Mt Fuji

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  • Topic: Lava, Volcano, Volcanology
  • Pages : 4 (1386 words )
  • Download(s) : 367
  • Published : February 21, 2011
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A volcano is simply defined as an opening in the earth's surface crust through which molten lava, ash, and gases are ejected. Terrestrial volcanoes are believed to have formed when molten rock or magma welled up in the Earth’s interior pushed its way to the surface causing the volcanoes’ initial eruptions. Volcanoes all generally fit into one of six different categories: Shield volcanoes, Cinder volcanoes, Strato volcanoes, Submarine volcanoes, Sub glacial volcanoes, and the most powerful volcano of all, the Super volcano. Volcanoes can cause more harm than simply a lava flow. While lava is deadly to a person, volcanoes can also cause mudslides and rockslides, killing many. A volcano's explosion can send debris raining down on up to twenty miles around its self. There is actually over 100 active volcanoes all over Japan that is why Japan has over 500 miniature earthquakes (tremors) every year. Often, volcanoes can cover areas with thick ash, which, added to damage from lava flows, destroys houses, towns and crops.

Volcanoes are formed by of magma deep under the earth's surface. It occurs when two plates meet. When two plates move apart causing a gap, hot molten rock - called lava - rises up between them. If the amount of magma is large enough, it rises above the surface of the ocean and an island is created. If two plates collide and one plate is forced beneath the other plate, the friction makes the first melt and magma rises up. Only a few volcanoes are formed like this. When rock inside the Earth becomes hot enough it melts. This molten rock, or magma, is less dense than the surrounding solid rock. Just as an object that is less dense than water will float on water, the relatively low density of the magma causes it to rise to the surface of the Earth. If the magma contains water and dissolved gasses, when the magma reaches the surface the water and dissolved gasses will suddenly expand into steam and gas, causing a...
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