What is a Pyroclastic Flow? Lyrics

Wh [ Lyrics from: http://www.lyricenter.com/e29660-ice_cube~what_is_a_pyroclastic_flow__lyrics.html ]
7;t's the definition of a pyroclastic flow
That's what happens when a volcano blow
That's what happens when Ice Cube starts to flow
Red hot lava mixed with saliva
Pulverising everything in its wake
Nothing can survive a pyroclastic flow
And no one will survive this one