Q:

What causes volcanic eruptions?

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Quick Answer

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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What causes volcanic eruptions?
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Full Answer

Explosive eruptions occur when pressure builds up in magma chambers beneath volcanoes. This is often due to different types of magma mixing in the chambers. Lighter, less-dense magma naturally rises, but if a bubble of lighter magma builds beneath a more dense, viscous reservoir of magma, the pressure can build up inside the chamber. Eventually, it becomes enough to force the heavier magma through the volcano's vent, causing an explosive eruption.

An eruption can also occur due to a collapse of the cinder cone of the volcano. Over time, lava flowing out of a volcano builds up more and more rock around the vent, and in some cases, that rock may become unstable. If enough collapses into the vent to block it and prevent magma and gases from reaching the surface, the pressure can build up to the point of explosive eruption.

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Related Questions

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    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:

    How do volcanoes change the Earth's surface?

    A:

    Volcanic eruptions involve the incursion of liquid magma into a physical environment, and the effects include major transformations, ranging from the formation of new land to the destruction of the viability of an existing environment. Just one example of the creation of new land comes from the Hawaiian Islands, which appeared as magma cooled into land after eruptions.

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  • Q:

    How does a volcano form?

    A:

    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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  • Q:

    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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