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The way volcanoes erupt depends on many things. One of them includes the explosiveness of the viscosity and dissolved gases. The lower the dissolved gases the more the volcano is low-exploding (poofs of smoke).Vice versa too. The more silica content the more clogage there is in the volcano. If there is minimum silica it is runny like snot. If it has maximum silica then it will clog at the top and eventually build up so much, it will make a HUGE explosion with a bunch of smoke and explosion. An example of that is Mt. St. Helens. Composite volcanoes have high silica and viscosity and shield volcanoes or the opposite. There also are two other volcanoes cinder cone and lava dome, cinder cone has high dissolved gases and low silica. Lava dome is vice versa. No volcano can ever become “extinct” all volcanoes can explode at any time.
National Geographic Society. National Geographic. 1996. 2007. http://www.nationalgeographic.com/forcesofnature/interactive/index.html.
