around dormant volcanoes, where volcanic risk perception is usually low.

Video footage is an effective tool for raising PDC hazard knowledge. During the 1991 eruption of Mount Pinatubo (Philippines), the dissemination of a film from the French volcanologists M. and K. Kraft likely saved many thousands of lives. Recently, the World Organization of Volcano Observatories (WOVO) provides video resources through VOLFilm, a Multilingual and multi-platform films database for resilience to risks from volcanic hazards (http://www.wovo.org/volfilm-multilingual-and-multi-platform-films-for-resilience-to-risks-from-volcanic-hazards.html). Dissemination of information also comprises continuous media slots on PDC risk prevention, preparedness and management taking into account geographical specificities.

Community Based Disaster Risk Reduction (CBDRR) should be considered in integrating top-down and bottom-up approaches and as a channel of information and actions between stakeholders. Indeed it fosters the participation of threatened communities in both the evaluation of risk (including PDC hazards, vulnerability and capacities) and in the ways to reduce it. Community participation and involvement in raising PDC hazard awareness might be accomplished through various ways: socioeconomic factors should be better integrated from daily life to strengthen livelihoods; collaboration should be based on actual collaboration between institutional and upper level stakeholders, local stakeholders, and communities. Several approaches may be taken in order to gain more traditional knowledge of and responses to PDC-related disasters, in the framework of a bottom-up disaster risk reduction programme. Dialogue between the communities and people giving the warnings could be improved through participatory methods, e.g. participatory volcanic hazard mapping, community evacuation simulations, rural appraisal, focused group discussion or participatory three dimension mapping.

Efficient communication between scientific experts on PDC hazard, authorities, the media,

local NGOs, and the population should be enhanced to improve crisis management. Information should be provided to people on time and using simple and clear language, preferably traditional language.

The need for community participation and involvement in raising PDC hazard awareness is crucial, especially among specific stakeholders, e.g. recent immigrants or daily workers coming from outside the PDC hazard zones or women, who usually have a poorer knowledge of hazards than their husband or children. Local and cultural factors should also be considered in risk and crisis management, especially because PDC hazard is often related to local myths. The 2010 Merapi disaster suggests that religion is an essential element of culture and must be carefully considered in the planning process, and not simply dismissed as a symptom of ignorance or superstition. Participatory risk management involving community leaders and their populations is most appropriate to bridge tradition, local realities and the implementation of risk management policies and strategies.

To conclude, CBDRM eventually empowers communities with self-developed and culturally acceptable ways of coping with crises due to PDC hazard.

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# The Communication and Risk Management of Volcanic Ballistic Hazards

R.H. Fitzgerald, B.M. Kennedy, T.M. Wilson, G.S. Leonard, K. Tsunematsu and H. Keys

**Abstract**

Tourists, hikers, mountaineers, locals and volcanologists frequently visit and reside on and around active volcanoes, where ballistic projectiles are a lethal hazard. The projectiles of lava or solid rock, ranging from a few centimetres to several metres in diameter, are erupted with high kinetic, and sometimes thermal, energy. Impacts from projectiles are amongst the most frequent causes of fatal volcanic incidents and the cause of hundreds of thousands of dollars of damage to buildings, infrastructure and property worldwide. Despite this, the assessment of risk and communication of ballistic hazard has received surprisingly little study. Here, we review the research to date on ballistic distributions, impacts, hazard and risk assessments and maps, and methods of communicating and managing ballistic risk including how these change with a changing risk environment. The review suggests future improvements to the communication and management of ballistic hazard.

**Keywords**

Volcanic ballistics • Volcanic hazard • Volcanic risk • Risk communication • Risk management

<footnote>R.H. Fitzgerald (✉) · B.M. Kennedy · T.M. Wilson
Department of Geological Sciences, University of
Canterbury, Private Bag 4800, Christchurch 8140,
New Zealand
e-mail: rebecca.fitzgerald@pg.canterbury.ac.nz</footnote>

<footnote>G.S. Leonard
GNS Science, PO Box 30368, Lower Hutt 5040,
New Zealand</footnote>

<footnote>K. Tsunematsu
Mt. Fuji Research Institute (MFRI), 5597-1
Kenmarubi Kamiyoshida Fujiyoshida-Shi,
Yamanashi 403-0005, Japan</footnote>

<footnote>H. Keys
Department of Conservation, PO Box 528, Taupo
3351, New Zealand</footnote>
# 1 Introduction

Ballistic projectiles are one potentially lethal and damaging hazard produced in volcanic eruptions. Ballistics are fragments of lava (bombs) or rock (blocks) ejected in explosive eruptions (Fig. 1a, b). Projectiles range from a few centimetres to tens of metres in diameter and separate from the eruptive column to follow nearly parabolic trajectories (Wilson 1972; Fagents and Wilson 1993; Bower and Woods 1996). Their exit velocities can reach hundreds of metres per second and land up to ~10 km from the vent, although typically within five kilometres (Blong 1984; Alatorre-Ibargüengoitia et al. 2012). Ballistics are associated with all forms of explosive eruptions but are considered major hazards of hydrothermal, phreatic, phreatomagmatic, Strombolian and Vulcanian eruptions, especially those which have little to no precursor signals of volcanic unrest. Managing ballistic hazard and risk on active volcanoes, particularly those permanently occupied or regularly visited, presents considerable challenges: it requires good information and specialist communication strategies around risk mitigation, preparedness, response, and recovery dependent on the state of the volcano, e.g. pre-, during- and post-eruption. In this chapter, we present an overview of volcanic ballistic hazards and impacts and the communication strategies used to manage risk on active volcanoes.

# 2 Ballistic Hazard and Risk Management

Ballistic projectiles are a risk to life on active volcanoes and can cause substantial damage to exposed infrastructure and the environment due to their high kinetic energy, mass, and often high temperatures (Blong 1984). Volcanic ballistic projectiles are amongst the most frequent causes of fatal incidents on volcanoes, with at least 76 recorded deaths at six volcanoes (Galeras, Yasur, Popocatepetl, Pacaya, Raoul Island and Ontake) since 1993 (Baxter and Gresham 1997; Cole et al. 2006; Alatorre-Ibargüengoitia et al. 2012;

Wardman et al. 2012; Tsunematsu et al. 2016). Many more people have been injured as a result of ballistic impacts, frequently suffering from blunt force trauma (broken bones), lacerations, burns, abrasions and bruising (Blong 1984; Baxter and Gresham 1997). Additionally, damage to buildings (Fig. 1c, e), infrastructure, property and the surrounding environment (Fig. 1d) are also common occurrences from ballistics during explosive eruptions. The high kinetic and thermal energy of ballistics can puncture, dent, melt, burn and knock down structures and their associated systems, such as power supply and telecommunication masts; crater roads; and crush and potentially ignite crops (Booth 1979; Calvari et al. 2006; Pistolesi et al. 2008; Alatorre-Ibargüengoitia et al. 2012; Wardman et al. 2012; Maeno et al. 2013; Fitzgerald et al. 2014; Jenkins et al. 2014). Blong (1981), Pomonis et al. (1999) and Jenkins et al. (2014) estimate a ballistic only needs 400–1000 J of kinetic energy to penetrate a metal sheet roof, far less than the estimated kinetic energy of ballistics (~$10^6$ J) from VEI 2-4 eruptions (Alatorre-Ibargüengoitia et al. 2012).

The distribution (distance from vent, direction, area and density) of ejected ballistics is controlled by the explosivity, type, size and direction of explosive eruptions, and usually creates spatially variable deposits (Gurioli et al. 2013; Breard et al. 2014; Fitzgerald et al. 2014). Generally, the distance travelled and the total area impacted by ballistics increases with increasing explosivity, i.e. particles generally travel further and cover a greater area in Vulcanian eruptions (Nairn and Self 1978; Alatorre-Ibargüengoitia et al. 2012; Maeno et al. 2013) compared with Strombolian eruptions (Harris et al. 2012; Gurioli et al. 2013; Turtle et al. 2016). However, eruptions can be directed, ejecting ballistics at low angles and at distances greater than those from more vertically directed eruptions (Fitzgerald et al. 2014; Tsunematsu et al. 2016). The directionality of these blasts is often unpredictable, and can be influenced by external factors such as landslides (Christiansen 1980; Breard et al. 2014), making it difficult to deterministically forecast future ballistic
<figure><img src="image_50.png" /><figcaption>**Fig. 1** Types of ballistic particles and their impacts: a Ballistic bombs from Yasur Volcano, Vanuatu (*Photo credit* Ben Kennedy), b Ballistic blocks (1.4 m diameter block) from the August 2012 Upper Te Maari eruption, c Damage to a building from ballistics ejected in the 2000</figcaption></figure>

Mt. Usu, Japan eruption, d Damage to the environment illustrated by a 4.4 m wide crater from the August 2012 Upper Te Maari, Tongariro eruption, e Damage to a hiking hut from 2012 Upper Te Maari ballistics (*Photo credit* Nick Kennedy)

distributions. Mapped deposits from past eruptions are often not symmetrical around the vent, reflecting this directionality (Minakami 1942; Fudali and Melson 1972; Steinberg and Lorenz 1983; Kilgour et al. 2010; Houghton et al. 2011; Gurioli et al. 2013; Fitzgerald et al. 2014), and are sometimes the result of the crater and surrounding topography (Breard et al. 2014; Tsunematsu et al. 2016). Detailed descriptions and maps of ballistic impact distributions are rare, but those published may contain some of the following data: maximum ballistic travel distances (Steinberg and Lorenz 1983; Robertson et al. 1998; Kaneko et al. 2016); the outer edges of a ballistic field (Minakami 1942; Nairn and Self 1978; Yamagishi and Feebrey 1994); and/or maximum particle (Nairn and Self 1978; Steinberg and Lorenz 1983; Robertson et al. 1998;

Swanson et al. 2012) or crater size (Robertson et al. 1998; Maeno et al. 2013; Kaneko et al. 2016). When isopleths of particle size are included these rarely contain individual measurements and may be severely limited by the availability of only specific mapped locations (e.g., Kilgour et al. 2010; Houghton et al. 2011). For this reason, the number of particles, sizes of particles, and spatial density per unit area is rarely reported (only four publications could be found with this level of detail—Pistolesi et al. 2008; Swanson et al. 2012; Gurioli et al. 2013; Kaneko et al. 2016). This leads to a limited understanding of the hazard and risk posed to the area.

Though work has been completed on ballistic hazard (e.g., mapping deposits, better understanding eruption dynamics and the factors that
influence ballistic distribution, recording particle velocities, the creation and use of ballistic trajectory models, and the production of hazard maps either focussed solely on ballistics or as an aspect of a multi-hazard map), very little has been focussed on the management of ballistic risk, leaving a large knowledge gap and a need for research in this area. Risk management strategies and mitigation systems are key to protecting life and infrastructure from ballistic hazards (Leonard et al. 2008; Bertolaso et al. 2009; Bird et al. 2010; Jolly et al. 2014b). Table 1 lists some of the strategies and tools used at volcanoes around the world.

Effective communication of ballistic hazard and risk to end-users such as the public, stakeholders in the area and emergency managers underpins effective development and implementation of these risk management strategies. However, ballistic hazard and risk are not and should not be treated the same at all volcanoes. The risk environment (the hazard, the number of people and assets exposed and their associated vulnerability) will determine the strategies, tools and methods of communication, and their relative importance, utilised in the overall risk management strategy. The volcano tourism industry is also growing (Sigurdsson and Lopes-Gautier 1999; Erfurt-Cooper 2011), increasing the number of people exposed to ballistic hazard in proximal areas. In addition, population growth in many volcanic regions means increasing numbers of people are settling closer to and on volcanoes (Small and Naumann 2001; Ewart and Harpel 2004). This creates an increasing demand for ballistic hazard and risk assessments coupled with effective communication strategies to manage ballistic risk at volcanoes. Ballistics are not a hazard in isolation. Their management needs to be integrated with that of other volcanic hazards (especially pyroclastic density currents in terms of near-vent life safety, but also landslides, lahars, lava flows, and volcanic gas emissions/areas of hot ground), and other life safety issues such as severe weather and mountain safety.

### 3 Assessments of Ballistic Hazard and Risk

Successful management of the risk from ballistic hazards typically requires first assessing the level of risk. This may range from the simple recognition that ballistics may endanger people or their activities on a volcano through to a sophisticated quantitative hazard or risk assessment (e.g. Alatorre-Ibargüengoitia et al. 2012; Jolly et al. 2014b). Ballistic hazard assessments determine the likelihood of ballistic-producing eruptions and the areas that may be impacted (Thouret et al. 2000; Alatorre-Ibargüengoitia et al. 2012). Risk assessments estimate the likelihood of consequences (i.e. death, injury, damage) from exposure to ballistics, typically with an associated probability of occurrence (Blong 1996). Once the level of risk has been assessed it can be used as the robust basis for risk management strategies, such as exclusion zones, hazard/risk maps and signs, and land-use planning. Ideal assessments involve a number of steps including: (1) a review of the eruption history of the volcano to determine past eruption frequencies and magnitudes, thus informing future eruption probabilities; (2) field mapping, remote sensing and/or review of past reports and literature to determine the nature and extent of past ballistic distributions; (3) utilising ballistic trajectory models to explore possible future distributions and areas of hazard; (4) identifying exposed assets in the area such as humans (visitors and inhabitants) and infrastructure; and (5) estimating their vulnerability to the hazard i.e. likelihood of fatality or damage (Nadim 2013). Assessments are ideally probabilistic, providing spatially varying probabilities of occurrence and damage from a range of scenarios varying in frequency and magnitude, and accounting for model and input parameter uncertainty. They should be constantly refined and improved as new information becomes available.

A hazard map is a primary tool used to present hazard and risk information (Sparks et al. 2013). Zonation is generally used as a means to
<table><caption>**Table 1** Risk management and communication strategies with selected example volcanoes where they have been employed</caption><thead><tr><td>Risk management strategy</td><td>Description</td><td>Selected examples of volcanoes where strategy has been used</td><td>References</td></tr></thead><tbody><tr><td>Hazard and risk assessments</td><td>Hazard assessments determine the likelihoods of hazard producing events and the areas that may be impacted. These can be expanded to risk assessments to determine the likelihood of consequences to people and/or other societal assets. They underpin and inform other risk management strategies</td><td>Tongariro Mt. Fuji Popocatepetl El Chichon</td><td>Mount Fuji Disaster Prevention Council (2004), Alatorre-Ibargüengoitia et al. (2012), Jolly et al. (2014b), Alatorre-Ibargüengoitia et al. (2016)</td></tr><tr><td>Hazard and risk maps</td><td>Identify zones of relative hazard and/or risk, typically in a two dimensional representation</td><td>Popocatepetl Mt. Fuji</td><td>Mount Fuji Disaster Prevention Council (2004), Alatorre-Ibargüengoitia et al. (2012)</td></tr><tr><td>Volcano monitoring and research</td><td>Systems deployed on and around a volcano to monitor volcanic activity, and indicate when the volcano is in unrest or eruption. Research is also conducted on the eruptive behaviour (e.g. magnitude and style) and eruption frequency of a volcano</td><td>Mt. Etna Tongariro Sakurajima Mt. Ontake</td><td>https://www.geonet.org.nz/volcano/info/tongariro; http://www.ct.ingv.it/en/mappa-stazioni.html; JMA (2013a, b)</td></tr><tr><td>Real-time warning systems</td><td>To monitor and detect a hazardous event (e.g. eruption) and communicate a warning to those potentially exposed.</td><td>Ruapehu</td><td>Leonard et al. (2008), Keys and Green (2010)</td></tr><tr><td>Volcanic alert levels, bulletins and media advisories</td><td>Formal communications from a volcano observatory which communicate changes in volcano behaviour, notify emergency managers and the population of an eruption and advise on mitigation.</td><td>Yasur Tongariro</td><td>https://www.geonet.org.nz/volcano/info/tongariro; http://www.geohazards.gov.vu/</td></tr><tr><td>Emergency response plans</td><td>Plan for directing response actions which aim to reduce the impacts of an eruption. Plans are best executed with training and exercises in their use</td><td>Ruapehu Sakurajima</td><td>Leonard et al. (2008); http://www.city.tarumizu.lg.jp/kikikanri/kurashi/bosai/bosai/taisaku/sakurajima.html</td></tr><tr><td>Rescue services</td><td>Deploy in emergencies to provide aid to affected persons and properties, e.g. Search and Rescue, police, ambulance, and fire services</td><td>Ontake Ruapehu</td><td>Kilgour et al. (2010), The Japan Times 27/9/2015</td></tr><tr><td>Land use planning</td><td>Policy and regulations used to minimise or exclude the development of settlement and construction of high-value assets in hazard zones.</td><td>Usu Volcano Tongariro Ruapehu</td><td>Becker et al. (2010), Keys and Green (2010)</td></tr></tbody></table>

(continued)
<table><caption>**Table 1** (continued)</caption><thead><tr><td>Risk management strategy</td><td>Description</td><td>Selected examples of volcanoes where strategy has been used</td><td>References</td></tr></thead><tbody><tr><td>Construction of protective shelters</td><td>Structures designed to withstand specific hazards e.g. ballistic shelters in high-risk areas</td><td>Sakurajima Aso Stromboli</td><td>Bertolaso et al. (2009), Erfurt-Cooper (2010)</td></tr><tr><td>Exclusion or restriction zones</td><td>Area restrictions commonly used temporarily during eruptions or unrest. Permanent zones may be required when risk is sufficiently high or frequent</td><td>Sakurajima Stromboli</td><td>Bertolaso et al. (2009), Kagoshima City (2010)</td></tr><tr><td>Stakeholder engagement</td><td>Involvement of stakeholders (e.g. people and organisations potentially affected by an eruption) in planning and activities to manage the risk. This is essential for effective hazard and risk communication, and to establish appropriate and acceptable risk management strategies</td><td>Tongariro Sakurajima</td><td>Williams and Keys (2013), Jolly et al. (2014b), http://www.data.jma.go.jp/svd/vois/data/fukuoka/506_Sakurajima/506_bousai.html</td></tr><tr><td>Hazard and risk education resources</td><td>Education resources which aid communication of hazard and risk information, often developed specifically for non-expert stakeholders. These can include pamphlets and brochures, websites, warning signs, videos, and public talks and meetings.</td><td>Auckland Volcanic Field, Tongariro</td><td>DOC (2012), Wilson et al. (2014)</td></tr></tbody></table>

distinguish areas of hazard, exposure, vulnerability and risk (Sparks et al. 2013). Ballistic hazard map zones may be classified by maximum travel distance of particles (either any size or a specific sized particle; Alatorre-Ibargüengoitia et al. 2012), number of ballistic impacts per unit area (Gurioli et al. 2013), probability of a specific size of ballistics reaching a given area (Artunduaga and Jimenez 1997), or probability of a specific consequence occurring e.g. death, injury, damage (Fitzgerald et al. 2014). A good example of a ballistic hazard map that follows the best-practice steps above was created by Alatorre-Ibargüengoitia et al. (2012) of Popocatepetl Volcano, Mexico. In this example, eruption history and frequency of occurrence are used to define three eruption scenarios (High: VEI 2–3 (as they are more frequent), Intermediate: 4, and Low: 5 (though an eruption of this

size would affect more people and impact a larger area, it has a much lower likelihood of occurring). The maximum travel distance of ballistic projectiles from each scenario (based on field and model distributions) is then used to define the extent of the hazard zones. Additionally, the map identifies nearby towns and roads exposed to ballistic hazard.

In many instances, it may not be possible or warranted to complete all of the steps involved in an ideal risk assessment. For example, Gareloi Volcano, Alaska is located on an uninhabited island, thus a detailed ballistic hazard assessment was not the priority of initial hazard assessments. Coombs et al. (2008) explore the eruptive history of Gareloi Volcano, though eruption frequency is only narrowed down to one eruption every 20–50 years and is not broken down into eruption magnitudes. Ballistic hazard is confined to
one hazard zone (a 5 km concentric radius
around the vent), whose extent is based on
Blong's (1996) assessment that ballistics gener-
ally do not travel further than 5 km from vent. It
is also mentioned that recent ballistic distribu-
tions have not travelled further than several
hundred metres from vent. Neither a determin-
istic or probabilistic approach was taken, instead
a value was adopted from other eruptions around
the world.

Very few studies exist on ballistic risk or
vulnerability. We summarise the three that could
be found. Booth (1979) presents an example of a
volcanic risk map for the La Primavera Volcanic
Complex, Mexico. Though ballistics are inclu-
ded, they are not ascribed a probability of
occurrence, instead, one zone at risk of ballistic
fall is defined by the maximum travel distance
for ballistics up to 0.1 m in diameter. The
equation that Booth used to calculate risk
includes probability of occurrence, indicating
that eruption frequency has been examined;
however, neither the probability used nor the
description of prior eruptive history are provided
in the publication. Thus, though an end-product
of a risk map is produced, the process itself is not
documented. Pomonis et al. (1999) utilise the
Blong (1981) impact energy thresholds for roof
perforation to assess building vulnerability from
an eruption of Furnas Volcano, the Azores. Two
risk zones are assigned (moderate and high)
based on the statement that ballistics generally
land within 5 km of the vent, but sometimes up
to 10 km. The study only considers one eruption
(the last major eruption), thus is lacking eruption
frequency and magnitude, and does not provide
any probabilities of building damage occurring.
Building vulnerability to ballistic impact has
been assessed by Jenkins et al. (2014) for Kan-
laon and Fogo volcanoes (Philippines and Cape
Verde, respectively) using estimates of energy
required to penetrate roof materials by Blong
(1981) and Pomonis et al. (1999). This study,
however, focussed only on the vulnerability of
the built environment and did not include an
overall assessment of hazard or risk. Eruption
frequency and magnitude, the extent of past

ballistic distributions, and modelling of possible
future trajectories were not investigated.

Assessments may also vary depending on the
state of the volcano. Volcanoes in a state of
quiescence allow for (and call for) more in-depth,
preferably probabilistic, assessment to be com-
pleted, ideally following the steps outlined ear-
lier. However, quiescent volcanoes may not be
the primary target for in-depth assessment.
Conversely, renewed volcanic activity, especially
when unexpected, urgently demands rapid hazard
assessments which may, as a result, be too sim-
plistic, overly conservative or lacking sufficient
detail to be considered complete. They also need
to be focussed on the range of scenarios pre-
senting the risk in that crisis (e.g. from one vent),
rather than the entire background risk from that
volcano (e.g. from multiple vents). Leonard et al.
(2014) describe the process of creating a crisis
hazard map for the 2012 Upper Te Maari erup-
tion, comparing this to the existing background
hazard map. In the case of a volcano in a state of
unrest, assessments may be limited by the
availability of safe locations to survey, and this is
especially likely once an eruption episode has
commenced as evident during the 2012 Upper Te
Maari, Tongariro eruptions and assessments
presented later. Odbert et al. (2015) have been
developing updateable hazard forecast estimates
using Bayesian belief networks, which may help
to improve rapid hazard assessments in times of
crisis.

4 Communication and Risk Management Strategies

Effective communication is essential in manag-
ing ballistic hazard and risk (Barclay et al. 2008;
Leonard et al. 2014). Science needs to be com-
municated to decision-makers, stakeholders, and
the public and understood and absorbed by them
so they can make informed decisions. Similarly,
the public, stakeholders, and decision-makers
should communicate to scientists what type of
information they need to make decisions relevant
to their situations. Ballistic communication
methods used at volcanoes include hazard and risk assessments, hazard maps, volcano monitoring and research, real-time warning systems, volcanic alert levels; volcano warnings, alert bulletins and communication with agencies; response exercises, education materials, response plans, exclusion and evacuation zones, instructions and signage for what to do in the event of an eruption around the volcano, community engagement, educational materials, and land-use planning and infrastructure design. These methods typically fall under four aspects of emergency management: Mitigation (Reduction), Preparedness, Response and Recovery (UNISDR 2009). Methods must also be integrated with the management of other risks, ideally in one cohesive approach. Ballistic communication strategies will also vary with eruption frequency, the risk context (quiescence or crisis; Fig. 2), whether

volcanoes are frequently visited or inhabited, and the availability of resources. This equally applies to volcanoes at which ballistics are/are not the main hazard.

Effective risk management is built on communication, hazard education and engagement with the at-risk communities (Johnston et al. 1999, 2000; Paton et al. 2001; Twigg 2002; Gregg et al. 2004; Leonard et al. 2008; Dohaney et al. 2015). Appropriate risk management actions by stakeholders, emergency managers and the public require an adequate perception of the risk and the correct actions to take in a crisis, with perception dependent on the hazard information received and exposure to impacts (Johnston et al. 1999; Leonard et al. 2014). Knowledge and understanding of volcanic hazards allows individuals to better decide whether to undertake preparedness and response measures, and if so,

<figure><img src="image_51.png" /><figcaption>**Fig. 2** Various ballistic hazard and risk communication processes (blue) and products (red) implemented over the changing state of the volcano and the stage of risk or</figcaption></figure>

emergency management. The level of activity/importance is indicated by *line style*, with *solid lines* indicating higher use or importance
which are required, thus reducing their vulnera-
bility to the hazard(s) (Siegrist and Cvetkovich
2000; Paton et al. 2008; Bird et al. 2010).

Scientific information can be misunderstood,
misrepresented or distorted when passed from
scientists to end-users (stakeholders, emergency
managers and the public; Barclay et al. 2008).
This can occur when end-users do not compre-
hend or are unaware of the science being pre-
sented, the information is not what is actually
needed by end-users, the science is communi-
cated poorly to end-users, or there is a lack of
trust between groups (Haynes et al. 2007). All
groups therefore need to communicate with each
other, preferably prior to a volcanic crisis, with
communication products tailored to the audience
(Haynes et al. 2007; Leonard et al. 2008). Fol-
lowing the 1979 eruption of Mt. Ontake, Japan
the National Research Institute for Earth Science
and Disaster Prevention in Japan (NIED, though
now renamed to National Research Institute for
Earth Science and Disaster Resilience) com-
pleted a report recommending: regulations on
development and land-use, building of ballistic
shelters and evacuation facilities, and the devel-
opment of emergency plans, as an eruption in the
summer hiking season would likely result in
human casualties (NIED 1980). However, the
report may not have been suitable or communi-
cated well to the local municipalities responsible
for disaster management as these recommenda-
tions were not adopted prior to the 2014 eruption,
indicating the need for communication to ensure
the information is relevant, understood and acted
upon (Barclay et al. 2008; The Japan News,
27/10/2014). Communication delivered jointly
by scientists and the local community is also
advisable as community members may be better
trusted and better communicators to their com-
munity than scientists in isolation. Users must be
able to trust the source of the information being
released as well as how and what is presented
(Slovic 2000; Haynes et al. 2008). It is also
therefore important for scientists and emergency
managers to be honest about what is/is not
known to maintain credibility and trust (Lindell
2013).

Best practice suggests the use of multiple
sources to disseminate hazard and risk informa-
tion as preferred forms of media accessed for
information vary (Sorensen 2000; Mileti et al.
2004; Haynes et al. 2007; Bird et al. 2010). The
public's response to volcanic hazard communi-
cation is influenced by the content and attrac-
tiveness of the message (which should include a
description of the hazard, its impacts, hazard
extent, and advice on what to do and when), how
comprehensible it is, and the frequency and
number of channels the message is received
from, as well as the extent of public belief that
safety actions are possible and will be effective
(Leonard et al. 2008; Sorensen 2013).

## 4.1 Ballistic Communication Processes and Products in Different Risk Contexts

4.1.1 Volcano Quiescence

Communication and risk management methods vary with changing eruptive states. In times of quiescence focus is placed on risk mitigation and preparedness, with access generally allowed into the hazard zone. In terms of ballistics this includes the completion of ballistic hazard and risk assessments; volcano monitoring and research; land-use and building planning i.e. the building of ballistic shelters capable of withstanding ballistic impacts or the reinforcement of existing structures to specific building standards, and the choice of location for hiking trails, viewing platforms or other visitor facilities; the creation of well distributed hazard maps with instructional text with what to do or where to go in an event of an eruption; and engagement with the local communities including exercises and evaluation (Fig. 2).

Hazard and risk assessments are useful start-
ing points for all communication and manage-
ment strategies as the nature, extent and
consequences of the hazard need to be under-
stood prior to any decisions being made. The
assessment should be made available to relevant
decision makers, with the authors and science
advisors available to advise or answer questions about the assessments. Scientists/authors should always strive to be transparent in their methodology. Transparency builds trust and credibility. It is important that stakeholders know the limitations of the information presented to them and/or informing decisions which affect them. It may not be needed or appropriate for the methods to be presented to the stakeholders in depth but instead it be communicated that they are available if requested. However, it is imperative to think of the risk context when making these decisions, as every situation is different. Methods and assessments should also be made fully available to other scientists so that these methods can be adopted at other volcanoes if chosen, which would increase best-practice and encourage similar and comparable methodologies. These assessments also need to be communicated to the public so that they can make informed decisions about the hazard and risk in the area they choose to enter as well as what steps they need to take to protect themselves.

The main way assessments are communicated is through a map (Haynes et al. 2007). Ballistic hazard maps are rare as they are typically not the only hazard produced in an eruption. Instead ballistics are typically included in ‘all-hazard’ or ‘multi-hazard’ maps (Fig. 3) depicting the general hazard for all active vent(s) (Neal et al. 2001; Hadisantono et al. 2002; Mount Fuji Disaster Prevention Council 2004; Kagoshima City 2010; Leonard et al. 2014). Ballistics are usually represented by one hazard zone, often based on the maximum or expected travel distance of a ballistic clast. This is, in part, because the public require concise, easily comprehensible information, rather than being distracted or overloaded with specifics of individual hazards (Haynes et al. 2007; Leonard et al. 2014). An effective hazard map for the public contains clear information on what are the consequences of the hazard(s), where they occur, and what to do (Leonard et al. 2014). For ballistics, impacts may be death or injury; impact locations are usually within 5 km of the vent; and advice may include “if ballistics are landing around you, move out of their oncoming path, seek shelter and make

yourself a small target.” Advice on actions to be taken may vary at different volcanoes, although it would be beneficial if messages are consistent across all volcanoes to reinforce actions and increase the likelihood of people following the correct actions. For this to occur, testing of suggested actions would be required to ensure that the safest and most successful measures are being advised. For example, where frequent Strombolian eruptions are the main source of ballistics, it may be possible to watch the low velocity ballistics and move out of their path. However, in many other eruption styles multiple particles may be ejected rapidly toward a person, presenting a situation in which dodging one ballistic may put you in the path of another. It may be more beneficial to make yourself as small a target as possible, seek shelter and use your backpack as a protective shield. Additionally, ballistics may be accompanied by a surge as seen in the 2014 Mt. Ontake (Kaneko et al. 2016; Oikawa et al. 2016) and August 2012 Te Maari eruptions (Breard et al. 2014), inhibiting the ability to see ballistics until it is too late to act.

Map design should also take into account the effect of map properties on communication (understanding/comprehension) such as data classification, basemap or image, colour scheme (e.g. for colour blind readers), content, and key expression (Haynes et al. 2007; Thompson et al. 2015). Haynes et al. (2007) evaluated the effectiveness of volcanic hazard maps as communication tools on Montserrat, West Indies and found that the use of aerial photographs as a basemap improved people’s ability to comprehend hazard information compared to traditional contour basemaps. In general, it has been found the public do not comprehend maps well and professional design input guided by iterative evaluation of map comprehension is wise (Haynes et al. 2007; Thompson et al. 2015). In contrast to the public, more specialist stakeholders such as infrastructure managers may require more detailed and hazard specific information about the impacts, location and recommended actions to inform decisions on land-use and building strength e.g. ballistics impacts in zone 1 can be expected to have sufficient energy
<figure><img src="image_52.png" /><figcaption>**Fig. 3** Volcanic hazard maps of Tongariro volcano, New Zealand: **a** General background hazard map used in quiescent periods (GNS Science 2007), focussed on hazards from events up to a scale that may not have significant precursors to enable warning; **b** Event-specific</figcaption></figure>

crisis hazard map following the 2012 eruptions of Upper Te Maari (GNS Science 2012). Note that map A is shown as an *inset* on map B with an explanation as to the complementary but differing nature of the two communication products

to cause severe damage to nearly all types of infrastructure below a certain design standard. Multiple zones of different impact intensity may be shown (e.g. travel distance, density of impacts in an area, size and or energy of expected ballistics in given scenarios). All end-user maps should successfully balance adequate detail and maximum clarity. Hazard maps and additional information should be made available and accessible to the public, and if different maps are made for, or directed to, different audiences their content must be consistent. Public availability may include being posted on signs around the volcanoes entrance(s), in a pamphlet or similar printed media at tourist facilities (e.g. information centres, tourism businesses, hotels, backpackers accommodation, transport operators), and on relevant websites such as volcano

observatories and those charged with managing natural hazards.

Additionally, community engagement and participation in meetings with scientists and managers is encouraged as a means of risk communication, and discussion around management strategies, especially for communities at risk (i.e. tourism providers and those living near or on the volcano) (Cronin et al. 2004; Williams and Keys 2013). Ballistic hazards lend themselves to this type of community engagement because many open system volcanoes that may be constantly erupting but not considered to be in a state of volcanic crisis (e.g. Stromboli, and Yasur) have frequent ballistic-producing eruptions that provide an attraction to tourists and employment for the local community. Ballistics at these constantly erupting volcanoes provide
tangible hazards that the community can both relate to and provide valuable observational data on. Meetings should be sufficiently regular to update residents when the status of a volcano is changing and to remind them when necessary of the hazards and risks. Briefing those new to the area, especially the transient visitor, may be the biggest challenge. Engagement allows the community to be prepared in the event of an eruption and to know what to do in the event that they are within hazard areas.

### 4.1.2 Volcanic Crisis

In a volcanic crisis (when the volcano is showing signs of unrest or is in eruption) communication and emergency management processes and products move toward response (Fig. 2). Real-time warning systems triggered by monitoring equipment, such as the EDS (Eruption Detection System) system installed on Mt. Ruapehu, New Zealand (Leonard et al. 2008), are used to communicate an eruption to those in the immediate vicinity. Wider communication occurs when an event is communicated from monitoring equipment to scientists, then onto emergency managers and decision-makers. Part of this process is the release of alert bulletins/warnings to advise the public of unrest, eruption phenomena, affected areas, and should always include instructions on what to do. Alert bulletins, existing hazard maps and risk and hazard assessments provide emergency managers with information to make decisions on limiting access to parts of the volcano. In the case of ballistics, limits or restrictions on access or development are usually achieved via creation of an exclusion zone, typically 1–4 km in radius (Kagoshima City 2010; Jolly et al. 2014b), or by reducing exposure by limiting the time spent or number of individuals allowed within a zone (Bertolaso et al. 2009).

During the crisis, hazard maps are typically updated and hazard and risk assessments modified. Maps are generally event-specific and only used over a short time-frame, reverting back to the original background hazard maps once the crisis period is over (Leonard et al. 2014; Fig. 3). However, ballistic hazard mapping during a

<figure><img src="image_53.png" /><figcaption>**Fig. 4** Crisis communication sign temporarily used at Ruapehu volcano following a small eruption in 2007, while it was considered there was an elevated risk of further eruptions</figcaption></figure>

crisis can be limited by access restrictions due to the possibility of further eruptions, though as time progresses more detailed mapping is able to be completed (Fitzgerald et al. 2014). The ongoing work by Odbert et al. (2015) in developing a real-time updateable probabilistic risk assessment may prove useful in these situations. The event-specific hazard maps are generally shared around the various media outlets (e.g., television, radio, newspapers, Facebook, Twitter) to inform the public of the updated hazard, as well as through the usual means of communication. They may be augmented by specific life safety signage (e.g. Fig. 4).

Meetings and consultations with local communities, emergency managers and other stakeholders should also occur during and following volcanic crises. The objectives of such meetings are to update communities on the evolving eruptive hazards, build relationships and trust, reduce any miscommunication or misinformation
passed along, and to make sure the information being presented is what the end-members need (Barclay et al. 2008; Bertolaso et al. 2009).

Communication of ballistic hazards and risk management vary at frequently erupting volcanoes that commonly enter in and out of crisis, such as Sakurajima in Japan. Access is generally controlled at all times (even during periods of quiescence), sometimes with permanent restriction zones in which nobody is allowed to enter due to the risk of being struck by ballistics (Kagoshima City 2010). In these cases different hazard scenarios may be pre-prepared and communication strategies reused with a population that is well educated about the volcano.

## 4.2 On-Going Challenges in Ballistic Risk Communication

Many volcanoes are tourist destinations with associated tourist facilities such as ski fields, accommodation and walking tracks (Erfurt-Cooper 2011). One challenge of communicating ballistic risk is to transient populations, especially tourists and other visitors. Tourists spend only a short amount of time in areas (hours to weeks) and often have little knowledge of the hazards or the available protection resources (Murphy and Bayley 1989; Drabek 1995; Burby and Wagner 1996; Bird et al. 2010). They often rely on tourism operators/employees/guides to inform them of volcanic hazards and the correct actions to take in an eruption (Leonard et al. 2008; Bird et al. 2010). This is evident at Yasur Volcano, Vanuatu where guides are frequently relied on to communicate ballistic hazard and safe areas to approach around the volcano, and at Tongariro Volcano, New Zealand where transport operators can give important information to 85% of all those hiking the Tongariro Alpine Crossing (TAC). However, tourism staff may also be somewhat transient, meaning that they may need to be regularly educated, trained or updated on volcanic hazards, appropriate responses and emergency procedures so that they can pass the message down to their patrons (Leonard et al.

2008; Bird et al. 2010; Williams and Keys 2013). Additionally, education material such as pamphlets and hazard maps on volcanic hazards should not only be available at tourism businesses but mechanisms should be in place that ensure that the hazard information is relayed to these transient populations.

Another ongoing challenge in communicating ballistic hazard is the lack of warning time associated with events that have little precursory activity, in which ballistics are typically one of the main hazards. In this scenario volcanic alert levels and bulletins may not be released prior to eruption. Instead, visitors and stakeholders would have to rely on their knowledge of the potential hazards and the response actions to take, especially if there are no real-time warning systems. This places more emphasis and weight on the availability of background hazard maps with messaging covering actions in events up to this size, signage around the volcano (in language(s) appropriate for the audience to comprehend, especially if there is a large proportion of visitors who speak a different language), on pamphlets distributed to businesses and visitors actually reading them, and through communication with their guides. Many visitors to the TAC still assume that they do not need to be concerned because they expect the area to be closed if it is unsafe or to be advised it was unsafe (Keys 2015).

We present the various ballistic risk management and communication approaches taken at four volcanoes: Upper Te Maari, Tongariro Volcanic Complex, New Zealand; Yasur Volcano, Vanuatu; Sakurajima Volcano, Japan and Mt. Ontake, Japan (Table 2). These volcanoes have been chosen for their variation in: frequency of eruption (Sakurajima and Yasur frequently erupt, while Upper Te Maari and Mt. Ontake have longer repose periods), available resources (Yasur has less monitoring equipment and hazard information available than the other three examples), eruptive styles—Yasur predominantly erupts bombs from small Strombolian eruptions; compared with phreatic eruptions from Mt. Ontake and Upper Te Maari and Vulcanian eruptions from Sakurajima that erupt blocks over a larger area, and the similarity in eruptions but with very
<table><caption>**Table 2** Comparison of the four case studies and their risk management and communication strategies</caption><thead><tr><th></th><th>Upper Te Maari</th><th>Yasur</th><th>Sakurajima</th><th>Mt. Ontake</th></tr></thead><tbody><tr><td>Dominant eruptive style</td><td>Hydrothermal</td><td>Strombolian</td><td>Vulcanian</td><td>Phreatic</td></tr><tr><td>Recurrence interval</td><td>~16 years</td><td>Frequently erupting</td><td>Frequently erupting</td><td>~13 years</td></tr><tr><td>Duration of precursory activity</td><td>3 weeks of seismicity, 5 min of increasing seismicity</td><td></td><td></td><td>2014: 16 days seismicity, 11 min increasing seismicity and inflation</td></tr><tr><td>Number of visitors</td><td>100,000 visitors/year</td><td>20,000 visitors/year</td><td>3,702,000 visitors/year</td><td>Hundreds of visitors per day</td></tr><tr><td>Hazard map with ballistics</td><td>Background and crisis</td><td>Yes</td><td>Yes</td><td>Two background maps</td></tr><tr><td>Volcano exclusion and evacuation zones</td><td>Yes</td><td>Yes</td><td>Yes</td><td>Yes</td></tr><tr><td>Volcanic Alert Levels</td><td>Yes</td><td>Yes</td><td>Yes</td><td>Yes</td></tr><tr><td>Education material</td><td>Yes</td><td>Yes</td><td>Yes</td><td>Yes</td></tr><tr><td>Volcano monitoring</td><td>Yes</td><td>Yes</td><td>Yes</td><td>Yes</td></tr><tr><td>Land-use planning and infrastructure design</td><td>Ketetahi Hut (not reinforced). TAC runs through summit hazard zone</td><td>No shelters or buildings. Track and viewing platforms along rim of volcano</td><td>Concrete shelters around island, evacuation ports</td><td>Mountain lodges and shrines (not reinforced). Tracks near active craters</td></tr><tr><td>Community engagement</td><td>Yes</td><td>In progress</td><td>Yes</td><td>Yes</td></tr><tr><td>Response exercises</td><td>No</td><td>No</td><td>Yes</td><td>Yes</td></tr><tr><td>Evaluation and improvement</td><td>Assessments updated post-eruption, creation of crisis hazard map</td><td>Currently assessments and maps are being updated</td><td>Last update of hazard map was in 2010</td><td>New hazard map released November 2015</td></tr><tr><td>Signage around volcano</td><td>Yes</td><td>Yes</td><td>Yes</td><td>Yes</td></tr><tr><td>Volcano warnings, alert bulletins and communication with external agencies</td><td>Yes</td><td>Yes</td><td>Yes</td><td>Yes</td></tr></tbody></table>

different consequences between Upper Te Maari and Mt. Ontake. Additionally, all of these volcanoes are relatively accessible and attract large numbers of tourists each year.

# 5 Case Studies

## 5.1 2012 Eruptions of Upper Te Maari, Tongariro, New Zealand

On the 6th August 2012, Upper Te Maari Crater, one of the many vents on Tongariro volcano, New Zealand, erupted for the first time in over 100 years (Scott and Potter 2014). The

hydrothermal eruption produced multiple pyroclastic surges, an ~8 km high ash plume and ejected thousands of ballistic blocks (Fitzgerald et al. 2014; Lube et al. 2014; Pardo et al. 2014). Blocks were distributed over a 6 km² area, affecting ~2.6 km of the popular Tongariro Alpine Crossing (TAC), a walking track frequented by around 100,000 people a year (Fitzgerald et al. 2014). Additionally, Ketetahi Hut, an overnight hut along the TAC, was severely damaged by ballistics. Fortunately, the eruption occurred at night, in winter (the low season) and in bad weather, resulting in no hikers along the TAC or staying at Ketetahi Hut (both around 1.5 km away from the vent and well within the impacted area). A smaller eruption
followed on 21 November 2012, though ballistics and pyroclastic surges were confined to within a well posted risk management zone 1 km from the vent and did not affect the TAC.

Ballistics were a known hazard from the active vents of Tongariro, witnessed in the 1974–5 Ngauruhoe eruptions (Nairn and Self 1978). As such they were described on the background hazard map for the volcano (Fig. 3a). The map, published in 2007, consists of a summit hazard zone around each active vent, encompassing gas and ballistics at radii of 2–3 km for different vents based on experience of ballistic ranges in past eruptions at Tongariro National Park. Work is underway to develop ballistic and life safety models to better inform zone radius. Pyroclastic density currents (PDC’s) and lava flows are not included in a hazard zone but are mentioned as a possibility in all valleys. Ashfall is stated as a hazard that could occur any place on the map. Text is provided, with instructions including to move quickly down off the mountain and away from summit hazard areas, though ballistics-specific advice was not provided (GNS Science 2007). The background hazard map with associated instructions was permanently posted at the entrances to the walking tracks up the volcano, was available on the GNS and DOC websites as well as on flyers at many of the tourist hubs (Leonard et al. 2008, 2014). The TAC hiking track cuts through most of the summit hazard zones, where access has been open at background levels. One hut, Ketetahi Hut, is located within the summit hazard zone, though is not reinforced to protect against ballistic impact.

Unrest was observed at the volcano up to three weeks before the eruption, initially in the form of increased seismicity and then increased magmatic gas content (Jolly et al. 2014a). In response the Volcanic Alert Level was raised from 0 to 1 (indicating unrest). Seismicity declined in the days prior to eruption and thus the TAC remained open to tourists (Jolly et al. 2014b), with seismicity reoccurring only ~5 min before the event (Jolly et al. 2014a). In the build-up to the eruption, a decision was made to complete response plans and create a crisis hazard map initially for the whole volcanic massif with some focus on the

northern flank of Tongariro. However, it was not publically available before the August 6th eruption (Leonard et al. 2014). GNS volcanic alert bulletins were also produced, communicating updates on the precursory phenomena observed at Tongariro (Volcanic Alert Bulletins TON-2012/01–04; Fig. 5e). Meetings and other discussions were held with the local residents and businesses involved with the TAC to discuss the situation and future scenarios. Being wintertime, there was very little use of the track. As there was no one on the hiking trail during the eruption it is difficult to assess the success of the hazard communication strategies, and these strategies would have been different during summer months with heavy track use.

Following the August event, some of the local population evacuated for the night and the TAC was closed for two months due to the risk of further eruption. Within this two-month period an updated hazard and risk assessment was completed (Jolly et al. 2014b). This involved a combination of reviewing the eruptive record to understand eruption frequency and magnitude, and expert elicitation by GNS staff (the institute responsible for monitoring volcanoes and assessing their hazard/risk) working closely with the land manager (Department of Conservation) to produce three possible future eruption scenarios (a 21 November size eruption, a 6 August size eruption, and a magnitude larger eruption) and associated probabilities of these occurring. Probabilities were re-assessed every week immediately after eruption, which was subsequently extended to every month, then every three months as time passed. Hazard extent was considered for ballistics and PDC’s for each scenario, exposure time along the impacted area, and the vulnerability (probability of fatality) of an individual to each hazard (using the area of hazard around an individual impact for ballistics, and the presence of a person in the path of a PDC), to calculate the combined risk of fatality for all scenarios (Jolly et al. 2014b).

Initial assessments suggested that ballistics were the main hazard to life from the eruption, though detailed mapping was not able to be carried out until months later when risk levels
<figure><img src="image_54.png" /><figcaption>(a)</figcaption></figure>

<figure><img src="image_55.png" /><figcaption>(b)</figcaption></figure>

## Eruption Hazard Awareness

### Te Maari Eruption Craters 2013

<figure><img src="image_56.png" /></figure>

**Rahui**

Ngāti Hāriki is Tongariro, who have Manawatu's territorial rights over these lands, have declared a Rahui (protective restrictions to uphold a traditional Maori custom (Tīkanga Maori) which respects the Mana (prestige) of the Maunga (mountains). This is to ensure that the spiritual, emotional, cultural and physical wellbeing of Tongariro and all people who come to enjoy the experience of Tongariro are protected. The Rahui extends across a 1 km radius around the Te Maari eruption site, as indicated on the map over the page. Do not enter this area.

**Read carefully:**

* The area known as Upper Te Maari Crater on the northern side of Mt Tongariro erupted from several vents on 6th August and 21st November, 2012.

* You will still be at some risk from further volcanic eruptions if you are within the Active Volcanic Hazard Zone around Te Maari (see map over the page).

* There are signs at the edge of the Active Volcanic Hazard Zone.

* You should move quickly through this Active Volcanic Hazard zone.

* Another eruption could happen without warning.

* The main dangers are burning ash clouds and flying rocks.

**Should an eruption occur:**

* Stop, look for burning ash clouds and flying rocks.

* Run away from the path of fast-moving burning ash clouds.

* Otherwise **fled shelter** behind something - banks, ridges or in hollows.

* Don't turn away from flying rocks unless you are sure they won't hit you.

* Get out of the Hazard Zone along one of the indicated escape routes. Stay together. Your escape route may be uphill, downhill or to the west away from the eruption site.

<figure><img src="image_57.png" /></figure>

**Other hazards:**

* Falling ash - Not normally hazardous at Tongariro. If caught, don't panic but move away from the area as quickly as possible.

* Gas - Lahar - Move quickly through or avoid valley during heavy rain or eruption.

**Electronic lights and other signs:**

* Read them and know what they mean.

* When lights are red or flashing, do not proceed.

* Amber lights mean risk is higher than normal.

* Green lights mean risk is normal (not no risk).

Always check weather conditions before leaving, wear footwear suitable for rough track conditions, and take clothing suitable for wet, windy and cold weather.

Department of
Conservation
Te Papa Atawhai
New Zealand Government

<figure><img src="image_58.png" /><figcaption>(d) Maari</figcaption></figure>

<figure><img src="image_59.png" /></figure>

## Volcanic Alert Bulletin TON-2012/07 - Tongariro Volcano

7 August 2012, 12:15 pm - Update; Alert Level remains at Level 2; Aviation Colour Code changed to Orange

### View the Tongariro current activity page

#### What to do in a volcanic eruption

A short lived phreatic eruption occurred at the Te Maari craters area on Mount Tongariro at approximately 11:50 pm last night (Monday, 6 August 2012). Activity at the present time consists of steam clouds and some small earthquakes. Eruptive activity is low level but could recommence at any time.

Observations of Mount Tongariro this morning by GNS Science are that eruption activity has subsided. White steam clouds were observed at the historically active Te Maari craters area but poor weather conditions at the time obscured a direct view of the active vent(s). There have been no lahars or pyroclastic flows or lava flows.

Our analysis of seismic data is that there was an explosive eruption lasting only a minute or two, followed by a series of discrete small earthquakes over the next few tens of minutes. No volcanic tremor occurred in the days preceding the eruption, nor has any occurred since then.

It is too early to predict the next series of events, but we expect heightened activity may continue for several weeks. There are likely to be specific signals of future magma movement beneath the volcano and we continue to monitor the situation through the GeoNet volcano-seismic network of

<caption>(e)</caption>

### Q. Search Blogs

OCTOBER 2012

SEPTEMBER 2012

AUGUST 2012

Volcanic Alert Bulletin TON-2012/24 - Tongariro Volcano

Volcanic Alert Bulletin WI-2012/15 - White Island Volcano

Volcanic Alert Bulletin TON-2012/23 - Tongariro Volcano

Volcanic Alert Bulletin WI-2012/14 - White Island Volcano

Volcanic Alert Bulletin TON-2012/22 - Tongariro Volcano

Volcanic Alert Bulletin TON-2012/21 - Tongariro Volcano
◄ **Fig. 5** Risk communication methods used at Tongariro, New Zealand. **a** Electronic signs communicating risk level and track closure at entrances to the volcano and where it crosses the AVHZ. **b** Signs advising area of increased hazard including a track-specific AVHZ hazard map. **c** Additional information on volcanic hazards at Tongariro (including ballistics), initially handed out to all

had decreased (Fitzgerald et al. 2014; Jolly et al. 2014b). The Department of Conservation (DOC), the agency responsible for hazard and risk management at Tongariro, began to implement risk management as part of a recovery programme. The risk assessments by Jolly et al. (2014b) became an important tool for making decisions about reopening. A new, event-specific Te Maari hazard map was created using mapped deposits and the most likely hazard scenarios, in which the main hazard zone was increased to a 3 km radius (choosing the larger potential radius based on historic events) down-slope and deliberately renamed the Active Volcanic Hazard Zone (AVHZ) to distinguish it from the former map (Fig. 3b). It included ballistics, explosions, pyroclastic density currents, lahars, gas and rockfall (Jolly et al. 2014b). The accompanying text to the crisis hazard map was also updated, with a ballistic specific instruction to ‘seek immediate shelter from flying rocks if an explosion occurs’ (GNS Science 2012). The map was released to the public alongside a Volcanic Alert Bulletin describing the changes made to the map and the source of the data (Volcanic Alert Bulletin TON-2012/23). This was distributed to the media (print, television, web and radio) to inform a wider audience (Leonard et al. 2014). Additionally, the map was posted at either ends of the track and where it crossed the boundaries of the AVHZ. Cordons, initially manned, were established at either ends of the TAC to prevent hikers from entering. Later, the cordon was moved to Emerald Lakes (on the edge of the 3 km Volcanic Hazard Zone) as the track was partially reopened. With declining risk of further eruption (based on the trend of the eruption probability estimates made by GNS to estimate how the expert elicitation might evolve over time), the

hikers, provided on Department of Conservation website. **d** GeoNet website showing monitoring data such as Volcanic Alert Level, seismic drums and visuals of the volcano. **e** A Volcanic Alert Bulletin issued on the GeoNet website and distributed to media following the 2012 Upper Te Maari eruption

track was fully opened 5 ½ months after the 21 November eruption.

DOC also published educational information on the eruption hazard at Te Maari including further advice on actions to take in an eruption (Fig. 5c). This included to ‘stop, look for flying rocks’, to ‘find shelter behind something—banks, ridges or in hollows’, to not turn away from ‘flying rocks unless you are sure they will not hit you’ and to ‘get out of the Hazard Zone along one of the indicated escape routes’ (Department of Conservation 2012). In October 2013 electronic warning signs were installed that informed hikers of the status of the volcano—a red flashing light meant danger-turn back, orange elevated risk and green normal volcanic activity (Jolly et al. 2014b, Fig. 5a). A survey of 203 hikers on the TAC in March-May 2014 indicated that most people saw these signs when activated red and understood the messages irrespective of their native language (Keys 2015). A reinforced public shelter and warden’s quarters was one option being considered to replace the damaged Kete-tahi Hut. Now the favoured option is to replace it with facilities outside the AVHZ.

## 5.2 Yasur Volcano, Vanuatu

Yasur Volcano is a frequently erupting basaltic scoria cone located on Tanna Island, Vanuatu (Cronin and Sharp 2002). Strombolian and Volcanian eruptions have been relatively continuous since 1774 (Eissen et al. 1991). Ballistics are the main hazard produced by these eruptions, responsible for multiple fatalities in the past (Baxter and Gresham 1997). Yasur is one of Vanuatu’s main tourist attractions with some twenty thousand people visiting the crater rim
each year. The vast majority of people are guided up the volcano by local guides to watch the eruptions occur, with a main viewing area only 150 m from the crater's inner rim. As the majority of people in the area are transient tourists, guides are often relied upon to relay hazard and risk information to their patrons. Volcanic alert levels (VALs) and bulletins are posted on the Vanuatu Meteorology and Geo-Hazards Department (VMGD) website when the behaviour of the volcano changes. These sometimes include hazards maps that provide the locations of where bombs have been observed or are likely to impact, and often caution the public to approach the crater or hazardous areas with care. Maps also urge visitors, tourist agencies and communities to seriously consider the information provided prior to ascending Yasur (Vanuatu Geohazards Observatory 2009). However, advice or instructions are not given for what to do if caught in an area where ballistics are landing. A hazard map is displayed at the carpark before the ascent up the cone, highlighting the 1999 lava bomb impact zone and the observation location for each volcanic alert level—as the alert level increases so does the distance of the observation position from the cone (i.e. restriction zones are emplaced). In addition, visitors to Yasur are warned by a sign to ‘Think Safety’ before ascending the crater rim, though no further instructions or information is provided. As it is frequently erupting, it is assumed that visitors accept the risk that they are entering into an active volcanic hazard zone.

An updated risk management framework has been developed from 2012 to 2016 including updated bulletins and VALs, background and safety (crisis) hazard maps, and tourist information including education and safety map information. This is associated with an upgrade of Vanuatu's active volcanoes to real-time warning (at the time of writing this included a seismometer and webcam on Yasur and daily OMI satellite monitoring of SO₂ emissions; Vanuatu Geohazards Observatory 2014), supported by the New Zealand Aid Programme and GNS Science in partnership with VMGD. This integrated

framework allows for pre-planning of safety zones related to ballistics and other hazards, and integration with warning products such as bulletins, VALs and tourist information. Ballistic zone ranges will initially be based on historic event ranges, but will be updated to include the modelling being developed in New Zealand, once available.

## 5.3 Sakurajima Volcano, Japan

Another frequently active volcano in which ballistics are a major hazard is Sakurajima Volcano, Japan. Continuous Vulcanian eruptions have occurred since 2009 from the andesitic composite cone (Japan Meteorological Agency 2013b). Sakurajima is constantly monitored by the Sakurajima Volcano Observatory and is considered to be one of the best monitored volcanoes in Japan (GSJ 2013). When activity changes, alert levels are posted on the Japan Meteorological Agency (JMA) website for the public to view. Many people live in close proximity to the volcano (~4900 within 5 km of the volcano) and millions visit the Kagoshima-Sakurajima area each year (3,702,000 in 2010; Japan Meteorological Agency 2013b), thus JMA and Kagoshima City released a volcanic hazard map with additional information in 2010. This map was distributed to local citizens and posted around the volcano. Three relevant zones are delineated on the map: the first is a 2 km radius (from the active craters) restricted area in which both residents and tourists are restricted from entering at all times; the second is ~3 km away from the active vents showing the area expected to be inundated with volcanic bombs in a 'strong eruption', and lastly a 6 km radius extends around the active vents where 'volcanic rock' is likely to impact from a 'great eruption' (Kagoshima City 2010). Definitions for 'strong eruption' and 'great eruption' are not provided, nor is an explanation of the data that these zones are based on. The hazard map also includes societal components such as important landmarks i.e. schools and the visitor centre, and evacuation buildings and ports. The other half of the map consists of information on precursory
phenomena likely to be felt and who to call if detected; how volcanic warnings will be disseminated and the measures needed to be taken; what the five volcanic alert levels are/what activity is expected and the consequent actions needed to be taken; information on major historic eruptions and recent activity; and evacuation procedures. An English version of the map is available in addition to the original in Japanese. This information is also available on the official tourism website of Kagoshima City (http://www.city.kagoshima.lg.jp/soumu/shichoshitu/kokusai/en/emergency/sakurajima.html). Ballistics (called 'cinders') are additionally listed on the site as a possible volcanic hazard accompanied by a description, particle size and travel distance. To prepare for a future eruption from Sakurajima, Tarumizu City (Kagoshima Prefecture) runs an emergency response exercise every year (http://www.city.tarumizu.lg.jp/kikikanri/kurashi/bosai/bosai/taisaku/sakurajima.html).

Three other notable risk communication and mitigation measures have been implemented at Sakurajima. A Volcano Disaster Prevention Council was created as a means of communication to discuss disaster prevention measures between volcanologists, local government, JMA, and other invested agencies (http://www.data.jma.go.jp/svd/vois/data/fukuoka/506_Sakurajima/506_bousai.html). Secondly, signs instructing people on the distance and direction to the nearest eruption safe house and evacuation port have been posted around the volcano. Lastly, concrete roofed shelters have been built around the island to protect visitors from falling ballistics (Erfurt-Cooper 2010).

## 5.4 2014 Eruption of Mt. Ontake, Japan

Mt. Ontake is a stratovolcano located on the island of Honshu, Japan (Japan Meteorological Agency 2013a). It is not a continuously active volcano with four eruptions (all phreatic) in its historic record (1979, 1991, 2007 and 2014; Japan Meteorological Agency 2013a; Smithsonian Institution 2013).

Mt. Ontake straddles the boundary of two prefectures—Gifu and Nagano, with trails on either side. Both prefectures have developed hazard maps for two eruption scenarios that include ballistics—the first a phreatic eruption similar in size to the 1979 eruption (VEI 2) and the second a larger eruption on the scale of 90,000–20,000 year recurrence interval (Nagano hazard map: http://vivaweb2.bosai.go.jp/v-hazard/L_read/53ontakesan/53ontake_2h03-L.pdf; Gifu hazard map: http://vivaweb2.bosai.go.jp/v-hazard/L_read/53ontakesan/53ontake_2h01-L.pdf). In both maps, ballistic hazard is defined by a 4 km asymmetric zone around an asymmetric vent area encompassing the 1979 vents—the same vents that erupted in the 1991 and 2007 eruptions. The parameter by which the zone is based on is not provided (e.g. maximum travel distance, spatial density of impacts) and no advice accompanies the hazard map, though a residents’ handbook was printed that included examples of what ballistics are and how far they can travel. The maps and handbooks are available on the NIED database and the prefectural government websites, though the map is not signposted around the volcano.

Mt. Ontake is constantly monitored by the JMA, with seismometers, GPS stations, tiltmeters, cameras and infrasonic microphones (Japan Meteorological Agency 2013a). In addition, preparedness communication measures also include Volcanic Alert Levels, in place since 2008 (Japan Meteorological Agency 2013a). Similarly to other volcanoes, these VALs range from 1 to 5 and include whether the alert level is a warning or forecast, the target area (e.g. crater area or more distal residential areas), the expected volcanic activity and phenomena with examples of previous cases, actions needed to be taken and also keywords accompanying the level (e.g. level 5 with ‘evacuate’).

The 27 September 2014 phreatic eruption occurred at lunchtime on a busy autumn day when ~340 hikers were on the mountain (Tsunematsu et al. 2016). Multiple pyroclastic surges were produced, travelling up to 2.5 km from vent, in addition to ballistics that impacted up to 1 km from the vent (Kaneko et al. 2016;
Tsunematsu et al. 2016). Fifty-eight people were killed in the eruption, 55 most likely the result of ballistic trauma relatively close to the summit, with five still missing (as of 24 June 2016; Tsunematsu et al. 2016). An increase in summit seismicity was noted 16 days prior to the eruption resulting in the JMA releasing notices about volcanic activity, though activity was not at levels significant enough to raise the Volcanic Alert Level (there needed to be signs of deformation, which were not recorded until just prior to eruption; The Japan News, 26/10/14; Ui 2015). The eruption was largely unexpected with 11 min of precursory tremor, and uplift detected only seven minutes before the event (Ui 2015). This was a much shorter period of precursory activity than previous eruptions. The 1979 eruption was preceded by earthquake swarms for a year and five months. A month of seismicity was noted prior to the 1991 eruption, increasing in frequency just days before the event. And the 2007 eruption was preceded by inflation and seismicity for three months, accompanied by increasing fumarolic activity the week prior (Japan Meteorological Agency 2013a). Longer periods of precursory activity allow time for warnings to be issued. JMA released warnings prior to the 1991 and 2007 events, although the resulting eruptions were very small, only impacted the immediate area and occurred in winter outside the climbing season (Japan Meteorological Agency 2013a). However, if it had been possible to issue a warning when the precursory activity increased on the day of the 2014 eruption, it is unlikely that it would have resulted in no fatalities. Any evacuation warning prior to an event would need to occur at least an hour before the event and be immediately transmitted to all hikers on the summit area as it takes over an hour for hikers to move out of the ballistic hazard zone. Nonetheless, even a short warning time may have provided more hikers time to get to shelter.

Following the eruption, the Volcanic Alert Level was increased to 3, warning people not to approach the volcano (as access was restricted),

and that blocks may be ejected up to 1 km from vent (based on previous eruptions). Signs were posted around the volcano telling people to “keep out” of the restricted area. Search and Rescue teams were deployed to rescue the injured hikers and those that sheltered in the buildings at the summit, and to recover the dead. Those that sheltered in the buildings around the summit survived the 2014 eruption, while many of the fatalities occurred due to hikers choosing to take photos and video of the eruption outside instead of running to the nearest hut. Half of the people autopsied by one doctor were found with cell-phones in hand while one person’s camera was found with a photo taken 4 min after the eruption occurred (Mainichi Shimbun 10/10/2014). Some then attempted to shelter around the summit shrine which they could not gain access to (the summit shrine is only open from the beginning of July to early September). Fatalities also occurred in exposed areas where there were no buildings in sight to shelter within. Personal safety measures taken by exposed hikers saved lives. This included sheltering behind large rocks, placing backpacks on heads, and wearing hard hats provided inside the mountain huts (NHK 2015).

Numerous risk management and communication tools have since been adopted. Prior to the eruption, Gifu and Nagano prefectures had separate commissions to manage volcanic activity from Mt. Ontake. Following the 2014 eruption they have combined to form one commission for the entire volcano, improving communication between the prefectures and subsequently to the public. The commission, similar to the Sakurajima council, is comprised of volcanologists, local government, JMA and other interested agencies (http://www.pref.nagano.lg.jp/kisochi/kisochi-sei saku/ontakesan/kazanbousaikyougikai.html). The council ran its first eruption evacuation drill on 4th June 2015.

Interviews conducted post-eruption showed that many climbers were unaware of the volcanic activity notices released, while of those that were aware 76% did not consider that they needed to be prepared for an eruption (The Japan News
26/10/2014; Shinano Mainichi Shimbun 2015). JMA subsequently launched a website to provide climbers with its observations of the volcanic activity around Japan, in an attempt to improve communication to climbers. From the 1st April, 2015 the Gifu Prefectural Government made it mandatory for all climbers of Ontake to submit a mountain climbing notification form prior to ascending Mt. Ontake, in an effort to improve knowledge of the number and location of people on the mountain, and to improve communication in times of crisis by recording their emergency contact information (http://www.pref.gifu.lg.jp/English/tourism/mountain/). Kiso, a town in the Nagano Prefecture responsible for one of the mountain trails, has also installed loudspeakers in the mountain cabins prior to easing restrictions in September 2015 (The Japan Times 27/09/2015).

In November 2015, a new hazard map was released by the Ontakesan Volcano Disaster Prevention Council (the combined commission mentioned previously). It provides two ballistic hazard zones—one for a phreatic eruption that extends 2 km from the vent area, and one for a larger magmatic eruption, extending 4 km from the vent area (http://www.city.gero.lg.jp/hazardmap/#12/35.9073/137.5203). The zones are based on research completed for Mt. Fuji on past ballistic distributions from phreatic and magmatic eruptions in Japan and around the world (Mount Fuji Disaster Prevention Council 2004). The asymmetric vent area has also been increased significantly, encompassing 3 km in length and ~2 km in width. In addition, further research has been completed on the ballistic hazard produced in the eruption. Tsunematsu et al. (2016) describe an elongated distribution toward the N-NE resulting from an inclined ejection and topographic controls such as the shape of the valley the vents formed in. The spatial distribution was mapped from aerial photos by Kaneko et al. (2016) and delineated into four zones. The densest zone (A) encompasses areas with impact densities >10 impacts per 5 × 5 m, decreasing in density with distance from the vent to Zone C which has between 0 and 2 impacts per 5 × 5 m.

# 6 Discussion

## 6.1 Understand the Context and Assess the Risk

We identify from review of literature and analysis of the four case study volcanoes (Table 2) that understanding the risk context is highly important for effective communication associated with ballistic hazard and risk. Establishing this context and identifying potential risks requires engagement with potential stakeholders, such as those which may be exposed or affected by ballistic, or other, volcanic hazards. Effective communication is an essential component of this. Once these steps are complete, we then suggest that a ballistic risk assessment is undertaken to help underpin effective management and communication of ballistic hazard and risk. Best-practice ballistic risk assessment generally consists of: (1) reviewing the volcano's eruptive history to establish eruption frequency and eruption magnitude; (2) determining the nature and extent of past ballistic distributions; (3) exploring possible future ballistic distributions; (4) identifying assets exposed in the area; and (5) estimating the asset's vulnerability. Once complete, risk can be evaluated and appropriate management and communication strategies implemented. However, we stress that risk assessment alone cannot underpin effective communication of ballistic hazard and risk. But must be carried out in conjunction with the tools and strategies listed in Table 1 and Fig. 2.

It is important to remember that every context is different and what works at one volcano does not necessarily mean it will work or is needed at another. An assessment for a frequently erupting, highly visited volcano where risk management organisations are well resourced will require a different approach compared with an infrequently active, rarely visited volcano in a country where there are few resources available for risk management. The scope and scale of risk management activities should be guided by the risk context, and determine which and how risk management tools and strategies are used.
## 6.2 Reflections on the Four Case Study Volcanoes

All of the volcanoes studied are capable of sustaining injuries and fatalities from ballistics. The Mt. Ontake 2014 eruption resulted in the most fatalities from any of the case studies, and provides a chance to analyse why this was so with the aim of preventing it from occurring again. Multiple factors contributed to the high fatality rate:

* The eruption happened in peak season when ~340 people were on the mountain.

* Precursory activity only increased 11 min prior to eruption, resulting in an unexpected eruption. This meant no warning was able to be issued to the people on the summit and no closure of the summit prior to the event occurred. Previous eruptions had precursory events that gave more warning of the impending eruption underscoring that past history should not be solely relied on to predict outcomes of future unrest.

* The Alert Level was not raised following increased seismicity beginning 16 days before the eruption. A requirement for this to occur is the presence of ground deformation, which was not recorded until 7 min before the eruption.

* Hikers chose to take images and video of the eruption instead of finding shelter. This decision may have been different had hazard maps been posted around the volcano with instructions on actions to take in an eruption.

Fatalities from ballistics could occur at all of the case study volcanoes. However, a scenario with fatalities on the scale seen at Ontake is unlikely from Sakurajima due to the 2 km restriction zone. Yasur is visited by much fewer tourists than Ontake so it is unlikely to see as many fatalities from one event as occurred at Ontake, although the lack of shelter, lack of hazard advice, and proximity to the vent means that ballistic casualties are still relatively likely at this volcano. Work is ongoing to reduce this risk. The August 2012 eruption of Upper Te Maari is the most comparable to the Ontake eruption as it was

largely unheralded and of the same explosivity. If the August 2012 eruption had occurred in peak tourist season, then a similar amount of fatalities as Ontake potentially could have occurred.

## 6.3 Critical Issues

We identify the following critical issues for contemporary and future communication of volcanic ballistic risk, based on our review of literature and analysis of the four case study volcanoes. We note many of these issues transcend volcanic ballistics to include nearly all volcano types and volcanic hazards:

* What is the most effective way to manage and communicate risk from volcanoes which are (highly) visited and/or settled which experience eruptions with very short and/or no meaningful warnings (e.g. Ontake, Te Maari)? This is a critical issue for managing ballistic risk, as eruptions with longer unrest phases typically allow evacuation of ballistic hazard zones before the eruption.

* What are the most appropriate risk management and communication strategies for volcanoes where ballistic (and other) risk is present which have poorly understood eruptive histories and/or monitoring systems?

* Effective ballistic risk assessment requires greater understanding of (a) the distribution of ballistic from a range of potential eruption styles, (b) the impact of ballistics to people and other societal assets (vulnerability/fragility characteristics), and (c) identification and (crucially) evaluation of what are the most appropriate mitigation actions to reduce ballistic risks before, during and after an eruption.

* Successful management of ballistic risk requires effective engagement (of which communication is a keystone) between authorities responsible for managing risk at volcanoes, those people and organisations who may have economic, cultural and social connections with a volcano, and the scientific community who can help inform hazard and (sometimes) risk considerations. Organisational and governance frameworks to
allow and facilitate this seem to be highly vari-
able globally, but some relatively successful
examples do exist (e.g. New Zealand).

* How to manage future risk, particularly for volcanoes where there is significant existing use and/or strong pressure to utilise the resources through tourism (increasing visitor numbers to high risk areas), and agricultural and settlement pressure from population growth.

7 Conclusions

Ballistic projectiles ejected in explosive erup-
tions present a major proximal hazard to life,
infrastructure and the environment. An increas-
ing population living on or close to active vol-
canoes and a growing volcano tourism industry
give rise to an increased number of people
exposed to ballistic hazard, presenting a consid-
erable need for detailed ballistic hazard and risk
assessments, and specialised communication and
management strategies. Recommended strategies
would include at least the following:

(1) Hazard and risk assessments (ideally probabilistic) specific to the volcano in question, which include ballistics where appropriate, that are made available to emergency managers and decision makers with authors/ scientists available to answer questions and advise where necessary and practical;

(2) The inclusion of ballistic hazard zones in hazard maps with accompanying advice on what to do. Maps should be updated in a crisis to reflect new information and readily available through a range of media. These maps should continue to be updated after the event when detailed scientific studies are complete;

(3) Volcano monitoring systems to monitor volcanic activity and indicate when a volcano is in unrest;

(4) The use of signage around the volcano to communicate ballistic hazard and risk, integrated with other hazard advice, including warning systems where practical, and with a focus on effectiveness of communication rather than just providing information;

(5) The use of volcanic alert bulletins, media releases or reports to communicate ballistic hazard and risk in crisis phases;

(6) Open, sufficiently frequent communication between scientists, stakeholders, emergency managers and local communities in which updates and training are provided, and informed input made into management and mitigation measures.

These strategies may vary with eruptive state
(quiescence or crisis), frequency of eruptions,
availability of resources, and whether ballistics are
the main hazard at the particular volcano. In
addition to the strategies mentioned in this chap-
ter, further work is needed to test and update the
advice provided to visitors on the actions to take in
a ballistic eruption, in particular personal protec-
tive measures. Effort should also be made to pro-
vide consistent advice at all volcanoes on the
actions to be taken, depending on the volcanic
hazards involved. This way the information would
be reinforced with visits to different volcanoes and
increase the likelihood of visitors acting correctly.

**Acknowledgements** Funding for this study was provided by DeVoRA (Determining Volcanic Risk in Auckland) and a New Zealand Earthquake Commission (EQC) Biennial Grant (16/727). RHF is also supported by a doctoral scholarship from the Ngāi Tahu Research Centre. We wish to thank Bill McGuire and an anonymous reviewer for their thorough and constructive reviews.

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# Imagining the Unimaginable: Communicating Extreme Volcanic Risk

Amy Donovan and Clive Oppenheimer

## Abstract

This chapter considers the challenges surrounding the management of extreme volcanic risk. We examine eruption scenarios based on past episodes and assess the key issues that might arise should similar events occur in the future. The nature of such eruptions will entail transboundary and multi-scalar hazards. In a globalised world, the geopolitical and societal issues that are likely to emerge cannot all be predicted, and communication technologies themselves are likely to be affected. We explore two aspects: communication prior to the eruption, and communication during the eruption. To the best of our knowledge, all large eruptions are presaged by sensible phenomena but the enduring challenge for volcanic hazard assessment and risk management will remain the uncertainty surrounding evaluations of the likelihood, timing, nature and magnitude of potentially damaging activity. At present, too, communication of volcanic risk beyond the borders of the country where the volcano is located is generally patchy and unsystematic in most parts of the world (with the exception of the threat of ash clouds to aviation). In the preparatory phase, it is also critical to establish robust communication strategies that are resilient during an eruption. Such strategies would be essential for communicating the availability of supplies, the extent and nature of damage, and the ongoing status of the eruption.

<footnote>A. Donovan (✉)
Department of Geography, King's College London,
The Strand WC2R 2LS, UK
e-mail: amy.donovan@kcl.ac.uk</footnote>

<footnote>C. Oppenheimer
Department of Geography, University of Cambridge,
Downing Place, Cambridge CB2 3EN, UK</footnote>
# 1 Introduction: Extreme Eruptions

Large magnitude volcanic eruptions are rare events with typically long return-periods (less frequent than ~1 in 1000 years) at any single volcano (Oppenheimer and Donovan 2015).<fnref n="1" /> These range from large magnitude effusive basaltic lava eruptions to explosive super-eruptions. Basaltic lava eruptions, such as the 1783–4 Laki eruptions, are hazardous largely through their emissions of sulphur and halogens to the atmosphere, both locally and via long-range atmospheric transport. Such impacts include problems with air quality, disturbance of terrestrial and marine ecosystems, local contamination of water supplies (e.g. by fluorine leached from ash particles) and climate change. These eruptions may continue episodically for years. In contrast, large magnitude explosive eruptions usually last days or weeks, but can have more prolonged impacts. One estimate for an eruption with 100 times the sulphur yield of Pinatubo suggests that it would impact the climate strongly for approximately ten years (Timmreck et al. 2012). Such an event could have major impacts on food security, energy security and other critical networks.

The challenge of communicating these risks is multi-scalar and multi-dimensional: the potential impacts in the near-field to the far field are diverse, but are linked through the structures that manage them, such as local authorities and nation states. Such events and their impacts can transcend scale and are better defined by relationality: the relationships between groups of scientists with different responsibilities, political/policy groups, populations in different places, and a particular but as yet unidentified volcano. The volcano can be viewed as a geographical anchor in the physical landscape, to which different types of human network are connected. When we discuss communication of extreme volcanic risk, we are effectively examining the nature of the network connections and how they operate. Volcanic risk from large

eruptions is fundamentally a systemic risk of low probability but high impact. Communicating such risk requires a very broad approach: the events are potentially global, they would require management by institutions at multiple levels, and they would involve input from a very wide range of experts, stakeholders and citizens (Fig. 1).

Here, we concentrate on aspects of the problem in two different timeframes (pre-eruption and immediate) and two particular but overlapping communication types (those between scientists and policymakers, and between scientists and populations). Initially, we define two scenarios for a large magnitude eruption. We then focus on the nature of systemic risks, and explore generalities of the communication of global systemic risks, focussing on the pre-eruption timeframe (by which we mean the period prior to any detection of anomalous activity). We examine the immediate period, when signals are detected and then an eruption commences. We argue that these two timeframes are not entirely distinct: it is critical that relationships and knowledge exchange takes place pre-eruption in order that it underpins communication in an immediate setting. The subject of this paper is challenging because it deals with scenarios not experienced in recent history, and therefore the discussion is sometimes necessarily speculative. However, we have drawn on examples both from volcanic crises and from the wider risk literature.

# 2 Volcanic Risk Scenarios

In this section, we outline two particular extreme volcanic risks, and discuss the likely challenges presented by each. This provides the context for the subsequent discussion in the paper.

## 2.1 Large Magnitude Basaltic Eruptions

The 1783–4 Laki Fissure eruption has been extensively studied (e.g. Thordarson and Self 1993, 2003; Thordarson et al. 1996; Schmidt et al. 2011, 2012; Hartley et al. 2014).

<footnote n="1">¹In this paper, we focus on the impact of large magnitude eruptions. However, we note that a smaller eruption at the wrong time and in the wrong place could produce an extreme event, and some of the implications discussed in this paper may be relevant to such a scenario.</footnote>
<figure><img src="image_60.png" /><figcaption>**Fig. 1** Examples of the complex web of ideas, institutions, infrastructure and groups involved in the management of extreme volcanic risk</figcaption></figure>

Thordarson and Self (1993) estimated that this eruption produced fire fountains up to 1.4 km high, sourcing plumes that rose into the stratosphere. Schmidt et al. (2011) modelled the potential air quality consequences of a comparable eruption occurring today and suggested that the long-range exposure to volcanogenic particulate it could significantly increase cardiopulmonary mortality across Europe. Thordarson and Self (2003) further implicated the eruption in the hot summer of 1783 and cold winter of 1783–4. Beyond climate impacts, such an eruption in the contemporary world could have a significant impact on aviation—especially if the eruption continued for months or years.

The 2014–15 volcanic eruption in Holuhraun, north of Vatnajökull, in Iceland represents an analogue for such an eruption, albeit at about a tenth of the magnitude scale. Precursory activity to this eruption was roughly two weeks in duration, with evidence for dyke propagation (Sigmundsson et al. 2014) from a central volcano, starting on 16 August 2014 and the first subaerial eruption on 29 August. Based on this scenario, there would be roughly two weeks’ warning that magma was rising. As was demonstrated during the precursory activity

however, it is very challenging for volcanologists to forecast what is to the uncertainty in interpreting monitoring data from volcanoes, in general, is a theme that pervades the literature (e.g. Baxter et al. 2008; Marzocchi et al. 2012).

A large magnitude basaltic eruption could produce two primary hazards over large areas—gas hazard and climate forcing. In the near-field, lava flows and tephra could be a problem. Gas hazard would affect the immediate area around the volcano, but its dispersion would be heavily dependent on the height of the plume and the meteorological conditions (e.g. Schmidt 2014). For example, SO₂ from the Holuhraun eruption reached parts of Ireland and Norway (Schmidt et al. 2015; Gettelman et al. 2015). The extent of any climate forcing would be dependent on aerosol formation and transport, at least in the short term, and on the duration, seasonality and latitude of the eruption (e.g. Schmidt et al. 2012). In this scenario, then, the hazard would be spatially specific but long-range and variable. Forecasts of the hazard would be heavily dependent on meteorological data and models and source constraints—such as SO₂ flux measurements and plume height distribution. Management of the hazard would defer to individual
nation-states in the first instance, but in the event of more prolonged and regional scale climatic disturbance there would be a need for a collaborative response to manage any adverse impacts on food production and distribution. If the eruptions occur in a populated area and/or a small country, evacuations to other nations might be necessary. Air quality deterioration would affect healthcare provision, especially for those with existing respiratory illness. Air quality issues and airborne ash could also affect aviation at regional scale, and airspace closures would have to be managed reflexively during a long, fluctuating eruption.

## 2.2 Large Magnitude Explosive Eruptions

Large magnitude explosive eruptions (>M6, according to the scale of Mason et al. (2004)), and super-eruptions (M8) can result in regional to global scale effects on climate (depending on sulphur yield to the atmosphere, location and timing) and regional scale devastation. Climate impacts from a 100× Pinatubo SO₂ release, for example, were modelled by Timmreck et al. (2012), and include decadal-scale global cooling of several degrees. This kind of scenario has major implications for food production globally. It would also affect trade, transportation and communication, particularly close to the source but with ripple-effects worldwide due to the nature of commercial aviation and global markets, and supply and distribution networks. Super-eruptions may even pose an existential risk (e.g. Rampino 2002). The complexities and diversity of the direct and indirect consequences of such large events make it very difficult to assess the risks in a meaningful way, and indeed it could be said that there have been no comprehensive efforts to assess the integrated impacts of a super-eruption on global society. Hereafter, we focus on an M8 scenario similar to that of the Youngest Toba Tuff (YTT) eruption, circa 74 ka BP.

A large magnitude eruption would yield >10 km³ of tephra in a matter of hours or days. In explosive eruptions of this size, substantial ash clouds are generated and associated plumes would circumnavigate the globe within a few weeks. Pyroclastic flows would likely extend tens of km from the volcano. The estimated minimum tephra mass for the YTT is 2 × 10¹⁵ kg (Rose and Chesner 1990): an eruption of this magnitude could affect the continental scale with severe implications for farming and agriculture. A major uncertainty in such an eruption is the volatile budget. There has been considerable debate concerning the sulphur yield of the YTT eruption, for example (e.g. Rampino and Self 1992; Oppenheimer 2002; Williams 2012), and there is even less consensus on the halogen yields of such large eruptions. Cadoux et al. (2015) for example showed that halogen inputs from the large Minoan eruption of Santorini could have had significant impacts on atmospheric ozone. In any case, contamination of water supplies and ecosystems over large areas would likely lead to major food security problems. This could provoke or exacerbate epidemics and social unrest (Oppenheimer and Donovan 2015). While the prospect of such a global hazard can result in a return to environmental determinism (e.g. Rampino 2002), so widely condemned in the disasters literature (e.g. Raleigh et al. 2014), it nevertheless raises the question of global vulnerability and the complexity of networked societies and nations. While many studies have examined the impacts of past large magnitude eruptions (e.g. Oppenheimer 2011), there are no recent analogues to assess the impact of such an eruption on modern globalised society—particularly the impacts on technologies, including communication, transportation and power.

## 2.3 Volcanic Risk Webs

Approaches to volcanic eruption management have traditionally attempted to follow the so-called linear model, in which scientists
produce evidence that they use for a risk assessment, which is then presented to policymakers who make decisions and then communicate those decisions to the public (e.g. Marzocchi et al. 2012). However, the empirical literature in volcanology and in other fields of environmental policy demonstrates that the linear model is flawed in practice because scientists and policymakers are part of the “public” and make social inferences throughout the process, as well as being affected by a range of political factors (e.g. Owens 2005; Owens et al. 2006; Jasanoff 1990, 2005; Donovan and Oppenheimer 2014). In essence, decision-making is networked and web-like, not linear, and communication and decision-making are not readily disentangled, since decisions will be interrogated by stakeholders. For example, during and after the 2010 eruption of Eyjafjallajökull in Iceland, the UK press attacked the Met Office's handling of the crisis (Harris 2015). Furthermore, large magnitude eruptions will not fit easily into human boundaries—national or institutional. Their management will depend not only on scientific monitoring and information, but also on the complicated networks of food production, security, transportation, electricity, political powers, water supply and communication, for example— and on the connections and dependencies between these networks. Risks of large magnitude volcanic events are best conceptualised in the context of networks or webs of interactions between critical infrastructure, institutions, political powers and the Earth system itself.

In the event of a super-eruption, for example, the impacts on global aviation and even shipping would have major impacts on supply chains of both food and technology (see Fig. 2). This would be significantly compounded by poor harvests in regions affected by volcanically-forced climate change. Increased food prices can trigger or exacerbate civil unrest and public health problems, limiting economic growth (e.g. Benson and Clay 2004). Areas and nations less affected by transport restrictions or more self-sufficient in terms of food requirements would be able to adjust to some extent but a severe economic impact on key banks in, for

example, East Asia, would cause liquidity crises in Europe and the United States.

As the eruption continues, or ash fallout across wide areas becomes re-suspended, much of the globe could have to manage repeated airspace closures and trade disruption. Climate impacts could be felt for years after the eruption (e.g. Timmreck et al. 2012), with poor harvests driving the global economy further into crisis and causing conflicts over resources (e.g. Godfray et al. 2010; see also Gassebner et al. 2010). Communication technologies could be badly affected as ashfall damages infrastructure including telecommunications masts, limiting the scope of cooperative risk management across and within national borders. In this scenario, we can only scope out the potential impacts, but several attempts have been made to rationalise such an extreme event (e.g. Denkenberger and Pearce 2014; Rees 2013). Modelling such events is highly complex, not least because it depends on numerous source factors which have large ranges (such as sulfur load, timing, location) as well as on the fragilities and vulnerabilities of the global food system, transport systems and governance systems. On top of this, uncertainty—both scientific and social—has to be taken into account to produce meaningful results. The problem is transdisciplinary because it requires action by experts (scientists, social scientists), governments and other stakeholders (Fig. 1). The uncertainty is therefore likely to be amplified because of the combination of monitoring methods, models and interpretation across different groups.

A further source of uncertainty is the trans-boundary nature of these large magnitude scenarios. Both of these scenarios pose challenges that transcend national boundaries, but will nevertheless be significantly affected by them, as nations differ in how they manage volcanic risk. At present, the management of volcanic risk is primarily the work and responsibility of individual nation states. Institutional frameworks vary considerably between nations (e.g. Donovan and Oppenheimer 2015a), and are not necessarily readily combined. Volcanoes are inevitably sited in particular places, and if other nations are affected by an eruption, they will be dependent at
<figure><img src="image_61.png" /><figcaption>**Fig. 2** Global flight routes (black lines). Also shown are volcanoes listed in the LaMEVE database (Crosweller et al. 2012) and population density (green to red)</figcaption></figure>

least in part on the “host nation” for information. This has been demonstrated in recent eruptions in Iceland (Donovan and Oppenheimer 2012), and also in Ethiopia and Eritrea (where the lack of diplomatic relationships caused problems as well; Yirgu et al. 2014). Information about the eruption of Nabro volcano in Eritrea was primarily sourced from satellite data, demonstrating the importance and significance of recent developments in remote sensing of volcanoes (e.g. Biggs et al. 2014).

An additional challenge of transboundary events is the issue of consistency. Nations may vary in their responses to eruptions and in their willingness to issue evacuation orders. One country may evacuate its citizens from the immediate proximity of the volcano and another may not. In the event of threats to air quality from volcanic emissions, one country may provide free masks and another not. These factors are important because of the potential for the situation to be exacerbated by social unrest as citizens in one state feel less well provided-for than those in another. Hence, such an eruption could reverberate through global social networks, amplifying uncertainties and significantly affecting social stability. There are also spatial differences in vulnerability and exposure: societies

will not be affected equally, and this could create significant challenges for security and for the allocation of resources. The Millennium Declaration, for example, states that “global challenges must be managed in a way that distributes the costs and burdens fairly in accordance with basic principles of equity and social justice” (UN General Assembly 2000, p. 1, paragraph 6). This effectively refers to “risk sharing”: the principle that risk is reduced for those most affected if it is shared with those who are less affected. This would be challenging in the event of an M8 eruption in which there are global impacts, and requires careful planning at an international level prior to the event.

The probability of either of the scenarios in this paper being realised is very low, if it is based on frequency analysis of past events. Frequency-based probabilistic assessments are commonly used in volcanology as “base-rates” (e.g. Mader et al. 2006; Self 2006). However, as a volcanic crisis unfolds, additional information may become available—such as an increase in seismic activity for example. Many volcanologists would argue that this information suggests that there is an increased probability of an eruption—but a frequency-based analysis cannot incorporate this information as it generally
requires higher levels of judgement, and belief-based probabilistic methods may be used (e.g. Bayesian methods, expert elicitation; Marzocchi et al. 2007; Aspinall et al. 2003; Newhall and Pallister 2014). The scenario then becomes a “single event” problem (Gigerenzer 1994). These two scenarios—the longer term risk from large magnitude eruptions and the immediate potential for such an eruption—represent our two time-scales hereafter. Initially, we argue that the longer-term risk from these eruption scenarios requires engagement with policymakers at all levels to ensure that there is awareness of the risk—it has to be on the global agenda as a systemic risk. We then explore some of the implications of this for scientists. Finally we discuss the evolution of a scenario into a single event problem, and the ensuing challenges of communication.

## 3 Systemic Volcanic Risk: Global Communication Structures and Decision-Making Systems

Ultimately, the risks associated with these scenarios are systemic: they occur at the interface between the human and the physical, and require a holistic approach to risk management. According to Renn and Klinke (2004), “A holistic and systemic concept of risk must expand the scope of risk assessment beyond its two classic components: extent of damage and probability of occurrence.” Haldane and May (2011) compare the complex systems of banking to the complexity of ecosystems, for example: there are multiple connections between actors and institutions that are dependent on one another and that transcend scale. Global systemic risk is a direct result of globalisation: it is a networked risk. While networks make risk more manageable in some ways by adding robustness, they can also increase fragility (Beale et al. 2011; Goldin and Vogel 2010), because a break in one part of the network affects the whole network.

The complexity of global networks sits uneasily with the existence of nation states (e.g. Sassen 2006): “bits of territory, authority and

rights” are assembled on multiple scales that transcend the traditional “local to national to global” scalar distinctions. Sassen (2006) argues further that “new types of orderings” are emerging. The global community of volcanologists also exists in this precarious spot between national and global—volcano monitoring scientists work within the institutional structures of governments, yet also participate in a global scientific debate about methods, new interpretations and new data—all of which can feed into their work within a state. This can have the positive effect of adding robustness to risk management within a nation, but can also produce culture clashes between the scientific perception and the local response (e.g. Donovan et al. 2014a, b). Such culture clashes have materialised in connection with outputs from the Intergovernmental Panel on Climate Change (IPCC), for example (e.g. Hulme 2009, 2014), and also in debates in different countries about issues such as genetically-modified crops. The focus in discussions around the IPCC is not merely a result of the evidence and uncertainties, but also a matter of how evidence is presented (Hulme and Mahoney 2010).

Communication of extreme volcanic risk at a global scale is thus immensely complex. It is affected by geography—availability bias, for example, will make some people more readily able to conceive of volcanic impacts than others (Tversky and Kahneman 1974). There are cultural variations not only in the way that risk is perceived, but also in the way that it is managed (e.g. Dake 1992). In the case of extreme volcanic risk that affects multiple nations and cultures, effective communication would have to use a range of media, and would require the involvement of a wide range of actors and institutions with a consistent and culturally sensitive narrative.

### 3.1 Managing Communication

The volcanic ash advisory centres (VAACs) have some experience in communicating transboundary volcanic hazard from ash plumes. They
require governments to monitor their volcanoes and provide information, usually via volcano observatories, when eruptions are imminent or ongoing. Models are run by the VAACs to assess the trajectory of ash clouds and information is provided for use by aviation authorities. It thus addresses a very specific problem with key actors who have some control over operations. However, the systematic allocation of areas of the globe to particular VAACs does ensure that responsibility is clear, and the information is available to those who need it in a straightforward way.

The requirement that there are global systems in place for managing global risks can, however, obfuscate the complexity of the problems at smaller scales. There is, for example, wide variation in the use of colour codes and alert levels between nations (and sometimes within them). This can depend on historical experience and on dominant types of volcanism, for example (e.g. Potter et al. 2014; Fearnley et al. 2012). The use of alert levels is also not very reliable at present (Winson et al. 2014). There are therefore some issues with any potential “global alert level system”, and while there is a global aviation colour code system, it is hazard-specific to ash plumes that might affect aircraft.

The absence of any international mechanisms for volcanic risk assessment and communication is problematic for several reasons, not least because it means that any response will be reactive. Goldin and Vogel (2010) note that many of the “obvious” international decision-making institutions (such as the World Bank and United Nations) “are already overloaded”: they have been stretched beyond their original remits by globalisation. Global governance itself is highly complex and driven by regulation, but it is also in its infancy, and is beset by issues such as the achievement of global democracy. There are also, importantly, much more pressing issues for global governance to deal with than the small possibility of a large magnitude eruption. Volcanologists are familiar with the difficulties of getting governments to act (e.g. Oppenheimer 2011): volcanoes are not that important. Hence there is no mechanism for

international scientific advice in large magnitude events.

Recent work on volcano early warning systems (e.g. Fearnley et al. 2012; Potter et al. 2014; Winson et al. 2014) has demonstrated some of the challenges of applying such systems in practice. Similarly, work on scientific advisory mechanisms has also demonstrated their social complexity (Donovan and Oppenheimer 2015b; see also for example Hulme 2014 on the IPCC). Nevertheless there is a strong argument that mechanisms for providing global warnings about volcanic activity are needed. It is worth noting that the Sendai Framework for Disaster Risk Reduction 2015–2030 called for a greater role for science (including social, economic, engineering, physical and medical sciences) in disaster risk reduction, and this presents an opportunity for the development of international advisory systems that fully integrate expertise from all of these fields, learning from the experiences of similar bodies such as the IPCC.

Rare events require three things from scientific advisors: imagination, flexibility and rapid response. Even where governments have no interest in preparing, scientists can be ready to offer advice: after all, governments will want it quickly when the need arises! In spite of this, there is a need for at least a mechanism for scientific advice during large magnitude eruptions. The model of the Volcanic Disasters Assistance Program is useful here—it gives precedence to local scientists whilst also providing resources (Pallister 2015). A further consideration, however, is the integration of social sciences throughout the processes of risk assessment and communication. Risk communication in an extreme event would require several characteristics: consistency, transparency and reflexivity. Consistency does not mean that the communication should always say the same thing about the risk; it rather means that messages should be internally consistent and clear about what is and is not known. It can be damaging when one group claims to have better information than another. This is therefore aided by transparency about the information itself and how it is being used, as well as about uncertainty. Reflexivity
refers to the subjectivity of those doing the communicating, and how they manage it (Donovan et al. 2014b; see also Alvesson and Sköldberg 2009; Gibbons et al. 1994, for general discussions of reflexivity). This requires a level of personal integrity and self-awareness. It becomes threatened if the communicator has too much emotional investment in the information, for example.

## 3.2 The Nature of Communication

The systemic nature of these risks requires a long-term scientific and social scientific engagement with decision makers in international, regional, national and local institutions (see Fig. 1). Work in risk communication has demonstrated unequivocally that communication links that are established prior to a crisis are critical in facilitating communication during a crisis (e.g. Donovan and Oppenheimer 2012; Marzocchi et al. 2012; Barclay et al. 2008; Bird et al. 2008; Haynes et al. 2008). One key recommendation is therefore that experts ensure that they are in communication with civil protection organisations even when volcanic activity is low. Such contact does not have to be continuous, but it should be relatively regular (for example, a meeting every six months—though this is likely to vary between institutions and circumstances). Meetings might include simulated drills, discussions of earthquake activity and monitoring data over the last few months, updates on response plans and discussion of new results.

Risk communication has different requirements depending on whether one considers high-frequency low impact events or low-frequency high impact events, especially at the extreme event end of the scale. This requires judgement: one of the problems with extreme events that have low probabilities but high impacts is that they can capture scientists' and journalists' imaginations. As Pidgeon and Fischoff (2011) point out, listening is also a form of communication, and so is silence. Govern-

ments have struggled to identify the “right” time to tell populations about extreme risks, and survey respondents generally want to be told but recognise that the issue is ambiguous (e.g. Eiser et al. 2014; Donovan et al. 2014a, b). In general, low probability risks are communicated if the probability increases. Setting a threshold for this can, however, be challenging because of the fear of “false alarms”. Volcanologists have struggled with this balance in the past, and this has fed into studies to find appropriate statistical approaches (e.g. Woo 2008; Aspinall et al. 2003). Successful management depends on the communication not only of risk but of uncertainty. In the presence of high uncertainty, there is no such thing as a false alarm (e.g. Hincks et al. 2014, showed that the evacuations on Guadeloupe in 1976 were justified even though there was no eruption, because there was very high uncertainty). However, high uncertainty regarding a low probability but high impact risk is challenging, and is also a situation in which the precautionary principle can produce paralysis rather than rational decisions (e.g. Sunstein 2005), not least because of the high economic cost of always erring on the side of precaution. With regard to extreme volcanic risk pre-crisis, communication with the public has to be carefully considered and framed. It also has to be transparent: the results of the L’Aquila trial demonstrate the importance of clear and open communication, for example. After the 2009 earthquake, inhabitants felt that they had been misled because they had been explicitly reassured (Alexander 2014), rather than told that the risk was low but not zero.

Framing is a critical aspect of risk communication (e.g. Barclay et al. 2008). A frame is a social construct that allows the interpretation of complex information. Frames can be negotiated through dialogue between all the participants in a conversation to ensure that they are appropriate and effective. It is important not only to state scientific knowledge and uncertainty, but also to engage with the audience. Scientists’ perceptions of the audience are also likely to affect their communication (Donovan et al. 2014a) and must
be handled carefully. This is a subjective process,
but can be rationalised through collaboration and
discussion between physical scientists, social
scientists, policymakers and the public.

4 Single Event Communication

Once volcanic activity is detected and expert
opinion is that the eruption may be very large,
the volcanic risk web has to be “activated”.
Figure 3 is a map of the world showing the
location of tweets with the hashtag #Holuhraun
from 29 August to 2 September 2014 (there was
a small eruption on 29 August, and then the
fissure re-opened from 31 August 2014 to 27
February 2015). It demonstrates the velocity with
which information about volcanic eruptions
travels the web. Secrecy about a potential large
eruption would be very difficult to maintain for
any length of time. Ultimately, the communica-
tion of such risk would be the responsibility of
governments, but it would be strongly dependent
upon relationships between scientists, social
scientists and governments—and the trust that is

placed in them by industry, NGOs and other
stakeholders, including the public.

In Donovan et al. (2012), we introduced a
modified framework for the management of risk in
volcanic crises, based on the Science Studies lit-
erature (Wynne 1992; Stirling 2007). A simplified
version of this is shown in Fig. 4, demonstrating
the transdisciplinary nature of the problem: the
types of question that are generated from such a
systemic risk are multi-dimensional. There are
risks, uncertainties, ambiguities and ignorance
that affect multiple connected groups and entities.

The management of such a situation would
quickly escalate beyond nations, and require
coordination (e.g. by UN institutions). It would
require coherence and clarity about the potential
impacts of the eruption, and about its manage-
ment by different groups in the risk web (e.g.
distinguishing the responsibilities of government
from those of individuals). In this respect, the
communication of risk moves far beyond volca-
nologists—but also requires that volcanologists
retain their integrity as sources of expert infor-
mation. In the next subsection, therefore, we
discuss some of the broad issues that affect

<figure><img src="image_62.png" /><figcaption>**Fig. 3** Tweet map, showing tweets with the hashtag #Holuhraun between 29 August and 2nd September. Colours and size represent the day: *red* 29 August, *orange* 30 August, *yellow* 31st August, *light green* 1 Sept, *dark green* 2 Sept. Note that only tweets from users who disclose their geolocation can be mapped; this amounts to ~2500 tweets, of a total of ~5600</figcaption></figure>

green 2 Sept. Note that only tweets from users who
disclose their geolocation can be mapped; this amounts to
~2500 tweets, of a total of ~5600
<figure><img src="image_63.png" /><figcaption>**Fig. 4** Different aspects of uncertainty around volcanoes, modified from Stirling (2007), Wynne (1992) and Donovan et al. (2012). Each category represents a different aspect of uncertainty that will be represented in each part</figcaption></figure>

of a network, including scientific institutions, infrastructure (transport, energy, agriculture etc), government institutions and different social groups

volcanologists involved in expert advice. This affects both long-term and single event communication: we suggest that the communication of extreme volcanic risk, though conceptually broken into these two aspects, actually depends on their integration. The management of an extreme volcanic event is likely to be dependent upon communication networks that are instituted prior to the detection of activity.

## 4.1 Professionalising Volcanology

Some of the issues that have been raised in this chapter speak directly to IAVCEI's Crisis Protocols (Newhall et al. 1999). Recent events, such as the trial of six seismologists in L'Aquila, Italy (e.g. Marzocchi 2012; Alexander 2014) have led to renewed calls for protocols and guidance for volcanologists who are involved in policy advice (e.g. Aspinall 2011). Volcanology in certain circumstances comes to resemble a formal profession (such as medicine or law; Baxter et al. 2008). In light of social media developments as well as an increasingly litigious world, the importance of individual responsibility cannot be

ignored in the context of global risk. Figure 3, for example, shows that the interest in the Holuhraun eruption was global and not scaled. In Iceland, researchers were asked not to tweet photos of themselves that were inconsistent with doing scientific work: the government was under pressure to allow tourists into the restricted area, which was a flood plain that would be affected rapidly in the event of subglacial eruption. The additional requirement to monitor social media sites may be an important consideration for future planning by volcano monitoring institutions. The interest and availability of information about volcanic activity—without any quality controls—is therefore challenging to manage. Communication technologies such as Twitter and Facebook are double-edged: they can both complicate and aid disaster management. Furthermore, they may require additional resources from responsible institutions in the event of a crisis. Where there is potential for a large magnitude eruption—for example, an unrest episode at a known supervolcano—it is likely that media attention would be significant and that volcanologists around the world might be asked to comment on a volcano about which they know
relatively little. The likely involvement of the global volcanology community in a large magnitude event necessitate a brief consideration of these issues here.

The implications of this for researchers are, ultimately, value-driven: they require reflexive management of subjective tendencies to want to be involved in every volcanic crisis, and careful consideration of comments on social media, following professional guidelines (e.g. from IAVCEI). Awareness that there may be a political context that individuals at a distance cannot see is also important. However, there are also implications for volcano monitoring institutions, particularly concerning the need to monitor social media but also its potential. Bird et al. (2008) demonstrated that the level of information provided by the Icelandic Meteorological Office on its website was appreciated by the public. Donovan and Oppenheimer (2012) found that scientists interviewed in Iceland felt that the availability of data had led to the public becoming, over time, able to use that information effectively. There are considerable advantages to a long-term dialogue with the public that familiarises people with the kinds of information available in a crisis—though there may be disadvantages and understandable insecurities in making data too readily available, not least the potential for misinterpretation (Donovan and Oppenheimer 2015a, b). Again, this issue is magnified in the case of supervolcanoes, as data indicating an increase in activity might cause widespread concern.

A further uncertainty in the present case—large magnitude eruptions—is that the source volcano may not have received much attention, compared with frequently active systems such as Etna. There may well be a trade-off between the involvement of scientists who have experience in policy advice but no local knowledge, and the involvement of, for example, a single local scientist who happened to do their PhD studies on that volcano, but is considerably more familiar with petrological methods than with providing hazard advice. Again, reflexivity is an approach that may aid in this situation.

Comparisons have been made in the past between volcanology and medicine (e.g. Baxter et al. 2008), and the introduction of “evidence-based volcanology” (Aspinall et al. 2003) builds on ideas from the medical literature. One difference is that volcanologists do not take the Hippocratic Oath and are not trained to deal with people or indeed to refer patients to colleagues whose specialties might be more appropriate. The culture of academia in particular is not always conducive to effective delegation or humility, and academics are not trained for the high pressure of responsibility for matters of life and death. The detection of signals that suggest a potentially large magnitude eruption at a previously unstudied volcano would have major impacts on the expectations that the public have of volcanologists, and on the pressure and responsibility faced by experts. Academic training, at present, rarely includes mandatory training in science communication for policy, or indeed in statistics for risk assessment—but volcanology is slowly turning into a profession, and this requires some adjustments in pedagogy.

# 5 Conclusions

This chapter has addressed some of the issues around the communication of extreme volcanic risk. We have demonstrated that such a risk is fundamentally systemic, not local, and it transcends scale. It is a networked risk that can be visualised as a web of connections between governments, institutions, infrastructures, industry, experts and populations, and “grounded” geographically through an as-yet-unspecified volcano. Such an event would reverberate through the risk web, and requires transdisciplinary collaboration. It is therefore important that communication pathways are established prior to any eruption. Communication about extreme volcanic risk prior to the detection of any activity will dictate the nature of communication when activity is detected. It should be characterised by four ideas:
* Appropriate framing: this requires careful consideration of the social context of the scientific information and also the potential impacts that it might have on the population.

* Intersubjective validation: this represents the importance of some level of scientific consensus—peer review—so that messages are clear.

* Dialogue and listening: communication is a two-way process, and this means that concerns from policymakers and populations have to be taken seriously and addressed

* Reflexive adaptation: in a rapidly developing situation, it is important that individual fears, assumptions and anxieties are acknowledged and addressed within the communication process.

These concepts are suggested as a means of structuring discussions between social and physical scientists, policymakers, officials and populations: they require transdisciplinary discussions. In the event of an imminent large-magnitude eruption, there will not be time to build relationships from scratch, nor to debate the appropriate role of different stakeholders and experts. Experts and civil institutions have to work together both to establish relationships and to assess existing communication technologies for their resilience to large magnitude hazards. However, much of this is required at a political level. The management of the high uncertainty in volcanic crises, the communication challenges and the need for engagement over the long term suggest that volcanology is becoming a profession in which agreed standards for practice are required.

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# Part One Summary: Adapting Warnings for Volcanic Hazards

William J. McGuire and Carina J. Fearnley

Of all the geophysical threats, volcanic activity is unique in having a particularly large and diverse portfolio of associated phenomena capable of causing death and injury, societal and economic disruption and damage to population centres and attendant infrastructure. Potentially hazardous phenomena as wide-ranging as ash, noxious gases, lava flows, pyroclastic density currents and tsunamis differ in terms of nature, predictability, scale, extent, impact and perception. As such, a ‘one size fits all’ approach does not provide the most effective means of addressing the communication of volcanic hazards, and while general principles apply, warnings that seek to manage and mitigate the effects of individual hazardous phenomena need to be adapted or tailored.

The chapters that form Part One of this volume demonstrate how this approach may be utilised successfully to tackle a variety of specific hazards, ranging from those that apply in the immediate vicinity of a volcano, notably ballistic ejecta, hydrothermal events, and pyroclastic density currents, to those that have more wide-

spread ramifications, most especially tephra and the manifold consequences of extreme volcanic events.

To date, little consideration has been given to the hazard arising from the ejection of ballistic material from explosive vents, perhaps because the numbers of people exposed tend to be small and death and injury tolls have been limited. As Fitzgerald et al. observes in “The Communication and Risk Management of Volcanic Ballistic Hazards”, casualties of ballistic events are largely restricted to tourists, hikers, locals and volcanologists, who visit and linger in the immediate vicinity of active vents. Nonetheless, notes the author, ballistic ejecta can be hurled to distances of several kilometres from source, and is capable of causing significant damage to property and infrastructure within range. Fitzgerald reviews the current state of thinking on the ballistic hazard and the methodologies used to communicate and manage associated risk, and addresses the potential for developing new tools and management approaches.

Closely linked to ballistic hazard is the general threat to life presented by areas of active hydrothermal activity, principally because explosions at hydrothermal vents often generate ballistic ejecta. The hazards characterising hydrothermal fields are, however, more diverse, and include geysers, fumaroles and pools of boiling mud and water. In “Active Hydrothermal Features as Tourist Attractions”, Erfurt-Cooper highlights the fact that such fields constitute environments, the unpredictability and potential

<footnote>W.J. McGuire
Department of Earth Sciences, UCL Hazard Centre,
University College London,
London WC1E 6BT, UK
e-mail: w.mcguire@ucl.ac.uk</footnote>

<footnote>C.J. Fearnley (✉)
Department of Science and Technology,
University College London, Gower Street,
London WC1E 6BT, UK
e-mail: c.fearnley@ucl.ac.uk</footnote>
hostility of which are rarely fully appreciated by
visitors. This, the author observes, is making the
management of hydrothermal hazards increas-
ingly problematic as tourist numbers increase.
Erfurt-Cooper focuses attention, in particular, on
hydrothermal areas that are also significant
tourist attractions; evaluating potential hazards in
the context of reducing accidents and limiting
injuries to visitors.

The destructive and lethal potential of pyro-
clastic density currents (PDCs) is well known, as
are the issues that make successful mitigation
problematic; high velocities; extreme tempera-
tures; sediment and debris load; and mobility. In
“Mapping Hazard Zones, Rapid Warning
Communication and Understanding
Communities: Primary Ways to Mitigate
Pyroclastic Flow Hazard”, Lavigne et al. dis-
cuss how communication of a hazard that has,
effectively, no warning time, might best be
approached. They note that, given the properties
of PDCs, the only useful approach is a precau-
tionary one centred around building understand-
ing in at-risk communities, hazard zonation, and
rapid and effective warning. Challenges abound,
however, which Lavigne and his colleagues
analyse, concluding that efficient dissemination
of information and an improved understanding of
how at-risk communities are likely to respond,
are key to mitigating the effects of PDCs on
populated areas close to active volcanoes.

Volcanic ash and gases provide the means
whereby the reach of an erupting volcano may be
extended over many thousands of square kilo-
metres and, in the most extreme cases, across the
globe. The communication demands of such
spatially extensive hazards are very different
from those relating to hazards confined to a
volcano and its immediate environs. As Stewart
et al., note in “Communication Demands of
Volcanic Ashfall Events”, forecasting when,
where and how much ash will fall during an
eruption, constitutes a major challenge that
requires a suite of communication strategies
rather than a single solution. Stewart and her
co-authors examine the factors that contribute to
the complex ‘communication environment’ that
characterises ashfall hazard and review the

various communication tools and methodologies
available across a range of sectors, including
public health, agriculture and critical infrastruc-
ture. They also highlight the peculiar challenges
presented by long duration, ash-producing,
eruptions, and during the clean-up and recovery
following ashfall events.

The major threat that widespread clouds of
volcanic ash present to the aviation industry, has
been highlighted in the last six years by disrup-
tive eruptions at Eyjafjallajökull (2010) and
Grimsvötn (2011)—both in Iceland—and the
Chilean volcanoes, Puyehue-cordón Caulle
(2011) and Calbuco (2011). In addition, there
have been numerous examples of encounters
between individual aircraft and ash clouds in the
vicinity of erupting volcanoes that are close to
flight paths. In “Volcanic Ash and Aviation—
The Challenges of Real-Time, Global
Communication of a Natural Hazard”, Peter
Lechner et al., focus on the range of issues that
arise due to interactions between ash and aircraft,
noting that informing aircraft in-flight of the
exact distribution of potentially dangerous ash
clouds in the vicinity remains a challenge. The
authors present a picture of how the aviation
industry currently deals with ash clouds, within
the framework of the International Airways
Volcano Watch (IAWV), observing that man-
agement of ash cloud events has improved con-
siderably since the 1980s. Lechner and his
co-authors highlight the import role interna-
tional collaboration has played in developing a
global warning system, but recognise that there is
still work to do, notably in improving commu-
nication prior to, and at the onset of, an
ash-producing event.

In the manner of ash, volcanic gases can have
serious consequences close to a volcano, but also
half a world away. As Edmonds et al., note in
“Volcanic Gases: Silent Killers”, proximally, the
effects may include asphyxiation, respiratory dis-
eases and skin burns while, further afield, wide-
spread famine may result from the
climate-modifying ramifications of sulphate aero-
sols injected into the stratosphere. The authors
identify a number of key challenges related to
tackling the volcanic gas threat, notably difficulties
in monitoring gas concentrations and communi-
cating the results to those who need to know, and
improving understanding of the gas risk amongst
at-risk populations. Edmonds and her colleagues
examine a range of scenarios, including carbon
dioxide release from lake overturn events and the
large-scale loading of the troposphere and strato-
sphere with volcanic sulphate. In the latter context,
there is a particular focus on the 1783 Laki (Ice-
land) eruption, and its impact on climate and
health across the UK and Europe, and how a
future eruption of this type might be managed.

It seems fitting that, in the final chapter of Part
One, "*Imagining the Unimaginable: Communicating Extreme Volcanic Risk*" Donovan and Oppenheimer consider how we might tackle an eruption large enough to qualify as a global geophysical event. Such eruptions recognise no boundaries and have the potential to impact in some way upon many, if not all, nation

states. As such, the problems of communicating
the associated hazards are unique. Donovan and
Oppenheimer focus on communication both prior
to and during such an eruption. While noting that
no volcano erupts on such a scale without
warning signs, the authors caution that great
uncertainties in likelihood, timing, nature and
magnitude of extreme volcanic events would,
nonetheless, provide a major challenge to effec-
tive communication of the hazard and risk, as
would problems arising in seeking to provide
clear messages beyond the borders of the country
that hosts the volcano. Donovan and Oppen-
heimer also highlight the need to ensure that
communication strategies developed prior to the
start of the eruption are robust enough to survive
through the course of the eruptive event, so as to
provide for reporting of the status of the eruption,
the degree and nature of damage and disruption,
and any logistical requirements.

**Open Access** This chapter is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, a link is provided to the Creative Commons license and indicate if changes were made.

The images or other third party material in this chapter
are included in the chapter's Creative Commons license,
unless indicated otherwise in a credit line to the material.
If material is not included in the chapter's Creative
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by statutory regulation or exceeds the permitted use, you
will need to obtain permission directly from the copyright
holder.
Part Two

Observing Volcanic Crises

Gill Jolly and Carina J. Fearnley
Volcanic Unrest and Hazard
Communication in Long Valley
Volcanic Region, California

David P. Hill, Margaret T. Mangan
and Stephen R. McNutt

Abstract

The onset of volcanic unrest in Long Valley Caldera, California, in 1980 and the subsequent fluctuations in unrest levels through May 2016 illustrate: (1) the evolving relations between scientists monitoring the unrest and studying the underlying tectonic/magmatic processes and their implications for geologic hazards, and (2) the challenges in communicating the significance of the hazards to the public and civil authorities in a mountain resort setting. Circumstances special to this case include (1) the sensitivity of an isolated resort area to media hype of potential high-impact volcanic and earthquake hazards and its impact on potential recreational visitors and the local economy, (2) a small permanent population (~8000), which facilitates face-to-face communication between scientists monitoring the hazard, civil authorities, and the public, and (3) the relatively frequent turnover of people in positions of civil authority, which requires a continuing education effort on the nature of caldera unrest and related hazards. Because of delays associated with communication protocols between the State and Federal governments during the onset of unrest, local civil authorities and the public first learned that the U.S. Geological Survey was about to release a notice of potential volcanic hazards associated with earthquake activity and 25-cm uplift of the resurgent dome in the center of the caldera through an article in the Los Angeles Times published in May 1982. The immediate reaction was outrage and denial. Gradual acceptance that the hazard was real required over a decade of frequent meetings between scientists and civil authorities together with

<footnote>D.P. Hill (✉) · M.T. Mangan
U.S. Geological Survey, California Volcano Observatory, Menlo Park, CA 94025, USA
e-mail: hill@usgs.gov</footnote>

<footnote>S.R. McNutt
School of Geosciences, University of South Florida,
Tampa, FL 33620, USA</footnote>
public presentations underscored by frequently felt earthquakes and the onset of magmatic CO₂ emissions in 1990 following a 11-month long earthquake swarm beneath Mammoth Mountain on the southwest rim of the caldera. Four fatalities, one on 24 May 1998 and three on 6 April 2006, underscored the hazard posed by the CO₂ emissions. Initial response plans developed by county and state agencies in response to the volcanic unrest began with “The Mono County Volcano Contingency Plan” and “Plan Caldera” by the California Office of Emergency Services in 1982–84. They subsequently became integrated in the regularly updated County Emergency Operation Plan. The alert level system employed by the USGS also evolved from the three-level “Notice-Watch-Warning” system of the early 1980s through a five level color-code to the current “Normal-Advisory-Watch-Warning” ground-based system in conjunction with the international 4-level aviation color-code for volcanic ash hazards. Field trips led by the scientists proved to be a particularly effective means of acquainting local residents and officials with the geologically active environment in which they reside. Relative caldera quiescence from 2000 through 2011 required continued efforts to remind an evolving population that the hazards posed by the 1980–2000 unrest persisted. Renewed uplift of the resurgent dome from 2011 to 2014 was accompanied by an increase in low-level earthquake activity in the caldera and beneath Mammoth Mountain and continues through May 2016. As unrest levels continue to wax and wane, so will the communication challenges.

# 1 Geologic Setting and Background

Long Valley caldera is a 15- by 30-km oval-shaped topographic depression located midway between Mono Lake and the town of Bishop in east-central California (Fig. 1). It is nestled against the western escarpment of the large graben formed by the Sierra Nevada on the west and the White Mountains on the east. This impressive eastern Sierra landscape has developed over the past three million years as a result of repeated slip on the range-front normal faults and persistent volcanism. The dominant volcanic event in the area was the massive eruption of the Bishop Tuff during the collapse of Long Valley caldera 760,000 years ago. This caldera-forming eruption spewed some 600 km³ of rhyolitic ash across much of the western United States. Frequent, smaller eruptions have continued within the caldera and along the adjacent Mono-Inyo

volcanic chain right up to the recent past, the most recent of which was a small eruption from the north side of Paoha Island in the middle of Mono Lake some 250 years ago (Bailey 2004; Hildreth 2004).

From a purely scientific viewpoint, the Long Valley Caldera-Mono Craters volcanic field is a natural laboratory for studying the interaction between active tectonic and magmatic processes in a transtensional continental regime. In the presence of people and their societal accom- trements, however, active geologic processes pose geologic hazards. The earthquake hazard in this area is emphasized by range-front faults with Holocene offsets (Chen et al. 2014), the great, (M<sub>W</sub> ~ 7.8) Owens Valley earthquake of 1872, together with the series of M > 7 earthquakes this century that ruptured much the Eastern California-Central Nevada Seismic Belt (Wal- lace 1981). The volcanic hazard is reflected in the recurrence of small to moderate volcanic
<figure><img src="image_64.png" /><figcaption>**Fig. 1** Shaded relief map showing regional setting of Long Valley Caldera (LVC) along the eastern escarpment of the Sierra Nevada with $M \ge 6$ earthquake epicenters (yellow circles for 1880–1977 and orange circles for 1978–2014) and $M \ge 5$ earthquake epicenters for 1978–2014 (small orange circles) where numbers are last two</figcaption></figure>

digits of the year. *Black lines* are faults with Holocene offset, *red lines* are faults with offsets in the last 200 years. Note the surface rupture of the M 7.8, 1872 Owens Valley earthquake, which was dominantly right-lateral, strike-slip. Updated from Fig. 3 in Hill (2006) (courtesy of The Geological Society, London)
eruptions along the Mono-Inyo volcanic chain over the past 50,000 years. Over the past 5000 years, for example, some 20 small to moderate eruptions have occurred from vents scattered along the Mono-Inyo volcanic chain at intervals of 200–700 years. Most were explosive, rhyolitic eruptions accompanied by ash clouds and occasional pyroclastic flows; a few were effusive basaltic eruptions. On the basis of this 5000-year record, the background (unconditional) probability of an eruption from somewhere along the Mono-Inyo chain is roughly 0.5% per year. For perspective, this is comparable to the probability of a M ~ 8 earthquake along the San Andreas fault or an eruption from some of the major Cascade volcanoes. It is thus typical of the background probability for geologic hazards throughout much of the active margin of the North American Plate. The particular challenge in the case of Long Valley caldera lies in (1) making a meaningful assessment of the probability gain (conditional probability) for an eruption as this large magmatic complex displays varying levels of seismicity, ground deformation, and magmatic gas

emissions, and (2) effectively communicating this and associated uncertainties to civil authorities, the public, and the media. The problem is one of reliable eruption forecasting and real-time, probabilistic hazard assessment.

Eastern California is an important recreation area heavily used by much of urban California as well as visitors from elsewhere in the country and the world. Mammoth Mountain volcano, which last erupted ~55,000 ybp, stands on the southwestern rim of Long Valley caldera (Hilbreth et al. 2014). It hosts one of the largest ski areas in the country. The resort town of Mammoth Lakes at the base of Mammoth Mountain sits within the southwestern corner of the caldera (Figs. 2 and 3). Mammoth Lakes, with a permanent population of ~8000 and a temporary population that swells to over 40,000 during major ski weekends, is a year-round, destination resort providing ready access to the adjacent high Sierra as well as mountain biking, fishing, and golf during summer months. This does not mix easily with talk of geologic hazards, particularly high-profile hazards posed by volcanoes and earthquakes (Hill 1998).

<figure><img src="image_65.png" /><figcaption>**Fig. 2** Photographic views across Long Valley Caldera. **a** View to NE across Long Valley Caldera from Lake Mary Rd on the SE flank of Mammoth Mountain (taken from point “A” in photo **b**). Mammoth Lakes is in the middle-left foreground, the resurgent dome in the middle distance and the South moat to the right. Glass Mountain forming the NE rim of the caldera in on the horizon behind the resurgent dome (USGS photo). **b** View from</figcaption></figure>

<figure><img src="image_66.png" /></figure>

the resurgent dome westward to Mammoth Mountain (taken from point “B” in photo **a**). The 40 MW geothermal plant is in the foreground, Hwy 395 cuts across the middle distance, and Hwy 203 extends toward Mammoth Lakes at the base of Mammoth Mountain. High peaks of the Sierra Nevada form the distant horizon to the right of Mammoth Mountain (USGS photo)
## 2 Hazard Communication (and Miscommunication) During Two Decades of Strong Volcanic Unrest (1978–2000)

A $M_L = 5.8$ earthquake on October 4, 1978, located beneath Wheeler Crest 14 km southeast of Long Valley caldera (roughly midway between Bishop and Mammoth Lakes) marked the onset of the extended episode of unrest in the caldera and vicinity that continues today (Figs. 3 and 4; Hill 2006; Shelly and Hill 2011; Lewicki et al. 2014). Over the following year and a half, seismic activity in the form of $M > 3$ and occasional $M > 4$ earthquakes

gradually migrated northwestward and the southern margin of the caldera. Then, on May 25, 1980, just seven days after the catastrophic eruption of Mount St. Helens, three $M \sim 6$ earthquakes shook the southern margin of the caldera accompanied by a rich aftershock sequence. By the morning of May 27, the Director of the U.S. Geological Survey (USGS) had released a formal “Hazard Watch” (Table 2a) noting the possibility of additional $M \sim 6$ earthquakes in the area. Just hours later, a fourth $M \sim 6$ earthquake shook the area—a successful “short-term” forecast!

That summer, Savage and Clark (1982) re-leveled a section of Highway 395 through the

<figure><img src="image_67.png" /></figure>

**Fig. 3** Map of epicenters for earthquakes with magnitudes $1.5 \ge M \le 6.5$ from 1987 to 2014 scaled by symbol size. Epicenters for the 1978–1983 interval (prior to installation of the locally dense seismic network in 1984) are from the standard NCSN catalog and include

only $M \ge 3$ earthquakes. Epicenters for $M \ge 1$ earthquakes the 1984–2014 interval are from the double-difference catalog of Waldhauser (2009). *ML* indicates the town of Mammoth Lakes. Background shaded relief and seismicity thanks to Stuart Wilkinson
area affected to document the co-seismic displacement expected from this series of four M ~ 6 earthquakes. What they found instead, was a broad, dome-shaped uplift of the caldera floor (the resurgent dome). Monuments near the center of the resurgent dome were 25 cm higher in the summer of 1980 than they had been in 1975. Measurements of a trilateration network spanning the area made in 1979 suggested that most, if not all of this deformation developed sometime between the summer of 1979 and the summer of 1980. With fresh images of Mount St. Helens in mind, it required no great leap to recognize a volcanic signature in this combination of strong earthquake swarm activity and ground deformation. Still, if the activity had died away as with most aftershock sequences, attention would have soon focused elsewhere.

Earthquake activity continued, however, with frequent swarms that included locally felt earthquakes (M ~ 3–5 events), rapid-fire bursts of small earthquakes (spasmodic bursts), which are often associated with active volcanoes, and evidence that focal depths appeared to be getting shallower with time (Ryall and Ryall 1983). Roy Bailey of the USGS, who produced the Long Valley Caldera geologic map (Bailey 1989) and was Volcano Hazards Program Coordinator, had initial responsibility for communicating the significance of this activity to local authorities. In discussions between scientists in the USGS, the California Division of Mines and Geology (CDMG), and Alan Ryall at the University of Nevada, Reno over the winter of 1981 and a meeting in early May 1982, a consensus developed that we had an obligation to inform local civil authorities of our concerns about the volcanic nature of this activity. The result was a memo to the Chief Geologist in USGS headquarters dated May 17 recommending a volcanic Hazard Watch (the middle level of the three-level hazard terminology in use by the USGS at the time; see Table 2a). Hazard notification was top-down at the time, passing from the Federal government (USGS) to the State of California Governer’s Office of Emergency Services (CalOES) and from there, on to the counties and cities affected. A dialogue between USGS

headquarters and CalOES on the precise wording of the alert ensued. Meanwhile, a science reporter for the Los Angeles Times got wind that something was up. An article announcing that the USGS was about to release a “Notice of Potential Volcanic Hazards” appeared in the Los Angeles Times on the morning of May 25, 1982, just two days before the Memorial Day weekend and short circuiting the official release of the “Notice of Potential Volcanic Hazards” (the lowest level in the Notice/Watch/Warning hazard terminology) scheduled for the next day: The local response was one of outrage, anger, and disbelief (what volcano?!) exacerbated by inflammatory headlines and news stories about “brewing lava eruptions” and a town in denial. Geologists, and USGS geologists in particular, immediately became persona non grata in Mammoth Lakes and Mono County—an attitude that only gradually mellowed over the years. Under the best of circumstances, communicating information on a newly recognized hazard is tricky—this serves as an outstanding example of the wrong way to start such a dialogue.

Roy Bailey, Coordinator of the Volcano Hazards Program, oversaw USGS monitoring efforts in the caldera through the summer and fall. In December 1982 the USGS instituted the Long Valley Monitoring Project with David Hill as Chief Scientist in charge of coordinating research, monitoring, and hazard communication efforts in Long Valley Caldera. The California Division of Mines and Geology (CDMG) assumed a comparable responsibility in 1982, and purchased an automatic earthquake recording system and eventually hired a volcano seismologist, Stephen McNutt in spring 1984. In an effort to clarify the significance of the Notice of Potential Volcanic Hazards, Miller et al. (1982) published USGS circular 877 describing the nature of the potential hazards from future volcanic eruptions, and CDMG prepared a series of eruption scenarios as the basis for response planning. These documents together with the persistence of ongoing unrest stimulated disaster preparedness efforts by State, County, and Federal land management agencies in the area that included establishing Incident Command