The Telegraph has pictures of the volcano that is erupting in the Caulle Cordon of southern Chile.
Lightning is caused by ‘charge separation’. Charge separation is simply the movement of negative and positive charges away from each other. The process is described here.
1. Starting state (particles might have already been charged by some previous process).
2. Collisions lead to charge separation. For this to happen there has to be some difference in the electrical properties of the particles in the collisions.
3. Some process, such as aerodynamic sorting, segregates the positively and negatively charged particles. This means that there are sections of the cloud that are more negative or positive than other sections.
4. When the charge separation becomes too great, electricity will flow between the positive and negative regions of the cloud forming lightning and neutralizing the charge separation.
Lightning has been seen in numerous volcanic eruptions over the past couple of centuries, but the process of the charge separation within the plume is not well understood. Differing aerodynamic properties of ions that are formed at the time of the eruption might explain some of the lightning, but not all. Recently, researches have found lightning forming right at the mouth of the volcano, much too soon for aerodynamic properties to have an effect.
Ronald Thomas of New Mexico Tech has been studying volcanic lightning.
To get a better look at the lightning, Thomas and his colleagues set up radio receivers around Mount Augustine, an Alaskan volcano on an uninhabited island in Cook Inlet that erupts about every 10 years…
The radio receivers at multiple stations pick up the impulses, and the researchers can use them to pinpoint where the lightning occurred in a cloud based on when the impulses arrived at each station, similar to the way seismologists find the epicenter of an earthquake.
“So we can get a picture, in 3-D, of what the lightning looks like inside the cloud,” Thomas said.
Thomas and others hope that research into this early lightning might assist in predicting eruptions.
If they are successful in developing a mapping system, it could provide useful warning that an eruption has actually begun. ”Just because a volcano is rumbling and making lots of seismic noise, you can’t tell whether it erupted,” Thomas says. Tamsin Mather, a volcano researcher at the University of Oxford, in England, adds that the sensors could be a handy warning system especially for ”remote volcanoes in Alaska or Kamchatka that don’t have people watching them all the time but have plenty of planes that fly in the vicinity.” Airplanes have unknowingly flown into ash, which has sometimes choked their engines.
Research may also provide clues into earlier stages of earth’s history, when volcanic lightning may have provided the initial spark triggering the chemical reactions that ultimately led to life.