Advancing long-term lava hazard assessment of the Reykjanes Peninsula, SV Iceland

With the onset of the Fagradalsfjall 2021 eruption, Reykjanes Peninsula entered a new eruptive period after 781 years break. Such periods last decades and can activate multiple volcanic systems on the Peninsula, including some that intersect the capital area. Eruptions from these volcanic systems have the potential to affect up to 75% of the Icelandic population (~ 285,000) either by compromising essential infrastructure and/or inundate inhabited areas.  Between 2021-2025, twelve eruptions have occurred.

Therefore, the long-term lava hazard assessment began in 2024, which is a part of the volcanic hazard and risk assessment for the Reykjanes Peninsula, led by the Icelandic Meteorological Office on behalf of the Icelandic government. It is the first lava hazard assessment comprising the entire Peninsula reaching east to the South Iceland Seismic Zone at the Ölfusá river, comprising six overlapping volcanic systems.

The long-term lava hazard assessment is divided into three parts. Firstly, an assessment of spatial distribution of vent opening probability based on geological mapping of eruptive fissures (subglacial and subaerial), faults, geothermal areas and the plate boundary axis using MatHaz (Bertin et al., 2019). Secondly, lava flow simulations for four different eruption scenarios were performed on a 5m/pixel digital elevation model using the probabilistic code MrLavaLoba (de’Michieli Vitturi and Tarquini, 2018) covering a 200 square metre grid in areas with a vent opening likelihood > 0. In total nearly 200,000 simulations were executed on the supercomputing facilities of the Icelandic Research e-Infrastructure (IREI). This national high-performance computing (HPC) system were critical to achieving the resolution and duration required for the study. After post-processing, the likelihood of lava inundation can be assessed for the entire peninsula for each of the four eruption scenarios. Finally, the combined results of the likelihood of vent opening and lava inundation are assessed with respect to inhabited areas and essential infrastructure: water supply, power supply, and roads. The results are intended for urban planning and serve as a knowledge base for emergency response plans. They will be published in reports, a web-map and data repository.

Here we present key findings and discuss challenges in this long-term lava hazard including i) complex study area with multiple volcanic systems and with sparse geological information, ii) performing multiple eruption scenarios and iii) additional considerations needed when providing both static and online/dynamic maps.