After Japan and Indonesia, the United States is third in the world for volcano activity. Each year since 1980, we've had as many as 5 eruptions a year occurring in Alaska and Hawaii. In Washington, Oregon and California, the Cascade Range, we have approximately 2 each century. Volcanoes produce several hazards along with the eruption including:
Earthquakes.
Flash Floods.
Landslides and mudflows.
Thunderstorms.
Tsunamis.
Hazardous Gases.
Lava flows.
WHAT ARE VOLCANOES?
Volcanoes are actually vents in the earth's crust that molten rock escapes through. Mountains are pushed up from below the surface of the earth where volcanoes are built from the surface up from layers of lava, ashflows and ash. When the pressure from gases in the molten rock builds up too high it erupts.
More than 80 percent of the Earth's surface is volcanoes in origin both above and below sea level. Sea floors and mountains were formed by volcanic eruptions and gaseous emissions formed the Earth's oceans and atmosphere.
Small eruptions can produce quiet lava flows that creep along as slowly as 2 mph. Explosive eruptions can shoot columns of gasses and rock fragments miles into the atmosphere can spread ash hundreds of miles downwind and can hurl rocks for at least 20 miles. Most of the eruptions in the Hawaiian Islands are relatively quiet, producing slows rivers of lava and thousands of earthquakes a year, most too small to even feel. A major earthquake or eruptions usually occurs about every ten years. Prior and during eruptions many small earthquakes occur as molten rock is forced up through the cone of the volcano. These quakes provide warnings in changes in the volcanoes activity.
In the past thousand years, changes in the volcanic activity in the Cascade Range of the United States and Canada, stretching from Northern California into British Columbia, have produced over 100 eruptions, most of them dangerously explosive. The Cascade volcanoes however tend to lie dormant for longer periods of time. They aren't considered as active as the Hawaiian volcanoes but they are considerably more deadly. Lateral blasts, sideways-directed volcanic eruptions attributed to a majority of the deaths in the Mount St. Helens volcano along with tree blow-down. Lateral blasts can shoot huge pieces of rock for several miles. The rock debris from the lateral blast of Mount St. Helens had an initial speed of over 250 miles per hour and at a distance of 15 miles the blast speed was still 60 mph. Volcano blast zones are usually a 20-mile radius and some danger may exist for up to 100 miles or more affecting Montana and Wyoming in the United States.
Lava flows are rivers of molten rock. They are great fire hazards due to their intense heat and they destroy everything in their path. Most move slowly enough that people can get out of their path but their speed can vary depending on the composition of the lava, the rate that it's pumping through the vent and the steepness of the side of the cone.
The most destructive of volcano hazards are lahars. These are the mud or debris flows that are composed mostly of mud, rock and water. They can rush down valley and stream channels at up to 40 mph. Some contain so much rock debris that they look like rivers of wet concrete. The water in these flows come from melted snow, melted glacier, rain or summit crater lakes.
Ash from a volcano is actually a fine, glass-like rock fragment powder. It can contaminate water, cause electrical storms, collapse roofs, ruin machinery and affect people hundreds of miles away from the eruption. Aircraft-wise if can damage planes, diminish visibility and clog jet engines, causing them to fail.
The US Geological Survey monitors volcanoes and can usually forecast eruptions.
BEFORE A VOLCANO ERUPTION
Contact you local emergency management agency and find out if you are at risk. Learn about volcanic activity in your community and prepare your Family Disaster Plan. While volcano eruptions occur in specific areas, lava and ash can occur more than 20 miles away. Be aware of the volcano danger in your region. Make sure you develop an evacuation plan. Discuss volcano activity with your family. Review safety and preparedness measures several times a year.
Investigate you communities warning systems and emergency plans. Many communities have a siren system for volcano warning. Use NOAA radios with tone alert if there is activity.
Contact your insurance company regarding your homeowner's policy and find out what it will and will not cover in the event of a volcanic eruption.
Special Disaster Supply List for Volcanoes include:
Goggles for each family member.
Disposable breathing mask for each family member.
Long sleeve shirts and pants for each family member.
Socks, shoes and gloves for each family member.
Be prepared to evacuate in advance of the eruption and avoid areas downwind of the volcano and riverbeds or valleys.
DURING AN ERUPTION
If you are indoors:
Close all doors, windows and fireplace/stove dampers.
Make sure all machinery, equipment and vehicles are inside a garage or barn.
Move all animals and livestock into shelters to prevent them from breathing ash.
If you are outdoors:
Seek immediate shelter.
Roll into a ball to protect yourself during a rockfall.
AVOID low-lying areas where lava flows, poisonous gases and flooding will be most dangerous.
BEWARE OF MUDFLOWS - you'll be able to hear the roar of the approaching mudflow. Move quickly out of its path.
In general:
If you are told to evacuate, do so immediately. A good Family Disaster Plan will have provided you with readiness.
Stay out of the defined restricted zone.
AVOID valleys and low-lying areas.
Stay tuned via television or radio for information and instructions.
AFTER AN ERUPTION
When outdoors, protect yourself from ashfall by wearing goggles, mask and long-sleeve pants and shirts. Volcanic ash is actually fine, glassy fragments and particles that can cause sever injury to lungs, breathing passages, eyes, open wounds and irritation to the skin. If you have respiratory problems, stay indoors until local officials advise that the air quality has improved.
Clear roofs of ashfall which is very heavy and can cause building collapse. Take great care in working on a roof with volcanic ash as it is very slippery, especially after a rainfall which can occur with volcanic eruption.
Avoid driving during heavy ashfall. It can clog engines, damage bearing, brakes and transmissions due to abrasion.
Remember to help your neighbors who may require special assistance - infants, the elderly and the disabled. If forced to go out without a breathing mask during an ashfall, make sure you cover your nose and mouth with a wet washcloth or towel. Keep skin covered to avoid irritation, abrasion and burns.
