# Volcanoes

![](media/image1.png){width="3.2875in" height="3.3055555555555554in"}

A 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 flatten
trees 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 harsh, 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, 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.

### 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-of-town 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 supply 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.  Avoid driving in heavy dust unless absolutely required. If you do
    drive in dense dust, keep speed down to 35 mph or slower.

7.  Remove heavy ash from flat or low-pitched 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.

    -   Keep car or truck engines off. 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.  Avoid 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 is very heavy and can cause
    buildings to collapse. Exercise great caution when working on a
    roof.

3.  Avoid driving through ashfall which is easily stirred up and can
    clog engines, 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.