An avalanche of ash that tumbles down the side of an explosively erupting volcano.
A turbulent mixture of gas and rock fragments, most of which are ash-sized particles, ejected violently from a crater or fissure. The mass of pyroclastics is normally of very high temperature and moves rapidly down the slopes or even along a level surface.
A mixture of ash and gases, ejected from a fissure or crater, which flows rapidly down the slopes of a volcano.