Disaster Preparedness Guide From FEMA

What to do Before,
During and After...

Natural and Man-Made Disasters Home

  • Adobe PDF Icon Volcanoes (PDF Version - Free Download - 301KB)

Ash and smoke erupt from a volcanoA volcano is a vent through which molten rock escapes to the earth’s surface. When pressure from gases within the molten rock becomes too great, an eruption occurs.

Some eruptions are relatively quiet, producing lava flows that creep across the land at 2 to 10 miles per hour. Explosive eruptions can shoot columns of gases and rock fragments tens of miles into the atmosphere, spreading ash hundreds of miles downwind. Lateral blasts can flattentrees for miles. Hot, sometimes poisonous, gases may flow down the sides of the of the volcano.

Lava flows are streams of molten rock that either pour from a vent quietly through lava tubes or by lava fountains. Because of their intense heat, lava flows are also 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, glassy and odorous. While not immediately dangerous to most adults, the combination of acidic gas and ash could cause lung damage to small infants, very old people or those suffering from severe respiratory illnesses. Volcanic ash can also damage machinery, including engines and electrical equipment. Ash accumulations mixed with water become heavy and can collapse roofs.

Volcanic eruptions can be accompanied by other natural hazards: earthquakes, mud- flows 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.

The May 18, 1980 eruption of Mount St. Helens in Washington took the lives of 58 people and caused property damage in excess of $1.2 billion.

What to do before an eruption

  1. Make evacuation plans. If you live in a known volcanic hazard area, plan a route out and have a backup route in mind.

  2. Develop a household disaster plan. In case household members are separated from one another during a volcanic eruption (a real possibility during the day when adults are at work and children are at school), have a plan for getting back together. Ask an out-oftown relative or friend to serve as the “household contact,” because after a disaster, it’s often easier to call long distance. Make sure everyone knows the name, address, and phone number of the contact person.

  3. Assemble a disaster supplies kit (see “Emergency Planning and Disaster Supplies” chapter).

  4. Get a pair of goggles and a throw-away breathing mask for each member of the household in case of ashfall.

  5. Do not visit an active volcano site unless officials designate a safe viewing area.

What to do during an eruption

  1. If close to the volcano evacuate immediately away from the volcano to avoid flying debris, hot gases, lateral blast, and lava flow.

  2. Avoid areas downwind from the volcano to avoid volcanic ash.

  3. Be aware of mudflows. The danger from a mudflow increases as you approach a stream channel and decreases as you move away from a stream channel toward higher ground. This danger increases with prolonged heavy rains. Mudflows can move faster than you can walk or run. Look upstream before crossing a bridge, and do not cross if the mudflow is approaching. Avoid river valleys and low-lying areas.

  4. Stay indoors until the ash has settled unless there is danger of the roof collapsing.

  5. During an ash fall, close doors, windows, and all ventilation in the house (chimney vents, furnaces, air conditioners, fans and other vents).

  6. Do not drive in heavy ashfall unless absolutely required. If you do drive in dense ashfall, keep speed down to 35 mph or slower.

  7. Remove heavy ash from flat or lowpitched roofs and rain gutters.

  8. Volcanic ash is actually fine, glassy fragments and particles that can cause severe injury to breathing passages, eyes, and open wounds, and irritation to skin. Follow these precautions to keep yourself safe from ashfall:
    • Wear long-sleeved shirts and long pants.
    • Use goggles and wear eyeglasses instead of contact lenses.
    • Use a dust mask or hold a damp cloth over your face to help breathing.
    • Do not run car or truck engines. Driving can stir up volcanic ash that can clog engines and stall vehicles. Moving parts can be damaged from abrasion, including bearings, brakes, and transmissions.

What to do after the eruption

  1. Stay away from ashfall areas if possible. If you are in an ashfall area cover your mouth and nose with a mask, keep skin covered, and wear goggles to protect the eyes.

  2. Clear roofs of ashfall because it can be very heavy and may cause buildings to collapse. Exercise great caution when working on a roof.

  3. Do not drive through ashfall, which is easily stirred up and can clog engine air filters, causing vehicles to stall.

  4. If you have a respiratory ailment, avoid contact with any amount of ash. Stay indoors until local health officials advise it is safe to go outside
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Federal Emergency Management Agency
22 Oct 2004 <http://www.fema.gov/>.

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