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Summary: Volcanoes can erupt only once, but other volcanoes, such as Kilauea, can erupt continuously for almost 30 years. Discover how those who study volcanoes define active volcanoes with help from the chair of a department of environmental studies in this free video on volcano eruptions.
"How often do volcanoes erupt? From continuous, I mean if you want to look at that, you could look at Kilauea in Hawaii, that's the longest continuously erupting volcano that we know of. It's been erupting for, it's going on close to 30 years now that it's been continuously erupting. To on the other end of the spectrum, never. It's a one shot deal, you get one eruption and it will never erupt again. Now if you take kind of generalities, what most volcanologists consider an active volcano is one that's generally erupted somewhere in the last three million years is considered still an active volcano. Now some people will put even a tighter restriction on that and say it's active if it's erupted in historic times, in other words maybe the past 5,000 years or something like that. So, again, the definitions vary a little bit but they go all over the spectrum. They'll go anywhere from continuous to every 25, 50 to hundreds to thousands to millions. Just depends."
eHow Article: How Often Do Volcanoes Erupt?
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