Volcanoes

General Info About Volcanoes

    Volcanoes are basically vents is the surface of the Earth.  They erupt when molten rocks in the Earths mantle are pushed to the surface.  The rocks break through the Earths crust.  The melted rocks are released in the form of lava.  The melted rocks are called magma while they are still in the Earth and they are called lava when they break through the Earth's surface.

    Volcanoes usually happen at plate boundaries.  There are three types of plate boundaries: Divergent( the plates are moving apart), Convergent(plates are coming together), and Transform Faults (the plates are sliding past each other).
Volcanoes usually occur on divergent or convergent boundaries.
    Some volcanoes also occur at places called hot spots. Hot spots are areas in the Earth's mantle that get so hot the magma rises and forms a volcano.  As plates move over the hot spots chains of islands are formed.  An example of a hot spot is Hawaii.

    There are three different types of volcanoes.  The first is a Shield volcano.  Shield volcanoes don't have explosive eruptions, the lava is continuously flowing from the top.  This constant flow doesn't allow the volcano to get very steep.  The second type of volcano is the Cinder Cone.  Cinder Cone volcanoes have major explosive eruptions irregular intervals. These explosions cause the volcano to be very steep.  Some Cinder Cone volcanoes do not erupt for thousands of years and others on a more regular basis.  The third type of volcano is the Composite volcano.  Composite volcanoes have eruptions every once and awhile and the lava bubbles over also.  These Composite volcanoes are not as steep as Cinder Cone volcanoes, but they are not as flat as Shield.

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