mudflow

/ˈmʌdˌfloʊ/
noun
  1. A large, fast-moving mass of wet mud that flows down a slope, often caused by heavy rain or a volcanic eruption.
    • Heavy rains triggered a mudflow that blocked the highway.
    • The village was destroyed by a mudflow after the volcano erupted.
    • Residents were evacuated before the mudflow reached their homes.