International Workshop on the mechanism of Phreatic Eruption

Identifying and effectively communicating about volcanic unrest in
New Zealand
Sally Potter1, Gill Jolly1, Brad Scott1, Graham Leonard1, David Johnston2
1 GNS Science, Lower Hutt, New Zealand, 2 Massey University, Wellington, New ZealandE-mail: s.potter(at)gns.cri.nz

When a volcano enters a state of unrest, it is often the trigger for prompting actions andcommunications from volcanologists to decision-makers, including the public. However,
earthquakes, ground movement, and geochemical changes occur regularly at volcanoes,
even at some that have not erupted for a long time. At what point does this activity at thevolcano become recognised as ‘unrest’?
Potter et al. (2015a) developed the Volcanic Unrest Index (VUI) to help integrate many
monitoring parameters and combine them into one number. This index can be used to help
define when the volcano is changing state, to identify ‘unrest’. The VUI ranges from 0 (nounrest) to 4 (heightened unrest). Potter et al. (2015b) then investigated historical activity atTaupo Volcanic Centre, a caldera volcano in New Zealand, and determined thresholds using
the VUI framework to identify ‘unrest’. They found 16 episodes of volcanic unrest over 140years. The VUI can be used at any volcano in the world, even with relatively little information
about unrest, or monitoring data.
At the same time, New Zealand’s Volcanic Alert Level system was reviewed using social
science methodologies (Potter et al., 2014). This was to make sure that the system was
useful for the decision-makers’ needs, and to make it easier to effectively communicate thelevel of volcanic activity in New Zealand. In order to maintain clear roles and responsibilities
between science and decision-makers (including response agencies), the revised Volcanic
Alert Level system continues to be based on the level of volcanic phenomena, or hazard,
rather than on impact, or guidance information. The revised Volcanic Alert Level system(Figure 1) was implemented by GNS Science in 2014 with the Ministry of Civil Defence andEmergency Management for all of New Zealand’s active volcanoes. The Volcanic Alert Levelis supplemented by Volcanic Alert Bulletins, which contain further details about the volcanicactivity, monitoring efforts, and potential impacts. The Emergency Management sector
support the science-based messaging by providing guidance information for the public.

International Workshop on the mechanism of Phreatic Eruption

Fig. 1. New Zealand’s Volcanic Alert Level system (2014). Fromhttps://www.geonet.org.nz/about/volcano/val
GNS Science strives to provide information to the public and decision-makers in the mosteffective way possible, by using evidence from the field of behavioural science, andcontinuing improvements in quality of the monitoring information from GeoNet. Effective
warning messages can help to achieve an appropriate and timely response. Collaboration
between physical and social scientists, stakeholders (including emergency management,infrastructure providers, tourism operators, and land owners), indigenous peoples, andcommunities, ensure we understand information needs so we can produce effective anduseful information.
References
Potter SH, Scott BJ, Jolly GE, Neall VE, Johnston DM. 2015a. Introducing the Volcanic Unrest Index (VUI): A tool toquantify and communicate the intensity of volcanic unrest. Bulletin of Volcanology. 77:77.
Potter SH, Scott BJ, Jolly GE, Johnston DM, Neall VE. 2015. A catalogue of caldera unrest at Taupo Volcanic Centre,
New Zealand, using the Volcanic Unrest Index (VUI). Bulletin of Volcanology. 77:78.
Potter SH, Jolly GE, Neall VE, Johnston DM, Scott BJ. 2014. Communicating the status of volcanic activity: Revising
New Zealand's volcanic alert level system. Journal of Applied Volcanology. 3(13).