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
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.
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
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.
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.
What to do Before a Volcanic
- Add a pair of goggles and disposable breathing mask for
each member of the family to your disaster supply kit.
- Stay away from active volcano sites.
- If you live near a known volcano, active or dormant, be
ready to evacuate at a moment's notice.
What to Do During a Volcanic
If a Volcano Erupts Where You Live:
- Follow the evacuation order issued by authorities and
evacuate immediately from the volcano area to avoid flying
debris, hot gases, lateral blast, and lava flow.
- Be aware of mudflows. The danger from a mudflow
increases near stream channels and with prolonged heavy
rains. Mudflows can move faster than you can walk or run.
Look upstream before crossing a bridge, and do not cross
the bridge if a mudflow is approaching.
- Avoid river valleys and low-lying areas.
- Remember to help your neighbors who may require special
assistance - infants, elderly people, and people with
Protection from Falling Ash
- Listen to a battery-powered radio or television for the
latest emergency information.
- If you have a respiratory ailment, avoid contact with
any amount of ash.
- Wear long-sleeved shirts and long pants.
- Use goggles and wear eyeglasses instead of contact
- Use a dust mask or hold a damp cloth over your face to
help with breathing.
- Stay away from areas downwind from the volcano to avoid
- Stay indoors until the ash has settled unless there is
a danger of the roof collapsing.
- Close doors, windows, and all ventilation in the house
(chimney vents, furnaces, air conditioners, fans, and other
- Clear heavy ash from flat or low-pitched roofs and rain
- Avoid running car or truck engines. Driving can stir up
volcanic ash that can clog engines, damage moving parts,
and stall vehicles.
- Avoid driving in heavy ash fall unless absolutely
required. If you have to drive, keep speed down to 35 MPH
Much of the info on this page was taken from FEMA's web site
which can be referenced at: