PREDICTING
VOLCANIC ERUPTIONS
Scientists
have no trouble figuring out where volcanoes are, but predicting a volcanic
eruption is not as easy. There are many different methods and tools
scientists use to try to predict when a volcano will erupt.
HISTORY
The
first thing scientists do is determine a volcano's eruption history.
A volcano is classified as active, dormant or extinct
based upon when it has last erupted.
- Active
volcanoes are in the process of erupting or show signs of eruption
in the very near future.
- Dormant
volcanoes are "sleeping." This means they are not erupting
at this time, but they have erupted in recorded history.
- An
extinct volcano has not erupted in recorded history and probably will
never erupt again.
SEISMOMETER
Next,
scientists consider seismic (earthquake) activity as it is registered
on a seismometer. A volcano will usually register some small earthquakes
as the magma pushes its way up through cracks and vents in rocks as
it makes its way to the surface of the volcano. As a volcano gets closer
to erupting, the presure builds up in the earth under the volcano and
the earthquake activity becomes more and more frequent.
TILTMETER
Scientists
also have an instrument that they attach to the side of volcanoes. It
is called a tiltmeter. A tiltmeter will detect small changes in the
slope of a volcano because as a volcano is about to erupt, the earth
may bulge or swell up a bit.
GAS
EMISSIONS
Another
thing scientists look for is the amount and types of gasses that are
emitted from a volcano. When a volcano is close to erupting, the gasses
become more pronounced. There is a slight problem with depending upon
only gas emissions to predict eruptions, however. Sometimes lava will
leak up through the top of a volcano and harden quickly. This will trap
gasses inside of a volcano. Therefore, no gasses may be seen just before
an eruption. This type of data collection may be very dangerous for
scientists because they have to go to the top of the volcano and the
gasses are very poisonous.
SATELLITES
Scientists
also use satellites to try to predict eruptions. Satellites can record
infrared radiation where more heat or less heat shows up as different
colors on a screen. If a volcano is seeming to become hotter, then an
eruption may be coming soon.
ACOUSTIC
FLOW MONITORING
A more
recent monitoring techique used by scientists is the Acoustic Flow Monitor
(AFM). With this type of instrument, scientists use a seismometer to
record sound waves within a volcano. It has been determined that as
pressure builds up within the earth, sound waves can be recorded-and
that the waves coming from inside of a volcano just before an eruption
look like regularly formed sound waves more than eratic and jagged earthquake
waves.
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