What is a volcano?
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.
Source: FEMA
