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"That's Telling You There's a Lot of Ash"When Alaska's Redoubt Volcano rumbled to life three years ago (pictured), researchers rushed to the scene to deploy radio sensors to catalog and map lightning within the plume. The readings, the team now reports, reveal that volcanic lightning storms can be as powerful as giant Great Plains thunderstorms and that more lightning means a bigger plume."If you get lightning," said report coauthor Stephen McNutt, "that's telling you there's a lot of ash."That ash can spell trouble for air travelers, who may welcome another of the project's findings: that radio sensors can detect the beginnings of big plumes before they're visible to other instruments.—Richard A. Lovett

Photograph courtesy Bretwood Higman