Seismic crisis and eruption March 2021 on the Reykjanes Peninsula: activity updates - part 1

Earthquake swarm continues, more than 2000 quakes during past 48 hours
Update Mon 15 Mar 2021 06:41
Earthquakes on the Reykjanes peninsula during the past 48 hours (image: IMO)
Earthquakes on the Reykjanes peninsula during the past 48 hours (image: IMO)
The volcano-seismic unrest continues on the southern Reykjanes peninsula, centered around Fagradalsfjall mountain.
A strong mag. 5.4 earthquake occurred yesterday 14 Mar 2021 at 2:15 pm local time 5.4 km SW of Fagradalsfjall. It was widely felt in the area, and even captured by the webcam:
Likelihood of volcanic eruption near Fagradalsfjall increases by the day
Update Fri 12 Mar 2021 16:06
Recent earthquakes in the Reykjanes peninsula
Recent earthquakes in the Reykjanes peninsula
Latest satellite images and GPS data show that accumulation of magma is concentrated at the southern part of the dike beneath Mt. Fagradalsfjall. This is the most likely site for a possible eruption. InSAR image reflects changes between March 3 to March 9 2021. Image contains modified Copernicus Sentinel data [2021] (image: IMO)
Latest satellite images and GPS data show that accumulation of magma is concentrated at the southern part of the dike beneath Mt. Fagradalsfjall. This is the most likely site for a possible eruption. InSAR image reflects changes between March 3 to March 9 2021. Image contains modified Copernicus Sentinel data [2021] (image: IMO)
The earthquake swarm in the Reykjanes peninsula, concentrated in the area around Mt. Fagradalsfjall SW of Keilir, continues with no signs of weakening. By early afternoon, the Iceland Met Office (IMO) had already recorded over 1700 earthquakes since midnight alone, including many of magnitude 3 or higher and a widely felt magnitude 5 event at 07:53 GMT this morning.
This seismic activity has been identified as result of continuing influx of magma into a newly forming dike (sheet-shaped magma reservoir) at shallow depth, of only about 1km beneath the surface in places. The longer it continues the higher the likelihood of it breaching the surface, or in other words causing a volcanic eruption.

Icelandic scientists concluded that "the dike intrusion is expanding with the most active magma flow centered at the southern part of it. A volcanic eruption remains a possibility as magma is still flowing into the corridor. With the ongoing activity the probability of an eruption increases day by day. It is considered very unlikely that lava from a possible eruption would reach populated areas.

The latest report by IMO further states:
- It is important to follow the activity in the southern region of Mt. Fagradalsfjall in order to evaluate whether the dike is expanding to the south.
- Latest satellite images and GPS data show that accumulation of magma is concentrated at the southern end of the dike beneath Mt. Fagradalsfjall. This is currently the most likely site for a possible eruption.
- If the dike keeps expanding and increasing stresses in the area, continuing earthquake activity that can be felt in populated areas is expected.
- Currently, the magma is shallow, lying 1-1,5 km beneath the crust. Therefore, it can be expected that an eruption could start without a strong precursory signal, as the magma can easily brake through the last hundreds of meters of the crust once the critical pressure is reached. From experience of lava flow eruptions (as we might expect), the eruption tremor is weak and has a low amplitude. For this reason, the IMO has installed webcams which can be used to monitor the area, in case of an eruption will start without clear precursory signals.

Geophysical survey leads to visualization of magma chamber under Reykjanes Peninsula

Update Thu 11 Mar 2021 07:30
Sketch showing the forming magma reservoir, a dike, under the Reykjanes peninsula (image: RUV)
Sketch showing the forming magma reservoir, a dike, under the Reykjanes peninsula (image: RUV)
In recent reports, the Icelandic Meteorological Office (IMO) stated that magmatic movements are the likely cause of the ongoing earthquake swarm in the Reykjanes peninsula. As magma migrates upwards, overlying rock layers are displaced, which causes tremors and ground deformation on the surface.
Geophysical surveys were conducted along the area of unrest located in between Fagradalsfjall and Keilir. The results generated a detailed look at how the expanding magma chamber under the Reykjanes peninsula behaves.

Expanding magma chamber under the Reykjanes peninsula
In an interview of the Icelandic National Broadcasting Service (RUV) with geophysicist Freysteinn Sigmundsson on 9 March 2021, the growing magma reservoir was shown to be in the form of a dike: It is currently about 1 meter wide and 7 kilometers long spanning the length between Keilir at the northern end and Fagradalsfjall at the southern end. The bottom of the magma chamber is located 5 kilometers below ground surface and is the site for magmatic influx. This is the process by which magma flows from deeper sources in the mantle towards the shallow magma chamber where it is now being stored.
15-20 cubic meters of magma flowing into the reservoir
Based on the rate of deformation, allowing to estimate the increase of volume of the dike, the magma influx was measured to be about 15 to 20 cubic meters per second.
The northern end of the magma chamber lies 2 kilometers deep under Keilir, while the southern end lies only a kilometer deep under Fagradalsfjall. Due to this orientation of the magma chamber, geophysicists believe that it is possible that the magma underneath Keilir may have already cooled down and solidified or is about to. An eruption in this area is thus less likely than in the area of the southern end of the dike, i.e. near Fagradalsfjall. It also means that there are more seismic and magmatic activities at the southern end near Fagradalsfjall.

Greatest volcano-seismic activity near Fagradalsfjall
According to geophysicist Sigmundsson, if magma continues to flow into the magma chamber, it will expand into the area with least resistance. This means that the magma chamber will expand southward as that portion is closer to the surface. Magma might eventually reach the surface causing an eruption near Fagradalsfjall. Scientists found evidence of magma migration such as increased seismic activities and ground deformation in the area.
However, there is still no way of knowing whether this scenario (of an eruption at the surface) becomes true, and if yes, what the exact date and time for an eruption in the area will be. There is still the possibility that the current volcano-seismic activity will weaken and no eruption occurs. But Sigmundsson believes that if an eruption does occur, it will be similar to the 2010 Fimmvorduhals fissure eruption, producing lava fountains and voluminous lava flows, but not followed by an explosive stage as there is no nearby glacier or larger water body that might interact.

For the complete interview with geophysicist Freysteinn Sigmundsson, visit the RUV news page here.
More than 34,000 quakes in two weeks
Update Wed 10 Mar 2021 15:29
Earthquakes on the Reykjanes peninsula during the past 2 weeks (image: IMO)
Earthquakes on the Reykjanes peninsula during the past 2 weeks (image: IMO)
The Icelandic Met Office (IMO) announced earlier today, that the total number of earthquakes in the region has exceeded 34,000 since the onset of the seismic swarm about 2 weeks ago.
For comparison, it had about 3,400 quakes in the whole of 2020, which also had shown elevated activity, while the average during the previous years was in the range of 1,000-3,000 quakes per year.
Aviation warning and future possibilities
Update Wed 10 Mar 2021 06:08
Figure 1. Earthquake location map as of 10 Mar 2021. Recent earthquakes focused in areas between Fagradalsfjall and Keillir. (source: IMO)
Figure 1. Earthquake location map as of 10 Mar 2021. Recent earthquakes focused in areas between Fagradalsfjall and Keillir. (source: IMO)
Figure 2. Aviation color code map of Iceland. Green – volcano in non-eruptive state, Yellow – elevated unrest, volcanic activity decreased, Orange – heightened unrest, increased likelihood of eruption. (source: IMO)
Figure 2. Aviation color code map of Iceland. Green – volcano in non-eruptive state, Yellow – elevated unrest, volcanic activity decreased, Orange – heightened unrest, increased likelihood of eruption. (source: IMO)
As the number of earthquakes recorded in the Reykjanes Peninsula, Iceland, surpassed the 20,000 mark, the main area of unrest was identified as the area between Fagradalsfjall and Keillir. According to the Icelandic Meteorological Office (IMO), magma intrusions under the surface are the prime suspect to cause this ongoing seismic activity.
However, there are still uncertainties as to how these volcano-seismic events will develop. IMO listed the possibilities in their website here:
- The earthquake swarm might slow down in the following days and weeks, or the contrary may occur: it could increase in intensity and result in quakes of magnitudes of up to 6.0 in the area.
- If the latter occurs, an earthquake with a magnitude as high as 6.5 could hit the nearby volcanic system roughly 20 km east from the main area of unrest.
- If magma intrusion resumes, an effusive volcanic eruption could occur resulting in lava flows which will not threaten inhabited areas on the peninsula.
- The magma intrusion may also stop, in which case magma will solidify in place underground without an eruption at the surface.

In the meantime, IMO raised aviation warnings over the Krysuvik volcanic system in southwestern Iceland and the Grimsvotn volcano located in Vatnajokull National Park in southern Iceland. Orange volcano warning was raised over Krysuvik, and yellow warning over Grimsvotn. In June 2020, scientists reported high levels of sulfur dioxide coming from Grimsvotn. This is an indication of the presence of magma at shallow depth. IMO warned of a possible violent phreatic eruption, which could result from melting ice interacting with the hot magma.

For more information on the aviation color codes for Icelandic volcanic systems, visit the IMO website where they will post updates on this matter.
Volcano-tectonic unrest continues
Update Tue 09 Mar 2021 16:01
The area where Icelandic scientists believe is being affected by a magmatic intrusion that might or not lead up to an eruption in the near future (source: IMO / twitter)
The area where Icelandic scientists believe is being affected by a magmatic intrusion that might or not lead up to an eruption in the near future (source: IMO / twitter)
The Icelandic Met Office (IMO) reported that seismic activity near Fagradalsfjall at the southern end of the supposed ongoing magma intrusion increased from 5:20 this morning, but later decreased again.
The activity was very localized to the south of the intrusion and is probably an indication that the intrusion widened in this area.
Scientists from IMO believe that the most likely area for a new eruption is on a fissure somewhere in the area where magma currently is intruding, or accumulating underground and forming a magma chamber: this area is marked by the red line on the attached map published by IMO.
Earthquakes outside the supposed intrusion, in particular in the shaded areas on the map, are interpreted to be caused by stress release in response to the active intrusion, but not directly by magma movements in those areas.
Earthquakes continue, more than 2000 tremors within 24 hours
Update Mon 08 Mar 2021 07:30
Earthquakes on the Reykjanes peninsula during the past 24 hours
Earthquakes on the Reykjanes peninsula during the past 24 hours
The earthquake swarm on the Reykjanes Peninsula continues, but has decreased a little bit:
The Icelandic Met Office (IMO) reported that since midnight, about 500 earthquakes have been detected in the area - fewer than during recent nights - and that there were no signs of unrest.
The largest earthquake was 3.3 magnitude event at 00:34. The activity was greatest at Fagradalsfjall, but earthquakes were also measured at Reykjanestá, Þorbjörn and Trölladyngja.
Yesterday (7 Mar) about 2800 earthquakes were measured on the peninsula, of which about 300 were analyzed manually. The largest quake was a 5.0 magnitude at 02:01, which was felt everywhere in the SW corner of the country.
Source: IMO's Twitter feed
Webcams for the potential new eruption site
Update Sun 07 Mar 2021 08:51
There are at least two webcams pointing towards the potential eruption area (should it occur) near Keilir:
From Reykjavik: https://ruv.is/frett/2021/03/03/keilir-i-beinu-vefstreymi
From Keflavik: https://www.youtube.com/watch?v=XMh3B0ouTRI
Large magnitude 5 quake at 02:02 and new pulse of tremor
Update Sun 07 Mar 2021 08:48
The situation remains tense. A large magnitude 5.0 quake occurred last night at 02:02 about 3 km WSW of Fagradalsfjall. IMO reported that additionally, from midnight over 30 earthquakes over M3 and 5 larger than M4 have also been recorded.
Another pulse of tremor was recorded that lasted for 20 minutes. Its intensity was similar to the one measured on the e March, however that tremor had lasted several hours.

Volcanic eruption likely as quake swarms continue in southwestern Iceland

Update Sun 07 Mar 2021 08:36
Seismic tremor recorded on 3 Mar 2021 (image: IMO)
Seismic tremor recorded on 3 Mar 2021 (image: IMO)
Location of the most likely vent area in case of new fissure eruption (image: Gisli Olafsson @gislio / Twitter)
Location of the most likely vent area in case of new fissure eruption (image: Gisli Olafsson @gislio / Twitter)
Recent earthquakes in the Reykjanes peninsula (image: IMO)
Recent earthquakes in the Reykjanes peninsula (image: IMO)
For more than a week now, Iceland's Reykjanes Peninsula has been continuously rocked by an intense earthquake swarm: A total of more than 20,000 tremors have been recorded since the activity started on the Reykjanes Peninsula on 24 February 24 when a magnitude 5.7 quake occurred, followed almost immediately by a magnitude 5.0 event.
In total, the Icelandic Meteorological Office (IMO) recorded 5 quakes of magnitude 5.0 or above, 51 quakes between 4.0 and 5.0 and 397 quakes between 3.0 and 4.0. Many of these quakes were felt in nearby villages and towns, but luckily, the immediate areas around the earthquake swarm are not densely inhabited and there have been no reports of significant damage.

Could the earthquake activity herald a new volcanic eruption?
Since early on, it has been speculated whether the current seismic swarm was related to a magmatic event underground and eventually precede a new volcanic eruption.
The area is located on the active rift zone of SW Iceland, where the North American and Eurasian tectonic plates separate from each other, something that manifests itself in frequent earthquakes, underground magma intrusions and occasional fissure eruptions on the surface along SW-NE trending fissures.
This was given new evidence on 3 March, when IMO reported a sudden increase of seismic tremor in the same area, most likely sign that magma was moving underground. IMO stated that the observed burst of tremor were sourced from a region 2 km southwest of Keilir on the Reykjanes Peninsula, or a few km northeast of Fagradalsfjall, an old extinct subglacial volcano (also known as a “tuya”).
This region might be considered as part of the Krisuvik volcanic system in southwest Iceland, although it is still difficult to assign the potentially new vent area to the name of a specific volcanic system right now.

Eruptions occur on average every 800 years
According to professor of volcanology, Thorvaldur Thordarson, from the University of Iceland, volcanoes in southern Iceland experience “pulses” of activity every 800 years or so. He noted that the last eruption from this area occurred in the 11th or 13th century, so Iceland is right on time for an eruption.
However, citizens from the Reykjanes Peninsula need not worry as southwest Icelandic volcanic eruptions are very rarely explosive. “Icelandic eruption” is a specific type of effusive (not explosive) eruption where molten basaltic lava is erupted from parallel fissures in the ground, forming lava fountains and then vast lava flows.
This type of volcanic eruption is usually observed along spreading centers or mid oceanic ridges under the ocean. It was named after Iceland as this type of eruption was prominently observed occurring on-land in the country. Iceland sits on top of the Mid-Atlantic Ridge which is a spreading center where the North American and Eurasian tectonic plates are rifting apart.
In an article written by volcanologist Dave McGarvie from the Lancaster University, he noted that if there are to be any eruption in the area, it would likely not be as explosive as the 2010 Eyjafjallajökull eruption or the 2011 Grimsvötn eruption. This is due to the fact that the area is not covered by ice (which would otherwise interact explosively with the magma) and has shown fissure eruptions producing lava flows during the recorded historic past. Nevertheless, IMO has raised aviation warnings over the region.

Possible scenarios
It is still far from certain whether an eruption will occur or not in the near future. IMO lists the most likely possible scenarios:
- The ongoing seismicity reduces in the coming days and weeks.
- The seismic swarm will increase in intensity, possibly with an earthquake up to magnitude 6 in size nearby Fagradalsfjall.
- An earthquake up to magnitude 6.5 in size could be triggered in the Brennisteinsfjöll mountain range, over 20 km east of Fagradalsfjall.
- Magma intrusions continue in the vicinity of Fagradalsfjall.
- The intrusive magma movements stop and eventually solidify.
- An effusive volcanic eruption could occur, resulting in lava flows that should not threaten inhabited areas of the peninsula.

The evolution of the seismicity continues to be monitored day and night, and in the event of an eruption, various contingency plans are in place.

Source: Increased seismic tremor measured southwest of Keilir at Reykjanes Peninsula (IMO)

Krísuvík volcano (Southwestern Iceland): ongoing elevated seismic swarm; possibly upcoming eruption

Do, 4. Mär 2021, 08:36
08:36 AM | VON: MARTIN
Satellite image of ground deformation associated with N-S and E-W movement on the Reykjanes Peninsula (image: IMO)
Satellite image of ground deformation associated with N-S and E-W movement on the Reykjanes Peninsula (image: IMO)
Distribution of the earthquakes on the Reykjanes Peninsula on 25 Feb (image: IMO)
Distribution of the earthquakes on the Reykjanes Peninsula on 25 Feb (image: IMO)
The Icelandic Met Office (IMO) reported that seismicity on Reykjanes peninsula in the area between Krýsuvík, Kleifarvatn a Svartsengi volcanic system has been increasing during the past week.
The seismic activity started on 24 February accompanied by two moderate-to-strong volcano-tectonic earthquakes with magnitude M 5.0 and M 5.7 respectively and later that day another earthquake with magnitude M 4.8. Since the beginning of this unrest, 16 earthquakes above M 4 and 90 earthquakes above M 3 were detected by seismic network. The volcano-tectonic earthquakes were widely felt across SW part of the country including larger ones in the NW part as far as Ísafjörður.
A sharp peak in tremor was detected at 14:20 local time yesterday which has decreased and continued at reduced rate. The tremor was located 2 km southwest of Keilir on the Reykjanes peninsula.
There have been over 18,000 earthquakes at the time of this update since the seicmic activity started.
Significant ground deformation and location of the quakes in a N-S and E-W pattern suggests that a striking fault zone has been activated in this area. An InSAR interferogram showed left-lateral movement over a large section of the plate boundary.
The alert level for Krísuvík volcano was raised to "orange", as an increase of volcanic tremor has been recorded.
The ongoing elevated seismic swarm might be related with rock fracturing caused by a new batch of magma rising up to the surface. A new expected effusive eruption is likely upcoming in the next few hours.
Source: Icelandic Met Office volcano activity update 4 March 2021
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