Why do volcanoes erupt?
Zach &
Kyle (4th grade students)
Hi Zach and Kyle,
A volcano is a place where lava, ash and/or gases come out of the interior
of the Earth onto the surface. We call molten rock magma while it is still
underground and lava once it has reached the surface. If you can identify
a volcano that means that lava and ash have erupted there and built some
sort of pile of material. It may be steep or gradual, big or small,
depending on lots of things like how runny the lava is, how much ash
relative to lava was erupted, how many eruptions have taken place from the
same vent, and so on.
So, your question asks why does a volcano erupt. The easiest answer is
that it erupts when the pressure of the magma inside becomes so great that
the volcano splits and the magma gets out. The magma pressure can get
high if the supply to the volcano from the Earth's mantle is high. The
magma pressure can also get high if magma is just sitting around in the
magma chamber within the volcano. This is because as the magma in the
chamber starts to cool off, it releases gases. These gases can increase
the pressure until the volcano fractures and you have an eruption.
I hope this helps.
Sincerely,
Scott Rowland, University of Hawaii
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