Potentially damaging volcano-related processes and products that occur during or following eruptions. In quantitative hazards assessments, the probability of a given area being affected by potentially destructive phenomena within a given period of time. At the start of the 21st century, more than half a billion of the world's population are at risk from volcano hazards. For general discussions of volcano hazards and their monitoring and mitigation, see Scarpa and Tilling (1996) and Tilling (1989, 2002)