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PART VIII Eruption Response and Mitigation  Scores of volcanoes will continue to erupt (about 55 to 70 being active each year), and will thus continue to pose a significant risk as the world's population grows and we rely increasingly on technology for the basic needs of civilization. However, some of the same technologies that improve life, such as the Global Positioning System (GPS), have also led to improvements in forecasting of eruptions. Better data, plus improvements in the use of data, have led to increasingly effective responses to eruptions and mitigation of their hazards.One of the main tools for monitoring is seismology. Nearly every eruption is preceded by an increase in earthquake activity, and eruptions are accompanied by a continuous vibration of the ground known as volcanic tremor. The opening chapter of this section, Seismic Monitoring, discusses the use of seismology in eruption forecasting and monitoring in general. The chapter includes case studies of eruptions at Mount St. Helens, Kilauea, Ito-Oki, Pavlof, and Pinatubo. Deformation of the ground, such as bulging, doming, or the formation of cracks, is also frequently found prior to eruptions. Further, if new magma is injected beneath a volcano, gravity changes may occur because new mass is being added. Finally, when rock is heated near its Curie temperature, its magnetization decreases. The following chapter, Ground Deformation, Gravity, and Magnetics, discusses modern techniques of measuring deformation, gravity, and magnetic signals and their use in monitoring volcanoes and eruption forecasting. Case histories include Sakurajima, Krafla, Colima, Mount St. Helens, Campi Flegrei, Poas, Etna, White Island, and Aso volcanoes. In addition to earthquakes and deformation, volcanoes also typically show signs of increased heat or changes in degassing prior to eruptions. These may be measured from the Earth's surface or from satellites if the signal is strong enough. During eruptions, plumes of ash and gases rise and may then travel great distances downwind. The next chapter, Gas, Plume, and Thermal Monitoring, examines the monitoring of gases, heat, and plumes, and illustrates these with examples from Mount St. Helens, Pinatubo, Showa-Shinzan, Usu, Vulcano, Long Valley caldera, Galeras, Masaya, Etna, Popocatepetl, El Chichon, Spurr, Erebus, Lascar, and others. Each type of data may be handled and interpreted individually, but experience has shown that much more can be learned when various data sets are combined. Indeed, closely monitored eruptions with many data sets provide much of the basis for progress in volcanology. The chapter Synthesis of Volcano Monitoring describes how various types of data contribute to an evolving understanding of the activity of volcanoes. The sequence of geological, geochemical, and geophysical events is different for different types of eruptions. These ideas are illustrated using detailed case studies from Mount Etna and from Soufriere Hills (Montserrat). Once scientists agree about the meaning of the data (and even if they disagree), a series of communications need to occur between scientists and those responsible for emergency response. The actions that need to be taken, appropriate for the current or expected hazards, need to be identified and assigned to the right people. The content and distribution of warning messages, maps, videos, alert levels, etc., are the focuses of the chapter Volcano Warnings. Concepts are illustrated using examples from two volcanoes that have erupted, Mount St. Helens and Pinatubo, and one that has not, Long Valley caldera. Although most eruptions are small, any eruption can pose a risk if people or structures are close to the volcano. Large eruptions, in contrast, affect nearby populations with certainty and have many effects at great distances. In each case, the perception of the events, and the response of society, will dictate whether or not an eruption is benign or whether a disaster will occur. The next chapter, Volcanic Crises Management, discusses elements of volcanic crises management, drawing on experiences at El Chichon, La Soufriere (Guadeloupe), Popocatepetl, Nevado del Ruiz, and others. Past eruptions leave deposits that can be studied to learn about the type and distribution of specific volcanic hazards. Further, contemporary eruptions at similar volcanoes may be studied to learn about the general effects of hazards. Once these are identified, coherent strategies may be developed to help mitigate risk. Some of these are direct, such as building dams to protect areas from mudflows. Some are longer term and less direct, such as land use zoning. Others are indirect and strategic, such as setting appropriate rates for insurance. These and other related topics are discussed in the chapter Volcanic Hazards and Risk Management. When an eruption occurs or is about to occur, the need for information suddenly becomes acute. Much of the needed information can be prepared ahead of time; indeed, the in-between periods last much longer than the eruptive periods. Effective strategies for education and intervention are the subjects of the final chapter of this section, Risk Education and Intervention. Although few studies have been done on the subject, the authors of this article assess the effects of a brief school-based intervention program that they performed at three schools following the 1995 eruptions of Mount Ruapehu, New Zealand. Although volcanoes will continue to erupt, knowledge of their behavior and effects, and adequate monitoring programs, can greatly reduce the risks from future eruptions. People can coexist with volcanoes provided they do so intelligently. Stephen R. McNutt | |