What is a Pyroclastic Flow?

I habitually listen to music while doing my homework.  Today i was listening to some Ice Cube and finishing my numerous math questions had been assigned.  Anyone who has listened to the album Raw Footage surely knows the part that this question comes from.  If you don't it goes like this, 

What's the definition of a pyroclastic flow?
That's what happens when a volcano blow
That's what happens when Ice Cube starts to flowRed hot s'lava, mixed with lavaPulverizing everything in its wakeNothing can survive a pyroclastic flowAnd no one will survive this one
So naturally, having nothing better to do i began to wonder, "what is a pyroclastic flow?"  The word pyroclast is derived from Greek words meaning fire and broken pieces.  A pyroclastic flow is a fast-moving current of gas and rock.  They are generally seen when a volcano erupts or parts of the volcano collapse, spewing large masses of gas that are heavier than the surrounding air.  These flows can travel as fast as 450 mph and reach temperatures of 1,830 degrees F. One interesting characteristic of pyroclastic flows is that they can cross large bodies of water as wide as 30 miles.  Though this has not been observed by scientists, it is generally accepted based on historical evidence and experimentation.
Final Verdict:  Don't get in the way of Ice Cube's pyroclastic flow 
Jason 

Sources: What Is A Pyroclastic Flow? by Ice Cube               http://en.wikipedia.org/wiki/Pyroclastic_flow