volcanoes
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A volcano is a vent or fissure in the Earth's surface through which magma and gases are expelled. They are areas of earths surface which magma and volcanic gases are pass. Four differnt types of Volcanoes are the Shield Volcanoes, Cinder Cone Volcanoes, and Composite Volcanoes. Volcanos are a moutain that open a pool of lava below the suface of the earth. When the the pressure builds up that is when the eruptions occur. They are formed when magma from the earth's upper mantle works its way up to the surface. Once it comes up to the surface the it erupts, to form lava flows and ash deposites. When the volcano keeps on erupting the volcano will get bigger and bigger. There is four types of lava, which are Aa, Pahoehoe, Pillow lava, Blocky lava. Magma chambers and vents are inside of a volcano. A Magma chamber is a body of molten rock deep underground, it feeds the volcano. A vent is magma that rise from the magma chambers through the cracks in the earths crust to openings. Lava, and Pyroclastic material, are what is eruptedd from a volcano. There is four types of Pyroclastic Material which are, Volcanic bombs, Lapilli, Volcanic ash, Volcanic blocks.
Holt Science and Technology Earth Science pg. 250- 255
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http://www.kidcyber.com.au/topics/volcanoes.htm
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