Volcanic Hazard in the 21st Century: an Asian-Pacific Perspective

Abstract

Asian-Pacific volcanoes have had devastating and often long-lasting impacts on nearby landscapes and communities. Relative to earthquakes and other natural hazards, such volcanic eruptions have long durations (typically weeks to months), impacts over large areas (sometimes in excess of 100,000 km2 [38,610 mi2]) and typically a number of different types of hazards will result from a single volcanic eruption. Perhaps more important for emergency managers and their scientific advisors, past large eruptions in our region have been preceded by recognizable precursors such as ground movement and earthquakes. These warning signs often give us the opportunity to act promptly and reduce risk to the population but they also introduce higher levels of responsibility and public expectation of the officials; few expect accurate predictions or forecasts for earthquakes or landslides but during volcanic crises there is intense pressure from the media and the population for the experts to “second-guess” the volcano.

Introduction

Several large natural disasters in 2004-2005 show us how society is growing more vulnerable to natural hazards and this increasing vulnerability is common to all hazards world-wide (Alexander, 1993; Tierney et al., 1999; Tobin, 1999). This increase is not due to changing hazard frequency, or intensity, but to increased vulnerability; that is, the cost of what we put at risk from eruptions. The impact of even small volcanic eruptions is escalating rapidly as a result of societal change, e.g. rising population densities and increasingly sophisticated infrastructures. The Asia-Pacific region has a history of violent volcanic eruptions (Table 1) that has been eclipsed only temporarily by other hazard events of the last several months: the December 2004 Indian Ocean earthquake and tsunamis, the August 2005 Hurricane Katrina in the U.S. Gulf Coast, and the October 2005 South Asian earthquake.

Mass casualties in contemporary hazard events are not limited to those countries without official warning systems to alert the public to impending danger. High death tolls can and do occur in countries with long-established warning systems (e.g., Hurricane Katrina). Ultimately, a warning system of any kind is only as good as the human response to it. Again, people’s perceptions and acceptance of risk and response to warnings is complex and often much different to official expectations. Here we contrast the natures of such hazard events and past large volcanic eruptions and discuss problems facing our communities in future eruptions.

Volcanic Crises

Data presented in Table 1 show a lack of correlation between the magnitude of recent volcanic events (as measured by the mass of material or amount of energy released) in the Asia-Pacific region and its impact. The scale of the impacts depends as much on the social fabric and demographics of neighboring communities, and their relationship to the environment, as on geological factors such as the intensity and style of the eruption. One twentieth-century example occurred at Nevado del Ruiz volcano (Colombia), a tall snow-capped Andean cone that has produced large lahars (volcanic mud flows) during historic times, with disastrous consequences. The 1985 eruption of Nevado del Ruiz was relatively small (0.01 km3) but generated lahars that destroyed more than 5,000 homes and killed more than 23,000 people, principally in the city of Armero. Lahars had buried the site of Armero twice previously, in 1595 and 1845. Warning systems and a hazard map had been established following the early unrest but were not acted on despite the fact that the lahar did not reach Armero until 2.5 hours after the eruption was detected. Researchers have postulated that “.... the officials were not willing to bear the economic or political costs of early evacuation or a false alarm. Science accurately foresaw the hazards but was insufficiently precise to render reliable warning of the crucial event at the last possible minute” (Voight, 1990).

Contrasts to Other Hazard Events

Why are volcanic eruptions special in the context of natural hazards? Volcanoes have devastating and often long-lasting impacts on nearby landscapes and communities (Blong, 1984). For example, researchers have suggested that the destruction from post-eruption lahars at Mount Pinatubo (Philippines) cost more than the climactic eruption. Relative to earthquakes and other natural hazards, volcanic eruptions have long durations (typically weeks to months), impacts over large areas (up to in excess of 100,000 km2) and typically will result in multiple types of hazards from a single volcanic eruption. Perhaps more important for emergency managers and their scientific advisors, large eruptions are preceded by recognizable precursors such as ground deformation and earthquakes. Globally, our scientific community is getting increasingly better at supplying accurate information to the public but we will always have difficulty in estimating the ultimate size of the eruption (before AND during a crisis), the precise form the eruption will take, and the lag time between onset of activity and a dangerous climax.

Event Duration

Figure 1 is a compilation of data from the Smithsonian Institution for the durations of 3,301 well-known eruptions (Simkin and Siebert, 2000). It shows clearly the difficulties that emergency managers and their expert advisors face in terms of forecasting the duration of eruptions. Notice that 9% of eruptions last less than 1 day and 5% more than 5 years. There is therefore considerable uncertainty involved in any form of forecast of future behavior even once an eruption has begun. The typical eruption duration of 1-6 months will contribute greatly to enhanced levels of long-term stress and fatigue for personnel in affected agencies. By comparison, most other meteorological and geological hazards have short and finite lengths and the response moves, within hours or days, into the recovery phase.

Multiple Hazards: Multiple Problems

Unlike many natural hazards, a single eruption typically poses many different threats to neighboring communities (Blong, 1984), e.g., simultaneous production of ash fall and hot lava at Mount Etna in 2001 and 2002-2003 (Calveri and Pinkerton, 2004; Andronico et al., 2005). In Hawaii, near-constant eruption of lava flows is accompanied by emissions of volcanic gases and aerosols (U.S. Geological Survey, 1997). Each hazard necessitates different strategies for effectively reducing risk — different facilities or lifelines will be at risk, and different forms of hazard maps and exclusion zones will be needed.

Figure 1. Duration of volcanic eruptions. The histogram depicts the durations of 3,301 well-documented eruptions, after Simkin and Siebert (2000).

Figure 2. The time interval between the onset and climax (i.e. the dangerous peak of activity) for 252 moderate to powerful explosive eruptions, after Simkin and Siebert (2000).

Precursors and Forecasting

Warning signs often give us the opportunity to act promptly and reduce risk to the population but they also introduce a higher level of responsibility and public expectation of the officials — no one expects accurate predictions or forecasts for earthquakes or landslides but during volcanic crises there is intense pressure from the media and the population for the experts to “second-guess” the volcano. Once an explosive eruption begins, there is frequently less than 24 hours (Figure 2) before it reaches a dangerous climax. This short escalation time span exacerbates pressures on emergency managers and their expert advisors.

Volcano Tourism

The growth of adventure tourism on active volcanoes is a very recent phenomenon, which is uncommon for most other hazard events. USA, Italy, New Zealand, and several central American nations all have significant tourism ventures built around the concept of safe exposure of visitors to the spectacle of an erupting volcano. These operations have the unintentional effect of increasing drastically the size of the at-risk population, often in settings where the precise intensity of eruptive activity is impossible to forecast on short time scales. Balancing the dependence of local communities on tourist revenues with issues of public safety has been a feature of several 21st century eruptions.

Issues for Crisis Management

Volcanic crises are complex social events where the weak point is often not an organization but the links between organizations. A successful intervention during a volcanic crisis requires the emergency management, and physical and social science communities to function together efficiently. “Cultural” and operational contrasts between these groups remain a barrier today to successful emergency management, compounded by the uncertainties of accurate forecasting of future events.

Managing unexpected or escalating volcanic crises is a difficult challenge, placing much higher demands on the personal resources and competence of the emergency manager (Paton et al., 2001). Because they are spectacular and new to most observers, even small eruptions may take on an undeserved “notoriety”, attracting intense media attention and inducing fear and anxiety in the community. Even with the best command system, functioning communications and a team who know their roles, the emergency manager will have to make decisions ‘in the heat of the moment’, often on the basis of incomplete information and ambiguous intelligence about the unfolding eruption. The rarity of volcanic crises means that emergency managers may have had relatively little recent exposure to operational situations, and this can enhance the difficulty of tasks for them and their team. Uncertainty throughout each stage of an eruption can generate elevated levels of stress and anxiety over long periods. Recent social science research now understands a great deal about the nature of stress and mechanisms to prepare and deal with it (Paton et al., 2001). Social science is also invaluable in understanding how the public behave — not just during volcanic crises but also during public education and awareness programs.

Volcanic eruptions are spectacular events which are highly “newsworthy” and it is vital that the media message accompanying eruption images conveys a
true impression of the associated level of risk. It is important that emergency managers and their
scientific advisors are proactive in forming a media response plan. It is critical to meet the needs and deadlines of the media and in particular to appear “live” on radio and television to reassure the public. Without this, eruptions are commonly accompanied by a phenomenon called social amplification of risk (Kasperson et al. 1988) where unjustified fears in the population generate panic and unnecessary reaction. If this occurs, valuable resources are diverted from the eruption response to reduce public anxiety. Scientists need to develop closer relationships with the news media before a crisis happens so they can provide more useful information during a crisis — because the media deliver the message. Simultaneously, the media need to understand the limitations and constraints of real-time scientific data, so that they can communicate the information as accurately as possible.

Pre-eruption education campaigns at active volcanoes are becoming increasingly sophisticated in recognizing the complex social ways in which society works (Ballantyne et al., 2000). Emergency management is switching away from simple awareness programs to emphasizing the processes that lead to better prepared, more resourceful communities like Kagoshima in Japan. Irrespective of the level of perceived risk, people are unlikely to act if they perceive hazard effects as insurmountable (low outcome expectancy) or perceive themselves as not having the competence to act (low self-efficacy). Even when intentions are formed, they may not be acted on. Whether intentions are converted to actions depends upon people’s interpretation of their past experiences, their appraisal of whether they have the required time, resources, skills, and social networks, their sense of community, and whether they accept personal responsibility for safety.

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Endnotes
1 Department of Geology & Geophysics, University of Hawaii, Honolulu, HI 96822
2 Department of Physics, Astronomy and Geology, East Tennessee State University, Johnson City, TN 37614