Particles of ash become positively or negatively charged as they shoot upwards in a volcanic plume. The imbalance is restored to neutral when lightning flows between the positive and negative regions of the cloud. I would love to see this! Puyehue Chile, June 5, 2011
This is a rare meteorological phenomenon called a skypunch. Ice crystals form above the high-altitude cirro-cumulo-stratus clouds, then fall downward, punching a hole in the cloud cover. Freakishly awesome!