A month since the eruption began

The eruption has now lasted longer than all of the …

The eruption has now lasted longer than all of the eruptions in this series of eruptions at the Sundhnúkagígar crater row. It is the second longest eruption since the eruption in Mt Fagradalsfjall in 2021, which lasted 6 months. mbl.is/Hörður Kristleifsson

Today, one month has passed since the eruption that is currently taking place at Sundhnúkagígar crater row. The eruption, which began on the evening of March 16, is the fourth since magma accumulation began under Svartsengi at the end of October 2023.

The eruption has been the longest of all the eruptions on the Sundhnúkagígar crater row in this series of eruptions and the second-longest of the eruptions on the Reykjanes peninsula since 2021.

Short notice

It is recalled that the eruption’s notice was short, but a small earthquake swarm began around 19:30 on March 16, and its intensity increased by 19:40 and GPS-meters showed deformation-signs that indicated that a magma-run had started. The eruption started at 20.23 and the eruption fissure was nearly 3 km long and extended from Stóra-Skógafell to Mt Sundhnúkur.

“At the beginning of the eruption, lava flowed mostly to the south and southeast, along the defense walls toward the Suðurstrandarvegur road, and to the northwest toward Grindavíkurvegur road. About four hours after the eruption began, lava flowed across Grindavíkurvegur road, close to the north of Svartsengi. The speed of the lava tongue, which traveled to the south along the coastal barriers, as measured from the Icelandic Coast Guard’s surveillance flights, was about 1 km per hour,” an announcement from the Icelandic Met Office states.

Only the eruption in Mt Fagradalsfjall  has lasted longer

The current eruption was the longest of all the eruptions on the Sundhnúkagígar crater row in this series of eruptions and the second-longest of the eruptions on the Reykjaness peninsula since 2021.

“The first eruption in Mt Fagradalsfjall, which started in March 2021, was longer, but it lasted for about 6 months. The eruption in Merardalir in August 2022 lasted 18 days, and the eruption at Litli-Hrútur in July 2023 lasted 26 days. The previous three eruptions in the Sundhnúkagígar crater row series were short-lived.”

The eruption is stable

 The eruption now is stable but very slowly decreasing according to Benedikt Gunnar Ófeigsson specialist at the Icelandic Met Office. 

“The flow is slowly decreasing, but it is not possible to see it between days, because we have been looking for several weeks at a time. It is still not possible to predict the end of the eruption as it is, although we are getting closer.”

Some of the magma accumulating under Svartsengi

Ófeigsson says that the Sunday’s earthquake swarm supports the fact that the eruption has decreased. “At the same time, we see an increase in the inflation underneath Svartsengi, which is entirely consistent with the fact that the flow of the eruption is decreasing. Part of the magma coming from depth accumulates underneath Svartsengi, but the crater cannot handle the entire flow.”

The current eruption is more similar to the eruption in Fagradalsfjall than the eruption of the last few months, not least because of the length of the eruption. “It’s a bit more similar, however in Mt Fagradalsfjall we never had such a shallow magma chamber, but the magma came right up from the depth.” When asked what might cause that, he says it takes a much longer research period to answer that.

“There are some different conditions underneath Svartsengi that allow the crust to collect magma, which is comparable to, for example, the volcanis system in Askja. But these conditions are not present in Mt. Fagradalsfjall.”

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