Mount Rainier Lahars

Volcanic lightning may occur during the early stages of an eruption. Scientists think that ice forms when the smoke plume rises from the volcano. As the altitude of the plume increases, the water vapor it contains begins to form ice. Then, lightning forms the same way it does in a cloud during a storm. The colliding ice crystals build enough of an electric charge to generate lightning.

In addition to its deadly pyroclastic flows, Indonesia's Mount Merapi is also prone to lahars, an Indonesian word used worldwide for mud or debris flows.

Watch this video to see what a lahar looks like. Although the video is focused on the Mount Rainier stratovolcano in the northwest United States, lahars on Indonesian stratovolcanoes like Mount Merapi follow the same process.