VOLCANOES
    A volcano is an opening in the earth's surface through which lava, hot gases, and scorching hot rock fragments erupt.  Cracks, in the Earth's crust, allow the hot magma from deep within the Earth's mantle to rise towards the surface.  When the pressure gets so great from the magma, it breaks through the surface to form a volcano.  After it breaks the Earth's surface and starts to flow out it is called lava.  Most volcanos are mountains, particularly cone shaped ones, because when the volcano erupts the ash, lava and other material thrown during the eruptions builds up around the opening.
    Eruptions of volcanic mountains are awesome sights.  In some eruptions, huge fiery clouds rise over the mountain, and glowing rivers of lava flow down its sides.  In other eruptions, red hot ash and cinders shoot out of the mountain top, and large chunks of hard rock are blasted into the air.  A few eruptions are so violent they blow the mountain apart.  Some eruptions occur on volcanic islands.  Eruptions have caused some of the world's worst disasters in history, wiping out towns and thousands of people.
    When volcanoes erupt on land they are big news.  However, we never hear about most volcanic eruptions because they erupt on the ocean floor.  Lava flows out onto the ocean floor.  When the hot lava reaches the cold ocean waters it hardens into rock and adds new crust to the ocean floor.
    There are three main kinds of volcanos and they are Shield , Cinder-Cone, and Deposit Volcanos.  The highest volcano above sea level is Aconcagua in Argentina and it stands at 22,831 feet.  The lowest volcano above sealevel is Surtsey in the North Atlantic Ocean and it stands at 568 feet.
    Scientists have been studying where volcanoes occur and they have concluded that volcanoes occur along the plate boundaries.  Scientists have learned that the earth is broken into twenty plates and these plates join together to form the Earth's crust.  These plates move in different directions from 2 to 15 centimeters per year.  As the plates move and collide the sinking crust enters the mantle and melts into magma.

    On this map below the red and black lines show where volcanoes occur - these are where the fault lines are.

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Volcano Experiment