Q:

What causes a volcano to erupt?

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Quick Answer

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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What causes a volcano to erupt?
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Full Answer

Molten rock, called magma, forms underground when Earth's tectonic plates collide or move apart, or when activity within the mantle, a very hot layer beneath the earth's crust, causes the crust to melt. Magma contains dissolved gases that remain dissolved as long as the pressure of the gas is not greater than the confining pressure of the solid rock around it. If the vapor pressure becomes great enough, the gas forms small bubbles within the magma. These bubbles are less dense than the surrounding magma, so they push upward to escape it, and an eruption occurs. The composition of the magma is an important factor in determining the force of this eruption. If it contains larger amounts of gas, it erupts more violently. Another factor is the viscosity of the magma. Magma with a high viscosity resists flowing, and the gas bubbles must forcefully push out more material to escape. On the other hand, magma with a low gas content and low viscosity is likely to result in a slow, non-explosive eruption.

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Related Questions

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    Why do so many of Earth's volcanoes occur along plate boundaries?

    A:

    Plate boundaries are the weakest points in the Earth's crust, which leads to cracks that allow magma to seep through and develop volcanoes, according to NEWTON. These areas are called "subduction zones." Subduction zones form the Ring of Fire, a volcanic region in the Pacific Ocean, explains Live Science.

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  • Q:

    Why did Mount Pinatubo erupt?

    A:

    In March 1991 and April 1991, magma rising 20 miles beneath the surface of the Pinatubo volcano caused many earthquakes and small explosions, which destroyed parts of the volcano. Then on June 12, 1991, magma filled with gas reached the surface, and the volcano erupted.

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  • Q:

    What is the difference between a volcano and a mountain?

    A:

    The chief difference between a volcano and a mountain is that a volcano forms around a vent that allows magma to reach the surface of the Earth, while a mountain can be formed by a variety of different geological processes. Most mountains form as the result of plate tectonics, although some were formed by magma welling up from the mantle without breaking through the surface.

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  • Q:

    What type of magma does Popocatepetl have?

    A:

    The volcano Popocatépetl produces magma that is primarily andesite mixed with some dacite as of the current eruption cycle including 2015. This active stratovolcano, the second tallest peak in Mexico, has erupted primarily andesitic magma for most of its history.

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