Operational response and hazards assessment during the 2014–2015 volcanic crisis at Bárðarbunga volcano and associated eruption at Holuhraun, Iceland

Abstract

On August 16, 2014, an intense seismic swarm started below the eastern part of Bárðarbunga caldera in the north-western part of Vatnajökull ice cap, Iceland, marking the onset of a major rifting event. The intense seismicity, corroborated by a complicated deformation pattern, migrated away from the Bárðarbunga caldera for >45 km, until a small effusive eruption started in Holuhraun, outside of the ice cap, on August 29 which lasted a few hours. On August 31 a second, more intense, eruption started. It lasted 180 days and is the largest effusive eruption in Iceland since the Laki event in 1783–1784. A lava field covered about 84 km2 in the middle of the highlands with a bulk volume of ~1.44 km3. Although the potential danger of ice melting and subsequent flooding coupled with tephra fallout was the main concern at the beginning of the crisis, the main associated hazard turned out to be an abundant and constant release of volcanic gases that polluted the country threatening human health and the environment for several months. Very little (or almost no) ash was produced. The impact of the Holuhraun eruption outside of Iceland was minor if compared with what happened in 2010 when Eyjafjallajökull erupted. However, on three occasions the dense gas cloud released by the fissure eruption reached some European countries where unusually high SO2 concentrations were measured at ground level. Managing and living with such a prolonged effusive event was a major effort for the Icelandic scientific community and civil protection authorities and it significantly affected the local population in the northern and eastern parts of the country.This paper retraces the main events that accompanied the volcanic crisis at Bárðarbunga and focuses on the scientific and operative response provided throughout its duration. Particular attention is given to the direct links between the observed phenomena, monitoring effort, hazard assessment and concrete actions taken by the authorities in charge of risk and mitigation assessment. The different roles of the involved institutions are clarified, and the wide and collaborative response on a national basis is explained.A major finding of this post-event analysis is that a strong internal collaboration between the scientific community and operative institutions is the basic element for proper crisis management. Iceland has established protocols that, while imperfect, ensured a well-coordinated response to the Holuhraun eruption and the preceding unrest, and will continue to provide a prompt and effective response for future events. Important realizations, including the need for a proper ground-based alert level system, have been raised and they will be a matter for further development.