As plumes of ash rise from a volcano, volcanic lightning sometimes erupts within its clouds. As it pierces through the billowing darkness, resembling a supernatural rage, the lightning’s incandescent flashes warn volcanologists far away that a potentially dangerous tower of ash is skyward.

In order to get lightning, the plume must be electrified. Generally, it’s assumed that ash particles jostling within the volcanic tempest build up huge electrical imbalances that can only be neutralized by supercharged bolts. But something else may contribute to the electrification of volcanic plumes.

By sending balloon-lofted electricity-detecting instruments over Sicily’s hyperactive Stromboli volcano, scientists discovered that even volcanic clouds that lack ash contain substantial amounts of charge. The source of this phantom electrification could be the decay of volcanic radon, an odorless and colorless radioactive compound.

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A similar process may occur above radon-emitting volcanoes around the world, said Karen Aplin, a physicist at the University of Bristol’s Department of Aerospace Engineering and a co-author of the study published this month in Geophysical Research Letters. If radon-driven electrification influences the behavior and lifetime of volcanic ash plumes — the very same that can down planes, bury cities and suffocate farms — then understanding the gas’s role could help people downwind from an eruption be better prepared.