Tracking Subtle Signals of Awakening Volcanoes

Scientists try to gather crucial background data to understand likelihood of future action

Since the volcano awoke on the Caribbean isle of Montserrat two years ago, it has become a showcase for volcanologists. Their gas sniffers, seismometers, and other gear have kept islanders as alert to their restless mountain as they would be to an approaching hurricane.

Yet one aspect of their geophysical prowess disappoints Michael Sheridan: Their forecasts, he says, haven't kept up with the volcano's growing destructive potential.

A volcano scientist with the State University of New York at Buffalo, Dr. Sheridan notes that it must be "disturbing" to look at a map designating your area as safe only to learn it isn't safe anymore.

At that point, he adds, people in the area may not believe the revised warning. He doesn't blame the Montserrat Volcano Observatory team for the confusion. It didn't have crucial background data needed to assess what it's dealing with.

Sheridan explains that "the real problem" in volcano forecasting "is to establish a base-line knowledge of what a volcano is like before it shows signs of danger." Then monitors can pick up on small surface deformations, gas emissions, faint underground rumbles, and other subtle signs of a volcano's awakening years before there's obvious action. If they come in cold when eruption seems imminent, they are handicapped in figuring out what is going on, Sheridan says.

Amassing knowledge

Developing that base-line knowledge for hundreds of volcanoes around the world is the challenge volcanologists face as they enter the 21st century. Members of the Montserrat volcano team pointed this out in the journal Science last April. They noted that "many of the world's most dangerous volcanoes are still poorly understood," adding that "this lack of knowledge represents the most pressing problem in reducing volcanic risk in a global context."

There's more to that risk than a rain of hot rocks or flaming rivers of lava. Ash clouds from even mild eruptions can endanger aircraft. A "sleeping" volcano like Mt. Rainier in Washington State may be quietly melting its snow cap from below. The melt water then rots the underlying rock until it can suddenly give way, releasing a devastating mudflow. For Rainier, that would put much of Seattle at risk.

As a step toward getting the needed knowledge, the International Association of Volcanology and Chemistry of the Earth's Interior has designated 15 active mountains as "Decade volcanoes." (See box, below.) That marks them for intensive study as part of the United Nations International Decade for Natural Disaster Reduction program. They are not necessarily the most dangerous. There's no international money for the volcano program. Its sponsors hope that a Decade designation will give that volcano a certain priority in a nation's research funding.

That's happening in the United States. Marianne Guffanti, coordinator of the US Geological Survey (USGS) volcano hazards program in Reston, Va., says the survey now monitors 37 of 65 suspect volcanoes in the US (for more information: volcanoes. usgs.gov).

"As a result of being designated a Decade volcano, we've increased monitoring [at Mt. Rainier]," she says.

Long-term monitoring produces the kind of background knowledge of a volcano's potential behavior needed to develop land-use strategies and standby evacuation plans that minimize risk to people and property.

"With volcanoes, [such advance] warning can really make a difference," Dr. Guffanti says. She adds that people in the Seattle area already are beginning to take the mudflow risk seriously.

High-tech tools

Scientists have an array of high-tech tools to improve volcano monitoring. At Mauna Loa in Hawaii - another Decade volcano - Donald Swanson with the USGS Hawaii Volcano Observatory hopes to install an array of electronic strain and tilt meters. These could be read out minute by minute to give an ongoing movie-like view of telltale ground distortions around the volcano.

Robert Tilling, chief scientist for the USGS volcano hazards team in Menlo Park, Calif., says the satellite-based Global Positioning System offers the "wave of the next century in tracking volcanoes." GPS can locate sensors on the ground to within an accuracy of less than an inch. Over time, scientists could follow small ground deformations.

Sheridan says another wave of the future will be satellite-based precision radar, which can also track deformations. He's worked with Mexican scientists in monitoring Popocatpetl near Mexico City - a volcano he calls "extremely dangerous." He says he plans to use radar on an American satellite to be launched next year to study Popo and three other Mexican volcanoes.

Volcanologists like Sheridan hope the knowledge they gain will inspire better volcano risk planning. But, as the Montserrat experience shows, it can be hard to persuade people to evacuate even when a dangerous eruption is under way. Mr. Swanson notes that it is even harder to persuade politicians and business people to declare seemingly desirable but potentially risky areas off-limits when danger seems less imminent.

Volcanoes to Watch

Of the hundreds of volcanoes around the world, 15 active mountains have been designated "Decade Volcanoes" by the International Association of Volcanology and Chemistry of the Earth's Interior. They are not necessarily the most dangerous. The aim of the project is to draw attention to a small number of hot spots for intensive research and public-awareness efforts. In random order they are:

1. Mauna Loa, Hawaii, US

2. Rainier, Washington, US

3. Colima, Mexico

4. Santa Maria/Santiaguito, Guatemala

5. Galeras, Colombia

6. Teide, Spain

7. Etna, Italy

8. Vesuvius, Italy

9. Santorini, Greece

10. Merapi, Indonesia

11. Taal, Philippines

12. Sakurajima, Japan

13. Unzen, Japan

14. Ulawun, Papua New Guinea

15. Niragongo, Congo (formerly Zaire)

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