Assigning a Volcano Alert Level: Negotiating Uncertainty,Risk,and Complexity in Decision-Making Processes

A volcano alert level system (VALS) is used to communicate warning information from scientists to civil authorities managing volcanic hazards. This paper provides the first evaluation of how the decision-making process behind the assignation of an alert level, using forecasts of volcanic behaviour, operates in practice. Using interviews conducted from 2007 to 2009 at five USGS-managed (US Geological Survey) volcano observatories (Alaska, Cascades, Hawaii, Long Valley, and Yellowstone), two key findings are presented here. First, that observatory scientists encounter difficulties in interpreting scientific data, and in making decisions about what a volcano is doing, when dealing with complex volcanic processes. Second, the decision to move between alert levels is based upon a complex negotiation of perceived social and environmental risks. This research establishes that decision-making processes are problematic in the face of intrinsic uncertainties and risks, such that warning systems become complex and nonlinear. A consideration of different approaches to negotiating uncertainty and risk that are deliberative would, therefore, be beneficial in volcanic hazard management insofar as these suggest effective practices for decision-making processes in assigning an alert level.