Eruption on Iceland's Reykjanes Peninsula 2021: activity updates

Magma likely won't reach surface as models indicate

GPS instruments continue to detect a mild ground deformation, although the seismic activity at Reykjanes Peninsula continues at decreasing levels.
Numerical models indicate that a current flux of magma is less than half of the pre-eruptive magma volume that started in March.
It is unclear whether the magma batch will reach the surface as happened in March.
The most likely scenario, according to models and the latest measurements, is that the magma may start to solidify in dikes sooner than reach the ground.
"Scientists have pointed out a comparison between the activity at Fagradalsfjall and the activity seen in the Krafla fires", says Michelle Parks, an expert at the Icelandic Meteorological Office. "In the Krafla fires, about half of the magma intrusions ended with an eruption and the other did not and we could see examples of such activity at Fagradalsfjall. It affects how big the magma intrusions are and how shallow they reach", says Michelle.
Source: Icelandic Meteorological Office volcano activity update 7 January 2022

Seismicity continues at reduced levels

The seismic activity at Reykjanes Peninsula continues at decreasing levels.
About 200 earthquakes have been detected since midnight and have reduced both in numbers and frequency.
Source: Icelandic Meteorological Office volcano activity update 3 January 2022

Activity slowed down as seismic swarm decreased

The seismic activity continues with little changes as a number of earthquakes have been lower than in previous days.
1300 earthquakes have been detected on 28 December which is a lot less in compared with the previous day when 2300 quakes were detected.
A maximum magnitude of 3.7 occurred at 10:22 local time yesterday located east of Kleifarvatn ans was widely felt in the capital area.
GPS and InSAR measurements confirm that the flux of magma is limited to a dike intrusion which is very similar to the pre-eruptive pattern before the eruption started on 19 March.
Source: Icelandic Meteorological Office volcano activity update 30 December 2021

More and more frequent earthquakes reflect magma intrusion

600 quakes have been detected since midnight, but have occurred at a lower number than yesterday at the same time.
A maximum magnitude of 3.6 occurred yesterday at 08:25 local time.
Magma migration at depth is still about to pressurize and the increase in the seismic activity is likely a sign of its accumulation.
19000 earthquakes have already been detected in total, mostly with magnitudes of 4 or more since the seismic crisis started on 21 December.

Strong seismic activity continues

The number of earthquakes rapidly increasing but the activity slowed down a bit over the past 24 hours.
18000 earthquakes have already been detected in total, mostly with magnitudes of 4 or more since the seismic crisis started on 21 December.
Strongest earthquakes occurred outside of a potentially eruption site yesterday.
People are advised to avoid the area due to risk of rockfalls.

Continuing ground deformation has reached same pre-eruptive February values

The seismicity continues at increasing levels.
Earthquakes have continues to pick up both in numbers and strength.
4 quakes on 24 December were recorded, of which 3 with magnitudes of 4 and 1 with a maximum magnitude of 4.8. 3000 earthquakes have been detected in total since the seismic crisis started on 21 December.
The activity has been intensifying and more frequent under the Fagradalsfjall volcano, but it also occurred near Grindavík and Kleifarvatn.
The latest interferogram measurements (InSAR) detected same pre-eruptive ground deformation (see attached image) as seen in late February reflecting continued magma intrusion and migration under the surface, supported also by continued deformation of the surface.
Source: Icelandic Meteorological Office volcano activity update 26 December 2021

Intense seismic activity continues

The elevated seismic activity continues.
2000 earthquakes have been detected in total over the last 17 hours at 5-8 km depth suggesting that the flux of magma rising within the volcano is significant and most likely scenario of an imminent eruption is considered to occur in Geldingadalir eruption site.
GPS instruments detected a rapid ground deformation, another tell-tale sign of an impending eruption, which is similar to the pre-eruption measurements before 19 March.
Source: Icelandic Meteorological Office volcano activity update 23 December 2021

Seismic activity has been picking up since yesterday, Aviation Color Code raised to orange

The Icelandic Meteorological Office (IMO) detected an increasing trend of seismic activity began yesterday.
18 quakes at regular intervals of 1 to 10 per minute have been recorded located 2-4 km northeast of Geldingadalir followed by a significant rise of seismic energy at about 00:30 local time.
26 quakes during the past 24 hours were recorded with magnitudes of 3 or more.
1400 earthquakes have been detected in total over the last 24 hours, of which the largest quake with a maximum magnitude of 4.9 occurred at 09:23 local time and was widely felt on the SW corner.
Earthquakes and the increase in seismic activity reflect magma intrusions at shallow level and likely push its way into same dikes as it used to erupt before.
As mentioned in the latest report, the expansion continues to be measured meaning that magma is probably accumulating under the surface and it's difficult to predict what will happen next.
Based on the increased seismic activity, the IMO has changed the Aviation Color Code to "orange".

Volcano remains quiet even three months since eruption ceased

It has been three months yesterday since the last lava flow was seen at the eruption site. The eruption that began on 19 March, lasted exactly 6 months.
"Of course, it is always a matter of saying exactly when a particular eruption is over, because volcanic activity can be very cyclical", says Sara Barsotti, director of volcanic eruptions at the Icelandic Meteorological Office. "We have been pointing out ever since the earthquakes in Geldingadalur began that the Reykjanes peninsula is active in terms of earthquakes and volcanic activity, and history tells us that volcanic activity there occurs in cycles", says Sara.
Expansion continues to be measured meaning that magma is probably accumulating under the surface and it's difficult to predict what will happen next.

Eruption site is currently calm for now, slight inflation detected

The effusive eruption at the volcano has already ended or has remained mostly calm since 18 September as lava flows have stopped.
During the eruption, instruments continued to detect a deflation over the eruption site as magma used to leave from the deep chamber and pushed its way up to the surface.
However, GNSS and InSAR instruments observed a new inflation on the Reykjanes peninsula since the end of September. This is likely reflecting a renewed magma intrusion and migration under the surface, supported also by continued deformation of the surface.
A swarm of small earthquakes occurred in late September, located in the south of Keilir area, that may be related to a new batch of magma rising inside the volcano's conduits, although no new ground deformation has been detected during this time period.
The current inflation may not be associated with a new impending eruption.
This may take years or decades what will happens next at Reykjanes peninsula.
Source: Icelandic Meteorological Office volcano activity update 19 November 2021

Activity oscillates like heartbeat from almost absence to spectacular lava overflows

The eruption continues with no signs of ending, even though it has been going through rhythmically alternating phases of very low to very high levels. Roughly every 24 hours, it changes from one to the other extreme.
When it is high, the crater is filled with a lava lake that overflows on its rims and produces spectacular flows, as can be seen in the recent video below or in the view of the webcam right now (attached); when it is low, there is usually no visible activity at the surface.
Video:

Volcanologist Þorvaldur Þórðarson explained that these lava pulses are likely caused by large gas bubbles rising through the magma in the underground feeding system, pushing the magma out of the vent onto the surface.
Since these lava surges come at very regular intervals, these large gas bubbles must rise in very orderly pattern. Nature likes such regular processes and creates order,- think of the rhythmic behavior of geysers, for example.
The gas bubbles that are responsible for the peaks of activity at Fagradalsfjall are of course orders of magnitude larger than most similar phenomena. Likely, they originate at the top of the magma source in the upper mantle at 15-17 km depth, and once large enough to overcome a critical threshold of some sorts, they start rising and pushing the magma column upwards, resulting in the surface activity seen a short time after.