In the United States this strategy is handled by that United States Geographical Survey. The survey has a color coded plan for handling such threats this includes: Green-No immediate threat, Yellow-Watch; Orange- Warning and Red- Eruption in progress. There are certain measures that are taken at each threat level.
Conclusion
Indeed there are active volcanoes around the world that make many people vulnerable. In most cases scientist can now predict when an eruption may occur with some accuracy. The best protection seems to be early warning. The research also indicates that people should heed such warning if they desire to live.
References
Dormant Volcano Erupts near Manila; Hundreds Feared Dead under Lava. New York Times September 29, 1965.
Lahars and Their Effects. United States Geological Survey. 4 April 2007 http://volcanoes.usgs.gov/Hazards/What/Lahars/lahars.html
Lava Flows. United States Geological Survey. 4 April 2007 http://volcanoes.usgs.gov/Hazards/What/Lava/lavaflow.html
Pyroclastic Flows and Their Effects. United States Geological Survey.
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