<figure><img src="image_29.png" /><figcaption>**Fig. 3** IAVW system elements and relationships</figcaption></figure>

organisations, local and national authorities, and
communities that live around volcanoes. Rela-
tionships between VAACs and Meteorological
Watch Offices are similarly long-term and strong,
given that many observatories run weather sta-
tions and have strong links with local meteorol-
ogists due to the need to forecast rain-induced
lahars (volcanic mud flows), volcanic ash, and
gas dispersal. The ascent of magma towards the
Earth's surface before an eruption typically
generates physical signals that can be detected if
appropriate volcano monitoring is in place,
thereby allowing eruption forecasting and early
warning. Pre-eruptive signals (volcanic unrest)
may be detected using a variety of methods,
including, but not limited to: volcanic earthquake
monitoring using seismometers, ground

deformation measurements and observations of
hydrologic activity change, gas emissions change
monitoring, and steam explosion observations.

The status activity of a volcano is best com-
municated in a succinct manner to inform deci-
sion makers. To assist with this, the international
aviation community has established a four-level
colour code chart for quick reference to indicate
the general state of a given volcano (Table 1).
The colour code identifies the state of the volcano
(i.e. unrest vs. eruption) but is not intended to
represent the status of distal ash in the atmosphere
(Guffanti and Miller 2013) or to represent risk to
aviation or to people and assets on the ground.

While the international community has
developed the colour-code system, it should be
noted that, for various reasons, these codes are
<table><caption>**Table 1** ICAO Aviation Colour-Code</caption><thead><tr><td>Colour-code</td><td>Status of volcano activity</td></tr></thead><tbody><tr><td>GREEN</td><td>Volcano is in normal, non-eruptive state, or, after a change from a higher alert level: Volcanic activity considered to have ceased, and volcano reverted to its normal, non-eruptive state.</td></tr><tr><td>YELLOW</td><td>Volcano is experiencing signs of elevated unrest above known background levels or, after a change from higher alert level: Volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.</td></tr><tr><td>ORANGE</td><td>Volcano is exhibiting heightened unrest with increased likelihood of eruption or, Volcanic eruption is underway with no or minor ash emission [specify ash-plume height if possible].</td></tr><tr><td>RED</td><td>Eruption is forecasted to be imminent with significant emission of ash into the atmosphere likely, or, Eruption is underway with significant emission of ash into the atmosphere [specify ash-plume height if possible].</td></tr></tbody></table>

not assigned to all volcanoes. While an international standard, the colour code is currently only formally used by the United States, Russia, New Zealand, and Iceland. The reasons for this vary, but most States not using the colour code indicate difficulties in using international systems in parallel with their own locally accepted and appropriate alert levels for ground hazards. It is also recognised that different colours are associated with adverse situations in different cultures and ethnicities.

In 2008, the IAVW Operations Group introduced a new message format to assist volcanologists in the timely provision of information on the state of a volcano to support the issue of volcanic ash advisories by VAACs, the issue of SIGMET information by Meteorological Watch Offices, and the issue of NOTAM for volcanic ash by Air Traffic (Control) Services. This especially formatted message is referred to as Volcano Observatory Notice for Aviation or VONA (International Civil Aviation Organization 2014a, b). The VONA (or something similar based on discussion and agreement on a case by case basis between the specific agencies involved) is expected to be issued by an observatory when the aviation colour code changes (up or down) or within a colour code level when an ash producing event or other significant change in volcanic behaviour occurs. Two-way discussions are essential between volcano observatories and aviation information providers about the observations and information needed during eruption, formats required, challenges and

limitations, as well as an explanation as to how the information will be used and who will receive outputs. For example, the Icelandic Met Office (Iceland's volcano observatory) and the UK Met Office (through the London VAAC) have established a specific format co-designed to suit volcano observatory operating capacities, VAAC needs, and reflect joint experience (Webster et al. 2012). The VONA is a good starting point for such discussions.

## 4 The Challenges

Introducing and continually improving high technology systems to mitigate safety and economic risk from natural events inevitably bring great challenges. For the volcanic risk to aviation these challenges include the detection of volcanic ash cloud, forecasting its dispersion, and the timely and targeted communication of this information, along with system improvement that is well informed by developing scientific understanding.

### 4.1 Ash-Cloud Detection and Forecasts

Today's volcanic ash cloud forecasts, provided by the VAACs, are basic textual and graphical information produced using the output from atmospheric dispersion and transport models. Most of the numerical ash dispersal forecast models utilised by VAACs comprise a
Meteorological model including wind speed and direction, into which volcanic ash is introduced specifying input parameters related to the volcanic source (Eruption Source Parameters). Eruption Source Parameters may include vent location, plume height, eruption duration or start/stop time, mass eruption rate, particle size distribution, vertical distribution of mass with height above the vent and distal fine ash fraction (Mastin et al. 2009). Uncertainty in any of the various source parameters can result in large errors in the resultant volcanic ash cloud forecasts (Webster et al. 2012). Sensitivity analysis can identify the most critical parameters and demonstrate the range of outcomes under different conditions of uncertainty.

Meteorological forecasters evaluate the model outputs before issuing and during the validity of VAA messages. That analysis includes real-time verification of the ash cloud model output against a range of observational resources, principally remote sensing by satellite but also including reports from aircraft and increasingly ground-based sensing such as LIDAR. Post-eruption, model predictions in the distal environment can be compared with observational datasets to examine overall model performance (e.g. Webster et al. 2012).

The current two primary volcanic ash forecast products are the VAA and the SIGMET. The VAACs provide VAA in a text and graphic-based format (VAG) that sets out an analysis of the current position of the ash cloud, and a six, 12 and 18-h forecast location of the ash cloud, setting out position, altitude and thickness using aviation flight level nomenclature. Work has been undertaken informally at each VAAC to provide forecast location of ash cloud out to 24 h. This may become a standard time-step in the future. Meteorological Watch Offices issue volcanic ash cloud SIGMETs based on the guidance provided by the associated VAAC in their respective VAA and VAG products. These SIGMETs are valid for up to 6 h and describe the current and expected location of the ash cloud within the Flight Information Region or area of responsibility of the Meteorological Watch Offices.

As a supplementary service, at time of writing, the European and North Atlantic regions use forecast ash cloud concentration charts issued alongside official VAAC products. Such charts, depicting forecast ash concentration were first provided to users in April 2010 in response to the Eyjafjallajökull volcanic event. It is important to note that there are currently no globally agreed standards and procedures for the production, provision, and use of concentration charts (Gufanti and Tupper 2015).

## 4.2 Communications

In elementary terms, the IAVW system is required to provide volcanic ash cloud information to airline operators and Air Traffic Management system providers who then pass the information to airline dispatchers and pilots. Figure 3 depicts the information flow following a volcanic eruption and identifies participants in the provision of volcanic ash cloud information.

In practice, and despite some excellent initiatives to improve it, communication can fail at any stage. For many significant aviation encounters, aircraft crew members had no knowledge of the eruption encountered despite it being evident to people on the ground—this was the case recently with an aircraft experiencing a damaging encounter with ash from Kelut, Indonesia, 6 h after the 13 February 2014 eruption (airline sources, unpublished communication, 2014). The worst known example occurred in 1991 when there were at-least sixteen in-flight encounters with volcanic ash from Pinatubo, in the Philippines. These encounters occurred despite extensive information being available. Casadevall et al. (1996) noted that the response within the Philippines was relatively effective, but the international response was not, as summarised:

> ...information and warnings about the hazard of volcanic ash either did not reach appropriate officials in time to prevent these encounters or that those pilots, dispatchers, and air traffic controllers who received this information were not sufficiently educated about the volcanic ash hazard to know what steps to take to avoid ash clouds... the key to
communicating information about volcanic eruptions in a timely and readily understandable form is to involve all interested groups (geologists, meteorologists, pilots, and air traffic controllers) in the development of information and to streamline the distribution of this information between essential parties....

Other documented examples include the Manam eruptions during 2004–05 in Papua New Guinea where a large number of pilot reports of volcanic activity collected in flight were not passed on outside the airline involved, regardless of international requirements (Tupper et al. 2007a, b). Conversations with the air traffic management community have also indicated that air traffic controllers are often too busy to pass on messages that they believe have a lower priority than managing the separation of aircraft (Tupper, personal communication, 2014).

When communications are working well, initial reports of volcanic ash can result in useful information being delivered to the end user. In most cases, information about a volcanic ash cloud will be provided to the pilot, either in flight, or during pre-flight planning, in the form of SIGMETs, NOTAMs, reports from pilots, or VAA/VAG. Each of these products is distinct in format and content, but all can provide information regarding the location of volcanic ash cloud. It is critically evident that all of these

products must be consistent in their overall message. When the situation is changing rapidly, that can be extremely challenging.

The 18 August 2000 eruption of Miyakejima, Japan, illustrated this point (Tupper 2012). At least four non-Japanese aircraft encountered the cloud, with two sustaining significant damage. The eruption was sudden, but there was very strong awareness amongst domestic and some foreign airlines of the potential for activity at the volcano. The eruption was well observed, and the speed of response by Japanese authorities was exceptional. Nevertheless, there were some minor communication issues at several stages in the warning chain, resulting in inconsistencies in the information available, particularly during the rapidly developing early stages of the eruption.

To illustrate the potential differences of estimated volcanic ash cloud height in various real-time warnings, Fig. 4 sets out the ash cloud heights stated in VAA, SIGMET, and NOTAM, with respect to their issue time and validity, against the post eruption evaluation of the approximate real volcanic ash cloud height for the 2000 Miyakejima event. The times and approximate altitudes of four confirmed aircraft encounters with the cloud are shown. During the critical first half hour of the eruption, the VAA and then consequent warnings responded to

<figure><img src="image_30.png" /><figcaption>**Fig. 4** Schematic showing volcanic ash cloud height as set out in various real-time warnings along with approximate real ash cloud height for the 2000 Miyakejima event, over approximate time after eruption. After Tupper et al. (2004)</figcaption></figure>
multiple, and in some cases time-lagged observations and information loops. The two early encounters occurred before a concurrent height of the eruption was reflected in the warnings. The actual warning response was relatively good for this eruption, but the schematic illustrates the complexity of messaging, in a fast changing environment, particularly with multiple warning types.

Getting the official communication for warnings right can be made easier, but can also be complicated by non-official communications. In recent years, the rise of social media, enhanced remote communications, and omnipresent digital photography has meant that unofficial eruption and hazard notifications have become almost expected. Operational centres can and do use this to their advantage, particularly for early alerting. However observers can be mistaken—for example during the eruption at Bardarbunga Iceland in 2014 there were *Twitter* reports of an eruption ash cloud based on web cam pictures but it was in fact a dust storm from a nearby sandur plain. Another downside is the amount of ‘chatter’ and the potential for conflicting messaging. Nevertheless, the necessity for public engagement during an event has also risen. The relative level of safety risk of events is also not necessarily reflected in the attention that particular eruptions get in public.

As a result of the avalanche of non-official communications during volcanic events, VAACs and Meteorological Watch Offices endeavour to authenticate all incoming information to establish the reliability and weighting of such information. For example, in 2010, earth scientists and atmospheric scientists in Iceland and the UK enhanced their relationships in a number of ways, including through visits between operational institutions (VAAC at the UK Met Office and Iceland's volcano observatory, the Icelandic Met Office) to better understand processes and working practices used by the other organisation. In parallel, civil protection authorities in the UK sought information and advice about impacts to the UK through UK national research institutions, who in turn consulted Icelandic scientists including the Icelandic Met Office.

In order to support both aviation and civil protection sectors and to facilitate strategic science, a memorandum of understanding was

established between the UK and Iceland to facilitate the flow of information between nations, and to enable wider management of the impacts of cross-border hazards and co-ordination of distal observations of volcanic ash cloud. This memorandum of understanding now underpins long-term productive cross-disciplinary research and relationships. The Icelandic Met Office with the National Commissioner of Icelandic Police (Iceland's Civil Protection) continue to make a great deal of data and information available in close to real time during volcanic unrest and eruptions (including that on social media) to enhance communication across sectors.

## 4.3 Science Challenges

Operational enhancements will continue to need wide scientific development work and expansion of the understanding of the full volcanic ash hazard and risk to aviation.

The central theme of scientific concern is how to accurately determine the constituents (solid particles, gases, and aerosols), density, and three-dimensional shape of a volcanic cloud at particular times and locations. Understanding engine and airframe tolerances to ash ingestion and gas effects will better inform the operational risk management of airlines.

Reducing uncertainties in ash reporting and plume modelling is expected to eventually provide critical warning system enhancements in the future.

During volcanic eruptions, a number of toxic gases may be emitted in addition to ash; these include sulphur dioxide (SO₂), hydrogen fluoride (HF), and hydrogen sulphide (H₂S) amongst many others. Each of these gases has different atmospheric dispersion properties, and so gas clouds may be found coincident or separate from volcanic ash clouds. Of these gases, SO₂ is of particular importance as it may be emitted in large quantities and potentially has significant health effects, as well as longer term effects on aircraft. Further engineering and science work is needed to fully understand this area and reflect any advances in the IAVW system.

In pursuing these objectives the aviation community has been well supported for many years by
the science community, including the World Meteorological Organization and the International Union of Geodesy and Geophysics, member associations, and many dedicated individuals.

Particular support in contributing to and co-ordinating these scientific endeavours in support of the ICAO IAVW will continue to be provided by the WMO Sponsored Volcanic Ash Advisory Group and VAAC Best Practices workshops. Supplementing this, the periodic WMO sponsored volcanic ash science meeting is expected to provide the academic forum for reporting of developments and scientific collaboration.

In supporting this growing area of work, future science investment will be essential to continue developing the IAVW.

## 5 Warning System Enhancements

The eruption of Iceland's Eyjafjallajökull volcano during March to May 2010 demonstrated again the vulnerability of aviation to volcanic eruptions. According to an analysis by Oxford Economics (2015), more than 100,000 commercial flights were cancelled during the Eyjafjallajökull volcano eruptive phase, and US $4.7 billion in global GDP was lost. The report estimated the gross loss to airlines worldwide at US$2.6 billion due to this single volcanic event.

Later, in 2010 and in response to the Eyjafjallajökull episode (International Civil Aviation

Organization 2013a), ICAO established an International Volcanic Ash Task Force as a multidisciplinary global group to further develop and co-ordinate work related to volcanic ash. Before it concluded its work in 2012, it addressed issues related to air traffic management, aircraft airworthiness, aeronautical meteorology, and volcanological and atmospheric sciences. The Task Force identified further work to be undertaken, by existing bodies such as the IAVW Operations Group and collaborative best practice development amongst the nine VAACs, co-ordinated by the WMO (Guffanti and Tupper 2015).

Also of significance, over the last decade ICAO has gradually developed and begun implementing a Global Air Navigation Plan (ICAO 2013b Doc 9750, 2013–2028) as an overarching air navigation framework, including key civil aviation policy principles to assist regions and States with the preparation of their Regional and State air navigation plans.

The objective of the Global Air Navigation Plan is to increase airspace capacity and improve efficiency of the global civil aviation system while improving, or at least maintaining safety. The Plan includes an upgrade framework, and guidelines for associated technology development covering communications, surveillance, navigation, information management, meteorology and avionics.

The Plan reflects all of the science, communications and operational recommendations of the International Volcanic Ash Task Force 4th

<table><caption>**Table 2** Enhancement of Volcanic Ash Risk Mitigation—Excerpts from the ICAO Global Air Navigation Plan (Abridged) with supporting and progress commentary</caption><thead><tr><th>Global air navigation plan module</th><th>Commentary</th><th>Progress</th></tr></thead><tbody><tr><td colspan="3"><em>Completion by 2018</em></td></tr><tr><td>Implement widely collaborative processes</td><td>Acceptable developments should take into account the needs of all directly involved</td><td>Common views have been established on the collaborative treatment of volcanic ash cloud extending across different Flight Information Regions and VAAC areas</td></tr><tr><td>Increase the provision of Volcano Observatory Notices to Aviation</td><td>Not all State Volcano Observatories are issuing VONA</td><td>State Volcano Observatories have been encouraged to issue the VONA. The number of States doing so is increasing</td></tr><tr><td>Develop information confidence levels</td><td>This work responds to a request from the International Air Transport Association (IATA)</td><td>VAAC provider States are actively developing confidence level concepts from both a science and operational standpoint</td></tr></tbody></table>

(continued)
<table><caption>**Table 2 (continued)**</caption><thead><tr><th>Global air navigation plan module</th><th>Commentary</th><th>Progress</th></tr></thead><tbody><tr><td colspan="3"><strong>Completion by 2023</strong></td></tr><tr><td>Enhance the provision of SIGMETs</td><td>A large volcanic ash cloud over congested, multi-State areas can result in multiple SIGMET information messages, all being in effect at the same time</td><td>Work is underway better support MWO responsibilities to issue SIGMET<br>Work is also underway to develop a regional approach to the issue of SIGMET</td></tr><tr><td>Transition to all-digital format</td><td>Volcanic cloud information needs to be provided in a digital form to support ingestion directly into flight planning and flight management systems</td><td>A large area of work is under way as part of the ICAO Meteorology Panel set of projects to support the development of data-centric meteorological information in GML/XML form</td></tr><tr><td>Increase Volcanic Advisory message frequency and time steps</td><td>Operators need frequent updates of volcanic ash information especially in congested airspace and around constrained airports</td><td>Dynamic provision of forecast data is being considered as part of the overall move to data-centric meteorological products</td></tr><tr><td>Continued improvements in observing networks</td><td>Reliable and granular observation of meteorological phenomena including volcanic ash is pivotal in improving forecast products</td><td>The expansion of ground-based networks, satellite platforms and sensors, and airborne sampling will continue building on existing accomplishments</td></tr><tr><td colspan="3"><strong>Completion by 2028</strong></td></tr><tr><td>Implementation of Now-casts</td><td>Aircraft operating at up to 1000 km/h need to know the current location of a volcanic ash cloud at any given time</td><td>It is expected that a three-dimensional representation of the current or near-current volcanic ash boundaries could eventually be made available and extracted by the user as required</td></tr><tr><td>Implementation of Probabilistic forecasts</td><td>Current volcanic ash forecasts are deterministic forecasts. They are a yes/no forecast, with respect to the depiction of the airspace impacted by discernible<sup>a</sup> volcanic ash</td><td>Probabilistic forecasts will provide decision makers with an assessment of all the likelihoods of risk of occurrence exceeding a defined magnitude</td></tr><tr><td colspan="3"><strong>Completion after 2028</strong></td></tr><tr><td>Other contaminant forecasts</td><td>There is a need to expand the warning services to other toxic emissions from volcanic eruptions</td><td>This issue is currently being studied by both ICAO and WMO experts</td></tr><tr><td>Trajectory based operations</td><td>Integration of volcanic cloud now-casts and forecasts, combined with the use of probabilistic forecasts to address uncertainty, is expected to significantly reduce the effects of volcanic cloud on air traffic flow</td><td>The meteorological and air traffic management communities are starting to work more closely on this objective</td></tr><tr><td>Development of Index levels for aircraft ash tolerances</td><td>Aircraft operators increasingly need quantitative volcanic ash forecasts to take advantage of yet to be specified aircraft and engine limits.</td><td>The development of a volcanic ash index for ash/gas tolerances of various types of engine/aircraft combinations is in the very initial stages of engineering review and concept design.</td></tr><tr><td>Airborne detection equipment</td><td>A few basic systems to alert pilots to the distal presence of volcanic ash are under evaluation</td><td>To allow operators to take advantage of tactical on-board volcanic ash detection equipment, new air traffic management processes will need to be developed</td></tr></tbody></table>

<footnote><sup>a</sup>Discernible ash is defined as “volcanic ash detected by defined impacts on/in aircraft or by agreed in-situ and/or remote-sensing techniques”; Visible ash is defined as “volcanic ash observed by the human eye” and not defined quantitatively by the observer</footnote>
Meeting (2012) to further develop and co-ordinate
work related to volcanic ash risk mitigation. The
main approaches from these initiatives to be
implemented by the IAVW Operations Group are
set out chronologically in Table 2.

In essence, the Plan calls for the enhancement of
collaborative processes in the observation and
provision of information, better land and aircraft-
based volcano and ash observations, the introduc-
tion of confidence levels to forecast information,
increased frequency of information, introduction of
probabilistic forecasts, and the introduction and use
of data on aircraft ash tolerances.

6 Conclusion

There is no doubt that future volcanic eruptions,
coupled with certain meteorological conditions,
have the potential to cause significant disruptions
to air transport (Sammonds et al. 2011).

The ongoing development of the IAVW system
continues to reveal significant challenges, some of
which may remain unresolved. Enacting a
fit-for-purpose warning network that brings vol-
canic hazard warnings into the aircraft cockpit
requires the bridging of gaps between two sciences
(volcanology and meteorology) in order to
understand the hazard, to knit the operational parts
of those sciences together in a single warning
system, and then to connect with operations in the
time and resource-critical aviation industry.

Fortunately, and arguably due in large part to the
IAVW system, there have been no fatalities asso-
ciated with aircraft operations proximal to volcanic
ash clouds. However, where the eruption is forecast,
warned for, resulting volcanic ash clouds tracked,
and with communications procedures in place and
followed, experience shows that aircraft are still not
always able to avoid volcanic ash clouds. Naturally,
where science or communications cannot provide
usable information, the operational risk rises.

The objective remains to provide increasingly
granular and robust information that will allow
aircraft to operate, safely and economically, proxi-
mal to volcanic ash in the atmosphere. While much
has been achieved, there is more to do, in proce-
dures, science, engineering, and in practical

communications. Without good warning system
communications, fully informed by the social sci-
ences that assist in the 'uptake' of the message, and
by robust, reliable operational practices, the fruit of
science and policy development will remain
compromised.

Lastly, because the advent of the IAVW has
brought the meteorological and aviation communi-
ties much closer to the volcanological community,
there is an exciting opportunity to bring potentially
useful practices further into the combined geo-
physical hazards space. For example, volcanic tsu-
nami, lahar warnings, ash fall, and even rainfall
induced lava dome collapses, are all areas where the
two fields will need to work together well to produce
enhanced warning and communication services.

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# Volcanic Gases: Silent Killers

Marie Edmonds, John Grattan and Sabina Michnowicz

## Abstract

Volcanic gases are insidious and often overlooked hazards. The effects of volcanic gases on life may be direct, such as asphyxiation, respiratory diseases and skin burns; or indirect, e.g. regional famine caused by the cooling that results from the presence of sulfate aerosols injected into the stratosphere during explosive eruptions. Although accounting for fewer fatalities overall than some other forms of volcanic hazards, history has shown that volcanic gases are implicated frequently in small-scale fatal events in diverse volcanic and geothermal regions. In order to mitigate risks due to volcanic gases, we must identify the challenges. The first relates to the difficulty of monitoring and hazard communication: gas concentrations may be elevated over large areas and may change rapidly with time. Developing alert and early warning systems that will be communicated in a timely fashion to the population is logistically difficult. The second challenge focuses on education and understanding risk. An effective response to warnings requires an educated population and a balanced weighing of conflicting cultural beliefs or economic interests with risk. In the case of gas hazards, this may also mean having the correct personal protection equipment, knowing where to go in case of evacuation and being aware of increased risk under certain sets of meteorological conditions. In this chapter we review several classes of gas hazard, the risks associated with them, potential risk mitigation strategies and ways of communicating risk. We discuss carbon dioxide flows and accumulations, including lake overturn events which have accounted for the greatest

<footnote>M. Edmonds (✉)
Earth Sciences, University of Cambridge, Downing
Street, Cambridge, Cambridgeshire, UK
e-mail: me201@cam.ac.uk</footnote>

<footnote>J. Grattan
Aberystwyth University, Aberystwyth, UK</footnote>

<footnote>S. Michnowicz
University College London, London, UK</footnote>
number of direct fatalities, the hazards arising from the injection of sulfate aerosol into the troposphere and into the stratosphere. A significant hazard facing the UK and northern Europe is a “Laki”-style eruption in Iceland, which will be associated with increased risk of respiratory illness and mortality due to poor air quality when gases and aerosols are dispersed over Europe. We discuss strategies for preparing for a future Laki style event and implications for society.

Volcanic gases have claimed directly the lives of >2000 people over the past 600 years (Auker et al. 2013). Millions more people have been impacted by volcanic gas, with effects ranging from respiratory irritation to neurological impacts, to crop failure and famine. Gas hazards contrast markedly with other volcanic hazards such as lahar, pyroclastic flows and ash fall; they are silent and invisible killers often prevailing over large areas of complex terrain. Volcanic gases may accumulate far from their source and flow down valleys as a gravity flow, engulfing and asphyxiating people as they sleep. Sometimes the hazard is visible in the form of a condensing plume emanating from a vent, with acidic gases capable of corroding buildings and aircraft, damaging crops and causing respiratory disease and skin burns. The trajectory and dispersal of such a plume is subject to local meteorology. The plume or gas cloud must be detected and tracked by sophisticated instrumentation. Designing a warning system that works in real time whilst incorporating both measurements and models tests the ingenuity of personnel at volcano observatories and meteorological agencies. Yet these hazard-warning systems are necessary if people are to live at close quarters with degassing volcanoes. The dissemination and communication of warnings associated with gas hazards requires effective alerts and systems in place to ensure that the warning gets to the part of the population at risk. The population must react to the warning in a way that mitigates risk; this is only possible if sufficient understanding of the hazard exists. The insidious hazard of volcanic gases is often poorly understood and overlooked. In this chapter, we

review the challenges associated with monitoring, detecting and communicating gas hazards and managing risk associated with gases. We start by reviewing the types of hazard.

# 1 Volcanic Gases, Insidious Hazards

A single event dominates the inventory of deaths due to volcanic gases: in August 1986 Lake Nyos (Cameroon, Africa) emitted a dense cloud of carbon dioxide ($CO_2$) gas in the middle of the night, which rapidly flowed down surrounding valleys, suffocating immediately 1700 sleeping people up to 20 km away from the lake (Kling et al. 1987). Many other deaths have occurred as a result of people encountering accumulations of $CO_2$ or hydrogen sulfide ($H_2S$) gases in low-lying areas or in the form of flows and clouds. In a recent analysis volcanic gas inundation was recognized as the second most common cause of death in the most frequent, fatal volcanic events (Auker et al. 2013). The key characteristic of this hazard is that usually there is no warning and no visible sign of it. Gas concentrations may creep up unnoticed until it too late, or a sudden inundation may leave no time for escape (Fig. 1).

Fatalities arising from the secondary effects of volcanic gases run into the millions over historical times (Rampino et al. 1988). Large explosive eruptions inject $SO_2$ directly into the stratosphere, which transforms rapidly (within hours to days) to sulfate aerosol (Robock 2000). The aerosol scatters and reflects incoming visible and UV radiation from the sun, causing tropospheric cooling over the lifetime of the aerosol (typically
<figure><img src="image_31.png" /></figure>

**Fig. 1** Cartoon to show the range of gas hazards and the scale of their impacts. **a** Diffuse degassing through fractures and faults. These gases are sourced from deep magma reservoirs. They may persist for long periods between and during eruptions. They typically affect local areas only but present significant hazards to people when gases accumulate in basements and topographic lows. **b** Acidic tropospheric plumes from active volcanic vents contain SO₂ and halogen gases. They lead to pervasive vog (sulfate aerosol) that may cause or exacerbate respiratory diseases. They may persist for many years during non-eruptive activity at some volcanoes and the

plumes are dispersed over 10 s of km. **c** Sudden flows of cold CO₂-rich gases occur as a consequence of lake overturn or phreatic explosions. They may last only minutes but may travel many 10 s of km in that time, flowing close to the ground with lethal concentrations of CO₂. **d** Large explosive eruptions inject SO₂ directly into the upper troposphere or stratosphere. The resulting sulfate aerosol has potential to cause significant regional and/or global environmental and climatic effects that may lead to cooling and crop failure, acid rain, increased mortality and crop failure over years timescales

a few years Fig. 1). Volcanic cooling has caused crop failure and famine for many years after large eruptions. Some recent eruptions (e.g. Pinatubo, Philippines, 1991 and El Chichon, Mexico, 1982) have allowed direct measurement of the reduction in direct radiative flux into the troposphere, total aerosol optical depth and tropospheric temperature (Dutton and Christy 1992), which validated predictions of the effects of stratospheric sulfate aerosol on climate. Large historic eruptions such as that of Tambora Volcano in 1815 (Indonesia) were associated with global cooling, leading to famine, social unrest

and epidemic typhus, leading to the “Year Without a Summer” (Oppenheimer 2003). A dramatic European example is the Laki (Iceland) eruption of 1783, which was followed by several years of crop failure and cold winters, resulting in the deaths of >10,000, ~20% of the Icelandic population (Grattan et al. 2003; Thordarson and Self 2003).

Another class of volcanic gas hazards is generally non-fatal, but gives rise to or exacerbates significant chronic and acute health conditions (Table 1). Persistent gas plumes at low levels in the atmosphere are common at many volcanoes
<table><caption>**Table 1** Health effects of volcanic gases (Hansell and Oppenheimer 2004)</caption><thead><tr><th>Gas species</th><th>Mode of dispersal</th><th>Type of hazard</th><th>In what quantity?</th><th>Acute effects</th><th>Chronic effects</th></tr></thead><tbody><tr><td rowspan="2">Sulfur dioxide, sulfate aerosol</td><td>Tropospheric gas plumes from vents or lava lakes</td><td>Acidic irritant</td><td>More than a few Mt</td><td>Upper airway irritation, pulmonary edema, nose, throat, skin irritation</td><td>Exacerbation of respiratory disease</td></tr><tr><td>Stratospheric injection during explosive eruption</td><td>Climate-forcing, particularly in tropics</td><td></td><td>Tropospheric cooling lasting 10<sup>0</sup>-10<sup>1</sup> years</td><td></td></tr><tr><td>Hydrogen sulfide</td><td>Diffuse degassing from the ground or from vents prior to or during eruptions</td><td>Irritant, asphyxiant, inhibitor of metabolic enzymes</td><td>Prolonged exposure &gt;50 ppm may cause death</td><td>Headache, nausea, vomiting, confusion, paralysis, diarrhea. Cough, shortness of breath, pulmonary edema. Eye and throat irritation</td><td></td></tr><tr><td>Fluoride compounds (HF, fluoride dissolved in water)</td><td>Tropospheric plumes during eruptions. Groundwaters and acid rain (through dissolution and/or leaching of ash particles)</td><td>Acidic irritant</td><td></td><td>Hypocalcemia, coughing, bronchitis, pneumonitis, pulmonary edema. Nausea, vomiting. Eye and throat irritation. Slow healing skin burns</td><td>Permanent lung injury. Mottling or pitting of dental enamel. Osteoporosis, kyphosis spine</td></tr><tr><td>Chloride compounds (HCl, other chlorides in gaseous and aqueous form)</td><td>Tropospheric plumes during eruptions. Groundwaters and acid rain. Plumes arising from the contact of lava and seawater</td><td>Acidic irritant</td><td></td><td>Coughing, bronchitis, pneumonitis, pulmonary edema. Eye and throat irritation</td><td>Permanent lung injury</td></tr><tr><td>Carbon dioxide</td><td>Diffuse/vent degassing pre- or syn-eruption. Overturn CO<sub>2</sub>-saturated lakes</td><td>Inert asphyxiant</td><td></td><td>Asphyxia, collapse</td><td>Paralysis, neurological damage</td></tr><tr><td>Carbon monoxide</td><td>Diffuse/vent degassing between or prior to eruptions</td><td>Noxious asphyxiant, binds to haemoglobin</td><td></td><td>Collapse, coma</td><td>Paralysis, neurological damage</td></tr><tr><td>Metals e.g. mercury Hg</td><td>Tropospheric plumes during eruptions, groundwater and diffuse degassing</td><td>Oxidant irritant</td><td></td><td>Bronchitis, pneumonitis, pulmonary edema. Neurotoxicity</td><td>Neurotoxicity</td></tr></tbody></table>

worldwide. These plumes may be rich in sulfate aerosol, generating a pervasive, choking haze. At Kīlauea Volcano, Hawaiʻi (Fig. 2), studies have

shown a link between incidences of plume inundation and asthma attacks in children (Longo et al. 2010a). These plumes give rise to acid rain and
<figure><img src="image_32.png" /><figcaption>**Fig. 2** Volcanic plume from the summit of Kīlauea Volcano, Hawai‘i. This plume contains acid gases and condensed water droplets, conducive to the formation of</figcaption></figure>

"vog" (volcanic smog, or sulfate aerosol). *Photograph credit* United States Geological Survey

their corrosive properties (arising from not just the SO₂ but also the acid halogen gases HCl and HF) leads to the damage of buildings, vehicles and infrastructure. These plumes may persist for decades or longer (Fig. 1), making them a significant health hazard (Delmelle et al. 2002). In other areas, interception of magmatic gases by groundwater aquifers may lead to contamination of water supplies that are tapped by springs. In East Africa, for example, the high concentrations of fluorine in the spring water, once dissolved in magmas many kilometres below, have caused widespread dental fluorosis (D'Alessandro 2006).

**What are volcanic gases?** Volcanic gases are mixtures of volatile compounds released from the ground's surface or directly from volcanic vents, into the atmosphere. They are generated when magmas exsolve volatiles at low pressures during their ascent to the surface and eruption.

Volcanic gases may precede the arrival of lava at the surface by several weeks or even months. In some cases, persistent and diffuse emissions of gases may take place continuously between eruptions, even when the eruptions occur very infrequently. The gases have different compositions depending on: tectonic setting, how close to the surface the degassing magma is stored and whether the fluids are interacting with a wet hydrothermal system prior to reaching the atmosphere (Giggenbach 1996). The gases that typically emanate from deep magma intrusions between and prior to eruptions are dominantly carbon dioxide (CO₂) and hydrogen sulfide (H₂S). When magma reaches the surface, the gas composition becomes dominated by the more melt-soluble components: water (which may make up >85 % by volume of the gas mixture), with lesser amounts of CO₂ and SO₂ (which make up 2–10 %),
halogen gases hydrogen fluoride (HF) and hydrogen chloride (HCl), and carbon monoxide (CO) and other minor components. If the gases interact with a hydrothermal system the acid gases SO₂ and HCl are removed, or “scrubbed” (Symonds et al. 2001); this is typical of the early stages of an eruption, or of “failed” eruptions (Werner et al. 2011). The components of volcanic gases that are of greatest concern for health are (Table 1), primarily CO₂, SO₂, H₂S, HCl, HF and metals such as mercury (Pyle and Mather 2003) and short-lived radioactive isotopes such as radon (Baxter et al. 1999). These gases and aerosols are of course also produced in many industrial settings and the risk of accidents in these settings has prompted most of the studies on their effects on health. Some gases undergo chemical reactions in the plume, resulting in secondary products that can cause health and environmental effects. Sulfur dioxide reacts with water to form sulfuric acid aerosol droplets that leads to acid rain in the troposphere (Mather et al. 2003). When injected into the stratosphere, the aerosols may reflect and absorb radiation from the sun, resulting in the cooling of the Earth’s surface for up to a few years for the largest eruptions over the past few decades, perhaps longer for larger classes of historic eruptions (Robock 2000).

There are multiple factors governing the magnitude of the volcanic gas health hazard and consequently, risk: the concentrations of gases (a function of both gas flux and composition), the mode of delivery to the atmosphere (e.g. from a point-source or over large areas; tropospheric or stratospheric) and the longevity or duration of the event. Monitoring networks should fulfill several functions in order to produce a realistic picture of the hazard: instrumentation coverage, precision (both spatial and temporal) and timeliness are critical. Once the hazard is identified and assessed, the nature of it must be communicated effectively to the communities at risk via an alert or warning

system. The reaction and response of the community to the risk communication must be appropriate and prompt, otherwise delays in evacuations and other risk mitigation procedures might occur. Preparing for future events requires an understanding of the hazard and its recurrence interval, robust monitoring networks and alarm systems, sophisticated models to simulate possible outcomes and risk mitigation plans to reduce or prevent fatalities. Whilst this sequence is well-developed for a subset of hazards in some localities, such as lahar, ash fall and lava flow inundation, there are very few examples of successful alert systems for gas hazards and even fewer that have been tested in extremely hazardous scenarios which might allow us to evaluate the effectiveness of hazard communication and risk mitigation. Challenges specific to gas hazards relate to: (1) the difficulty of achieving adequate coverage with regard to monitoring (e.g. gas concentrations may be low across most of an area, but there may be localized regions of high concentrations, so dense networks of instrumentation are required); (2) developing alert and early warning systems that will be communicated in a timely fashion to the population. Gas hazards may develop rapidly and be highly dispersed, making communication of warnings problematic. (3) Ensuring that an educated population will respond in a timely and appropriate way. An amenable response to warnings or evacuation orders requires an educated population and a balanced weighing of conflicting cultural beliefs or economic interests with risk. In the case of gas hazards, this may also mean having the correct personal protection equipment, such as gas masks; knowing where to go in case of evacuation (e.g. high ground); and being aware of increased risk under certain sets of meteorological conditions (e.g. on still days with no wind). Different hazards require vastly different responses. Large eruptions which inject gas (and ash, see Chap. XXX) into the upper atmosphere for example, give rise to regional, or global hazards that have their own unique set of challenges that focus on dealing with both immediate health effects and longer term impacts (social and economic) resulting from climate forcing. In this chapter we review some
key case studies and discuss the monitoring, alert and risk mitigation schemes that were in place or could be implemented for future events. We discuss the particular challenges inherent in dealing with gas hazards on all temporal and spatial scales and suggest profitable approaches for future development.

## 2 Developing Risk Mitigation Strategies for CO₂ Flows and Accumulations

Over the course of a decade beginning in 1979, our understanding of gas hazards was to take a dramatic turn. Events served as a stark reminder that volcanic gas hazards were capable of causing significant loss of life. Hazards from atmospheric CO₂ are usually limited, because atmospheric dispersion tends to dilute volcanic or hydrothermal gas emissions to the extent that concentrations become non-lethal rapidly away from a vent or degassing area. If however, geological, geographical, hydrological or meteorological factors bring about the accumulation of CO₂, or its concentration into a flow, the effects are life-threatening. Within the Dieng Volcanic Complex in central Java, on 20 February 1979, a sequence of earthquakes was followed by a phreatic eruption and sudden release of CO₂ (Allard et al. 1989; Le Guern et al. 1982). The area was known for its hydrothermal manifestations, with boiling mud pools, hot springs and areas of tree kill indicative of CO₂; local people are aware of “death valleys” in which vegetation is dead up to a certain level on the valley walls, and animals are often killed. People lived (and still do) in the low areas adjacent to grabens and phreatic craters known to have been sites of explosions and gas emissions in the past. After three large earthquakes between 2 and 4 a.m., a phreatic explosion at 5:15 was associated with the ejection of large blocks and a lahar that reached the outskirts of the village Kepucukan (Allard et al. 1989). Frightened by the activity, people attempted to escape from the village, walking west along the road to Batur, another village just 2 km away. Halfway there,

142 people were engulfed in “gas sheets” that emanated from the erupting crater, which killed them instantly. Gas emissions, dominated by CO₂, continued for another 8 months (Allard et al. 1989) and may have reached a total volume of 0.1 km³ (Allard et al. 1989).

Today, more than 500,000 people live in an area at high risk of hazardous CO₂ flows in Dieng caldera. Gas emission events occur frequently, heralded by seismicity (every few years with large events every few decades). A recent survey showed that 42 % of the people are aware of the risk of “poisonous gas” but only 16 % link this hazard to volcanic activity (Lavigne et al. 2008). Most people show a reluctance to accept the risk and a greater reluctance to leave the area due to a combination of religious and cultural beliefs (the area has been a sacred Hindu site since the 7th century) and economic factors (Dieng is agriculturally rich and in addition attracts many tourists). Farmers work within metres of dangerous mofettes (cold CO₂-producing fumaroles) and mark them with mounds of earth. Villages are situated at the mouths of valleys that connect phreatic craters on high ground with the caldera floor and which channel cold CO₂ flows (Fig. 3). Monitoring the hazards is therefore of utmost importance and takes place using a network of in situ logging geochemical sensors and seismometers, maintained by the Indonesian volcanological agencies. Monitoring is not easy: the sensors are difficult to maintain, have short lifetimes and do not have the spatial coverage required to monitor all of the gas-producing vents and areas. Since 1979, there have been six phreatic eruptions accompanied by elevated CO₂ emissions. Degassing crises in 2011 and in 2013, however, were successfully managed using the existing system, with CO₂ concentration levels used to assign alert levels. Gas emission forced the evacuation of 1200 residents following a phreatic eruption at Timbang crater on 29 May 2011, and people were advised to remain at least 1 km away from the crater, where dead birds and animals were found (Global Volcanism Program Report 2011). An improved network of telemetered arrays of sensors, webcam s and linked siren warning systems
for the surrounding villages was approved for USAID/USGS funding in 2013. For future events, it is widely assumed that phreatic eruptions will be preceded by significant seismicity (Le Guern et al. 1982). Evacuations of far larger areas will be necessary to protect the population from the gas hazard and Early Warning Systems are needed to communicate encroaching hazards.

It was not until 1986 that the wider public was exposed to the idea of volcanic gas hazards, when the 8th largest volcanic disaster in historical times occurred near to Lake Nyos in Cameroon. A landslide triggered the overturn of a density-stratified lake, within which CO₂ had concentrated in its lower levels. The sudden depressurization of the lake water upon overturn caused an outpouring of CO₂ from the lake and into a valley, killing 1746 people by asphyxiation, up to 25 km from the lake, as well as thousands of cattle (Kling et al. 1987). Around 15,000 people fled the area and survived but developed respiratory problems, lesions and

paralysis as a result of their exposure to the gas cloud (Baxter et al. 1989). There were no monitoring systems in place, no warning system and no assessment of risk before the event; scientists had no idea that this kind of event was possible prior to 1986.

It transpired, from isotopic analysis of the CO₂, that the gas had a magmatic origin, and had entered the lake from fault systems channeling gases from deep in the crust, derived ultimately from the mantle (Kling et al. 1987). There was no direct volcanic activity associated with the disaster. Gas sensor networks linked to siren systems were immediately set up at the edges of the lake and at the heads of the valleys to warn of future gas flow events. A unique hazard mitigation system was set up in 1999, funded by the United States and supplemented by the governments of Cameroon, France and Japan, with the aim of artificially degassing Lake Nyos by decompressing deep lake waters using three pipes, which work in a self-sustaining way,

<figure><img src="image_33.png" /><figcaption>**Fig. 3** Condensed steam and CO₂ accumulating in a valley close to Timbang Crater, Dieng Plateau, Indonesia in 2011. Note the dead vegetation below the level of the</figcaption></figure>

gas as a result of the high CO₂ concentrations. *Photograph credit* Andy Rosati, Volcano Discovery
initially pumping deep water towards the surface but thereafter driven by the degassing of CO₂ (Kling et al. 1994). The scheme has reduced gas pressures in the lake substantially, reducing the risk of future overturn and gas flow events, which would otherwise have occurred every few decades. A new hazard has been identified however, in the shape of a weak dam, raising the possibility that dam breach and removal of water from Lake Nyos could be a potential future trigger for a gas emission event, regardless of the degassing pipes. Added to this is the increasing risk to people, as they gradually resettle the area.

The Lake Nyos event was not unique; two years before the disaster a similar limnic eruption occurred at Lake Monoun, killing 38 people. Other lakes are associated with significant risks of similar events: at Lake Kivu, on the border of the Democratic Republic of Congo and Rwanda, recent measurements have shown that ~300 km³ of CO₂ (at standard temperature and pressure) are present in the lake's permanently stratified deep water (Schmid et al. 2005). Release of these gases by limnic overturn would have deadly consequences for the two million people living along the lake shore. It has been suggested that limnic eruptions in the Holocene have been responsible for local extinction events (Haberyan and Hecky 1987). Elsewhere, limnic eruptions have been implicated in the deaths of a wide range of Eocene vertebrates, which were subsequently preserved to an exceptional degree, at the Messel Pit (Germany), which was, in Eocene times, a crater lake over a maar (Franzen and Köster 1994). Limnic eruptions remain, however, a rare, if extremely hazardous, event.

Outstanding questions are those concerning how to mitigate hazard and manage early warning systems and how to reduce risk associated with these silent, yet deadly hazards. Considerable interest in modeling gas flow over topography has arisen from recent developments in CO₂ transport as a supercritical fluid through long-range pipelines for carbon sequestration (Duncan and Wang 2014). The possibility of a breach in a pipeline and associated gas flow has prompted investment in gas hazard assessment. At Mefite D'Ansanto in central Italy, a near-pure

CO₂ gas flows down a channel at a rate of ~1000 tonnes per day (Chiodini et al. 2010). The flow reaches a height (defined by a gas concentration of 5 vol%) of 3 m above the valley floor (far higher than a typical human). Using measurements of CO₂ concentration at various heights and distances in the valley to constrain the model and a local wind field, a gas transport model (TWODEE-2; Folch et al. 2009) was used to simulate the gas flow and to predict the zones of potential hazard for humans in terms of dangerous (>5 vol%), very dangerous (>10 vol%) and lethal (>15 vol%) concentrations, which has been used successfully for risk mitigation in the area. Gas transport models will have great utility in areas subject to dense, cold gas flows and are relatively inexpensive to implement, given appropriate constraints and calibrations provided by field measurements. Their unique advantage is that they provide a means to convert discrete measurements of gas concentrations using sensors into a fully 3-D continuous model of gas concentration and hazard that can be straightforwardly incorporated into warning systems.

The gas flows described above are extreme; there are numerous examples of smaller scale gas accumulation hazards that have caused loss of life. These kinds of manifestations have been shown to be the most frequently associated with deaths in the record (Auker et al. 2013) and as such, require robust monitoring, alert systems and risk assessment. Areas of tree kill and asphyxiated animals were reported at Mammoth Mountain, inside Long Valley Caldera, beginning in 1990 and caused by the diffuse emission of CO₂ over 0.5 km² that reached up to 1200 tons/day at its peak (Farrar et al. 1995), following a swarm of earthquakes and an intrusion in 1989. The emissions have caused fatalities: in 2006 three ski patrollers died after falling close to a fumarole. The gas hazards occur in a recreational area visited by 1.3 million skiers in the winter and 1.5 million hikers in the summer. Monitoring has been undertaken since 1990 in the form of campaign-style measurements using soil gas chamber spectrometers, and then through three permanently installed soil gas instruments, operated and monitored by United States
Geological Survey scientists (Gerlach et al. 2001). Risk mitigation measures include the posting of signs in prominent areas warning of the hazards associated with gas accumulations in topographic lows. For this lower level of hazard, this communication method is effective and has resulted in a largely safe enjoyment of the area by a largely educated public, despite the gas emissions.

In the Azores, in the mid-Atlantic, the situation is rather more precarious. On Sao Miguel Island, villages are situated within the Furnas volcanic caldera (Baxter et al. 1999; Viveiros et al. 2010). This is the site of numerous gas manifestations such as boiling fumaroles, diffuse emissions and cold CO₂-rich springs. It is an area popular with tourists, who enjoy the thermal spas. Up to 98 % of the houses, however, are situated over CO₂ degassing sites (Viveiros et al. 2010). A study in 1999, which has been repeated many times subsequently, showed that lethal concentrations of CO₂ (>15 vol%) existed in non-ventilated confined spaces in the houses (Baxter et al. 1999). There have been no confirmed cases of deaths in the area from CO₂ asphyxia but there exist frequent anecdotal records of people being “overcome” by gases (Baxter et al. 1999). No formal early warning or alert system exists, but there are soil gas flux spectrometers and soil temperature sensors located in the village that telemeter data back to the Azores Monitoring Centre for Volcanology and Geothermal Energy in real time. A survey of the population of the village of Furnas carried out in 1999 showed that, astonishingly, not a single one of 50 random adult respondents had any knowledge about the existence of gas hazards in the area. Upon closer questioning of the wider population only a very small fraction, mainly civil defense and medical workers, were aware of the hazard (Dibben and Chester 1999). This shows a profound lack of education of the general population by the scientific establishment at the time of the survey. Whilst a more recent survey has not been carried out, it is likely that this has improved in recent years with the enhancement of monitoring and the responsibility to safeguard tourists. But this

situation raises some thorny issues concerned with risk mitigation (Dibben and Chester 1999). Highlighting the most vulnerable areas in the village is likely to reduce the value of property in those areas and so the public will likely be averse to accepting such information. Gas hazard alerts might affect tourism and hence the economic status of the area. Building regulations to prevent the build up of CO₂ in basements might be harder for the poor to comply with, resulting in a socially divisive vulnerability structure. Lastly, installation of a high spatial coverage, precise and reliable monitoring and early warning system might lead the population to believe that they are no longer threatened, encouraging risky behaviors.

### 3 Monitoring and Communicating “Vog” Hazards

When magma is close to the Earth’s surface (and when the gases do not interact with extensive wet hydrothermal systems), the gas hazards fall into a different category to those described above. In this case, acidic gases such as sulfur dioxide, hydrogen chlorine and hydrogen fluoride become important hazards. Active volcanism is therefore associated with thick plumes containing a mixture of these acid gases, as well as water, CO₂ and minor carbon monoxide (CO) and hydrogen sulfide (H₂S). Under these conditions, volcanic smog or “vog” may cause acute respiratory difficulties and skin, noise and throat irritation. Vog, which is made up of sulfate aerosol particles, has been linked to asthma and other respiratory diseases (Hansell and Oppenheimer 2004). Some volcanoes degas prodigious fluxes of gases quasi-continuously. Mount Etna, in Italy, for example, produces several thousand tons of SO₂ and significant quantities of other acidic gases every day and activity has persisted at this level for decades (Allard et al. 1991). Other prodigious producers of tropospheric volcanic gas plumes are Nyiragongo (Democratic Republic of Congo), Ambrym (Vanuatu), Kīlauea (USA), Erebus (Antarctica), Masaya (Nicaragua), Erta Ale (Ethiopia) and Villarica (Chile). Some of
these volcanoes are sparsely populated; others have major urban centres within range of their plumes.

Kīlauea Volcano, Hawaiʻi, has been in continuous eruption since 1983. At Kīlauea, magma is outgassing at both the summit (since 2008) and from eruption sites and active lava fields on the east rift zone (Longo et al. 2010a), giving rise to multiple sources of gases. The emissions affect not only the 2 million visitors to Hawaiʻi Volcanoes National Park every year, but also wider areas of Big Island and the other Hawaiian islands via dispersal by the trade winds (Fig. 4). It has been shown that indoor SO₂ concentrations regularly exceed the World Health Organisation guidelines in the affected areas of Big Island (Longo et al. 2010b) and that during periods of enhanced volcanic outgassing there are synchronous increases in the occurrence of acute

respiratory conditions requiring treatment on the island (Longo et al. 2010a). In response to the clear need for a system of monitoring and early warning, SO₂ concentration sensor data from inside the park and around the island are combined with SO₂ emission rates and a model for plume dispersion to produce a vog model that forecasts air quality for the Hawaiian Islands (Fig. 5). These warnings have proven to be a very successful way of mitigating risks due to vog; statistical analysis has shown that the predictions lie within one standard deviation of the data for forecasts up to 24 h ahead (Reikard 2012). Advice to residents to minimize their exposure to vog once a forecast or warning for high aerosol concentrations has been issued include closing windows and doors, limiting outdoor activities and exertion and having medications on hand. Communication of vog

<figure><img src="image_34.png" /><figcaption>**Fig. 4** Hawaiian Islands, December 3, 2008, showing a pervasive tropospheric vog plume carried westwards from Kīlauea Volcano by the Trade winds. Image acquired by</figcaption></figure>

the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite
Island of Hawaii SO₂

<figure><img src="image_35.png" /><figcaption>**Fig. 5** Model to forecast “vog” and communicate vog hazard warnings for the Hawaiian Islands. The model uses estimates of volcanic gas emissions along with forecast winds to predict the concentrations of sulfur dioxide gas (SO₂, left) and sulfate aerosol particles (SO₄, right)</figcaption></figure>

Island of Hawaii Sulfate Aerosols

<figure><img src="image_36.png" /></figure>

downwind of the ongoing Kīlauea Volcano eruption. Images from the Vog Measurement and Prediction Website (VMAP; http://weather.hawaii.edu/vmap), hosted by the School of Ocean and Earth Science and Technology, University of Hawaiʻi at Manoa

warnings takes place via the web, radio, field units and road signs. This style of monitoring, modeling, forecasting, warning and communication might profitably be applied to many other volcanic centres facing similar tropospheric volcanic aerosol pollution in the future.

# 4 The Great Dry Fog: Preparing for a Future Laki-Style Event

The Laki (Lakigigar) eruption 1783–1784 is known to be the largest air pollution incident in recorded history and its effects were felt throughout the northern hemisphere (Grattan 1998). Activity in this area of southern Iceland began in mid-May 1783 with weak earthquakes which intensified into June. On the 8th of June, the 27 km long fissure opened up with more than 140 vents (Thordarson and Hoskuldsson 2002; Thordarson et al. 1996). The eruption pumped 100 million tonnes of SO₂ into the westerly jet stream, producing sulfur-rich plumes that were dispersed eastwards over the Eurasian continent and north to the Arctic. The reaction of SO₂ with

atmospheric vapour produced 200 million tonnes of sulfate aerosol, of which 175 million tonnes were removed during the summer and autumn of 1783 via subsiding air masses within high pressure systems (Thordarson and Hoskuldsson 2002; Thordarson and Self 2003). At its peak, this mechanism may have been delivering up to six million tonnes of sulfate aerosol to the boundary layer of the atmosphere over Europe each day (Stothers 1996). The explosive activity from the eruption produced a tephra layer that covered over 8000 km² and is estimated to have produced 12 km³ of tholeiitic lava flows. Ten eruption episodes occurred during the first five months of activity at Laki, each with a few days of explosive eruptions followed by a longer phase of lava emissions. Volcanic activity began to decrease in December 1783 and ceased on the 7th of February 1784 (Steingrímsson 1998; Thordarson and Hoskuldsson 2002; Thordarson and Self 2003).

The consequences of the eruption were catastrophic. In Iceland, acid rains destroyed grazing and more than half of the livestock died from starvation or in combination with skeletal fluorosis (bone deformation resulting from the
ingestion of high levels of fluorine) precipitated
from erupted fluorine gases. More than a quarter
of Iceland's population subsequently died from
starvation and the survivors suffered from
growths, scurvy, dysentery, and ailments of the
heart and lungs (Steingrímsson 1998). The
aerosol produced in the atmosphere resulted in a
“dry fog” which hung over Britain, Scandinavia,
France, Belgium, the Netherlands, Germany and
Italy during the summer of 1783, affecting
human health and withering vegetation (Durand
and Grattan 2001). The aerosol also caused
severe climatic perturbations. In the UK, August
temperatures in 1783 were 2.5–3 °C higher than
the decadal average, creating the hottest summer
on record for 200 years. A bitterly cold winter
followed, with temperatures 2 °C below average
(Luterbacher et al. 2004). Coincidentally, in
England, the death rate doubled during July
1783–June 1784 with 30,000 additional deaths
recorded (Federation of Family History Societies
2010; Grattan et al. 2007; Witham and Oppen-
heimer 2004b). This period is classified as a
‘mortality crisis’ because the annual national
mortality rate was 10–20 % above the 51-year
moving mean (Wrigley and Schofield 1989).
Two discrete periods of crisis mortality occurred:
August–September 1783 and January–February
1784, which in combination accounted for
around 20,000 additional deaths, with the East of
England the most affected region (Witham and
Oppenheimer 2004a). Crisis years are not unu-
sual however, during the period 1541–1870 there
were 22 crises where the death rate was 20–30 %
higher, which is greater than the 1783–84 crisis
of 16.7 % (Grattan et al. 2003). Whilst it is dif-
ficult to prove a direct causal link between the
eruption and the mortality crisis, the connection
between temperature extremes and mortality of
the elderly or vulnerable is well established
(Keatinge and Donaldson 2004; Kovats 2008;
Royal Society 2014; Wilkinson et al. 2004). The
effects of the Laki volcanic cloud are implicated
in the climatic anomalies of 1783–4 and it is
therefore likely that the Laki Craters eruption did
contribute to the crises (Grattan et al. 2003;
Witham and Oppenheimer 2004a).

Current levels of particulate air pollution in
many parts of the UK exert considerable impact
upon public health (Public Health England
2014). Epidemiological studies have linked pre-
mature mortality with exposure to air pollution,
particularly to particles smaller than 2.5 µm in
diameter (PM2.5) (Pope and Dockery 2006).
During a 14 day period in March and April 2014,
air pollution was ‘very high’ (based on govern-
ment monitoring of PM10 and PM2.5) across the
UK, which resulted in 3500 additional healthcare
visits for acute respiratory symptoms and
approximately 500 for severe asthma (Smith
et al. 2015). The air pollution episode was due to
anticyclonic atmospheric conditions which
brought together local air pollution emissions,
pollution from continental Europe and dust
transported atmospherically from the Sahara
(Smith et al. 2015). Air pollution levels resulting
solely from local emissions also regularly breach
European Union directives; NO₂ is of particular
concern and in April 2015 the UK Supreme
Court ruled that the government must submit
new air quality plans to the European Commis-
sion by the end of the calendar year (Supreme
Court Press Office 2015).

Given that air pollution in parts of the UK is
regularly at (or in breach of) permissible levels,
even a modest-sized eruption in Iceland could
push UK cities over the threshold into very high
levels of pollution. Over the last 1130 years, there
have been four fissure eruptions in Iceland that
caused environmental and climatic perturbation,
of which Laki was the second largest and the
occurrence of a contemporary Laki-style eruption
poses a serious threat to the health of European
populations. The need for preparedness for such
an event was raised by a Geological Society
working group in 2005 (Sparks et al. 2005) and
subsequently added to the National Risk Register
of Civil Emergencies (Loughlin et al. 2014).

Recent modelling of likely excess mortality
resulting from a modern Laki reveals that a
similar-sized eruption would produce, on aver-
age, 120 % more PM2.5 over background levels,
which would result in 142,000 additional deaths,
an increase of 3.5 % in the mortality rate
(Schmidt et al. 2011). This rate of mortality is much lower than actually occurred during the 1780s, which could be due to several factors, including the assumption that modern populations are more resilient to air pollution and environmental stress (which may not be the case), and that the concentration response functions in the model do not account for all adverse health effects (i.e. asthma caused by elevated SO₂) (Schmidt et al. 2011).

The link between elevated mortality and extremes of temperature is also well-established and therefore volcanically-induced anomalous weather could also contribute to a post-eruptive death toll. The European heatwave of 2003 was a three week period of abnormally hot weather which resulted in over 52,000 deaths across Europe with cities particularly affected (Royal Society 2014). There were over 14,800 fatalities in France, with excess mortality greater than 78 % in Paris, Dijon, Poitiers, Le Mans and Lyon. In the UK there were 2091 fatalities of which 616 occurred in London alone (Kovats and Kristie 2006; Royal Society 2014). There was a resultant increase in heat health warning systems across Europe (heat surveillance systems with associated risk warnings and awareness raising) with 16 active by 2006, which resulted in a reduction in the mortality following the 2006 heatwave (Royal Society 2014). The World Health Organisation's EuroHEAT project researches heat health effects in European cities, preparedness and public health system responses. It has highlighted that the health burdens fall disproportionately on those living in urban areas, particularly if they are also physiologically susceptible, socio-economically disadvantaged and live in degraded environments; a variety of practical measures to increase resilience have been suggested alongside legislation, national plans and social capital-building (World Health Organization 2007).

A future eruption similar to Laki would likely be forecast days to weeks in advance using the sophisticated volcano monitoring networks that are in place (Sigmundsson et al. 2014). The eruption itself would likely be accompanied by prolonged high fluxes of gases and ash,

producing an aerosol-laden plume in the troposphere, as observed in recent Icelandic eruptions. During some prolonged or particularly intense periods of eruption the plume may even reach the stratosphere (Thordarson and Self 2003). The plume will be modified physically and chemically as it moves away from the vent. Dispersal largely depends on wind direction and shear, meteorological conditions, synoptic-scale features (Dacre et al. 2013) and the stability of the atmosphere. Reactions take place in the gas phase and on the surfaces of ash and aerosol particles, where SO₂ is transformed to sulfate aerosol as well as other chemical reactions involving halogen radicals and ozone and NOₓ species (von Glasow et al. 2009). Chemical transformations of the plume will depend on the availability of surfaces for reactions and will be affected by particle aggregation and sedimentation. The lifetime of sulphate aerosols and SO₂ in the troposphere depends on altitude and season and is of the order of 5–10 days at the low altitudes between UK and Iceland (Stevenson et al. 2003). The source parameters and associated uncertainties for modelling of a Laki eruption scenario were developed by the British Geological Survey who determined that once an eruption was underway and assuming the least favourable meteorological conditions for the UK (a strong north-westerly wind), there would be a minimum lead time of approximately six hours (Loughlin et al. 2013). A sustained supply of gas and aerosol from the source and unfavourable meteorology might maintain long-term (months) direct impacts in the UK (Loughlin et al. 2014).

Most of the risks associated with the eruption could be mitigated, given sufficient time to prepare for them, but there is work to be done in preparing guidelines to deal with hazards such as acid rain, increased levels of atmospheric pollutants, contaminated water, and the effect of aerosol on aviation (Loughlin et al. 2014). An effective response to an impending crisis will also require a much better understanding of plume chemistry and dispersion and its effects on the environment and on climate; there is a clear need to make these a research priority. Tracking volcanic clouds using satellites is now possible
for eruptions in most parts of the world (Fig. 6), but there is clearly scope to improve coverage in both time and space (including depth resolution

in the atmosphere). Air quality monitoring networks would require augmentation and coordination to be used as input to forecasting models.

<figure><img src="image_37.png" /><figcaption>**Fig. 6** Risk mitigation during a future large eruption in Iceland will depend on effective monitoring and hazard forecasting, which will be possible with a new generation of satellite-based sensors e.g. ESA's Sentinal 5 Precursor mission. Here we show data from existing satellite-based sensors. The OMI instrument on NASA's Aura satellite can image the spatial distribution (in x-y) of **a** sulfur dioxide and **b** sulfate aerosol in the atmosphere from volcanic</figcaption></figure>

eruptions. These simultaneous traces were recorded on 8 May 2010 during the Eyjafjallajökull eruption (NASA). On April 17, 2010, during the same eruption, NASA's Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite captured this image of the Eyjafjallajökull Volcano ash and aerosol cloud, providing a vertical profile of a slice of the atmosphere
There are many examples of smaller scale gas and aerosol monitoring and alert systems that have been successful (e.g. Kîlauea, USA; Mijakejima, Japan), but there are particular challenges applying these kinds of strategies to large regions potentially to include the whole of northern Europe. A major breakthrough has been the development of sophisticated modelling of aerosol formation, transport and loss. Early models used Global Circulation Models to simulate aerosol formation and its effects on climate (Chenet et al. 2005; Highwood and Stevenson 2003) but it was recognised that fully coupled chemistry and microphysics models were required in order to simulate aerosol size distributions (Schmidt et al. 2010). Recently, the atmospheric chemistry and meteorology model NAME (Jones et al. 2007) has shown promise for modelling the physical dispersion and transformation of volcanic SO₂ to aerosol. Current modelling is exploring the likelihood of near-surface concentrations of sulfur and halogen species exceeding health thresholds and the effects of acid deposition on ecosystems (Witham et al. 2014). Whilst these models are sophisticated, it is important to note that all models inherently involve uncertainties; particularly significant here are the estimated volcanic ash emission rates (Witham et al. 2012). A striking new finding from modelling the effects of tropospheric SO₂ emissions from the 2014 Holuhraun eruption has been that the sulfate aerosol increases the albedo of liquid clouds, causing a radiative forcing that might have been observable, had the eruption continued into summer 2015 (Gettelman et al. 2015). Radiative forcing of this magnitude is sufficient to cause changes in atmospheric circulation and might be a feasible mechanism to explain the far-reaching climatic effects of the 1783 Laki eruption (Gettelman et al. 2015). Understanding how dominantly tropospheric SO₂ emissions from large Icelandic flood basalt eruptions may affect climate and ultimately European air quality is a critical component of mitigating risk from a future eruption. The recent eruptions of Eyjafjallajökull (2010), Grímsvötn (2011) and Holuhraun (2014) illustrate well that Icelandic eruptions have

potential to disrupt aviation, our economy and air quality; the impacts of an even larger future eruption will undoubtedly extend into the realms of human health, agriculture and the structure of our society.

# 5 Perspectives for the Future

We have shown that the hazards due to volcanic gases are diverse in terms of not only their chemical nature but also their impacts. Monitoring and modeling the hazards, producing effective warning or forecast systems and risk mitigation strategies are all associated with unique challenges not shared with other volcanic hazards. Gas hazards may be diffuse and affect a large area. While there have been examples of successful monitoring strategies that integrate observations into sophisticated models describing gas behavior, these are few and far between. Future work requires innovative and far-reaching solutions to these monitoring challenges that can be applied in developing countries with minimal maintenance. Arguably the greatest strides are being made in modelling, with sophisticated models that couple chemistry with particle microphysics showing great promise as a monitoring and risk mitigation tool when combined with high quality ground- and satellite-based observations of volcanic emissions. Overcoming the challenges associated with educating populations with regard to gas hazards and maintaining effective communications is critical for future risk mitigation. Our greatest challenge may be a future large fissure eruption in Iceland, which may have significant consequences for air quality, our economy and environment in Europe and in North America.

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<figure><img src="image_38.png" /></figure>
# Active Hydrothermal Features as Tourist Attractions

Patricia Erfurt-Cooper

## Abstract

Tourists are looking increasingly for adventurous experiences by exploring unusual and interesting landscapes. Active volcanic and hydrothermal landscapes and their remarkable manifestations of geysers, fumaroles and boiling mud ponds are some of the surface features that fascinate visitors of National Parks, Geoparks and World Heritage areas worldwide. The uniqueness of hydrothermal activity based on volcanism has provided popular tourist attractions in many countries for several thousand years. The Romans for example have used hydrothermal springs on the Italian island Ischia and visited the Campi Flegrei for recreational purposes. In Iceland the original Geysir already attracted international visitors over 150 years ago, who came to observe this spectacular hydrothermal phenomenon. In Greece and Turkey volcanic hot springs have historically provided attractive destinations, as well as in New Zealand, Japan and the Americas. The fact that locations with hydrothermal activity based on active volcanism have acquired various forms of protected site status, adds a further dimension to their attraction and demonstrates a significant contribution to sustainable and nature based tourism. Countries such as Iceland, New Zealand and Japan have a long tradition of using hydrothermal activity in its various forms to offer tourists a unique natural experience. These environments however are also known for their unpredictable and potentially hostile nature, as the use of hydrothermal features as a natural resource for tourism does harbour certain risks with the potential to affect human health and safety. Hydrothermal systems have erupted in the past, thereby causing the destruction of their immediate environment. Depending on the level of magnitude explosions of super heated water and steam mixed with fractured rocks and hot mud can be violent enough to create craters varying in size from a few metres

<footnote>P. Erfurt-Cooper (✉)
GEOTOURISM Australia, Canberra ACT, Australia
e-mail: Patricia.Erfurt@my.jcu.edu.au</footnote>
to several hundred metres in diameter. Apart from unexpected eruptions of hydrothermal vents with the potential to cause thermal burns, further risk factors include seismic activity such as earthquakes, lethal gas emissions of hydrogen sulphide (H2S) as well as ground instability through hydrothermal alteration. While it is essential to prevent injuries to tourists the management of hydrothermal hazards remains problematic. Precursory signs are not well understood by the general public and the communication of imminent danger is frequently unachievable. As a consequence serious thought needs to be given to the risk factors and the potential danger of areas in the proximity of active hydrothermal manifestations such as extreme hot springs and geysers. To improve the safety standards in hydrothermal landscapes that are used as main features in tourism, strategic guidelines for best practice management must cover ALL active volcanic and hydrothermal areas. This chapter looks at management issues at hydrothermal destinations with special consideration of areas where these unique features are integrated as tourist attractions. Examples from destinations traditionally based on active volcanic and hydrothermal phenomena are presented as case studies to highlight the risk management processes in individual countries. Potential hazards in volcanic and hydrothermal areas are assessed with a focus on the prevention of accidents and injuries to tourists.

**Keywords**

Hydrothermal activity • Protected site status • Risk management • Sustainable tourism • Volcanic environments

# 1 Introduction

## 1.1 Visitor Safety in Hydrothermal Environments

Tourists are looking increasingly for adventurous experiences by exploring unusual and interesting destinations. Active volcanic and hydrothermal landforms and their remarkable manifestations of geysers, fumaroles and boiling mud ponds are some of the surface features that fascinate tourists worldwide. The uniqueness of hydrothermal activity based on volcanism has provided popular tourist attractions in many countries for several thousand years. The Romans for example used hydrothermal springs on the Italian island Ischia and visited Campi Flegrei for recreational purposes. In Iceland the original Geysir attracted international visitors over 150 years ago who

came to observe this spectacular hydrothermal phenomenon. In many other countries worldwide (Greece, Turkey, New Zealand, Japan, China and the Americas) hydrothermal activity in its various forms has historically provided attractive destinations.

The fact that locations with hydrothermal activity, commonly based on active volcanism, have acquired various forms of protected site status (e.g. National Parks, Geoparks and World Heritage Areas) adds a further dimension to their attraction and demonstrates a significant contribution to sustainable and nature based tourism. However, these environments are also known for their unpredictable and potentially hostile nature and the use of hydrothermal features as a natural resource for tourism does have certain risks with the potential to affect human health and safety.
This chapter examines the communication of hazards and the potential risks associated with sites where hydrothermal features are major tourist attractions. Examples from tourist destinations based on active hydrothermal phenomena are presented as brief case studies to highlight the importance of hazard and risk communication. To prevent unnecessary exposure to hazards, which can escalate into a crisis situation, visitors of hydrothermal attractions must be made aware of potential hazards that could carry the risk of personal injury or death. As many hydrothermal areas are located in close proximity to active volcanic systems, this chapter occasionally refers to both environments and their correlated hazards.

## 1.2 Definitions of Hazard, Risk and Vulnerability

First of all, the actual meaning of the common language terms hazard, risk and vulnerability needs to be clarified in relation to the subject matter of this chapter. While the term hazard is often used as a synonym for danger and/or risk, a hazard is scientifically defined as the probability of a natural event occurring as well as being a potential source of vulnerability (exposure to danger). The term vulnerability refers to the susceptibility and inability of humans or physical structures to withstand the impacts of natural hazards. Vulnerability in hydrothermal areas based on volcanic activity takes into account the real possibility of causing injury, damage and loss of life (Aspinall and Blong 2015; Barclay

et al. 2015; Jolly and De La Cruz 2015; McGuire et al. 2009; UNISIDR 2016). Vulnerability can be a consequence of either being unsuspecting of potential risks or ignoring these while visiting sometimes remote or unsafe areas without suitable defence structures or shelters. Taking a risk in these environments therefore can result in vulnerability due to exposure of hazards and includes the probability of being harmed in the process. This can be based on a lack of awareness about the potential risks and/or a lack of appropriate hazard communication.

Potential hazards in areas of hydrothermal activity (Table 7.1) are generally assessed with the main focus on minimising the risk of accidents and injuries. The process of risk identification recognises potential hazards as well as any potential vulnerability from the damaging effects of a hazard (Aspinall and Blong 2015; UNISIDR 2014). Also, the risk to visitors is considered to increase with extended time spent in an active hydrothermal area (Bratton et al. 2013). It is therefore highly recommended that all visitors of active hydrothermal environments are aware of the particular hazards and the potential risks in these areas.

In this regard, a crisis can be defined as an unstable and hazardous situation of increased danger that has reached a critical phase (De La Cruz-Reyna et al. 2000). Communication of scientific advice in a crisis situation must clearly reflect the level of danger to raise awareness about the real hazard level and to avoid misunderstanding as to the likely consequences (Jolly and De La Cruz 2015).

<table><caption>**Table 7.1** Examples of the most common hydrothermal hazards</caption><thead><tr><th colspan="2">Potential hazards in active hydrothermal areas</th></tr></thead><tbody><tr><td>Seismic activity—unexpected earthquakes</td><td>Sudden change of location of hot water source</td></tr><tr><td>Toxic fumes and gas emissions</td><td>Sudden change of flow rates, direction and currents of hot water source</td></tr><tr><td>Unstable ground</td><td>Thermal burns from extreme hot springs</td></tr><tr><td>Unexpected hydrothermal eruptions</td><td>Health hazards from thermophilic microbes and bacteria</td></tr><tr><td>Hydrothermal steam discharge</td><td></td></tr><tr><td>Sudden change of water temperature</td><td></td></tr></tbody></table>
## 1.3 Hydrothermal or Geothermal?

Now and again there appears to be confusion between the terms hydrothermal and geothermal. The term hydrothermal refers to hot water and is derived from the Greek meaning of *hydros* for water and *thermos* for heat. Likewise, the term geothermal has its origin in the Greek language with the prefix *geo* referring to earth. To clarify the difference between hydrothermal and geothermal Heasler et al. (2009) describe hydrothermal as a subset of geothermal, whereby geothermal refers to any system that transfers heat from the interior of the earth to the surface involving water, both as a liquid and steam (Keary 1996). All hydrothermal systems related to volcanism are based on a geothermal heat source in the form of an active magma chamber or a cooling magma body (Hochstein and Browne 2000). Consequently, water emerging from a hydrothermal vent is correctly termed geothermal water, but this term can also refer to water heated by convective circulation deep underground without the proximity of a magma body (Heasler et al. 2009). The actual process of heat transfer involves the circulation of groundwater from a subterranean reservoir to the surface. Here, individual hydrothermal features emerge in the form of hot springs and geysers, or in the case of subaqueous hydrothermal vents in close proximity to an underlying magma body as the emission of superheated mineral rich solutions, known as Black or White Smokers.

The temperature range of such hydrothermal systems is estimated to be typically between 50 °C and up to over 400 °C in deeper reservoirs (Haase et al. 2009). According to Heasler et al. (2009) hydrothermal systems present a continuum of resource temperatures that is relatively open-ended. In comparison the temperature range of

natural hot springs utilised for health and recreational facilities lies generally between 37 °C and the boiling point of water at sea level (100 °C). These natural hot springs, independent of whether their origin is volcanic or non-volcanic, are frequently referred to as either geothermal or just as thermal springs (Erfurt-Cooper 2012).

# 2 The Challenges of Hydrothermal Tourist Sites

## 2.1 Direct Use of Hot Springs as Tourist Attraction

Hydrothermal features play an important role in tourism and are a favourite with people who are looking for unusual natural experiences with a touch of adventure (Tables 7.2 and 7.3). Many hydrothermal areas are marketed as family friendly must-see destinations, offering a once-in-a-lifetime occasion to encounter the raw power of nature. Another reason for people to visit active areas is that features may be ephemeral and may become inaccessible or disappear altogether due to earthquakes or volcanic activity (e.g. Valley of the Geysers in Kamchatka—mudflow in 2007).

Hot springs, geysers, boiling lakes, bubbling mud pools and hissing steam vents are common in countries with active as well as dormant volcanism (e.g. New Zealand, Japan, Iceland (Case Study 7.1), the Americas, Africa and China). Located in protected areas such as national parks or geoparks can be an advantage in controlling access to hazardous sites, although providing safety is a definite challenge, which depends on many variables including language barriers. For example, the family affected in Case Study 7.2 did not speak English, which may have contributed to the horrific accident.

<table><caption>**Table 7.2** Examples of hydrothermal features based on volcanism that are used as tourist attractions worldwide</caption><thead><tr><th colspan="2">Hydrothermal Features used as Tourist Attractions</th></tr></thead><tbody><tr><td>Fumaroles/steam vents</td><td>Boiling mud pots</td></tr><tr><td>Geysers</td><td>Explosion craters</td></tr><tr><td>Hot lakes</td><td>Sinter terraces</td></tr><tr><td>Hot rivers and streams</td><td>Hot springs (for bathing)</td></tr><tr><td>Hot waterfalls</td><td>Hot springs (for cooking)</td></tr><tr><td>Mud volcanoes</td><td>Geothermal power stations</td></tr></tbody></table>
<table><caption>**Table 7.3** Hydrothermal features play an important role in the marketing of tourist destinations</caption><thead><tr><th>The role of hydrothermal features in tourism</th></tr></thead><tbody><tr><td><ul><li>Unique selling point for destination development</li><li>Value adding when combined with other recreational facilities</li><li>Significant resource for Geotourism with opportunities to learn about hydrothermal features and their geological heritage</li></ul></td><td><ul><li>Integration into Health & Wellness tourism by utilising geothermal spring water</li><li>Sustainable development based on the use of renewable energy</li><li>Economic benefits through the use of geothermal energy for local infrastructure</li></ul></td></tr></tbody></table>

**Case Study 7.1: Iceland**

Volcanic and hydrothermal tourist attractions are an important part of the visitor experience in Iceland. The geysers at Haukadalur and the hot springs at Landmannalaugar and Hveragerði are commonly included in trip agendas. The Blue Lagoon, not far from the capital Reykjavik and the Mývatn Nature Baths in Iceland's north-east are unique bathing pools fed by excess geothermal water from the neighbouring power stations Svartsengi and Krafla. In fact, tourists can visit most of the Icelandic geothermal power plants and learn about the generation of clean renewable energy. "With more than 100,000 visitors a year, the geothermal power plants and related installations in Iceland are one of the top tourist destinations in Iceland" (Think Geoenergy 2015).

**Case Study 7.2: Rotorua—New Zealand**

While tens of thousands of people safely visit New Zealand's geothermal parks each year, tragic accidents can happen. In 2010 a ten-year old boy died after falling into one of Rotorua's hot water pools (NZ Herald 2013). According to eye witnesses the boy had burns from his head to his feet and was flown to a hospital in Auckland to be treated in intensive care, but later died (BBC News 2010). Following the accident, Rotorua District Council reviewed the park's safety and added 60 new warning signs as well as additional fencing. However, according to council officials, visitors are frustrated when there are too many

fences, and climb over for a better view (TVNZ 2012). An inquest later found that the boy had climbed a wall and fell into one of the hot pools, suffering burns to almost 100% of his body.

Geothermal water is used worldwide as a renewable resource for generating energy, commercial, agricultural and industrial purposes, space heating, bathing and rehabilitation as well as for drinking and cooking. At Yellowstone (USA) Native Americans have historically used hydrothermal features for food preparation. Today geothermal cuisine is regularly used as a tourist attraction at many active volcanic and hydrothermal destinations. In New Zealand tourists can visit natural cooking pools such as Ngāraratuatara (Rotorua) and observe ancient Māori cooking techniques. In Iceland geothermal or "geyser cooking" is attractive to tourists, with a restaurant in Hveragerði specialised in geothermal cuisine using steam from volcanic activity. On the volcanic islands of the Azores one of the most remarkable tourist attractions of Furnas (San Miguel) is geothermal cooking, offering typical Azorean cuisine at many local restaurants. Hot spring cooking is equally popular in Japan with jigoku-mushi one of many sought after dishes prepared using geothermal steam. Apart from these well-known examples, many countries worldwide, including Kenya, the Philippines, Mexico and Indonesia, use geothermal water for cooking.

On account of their proximity to active volcanism, the management of tourist areas with underlying hydrothermal systems is therefore not an easy task. Given the potential hazards of
active environments, both volcanic and hydrothermal, it is essential that sufficient warnings and safety guidelines are available and emergency procedures and crisis response resources have been prepared along with appropriate channels for effective communication.

## 2.2 Potential Hazards—Beauty or Beast?

Although hydrothermal areas are attractive to visitors, there are a number of inherent hazards and risks. Depending on the magnitude, explosions of super-heated water and steam mixed with fractured rocks and hot mud can be violent enough to create craters varying in size from a few metres to several hundred metres in diameter. Apart from the unexpected eruptions of hydrothermal vents with the potential to cause thermal burns, further risk factors include seismic activity such as earthquakes and lethal gas emissions, as well as ground instability through hydrothermal alteration.

Considering the number of hydrothermal hazards (Table 7.1) it becomes clear that there is indeed a possibility for accident and injury, despite the fact that fumaroles, geysers and bubbling mud pools present such a picturesque photo opportunity. Adding to the list of potential problems is the frequent underestimation of the safety risk from nearby active volcanoes, where circumstances can quickly change in case of unexpected eruptions. Failing to seek information about current activity levels prior to visiting such areas, or not following warnings, can lead to serious injuries or death as many people are not aware of the various hazards they may encounter in these environments.

While life-threatening hydrothermal eruptions are relatively rare, toxic fumes and gas emissions are rather common in active areas. These naturally occurring gases are emitted from volcanic craters and fumaroles or diffused through the soil (Hansell et al. 2006). Toxic gas emissions can also occur in the absence of eruptive activity. Some of the most common gases include

Hydrogen Sulphide ($H_2S$), Carbon Dioxide ($CO_2$) and Sulphur Dioxide ($SO_2$). All of these are dangerous to human health with $H_2S$ causing instant death at extreme levels (Case Study 7.3).

**Case Study 7.3: Akita, Japan**

In December 2005 a family of four tragically died near a hot spring resort from hydrogen sulphide poisoning. While playing two young boys tried to retrieve their Frisbee from a snow covered hollow, unaware that the depression in the ground contained a lethal concentration of $H_2S$. When both children suddenly collapsed their mother tried to save them, but also died instantly after inhaling the toxic gas. When searching for his family the father discovered them lying on the ground and also entered the hollow. He initially survived, but passed away a day later in hospital (Japan Times 2005).

Being denser than air $H_2S$ can accumulate in low lying areas such as hollows and depressions in the landscape and remain trapped if not dispersed by wind (USGS¹ 2014, Whittlesey 2014; Williams-Jones and Rymer 2000). Although $H_2S$ at low levels has a distinctive odour often described as rotten egg smell, at higher concentrations this gas cannot be detected through smell which means there is no warning.

In Hawai'i tourists regularly visit the Hawai'i Volcanoes National Park to observe the glowing lava flows. A special attraction is the area where the lava flows enter the ocean, instantly boiling the seawater and turning it into vapour (Hansell et al. 2006; Heggie et al. 2010; Williams-Jones and Rymer 2000). This chemical interaction between molten lava and sea water creates a white plume known as lava haze or *LAZE* and is frequently mistaken for a 'harmless' steam cloud. This plume however contains a mixture of hydrochloric acid (HCl) and concentrated seawater with up to 2.3 times average salinity and
with pH levels as low as 1.5–2.0 (Heggie et al. 2010; USGS¹ 2014). As a precaution the USGS information website (USGS² 2014) clearly advises people not to stand beneath the volcanic laze plume or downwind of it because hydrochloric acid is toxic and can cause irritation of the throat, lungs, eyes, and nose. In fact, volcanic laze is dangerous enough to kill (Case Study 7.4).

**Case Study 7.4: Clouds that can kill—
Acidic LAZE plumes**

During November 2000 in the Hawai'i Volcanoes National Park two people were caught in a volcanic laze plume near the point where lava flows enter the ocean and died as a result of pulmonary oedema caused by inhalation of volcanic laze. Conditions near this point involved the threat of exposure to dense hydrochloric acid mist, which subsequently engulfed the victims in an extremely hot and acidic cloud. Nevertheless, the area can be accessed without restrictions, although warning signs and safety instructions should never be ignored (Heggie et al. 2010).

Hydrothermal areas for example in Japan, New Zealand or at Yellowstone warn visitors about the risk of encountering unstable ground, as hydrothermal features may only be covered by a thin crust that easily breaks underfoot, and may cause thermal burns (Case Study 7.5; Fig. 7.1).

Unexpected hydrothermal eruptions can become a serious danger also, causing impact injuries and burns from scalding steam emissions, hot mud and ejected rocks. Hydrothermal steam discharge from fumarolic vents can suddenly increase without warning, or steam plumes can change their direction with the wind, which can result in thermal burns as well as respiratory problems. Likewise, a sudden change in the water temperature of hot streams, rivers and lakes, where geothermal spring water mixes with cooler water, can result in serious injuries if people take a soak in what they initially perceive as warm water.

**Case Study 7.5: New Zealand—
Geothermal Wonderlands**

New Zealand's hydrothermal sites provide walkways for tourists in potentially hazardous areas. Boiling lakes, geysers, mud pools, and especially areas of unstable ground are fenced off to reduce the risk for accidents and injury due to underlying geothermal activity. This practice protects both the tourists and the mineral deposits which are part of the attraction of hot springs (Roscoe 2010). However, there is still a need for multilingual warning signs at hydrothermal destinations to increase awareness about potential hazards and visitor safety.

<figure><img src="image_39.png" /><figcaption>**Fig. 7.1** Examples of warning signs at popular North American hydrothermal tourist destinations. The use of pictures or symbols is effective and recommended if there</figcaption></figure>

is the lack of warnings in several languages (Compare Figs. 7.2, 7.3, and 7.4). Source Public Domain
<figure><img src="image_40.png" /><figcaption>**Fig. 7.2** Examples of warning signs in Japan and Iceland. The effort to communicate hazards to international visitors is obvious and commendable, while at the same time adding urgency to the warnings. Source Patricia Erfurt-Cooper</figcaption></figure>

Other risks involve the unexpected change of location of the hot water source, especially if these are located below the surface of a stream of lake. The sudden change of flow rates, direction and currents of the hot water source is another hazard and a risk that people frequently underestimate. The temperature of hydrothermal features such as erupting geysers can also be underestimated from a distance, which can result in thermal burns on approach.

Another important health hazard involves disease-causing organisms such as thermophilic microbes and bacteria. Legionella bacteria and Naegleria fowleri have been identified at thermal pools used for recreation (Fig. 7.3) with some hydrothermal locations reportedly having problems with Primary Amoebic Meningoencephalitis (PAM), a rare but life-threatening infection caused by the organism Naegleria fowleri (Erfurt-Cooper and Cooper 2009). While casual exposure via the skin does not result in infection, the inhalation of contaminated water can cause serious problems, as the pathogenic amoebae migrate up the sinuses and surrounding tissue to the brain (Barnett et al. 1996). A common hot pool safety warning in New Zealand advises that "When swimming in natural hot pools, where the water comes out of the ground, keep your head above water because there is a small risk of contracting an illness called amoebic meningitis. While very rare, this illness is serious".

Public bathing facilities in the form of hot spring pools are often also accessible in hydrothermal areas. Bathing accidents are not unusual at natural hot springs, thermal health spas and geothermally heated communal pools. Being generally careless or consuming alcohol prior to using hot spring pools shows a lack of common sense and ignorance of safety advice, but is unfortunately all too common. In general, developed hot spring spas and pools advise visitors on the risk of excessive soaking in hot water when suffering from certain health conditions.

# 3 Communicating, Forecasting and Managing Natural Hazards—A Mission Impossible?

## 3.1 The Main Challenges of Hazard Communication

Hazard education and risk communication are an essential foundation for effective risk management (Leonard et al. 2008; Paton et al. 2001) with the aim to prevent harm through injury or death, while crisis communication focuses on informing the public during a crisis event (Leonard et al. 2008; Steelman and McCaffrey 2013; Williams and Olaniran 1998). To maximise the effectiveness of warnings, signage plays a critical role in increasing hazard awareness of the public
<figure><img src="image_41.png" /><figcaption>**Fig. 7.3** Bilingual sign at a thermal pool warning visitors of the risk of contracting amoebic meningitis. *Source* Public Domain</figcaption></figure>

(Dengler 2005; Leonard et al. 2008). Visitors of hydrothermal and volcanic environments may be aware of potential hazards, but once an emergency situation develops, reaching people in remote locations can be fraught with problems. Apart from the geophysical hazards, a number of additional challenges at hydrothermal tourist sites also have to be considered (Table 7.4).

While effective communication starts with essential warning signage in hazardous areas, warnings, safety instructions and hazard maps, if ignored, can result in the loss of lives. The reliance on smart phones and a potential lack of reception is a further challenge in achieving effective communication. Some of the biggest problems in hazard communication however are language barriers, with more signs displaying multilingual warnings and effective symbols or pictograms needed at many hydrothermal tourist destinations.

Another main difficulty is to keep a record about the exact numbers of people present in an affected area during a crisis situation. Uncertainty over the whereabouts of tourists (hikers, climbers etc.) can cause preventable fatalities if there is insufficient time to reach all affected people under deteriorating conditions. This is complicated by the fact that predictions and/or forecasts of hazardous activity can often only be made based on the frequency and the type of past hazardous activities of a particular area. To realistically forecast future activity and determine which area may be subject to potential threats is only possible if the site is constantly monitored and assessed. Scientists can advise on possible danger zones and create hazard maps in cooperation with local authorities to show unsafe and safe areas, escape routes and shelters, but this is at best only a probability assessment.
<table><caption>**Table 7.4** Challenging factors related to hazards in active hydrothermal environments</caption><thead><tr><th colspan="2">Potential problems at hydrothermal tourist sites</th></tr><tr><th>Challenging factors</th><th>Examples/Consequences</th></tr></thead><tbody><tr><td>Remote areas</td><td>Uncertain visitor numbers<br>Uncertain access and escape routes<br>Rescue response delayed or impossible</td><td>Valley of Geysers, Kamchatka, Russia</td></tr><tr><td>Large areas</td><td>Monitoring visitors difficult<br>Emergencies can go unnoticed</td><td>Yellowstone, USA (Case Study 7.8)</td></tr><tr><td>Large crowds</td><td>Crowd control to avoid panic<br>Unknown and/or blocked escape routes</td><td>Hydrothermal parks (New Zealand) (Case Study 7.5, 7.7 and 7.9)<br>Yellowstone (USA)</td></tr><tr><td>Confined spaces</td><td>Blocked escape routes<br>Potential of panic causing injuries</td><td>Small hydrothermal parks or Jigoku (Japan) (Case Study 7.6)</td></tr><tr><td>Communication barriers</td><td>Insufficient warning signs<br>Lack of emergency information<br>Lack of mobile phone reception</td><td>Areas with limited or no communication infrastructure, remote areas</td></tr><tr><td>Language barriers</td><td>Signage does not communicate warnings effectively</td><td>Tourist sites only using signs in the local language</td></tr><tr><td>Lack of shelters or difficult access to shelters</td><td>Shelters not built strong enough to protect from eruption fallout or from toxic gas emissions</td><td></td></tr><tr><td>Transport logistics in crisis situations</td><td>Access for rescue and transport of injured people in remote locations<br>Treatment and medical care</td><td></td></tr><tr><td>Time factor</td><td>Sudden onset of crisis</td><td></td></tr><tr><td>Political</td><td>Access limited or prevented during times of political instability<br>Cross-border disagreements</td><td>Erta Ale and Dallol Hydrothermal Field (Ethiopia)</td></tr><tr><td>Financial</td><td>Lack of funding to implement safety strategies<br>Economic mismanagement</td><td>Affects emergency management, strategic planning and rescue response</td></tr><tr><td>Topography</td><td>Extreme terrain and physical surface features</td><td>Area is difficult to negotiate due to environmental factors</td></tr><tr><td>Sudden weather changes</td><td>Additional natural hazards such as strong wind, rain, snow, temperature drop</td><td>Can affect any region<br>Disadvantage for rescue missions</td></tr><tr><td>Human resources</td><td>Lack of trained staff, unpreparedness<br>Lack of emergency response teams</td><td></td></tr><tr><td>Technical problems</td><td>Equipment failure, power outage</td><td></td></tr></tbody></table>

Risk management is based on the monitoring of potentially hazardous areas, and restricting access when for example toxic gas emissions reach dangerous levels. Unfortunately, areas at risk quite often lack the necessary funding to install permanent monitoring equipment (Williams-Jones and Rymer 2000). Table 7.4 lists the major factors that can determine success or failure in crisis communication and emergency management.

**Case Study 7.6: Japanese Jigoku—Hellish Experience**

In the centre of Beppu City on the Japanese island of Kyushu ten small geothermal parks are located. Thousands of tourists visit these parks known as jigoku, which means ‘hell’ in Japanese, on a daily basis, with many tour groups arriving by bus. There are a variety of geothermal features,
including a small turquoise crater lake fed by a permanent geyser (Umi Jigoku or Sea Hell), a steaming red pond known as Blood Hell (Chinoike Jigoku), the Priest Hell with bubbling mud ponds (Onishi Bozo Jigoku), the White Hell ponds (Shiraike Jigoku), and others, all of which are popular tourist sites. For the safety of visitors, the boiling lakes are fenced off and warning signs are located at all hazardous features (Fig. 7.4). Public announcements update visitors on important issues of the individual sites and friendly staff members are always around talking to visitors and guiding them from one geothermal feature to another (e.g. Kamado Jigoku). Safety is rarely an issue as Japanese regulations are very strict. Seismic activity and pressure in the underlying hydrothermal system are constantly monitored due to their location in the volcanic dome complex of Mt Tsutumi, which is classed as an active volcano. Also, hazard communication in Japan has over the past decade been extended to include several languages based on increasing number of foreign tourists. Other ‘hellish’ locations in Japan include Jigokudani near Noboribetsu on the island Hokkaido and the Unzen Jigoku near Shimabara (Kyushu).

Reaching people in an emergency to rescue them or guide them to a safe area depends on access to the affected site and transport options for evacuation. While a crisis is in progress, weather changes can hinder rescue efforts or make them impossible. For example, during the hydrothermal eruption of Mt Ontake (Japan 2014) rescue workers and Self Defence Force helicopters were carrying injured people to safety, but were battling adverse weather conditions as well as communication problems when trying to locate missing people. This disaster was made worse by not recording visitor numbers as should be done at all active volcanic and hydrothermal areas, although this is difficult logistically.

Further challenges to hazard communication, apart from the already mentioned lack of monitoring facilities at remote or underfunded destinations, include visitors blatantly ignoring warning signs and safety announcements. The co-operation of key stakeholders (e.g. scientists, authorities, tourist organisations) also remains difficult and can result in the lack of sufficient and effective emergency management strategies. Paired with procrastination this can delay the required decision making processes, and the timing of when to warn the public of an imminent danger. This is especially if the crisis situation is exacerbated by unfavourable factors including remoteness, large crowds, an ensuing panic or the threat of bad weather together with low visibility and hostile temperatures.

<figure><img src="image_42.png" /><figcaption>**Fig. 7.4** Warning sign in two languages at a boiling pond at one of Beppu's Jigoku. Photo Patricia Erfurt-Cooper</figcaption></figure>
## 3.2 How Are Hazards and Risks in Hydrothermal Areas Communicated to the Public?

Advising the public of an imminent crisis is generally the responsibility of a local authority, based on the information supplied from scientists monitoring an active area (McGuire et al. 2009), or casual observation. The capacity to communicate safety advice in case of a developing crisis situation depends on a range of factors. Above all the time frame is critical; the sudden onset of a hazardous situation can translate into life-threatening injuries.

Communication of hazards and risks can take place in several ways (Table 7.5). Prior to visiting, people interested in active hydrothermal or volcanic areas certainly have the opportunity to secure information about their chosen destination. While literature about many active environments is available and can be researched at libraries, the most effective way to access up-to-date information is to use reliable online sources for individual destinations (Case Study 7.7) and to check for current conditions and alert levels.

### Case Study 7.7: New Zealand

The Waimangu Volcanic Valley is promoted on the internet as “amazing thermal features combined with lovely bush walks” with “hot springs, steaming lakes and colourful mineral deposits” (Waimangu Volcanic Valley 2015). Not promoted is advice on safety and instructions for emergencies. The “All you need to know” section offers “General information” about guided and self-guided tours and refers to “Guide sheets” in nearly a dozen languages. A brochure covering the area describes Waimangu Valley as “the world’s youngest geothermal ecosystem, home to many geothermal features of worldwide importance” refers briefly to sustainable management practices including “safe access to the best viewing points”. Information related to potential hazards is not always communicated on websites or brochures. However, after contacting the management at Waimangu it was clarified that safety is a very serious issue with strategies in place for all possible events. Great emphasis is placed on

<table><caption>**Table 7.5** Availability of information about hydrothermal (and volcanic) hazards before, during and after visiting</caption><thead><tr><th>Communication channels and their application</th><th>Before</th><th>During</th><th>After</th></tr></thead><tbody><tr><td>Internet sites of destination (e.g. regular updates, alert levels, webcams)</td><td>x</td><td></td><td>x</td></tr><tr><td>Literature (earth science books and journals, guides books, research papers)</td><td>x</td><td></td><td>x</td></tr><tr><td>Brochures, fact sheets (park management, tourist offices)</td><td>x</td><td>x</td><td>x</td></tr><tr><td>Maps, hazard maps with safety instructions</td><td>x</td><td>x</td><td></td></tr><tr><td>Visitor centres, interpretive centres, science museums</td><td>x</td><td>x</td><td></td></tr><tr><td>Videos (visitor information, safety advice)</td><td>x</td><td></td><td></td></tr><tr><td>Documentaries (related to natural crises)</td><td>x</td><td></td><td>x</td></tr><tr><td>Rangers, tour guides</td><td>x</td><td>x</td><td></td></tr><tr><td>Social media (fb, twitter, trip advisor) real time updates</td><td>x</td><td>x</td><td>x</td></tr><tr><td>General media (TV, radio)</td><td>x</td><td></td><td>x</td></tr><tr><td>Public address systems where installed</td><td></td><td>x</td><td></td></tr><tr><td>Smart phone apps (if any have been developed)</td><td>x</td><td>x</td><td>x</td></tr><tr><td>Subscription to text messages, real time updates</td><td></td><td>x</td><td></td></tr></tbody></table>
trained staff and all visitors are briefed on arrival at Waimangu to stay safe. Some of the guidelines include staying on the paths at all times and following the directional signs. Written interpretations given to visitors contain further safety messages (pers. email communication with H. James CEO Waimangu). Based on further personal experience from previous visits of geothermal destinations in New Zealand staff at visitor centres and rangers/guides are available to advise on safety and potential dangers and are trained to respond to emergencies.

To communicate potential hazards, some National Parks show visitors introductory videos, hand out brochures, explain safety procedures and advise to strictly obey warning signs. The Hawaii Volcanoes National Park shows informational videos about safe conduct near active features prior to entering the Park to warn people in advance about the various hazards they can encounter. These measures cannot be enforced however, with some visitors to hazardous areas choosing to ignore them. Nevertheless, effective hazard communication is possible; an example is to be found at Mt Aso (Kyushu, Japan), where during visits to the summit public announcements in four different languages constantly update tourists about the level of toxic gas emissions from the crater and whether this poses a risk for visitors on the viewing platform and the surrounding walkways. Evacuation of the area is carried out immediately if the wind direction changes and the situation becomes hazardous for visiting tourists.

Another positive example is found in the Yellowstone National Park, USA, where the emphasis is firmly on public safety to avoid accidents and injuries from hydrothermal features, which have led to fatalities in the past (Case Study 7.8).

## Case Study 7.8: Yellowstone—10,000 geothermal Features and 3 Million annual Visitors

Yellowstone National Park's chief safety officer says that they “try to educate people starting when they come through the gate” and that it is important for parents to keep a close eye on their children when visiting thermal areas. Prior to visiting the Yellowstone website informs people that “wild animals are not the only dangerous threat in Yellowstone”, and that there have been a significant number of “deaths and injuries from geysers and geothermal water” over time. While the geothermal features are known to be hazardous, park management is concerned that visitors and even employees are not aware or ignorant of the potential risks when leaving designated walkways (Yellowstone 2014). According to Whittlesey (2014) there have been 19 confirmed human fatalities in Yellowstone's history as a national park from falling into thermal features including children, adults and even people working in the park. Safety managers at Yellowstone also think that incidents of injuries are higher than reported, because people cannot resist testing the water temperature by putting in their fingers or toes and suffer thermal burns. Warnings related to the dangers of geothermal hazards are clearly communicated on Yellowstone's website and are a good example of informing the public ahead of visiting. Throughout the geothermal areas there are warning signs and rangers are trying their best to keep unwary tourists from endangering themselves (Yellowstone 2014).

## Case Study 7.9

The Waikato Regional Council (New Zealand) monitors geothermal sites and develops specific hazard maps for the Waikato region. For visitors to geothermal
areas the Waikato Council offers some
guidelines on their website about potential
hazards and how to avoid them:

- Always check the temperature of the water before putting any part of your body in it. Take care not to fall in the water unless you are sure the temperature is safe.

- Keep your head above the water when bathing in geothermal pools. If you have severe flu-like symptoms within a week after visiting a hot pool, see a doctor immediately to rule out amoebic meningitis.

- Don't drink geothermal water in case it contains the toxic minerals arsenic and mercury.

- Be wary of eating trout caught in geothermal streams and lakes, as these fish may contain high levels of mercury.

- Keep a safe distance away from boiling mud pools, geysers and other areas which may suddenly erupt. Remember, a safe distance may be greater than you think, due to the unpredictable size and frequency of these geothermal features (Waikato Regional Council 2014).

Nevertheless, every country has their own methods and legislations how to deal with complex health and safety tasks emerging during crisis situations in relation to hydrothermal hazards. Based on the type of hazard, appropriate crisis management should include strategies for any level of emergency, including preparations for the evacuation of tourists and host communities if necessary. Hence, courtesy of the advanced media coverage we have come to rely on, hazard and crisis communication has far more opportunities to reach the public than even only one or two decades ago. And an abundance of information is available for those who are willing to do some research before embarking on a trip into a potentially hazardous area. However,

the above listed methods of hazard communica-
tion are not always taken advantage of and they
may not all be available for a particular site or
destination.

4 Hazard and Crisis Communication

4.1 Alerting the Public—
Communicating Warnings

As mentioned above, the communication of hazards is legally at the discretion of the official management in charge of public safety. Depending on the hydrothermal activity level, appropriate signage and fencing are essential to warn and protect the public under normal conditions. During a crisis situation accurate and up-to-date information about an imminent danger is one of the key elements of effective communication. Difficulties in translating data from monitoring scientists into relevant facts followed by an appropriate course of action can however affect the successful management of an emerging crisis situation (Jolly and De La Cruz 2015; Gregg et al. 2015; McGuire et al. 2009).

In the build-up to a crisis warnings are dis-
seminated through local media outlets (TV,
radio, newspaper, website updates). Prior to and
during a crisis emergency advice and directions
can be communicated through rangers and tour
guides, assisted by hazard maps and fact sheets.
To communicate alert levels in real time colour
coded warning lights and public announcement
systems are suitable methods to reach tourists in
large or remote areas with volcanic and
hydrothermal activity. Finally, depending on the
actual area, rescue workers and emergency per-
sonnel on site should be available to assist the
public. Mobile phone message subscriptions and
digital Apps are increasingly playing a part in
reaching people prior and during emergencies,
which shows that text messages carrying infor-
mation about geo-hazards can be communicated
to registered users in real time. To avoid misin-
terpretations Ghosh et al. (2012) note that “a
generalized system that could be deployed for
any geo-hazard across any region” should be
developed. However, as many hydrothermal tourist destinations are located near active volcanoes, alert level systems as described in detail by several scientists (Fearnley et al. 2012; Gregg et al. 2015; Jolly and De La Cruz 2015; McNutt 2015; Williams-Jones and Rymer 2015) could possibly be modified and implemented at hydrothermal sites where required.

## 4.2 The Main Stakeholders and Their Responsibilities

As with volcanic environments planning for hydrothermal areas includes consultation and discussion between all stakeholders (Gregg et al. 2015). To communicate potential hazards to stakeholders (Connor et al. 2015), prior education through ranger talks, videos, brochures, and the internet can prepare visitors for the need of hazard and crisis communication in hydrothermal areas by raising their awareness. At the first signs of an emerging crisis situation, effective and reliable communication must be established between the stakeholders to develop a strong working relationship to cope with the crisis as it unfolds. While the most important stakeholder group in terms of tourism are the **visiting tourists**, three main stakeholder groups are identified by McGuire et al. (2009): the monitoring scientists, the emergency managers, and the media. However, local authorities and resident communities also constitute important stakeholder groups at hydrothermal tourist destinations. Heath et al. (2009) acknowledge that stakeholder partnerships, which include the public are the key to effective hazard and crisis communication.

Monitoring scientists are responsible for detecting early warning signs and assessing activity levels to provide information and guidance in an emergency situation. The role of emergency management committees is to determine an appropriate response strategy based on such scientific data, to develop hazard maps and risk management strategies and to take a pro-active role in educating the public about the nature of the emergency situation (Gregg et al. 2015; McGuire et al. 2009). To prevent

misunderstandings that may result in misinterpretation and delay in the decision making process in a crisis situation, it is critical that the communication between scientists and all other stakeholders is clear and unambiguous (Doyle et al. 2014). The media then should focus only on information, which is specific to the situation and present warning messages in a form that is clearly understood by everybody. To convey information effectively all irrelevant data should be avoided in media releases as it can confuse the public (Leonard et al. 2008; McGuire et al. 2009; Sorensen 2000). Warning messages should be consistent and designed to include those with poor literacy, language problems or disabilities effectively in the information stream. Pictures, drawings and video footage are useful ways to communicate with international visitors, and at the same time avoid confusion with terminology (Erfurt-Cooper and Cooper 2010, Erfurt-Cooper 2014; McGuire et al. 2009).

Scientists sometimes may be reluctant to communicate scientific information to other stakeholders based on their experience of misinterpretation or selective use of their data (Boykoff 2008). While there have been advances in the field of communicating geo-hazards, much needs to be done to improve the engagement between all stakeholders (monitoring scientists, politicians, government agencies, emergency managers, representatives of the media, and the public) to ensure seamless co-operation and effective communication (Liverman 2010; McGuire et al. 2009).

# 5 Hazard Management

## 5.1 Why Are People Reluctant to Respond to Warnings?

An emergency situation in areas of hydrothermal activity can be caused by a natural event and affect many people, but very little can be done to prevent it from happening. Disaster preparedness can offset some of the hazards in this situation, but not all. However, another type of emergency is caused by humans who are frequently injured
as a result of being careless, and this situation can
be avoided. In the Yellowstone National Park for
example accidents and injuries are nearly always
due to visitors being irresponsible in thermal
areas with a number of reasons for injuries
identified by Whittlesey (2014):

* Walking in off-limit areas

* Walking in darkness

* Losing balance

* Being intoxicated

* Being distracted

* Over-confidence

* Ignoring warnings

* Careless running

Whittlesey (2014) rightly points out that “*a balance is needed between adequate warnings and basic responsibility from the visitor*”. Individuals, who choose not to respond to hazard warnings or worse, in a crisis situation may not do so because (a) they are unfamiliar with the hazard, or (b) they think they can avoid the hazard altogether, while (c) others believe it could be a false alarm, and (d) if not, somebody will come to their rescue.

One of the key factors influencing the decisions of individual people in these situations is their personal risk perception, which can range from being overcautious to ignoring a potential risk, or to the complete denial of any danger. In addition, apart from a possible uncertainty about the risk, a negative attitude towards authorities could be another reason for ignoring safety advice. Furthermore, tourists frequently overestimate their personal ability to cope with dangerous situations while at the same time underestimating the actual risk and their own vulnerability. Here it would be advisable to provide all visitors of active hydrothermal environments with detailed safety guidelines, which they should refer to before and during their visit.

Virtual reality is in this day and age a valuable
tool for travel planning and the internet offers
many sources to assist detailed research of
planned destinations including webcams, videos
and computer simulations. While cyber visits to
extreme landscapes and hazardous areas may

lack the actual risk, they can help visitors and
host communities to understand the potential
difficulties as well as the risks that can be
encountered in the real world (Erfurt-Cooper and
Cooper 2009). However, despite the advent of
real-time internet resources, the task of hazard
and risk management in volcanic and
hydrothermal environments remains extremely
challenging, as varying degrees of potential
danger from hydrothermal activity as well as
correlated volcanic and seismic events generate
different types of hazards (Erfurt-Cooper and
Cooper 2009).

## 5.2 Why Are Authorities Reluctant to Announce Evacuations?

Not being aware of the potential hazards in an
active area prior to visiting could mean the dif-
ference between safety and injury. So, if this is
true, and if maintaining a high level of commu-
nication means that public warnings are the
responsibility of the authorities (McGuire et al.
2009), why are some authorities reluctant to
announce evacuations? As suggested by Francis
and Oppenheimer (2004), all details of risk
management strategies need to be planned and in
place, including successful evacuation, transport
and medical care. However, this may not be
common knowledge, as for the tourism industry
disasters are generally bad for business. Thus, if
warnings are given too early, they might be
ignored by the public, or in the case of repeated
warnings without anything happening they may
also be ignored (the cry wolf syndrome). Nev-
ertheless, to avoid endangering the public, good
management strategies are required to assist with
hazard communication, crisis planning and to
prevent emergency situations getting out of hand.

When it comes to the drastic measure of
calling an evacuation, authorities may be reluc-
tant to do so for several reasons. Uncertainty
about the actual risk combined with a lack of
scientific knowledge and experience on the part
of some stakeholders can make the decision
making process difficult. In the case of insuffi-
ciently trained staff and/or in the absence of
monitoring facilities the reliable assessment of imminent danger can be impossible. Emergency managers and response teams can also have their tasks complicated by unfavourable logistics based on remote terrain, weather, lack of time and/or inadequate strategies. When local authorities are incapable of dealing with emergencies, external rescue response teams may have to be called in to assist, which again may delay the decision to evacuate. Occasionally political disagreements such as cross border problems can come into play, presenting another reason for making hazard communication and crisis management including successful evacuation unworkable.

To generate effective and accurate communication before, during and after a crisis therefore remains a challenge, because it depends on numerous variables. More to the point, hazard communication is mainly focussed on volcanic environments with hydrothermal areas in need of higher levels of targeted research to improve hazard communication and crisis management. If reliable information is not available or is only partial, it becomes obvious how delays in effective crisis response can occur.

# 6 Conclusion

Health and safety issues play a major role in the tourism industry based on hydrothermal and volcanic resources (Erfurt-Cooper 2008, 2010, 2014). While it is essential to prevent injuries to tourists the management of effectively communicating hydrothermal hazards remains problematic. Precursory signs indicating a dangerous natural event are still not completely understood and the communication of imminent danger is frequently unachievable. As a consequence, serious thought needs to be given to improvements in the communication of risk factors and potential dangers from the proximity of active hydrothermal surface features, including extreme hot springs and geysers, as well as areas affected by hydrothermal alteration resulting in unstable ground properties.

To reduce the risk factor, it is essential to raise visitor awareness about any potential hazards in hydrothermal tourist areas and put management strategies for emergencies in place. Advice for visitors of active hydrothermal environments should include guidance and recommendations how to cope with extreme events in difficult situations (Erfurt-Cooper 2008, 2010, 2014). To improve the safety standards in these areas, strategic guidelines for safe conduct should cover all active hydrothermal areas and must be designed to be understood by every visitor. In seeking to achieve this ideal state, one of the questions arising is whether visitors to these areas seek enough information from available sources prior to their journey (Appendices 1 and 2). However, the overall hazard, risk and crisis communication process for active hydrothermal environments is a problem, which frequently is insufficiently addressed at tourist destinations. While some areas have taken steps to educate visitors about potential dangers the moment they arrive (Yellowstone 2014), other areas do not offer adequate safety information. Here virtual reality can be a valuable tool for travel planning with the internet offering numerous comparable sources (e.g. webcam, videos and computer simulations) to research planned destinations.

This chapter has presented an overview of the most common hazards or risk factors in hydrothermal areas with brief case studies to exemplify different scenarios. To highlight the challenges of risk management and the need for effective communication a number of locations were discussed for their site specific hazards and their potential risks. The literature reviewed for this chapter indicates a scarcity of research for hazard communication in hydrothermal areas and hence information related to this topic remains limited. In conclusion, it is recommended that more studies are undertaken to contribute to the safety of visitors in these environments and that more destination websites include safety advice relating to their hydrothermal tourist attractions.
# Appendix 1

Example of safety advice—extract from USGS factsheet (USGS³ 2007).

U.S. Geological Survey and the U.S. Forest Service—Our Volcanic Public Lands.

Boiling Water at Hot Creek—The Dangerous and Dynamic Thermal Springs in California's Long Valley Caldera.

This Fact Sheet and any updates to it are available online at http://pubs.usgs.gov/fs/2007/3045.

## VISITING HOT CREEK SAFELY

Visiting Hot Creek can be an enjoyable and rewarding experience, but you should be aware of the dangers and take them seriously. Know the hazards—boiling or scalding water, steam vents, unstable ground and boulders, hot ground or mud, swiftly flowing water, a stream with unpredictable currents, and water unfit for human consumption.

**Follow these tips for your safety:**

* Keep a clear head and be observant—conditions can change quickly.

* Keep careful watch on children and pets (always keep pets on a leash).

* Follow directions and warnings on signs.

* Don't cross over fences or barriers, and stay on walkways.

<figure><img src="image_43.png" /></figure>

**How to get there:**

The Hot Creek Geologic Site is located northeast of the Mammoth-Yosemite Airport and is accessed from U.S. Highway 395 by the Hot Creek Hatchery Road.
**Appendix 2**

HAZARDOUS EVENTS AT YELLOWSTONE

Scientists evaluate natural-hazard levels by combining their knowledge of the frequency and the severity of hazardous events. In the Yellowstone region, damaging hydrothermal explosions and earthquakes can occur several times a century. Lava flows and small volcanic eruptions occur only rarely—none in the past 70,000 years. Massive caldera-forming eruptions, though the most potentially devastating of Yellowstone's hazards, are extremely rare—only three have occurred in the past several million years. U.S. Geological Survey, University of Utah, and National Park Service scientists with the Yellowstone Volcano Observatory (YVO) see no evidence that another such cataclysmic eruption will occur at Yellowstone in the foreseeable future. Recurrence intervals of these events are neither regular nor predictable.

<figure><img src="image_44.png" /></figure>

How Dangerous Is Yellowstone?

None of the events described above—cataclysmic caldera-forming eruptions, lava flows, large earthquakes, or major hydrothermal explosions—are common in Yellowstone. Although visitors to Yellowstone National Park may never experience them, some hazardous events are certain to occur in the future. Fortunately, systematic monitoring of Yellowstone's active volcanic and hydrothermal systems, including monitoring of earthquakes and ground deformation, is now carried out routinely by YVO scientists.

This monitoring will allow YVO to alert the public well in advance of any future volcanic changes in the patterns of ongoing seismicity or other indicators of possible geologic unrest are quickly reported to officials responsible for public safety in the National Park Service and other agencies.

Through continuous monitoring and research, YVO is greatly improving understanding of

Yellowstone's volcanic, earthquake, and hydrothermal hazards. The work of USGS scientists with YVO is only part of the USGS Volcano Hazards Program's ongoing efforts to protect people's lives and property in all of the volcanic regions of the United States, including California, Hawaii, Alaska, and the Pacific Northwest (Lowenstern et al. 2005).

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Mapping Hazard Zones, Rapid
Warning Communication
and Understanding Communities:
Primary Ways to Mitigate Pyroclastic
Flow Hazard

Franck Lavigne, Julie Morin, Estuning Tyas Wulan Mei,
Eliza S. Calder, Muhi Usamah and Ute Nugroho

Abstract

Protection against the consequences of Pyroclastic Density Currents (PDCs) is almost impossible due to their high velocity, temperature, sediment load and mobility. PDCs therefore present a challenge for volcanic crisis management in that specific precautionary actions, essentially evacuations, are required to reduce loss of life. In terms of crisis communication for PDC hazards, there are three challenging questions that arise in terms of reducing risk to life, infrastructure and livelihoods. (1) *How do we accurately communicate the hazardous zones related to potential PDC inundation?* The areas exposed to PDC hazard are difficult to assess and to map. In terms of risk/crisis management, the areas considered at risk are usually those that were affected by PDCs during previous eruptive episodes (decades or centuries ago). In case of “larger-than-normal” eruptions, the underestimation of the hazard zone may lead to refusals to evacuate in the “newly” threatened area. Another difficulty in assessing the PDC hazard zones relate to their transport processes that allow surmounting of the topography and in some cases across the surface of water. Therefore warning systems must be able to cover vast areas in a minimum of time. (2) *How do we efficiently warn people in time?* PDCs are extremely mobile and fast. It is therefore necessary to raise the alert early enough before the onset of the first PDCs. A challenging question in terms of crisis communication is related to the

<footnote>F. Lavigne (✉)
Laboratoire de Géographie Physique,
Université Paris 1 Panthéon-Sorbonne, Meudon,
France
e-mail: franck.lavigne@univ-paris1.fr</footnote>

<footnote>J. Morin
Laboratoire Magmas et Volcans,
Université Clermont Auvergne, CNRS, IRD, OPGC,
Clermont-Ferrand F-63000, France</footnote>

<footnote>E.T.W. Mei
Fakultas Geografi, Universitas Gadjah Mada,
Yogyakarta, Indonesia</footnote>

<footnote>E.S. Calder
School of GeoSciences, University of Edinburgh,
James Hutton Rd, The Kings Buildings, Edinburgh,
UK</footnote>

<footnote>M. Usamah
PYDLOS, Universidad de Cuenca, Cuenca, Ecuador</footnote>

<footnote>U. Nugroho
Universitas Padjadjaran, Bandung, Indonesia</footnote>
type of tools used by the local authorities, modern and traditional tools both of which have advantages and disadvantages. (3) *Why are people reluctant to evacuate?* Local inhabitants can be reluctant to evacuate during a crisis if traditional warning signs or signals they are familiar with are lacking, if they don't receive both traditional and official warning, and because they may lose their livelihoods. Thus a deeper understanding of the at-risk communities and efficient dissemination of information are key issues in order to reduce vulnerability in PDC hazard regions.

**Keywords**

Pyroclastic density currents • Risk communication • Crisis management • Warning • Evacuation • Risk perception

# 1 Introduction

Pyroclastic Density Currents (PDCs) are rapid flowage phenomena that involve various proportions of volcanic gas and fragmented volcanic rock at high temperatures. PDCs encompass dense pyroclastic flows, which tend to be more topographically controlled, and dilute pyroclastic surges that are less topographically controlled and can surmount topographic obstacles, or travel across the surface of bodies of water. Both dense flows and dilute surges destroy almost everything in their path and therefore protection against the consequences of PDC inundation is almost impossible. In some countries, anti-PDC bunkers have been built in high hazard prone areas to provide a safe shelter to a limited number of people in the situation that they are unable to evacuate on time. It was demonstrated in 2006 on Merapi (Indonesia) that they are not always effective, as two people died trapped in the bunkers where they took refuge (Gertisser et al. 2011). Moreover, hard engineering structures such as SABO dams may actually accentuate the avulsion process of PDCs, e.g. in 2006 and 2010 at Merapi (Lube et al. 2011), or Tungurahua in 2006 (Stone et al. 2014). Thus, PDCs present a challenge for volcanic crisis management in that specific precautionary actions are required to reduce loss of life.

The improvement of crisis management capabilities is based, on one hand, on PDC monitoring and early warning systems as well as robust communications that are not likely to be compromised for example by power failure and, on the other hand, on preparedness of stakeholders and population (MIAVITA Team 2012).

This chapter discusses three challenging questions in reducing the risk associated with PDCs: (1) How should we accurately communicate the hazardous zone related to potential PDC inundation? (2) How should we efficiently warn people in time? (3) Why are people often times reluctant to evacuate and how should we improve the propensity for people to accept and undertake evacuations?

These points are addressed through examples, mostly focusing on Merapi, and other Indonesian volcanoes as well as other volcanoes around the world. This chapter concludes with a discussion on ways to improve volcanic risk management in areas prone to PDC hazards.

# 2 How Can We Communicate PDC Hazard Zones?

The areas exposed to PDC hazard are difficult to accurately assess and to map. In terms of risk/crisis management, the areas considered at
risk are usually those that were affected by PDCs during the last decades or centuries. Scientists in charge of volcano monitoring often use a “reference eruption”, the extent of volcanic deposits of which are used to gauge inundation extent for future eruption scenarios in operational hazard maps. For instance, the “danger zones” maps used in Indonesia for emergency planning are provided by the Center of Volcanology and Geological Hazards Mitigation (CVGHM). These maps typically display two zones threatened by PDC hazard: the KRB III (KRB stands for *Kawasan Rawan Bencana* in Indonesian or Hazard Prone Area in English) encompasses areas located close to the summit, frequently affected by dome-collapsed pyroclastic flows, lava flows, rock falls and ejected rock fragments. The KRB II is affected by less frequent and longer runout pyroclastic flows, lahars, volcanic ash fall, and ejected rocks. At Merapi for example, the boundaries of hazard zone III and II were based, until 2010, on the distribution of volcanic products of the largest eruptions of the 20th century. Therefore the maximum distance of the KRB II did not exceed 15 km, which was the approximate maximum extension of the 1930,

1961, and 1969 PDCs. Since its first edition in 1978 (Pardyanto et al. 1978, Fig. 8.1), the volcanic hazards map has been widely disseminated among the communities at risk through the local authorities and non-governmental organizations (NGOs). Although this map was updated following the 2006 eruption (Mei and Lavigne 2012), the contingency plan created in 2009 still did not consider a plinian or subplinian eruption scenario such as the one that occurred in 1872. Several areas affected by the subsequent and devastating 2010 PDCs, the length of which were substantially longer than expected (17 km from the summit), had not been included in the danger zone. As a result 53 people who were resisting evacuation or who were late in the process of evacuating were killed in Bronggang, a village located 13.5 km to the south of Merapi, when dilute surges detached from their parent flows in the adjacent Gendol River and entered the village (Jenkins et al. 2013). Among the survivors, several inhabitants who were unprepared for evacuation took a wrong evacuation route too close to the river (Mei et al. 2013). Since the 2010 eruption, the hazard map has been revised (Fig. 8.1).

<figure><img src="image_45.png" /><figcaption>**Fig. 8.1** The Merapi volcano hazard map designed by the Indonesian Center of Volcanology and Geological Hazard Mitigation (CVGHM) in 2002 (CVGHM 2002) and after its revision in 2011 (CVGHM 2011)</figcaption></figure>
Although the local authorities are often aware of the worst-case scenario provided by the volcanologists, they cannot use it for contingency planning, i.e. for risk management. Using the worst case scenario for a background hazard map is actually impractical since many existing communities are established on deposits from large eruptions, and an eruption is unlikely to reach worst case without some precursory activity. However, all possibilities should be discussed between volcanologists and authorities well before a crisis, so that outline contingency planning can be made if significant escalation does occur. Communities can live within hazard zones, if they are aware of the threat and there is good planning for evacuations in the event of an escalation. Maps are commonly adjusted as a crisis evolves, as shown in the cases of Merapi. During the 2012 Tongariro eruption crisis in New Zealand, Leonard et al. (2014) highlighted the importance and complementary roles of three map types for communicating volcanic hazard information: background hazard, crisis hazard and ashfall prediction maps. In developing hazard maps there are a range of key points to consider in terms of message, presentation and basis for each map type. For example, perspective view has been shown to increase map readability and public self-location accuracy (Haynes et al. 2007b; Nave et al. 2010). Following Leonard et al. (2014), PDC hazards need careful quantification through modelling. For rapid crisis PDC hazard map zone development the critical factors are (1) having access to and experience in running flow models, (2) having those models tested against the past and expected future parameters of a volcano and (3) having access to the computing resources needed to run enough scenarios in a short (day to days) timeframe.

The main difficulty in communicating PDC hazardous zones occurs when the hazard is almost unknown, or has been forgotten by local people over time after a few generations, such as on the slopes of the Mount Pelée on the island of Martinique before the 1902 eruption (Leone and

Lesales 2009). One day before the total destruction of Saint-Pierre by pyroclastic surges, a scientific expert from mainland France claimed that “Saint-Pierre is not more threatened by the Pelée volcano than Napoli by the Vesuvius volcano”. This scientist was not aware that dilute pyroclastic surges could occur at Mount Pelée (such as during the plinian eruption in 1300 AD), since these phenomena were not yet known (Lacroix 1904). Examples as this one are numerous in volcanic areas. For instance, most of the villages of the northern and southeastern coast of Lombok Island (Indonesia) have been built on pumice PDC deposits emplaced during the 1257 AD ultraplinian eruption of the Samalas volcano (Lavigne et al. 2013).

# 3 How Do We Warn People in Time?

## 3.1 Difficulties in Providing Timely Warnings

PDCs are extremely mobile, generally travelling at tens to hundreds of km/h. Therefore alerts need to be provided at least several hours before the first PDC occurs. Unfortunately, local populations are not always warned by the authorities before an imminent eruption, for various reasons. In case of gravitational collapses of silicic lava domes, which trigger ‘Merapi-type’ pyroclastic flows, warning people is not possible until the occurrence of the collapse itself: reliable precursory signals have not yet been identified, as observed on Merapi on 22 November 1994 (Abdurachman et al. 2000), although in some cases, the characteristics of seismic activity can change leading up to a collapse e.g. at Soufriere Hills (Cole et al. 1998). In some cases, the absence of warning may be related to traditional scepticism in technological predictions, when local officials refuse to listen to the scientific forecasts and predictions at the very beginning of a volcanic crisis (IAVCEI Subcommittee for Crisis Protocols 1999). Additional external
drivers may prevent an alert by the local authorities (the mayor in many cases), e.g. local elections, as observed at the beginning of the 1902 eruption of Mount Pelée in Martinique (Lacroix 1904).

## 3.2 Modern Versus Traditional Warning Tools

The type of tools used to communicate warnings by local authorities in times of crisis is critical to ensuring an effective messaging. Modern tools like sirens are increasingly used as “official”

warning systems on active volcanoes. In developing countries, however, the areal distribution of sirens is not homogeneous, e.g. around Merapi in Indonesia (Fig. 8.2). Based on a survey carried out among 1969 people in shelters during the 2010 eruption of Merapi, only 16% of the people were warned by sirens before the PDCs totally destroyed the slopes of the volcano (Fig. 8.3, Mei et al. 2013), whereas most people received evacuation alerts directly from the head of village (54%), or from neighbors (11%).

The warning signal may be also transmitted by a mobile system installed on the fire department's vehicles (e.g. in France). In Japan, the

<figure><img src="image_46.png" /><figcaption>**Fig. 8.2** Siren distribution around the flanks of Merapi, Indonesia. Source Lavigne et al. (2015), based on Mei et al. (2013)</figcaption></figure>
<figure><img src="image_47.png" /><figcaption>**Fig. 8.3** The source of warnings during the 2010 volcanic crisis of Merapi, Indonesia (adapted from Mei and Lavigne 2013)</figcaption></figure>

J-Alert system, launched in 2007, aims to allow government officials to address the population directly via loudspeakers, e.g. in case of an eruption alert.

Other modern tools are widely used to warn people of imminent PDCs. Should a volcanic event happen, local people considered at risk may receive a warning message in the form of SMS Text Message and/or Email onto their cell phones, smart phones or other electronic devices like iPads, Laptops, Desktop computers, etc. Usually, this type of warning message would be distributed by Civil Defense Corps and includes all the hazards that could trigger an emergency situation, not only volcanic hazards, e.g. the app provided in Auckland (www.aucklandcivildefence.org.nz/Alerting/Get-the-Applications) or in Hawaii (http://www.hawaiicounty.gov/active-alerts). At Tongariro Volcano in New Zealand, for example, an alert is

provided by the key scientific institution to related agencies (e.g. Civil Defense and Emergency Management) and the media through online bulletins as well as direct communication through its emergency network. This bulletin is also accessible by the public via their network website and social media (Leonard et al. 2014). In Japan, real-time volcanic warning is available to the public on the website (JMA 2015). Beyond volcanic hazards, Japanese agencies send out SMS alerts to all registered mobile phones in the country (Pearson 2015).

Although modern tools are growing, traditional tools are still considered as efficient warning tools by local authorities, especially in remote areas. For example, the Indonesian *ken-tongan* (bamboo drum: Fig. 8.4a) is traditionally used for warning the public, notably in rural areas or during an emergency period during which electricity might be cut off, meaning that
<figure><img src="image_48.png" /></figure>

<table><caption>**Fig. 8.4** The use of bamboo drums (kentongan) at Merapi, Indonesia. **a** kentongan at the entrance of a house on the West slope of Merapi (Photo F. Lavigne, 2010). **b** Kentongan communication codes. *Source* Lavigne et al. (2015)</caption><thead><tr><th>(b)</th><th></th><th></th></tr></thead><tbody><tr><td>Aman</td><td>Normal, safe</td><td>000000 - 000000</td></tr><tr><td>Siap</td><td>Ready</td><td>00 - 00 - 00</td></tr><tr><td>Kejadian Khusus</td><td>Special event</td><td>000 - 000 - 000</td></tr><tr><td>Kejadian Besar</td><td>Major event</td><td>00000000 - 00000000</td></tr><tr><td>Bencana Alam</td><td>Disaster</td><td>00000000000000000000</td></tr><tr><td>Kematian</td><td>Death</td><td>000 - 000000 - 000 (repeated twice)</td></tr></tbody></table>

modern alert tools relying on electricity power might be dysfunctional. Based on a field survey at Merapi in 2002, over 70% of interviewed villagers thought that the *kentongan* was an efficient warning system (Lavigne et al. 2008). Every kentongan code has its own meaning (Fig. 8.4b). In case of volcanic disaster, the kentongan is beaten repeatedly and continuously with the same tone. It indicates that people should immediately evacuate to a pre-determined location, which is usually a village hall. However, many people among the young generation are not able to interpret the signals anymore. Therefore, the use of this tool is forbidden during Merapi's volcanic crisis in some municipalities or villages, e.g. in Sawangan and Selo on the north slope of the volcano (Mei et al. 2013).

## 3.3 Official Warning Versus Community-Based Warning

Local communities are still using natural warning signs of various types, as exemplified on the slopes of Merapi: increase in rock fall noise, increase in fumarolic activity from the summit's crater, the descent of monkeys or other wild animals from the hills, ground shaking relating to increased seismic activity, or lightning storms

caused by the emission of ash into the atmosphere. Local inhabitants can be reluctant to evacuate during a crisis if signals they are familiar with are lacking, and if they don't receive both traditional and official warning of a possible eruption (Donovan 2010). Furthermore, some culturally accepted warning signs can create a false sense of security, and it can be a struggle for some to believe those based on scientific monitoring alone. Such problems related to traditional cultural beliefs were reported not only in developing countries, but also in the USA at Mt. Kilauea in Hawaii (Gregg et al. 2004), Mount St. Helens (Greene et al. 1981), and in Italy at Mt. Etna and Mt. Vesuvius (Chester et al. 2008).

The credibility of a given warning and the validity of past warnings and evacuations, both influence the decision to evacuate. Social, economic and political forces may distort risk messages, leading to public reliance upon informal information networks (Haynes et al. 2008), e.g. social networks. Therefore, local organizations play a key role in crisis communication, as exemplified at Merapi by the actions of JalinMerapi (Jaringan Informasi Lingkar Merapi, in English Merapi Circle Information Network), a local organization supported by several NGOs working around the volcano. This
association was established in 2006 by three community-based radio stations. During the emergency response period in 2010, JalinMerapi used various electronic media to quickly and accurately convey important information and data to support the decision making process. JalinMerapi information was transmitted through a website, social networks such as Twitter and Facebook, SMS, radio communications, telephone and through information posters in the field. JalinMerapi was managed by a voluntary network that operated 24 h a day during the 2010 eruption (Mei et al. 2013). Thus, repetition of warnings through different sources of the evacuation command-line increased the chances that people heeded the warning.

Community-based volcano risk communication is also exemplified by the existence of the *los vigias* system in Tungurahua, Ecuador. *Los vigias* literally means watchmen, and comprises organised surveillance of the volcano made up of local community members from different villages situated on the flanks of the volcano. The vigias system has been integrated into the official risk communication of Tungurahua managed by the Volcano Observatory of Tungurahua (Stone et al. 2014).

## 4 Why Are People Reluctant to Evacuate?

Refusal to evacuate is one of the main issues in volcanic crisis management, as exemplified during the 2010 eruption of Merapi (Fig. 8.5). Evacuations have traditionally been a difficult task to carry out because of people's reluctance to leave their homes and land. Various reasons compound people's reluctance to evacuate in case of a volcanic crisis related to PDC hazard, as exemplified at Merapi (Mei and Lavigne 2013).

First, the principal reason for hesitancy is that some people do not believe that their lives are endangered by PDCs, or that PDCs are likely in that locality. Thus differences in perception of PDC management issues by local communities

and scientists or emergency planners may lead to a disruption of crisis management plans (Johnston and Ronan 2000; Ronan 2013). PDC hazard experience may create an inaccurate localized template for future eruptions, giving local people a false sense of safety (Douglas 1985; Donovan 2010). For instance, despite the efforts of officials, scientists and concerned members of the public of Montserat, about 80 people were in Zones A and B of the Exclusion Zone on 25 June 1997 (Loughlin et al. 2002). Many had become accustomed to the pyroclastic flows and had become overconfident in their own ability to judge the threat by observing repeated flows that had gradually increased runout but remained restricted to valleys. Many people had contingency plans and believed that there would be observable or audible warning signs from the volcano if the activity were to escalate significantly (Loughlin et al. 2002). The feeling of safety is enhanced with the presence of concrete structures like Sabo dams, and by increasing distance of the village from the crater. The feeling of safety felt by the local communities living further than 15 km from Merapi crater in 2010 was enhanced by the extent of the pyroclastic flow hazardous areas delineated by CVGHM, which did not take into account the possibility of a major explosive eruption (Mei et al. 2013). Therefore understanding how people perceive risk has become increasingly important for improving risk communication and reducing risk associated conflicts (Haynes et al. 2008).

Second, it is essential to consider the local and cultural factors in volcanic risk and crisis management (Lavigne et al. 2008). During the 2010 PDC of Merapi, the evacuation refusal of Mbah Marijan (the volcano's gatekeeper or *Juru Kunci*) and his followers led to the deaths of thirty-five people in Kinarhejo, a village located only 5 km from the summit, including the gatekeeper himself. Before this disaster, evacuation refusals along the southern flank of the volcano were mostly conditioned by trust in the gatekeeper and the feeling of being protected by his presence
<figure><img src="image_49.png" /><figcaption>**Fig. 8.5** Evacuation refusal during the 2010 eruption of Merapi volcano, Indonesia. Refusal means that at least one person in the village has been identified by the</figcaption></figure>

village's chief as being reluctant to evacuate after have received the warning. *Source* Lavigne et al. (2015)

(Mei and Lavigne 2012), even though in 2010 Marijan suggested to people not to follow his decision to stay in the village. Another well-known disaster related to large PDCs was partly due to evacuation refusals for cultural reasons: the 1963 eruption of Mount Agung occurred at the time of a very rare and important Balinese ceremony at Besaki Hindu temple, 7 km away from the crater. The PDCs were therefore interpreted as a punishment from the gods, leading to the death of more than 1000 people. Careful communication and awareness of potential culture clashes might aid

communication within and beyond the scientific community (Donovan and Oppenheimer 2014).

Third, people may be reluctant to evacuate even if they are aware of the danger. Economic pressure may explain people's behaviour during crisis, since they often refuse to evacuate in order to cultivate their crops, take care of their animals and protect their goods. Evacuation can have severe consequences on the economy of a village or a city. During the 2007 volcanic crisis of Kelut volcano in East Java, for instance, 77% of people living in Sugihwaras, a village close to the crater did not pay attention to the warning message
issued by the government, and almost a half of the interviewees disregarded the order to evacuate (De Belizal et al. 2012). They chose to stay at home, hiding themselves in their own houses, closing shutters and turning off lights. Almost two third of those interviewed thought it was dangerous to leave their houses and assets behind. They declared that they were afraid of potential looters, a common perception which has been deeply discussed in the literature (e.g. by Quarantelli 1984).

Some people refuse to evacuate until other family members, and also pets, are safe. A study conducted within the community living around Mayon Volcano, the Philippines, reveals how community members were not willing to stay at evacuation centers and preferred to stay with family members should an evacuation warning be issued by the authorities (Usamah and Haynes 2012). People may be reluctant to evacuate due to the sanitary situation in evacuation centres, either actual or due to rumors spread by the media. For instance, some people from Sugihwaras (Kelut) did not evacuate to the shelters during the 2008 volcanic crisis, because they heard that they were insalubrious (De Belizal et al. 2012). The media asserted that infectious diseases were spreading in many camps because of the bad quality of the food. The newspaper condemned the organizations in charge of the evacuation centres. Rumours of such diseases spread quickly and many people believed that problems occurred in every evacuation center. Such rumors have been largely covered by the literature (e.g. Drabek 1999) and may increase people's vulnerability.

# 5 Building Trust in Hazard and Risk Communication to Ensure Better Responses to Evacuations

Open and transparent communications between the stakeholders before and during a volcanic eruption is a key point in improving crisis management capabilities. In order to enhance these

capabilities, it is essential to consider the local and cultural factors in volcanic risk management. As pointed out by Haynes et al. (2008), specific differences between the public, authorities and scientists are often responsible for misunderstandings and misinterpretations of information, resulting in differing perceptions of acceptable risk. Deeper understanding of the at-risk communities is therefore a key issue in order to reduce vulnerability in PDC hazard regions. Information dissemination and education of the people at risk are also key factors in correcting the perception of PDC threats, and therefore in improving crisis communication. Modes of communication should be reviewed regularly in the context of social changes. The need for community participation and involvement in raising PDC hazard awareness is crucial. Risk communication is a dialogue between the communities and people giving the warnings. The take-up of scientific advice is much more efficient when communication of that advice is founded on personal trust rather than written on a report (Haynes et al. 2007a). As a result, communication of PDC hazard directly between scientists and the public is very important, e.g. on Montserrat (Haynes 2005; Donovan and Oppenheimer 2014).

# 6 Conclusion: Improving Crisis Management Capabilities for PDC's Risk Reduction

Crisis management capabilities may be improved through a set of good practices that are theoretically well-established, but that remain difficult to develop practically by the local stakeholders.

Among the good practices for raising PDC hazard knowledge and public awareness, information related to this specific hazard should be widely disseminated, through the members of hazard mitigation offices from regional to local levels, not only within the PDC hazard zones but also involve villages and cities located tens of kilometres away from the vent. PDC hazard information should be disseminated especially