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7 - Eruptions and lahars of Mount Pinatubo, 1991-2000
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- By C.G. Newhall, Earth Observatory of Singapore, Singapore, R.U. Solidum, Philippine Institute of Volcanology and Seismology, Philippines
- Edited by Susan C. Loughlin, Steve Sparks, University of Bristol, Sarah K. Brown, University of Bristol, Susanna F. Jenkins, University of Bristol, Charlotte Vye-Brown
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- Book:
- Global Volcanic Hazards and Risk
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- 05 August 2015
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- 24 July 2015, pp 249-254
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Summary
Mount Pinatubo (Philippines) – asleep for ∼ 500 years – began to stir in mid-March 1991, and produced a giant eruption on 15 June 1991, second largest of the twentieth century. Only that of remote Katmai-Novarupta, Alaska in 1912 was larger. About 20,000 indigenous Aeta lived on the volcano, and ∼1,000,000 lowland Filipinos lived around it. Two large American military bases, Clark Air Base and Subic Bay Naval Station, added about 40,000 Americans to those at risk. With centuries' of volcanic gas (supply) accumulated in tens of cubic kilometres of molten rock (magma), and with so many innocent people nearby, a disaster was waiting to happen.
Thick deposits from pumice-rich pyroclastic flows formed the lower slopes of the volcano and told a history of infrequent but very large eruptions - larger than any eruption in the history of modern volcano monitoring. Scientists warned that a giant eruption was possible, perhaps even likely, but none had ever been monitored, much less successfully forecast. For two months after the volcano began to stir, small earthquakes and other signs fluctuated without clear, systematic trends. The volcano was teasing the scientists, and the public was profoundly sceptical.
Against the odds, a team of scientists from the Philippine Institute of Volcanology and Seismology (PHIVOLCS), assisted by the US Geological Survey, correctly forecast a giant eruption. Evacuations that had been recommended earlier were now enforced and expanded. Over the course of a few days, small precursory eruptions escalated to a spectacular climax on 15 June that swept the whole volcano, killing virtually everything in its path. Avalanches of searingly hot ash and pumice (pyroclastic flows) filled valleys and swept over ridge crests. Tens of centimetres of ash, with weight nearly doubled by rain from simultaneous Typhoon Yunya, caused many roofs to collapse. Loss of life was relatively modest considering the population at risk and the enormous size of the events (∼400 died during the eruption, and ∼500 Aeta children died in evacuation camps from measles). Warnings, coupled with strong visible clues from pre-climactic eruptions, had saved nearly all of the Aeta population, plus an unknown number of lowlanders. Some damage was unavoidable, but much was also averted, especially damage to military assets and commercial jets.
1 - An introduction to global volcanic hazard and risk
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- By Susan C. Loughlin, British Geological Survey, UK, Charlotte Vye-Brown, British Geological Survey, UK, R.S.J. Sparks, University of Bristol, UK, Sarah K. Brown, University of Bristol, UK, J. Barclay, University of East Anglia, UK, E. Calder, University of Edinburgh, UK, E. Cottrell, Smithsonian Institution, USA, G. Jolly, GNS Science, New Zealand, J-C. Komorowski, Institut de Physique du Globe de Paris, France, C. Mandeville, US Geological Survey, USA, C.G. Newhall, Earth Observatory of Singapore, Singapore, J.L. Palma, University of Concepcion, Chile, S. Potter, GNS Science, New Zealand, G. Valentine, University at Buffalo, USA
- Edited by Susan C. Loughlin, Steve Sparks, University of Bristol, Sarah K. Brown, University of Bristol, Susanna F. Jenkins, University of Bristol, Charlotte Vye-Brown
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- Book:
- Global Volcanic Hazards and Risk
- Published online:
- 05 August 2015
- Print publication:
- 24 July 2015, pp 1-80
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2 - Global volcanic hazard and risk
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- By Sarah K. Brown, University of Bristol, UK, Susan C. Loughlin, British Geological Survey, UK, R.S.J. Sparks, University of Bristol, UK, Charlotte Vye-Brown, British Geological Survey, UK, J. Barclay, University of East Anglia, UK, E. Calder, University of Edinburgh, UK, E. Cottrell, Smithsonian Institution, USA, G. Jolly, GNS Science, New Zealand, J-C. Komorowski, Institut de Physique du Globe de Paris, France, C. Mandeville, US Geological Survey, USA, C.G. Newhall, Earth Observatory of Singapore, Singapore, J.L. Palma, University of Concepcion, Chile, S. Potter, GNS Science, New Zealand, G. Valentine, University at Buffalo, USA
- Edited by Susan C. Loughlin, Steve Sparks, University of Bristol, Sarah K. Brown, University of Bristol, Susanna F. Jenkins, University of Bristol, Charlotte Vye-Brown
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- Book:
- Global Volcanic Hazards and Risk
- Published online:
- 05 August 2015
- Print publication:
- 24 July 2015, pp 81-172
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Summary
Introduction
An estimated 800 million people live within 100 km of an active volcano in 86 countries and additional overseas territories worldwide [see Chapter 4 and Appendix B]1. Volcanoes are compelling evidence that the Earth is a dynamic planet characterised by endless change and renewal. Humans have always found volcanic activity fascinating and have often chosen to live close to volcanoes, which commonly provide favourable environments for life. Volcanoes bring many benefits to society: eruptions fertilise soils; elevated topography provides good sites for infrastructure (e.g. telecommunications on elevated ground); water resources are commonly plentiful; volcano tourism can be lucrative; and volcanoes can acquire spiritual, aesthetic or religious significance. Some volcanoes are also associated with geothermal resources, making them a target for exploration and a potential energy resource.
Much of the time volcanoes are not a threat because they erupt very infrequently or because communities have become resilient to frequently erupting volcanoes. However, there is an everpresent danger of a long-dormant volcano re-awakening or of volcanoes producing anomalously large or unexpected eruptions. Volcanic eruptions can cause loss of life and livelihoods in exposed communities, damage or disrupt critical infrastructure and add stress to already fragile environments. Their impacts can be both short-term, e.g. physical damage, and long-term, e.g. sustained or permanent displacement of populations. The risk from volcanic eruptions and their attendant hazards is often underestimated beyond areas within the immediate proximity of a volcano. For example, volcanic ash hazards can have effects hundreds of kilometres away from the vent and have an adverse impact on human and animal health, infrastructure, transport, agriculture and horticulture, the environment and economies. The products of volcanism and their impacts can extend beyond country borders, to be regional and even global in scale.
Although known historical loss of life from volcanic eruptions (since 1600 AD about 280,000 fatalities are recorded, Auker et al. (2013)) is modest compared to other major natural hazards, volcanic eruptions can be catastrophic for exposed communities. In 1985 the town of Armero in Colombia was buried by lahars (volcanic mudflows) with more than 21,000 fatalities due to relatively small explosive eruptions at the summit of Nevado del Ruiz volcano that partially melted a glacier (Voight, 1990).
22 - Development of a new global Volcanic Hazard Index (VHI)
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- By M.R. Auker, University of Bristol, UK, R.S.J. Sparks, University of Bristol, UK, S.F. Jenkins, University of Bristol, UK, W. Aspinall, University of Bristol, UK, Sarah K. Brown, University of Bristol, UK, N.I. Deligne, GNS Science, New Zealand, G. Jolly, GNS Science, New Zealand, Susan C. Loughlin, British Geological Survey, UK, W. Marzocchi, Istituto Nazionale di Geofisica e Vulcanologia, Italy, C.G. Newhall, Earth Observatory of Singapore, Singapore, J.L. Palma, University of Concepcion, Chile
- Edited by Susan C. Loughlin, Steve Sparks, University of Bristol, Sarah K. Brown, University of Bristol, Susanna F. Jenkins, University of Bristol, Charlotte Vye-Brown
-
- Book:
- Global Volcanic Hazards and Risk
- Published online:
- 05 August 2015
- Print publication:
- 24 July 2015, pp 349-358
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Summary
Background
Globally, more than 800 million people live in areas that have the potential to be affected by volcanic hazards, and this number is growing [Chapter 4]. The need for informed judgements regarding the global extent of potential volcanic hazards and the relative threats is therefore more pressing than ever. There is also an imperative to identify areas of relatively high hazard where studies and risk reduction measures may be best focussed. Various authors have tackled this task at a range of spatial scales, using a variety of techniques. At some well-studied volcanoes, the geological record has been used in combination with numerical modelling to create probabilistic hazard maps of volcanic flows and tephra fall [Chapter 6 and 20]. Such sources of information can be hugely beneficial in land use planning during times of quiescence and in emergency planning during times of unrest. Unfortunately, creating high-resolution probabilistic hazard maps for all volcanoes is not yet feasible. There is therefore a need for a methodology for volcanic hazard assessment that can be applied universally and consistently, which is less data-and computing-intensive. The aim of such an approach is to identify, on some objective overall basis, those volcanoes that pose the greatest danger, in order that more indepth investigations and disaster risk reduction efforts can then be focused on them.
Previous methods
An index-based approach to volcanic hazard assessment involves assigning scores to a series of indicators, which are then combined to give an overall hazard score. Indicators typically include measures of the frequency of eruptions, the relative occurrence of different kinds of eruptions and their related hazards, the footprints of these hazards, and eruption size. Indices are well suited to the problem of volcanic hazard assessment, as they allow the decomposition of the complex system into a suite of volcanic system controls and simple quantitative variables and factors that jointly characterise threat potential.
Ewert (2007) presented an index-based methodology for assessing volcanic threat (the combination of hazard and exposure) in the USA, to permit prioritisation of research, monitoring and mitigation.