where does volcanic ash come from?

How is it created from a volcano? I know that lava comes from magma bubbling up from the earth, and thatsteam come from water hitting the magma. Is ash just magma that explodes out of the volcano with such force that it is blown into tiny ash-sized flakes?

Volcanic ash is not so much flake-size as it is sand-size, a fine grit that is blown into the air, and filters down into everything. I have seen volcano movies that got it all wrong; volcanic ash has no resemblance to any other kind of “ash”. I was living in Oregon when St. Helens blew in '80, and I shipped 350 lbs. of it to a company in Boston that sold it as souvenirs. Take my word for it, it is sand.

I posted this earlier in answer to another volcanic ash question. Great site: http://volcanoes.usgs.gov/ash/properties.html