At the time of writing the eruption at Fagradalsfjall is not only continuing unabated but getting stronger. After the opening of five new fissures, eruptive activity has focused on one crater, fissure 5. Lava now covers the Geldingadalur valley floor and threatens to engulf the first cones; lava has been flowing steadily into Meradalir since 24 April 2021.
Eruptive activity changed from continuous fountaining with effusive lava flows to periodic jetting after midnight on 2 May 2021. The change is thought to be due to degassing of the magma in the upper part of the eruption channel where a small chamber may have formed. Each jet is now accompanied by strong gas emissions. Lava flow, itself, is mostly being carried in lava channels under the crater rim, rather than ejected in the current jets so periodic jetting has not adversely impacted the output.
The onset of jetting can be seen in the tremor plots from local stations. We have included KRI because, being further away, we can see more of the lower frequency lines.
Area of the Geldingadalsgos lava field: 1.78 Km2 (1.41Km2, 03 May 2021)
Volume of erupted lava: 30.7 million m3 (23.0 million m3, 03 May 2021)
Lava discharge rate: 12.9m3/s, (7.5m3/s, 03 May 2021)
Mg0: varies from 8.5 to 9.8
K20/Ti202 ratio: increasing from 0.1 to 0.3
In the first two weeks of the eruption lava flow decreased steadily from 7-8m3/s to 4-5m3/s. In the second two weeks, five new fissures opened with lava flow varying between 5 – 8m3/s. In the two weeks to 3 May 2021, one crater dominated with lava flow increasing. In the week to 10 May 2021, there has been a large increase in the output of lava to 12.9m3/s; the lava field now covers an area of 1.78km2 with a volume of 30.7 million m3. It is thought that the increase in output reflects changes in the lava channel from the mantle to the surface; it has widened over time.
Changes in chemical composition may mean that materials are mixing in the upper mantle before ascent or there is less partial mantle melt in the magma. If the latter, the eruption will end when the mantle source is sufficiently reduced.
Geldingadalsgos is still a toddler compared to Holuhraun; Geldingadalsgos’ eruption rate is 5% – 10% of the average eruption rate at Holuhraun between September 2014 and February 2015. Let’s hope it stays that way as it is a lot closer to residential areas.
La Soufrière St. Vincent
The alert status was lowered to orange after a period of relative quiescence on 6 May 2021; only a few long period events and volcano-tectonic earthquakes are occurring each day. People are allowed back into the orange zone but the red zone remains an exclusion zone.
The last explosive event was on 22 April 2021. However, a possible lava spine was spotted on photos on 27 April 2021. Tephra fills the crater, increasing the risk of pyroclastic flows should eruptive activity pick up again. In the meantime, lahars are the main hazard.
Mount Pelée remains on alert level yellow. Volcano tectonic events are occurring and seismic activity remains at above baseline level. An area of brown and dead vegetation was confirmed on 8 February 2021 caused by diffuse CO2 emissions; the vegetation has not recovered. The volcano is slowly reawakening.
As the new volcano at Geldingadalur continues to grow, opening and closing new fissures, we have returned to our tour of Iceland. We have now reached the Northern Volcanic Zone, where the plate boundary heads northwards from Kverkfjöll to meet the Tjörnes Fracture Zone. Active volcanoes in the zone are Kverkfjöll, Askja, Fremrinámur, Heiðarsporðar, Krafla and Þeistareykir; Herðubreið, itself, is Pleistocene palagonite table-mountain.
We are starting with the currently most seismically active volcanoes, Askja and Herðubreið, located where the Eastern Volcanic Zone meets the Northern Volcanic Zone, north of the Vatnajökull ice-cap. The mantle plume, itself, is thought to be located to the north west of the Vatnajökull ice-cap.
The Askja volcanic system comprises a 1,516 m high central volcano and 190 km long fissure system, the central volcano being the Dyngjufjöll massif. It has three nested calderas, the latest of which formed in a rhyolitic eruption in 1875. The central volcano, itself, is made up of Pleistocene glacio-volcanic tuffs, hyaloclastites, pillow basalts and intercalated sub aerial lava and capped by Holocene sub aerial lavas and pumice. The fissure system, itself, extends from beneath the Vatnajokull ice-cap to the north coast of Iceland and includes small shield volcanoes.
This volcanic system does not erupt frequently; GVP records 14 Holocene eruptions which range from VEI 0 to VEI 5, the VEI 5s occurred in c. 8910 BC and 1875. Askja’s lava types are tholeiitic basalt / picro-basalt and rhyolite. Her main eruption types are effusive basalt with occasion explosive basalt or rhyolite. The 1875 eruption created a 4.5-km-wide caldera which is now filled by Öskjuvatn lake. The most recent eruption in 1961 was a VEI 2 effusive basalt one.
The Askja Fires, 1874 to 1929
Askja was little known before the Askja Fires. The area is sparsely inhabited, sited in lava fields and ash deserts. The Fires occurred during a volcano-tectonic episode between 1874 to 1929.
A steam column rising from the central volcano in February 1874 was the first observed sign that the volcano was active. Northern Iceland was rocked by many large earthquakes in December 1874. Steam and ash were seen in early January 1875 and light ashfall was noted south of Öxarfjörður. By 15 February 1875, 10m subsidence had occurred in the main caldera along with the formation of a crater erupting mud. A basalt lava flow at Holuhraun to the south of Askja occurred around this time.
On 18 February 1875, a fissure eruption started on the Sveinagjá fissure north of the volcano; this generated 0.2 to 0.3km3 of basaltic lava over the course of several months.
On 29 March 1975, the Plinian eruption at the central volcano started in earnest. The initial output was a wet and sticky tephra. Shortly after 05:30, pumice was erupted, reaching as far as Scandinavia; this phase lasted until the following day. The Víti crater was formed later in a short hydro-magmatic episode. The caldera, itself, formed over a period of 40 to 50 years, is now filled by Öskjuvatn lake. As the volume of the new caldera is greater than the calculated erupted volume of lava and ash, it is thought that the excess lava is stored in the fissure system.
In 1929 to 1930, five eruptions occurred on ring faults around the Öskjuvatn caldera, with a 6 km long fissure eruption occurring on the southern side of the volcano that created the Þorvaldsraun lava.
The 1875 eruption is not the first time Askja has erupted rhyolite. Two other instances have been occurred: the c.10ka Skolli eruption and one around 2.1ka; these deposited thick layers of tephra and ash from the latter reached as far afield as Scotland and Sweden.
Holuhraun, which should be familiar to those interested in volcanology, is the area where a fissure eruption occurred in 2014. This time the central volcano responsible was Barðarbunga. At the time there was some concern at the time that the activity in Holuhruan would extend to Askja, triggering a rhyolitic eruption. Fortunately, that did not happen.
Herðubreið is a 1,682m high Pleistocene palagonite table-mountain (tuya) made up of pillow lavas, hyaloclastite, capped by a 300m thick lava shield. Herðubreiðartögl, a small ridge extending from the south of Herðubreið, may be part of the same system. Although Herðubreið is close to the Askja and Kverkfjöll volcanic systems, in the absence of any post glacial activity it not known if it belongs to either system. We are including the volcano here as it is difficult to allocate the seismic activity in the area to each volcano without more local knowledge.
Herðubreið has been studied as an indicator of climate change during the last glacial periods. Werner et al, (1996) proposed that Herðubreið developed in stages from initial sub-aerial, sub-aqueous, subglacial to sub-aerial. The first sub-aerial activity occurred during an interglacial, creating an olivine tholeiitic shield volcano in the vicinity of Herðubreiðartögl. A lull in volcanic activity coincided with the onset of the last ice-age. Activity resumed with the deposition of olivine tholeiites, followed by hyaloclastites in a lake environment until the volcano breached the lake surface to produce subaerial lavas. The tuya, itself, was formed during the last glacial maximum when the volcano erupted pillow lavas under hyaloclastite deposits in the ice-cap; these were later topped by subaerial lavas when the volcano broke through the ice-sheet. At the end of the last ice-age, activity at Herðubreið had ceased, however, Herðubreiðartögl produced some later olivine tholeittic lava flows and ash deposits.
We plotted the area between 64.95°N,17.2°W and 65.3°N,16.0°W, a total of 45,899 earthquakes. As you can see from Fig 4, the area is very active (although perhaps we should not have used green dots in retrospect– Askja looks very unwell as a result).
The latitude v longitude scatter plot shows that activity follows a NE-SW pattern around Herðubreið, with a swarm to the south east; activity around Askja is focussed on the SE section of the caldera with some further east. The plots are data-heavy so we have broken these down by year.
The years with most seismic activity in the sequence are: 2007, 2008, 2014 and 2019.
In 2007 and 2008, there was a swarm that started in Upptyppingar and progressed to Álftadalsdyngja; this is thought to be due to magma movement. 2014 is the same year as the Barðarbunga eruption at Holuhraun; perhaps some of the seismicity is the result of the crust accommodating magma movement in the region, although the swarm here preceded the swarms at Barðarbunga. In 2019, there was a swarm to the east of the Askja caldera.
The earthquake density plots and depth v longitude plots for these years are set out in Figs 8 to 11 below.
Let’s see what the scientists have said. Greenfield et al (2016) have noted from seismic studies that there is considerable melt storage and transportation (movement) under the lower crust in the region (which may or may not be typical of Icelandic volcanoes – more study would be needed); there is likely to be a magma intrusive complex in the shallow crust round Askja; and, the activity round Herðubreið is caused by fracturing in the region.
The region is well monitored due to the risk of another rhyolitic eruption from Askja; this time around one may cause some disruption to aviation and communication systems, by how much would depend on the size and length of the eruption. In the light of the reawakening of Fagradalsfjall on the Reykjanes Peninsula, perhaps the Pleistocene volcanoes should be added to the watch list, although the monitoring of Holocene volcanoes is likely to pick up unusual activity.
La Soufrière St. Vincent
We have not forgotten La Soufrière St. Vincent; our thoughts are still with the islanders. We will do a fuller update soon. In the meantime, the volcano is still erupting and a new lava dome is forming in the crater. The island has lost up to 50% of its GDP. More aid is now reaching the island. For updates, we use News 784 (link below).
Barbados continues to clear up the volcanic ash; this is putting strain on local water supplies. For updates, we use Nation News Barbados.
R. Werner, H. U. Schmincke, G. Sigvaldason ,“A new model for the evolution of table mountains: volcanological and petrological evidence from Herðubreið and Herðubreiðartögl volcanoes (Iceland)”, Geologische Rundschau 85, Article number: 390 (1996). https://link.springer.com/article/10.1007/BF02422244
Thor Thordarson (Faculty of Earth Sciences, University of Iceland) and Al Margaret Hartley (University of Manchester (November 2019). Askja. In: Oladottir, B., Larsen, G. & Guðmundsson, M. T. Catalogue of Icelandic Volcanoes. IMO, UI and CPD-NCIP. Retrieved from http://icelandicvolcanoes.is/?volcano=ASK
“Classic Geology in Europe 3: Iceland”, Thor Thordarson & Armann Hoskuldsson, Terra Publishing, Third Edition, 2009.
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.
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.
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.
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.
Whether the earthquake hotspots will lead to new eruption sites, only time will tell.
For the current status, please consult IMO (link below).
If you wish to watch the eruption , there are local webcams. The link to one is given below.
For this update, our information comes from IMO and the Department for Civil Defence. We will update our earthquake plots later on.
The eruption which started yesterday on a ridge in Geldingadalur has been assessed as a minor one, contained in the valley; the eruptive fissure is around 500m to 700m long; and, there is no ash or tephra. Levels of S02 are low, except near the eruption site; gases can accumulate in the valley or other depressions. The main road to Keflavík from Reykjavík has been opened. However, the road between Grindavík and Þorlákshöfn is closed. The aviation code has been lowered to orange.
The eruption may change without notice. The Department of Civil Defence warn of the potential for new fissures opening either at the current site or elsewhere from the dyke near Fagradalsfjall. Large earthquakes are considered unlikely at the eruption site but the risk for a magnitude 6.5 still remains for Brennisteinfjöll. At the moment seismicity on the Reykjanes Peninsula is much reduced.
Hazards for those visiting the site are getting too close to the lava flow and not being able to outrun any lava that breaks off it; the craters are unstable and may break, releasing a lava flow; and explosions where hot lava meets water-logged ground. The Department of Civil Defence advises observers to keep to the hills surrounding the site. Not that it is easy to get to without a helicopter!
Local webcams have been set up from which the rest of us can watch; one is:
This was going to be a post with an update on the earthquake swarm on the Reykjanes Peninsula, but the magma beat me to it! IMO has just confirmed that a volcanic eruption is underway near Fagradalsfjall at Geldingadalur. The eruption started at 20:45 19.03.2021. It has been named as Geldingadalsgos, after the valley. At the time of writing, the eruption is a small fissure eruption; the fissure is c. 0.5km long.
The public have been advised not under any circumstances go close to the eruption site or on Reykjanesbraut. First responders need to be able to drive freely to assess the situation. Scientists are working on assessing the eruption, the site and possibilities.
People living nearby in Þorlákshöfn have been instructed to stay indoors, close windows and turn up their heating to avoid exposure to any volcanic gases. The Reykjanesbraut has been closed – the main road from the capital region to Reykjanesbær and the international airport at Keflavík.
Here are the updated earthquake plots by the author, anyway. The raw earthquake data has been obtained from IMO; this is confirmed earthquakes to date (19.03.2021 15:00). IMO’s page above gives the more recent earthquakes.
What we see from the plots is that seismic activity has now extended beyond Reykjanes to the west and the swarm is still active. Activity in the swarm is densest to the NE and SW of Fagradalsfjall. The depth plot shows that earthquakes in the swarm are tending to be smaller and shallower.
Extension of the swarm to the west is in keeping with the swarms which have occurred since December 2019.
Let’s hope that this is a “tourist eruption”; our thoughts are with anyone affected by this eruption.
For more up to date information, please consult IMO or the Department for Civil Protection.
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).
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
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
An eruption considered likely; magma c. 1km below the surface.
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).
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.
For the current status and advice, please consult IMO.
3 March 2021 (Updated 07.03.2021 – new plots added).
The earthquake swarm which started on 24 February 2021 between Kleifarvatn and Svartsengi on the Reykjanes Peninsula is continuing.
IMO have raised the aviation code for Krýsuvík to Orange and report a tremor pulse south of Keilir. At the time of writing, no eruption has been confirmed; however, visibility of the area is hampered by weather.
If magma does reach the surface, the most likely scenario is a fissure eruption, which would produce effusive basaltic lava flows and toxic gases, rather than an explosive ashy eruption. If lava meets a significant amount of water, some tephra may be produced.
The likely impact from any eruption is expected to be disruption of air traffic and also road traffic access to and from Keflavík International Airport, if lava flows cross the access road.
Keilir, itself, is a subglacial mound near Krýsuvík formed during the Pleistocene during a fissure eruption. The mound is built of tephra formed when melting ice met magma, topped by lava. Fagradalsfjall, another location associated with the earthquake swarm, is a Pleistocene table-mountain. As lava prefers to take the easy route out, it is unlikely to emerge via these two volcanoes whose lavas would be fairly solid – hence the expectation of a new fissure swarm.
For status updates, please consult IMO.
A local news service that is also providing updates in English is the Reykjavik Grapevine.
Life is not easy for the research scientists monitoring events. Two had to be rescued after having been separated from the main party while studying gas emissions. Spare a thought for the risks they take.
The public have been advised to stay clear of the area at least until it is known where and how lava emerges and where it would be safe to observe the eruption.
In our excitement at the thought of a possible eruption we overlooked the very real risk of larger earthquakes, if the intensity of the swarm continues: up to 6.0 M near Fagradalsfjall and up to 6.5 M in the Brennisteinfjöll range. Be careful if you are in the area.
Update 05.03.2021 23:29
We have plotted the earthquakes with a quality of 99.0 from IMO’s page showing the earthquakes for the last 48 hours for the Reykjanes Peninsula for the period 2 March 2021 to 5 March 2021 (23:29) (we were too slow to capture 1 March 2021). Here are the results. Colour coding in the scatter plots is by day and size reflects magnitude. The geodensity plot is weighted by magnitude.
Here are plots for the entire swarm from 24.03.2021 to 07.03.2021
As noted above, for the latest status please consult the experts: IMO.
A large earthquake swarm started on the morning of 19 July at around 1:30 am at Fagradalsfjall on the Reykjanes Peninsula. The largest earthquake had a magnitude of 5.1M. At the time of writing, there had been 1,635 earthquakes in the last 48 hours recorded on IMO’s website (note that not all of these have been confirmed). IMO’s map and breakdown of the swarm are shown below:
Close up of the Reykjanes Peninsula:
Fig 3: Breakdown of earthquakes by magnitude
This swarm is occurring on the east side of the swarms on the Reykjanes Peninsula which started late last year. IMO have reported that these swarms (still ongoing) are associated with multiple magma intrusions. The aviation code for the area is still green (IMO). IMO are in the process of evaluating the Fagradalsfjall swarm.
The swarm at the Tjörnes Fracture Zone is still ongoing.
The eagle-eyed amongst you will note that there is some seismic activity at Katla. Whether this will result in anything is anyone’s guess at the moment.
We have not yet updated our earthquake data-set for the current swarm. We will wait until IMO has had a chance to confirm more earthquakes
Update 24 July 2020
The swarm at Reykjanes is now less intense. In the meantime, Katla produced a shallow 3.0 M. IMO have remarked that earthquakes in the summer at Katla are not uncommon.
From memory, Katla was seismically active before the intense swarms started in August 2014 at Barðarbunga in the run up to the eruption at Holuhraun. This may have been a coincidence.