Volcanic Hazard Communication at Pinatubo from 1991 to 2015

Abstract

When Pinatubo re-awakened in early 1991, very few people within the vicinity were familiar with volcanic hazards, and even fewer believed that Pinatubo could impact them. Scientists knew more, but were still struggling to answer: How often and how explosively did Pinatubo erupt, and when was its most recent eruption?What precursors could be expected in advance of a very large (VEI ≥ 6) explosive eruption?What was happening beneath Pinatubo that was driving 1991 unrest? To reach an exceptionally diverse audience and to counter widespread scepticism, scientists tried a whole package of communication measures, including simplified alert levels; a “worst case” hazard map; a probability tree; personalized briefings for local and national government officials, military and civil defense officials, nuns, and the news media; use of a IAVCEI video on volcanic hazards on broadcast TV and in briefings; volcanology tutorials for school teachers; talks on the mountain with villagers and anti-government guerrillas; and beer and hotdogs too. Forecasts were just-in-time and generally correct about what areas would be at risk. Overall, pre-eruption communication achieved its goal of getting people out of harm’s way. Three lessons stand out: use simple, multipronged communications, especially video; include worst case scenarios in your warnings, together with estimated probabilities thereof; and be willing, as scientists and decision makers, to recommend evacuations even if uncertainty is still high and there is still a chance of false alarm. For more than a decade after the 1991 eruption, rain-induced lahars threatened even more people and more infrastructure than the eruption itself. Several groups of scientists and engineers worked on the lahar threat, each coming up with slightly different long-term assessments that appeared to the public as bickering or incompetence. Scientists’ credibility was seriously diminished. Decisions of what lahar-mitigation projects to build—including a succession of inadequate ones—were influenced less by science and more by public pressure, pragmatism, back-room politics, and profit. Short-term or immediate lahar warnings were communicated by scientists and by police-manned watch points. The scientific warnings were technically superior but the police warnings had greater credibility, as they were from familiar sources and easily understood. Communication of hazard information at Pinatubo saved many lives, and we are proud and privileged to have been part of preventing a much worse disaster. However, margins of safety were narrow and some deaths that did occur could have been prevented by better communication.