The mingling of lightning and ash seen below may be a "dirty thunderstorm."
The little-understood storms may be sparked when rock fragments, ash, and ice particles in the plume collide to produce static charges just as ice particles collide to create charge in regular thunderstorms.
Two of nature’s most spectacular forces produced an incredible brew in the skies of Chile as a volcanic eruption met a lightning storm.
Tonnes of dust and ash from the eruption of the Chaitén volcano poured into the night sky just as an electric storm passed overhead.
The resulting collision created a spectacular sight as lightning flickered around the dust cloud amid the orange glow of the volcano.
This took place in the summer of 2008.
-Pictures from unknown source (if you know, please let me know so I can cite them)