Larry
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In essence, a volcano is a crack or hole in the earth's crust. This opening serves as a vent for gases as well as lava and ash, which build up under the earth's surface and make their way to the earth above. The word volcano can be traced back to the island of Vulcano, located close by the coast of Sicily. This island, full of volcanic activity, was named after the god of fire, Vulcan.
Volcanoes are generally found at the convergence or divergence points of tectonic plates, which are either pushing against each other or pulling away from each other. The pressure caused by the earth's actions works continuously to form cracks in the earth's crust where magma can work its way to the top. As time passes, lava flows through these cracks and builds up to form the familiar cone shape associated with volcanoes.
Volcanoes erupt when gas pressure forces the molten rock upward and ultimately through the weaknesses in the earth's crust. These eruptions can present themselves as steam and lava flows down the sides of the volcano. The eruptions are often more violent, though, as the molten rock explodes through the surface and shoots violently into the air. Heavier fragments will usually fall to the ground in the nearby vicinity, but the finer particles in the form of ash clouds can be blown high into the atmosphere and carried by stratospheric winds several times around the world.
Many volcanoes can remain dormant for long periods of time, sometimes hundreds of years. People in the vicinity can be lulled into a false sense of security, believing these volcanoes will never erupt again. In truth, because of their placement on tectonic plates, even long dormant volcanoes can spring back to life in a short amount of time and cause death and destruction.
 Posted 5442 day ago
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