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Outline The Recent Improvements In Volcano Hazard Management That Can Help With Decisions About Whether An Area Should Be Evacuated Or Not During A Volcanic Crisis.

Date : 19/06/2016

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Adam

Uploaded by : Adam
Uploaded on : 19/06/2016
Subject : Geography

One of the most effective ways to mitigate the effects of a volcanic eruption is the evacuation of people from threatened areas. The explosion of population growth in the vicinity of active volcanoes has made this ever more apparent and demanded great improvements in the tools and equipment used in volcano hazard management. Recently, the scientific community has started to produce critical analysis in the physical human interface in a way that past disaster management bodies struggled to do, making an effort to consider and factor in the economic, social and political costs of hazard management procedures. This, combined with recent improvements in the accuracy of volcano assessment strategies and techniques, has helped with decisions of evacuation. In this essay I will examine several of these improvements and outline how they have contributed to decisions of evacuation.


Volcano monitoring data provides the only scientifically valid basis for making short-term eruption forecasts and consequently decisions of evacuation (Tilling 2008). Historically, data shows that eruptions have typically been preceded by unrest, be it in the form of chemical or physical changes in and around the volcano. Such data is obtained from both ground and air based methods and includes seismic levels, changes to global positioning system (GPS) measurements, gravity, magneticity and/or gas emissions. Two techniques in particular have seen recent improvements, and are applied most widely and frequently. These are seismic and geodetic methods. Indeed 'A survey of volcanologists carried out in 2008–&2009 suggests that participants regard broadband seismometers as the most useful tool in monitoring volcanoes, but with continuous GPS measurements a very close second' (Donovan et al 2012).


Whilst the majority of volcanic seismic activity does not lead to an eruption, seismic activity which exceeds background levels typically signals the likelihood of an eruption. Seismic activity occurs as magma rises to the surface or expands to create the growth of a lava dome. As magma rises, it forcibly creates a pathway, consequently unsettling stress distributions and pore fluid pressures and thus resulting in fracturing and numerous small-magnitude earthquakes. Seismic signals can thus be used to detect the ascension of magma within the earth's crust and predict potential eruptions. For example, prior to the eruption of Pinatubo 1991, the foci of seismic events revealed a significant migration of seismic activity and long-period (LP) seismicity and seismic-energy release also increased (Harlow et al., 1996& White, 1996 cited Tilling 2008). Even when an eruption is taking place, seismic events provide information on the style of activity and can be used to detect changes in the physical system. Furthermore, due to the installation of networks of three component and broad band seismometers, recent improvements in volcano seismology have allowed the recognition of different types of earthquakes which can be linked to particular volcanic phenomena, in addition to the recognition of long-period signals related to flow of volcanic gases and geothermal fluids (Sparks 2003). The use of seismic activity measurements then can be used to determine the rise of magma and thus help with decisions of whether an area should be evacuated. High levels of seismic activity suggests a rapid rise in magma and thus the chance of an eruption, providing signals which would aid decisions to evacuate the surrounding area.


In regards to GPS measurements, the movement of magma along subterranean channels, or its storage in magma chambers, leads to the deformation of surrounding crustal rocks and consequently, the Earth's surface. Most ground deformation techniques thus measure the resulting changes on or near the Earth's surface. In addition to the use of GPS, standard techniques to measure ground deformation include electronic distance measurements (EDM) using reflected laser or infrared light, measurement of ground tilt, precise levelling and borehole sensors including strainmeters and tiltmeters (Sparks 2003). Recent improvements in GPS have provided volcanologists with significant advancements in the quality and quantity of data available to them. Typically, ground deformation, particularly that of ground inflation, is observed before the onset of an eruption. For example, in the case of Mount St Helens 1980, magma intrusion led to the outward movement of the north flank of the volcano by 1-2 m/day (Lipman et al 1981 cited Sparks 2003). Furthermore, volcanic eruptions on Montserrat were anticipated based on observations of ground deformation and lava dome formation, which started in October 1996 and led to a precautionary evacuation (Sparks 2003). However, it is important to highlight the difficulty in predicting the structural stability of volcanoes, the timing of an eruption and thus evacuation decisions, as the collapse of the lava dome did not take place until December 1997. Furthermore, as a result of tectonics, isostatic adjustment and changes in geothermal systems, substantial ground deformation can occur without an eruption. Additionally, some eruptions occur without any deformation detected. As a result, for predictions of eruptions and decisions of evacuation, ground deformation and GPS techniques cannot solely be relied on. However, in regions with short historical records or limited conventional monitoring, global studies of volcano deformation using satellite data will increasingly play a part in assessing eruption potential (Aspinall 2014).


However, we must distinguish between hazard assessment/prediction and hazard management. Many, if not all, of the improvements in volcano monitoring so far discussed relate to volcanological assessment and prediction. In regards to volcano hazard management and the decision to evacuate, many recent improvements have come from the social sciences, or at least from a greater collaboration between social and physical sciences. Whilst the refinement and improvement in accuracy of various techniques such as seismicity, GPS measurements and tilt meters have certainly helped with eruption forecasting, it has been social factors, such as the increase and sharing of inter-disciplinary knowledge and the cooperation of social and physical sciences that has helped improve volcano hazard management and the decisions of whether to evacuate or not.


"The usual strategy adopted during a volcanic crisis is to fallback on the subjective opinions of a pool of experts" (Marzocchi and Woo 2007). As a result experts have a lot of power, providing the knowledge and advice on which significant decisions are made. As a result, a critique of volcano hazard management is that decisions are made based on volcanologist's advice. Such decisions may lead to a costly evacuation of residents for extended periods of time, and if the eruption fails to materialise, many people object. For example, the risk of an eruption of Soufriè&re in Guadeloupe, 1976, led to the government evacuating 70,000 people over a 9 month period. Yet ultimately the eruption did not result in any damage leading to a bitter reaction by evacuated citizens. As a result, there has been a great increase and improvement in scientific discussion and the integration of datasets in an attempt to improve the accuracy of evacuation decisions. This cross-disciplinary communication and expertise has been a struggle in the past and yet the importance of dialogue between scientific fields of enquiry, 'the idea of "interactional expertise' [and] the ability to communicate meaningfully within a discipline…&', (Collins (2004) cited Donovan et al 2012), particularly when an evacuation is possible, has taken on a more significant role in volcano hazard management. Generally, the fields of enquiry participating in the prediction of volcanic eruptions represent a highly interdisciplinary arena, involving geophysicists, seismologists, geochemists, petrologists and others. By combining the array of information each brings to the metaphorical table, assessing the state of a volcano, the probability of an eruption and the necessity of whether an area should be evacuated becomes much more accurate. For example, the integration of data for Mount Pinatubo 1991, led to a successful forecast and timely evacuation of tens of thousands of people (Sparks 2003). Clearly then, the importance of discussion is key and it is apparent how recent improvements in the collaboration and consideration of different scientific fields has helped improve the accuracy of volcano hazard management. 'The fact that scientific consensus [is] viewed as less important than communication between scientists also emphasises the importance of discussion between a range of views, over a polarised approach' (Donovan et al 2012). However, interdisciplinarity is difficult for the scientists themselves to develop (Collins and Evans 2007 cited Donovan et al 2011) and it is thus important to recognise that more isn't necessarily better as a greater number of opinions and level of data, which may or may not conflict, makes agreement much more difficult to reach.


Additionally, the use of cost benefit analysis is another recent social science technique employed to help with decisions of evacuation. In a field characterised by high uncertainty, the decision to evacuate involves weighing the advantages of evacuation against the disadvantages of non-evacuation, namely loss of life. Whilst this appears straightforward, the balance of judgement is assessed subjectively, and as a result individuals may place a higher value on certain factors and losses than would others. Thus, the use of cost benefit analysis attempts to subjectively forecast the tangible and intangible costs of evacuation and non-evacuation, consequently serving as a valuable tool in volcano hazard management. Typically, evacuation costs are measured in terms of economic loss whilst non evacuation costs are measured in years of life lost. As a result 'The significant socio-economic expense of evacuation is the premium deemed worth paying so that, in the event of a volcanic eruption, the much higher cost of mass casualties is avoided' (Marzocchi and Woo 2007). Furthermore, central to the discussion around the use of cost benefit analysis is the valuation of economic loss against that of human life. In developed countries, the cost of a volcanic eruption is more likely to be expressed in economic terms whilst, in contrast, an eruption in a developing country often sees costs represented in terms of life years lost. Thus, when using cost benefit analysis, particularly in developed countries, it is important that human life is not under valued and the choice to minimise the probability of "false alarms', and thus economic loss, is not the optimal one when many lives are at risk. For example, in the case of Vesuvius, 'acknowledging the stated priority of Italian Civil Protection authorities to safeguard human life, the implementation of a cost benefit criterion for evacuation decision-making would allow this principle to be reconciled in a measured rational way with the known public intolerance of false evacuation alarms' (Marzocchi and Woo 2007). A lot of uncertainty surrounds volcano hazard management and the predominant view surrounding volcanic eruptions is "Better to be safe than sorry'. Yet this argument is becoming ever more harder to justify when the economic cost of evacuation is so high. With the expansion of urbanism and rapid population growth, this cost is only set to rise further. Consequently, the development and implementation of a cost-benefit framework enables probabilistic forecasting tools to be used more effectively to improve evacuation strategies and consequently improve and reduce any objections, protest and upset caused by evacuation.


Despite great pressure being placed on volcanologists to predict eruptions, precise forecasts of eruptions remain elusive. Notwithstanding adequate volcano monitoring, there remains a great need to improve forecasts and refine models and their inputs and outputs. Yet, it is evident that volcanological methods can be effectively used for mitigation and hazard management purposes. Furthermore, the success of incorporating various spatial-temporal factors into a framework which manages to include scientific uncertainty represents a significant improvement on past methods of volcano hazard management. However, no matter how accurate, complete and correctly interpreted, volcanological data does not guarantee successful prediction and outcomes of future volcanic crises. Ultimately, volcanological data is predominantly interpreted by managerial action and it is the reaction of politicians to scientific recommendation that will determine the success of volcano hazard management and evacuation procedures. As a result officials and the general public must be prepared to accept the consequences and costs of occasional, unavoidable "false evacuations'. Indeed '. . . False alarms themselves can provide, through objective assessment of the scientific and public response to a volcanic crisis that ended without eruption, valuable lessons useful…&for the next crisis, which could culminate in an eruption' (Banks et al 1989 cited Tilling 2008). People show a surprising desire to remain in places which are dangerous and where their livelihoods are threatened and thus the demand for accurate predictions are needed to ensure an effective and persuasive evacuation. Demonstrating cost effectiveness for volcano hazard management beyond the volcanological community certainly represents a challenge. Scientists may feel that they have to place higher probability on predictions because they believe the public will misunderstand them if they don't. However this may lead to more occurrences of "false evacuations' which may be extremely damaging, not only to the local economy, society and political base, but to the legitimacy and credibility of scientific enquiry. Consequently, 'governments and relevant authorities [may] be reluctant to fund volcano hazard management techniques if unconvinced of their worth' (Donovan et al 2012). Examples worldwide indicate that the best volcano hazard management approach is one that employs a combination of techniques rather than a reliance on any single one and it is unquestionable that, without adequate monitoring data, there is not even the opportunity to avert volcanic catastrophe. Thus it is essential that continued effort is made to improve volcano hazard management techniques and reduce uncertainties so that decisions to evacuate will become ever more accurate and appropriate.


References


    Donovan, A., Oppenheimer, C., Bravo, M. (2012). Reply to comment from W.P. Aspinall on 'Social studies of volcanology: knowledge generation and expert advice on active volcanoes' by Amy Donovan, Clive Oppenheimer and Michael Bravo [Bull Volcanol (2012) 74:677-689]. Bulletin of Volcanology 74 (6):1571-1574. Donovan, A., Oppenheimer, C., Bravo, M. (2012). Science at the policy interface: volcano-monitoring technologies and volcanic hazard management. Bulletin of Volcanology 74 (5):1005-1022. Marzocchi, W., and G. Woo (2007), Probabilistic eruption forecasting and the call for an evacuation, Geophys. Res. Lett., 34, L22310. Sparks, J, S, R. (2003). Forecasting volcanic eruptions. Earth and Planetary Science Letters 210 (2003) 1-15 Tilling, I, R. (2008). The critical role of volcano monitoring in risk reduction. Advances in Geoscience, 14, 3–&11.

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