found: USGS Volcano and hydrologic hazards, features, and terminology web site, Apr. 5, 2007(Supervolcanoes: The term supervolcano has no specifically defined scientific meaning. It was used by the producers of a British TV program in 2000 to refer to volcanoes that have generated Earth's largest volcano eruptions. As such, a supervolcano would be one that has produced an exceedingly large, castastrophic explosive eruption and a giant caldera. Because Yellowstone has produced three such very large caldera-forming explosive eruptions in the past 2.1 million years, the producers considered it to be a supervolcano. Because there is no well-defined minimum size for a "supervolcano", there is no exact number of such volcanoes. Examples of volcanoes that produced exceedingly voluminous pyroclastic eruptions and formed large calderas in the past 2 million years would include Yellowstone, Long Valley in eastern California, Toba in Indonesia, and Taupo in New Zealand. Other "supervolcanoes" would likely include the large caldera volcanoes of Japan, Indonesia, Alaska (e.g., Aniakchak, Emmons, Fisher), and other areas.)
