Q:

How often do volcanoes erupt?

A:

Some volcanoes erupt often and some are inactive for long periods of time. The amount of time between volcanic eruptions depends on the volcano itself, according to the Department of Geosciences at Oregon State University.

Three things that can trigger a volcanic eruption are magma buoyancy, pressure from gases in the magma and magma refilling the magma chamber. When rock melts, it produces magma that is lighter than the rock around it. This causes buoyancy that makes the magma rise to the surface and the volcano to erupt. Magma contains water, sulfur dioxide and carbon dioxide that cause bubbles in the magma, making the magma partially molten. This causes the volcano to erupt explosively. When new magma enters a chamber already filled to capacity with old magma, it pushes the magma to the top and the volcano erupts.

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Related Questions

  • Q:

    How do volcanoes erupt?

    A:

    Volcanic eruptions can either be effusive or explosive. An effusive volcanic eruption occurs when the lava pours out onto the ground from the volcano's vent. When the molten rock or magma is thin and runny, gases can easily escape and the lava flows freely and travels far. An explosive volcanic eruption is caused by thick and sticky magma, which prevents gases from escaping and causes them to explode violently.

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  • Q:

    What causes volcanoes to erupt?

    A:

    A volcanic eruption is caused by the injection of magma into a full magma chamber, the buoyancy of magma and the pressure exerted by the gases in the magma. The volcano simply acts as an opening through which magma and dissolved gases are discharged.

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  • Q:

    How do cinder-cone volcanoes erupt?

    A:

    Cinder-cone volcanoes, properly called scoria volcanoes, erupt when expanding gas bubbles drive lava to the volcano's surface. Because of this pressure, the lava fountains are usually very high and vertical. By the time the erupted material lands, it is already cool.

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    How do shield volcanoes erupt?

    A:

    Shield volcanoes usually erupt with splattering liquid lava that fountains out and has little explosive potential. This forms some of the largest volcanoes on Earth with very gentle slopes, since the liquid water cannot build steeper slopes. This type of lava cools to form basalt rock.

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