The Wild File: Lightning

Iceland's Eyjafjallajokull     Photo: Courtesy of bjarkis on Flickr.

Q. Why was there lightning in the ash clouds from that Icelandic volcano?

A. The eruption of Iceland's Eyjafjallajökull did more than ground European air traffic; it created dirty thunderstorms in its ash plume. Though many eruptions produce lightning, few cases have been studied. "The ash particles banging into each other in the cloud and the charges coming out of the vent aren't well understood," says Graydon Aulich, an atmospheric scientist at New Mexico Tech and co-author of a 2007 study on the topic published in the journal Science. According to the study, which was conducted during the 2006 eruption of Alaska's Mount Augustine, the ash emerging from all volcanoes emerges charged but may pick up additional electricity the same way a thunderhead does through colliding ice crystals. And when the strongly charged atmosphere becomes ripe for ionizing air molecules, the freed electrons carry electricity to the ground in the form of lightning bolts. During the 1980 Mount St. Helens eruption, ground strikes ignited hundreds of forest fires near the volcano.

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