Throwing water into lava While discussing magma in class with my students, I showed a video of a man throwing water onto molten, running lava.  A large flame ensued.  I realize that the water is being converted into steam and expanding extremely rapidly, but why does this create a small "explosion," if you will?

Surely none of the lava is being "atomized" into the air in small droplets, is it?  But even so, they would not light aflame.
This is a Steam explosion generally the flame is due to the hydrogen produced when water is superheated so thermal decomposed into $\ce{H2}$ and $\ce{O2}$.

Quoting wikipedia:


  Steam explosions are not normally chemical explosions, although a
  number of substances react chemically with steam (for example,
  zirconium and superheated graphite react with steam and air
  respectively to give off hydrogen, which burns violently in air) so
  that chemical explosions and fires may follow.