America's Most Dangerous VOLCANO.

For thousands who live near Mount Rainier, the mountain is more than a beautiful sight. It's an explosion waiting to happen.

It's an ordinary day in Orting, Washington, with neighborhood kids shooting hoops in driveways and tearing around on their bikes. But looming high above their homes is the 4,392 meter (14,410 foot)-high, snowcapped Mount Rainier--the most dangerous volcano in the United States. When it erupts--and scientists say one day it will--blistering avalanches of hot rock, lava, and ash will sweep down the volcano.

Worse, walls of mud hundreds of meters deep, called lahars--filled with melted ice, boulders, and whole forests of uprooted trees--will gush down river valleys. Like concrete cascading down a cement truck chute, lahars could even entomb the streets of Orting. "We do volcano drills in school every year and climb on buses in case we need to get out fast," says Orting High School student Josh Garber, 14. Brianna Backus, 14, adds, "I do think there's a chance Rainier could blow, but we live far enough away to escape in time. I'm not afraid for myself--I'm more afraid for my dog and my fish."

Rainier is one of many potentially explosive volcanoes in the Cascades, a mountain range extending from Northern California to British Columbia, Canada. Seven Cascades volcanoes have erupted in the last 200 years, including Washington's Mount St. Helens in 1980. It spewed steam and ash at more than 321 kilometers (200 miles) per hour, flooding valleys below with debris from the largest landslide in human history.

Many towns have been built near the 165 potentially active volcanoes that bubble away in the continental U.S., Alaska, and Hawaii. And near Mt. Rainier at least 100,000 people live on the solidified mudflows of past eruptions, with millions more in nearby Seattle and Tacoma. "There's nothing we can do to stop a volcano," says U.S. Geological Survey (USGS) volcanologist (volcano scientist) Margaret Mangen.

WAITING TO EXPLODE

Why is Rainier so dangerous? Like most volcanoes, it sits on the edge of two constantly shifting tectonic plates, sections of Earth's outermost layer, or crust. When tectonic plates collide, one plate may be squeezed down into Earth's mantle (layer below the crust), where rock melts into magma (molten rock); pressure thrusts magma toward the surface. There it becomes trapped in underground chambers like boiling oatmeal. If pressure becomes too great, the volcano erupts.

Disaster could come to Rainier in several ways: it may flow, blow, or both. If Rainier blows, like Mt. St. Helens did, it will erupt with violent force, shooting tons of gas, ash, and superheated volcanic rock or lava into the stratosphere, 50 km (31 mi) above Earth's surface. If it flows, a less explosive but still deadly eruption will trigger a pyroclastic flow--an avalanche of burning ash (as hot as 704 [degrees] C or 1,300 [degrees] F) that speeds downhill at 129 km (80 mi) per hour, incinerating everything in its wake.

Fortunately, Rainier won't erupt without warning. Before it explodes, the volcano will swell, spout steam and gas, and rumble noisily for months. Such signs help volcanologists predict eruptions and warn area residents in time to evacuate.

DICEY SCIENCE

But predicting volcanic eruptions remains a dicey science. The Mt. St. Helens explosion came sooner and proved far more powerful than scientists predicted. The eruption killed 57 people and became a wake-up call to scientists at USGS monitoring stations near potentially dangerous volcanoes.

Geologists quickly mapped rock deposits from previous eruptions to chart their frequency. To monitor Rainier, volcanologists deployed six seismometers, instruments that detect even small quakes often preceding an eruption. They also installed instruments near high-risk volcanoes: tiltmeters, which detect ground movements, and Global Positioning System (GPS) satellite receivers to pinpoint ground-movement location. And researchers analyzed the chemistry and temperature of gas emissions from volcanic hot springs and gas vents called fumaroles. As Japanese geochemist Sadao Matsuo has said, "Volcanic gas is a telegram from Earth's interior."

If Rainier erupts, lava or pyroclastic flow shouldn't reach far beyond the boundaries of Mount Rainier National Park, explains Willie Scott, head scientist at the Cascades Volcano Observatory in Vancouver, Washington. But a lahar flow, triggered by earthquakes could be far more lethal to towns and cities. When Rainier erupted 5,600 years ago, an ocean of lahar buried a 259 square km (100 square mi) area of the White and Puyallup River valleys in sludge (see chart, p. 14).

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Monitoring data may help predict when and how Rainier might explode next, Scott thinks. "But my concern is that by the time a flowing lahar is detected, it could be as little as 45 minutes from the nearest town. So warning has to be automatic and reliable." Mt. Rainier and Mt. St. Helens are the only two U.S. volcanoes permanently monitored for lahars. Scientists use geophones--microphones placed underground in river valleys, which "hear" approaching mudslides and trip an alarm system. Compact solar-powered sensors transmit radio signals to emergency centers, which would spread an alarm via a computerized warning system.

Many people live in the shadow of this beautiful, unstable mountain. "I think people are overexaggerating this stuff," Orting High School's Sean McIlraith, 16, says. "I know if it does happen, it could be catastrophic. But I think people are just making too big of a deal." In the meantime, scientists' best hope is to educate and protect residents as best they can from a fatal landslide or explosion from America's most dangerous volcano.

Adapted and reprinted with permission of Discover magazine [C] 1999.

In Close Range of a Killer

In the past 4,000 years, four eruptions have burried Mount Rainier's river valleys in deadly lava and mud-slides. Its next eruption could destroy areas 50 or more miles away.

Mount St. Helens: NEW LIFE FROM THE ASHES

On May 18, 1980, Mount St. Helens in Washington State exploded. Part of the mountain top blew off, and in the immediate area around the volcano no life survived. Since then, ecologists (scientists who study relationships between organisms) have used the devastated landscape to investigate how natural environments, or ecosystems, recover from such destruction.

What they learned has turned their theories upside down. "We thought we knew what was going to happen," says Terry Franklin, a forest ecologist at the University of Washington. "We were clearly wrong." Scientists expected life would renew itself in orderly fashion and return to its original state: plants like mosses and lichens would revive first--they can withstand harsh conditions. These species would pave the way for wildflowers and herbs, then deciduous plants (losing their leaves in winter); finally conifers, or evergreen trees, would grow back.

Instead, renewal amid the lifeless landscape proved more random. Pockets of survivors, like moles, gophers, and ants survived underground. Saplings and shrubs still shrouded in snow weathered the blast that toppled tall trees. Wildflower roots were swept away with the avalanche--then sprouted in entirely new places.

Life around Mt. St. Helens flourishes once again, but the "neighborhood" has changed dramatically, with many new species and different numbers of previous residents.

HANDS-ON SCIENCE

Create a Crater

During a volcanic eruption, hot gases trapped beneath rock burst from the volcano's center. The sudden release of gaseous pressure causes the mountain-like structure to collapse, and leaves a massive crater, or caldera, in its center. Want to create your own volcanic crater? Try this activity.

YOU NEED:

box * balloon * plastic tubing * clamp * newspaper * tape * 2.27 kilogram (5 pound) bag of flour

TO DO:

1. Line the box with newspaper, then punch a hole (large enough to fit the tubing) through the center of the box and the newspaper.

2. Pass the tubing through the hole and stretch the opening of the balloon over the tubing. Secure the balloon to the tubing with tape.

3. Blow through the tubing to inflate the balloon at least 5 centimeters (2 inches) in diameter; to keep air pressure in the balloon, clamp off the plastic tubing.

4. Bury the balloon beneath a cone-shaped mound of flour.

5. Open the clamp and let the balloon deflate.

CONCLUSION:

What happens to the flour? Why? What force holds up the mountain of flour!

America's Most Dangerous Volcano * Earth Science: Volcano

Cross-Curricular Connection

History: Have students research a historic volcanic eruption and report its effects on people and the environment.

Did You Know?

* We think of volcanoes as cone-shaped mountains, but any hole through which lava reaches Earth's surface is a volcano. Most are found beneath the sea.

* On May 8, 1902, one of the worst volcanic disasters of the 20th century struck the Caribbean island of Martinique. Mt. Pelee erupted, killing 29,000 residents.

* Volcano-monitoring technologies save lives. In spring 1991, scientists from the U.S. and Philippines monitoring Mt. Pinatubo determined an eruption was imminent. It exploded on June 15--but most local residents had been evacuated.

National Science Education Standards 

Grades 5-8: structure of Earth's systems * Earth's history * natural hazards * science and technology in society * populations, resources, and environments

Grades 9-12: energy in Earth's system * geochemical cycles * science and technology in local, national and global challenges * natural and human-induced hazards

Resources

"Under the Volcano," Discover, November, 1999, p. 82 "as Mt. St. Helens Recovers, Old Wisdom Crumbles," The New York Times, May 16, 2000, p. F5

Volcano and Earthquake, by Susanna Van Rose, (Eyewitness Books, Dorling Kindersley, 2000)

America's Most Dangerous Volcano

1. Cascade

2. 13

3. volcanologist

4. tectonic

5. mantle

America's Most Dangerous Volcano

Directions: Fill in the blanks.

1. Mt. Rainier belongs to the West Coast's -- mountain range.

2. Rainier is one of -- potentially active volcanoes in the mountain chain.

3. A -- is a scientist who studies volcanoes.

4. Most volcanoes sit on the edge of two constantly shifting -- plates.

5. When these plates collide, one is usually pushed down through Earth's crust into the --.

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