A volcano is a mountain that opens
downward to a reservoir of molten rock
below the
surface of the earth. Unlike most mountains,
which are pushed up from below, volcanoes
are built up by an accumulation of their
own eruptive products. When pressure from
gases within the molten rock becomes too
great, an eruption occurs. Eruptions can
be quiet or explosive. There may be lava
flows, flattened landscapes, poisonous
gases, and flying rock and ash.
Because of their intense heat, lava flows
are great fire hazards. Lava flows destroy
everything in their path, but most move
slowly enough that people can move out
of the way.
Dangers of a Volcano
Fresh volcanic ash, made of pulverized
rock, can be abrasive, acidic, gritty,
gassy, and odorous. While not immediately
dangerous to most adults, the acidic gas
and ash can cause lung damage to small
infants, to older adults, and to those
suffering from severe respiratory illnesses.
Volcanic ash also can damage machinery,
including engines and electrical equipment.
Ash accumulations mixed with water become
heavy and can collapse roofs. Volcanic
ash can affect people hundreds of miles
away from the cone of a volcano.
Sideways directed volcanic explosions,
known as "lateral blasts," can
shoot large pieces of rock at very high
speeds for several miles. These explosions
can kill by impact, burial, or heat. They
have been known to knock down entire forests.
Volcanic eruptions can be accompanied
by other natural hazards, including earthquakes,
mudflows and flash floods, rock falls and
landslides, acid rain, fire, and (under
special conditions) tsunamis.
Where can Volcanoes be found?
Active volcanoes in the U.S. are found
mainly in Hawaii, Alaska, and the Pacific
Northwest. Active volcanoes of the Cascade
Mountain Range in California, Oregon, and
Washington have created problems recently.
The danger area around a volcano covers
approximately a 20-mile radius. Some danger
may exist 100 miles or more from a volcano,
leaving Montana and Wyoming at risk.
