Q:

What is a volcanic eruption?

A:

Quick Answer

A volcanic eruption is the expulsion of magma and gas from the Earth's interior. Most current volcanic eruptions are the result of one of three eruption mechanisms.

Continue Reading

Full Answer

Magmatic eruptions occur as pressure releases from magma inside the Earth. The depressurization forces magma out through cracks in the Earth's crust, usually in the seafloor. Most of these eruptions involve basalt magma.

Phreatomagmatic eruptions, which are typically underwater, are the result of tectonic plates plunging downwards into Earth's mantle. This type of eruption is the opposite of a magmatic eruption in that it involves the addition of pressure to magma, rather than the release of pressure. Phreatomagmatic eruptions are responsible for the formation of most of earth's volcanoes.

Phreatic eruptions happen when steam superheats upon contact with magma. These eruptions often have little to do with the edges of tectonic plates, and instead, they occur at hotspots. These account for approximately 10 percent of the Earth's volcanoes.

Flood volcanism no longer occurs, but it is responsible for such landforms as the Columbia River Basalts and various underwater plateaus. In flood volcanism, basalt lava issues from fissures in the Earth's crust, sometimes covering over a thousand square miles. Tar and mud volcanoes also exist, neither of which involve magma.

Learn more about Volcanoes

Related Questions

  • 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.

    Full Answer >
    Filed Under:
  • Q:

    What happens before a volcanic eruption?

    A:

    According to the United States Geological Survey, before a volcanic eruption, magma must travel upwards through rock. The travelling magma produces these precursors to an eruption: an increase in earthquakes beneath a volcano, volcanic tremors, disturbance of ground features, increased release of steam from the volcano, increased temperatures and increase of gases. Additionally, different catalysts occur beneath the earth's surface prior to an eruption.

    Full Answer >
    Filed Under:
  • Q:

    What is a phreatic eruption?

    A:

    A phreatic eruption is a steam-based volcanic reaction caused by the heating of water by magma. The pressure caused by underground steam forces it to escape through volcanic eruption.

    Full Answer >
    Filed Under:
  • Q:

    What is a side vent in a volcano?

    A:

    Side vents, also known as secondary vents, in a volcano allow some of the magma and gases to escape but are not the main vent where the eruption takes place. One of the volcano's most recognized characteristic is the crater, but this hole actually forms after the eruption has taken place.

    Full Answer >
    Filed Under:

Explore