Eruption on Iceland's Reykjanes Peninsula 2021: activity updates

Fagradalsfjall volcano (Reykjanes Peninsula, Iceland): monthly eruption summary, activity seems to have slowed down

Sa, 24. Jul 2021, 05:25
05:25 AM | VON: MARTIN
The graph shows parameters of the lava flow discharge rate, lava area, lava volume, rock geochemistry and volcanic gases over the past month (image: IMO)
The graph shows parameters of the lava flow discharge rate, lava area, lava volume, rock geochemistry and volcanic gases over the past month (image: IMO)
The University of Iceland's Institute of Earth Sciences reported a summary of eruption parameters today documented since 26 June. Parameters showed lava area, lava volume, lava flow discharge rate, rock geochemistry, and volcanic gases. The graph below depicts an overview of the results.
The current eruption's site activity changed at the end of June as it began to fluctuate a lot in the frequency of lava flow discharge rate's periods. Following measurements depict a decreasing level of the lava flow.

Lava flow area
The lava flow area covered 3.96 square km.

Lava flow volume
Scientists estimate that approximately 96,1 million cubic meters of the lava have so far erupted from all vents. The lava flow has mostly accumulated in the Meradalir valley. No lava flows occurred in Geldingadalur, Nátthaga, and Syðri Meradalir valleys over the past two weeks.

Lava flow discharge rate
New measurements were made on 19 July by ISAVIA's machine TF-FMS to provide new parameters of the lava flow discharge rate and compared with previous data from 26 June.
The average lava flow discharge rate at the current eruption site during the period 26 Jun-19 Jul is about 7,5 cubic meters per second, which is almost half of the previous average rate (13 meters per second) and indicates a decreasing flow level.

Rock geochemistry
The graph shows the weight percent (wt.%) of magnesium oxide (MgO) (9,7%) and titanium oxide (TiO2) (9,9%) in the erupted magma.

Volcanic gases
Monthly average sulfur dioxide (SO2) emissions reached about 5000 tons per day and carbon dioxide (CO2) emissions reached approx. 9000 tons per day.

The effusive eruption of the volcano continues at reduced levels, which indicates that the pressure in the system is now decreasing. Is this a sign of weakening that leads the second half of the eruption likely to the beginning of the end?
Source: University of Iceland's Institute of Earth Sciences volcano activity update 23 July 2021

Lava overflows building shield around main vent, ash venting

Update Fri 02 Jul 2021 18:09
Lava overflow from the main vent last night (image: mbl.is webcam, screenshot via vulkane.net)
Lava overflow from the main vent last night (image: mbl.is webcam, screenshot via vulkane.net)
Latest lava flow field map as of 28 June 2021 (image: www.almannavarnir.is)
Latest lava flow field map as of 28 June 2021 (image: www.almannavarnir.is)
Ash venting this morning (image: mbl.is webcam, screenshot via vulkane.net)
Ash venting this morning (image: mbl.is webcam, screenshot via vulkane.net)
Although activity might seem to have been less vigorous during much of the past week compared to earlier stages, the eruption continues. Lava effusion rate has been at least stable if not following an overall slowly increasing trend, as last week's published data from the Icelandic Meteorological Office shows (see previous post).
After a few days with little visibility of the volcano, clouds cleared yesterday and showed that significant amounts of new lava had been erupted into the growing shield around the main vent, which in turn now seems smaller.
At about 9:30 p.m. yesterday, a prolonged lava overflow began as the lava level in the crater rose, producing small fountains, and large amounts of lava over-spilled onto the sides. Similar episodes are likely to have occurred during periods of bad weather as well.
Another lava flow made its way towards the Natthagi valley, which continues to be more and more filled as well. The flow stopped at around 2 a.m. Around 3:40, an ash cloud was seen rising from the vent, and tremor fell significantly at the same time. This lasted approx. 12 minutes and similar but smaller events with ash venting occurred several times later on.
What caused this change is not completely clear, but one likely scenario is that the magma column dropped temporarily and caused internal collapses in the emptied parts of conduits.

Fagradalsfjall volcano (Reykjanes Peninsula, Iceland): monthly eruption summary

Do, 1. Jul 2021, 04:29
04:29 AM | VON: MARTIN
The graph shows parameters of the lava flow discharge rate, lava area, lava volume, rock geochemistry and volcanic gases over the past month (image: IMO)
The graph shows parameters of the lava flow discharge rate, lava area, lava volume, rock geochemistry and volcanic gases over the past month (image: IMO)
On 26 June, the University of Iceland's Institute of Earth Sciences reported a summary of eruption parameters documented since May 10. The parameters showed lava flow discharge rate, lava area, lava volume, rock geochemistry and volcanic gases. The graph below depicts an overview of the results.

Lava flow discharge rate
The average lava flow discharge rate at the eruption site during the period 11-26 June is about 13 cubic meters per second, which indicates a stable flow level in comparison to the most other eruptions.

Lava flow area
The lava flow area covered 3.82 square km.

Lava flow volume
Scientists estimate that approximately 80 million cubic meters of the lava have so far erupted from all vents.

Rock geochemistry
The graph shows the weight percent (wt.%) of magnesium oxide (MgO) (10%) and titanium oxide (TiO2) (9,9%) in the erupted magma.

Volcanic gases
Monthly average sulfur dioxide (SO2) emissions reached 4200 tons per day and carbon dioxide (CO2) emissions reached 10000 tons per day.
Source: Icelandic Met Office volcano activity update 30 June 2021

The eruption in Fagradalsfjall is in many ways different from eruptions witnessed in recent decades. Most eruptions have originated in magma chambers under main volcanoes, where the pressure in the chamber and its size seem to largely determine the size and length of the eruption.

In Fagradalsfjall, this seems to be protected somewhat differently. It can be seen that the inflow vein and its properties have a great influence on the magma flow. The channel opened was relatively narrow and long (reaching a depth of ~ 17 km) and the carrying capacity was limited. An increase with time indicates that the channel has expanded somewhat over time, probably due to erosion in its walls. It can not be seen that the pressure in the source has decreased significantly and therefore the flow increased when the channel widened. There is currently no way to predict how long the eruption will last or whether lava flows will continue to increase.
Source: University of Iceland's Institute of Earth Sciences volcano activity update 30 June 2021

Lava flows and flows...

Update Wed 16 Jun 2021 16:27
Activity at Fagradalsfjall today (image: mbl webcam)
Activity at Fagradalsfjall today (image: mbl webcam)
The eruption goes on with no significant changes. Today, long-lasting periods occurred when lava flows were erupted from the main vent onto the immediate surrounding areas, creating beautiful surface flows and adding to the height of the central part of the growing lava shield.
Still, most lava finds itself going into a tube system that brings it to the margins of the active lava flow fields. In particular, the lava flow in Nátthagi valley continues to grow southwards, getting closer to the coast.

Aerial image of artificial dam and lava flows

The below image shows the dam built to prevent lava flowing into Nátthagakriki west of the Gelingadalur Valley (image: Styrmir Geir Jónsson / facebook)
The below image shows the dam built to prevent lava flowing into Nátthagakriki west of the Gelingadalur Valley (image: Styrmir Geir Jónsson / facebook)
The below image shows the dam built to prevent lava flowing into Nátthagakriki west of the Gelingadalur Valley on the evening of 14 June 2021. How long it lasts is probably a good matter of guessing...
Source: Styrmir Geir Jónsson / facebook

No signs of eruption ending soon, lava field increases by the hour

Update Tue 15 Jun 2021 18:19
Lava flows near the vent at Fagradalsfjall volcano in Iceland yesterday (image: mbl webcam)
Lava flows near the vent at Fagradalsfjall volcano in Iceland yesterday (image: mbl webcam)
Latest data from the eruption (image: IMO)
Latest data from the eruption (image: IMO)
Within less than a day, much of Nátthagi Valley was covered by new lava (image: mbl webcam)
Within less than a day, much of Nátthagi Valley was covered by new lava (image: mbl webcam)
The eruption continues to produce lava flows at constant pace, which gradually both enlarge and thicken the expanding lava flow field. Most of the lava arriving at the vent is going directly into lava tubes that bring it to the active flow margins and contribute to overall inflation of the flow field.
Another likely much smaller part, of varying proportion, is being erupted into near-vent surface flows that contribute to the slow formation of the elevated part of a lava shield. During much of yesterday, such surface flows could be seen being near-continuous from the vent, even forming small lava falls at topographic steps in the surface.

Much advance of the lava flow field occurred at the southern end of the Nátthagi Valley, mostly thanks to the new lava channel that had formed as overflow from Gelingadalur through a narrow valley a few days ago. The area covered by lava in Nátthagi has increased drastically, in a very short time.

The main concern is now to delay the lava from entering the Nátthagakriki area west of the eruption site, from where there are little natural obstacles for lava to reach the coastal road. A new 4-m tall earth wall is being build at the southwestern end of Gelingadalur in an attempt to at least delay this scenario (which, if the eruption continues, which is rather likely to assume, is only a matter of time).

Eruption is a scientific sensation
Newest scientific data show that the effusion rate is more or less constant, or gradually increasing, currently at around 12 cubic meters a second. The total area covered by lava flows is more than 3 square km and the total volume estimated 63 million cubic meters. Scientists are intrigued furthermore to observe a constant, gradual change in geochemical properties, which hint strongly towards that the magma currently erupted is coming directly from a deeper source in the mantle (as opposed to a shallower magma chamber). This in turn likely means that if nothing disturbs the now open pathways underground (such as a larger earthquake), the eruption has potential to indeed go on for a long time!
At any rate, the eruption already now is ranking as a scientific sensation and one of the most interesting and significant ones ever observed so far.
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