A volcano is
an opening in the earth's surface through which lava,
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
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
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
On this map below the red and black lines show where volcanoes occur -
these are where the fault lines are.
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