The eruption in Fagradalsfjall (2021, Iceland): how the operational monitoring and the volcanic hazard assessment contributed to its safe access

Abstract

After more than a year of unrest, a small effusive eruption commenced in Fagradalsfjall, Iceland, on 19 March 2021. The eruption lasted six months. The first six weeks were characterized by multiple fissure openings, and the remainder was dominated by effusive activity from a single crater. During the eruption, lava and low-level gases propagated over the complex terrain: a hyaloclastite massif with mountain peaks up to about 350 m asl with valleys in between. The area is uninhabited, but easily accessible at about 30 km distance from Reykjavík. While the eruption was ongoing, more than 356,000 tourists visited the eruptive site. To maintain low risk access to the area, it was critical to monitor the eruption (including opening of new fissures) in real-time, forecast the transport of gas and lava flow emplacement, and assess the evolving hazards. In addition to data accessibility and interpretation, managing this volcanic crisis was possible thanks to strong collaboration between the scientific institutions and civil protection agencies. The eruption presented an opportunity to tune, test and validate a variety of numerical models for hazard assessment as well as to refine and improve the delivery of information to the general public, communities living near the eruption site and decision makers. The monitoring team worked long hours during both the pre- and syn-eruptive phases for identifying low risk access areas to the eruption site and to provide a regular flow of information. This paper reviews the eruption and its associated hazards. It also provides an overview of the monitoring setup, the adopted numerical tools and communication materials disseminated to the general public regarding current exclusion zones, hazards and possible future eruptive scenarios.

Magmatic Controls on Volcanic Sulfur Emissions at the Iceland Hotspot

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Tremor clustering reveals precursors and evolution of the 2021 Geldingadalir eruption

“…However, they also can occur due to non-eruptive activities (Benoit and McNutt, 1996;Farrell et al, 2009;Moran et al, 2011;Shelly et al, 2015). Contrary to the reported intense seismicity prior to the Geldingadalir 2021 eruption, no precursory volcanic tremor has been reported before this study (Barsotti et al, 2023). Persistent seismic signals precede and/or accompany most volcanic eruptions (Konstantinou & Schlindwein, 2003); hence, volcanic tremors can be seen as a geophysical precursor to predict eruptions.…”

Relative Sea Level and Coastal Vertical Movements in Relation to Volcano-Tectonic Processes at Mayotte Island, Indian Ocean

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“…Recent volcano-seismic events in unexpected places or with significant unforeseen impacts challenge our understanding of volcanic activity. First, these events suggest that the role of volcanic activity on local natural hazards should be reconsidered [1][2][3][4][5], promoting specific studies on the reduction in risk [6] associated with volcanic activity [7][8][9][10][11][12]. Second, the potential interrelationship between short-term volcanic activity and long-term volcanotectonic evolution challenges our understanding of volcanic processes and the evolution of Earth's surface.…”