article.
Good Evening!
Update 26th May 2022
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.
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.
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.
Let’s look at the earthquakes.
Western Reykjanes Peninsula
Initially, we updated our plots of the area between 63.75°N,23.0°W to 64.0°N, 22°W. Here is a summary.
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.
Let’s look more closely at the area around Mt Þorbjörn.
Svartsengi Area, 63.81°N, 22.5°W to 63.90°N, 22.35°W
For more up to date information on the seismic activity and the latest alerts, please refer to the local authorities or the Icelandic Met Office, IMO.
Armchair Volcanologist
© Copyright remains with the author; all rights reserved, 2022.
Sources
Raw earthquake data: IMO
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.
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.
Armchair Volcanologist
© Copyright remains with the author; all rights reserved, 2022
Sources
Raw earthquake data: Icelandic Meteorological Office
From Iceland — Magma Collecting, Increased Earthquakes At Reykjanes (grapevine.is)
Good Afternoon!
An earthquake swarm started near the Reykjanes and Eldey volcanic systems on 17th April 2022. A volcanologist was reported by the Icelandic media to have said that there is a 50% chance of another eruption on the Peninsula by the end of this year. If the eruption occurs offshore, the resulting ash may reach Reykjavik and beyond. Another possibility is that Fagradalsjall may erupt again.
So we decided to plot the earthquakes on the Reykjanes Peninsula from 1st January 1995 to 26th April 2022 for the area 63.6°N, 23.5°W to 64.2°N, 21.0°W by month. The results are interesting.
Intense earthquake activity starts early 1995 in the east of the region to the south east of Hengill near the Hrómundartindur volcanic system, which has not erupted since the early Holocene. Activity migrates slowly westward to Geirfuglasker via Krýsuvík, Fagradalsfjall, Reykjanes, and the intensity of activity near Hrómundartindur lessens. The volcano-tectonic episode which resulted in the eruption at Geldingadalir started in month 300, the eruption, itself, started in month 315.
We have discussed the Hengill, Brennisteinfjöll, Krýsuvík and Reykjanes volcanic systems in an earlier post (Recent Seismic Activity on the Reykjanes Peninsula, 14th May 2020) The Hrómundartindur system is about 25 km long, comprising a fissure swarm and a 500m high central volcano. The system lies at the junction of the Western Volcanic Zone and the South Iceland Seismic Zone. Its lavas range from picrite to basaltic andesite. There is an active geothermal field in the system. The Eldey volcanic system is a 40km long fissure system on the Mid Atlantic Ridge, here, the Reykjanes Ridge. There is no central volcano. It is mostly submarine; the island Eldey and the skerries, Eldeyjardrangur, Geirfugladrangur and Geirfuglasker, are the only subaerial features of the system. Six small submarine/explosive Basaltic eruptions have occurred in the last 1,100 years, the last eruption occurring in 1926 CE.
We would not like to predict where the next eruption will be based on the above earthquake plots alone, other than to say it could be anywhere between Hrómundartindur and Geirfuglasker. Our non-expert interpretation of the above plots is that magma is ascending between Krýsuvík and Reykjanes. The seismic activity to the east and west of that area is caused by resulting stress on the crust; whether there is enough activity to provide an additional path for magma remains to be seen. Time will tell where and when magma makes it to the surface again.
Armchair Volcanologist
© Copyright remains with the author; all rights reserved, 2022.
Sources
Reykjavik Grapevine: From Iceland — RVK Newscast 179: Underwater Volcano On The Cards (grapevine.is)
Kristján Sæmundsson (Iceland GeoSurvey) (2019 November 15). Hrómundartindur. In: Oladottir, B., Larsen, G. & Guðmundsson, M. T. Catalogue of Icelandic Volcanoes. IMO, UI and CPD-NCIP. Retrieved from http://icelandicvolcanoes.is/?volcano=HRO
Guðrún Larsen (Institute of Earth Sciences – Nordvulk, University of Iceland) (2019 November 15). Eldey. In: Oladottir, B., Larsen, G. & Guðmundsson, M. T. Catalogue of Icelandic Volcanoes. IMO, UI and CPD-NCIP. Retrieved from http://icelandicvolcanoes.is/?volcano=ELD
Raw earthquake data: Icelandic Meteorological Office
Good morning!
The earthquake swarm is continuing on São Jorge as we write, albeit it at a much lower intensity. The swarm is located on the Manadas Fissure system. INVOLCAN has sent a team to assist the local scientists (CIVISA and IVAR). CIVISA advised on 6 April 2022 that volcano-tectonic earthquakes had been detected suggesting magma movement at depth.
While we wait to see what transpires, here are some statistics.
We have updated our earthquake plots for 38.548°N, 27.677°W to 38.769°N, 28.350°W from 19th March 2022 to 7th April 2022.
Armchair Volcanologist
© copyright remains with the author; all rights reserved, 2022.
Sources
IPMA – Seismic Map (for raw earthquake data)
Volcano-tectonic tremors recorded for first time on quake-hit Azores island | Reuters
Good Morning!
At the end of 2021 a large earthquake swarm started to the west of the Ok shield volcano in Iceland. At the time of writing the swarm is ongoing. The Icelandic Meteorological Office (IMO) reported on their Icelandic site on 1st February 2022 that there is no evidence of magma intrusion.
The swarm is occurring west of Ok in Borgarfjörður in a low temperature region outside the main volcanic and rift area. The earthquakes are thought to be rifting caused by horizontal tension in the crust, here of the North American Plate. The swarm is the largest to date in the region and is continuing at the time of writing. So off we trotted to plot the earthquakes.
What’s in the Area?
We looked at the area 64.2°N, 19.2°W to 65.3°N, 21.8°W which contains the Langjökull ice cap, two Holocene volcanic systems and several Pleistocene volcanic systems.
The Langjökull ice cap is the second largest ice cap in Iceland located at the northern end of the Western Volcanic Zone (WVZ). The WVZ is a slow spreading rift that forms the western boundary of the south Iceland microplate. Sinton et al.’s study in 2005 showed that there is no evidence for the decline in the WVZ in the Holocene; the shield eruptions are long duration with low effusion rates fed by magma from the mantle. c. 40 eruptive units have been located in the WVZ; we are focussing on those in the Langjökull area in the northern part of the zone.
Holocene Volcanoes
| Volcano | Latitude | Longitude | Last Known Eruption | Dominant Rock Type |
| Prestahnúkur | 64.583 | -20.666 | 3350 BCE | Basalt / Picro-Basalt |
| Langjökull | 64.85 | -19.7 | 950 CE | Basalt / Picro-Basalt |
Prestahnúkur is west of the Geitlandsjökull glacier in the south west part of Langjökull. It is a 90 km ling 15 km wide fissure system with a rhyolitic peak, on a Pleistocene basaltic plateau. The central volcano is a hyaloclastite massif; it has shield forming olivine tholeiite basaltic effusive eruptions, with some rhyolite. The fissures extend southwest-north east, reaching under the Þórisjökull and Geitlandsjökull glaciers. There is a parallel sub swarm of tuyas 4–6 km west of the main swarm. The last significant eruption of the central volcano was in the Pleistocene and on the fissures c.900 CE. The Holocene eruptions occurred on rift zones to the north and south west of the volcano.
Langjökull comprises the Hveravellir central volcano and a 100 km long and 20 km wide fissure system. A 600m thick ice cap partly covers the system. The central volcano is another hyaloclastic massif with a silicic component. It has had six recorded Holocene eruptions: 2 VEI 2, Hallmundahraun 950 CE and Kjalhraun 5850 BCE; and, 4 VEI 0, Lambahraun 2050 BCE, Krákshraun 2550 BCE, Strytuhraun 3550 BCE and Leggjarbrjótur 8600 BCE. The Hallmundahraun lava flow covers 240 km2 . Kjalhraun is a shield which erupted 11km3 lava 7,800 years ago. The dominant magmas are olivine tholeiite basalt.
Skjaldbreiður is a shield volcano that lies in the southern part of the Langjökull system. It erupted 13km3 of basaltic lava in the early Holocene. The lava flows formed the basin of Þingvallavatn and Þingvellir, where Iceland’s parliament, the Alþing, was founded in 930.
Pleistocene Volcanoes
| Volcano | Latitude | Longitude | Primary Volcano Type |
| Geysir | 64.32 | -20.3 | Stratovolcano |
| Hlöðufell | 64.93 | -20.53 | Tuya |
| Þórisjökull | 64.53 | -20.7 | Subglacial |
| Ok | 64.62 | -20.88 | Shield |
| Eiríksjökull | 64.77 | -20.4 | Tuya |
| Hrútfell | 64.73 | -19.72 | Tuya |
| Bláfell | 64.492 | -19.87 | Tuya |
| Hreppar | 64.42 | -19.5 | Fissure vent(s) |
The Geysir geothermal area lies in the Haukadalur basin near the southern end of the Langjökull system. Earthquake activity in June 2000 temporarily activated the normally somnolent Grand Geysir
Eiríksjökull is Iceland’s largest tuya.
Ok erupted during interglacials in the Pleistocene. It used to have a summit glacier, the Okjökull, whose disappearance has been attributed to climate change. Local volcanologists have reminded us that the ash from the 2010 Eyjafjalljökull eruption would have contributed to ice loss. “Not Ok” was a documentary about the lost glacier. Ok overlies some of the tuyas of the sub swarm to the west of Prestahnúkur.
Hreppar is two NE-SW trending ridges which extend from the rhyolitic Kerlingarfjöll volcano located SW of the Hofsjökull ice cap.
Recent Seismic Activity
As we have extended our database of Icelandic earthquakes back to 1995, we have plotted the earthquakes for the period from 1995 to 7th February 2022 for the area 64.2°N 19.2°W to 65.3°N 21.8°W.
There is a relatively low level of background activity compared to the other volcanic regions of Iceland. However, the following months each saw more than 200 earthquakes: 55 (July 1999) near Þórisjökull and Prestahnúkur , 66 (June 2000) near Geysir, 67 (July 2000) near Geysir, 69 (September 2000) near Geysir, 155 (November 2007) near Hveravellir and Geysir, 240 (December 2014) near Geysir, 325 (January 2022) near Ok and 326 (February 2022) near Ok. Note: that February 2022 is only one week.
We noted six warms to the west of Ok, including the current swarm. They appear to be aligned along a rift / fissure. The current swarm near Ok is one of the largest in the database to date.
Our geoscatter and scatter plots (including a rotating 3D scatter plot of the earthquakes to the west of Ok) are contained in the following video.
It’s not clear from the plots, themselves, whether or not there is any magma movement associated with the current swarm or, indeed, any of the other activity identified. The size of the current swarm indicates that something may be going on near Ok. Only time will tell if volcanic activity will ensue. In the mean time, the plots do shed some light on the activity along rifts associated with plate seperation.
Armchair Volcanologist
© Copyright remains with the author; all rights reserved, 2022.
Sources and Further Reading
Icelandic Meteorological Office: www.vedur.is for raw earthquake data
Kristján Sæmundsson (Iceland GeoSurvey) (2019). Prestahnúkur. In: Oladottir, B., Larsen, G. & Guðmundsson, M. T. Catalogue of Icelandic Volcanoes. IMO, UI and CPD-NCIP. Retrieved from http://icelandicvolcanoes.is/?volcano=PRE
Guðrún Larsen and Magnús T. Guðmundsson (Institute of Earth Sciences – Nordvulk, University of Iceland) (2016): Langjökull, Hveravellir. n: Oladottir, B., Larsen, G. & Guðmundsson, M. T. Catalogue of Icelandic Volcanoes. IMO, UI and CPD-NCIP. Retrieved from http://icelandicvolcanoes.is/?volcano=LAN
John Sinton, Karl Grönvold, Kristján Sæmundsson, “Postglacial eruptive history of the Western Volcanic Zone, Iceland”, Geochemistry, Geophysics, Geosystems, AGU, Volume 6, Issue 12, December 2005, https://doi.org/10.1029/2005GC001021
For the Pleistocene volcanoes we consulted Wikipedia and the Smithsonian Institution – Global Volcanism (www.volcano.si.edu/)
Good afternoon!
Seismic activity at Fagradalsfjall, Iceland, has remained low. The recent swarm is now considered over. The aviation code has been lowered to yellow as a result.
Armchair Volcanologist
© Copyright remains with the author; all rights reserved, 2022.
Sources:
Aviation colour code map: https://en.vedur.is/earthquakes-and-volcanism/volcanic-eruptions/
Icelandic Met Office: https://en.vedur.is
An Armchair Volcanologist 
#/media/File:Blue_Lagoon_(6818651629).jpg){kind=link}
.JPG){kind=link}
_julesvernex2.jpg){kind=link}