Footage of a lightning storm swirling in dark clouds around the peak of the Taal volcano in the Philippines has gone viral. Officials said the plume from the volcano stretched 1 km into the sky. Volcanic lightning is an extremely rare phenomenon and is caused by highly-charged particles rubbing together in dense ash clouds in the stratosphere. Volcanic lightning may be a result of both volcanic ash and ice. The Taal Volcano, a tourist hotspot, is one of 16 spots on Earth designated so dangerous by scientists, that they have to be monitored around the clock.