Volcanic hazards associated with explosive basaltic eruptions in Iceland: A case study of the Veiðivötn 1477 CE Eruption in Central Iceland.

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Recent historical eruptions such as Eyjafjallajökull 2010, La Palma 2018, and even the Hunga Tunga Hunga Ha'apai events in 2022 have highlighted the far-reaching impacts of volcanic plumes, including disruptions to air travel, infrastructure damage, and potential health consequences. These events were highly documented with direct observations and near real-time measurements, allowing scientists and local authorities to act rapidly. Highly active volcanoes are being monitored, such as Etna, Stromboli, Hekla, Piton de la Fournaise and Kilauea, and their eruptive history is well-constrained, allowing stakeholders to draw hazard maps and build action plans. However, some volcanoes with lower eruptive frequency, i.e., 500-800 years, such as the Veiðivötn fissure swarm in Iceland, have received less attention, and their potential volcanic hazards remain poorly constrained. The Veiðivötn 1477CE fissure eruption took place in the Southern highlands of Iceland. Tephra from this event covered an inland area of 53,000 km^2. Deposits from the eruption are still two centimetres thick at distances larger than 200 km from the source and reached as far as Scandinavia and Greenland, illustrating the long-range tephra dispersal and the potential for widespread disruption to communities, infrastructure, and economic activities.In this study, we intend to decipher the volcanic hazards associated with the Veiðivötn eruption and its potential relevance as an analogue for a future explosive basaltic eruption in Iceland. We combine our field data on mapping, deposit thickness, tephra and bulk density, and total grain-size distribution to a one-dimensional physical model of a volcanic plume to estimate the Mass Eruption Rate (MER) and maximum column height.Field data allows us to constrain two dispersal axes associated with different eruption phases. The main 1477 CE eruption dispersal axis was to the northeast, which significantly impacted the Icelandic population then. However, a similar eruption today with dominant winds directed to the north, south, or southwest would strongly impact the towns of Akureyri, Vík, and Reykjavík with tephra accumulations of up to 5 cm, 20 cm, and 10 cm, respectively. We also identified traces of buried vegetation beneath the deposit column in the highlands. The proximal area associated with this event is a sandy desert covered in tephra from the eruption. Suggesting that the Veiðivötn 1477CE eruption devastated the local environment, leaving the landscape bare and inhospitable since.The comparison between our field data on this outstanding eruption and our physical model shows that the MER needed for a stable plume ranges from 10^7 to 10^8 kg/s, with a maximum column height between 15 and 25 km for volatile contents of 1-2 wt%. The results also emphasize the role of the wind on the sustainability and maximum height reached by the plume.These findings highlight the use of one-dimensional models in refining predictions of eruption dynamics and enable us to evaluate the associated hazards if such an eruption were to occur today.

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