Why Dormant Volcanoes?
Country: United States
Date: November 2008
One of my students asked, "What causes volcanoes NOT to erupt?"
I would use a bottle of carbonated drink as a metaphor. If the container is
sealed tight, then no eruption (no over-flowing fizz) happens. If the bottle
is kept calm and opened gently, there may be some hissing as the pressure
escapes, but no overflow. If the bottle is shaken and given a lot of energy
and then opened, there is an eruption.
Pretty good question. Your student is obviously doing some good thinking and
the answer, "It is missing what makes it erupt", may not satisfy them at first,
but that is the answer.
Volcanoes erupt when melted rock, called magma, hot water and gasses come near
the surface of the ground from below. The rock eventually makes it up to the
surface or very near it and the volcano erupts.
A volcano stops erupting when it loses, or uses up the source of heat that melts
the rock. If the source of heat returns at a later date, the volcano will erupt
Think of a pot of boiling water. If you are boiling water (the volcano is
erupting) and turn the stove off (the volcano loses or uses up its source of
heat), the water stops boiling (the eruption stops).
If you turn the heat back on later, the water will boil again (the volcano
erupts after lying dormant).
Where the heat for volcanoes comes from and how volcanoes lose or use up this
heat is fairly complex unless the student understands “Continental Drift”
Oklahoma State University Institute of Technology
Good question. For a volcano to erupt, there must be some sort of heat source
(usually pressure and/or heating from the interior of the Earth). If there is
no heat source, there really is no way for the volcano to erupt. So, what causes
a volcano not to erupt? Lack of energy/heat.
If she or he is wondering if we can stop a volcano from erupting, right now the
answer is no, scientists do not know of any way to stop it.
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Update: June 2012