Vancouver-based volcanologists hope that studying the deadly fall eruptions of an Indonesian volcano will help explain why Mount St. Helens' eruptions of 2004-08 were so comparatively tame — and help them better predict when its next explosive eruption will take place.

"There are a lot of lessons learned that we implement domestically," said John Pallister, who leads the Vancouver-based Volcano Disaster Assistance Program team for the U.S. Geological Survey.

He and team members Andy Lockhart and Jeff Marso spent three weeks in Indonesia, assisting with response to the Mount Merapi eruption. They returned in early December.

"We want to see why this was such a large eruption," he said. "This one was probably the largest (at Merapi) in more than 100 years, since 1872."

Merapi released more gas than the usual eruptions there. Scientists are studying why and whether it means more large eruptions in the future, Pallister said. The amount of gas trapped in molten rock - magma — is a key factor in how violent any particular eruption will be at any volcano.

"Better understanding how gas builds up in magma and how frequently it causes big explosions — that helps us understand things like why the Mount St. Helens eruption event of 2004-08 had such gas-poor magma," Pallister said.

By contrast to its explosive eruptions in the early 1980s, the Mount St. Helens eruptions of 2004-08 were quiet, dome-building events. Scientists still are studying what sparks each type of eruption, and observing other volcanoes helps answer those questions.

"Unless you have volcanoes (and eruptions) that you can study frequently you can never answer those questions," Pallister said. "And Indonesia has at least half a dozen eruptions a year and several that require evacuations."

Since its 1986 creation, Volcano Disaster Assistance Program has responded to 24 major eruptions worldwide. The program helps cover the costs of travel and equipment. Japanese volcanologists also responded to the Indonesian eruption.

The local USGS team arrived in Indonesia after Merapi's eruption on Nov. 10, the deadliest in last fall's sequence of eruptions. However, the USGS already had been helping monitor the volcano using satellite radar technology. Once in Indonesia, the USGS crews also helped replace seismic instruments and other monitoring equipment.

Radar technology is relatively new in volcano research and allows scientists to "see" when a volcano is bulging or contracting. Pairing radar information with seismic readings gives officials a better idea of when a volcano will erupt and allows them to evaluate the most at-risk regions, Pallister said.

At Mount Merapi, for example, Indonesian officials were able to use the radar and seismic readings to issue evacuation notices when activity increased on the volcano.

More than 300 people died in the eruptions. But Pallister estimated close to 20,000 lives were saved due to the monitoring and advanced warning.

"Learning how other nations monitor volcanos and the strategies and kind of networks they have and the analysis of priorities — those kinds of lessons come back domestically and end up going back internationally (to other countries) too," Pallister said.

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