|Why do volcanoes erupt? Why is it that whenever
there is a earthquake a volcano would erupt? How
can you prevent a volcanic eruption?
|Question Date: 1999-02-25|
As far as preventing a volcanic eruption, I have
to say that there really is NO WAY a volcanic
eruption can be prevented based on current
technology. It is similiar to trying to influence
the track of a storm...there is so much energy
involved that any attempt on the human scale to
prevent it or make a storm move from one place to
another is FUTILE. The best we can do is to try
and FORECAST an eruption. This can sometimes be
done if a network of stations on the volcano is
set up. Then by monitoring volcanic-related
earthquakes as well as small changes in the TILT
of the land and the emission of gases, it is
possible to estimate in a rough way the chances of
an eruption. Unfortunately, this is not an exact
science. It is expensive to maintain and deploy a
set of instruments and so this is not often done
except for volcanos in populated areas.
VOLCANIC ERUPTIONS: Why do they
Well this is a complex question.
Basically, magma rises from depths in the Earth
because magma is of lower density than the
surrounding rock. Just like a balloon filled with
Helium, the low density molten rock RISES in
cracks and fissures and eventually gets extruded.
Sometimes, because the magma cools, it does not
make it all the way up to the surface and instead
freezes at depth to form a plutonic (as opposed to
volcanic) rock. GRANITE is a good example of a
common PLUTONIC ROCK.
Finally, there are
many earthquakes that DO NOT INVOLVE migration or
eruption of magma. There is a type of EARTHQUAKE
called " VOLCANIC TREMOR" that IS invariably
associated with volcanic eruptions. This is
realated to the flow of molten stuff in the
conduit. It is similiar to the VIBRATION that gets
set up in a pipe of flowing water. When you turn
on the shower or let the water run in the kitchen
sink, the flow of water in the pipe actually
causes some vibration to get set up. Sometimes you
can hear this. When magma flows in cracks, the
same sort of thing can happen... and we can pick
that signal up on a seismometer. Hence we can look
for these signals when we are trying to judge
whether an eruption may occur.
I have never heard of any way to stop a volcano,
and I don't even think geologists are studying how
this can be done.The forces that cause volcanic
eruptions are so big and so deep that people can't
do much except to predict when they will erupt and
get out of the way!
because of gases that are in the magma underneath
the volcanoes. Typical volcanic gases are water
vapor (H2O) and carbon dioxide (CO2), but there is
also some nitrogen gas and sulfer dioxide and
others. You can think of these gases like the
carbon dioxide in a bottle of Coke. You don't see
the carbon dioxide because it is dissolved in the
Coke, but when you pour the Coke into a glass the
carbon dioxide comes out of the liquid and forms
bubbles. In the magma under a volcano the same
thing happens, but the reason it happens is that
the magma is cooling and turning from molten rock
to solid rock made of crystals. When part of the
magma becomes rock several miles underground there
is less magma left over to hold the gas.
Eventually the gas becomes saturated in the magma
and comes out of solution, forming bubbles. These
bubbles exert a lot of pressure on the walls and
roof of the cavern of magma, causing a new crack
to form or an old vent to open up. When this
happens the gas bubbles expand and force the magma
out. You can see evidence of these gases in a lot
of lava rock that looks like Swiss Cheese or a
sponge from the holes in it. These holes were
expanding gas bubbles that caused the magma to
That was a long and maybe complicated
answer, so send more questions if you have
Maybe you should consider why it is not possible
to stop a volcano. I know that this sounds like a
cop-out answer but I think that you have enough
information that you can answer your own question.
How hot is molten lava? What could you make that
could stop a lava flow? Would using a steel plate
be enough? How about concrete? How much energy
is in a volcanic explosion? I've heard that some
explosions are as much as an atomic bomb. Look
for information like this.
You should try
looking for information on plate tectonics in
order to get a good answer. A quick answer would
not be really meaningful. Use "plate tectonics" as
a search word on the internet. You'll find out
that the surface of the planet is made up of
"plates" of rock that float on magma. A good
analogy is when you heat refried beans (or
oatmeal) in a pot and the top of the beans cools
and forms a crust over the warm beans underneath.
The crust will crack into sections. These
sections are like the "plates" floating on magma.
These plates move over the magma very very slowly
(a couple of centimeters a year in some places).
Where ever they rub against each other you get
earthquakes. In some places they push up against
each other until one plate slips under the other.
The one that goes under the other ends up going
back down into the magma and melts. Some of the
stuff that melts is lighter than the magma and
rises (like oil poured into water, it all pushes
up to the top and floats). But in this case the
other plate blocks the rising melted stuff. This
stuff will eventually melt its
way through the
plate and burst through as lava.
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