Saturday, June 21, 2008

When lightning strikes

Tech researchers to use electric discharge from clouds to study volcanic activity

Argen Duncan El Defensor Chieftain Reporter

ADUNCAN Lightning over an erupting volcano could mean greater safety for people, if the work of several New Mexico Tech researchers pays off.

Professors of Electrical Engineering Bill Rison and Ron Thomas along with Assistant Professor of Geophysics Jeffrey Johnson hope their data about lightning created over an erupting Chilean volcano will help predict hazards from volcanoes, as well as adding to scientific knowledge of lightning.

"If the volcano has another major eruption with a lot of lightning, we can hopefully understand lightning in volcanoes," Rison said.

If not, the scientists still intend to attempt to use lightning to determine the level of volcanic activity, leading to a technique to monitor volcanoes remotely and help predict danger to people.

Also, Johnson said the Tech researchers hope lightning can become a tool to track the volcano's activity over time, even when its hard-to-reach location and weather make it difficult for Chilean scientists to tell what's happening.

"But there's a lot of work to be done before that stage," he said.

In May, the Chaitén Volcano in the Andes on Chile's southern coast began erupting. The region is experiencing its rainy season, and clouds often block the view of the volcano's activity.

Tech scientists have developed a system for studying lightning in thunderstorms, and they have applied it to the study of volcanic lightning.

Thunderstorms produce radio signals, the source of hisses and pops on car radios used during the storms. The equipment locates those signals and creates a map of lightning bolts.

The Chaitén Volcano has rhyolitic eruptions, meaning they're particularly explosive, like Mount St. Helens. Johnson said this type of eruption is rare.

The Tech researchers wanted to find the pattern of volcanic lightning, which hasn't been scientifically observed much. They took four sensor stations to Chiloe Island across Corvovado Bay from the hard-to-reach volcano, took preliminary data and left the equipment to operate automatically, probably until July depending on what the volcano does.

The trip was the second time Tech scientists deployed equipment to study lightning created by a volcano. A team deployed two sensors to monitor an Alaskan volcano eruption in 2006.

Johnson said close access to the volcano is impossible except by plane, but the Tech sensors could operate from a distance.

Thomas said the position of the island allowed the researchers to get within 50 miles of the volcano. They used Google Maps to decide where they wanted to put sensors and then drove to the end of the road and asked an island farmer to let them put the station on his or her property.

"People there were very amiable," Johnson said.

Sheep, pigs and sometimes cattle roamed the yards where the Tech researchers worked. Johnson recalls seeing Rison troubleshooting with a laptop while trying to kick away a big, muddy pig.

Rison designed the instruments, while Johnson speaks Spanish and is familiar with Chile.

The researchers are analyzing their preliminary data and trying to get seismic information.

If they see lightning over the volcano, Thomas said, scientists are pretty sure the volcano is erupting. They would like to use the lightning to determine how much it's erupting.

"There's a lot of complications, though," Johnson said.

The researchers don't know if different eruptions generate different amounts of lightning.

Thomas said it would be interesting to see how thunderstorms and volcanic lightning are related.

"That will tell us some fundamental things about lightning and how clouds become electrified," he said.

Thomas and his colleagues theorized that part of the electricity is created as the ash exits the volcano. They think friction from rocks being broken and those particles rubbing together causes electricity, much like shoes being rubbed on carpet.

Also, in a thunderstorm, the interaction between frozen water particles causes electricity. Because volcanic eruptions release a lot of water into the atmosphere, where it freezes, Tech researchers hypothesize that similar interactions occur in volcanic plumes, which have lightning similar to that in thunderstorms.

The scientists want to get enough measurements to check their theories and learn how the mechanisms interact. Thomas said processes almost always turn out to be more complicated that originally thought.

The National Science Foundation is sponsoring the project.

aduncan@dchieftain.com

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