Volcanoes form when hot rocks from inside
the earth move up towards the surface.
When the rocks are deep inside the earth, they are
squished by pressure and therefore they are solid.
When the rocks move up, there is less pressure on
them and so they expand. Sometimes the change in
pressure is so much that they can melt and become
To make sense off this think of a marshmallow
in your hand. If you squeeze the marshmallow in
your hand, it will get smaller. Your hand is
putting pressure on the marshmallow. Now, if you
open your hand and relieve the pressure, the
marshmallow will go back to its normal size, or
expand. >When rocks melt, gas escapes. Gases take up
more space than liquids or solids, so they
increase the pressure. The gas that escapes will
build up until it increases the pressure on the
magma to the point where the magma will find a
crack or tunnel and erupt.
Unfortunately for geologists (because we like
to study volcanic eruptions), but luckily for all
of us that live here, there have not been any
recent volcanic eruptions near Goleta or Santa
Barbara. The closest recent eruptions have been in
Mexico and in Washington, Mount St. Helens.
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