What Causes Volcanic Eruptions?

Answer

A volcano erupts when magma escapes from inside the earth. Magma sometimes rises under enormous pressure, so it not only finds cracks in the earth's crust, it can also create them. When magma reaches the earth's surface it is called lava.
Q&A Related to "What Causes Volcanic Eruptions"
magma and heat preasurizing.
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Volcanic eruptions are caused by divergent tectonic plates pulling
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The crust of the earth or mantle floats on a liquid oceans of magma. As plates or parts of the mantle collide magma is forced to the surface of the earth through a process known as
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Igneous rocks form from volcanic eruptions, such as basalt and pumice.
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3 Additional Answers
Ask.com Answer for: what causes volcanic eruptions
Several factors trigger volcanic eruptions, including the buoyancy of magma, a build-up of pressure from the gases in the magma and an injection of new magma into a full magma chamber.
When a part of the earth's upper mantle or lower crust melts, magma forms. A volcano is essentially an opening or a vent through which this magma and the dissolved gases it contains are discharged.
A volcano is an opening or vent through which magma and dissolved gases are discharged from the earth's mantle. Volcanoes happen when rock melts underneath the earth's surface. Their mass remains the same while their volume increases, this makes the rocks to be lighter hence raising them towards the surface through buoyancy.
When a portion of the earth's lower crust or upper mantle melts, magma is formed. The magma and dissolved gases need to be discharged. The vent where this happens is actually the volcano. You can find more information here: http://www.scientificamerican.com/article.cfm?id=what-causes-a-volcano-to
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