Volcanoes
Of the more than 1,500 potentially active volcanoes in the world, eight to ten are erupting at any given moment. On the bottom of the seabed circling the Pacific basin lies a series of volcanic arcs and oceanic trenches coinciding with the edges of one of Earth's main tectonic plates. This zone is called the Ring of Fire, because of its frequent earthquakes and volcanic eruptions. About 80 percent of these volcanoes are located in countries in Pacific Asia. The most volcanically active country in Asia is Indonesia, which has seventy-six historically active volcanoes, four-fifths of which erupted in the last century. Ten have erupted since 1990.
Volcanoes form when a break in Earth's crust allows magma (molten rock) and hot gas to reach the surface under pressure, resulting in dangerous eruptions. The main threats in the immediate area of these eruptions are high-speed, superheated toxic gases and debris (pyroclastic flows), blast effects, lava flows, volcanic earthquakes, landslides, and lahars (mudflows). Ash clouds or deposits and tsunamis (tidal waves) can be hazardous over a greater distance. Volcanoes can cause immense destruction to crops, forests, roads, and entire towns, resulting in many evacuees who must be sheltered, fed, and resettled.
While Japan's cone-shaped Mount Fuji presents an image of a volcano's majestic beauty, the volcanoes of the Philippines have earned the reputation of being the most deadly and costly in the world. On average over 13 percent of volcanic eruptions cause fatalities and 22 percent cause damage. The 1991 eruptions of Mount Pinatubo, for example, caused an estimated US$260 million in damage. The series of eruptions lasted for months, producing the largest cloud of climate-modifying gases since mighty Krakatau erupted in Indonesia in 1883. Scientists estimated that Pinatubo's eruption added more aerosols (light gases and particles) than all human activity since the industrial revolution. The cooling effect of these particles on the atmosphere lasted for two years and temporarily more than offset any global-warming effect.
Many Asian countries have increased their volcano research and monitoring, to provide greater warning time of likely eruptions and to broaden natural-hazard management programs. Although these efforts help to mitigate the impacts of volcanic eruptions on humans and property, volcanic eruptions will persist as a significant natural hazard throughout countries located in Asia's Ring of Fire.
James Hafner
Further Reading
Kovach, Robert L. (1995) Earth's Fury: An Introduction to Natural Hazards and Disasters.Upper Saddle River, NJ: Prentice-Hall.
Merrits, Dorothy, Andrew De Wet, and Kirsten Menking. (1998) Environmental Geology: An Earth System Science Approach. New York: W. H. Freeman.
Simkin, Tom, and Lee Siebert. (1994) Volcanoes of the World. 2d ed. Washington, DC: Smithsonian Institution.
Smith, Keith. (1996) Environmental Hazards: Assessing Risk and Reducing Disaster. 2d ed. London and New York: Routledge.
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