Dirty storm - lightning in volcanic eruptions
PHOTOGRAPHY: SERGIO TAPIRO VELASCO. A powerful eruption illuminates the slopes of the Colima volcano in Mexico on December 13, 2015. Winning photograph of National Geographic’s 2017 travel photography contest.

The appearance of lightning in volcanic eruptions is, according to the most general explanation, a meteorological phenomenon that forms when the parts of the rocks, ashes and ice particles that expel the volcano collide with each other and provoke electrical reactions.

We call this phenomenon “dirty storm”.

The ashes coming out of the volcano are neutral. But the difference in temperature, friction and collisions between particles and gases cause them to be charged electrically with loads of the opposite sign.

Having different densities, these particles move and separate progressively into positive charge and negative charge. When the potential difference is large enough, the discharge occurs.

In addition to this, some experts such as Keri Nicoll, director of a team of researchers from the universities of Bristol, Reading and Bath (United Kingdom), believe that there is another very important agent in the formation of these lightnings: radon.

Radon is a radioactive, colorless and odorless gas that releases eruptions naturally.

The origin of this gas is completely natural. It comes from the natural radioactive decay of uranium.

Nicoll’s team examined the eruption of the Estromboli volcano in Sicily. There they observed that, although the generated clouds had hardly ashes, they were highly charged. After this analysis, the experts determined that the origin of this electrification could be in radon.

According to these researchers, the presence of this gas, in addition to ionizing the air, is capable of increasing the load and electrifying the volcanic plumes. However, Nicoll, director of research, acknowledges that they still need to make more measurements. Still, she claims that there is no other know electricity generation mechanism that explain the group’s observations. Therefore, the research is promising and it is very likely that this is the true explanation to the “dirty storms”.