International Workshop on the mechanism of Phreatic Eruption

Living in harmony with New Zealands volcanoes: Balancing tourism,
social values, land use, and hazards around caldera and cone volcanoes
Graham Leonard1, Sally Potter1, David Johnston2, Wendy Saunders1
1 GNS Science, 1 Fairway Drive, Lower Hutt 5010, New Zealand
2 Joint Centre for Disaster Research – Massey University – GNS Science, Wellington, New ZealandE-mail: g.leonard(at)gns.cri.nz

Tourism, both domestic and international, is a substantial part of New Zealand’s economy,
with a strong link to volcanoes. Volcanoes are also widely valued in terms of landscape,access and resources by New Zealanders. Risk management in New Zealand is underpinned
by New Zealand’s signatory to the post-Sendai 2015 framework for improved community
resilience to all natural hazards.
The most challenging hazards around both calderas and cone volcanoes lie at the two endsof the eruption size spectrum. The smallest eruptions, which are often phreatic or phreatomagmatic can occur with little or no warning due to a sudden perturbation in the hydrothermalsystem. Because these hydrothermal areas are also accessed daily by abundant tourists(Tongariro, Ruapehu, central Taupo Volcanic Zone (cTVZ) calderas, and White Island) evenin small eruptions the consequences can be severe. Figure 1 shows the large number ofhydrothermal systems across cTVZ and White Island.
At the other end of the spectrum when possible magmatic unrest is detected throughmonitoring at these volcanoes, the challenge is in interpreting the signals to provide eruption
forecasts, and in interpreting and communicating uncertainty. This applies also at lessrecently active volcanoes including Auckland, Taranaki and other parts of cTVZ, Cooperation
between scientists, emergency managers and communities is complex because response
actions such as evacuation can require substantial lead times. This means decisions need
to be planned and executed while there is potentially high uncertainty as to whether or how
big an eruption may occur.
Research into our most recent large eruption, at Ruapehu 1995-96 shows two paths totourism impacts. The single largest economic cost was from disruption of flights, however thelargest local disruption was the loss 1/3 to 2/3 of eruptive period tourism revenue acrossthose two years.
Living in harmony with New Zealands volcanoes means balancing a desire and need foraccess to places at risk across this eruption size spectrum. Risk elimination would only bepossible through abandonment of large parts of the North Island, and all of New Zealand (likeInternational Workshop on the mechanism of Phreatic Eruption

Fig. 1 Distribution of hotsprings across the central Taupo Volcanic Zone (overlain on
resistivity data which correlates to geothermal systems). From Leonard et al. 2010.
Japan) has competing risks from earthquakes, tsunami, severe weather, landslides etc. As aresult there is a strong focus on risk management – through risk calculation, discussion ofwhat risk is acceptable or tolerable for different land uses or activities, and risk reduction
strategies. These include education, physical safety measures, closures and evacuation in
response to forecasts or eruptions (Leonard and Potter, 2015). Currently land use planning
is an underutilized approach for mitigating volcanic risk, but applications are limited because
cone volcanoes are already mostly isolated within national parks, and the potential ventlocations in cTVZ and Auckland are widely distributed.
Main References
Leonard, G.S., Begg, J.G., Wilson, C.J.N. and Leonard, G.S., 2010. Geology of the Rotorua
area. GNS Science.
Leonard, G. and Potter, S., 2015. Developing effective communication tools for volcanic
hazards in New Zealand, using social science. Global volcanic hazards and risk.
Cambridge University Press, Cambridge, UK, pp.305-310.