Fighting the volcano: a SWAT team of scientists tackles the ultimate challenge - an explosive volcano waking up from a 400-year sleep.
It was another day in paradise, the kind of day when all you want to do is laze on a sandy beach under tropical palms and a brilliant blue sky. It was June 25, 1997, on the tiny lush island of Montserrat, known as the Emerald Isle of the Caribbean.
Within 10 minutes the day turned dark as night. The island's volcano suddenly burst, spewing clouds of ash, lava, and gas sky high. Molten ash and rocks--a scorching 800 [degrees] C (1,472 [degrees] F) raced down the volcano's flanks, torching everything in their path.
Fortunately, Margaret Mangan was ready for action. Stationed at the Montserrat Volcano Observatory, she and other volcanologists (volcano scientists) had been keeping a close eye on the restless mountain for two days. Computer readouts showed the telltale signs of magma (molten rock) rising toward the surface. The signs included earthquake tremors and an actual bulge in the mountain's side.
The volcanologists immediately alerted island officials. Heeding warning sirens, essential workers still in the evacuated capital of Plymouth donned particle masks to filter out choking ash as they fled to the safety zone north of the volcano.
"There is nothing we can do to stop a volcano, but we try to get people and property out of the way as fast as we can," Mangan says.
Unfortunately, 19 people who ventured beyond roadblocks set up by local police were killed in the eruption.
When needed, Mangan is part of a "SWAT" team of scientists from the U.S. Geological Survey's Volcano Disaster Assistance Program. Their mission: to predict and help monitor volcanic eruptions, and to save lives wherever possible.
Knowing when a volcano will blow its top is tricky business. Scientists estimate that 1,500 active volcanoes exist worldwide. About 50 erupt each year, many with no warning. Since an estimated 500 million people around the world live dangerously close to volcanoes, the SWAT team is always on call.
The Montserrat volcano had been asleep for 400 years. But in June 1994, sensors on the mountain picked up the first alarm--a flurry of earthquakes, which often precede a stirring volcano. A year later came blasts of steam and ash, or phreatic eruptions. That's when island officials first called in the SWAT team.
The real source of trouble actually lay some 80 km (50 miles) underground. The Montserrat volcano, like many others, formed over a subduction zone, an area where two tectonic plates (slabs of Earth's crust) collide. In this case, the Caribbean plate subducts, or slides beneath, the North American plate. Under excessive heat and pressure, parts of the rocky Caribbean plate started to melt and form magma. Because they're less dense than surrounding rock, gobs of magma tend to rise. They collect in a shallow holding tank, or magma chamber, under the volcano.
Packed with dissolved gases, the magma starts to bubble up and expand. But with too little stretching room, the magma forces its way up to the surface, cracking the rock around it. The SWAT team's main role is to detect signs that magma is rising, and predict whether and when a volcano will explode.
On the Montserrat volcano, the team set up seismometers--instruments that detect earthquakes. "As magma pushes its way to the surface, the ground shakes and cracks," Mangan explains. The team also assembled geodetic devices, equipment that measures the swell of the Earth. "The rising magma actually inflates the ground surface like a balloon," she says. Finally, they brought in gas sensors to measure the amounts of sulfur in the air. "Gases power the eruption," says Mangan--the way gas bubbles make soda explode from a shake bottle.
Soon after the team's arrival, the mountain belched up to 1,200 tons of sulfurous gas a day. Thick, sticky magma oozed to the top of the volcano's vent, like a toothpaste tube squeezed from the bottom. The magma collected in a lava dome at the mountain top--seething with pent-up pressure. Sure enough, the first blast came on March 29, 1996. Powered by gases under pressure, huge chunks of the lava dome boiled down the mountain as a pyroclastic flow, a scalding avalanche. The volcano has erupted continuously ever since, with the largest eruption this past June.
Montserrat's eruptions have turned parts of a lush green paradise into a drab gray moonscape. About two-thirds of the island is blanketed by ash. Nearly 8,000 people (out of a total population of 12,000) have fled the island entirely. The other 4,000 have moved to safer ground in the north, where they live in crowded makeshift shelters. The airport and port where tourists once flocked are shut down. Ash has buried the recording studio where musicians like the Rolling Stones, Sting, and Paul McCartney once recorded hit songs.
Is it all over for Montserrat? Unlikely, Mangan replies. In 1902, a volcanic blast killed 30,000 people on the nearby island of Martinique. Today, the island thrives with palm trees and tourists. For now, the island of Montserrat may seem like a paradise lost. But as Mangan says, "One month after the devastation, I flew over the area. I could see little green shoots popping out of the ash." Life--and paradise--reborn.
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Volcanologist Margaret Mangan comes from a family of artists and dancers. "After high school I thought I would go into liberal arts," she says. But a geology course in college fueled a fascination with minerals. She decided to become a crystallographer--a scientist who studies the molecular structure of minerals. After college the U.S. Geological Survey hired Mangan to study volcanoes in Washington state. In 1990 she earned a Ph.D. in volcanology at Johns Hopkins University. Today she works at the Hawaiian Volcano Observatory, at the summit of Kilauea volcano. There she witnesses gentle lava flows as well as fire fountains, geysers of molten lava that shoot up several hundred feet. On call for the volcano SWAT team, she has completed two tours of duty in Montserrat.
To learn more about being a SWAT team volcanologist, check out this Web site: http://vulcan.wr.usgs.gov (scroll to Volcano Disaster Assistance Program)
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Ready to Blow
Scientists have devised a list of volcanoes that could erupt at any time. Use an atlas to pinpoint the volcanoes on a map. What do they have in common? How many are near big cities? Why do you think scientists made this list?
(*) 1. Merapi, Indonesia
2. Taal, Philippines (*) 3. Unzen, Japan
4. Sakurajima, Japan
5. Ulawun, Papua New Guinea
6. Mauna Loa, USA
7. Rainier, USA (*) 8. Colima, Mexico
9. Santa Maria/Santiaguito, Guatemala
10. Galeras, Colombia
11. Teide, Spain
12. Vesuvius, Italy
13. Etna, Italy
14. Santorini, Greece (*)15. Niragongo, Congo
16. Avachinsky/Koryaksky, Russia
(*) These volcanoes have erupted in the 1990s.
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|Title Annotation:||volcano on the Caribbean island of Montserrat; includes notes on volcanologists|
|Date:||Nov 17, 1997|
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