Responding to eruptive transitions during the 2020–2021 eruption of La Soufrière volcano, St. Vincent

Abstract

A critical challenge during volcanic emergencies is responding to rapid changes in eruptive behaviour. Actionable advice, essential in times of rising uncertainty, demands the rapid synthesis and communication of multiple datasets with prognoses. The 2020–2021 eruption of La Soufrière volcano exemplifies these challenges: a series of explosions from 9–22 April 2021 was preceded by three months of effusive activity, which commenced with a remarkably low level of detected unrest. Here we show how the development of an evolving conceptual model, and the expression of uncertainties via both elicitation and scenarios associated with this model, were key to anticipating this transition. This not only required input from multiple monitoring datasets but contextualisation via state-of-the-art hazard assessments, and evidence-based knowledge of critical decision-making timescales and community needs. In addition, we share strategies employed as a consequence of constraints on recognising and responding to eruptive transitions in a resource-constrained setting, which may guide similarly challenged volcano observatories worldwide.

Challenges and Opportunities for Risk Management of Volcanic Hazards in Small-Island Developing States

“…Volcanic risk management planning and awareness activities are the primary volcanic hazard mitigation strategies implemented by UWI-SRC for the Caribbean. These activities include the preparation of volcanic hazard maps for the Antilles region (eg Figure 1) and the volcanic hazard atlas of comprehensive geological and volcanological data for each volcanic island (Lindsay et al 2005), as well as the development of volcanic alert-level systems for each island (Joseph et al 2022).…”

“…This dome growth was preceded by a short period of low-level volcanic seismicity at the volcano from November 2020. SMU uses an alert system that consists of 4 levels, with green indicating normal background volcanic activity with no or minimal risk and red indicating eruptive activity with high or impending risk that may potentially have negative impacts on communities, agriculture, and structures near the volcano (Joseph et al 2022).…”

“…This newly formed dome underwent a significant increase in growth rate, with increased venting and visible incandescence observed 6-8 April 2021 (Joseph et al 2022). UWI-SRC issued a warning on 8 April based on heightened seismicity and visual observations that were indicative of an imminent explosive eruption.…”

“…The eruption transitioned to an explosive phase on 9 April 2021, with multiple Vulcanian and Sub-Plinian explosions occurring. The explosive eruptions consisted of 32 discrete events that generated plumes of 15 km or more above the volcano (Joseph et al 2022), which deposited ash over the entire island of St Vincent and extended to the neighboring islands, particularly Barbados.…”

“…Furthermore, contributions from both the donor agencies who responded to the monitoring needs and the authorities who facilitated the evacuation and recovery preparations were significant. UWI-SRC created subgroups based on the necessary volcanic disciplines and identified team leads to coordinate the international scientific support response (Joseph et al 2022). This approach greatly improved access to available data and resources in a timely manner.…”