How Lahar Is Produced?

Pyroclastic flows

can generate lahars when extremely hot, flowing rock debris erodes, mixes with, and melts snow and ice as it travel rapidly down steep slopes. Lahars can also be formed when high-volume or long-duration rainfall occurs during or after an eruption.

Where does the material in lahar come from?

A lahar is a debris flow composed of a significant component of volcanic materials (> 25%) (Fisher and Schmincke, 1984). Lahars are volcanic mudflows, and they do not have to come directly from volcanic activity. They occur when huge amounts of volcanic ash, mixed with water flows down the side of a mountain.

How is lahar different from lava flow?

Everything in the path of an advancing lava flow will be knocked over, surrounded, or buried by lava, or ignited by the extremely hot temperature of lava. When lava erupts beneath a glacier or flows over snow and ice, meltwater from the ice and snow can result in far-reaching lahars.