Cold lava flow is a mud-like mixture of volcanic ash, rock debris and water that flows down a volcano’s slopes in the rain. It is also known in Indonesia as a lahar.

In these flows, the lava erupts at temperatures of around 1,100 to 1,250°C (2,012 to 2,282°F). At Ol Doinyo Lengai, the lava erupts at a much cooler 510°C (950°F).