Top of Part 4
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Material at a certain
temperature radiates
infrared-ray
which has an energy
proportional to
the fourth power of
its absolute temperature
(an temperature which
fixed its origin
at 273 degrees centigrade
below zero).
By making use of this,
we can get a distribution map
of ground surface
temperatures when
we observe a spectrum
of infrared-ray radiated
from some area.
An airplane is
commonly employed
for the observation
of a large area in a
short time.
The ground temperature
distribution map obtained
in this way is called an
aerial infrared-ray image.
A surface temperature of
an active volcano is
closely related with the
volcanic activity.
Therefore, an aerial
infrared-ray image is
useful for immediate
grasp of the present state
of volcanic activity.
Discovery of a new
abnormally high
temperature area
may lead to the prediction
of a volcanic eruption
of which surface activity
is not yet exposed.
In cooperation
with the Self-Defence Forces,
SEVO has kept taking aerial
infrared-ray images
of the summit area
from a helicopter
during the period
of eruption of Unzen volcano.
