Chapter 24 A review of volcanic hazard and risk-assessment praxis at the Soufrière Hills Volcano, Montserrat from 1997 to 2011

Volcanic hazard and risk at Soufrière Hills Volcano (SHV), Montserrat has been assessed in a consistent and quantitative manner for 14 years (1997–2011) during highly variable eruptive activity involving andesitic lava-dome growth, which has placed serious constraints on Montserratian society. This work has been carried out by the Scientific Advisory Committee (and predecessors) in collaboration with the Montserrat Volcano Observatory. We describe the organizational context of these assessments, the types of hazards and the methods used to analyse them. Knowledge elicitation using hazard scenarios and analysis by the Classical Model method were employed to formulate probabilistic forecasts of future hazardous events over the next year, and to quantify risks to individuals and Montserrat society generally. We devised a scheme for assessing the likelihood that the volcanic system had stopped receiving basalt magma, considered to be the main driver of the eruption. The accuracy of forecasts was tested using Brier Skill Scores: 83% of forecasts for events that were critical to life had positive skill, as measured by this method. We also discuss how government responded to our assessments. The continuous series of quantitative volcanic hazard and risk assessments described here is the only one of its kind.