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7.6: Effusive Eruptions

  • Page ID
    5430
  • Isn't this an explosive eruption?

    This is a strombolian eruption. This type of eruption was named for Mt. Stromboli in Italy. Strombolian eruptions spew lava into the air, but these eruptions do not have a massive explosion. They create lava flows.

    Effusive Eruptions

    Mafic magma creates gentler, effusive eruptions. There is little or no gas. The lava is thin and fluid so that it flows over the ground like a river. Mafic magma pushes toward the surface through fissures. Eventually, the magma reaches the surface and erupts through a vent (Figure below). Effusive eruptions are common in Hawaii, where lavas are mafic.

    In effusive eruptions, lava flows readily, producing rivers of molten rock

    In effusive eruptions, lava flows readily, producing rivers of molten rock.

    Effusive Eruptions Damage

    Effusive eruptions rarely kill anyone because they move slowly. People can usually be evacuated before an effusive eruption. Still, effusive eruptions can be destructive. There is not much anyone can do to stop a lava flow from destroying a building or road (Figure below).

    Road covered by lava from an eruption at Kilauea in Hawaii

    A road is overrun by an eruption at Kilauea volcano in Hawaii.

    Summary

    • Mafic magma creates effusive eruptions. The pressure builds but the lava flows fairly quietly.
    • Effusive eruptions cause damage but rarely kill anyone.
    • Mafic magma cools into different types of flows like a'a, pāhoehoe, and pillow lava.

    Review

    1. Why do mafic lavas flow rather than explode?
    2. Compare and contrast lavas from explosive and effusive eruptions.
    3. Why do effusive eruptions sometimes cause a lot of damage?

    Explore More

    1. Why is Kilauea considered one of the most active volcanoes in the world?
    2. What does the height of Kilauea’s lava lakes mean regarding upcoming eruptions?
    3. Where does the lava go?
    4. What do shield volcano eruptions look like?
    5. Why is it difficult to predict a volcanic eruption from a volcano like Kilauea?
    6. What would scientists need to know to better be able to predict eruptions from Kilauea?