Where humans live in close proximity to volcanoes there is a risk of a natural hazard occuring. A
natural hazard is where an extreme natural event (such as an volcanic eruption) may have an impact
upon a vulunerable population. It is therefore necessary to manage the risk.
Mount Rainier is an active volcano that is currently dormant. Its next eruption might
produce volcanic ash, lava flows, or pyroclastic flows. The latter can rapidly melt snow
and ice, and the resulting meltwater could produce lahars that travel down valleys
beyond the base of the volcano to areas now densely populated. Lahars caused by large
landslides can also occur during non-eruptive times, without the seismicity and other
warnings that normally precede eruptions.
Lahars look and behave like flowing concrete, and their impact forces destroy most man-
made structures. At Mount Rainier, they have traveled 70-80 km/h at depths of 30
metres or more in confined valleys, slowing and thinning in the wide, now-populated
valleys.
Although Mount Rainier has erupted less often and less explosively in recent millennia
than its neighbor, Mount St. Helens, the proximity of large populations makes Mount
Rainier a far greater hazard to life and property.
Around Mt Rainier more than 150,000 people reside on the deposits of previous lahars. During the
past few millennia lahars that have reached the Puget Sound lowland have occurred, on average, at
least every 500 to 1,000 years. USGS research shows that some lahars occur with little or no
warning. Our only warning could be a report that a flow is under way.
The USGS monitors the state of the volcano and assesses hazards from volcanic activity. The lahar
pathways mapped by the USGS guide the hazard-area regulations of the comprehensive land-use
plan for local counties.
Because of the higher level of risk from lahars in the Carbon and Puyallup River valleys,
the USGS and Pierce County Department of Emergency Management have installed a
lahar-detection and warning system. The system consists of arrays flow monitors that
detect the ground vibrations of a lahar. Emergency managers then can initiate response
measures such as evacuations. This system for automatic detection and notification of a
lahar reduces, but does not eliminate, risk in the lahar pathways.
Time is short, and successful evacuation will depend on detection of the approaching
lahar, effective notification of people at risk, public understanding of the hazard, and
prompt response by citizens.
Communities are encouraged to Learn, Inquire and Plan. "Learn" to determine whether they live,
work, or go to school in a lahar hazard zone. "Inquire" by asking public officials to advise the
community about how to respond during any emergency. "Plan" by developing an emergency plan
with your family so that you are prepared for natural hazards and emergencies.
What to do Before a Volcanic Eruption
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 Eruption
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 disabilities.
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 lenses.
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 volcanic ash.
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 vents.
Clear heavy ash from flat or low-pitched roofs and rain gutters.
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 or slower.
Volcanic Hazard management
1. Describe the location of Mt Rainer
2. List 4 volcanic hazards associated with Mt Rainer
3. What is a Lahar?
4. Using the Map of lahar flows around Mt Rainer: Describe and explain the pattern of
volcanic hazards associated with Mt Rainer
5. Explain 3 ways in which the volcanic hazards around Mt Rainer are managed in the area
surrounding the volcano.
6. Using the information from FEMA produce a poster for people in the Mt Rainer area to
explain to them what to do during an earthquake Hazard.