Fig. 6

Generic format of event tree for use in eruptive volcanoes (H. Wright, unpublished example), similar to those used at Agung and Sinabung Volcanoes (Indonesia) as presented by Syahbana et al. (2019) and Wright et al. (2019). In this case the eruption was already underway, hence a probability of 100% was assigned for occurrence of eruption. By constructing such trees and assigning probabilities to each node (perhaps through an expert elicitation), the observatory can help frame eruption scenarios, collate current monitoring information, and document outstanding questions and unknowns. Note that event trees such as this can be extended to columns that aim to incorporate information on vulnerability and risk