Volcanic lightning most often occurs during eruptions which have large ash clouds. The 1982 eruption of the Galunggung volcano in Indonesia had a large ash cloud with volcanic lightning. Such spectacular displays occur when electrical discharges are generated by friction between particles and gases in an expanding eruption cloud. Volcanic lightning is primarily hazardous to airplanes and to radio transmissions. The lightning bolts are generally confined to the eruption cloud and crater area and are not a major threat to people or animals on the ground. However, volcanic lightning has been known to set forest fires in forested areas near the volcano crater.