Lightning in volcanic eruptions is caused by the same reason it occurs in thunderstorms — negative and positive charges separate in the atmosphere, and lightning is what restores the charges to balance. But why the charge separation occurs in volcanic eruptions in the first place is still not well-understood. There seem to be a few theories, including one that suggests the ash ejected from the volcano already carries a certain charge, which then interacts with the charges in the atmosphere.Volcanic lightning is difficult to capture — it usually only happens in the most intense eruptions, and is often confined to the very beginning of the eruption. While these are two of the hottest surfaces on Earth, lightning — at an astonishing 50,000 degrees Fahrenheit — is actually 25 times hotter than lava.
December 4, 2015 at 12:41 PM EST