Q:

What causes a volcano?

A:

Volcanoes form when magma, a mixture of hot gas and molten rock, flows out of fissures in Earth's crust. The powerful eruption creates vents in the crust, and mountainous formations take shape above ground as molten rock spreads out in layers and gradually cools down. Each successive eruption occurs when more gas and magma accumulate in the vents, building pressure below the crust.

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Beneath Earth's outer surface, the fragmented crust layer is made up of tectonic plates that slowly shift position. Steaming magma helps the tectonic plates move and fills the space between the crust and the mantle, an inner layer of Earth. If plates move too far apart, pressurized magma can shoot up through the crust layer and form a volcano. When tectonic plates shift closer and forcefully bump into one another, their edges may be pushed so deep into Earth's interior that the solid rock heats up, turns into melted magma and rises back up through the crust as a volcano.

Every type of volcano has a distinct formation and eruption pattern. Shield volcanoes are shallow, low-lying formations with wide bases. They form when mild, centralized eruptions release lava that quickly spreads out in thin layers. Stratovolcanoes, also known as composite volcanoes, are highly explosive and contain multiple vents, leading to massive eruptions that cause molten rock to stack up in steep, sloped layers. Scoria volcanoes, or cinder cones, are usually symmetrical and have a large crater at the summit formed by repeated eruptions from a single vent.

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Related Questions

  • Q:

    How is a volcano formed?

    A:

    A volcano forms when magma rises through weakened areas of the crust from a magma reservoir many miles deep within the earth, pushing itself up through a vent. This vent acts as a release valve for pressure building up below, and when the new volcano erupts, thousands or millions of pounds of ash and molten rock slowly accumulate, forming a volcanic mountain.

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  • Q:

    Where do volcanoes form?

    A:

    Volcanoes can form anywhere the Earth's crust allows magma to reach the surface. Typically, this occurs around plate boundaries, either where plates are pulling apart or where one is forcing its way under another. Weak spots can also develop away from plate edges, creating magma vents called hot spots.

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  • Q:

    What causes volcanic eruptions?

    A:

    Volcanic eruptions occur when magma builds up beneath the Earth's crust and forces its way to the surface. Natural vents in the crust allow magma passage to the surface, and eruptions occur when the magma that forms is less dense than the material above it, causing it to flow upward. In some cases, this flow is slow and steady, but it can also be rapid and violent.

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  • Q:

    What causes a volcano to erupt?

    A:

    A volcano erupts when the pressure of a subterranean pool of magma becomes great enough to crack the earth's crust. Whether the eruption results in a violent explosion or a slow seepage depends on several different factors, according to How Stuff Works.

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