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. Eruptions can be quiet or explosive. There may be lava flows, flattened landscapes, poisonous gases, and flying rock and ash. Fresh volcanic ash, made of pulverized rock, can be abrasive, acidic, gritty, gassy and odorous. The acidic gas and ash can cause lung problems for some people and can also damage machinery, including engines and electrical equipment. Volcanic eruptions can be accompanied by other natural hazards, including earthquakes, lahars (mudflows), flash floods, rock falls and landslides, acid rain, fire, and under special conditions, tsunamis.
Washington state is home to five major active volcanoes: Mount Baker, Glacier Peak, Mount Rainier, Mount St. Helens and Mount Adams. Both Mount Rainier and Mount St. Helens pose potential danger for those living the in the King County region. Residents living on or near the mountain, or in nearby valleys, can be affected by lahars (or mudflows) if an eruption should occur. Ashfall could also impact a larger area, depending on wind speed and direction.
One of the most distinguishing features of the King County landscape is Mount Rainier, a seemingly harmless mountain towering majestically over the skyscrapers and rural valleys. However, Mt. Rainier is an ACTIVE volcano, whose potential eruption would be incredibly destructive to our residents, businesses, and infrastructure. In addition to explosive eruptions, other potential threats from the mountain include dangerous volcanic mudflows called lahars.
For more information on Mount Rainier, visit USGS Cascade Range Volcanoes Summary - Mount Rainier
Mount St. Helens
In 1980 the Mount St. Helens eruption killed 57 people, caused nearly $1 billion in property damage, buried 230 square miles with landslide debris, deposited ash as deep as a half-inch 300 miles away, and plugged the Toutle and Cowlitz rivers with mud. Southwest of King County, this mountain presents a potential volcanic threat to Puget Sound residents because of the probability that hazardous ashfall will be released during an eruption. In fact, about an hour after the eruption of Mount St. Helens in 1980, ash began to fall in Yakima in Eastern Washington (about 150 miles east of Seattle). The ashfall was so heavy it became so dark that lights were turned on all day. It took ten weeks to haul away the ash from Yakima's streets, sidewalks, and roofs. While this hazard was last most spectacularly witnessed over 25 years ago, recent stirrings at St. Helens have brought the threat back into regional focus.
For more information on Mount St. Helens, visit USGS Cascade Range Volcanoes Summary - Mount St. Helens
Hazard-specific preparedness steps
- Find out if you live or work in a volcano hazard area and learn about your community warning systems, emergency plans, and evacuation routes. Contact your local fire department or emergency management agency for more information.
- Be prepared for hazards that can accompany volcanoes: mudflows and flash floods, landslides and rock falls, earthquakes, ashfall, acid rain, and in some cases, tsunamis.
- Plan two evacuation routes out of your neighborhood and be familiar with your community's pre-established evacuation routes.
- Get goggles and throw-away breathing masks for each member of the household in case of ashfall. Add them to your emergency supply kits at home and in all vehicles.
- Stay out of the area defined as a restricted zone by government officials. Effects of a volcanic eruption can be experienced many miles from a volcano.
- Monitor your NOAA weather radio and keep a local radio and/or television on for information and emergency instructions.
- If directed by authorities to evacuate, do so immediately.
- Bring animals and livestock into closed shelters.
- Stay inside and close all windows, doors and dampers. Place damp clothes at door thresholds and other draft sources. Tape drafty windows.
- Put all machinery inside a garage or barn.
- 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.
If caught outside:
- Cover your mouth and nose. Volcanic ash can irritate your respiratory system.
- Avoid areas downwind from the volcano, river valleys, and low-lying areas.
- Beware of mudflows. Move up slope, especially if you hear a roar of a mudflow. The danger increases near streams and river channels. Mudflows can move faster than you can walk or run. Look upstream before crossing a bridge, and do not cross the bridge if mudflow is approaching.
- If caught in a rock fall, roll into a ball to protect your head.
- Keep skin covered to avoid irritation from contact with ashfall.
Protection from ashfall:
- 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).
- If you have a respiratory problem, avoid contact with any type of ash.
- Wear goggles to protect your eyes.
- Wear glasses instead of contact lenses.
- Wear long-sleeved shirt and pants to protect your skin.
- Use a dust-mask or hold a damp cloth over your face to help breathing.
- Keep car or truck engines off.
- Clear roofs and rain gutters of ashfall. Ashfall is very heavy and can cause buildings to collapse. Use extreme caution when working on a roof.
- Avoid running vehicle engines. Driving can stir up volcanic ash that can clog engines, damage moving parts, and stall vehicles.
- Avoid driving in heavy ashfall unless absolutely required. If you must drive, keep speed down to 35 MPH or slower. Be prepared to change oil, oil filter and air filters frequently (every 50 to 100 miles in heavy dust and every 500 to 1,000 miles in light dust).
- As much as possible, keep ash out of buildings, machinery, air and water supplies, downspouts, storm drains, etc.