New eruption at Fagradalsfjall Volcano follows days of seismic swarms

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After a weekend of intense earthquakes, a spectacular new eruption at Fagradalsfjall volcano in Iceland began Wednesday afternoon. Volcano scientists are keeping a close eye on this eruption, but only time will tell what will happen.
 

By Melissa Scruggs, Ph.D., @VolcanoDoc
 

Citation: Scruggs, Melissa A., 2022, New eruption at Fagradalsfjall Volcano follows days of seismic swarms, Temblor, http://doi.org/10.32858/temblor.264
 

Eruption at Fagradasfjall. Credit: Edward Marshall
Eruption at Fagradasfjall. Credit: Edward Marshall

 

After days of elevated earthquake activity on the Reykjanes Peninsula, Iceland’s Fagradalsfjall volcano began erupting at 1:18 p.m. Wednesday afternoon, local time. Roughly 5,000 earthquakes have been detected on the peninsula since July 30, according to the Icelandic Meteorological Office — including a magnitude-5.4 event felt in Reykjavik on July 31. These earthquakes accompanied ground deformation near the site of last year’s eruption, indicating magma movement toward the surface.

Currently, small lava fountains are erupting from a 300-meter-long (1,000-foot), northeast-southwest trending crack on the northern edge of the 2021 lava flow, according to researchers from the University of Iceland and Icelandic Meteorological Office who surveyed the new eruption. Lava is steadily erupting between five and ten times faster than the lava that erupted at the start of the 2021 eruption. Already, along the fissure, ridges of solidified lava have started to form.
 


 

Why is Iceland so volcanically active?

Iceland is home to 34 active volcanoes, averaging one eruption every four years. Volcanoes are so common in Iceland because of its unique tectonic setting; it is located above a mantle plume — a hot, buoyant bit of Earth’s mantle that rises upwards, bringing magma to the surface — and on top of the plate boundary where the North American and Eurasian plates incrementally inch apart. As the plates move away from each other, hot, less dense mantle rock rises upwards to fill the space in between the plates. High pressures deep in the Earth keep the mantle solid, but at the shallow depths underneath spreading ridges, lower pressures force hot mantle rocks to melt, generating basaltic magma. This process is called decompression melting. The new, buoyant magma ascends through the thin crust, often erupting at linear vents called fissures and creating new land.

Eruptions at Icelandic volcanoes are generally not explosive. Typically, flows of hot, runny basaltic lava pour out of fissures or fountain toward the sky in what’s called an effusive eruption. Although effusive eruptions are not as violent as their explosive counterparts, lava flows can still damage infrastructure, and large quantities of volcanic gases can affect air quality for nearby populations.
 

The 2021 fissure eruption of Fagradalsfjall produced spectacular lava flows, lava fountains and built-up spatter cones along a linear fissure for the first time in roughly six thousand years. A similar eruption is now underway. Credit: Courtesy A. Shevchenko and E. Zorn (GFZ Germany).
The 2021 fissure eruption of Fagradalsfjall produced spectacular lava flows, lava fountains and built-up spatter cones along a linear fissure for the first time in roughly six thousand years. A similar eruption is now underway. Credit: Courtesy A. Shevchenko and E. Zorn (GFZ Germany).

 

An unsurprising spectacle

This week’s eruption was not entirely unexpected by scientists monitoring the volcano, as heightened earthquake activity and uplift in the ground surface can indicate magma moving beneath a volcano. As magma travels toward the surface via underground conduits called dikes, the leading tip of the dike can cause the crust to fracture as it tunnels forward, triggering earthquakes.
 


 

Similar earthquakes and significant ground deformation occurred in the months before the 2021 eruption of Fagradalsfjall, as a nine kilometer (about five and a half miles) long, narrow body of magma intruded into the rift zone. The dike responsible for this new eruption is located only one kilometer (about half a mile) below the surface, says Magnús Tumi Guðmundsson, a geophysicist at the University of Iceland.
 

What can we expect next from Fagradalsfjall?

Though predicting exactly what a volcano will do in the future is not possible, scientists often use past eruptions to anticipate future eruptive behavior. With few exceptions, Icelandic volcanoes erupt effusively, producing spectacular basaltic lava fountains and flows, along with large quantities of dangerous volcanic gases. Scientists cannot predict exactly when an eruption will begin or end, but instead forecast what might happen, based on changes in volcanic activity.

In addition to monitoring earthquakes and volcanic gases, scientists are examining lava chemistry to get a better idea of how the magma is changing as the eruption progresses, says Frances Deegan, a volcanologist at the Swedish Research Council. This new batch of magma could have the same origins as the magma involved in last year’s eruption, says Deegan, but scientists will need to compare newly collected samples to the 2021 lavas to determine if there have been significant changes to the magma plumbing system in the past eight months.
 


 

The Icelandic Meteorologic Office expects no damage to infrastructure at the moment, and the Icelandic Civil Defense lowered its Public Safety Level to reflect the lower threat posed by the volcano. For now, the primary problem appears to be negative air quality, which the Icelandic Meteorological Office is monitoring.

Fagradalsfjall captured the attention of the world last year with its spectacular cones and lavafalls, lava fountains and flows. It seems that in 2022 it is poised to do the same.
 


 

References

Flis, A. (2022, August 1). A strong burst of nearly 4000 earthquakes occurs in Iceland, causing an increased risk of a new volcanic eruption as we head into August. Severe Weather Europe. https://www.severe-weather.eu/news/powerful-earthquake-swarm-volcano-iceland-seismic-activity-2022-fa/

Gudmundsson, A., Bazargan, M., Hobé, A., Selek, B., & Tryggvason, A. (2021) Dike-Segment Propagation, Arrest, and Eruption at Fagradalsfjall, Iceland. Presented at the AGU 2021 Fall Meeting, New Orleans, LA and virtual. https://doi.org/10.1002/essoar.10508827.3

Heimisson, E., & Segall, P. (2020) Physically consistent modeling of dike-induced deformation and seismicity: application to the 2014 Bardarbunga Dike, Iceland. Journal of Geophysical Research Solid Earth. https://doi.org/10.1029/2019JB018141

Jonsdottir, K., Cubuk Sabuncu, Y., Geirsson, H., Klaasen, S., Caudron, C., Lecocq, T., Barsotti, S., Barnie, T., Sigmundsson, F., Oddsson, B., Gudmundsson, M., Parks, M., Fichtner, A., Thrastarson, S., & Paitz, P. (2021) Seismic Monitoring of the 2021 Fagradalsfjall Eruption, SW Iceland. Presented at the AGU 2021 Fall Meeting, New Orleans, LA and virtual. https://ui.adsabs.harvard.edu/abs/2021AGUFM.V23B..05J/abstract
 

Further Reading

Larsen, G. & Guðmundsson, M.T. (2016 March 7). Katla. In: Oladottir, B., Larsen, G. & Guðmundsson, M. T. Catalogue of Icelandic Volcanoes. IMO, UI and CPD-NCIP. Retrieved from http://icelandicvolcanoes.is/?volcano=KRY
 

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