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How does a volcano form?

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Quick Answer

A volcano forms when a vent in the Earth's crust allows magma to well up from below. The magma fills a void underneath the surface, and when it builds up enough pressure, it bursts through to the surface. As the magma cools, it hardens into rock, and multiple eruptions may build up the mountainous form of a volcano.

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How does a volcano form?
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The Earth's crust seems solid, but it is actually made up of 17 large, rigid plates floating over a hot, malleable sea of molten rock. When these plates collide or pull apart, they can allow this molten material, called magma, to make its way upward into the crust. If magma finds a particularly weak spot, it may burst through to the surface, creating a volcano. These can come about as the result of a slow accretion of cooling lava, or they can be the result of spectacular, pressurized explosions.

In some cases, a single vent may create multiple volcanoes. The Hawaiian Islands are the result of a tectonic plate passing over a particular hot spot in the mantle, and that hot spot has created several volcanic mountains in the sea floor. The chain of islands and mountains created by this vent extends as far as Midway, and Kilauea is the current site of the active volcano.

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Related Questions

  • Q:

    How is a volcano made?

    A:

    A volcano is any place where magma from the Earth's interior breaks through its surface, as explained by How Stuff Works. Magma is molten rock that is partially liquid, partially solid and partially gaseous. Interaction between the plates that form the Earth's crust is one of the primary catalysts for creating magma.

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  • Q:

    What is a main vent in a volcano?

    A:

    The main vent of a volcano is the outlet chamber in the Earth's crust that allows hot magma to reach the surface. While secondary vents may form to alleviate the pressure caused by a magma chamber, the main vent is responsible for giving volcanoes their familiar cone shape.

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  • Q:

    What makes a volcano erupt?

    A:

    Volcanoes erupt due to pressure that the weight of the rocks puts on the magma and forces it to the surface out any available vent or exit provided to it. The magma is in a reservoir like area under the surface and the pressure from the rocks causes the less dense magma to move into any available crack or fissure that it can reach to try to release in some fashion. The magma can even melt its way to the surface if no exit is available for it at the time.

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  • Q:

    What causes a volcano to form?

    A:

    A volcano forms when magma pushes up through the Earth's crust from below, depositing lava on the surface. This lava cools, creating volcanic rock. Over time, repeated eruptions of lava build a cone-shaped mountainous structure, producing a volcano.

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