Fagradalsfjall volcano update: Eruption with hickups - what the changes from calm to lava fountains might mean

Mon, 3 May 2021, 10:29
10:29 AM | BY: T
Phase of strong lava fountain yesterday around noon (image: RUV webcam)
Phase of strong lava fountain yesterday around noon (image: RUV webcam)
The eruptive activity remains overall similar as during yesterday, with alternating phases of lava fountaining and only more or less quiet lava effusion. It seems that most activity by now is concentrated at the vent #5 in the central part of the fissure system, which had began erupting on 13 April.
In the past 12 hours, the lava fountains from the cone did not reach the same intensity as during yesterday morning, and intervals between these seem to have increased, but this could change quickly.
More interestingly, what exactly caused the observed change in eruptive behavior, from being extremely stable over many weeks with constant stead lava effusion and mild spattering at several vents, to now pulsating, switching from quiet effusion at low rate to strong lava fountaining from a single vent? What could this observed instability mean for the near future of the eruption?

That question is difficult to answer. The immediate cause of the intermittent strong lava fountaining phases is that gasses contained in the magma have now been released in batches as opposed to a steady flow at constant rate, which had been the case before.
Only what exactly causes this change to a rhythmic pattern is more difficult to know: one model might be it is caused by newly developed blockages in the (upper) plumbing system, or "bottlenecks", and / or, likely in combination with the arrival of more gas-rich magma, according to volcanologist Ármann Höskuldsson, cited in an article on Icelandic National Broadcasting Service's website (RUV):
"We're trying to understand the sore throat it appears to have got. I guess not only is there more gas in there, but there are also either bottlenecks or blockages down there and probably more water in the magma."

According to Þorvaldur Þórðarson, professor of volcanology, the eruption has entered a phase of being more volatile, and despite the apparent calmer phases in between the more active ones, it is not clear whether this suggests it is in decline or increase:
"But what is happening is that the gas that is being released from the magma, it is not flowing out of the magma as it has done so far, but it seems to come with certain pulses into the system and then tear itself up. There is something that is delaying the gas release for a certain period of time, until pressure builds up and the gas-rich magma manages to erupt to the surface in form of large jets"

Source / Link: Gígurinn þeytir kviku 300 metra upp í loft (RUV)

Previous news

Mon, 3 May 2021, 08:18
Lava fountains, about 300 m tall, pulsated at regular intervals of 7 to 10 minutes (image: @gislio/twitter)
A spectacular footage of tonight's lava fountains visible from Iceland's capital - Reykjavík can be seen in the attached video below. Read all
Mon, 3 May 2021, 07:54
Lava fountains, about 300 m tall, pulsated at regular intervals of 7 to 10 minutes (image: @gislio/twitter)
The effusive eruption of the volcano continues from all fissure vents. The activity continued at stable levels over the past days until it began to fluctuate yesterday. ... Read all
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