Looks like a victim of too low of air pressure tire hitting a curb, but obviously that's just a stupid guess. Anytime you ride a bike the possibility of a flat is there, major cut like that needs to be examined to figure out why and how and what can be done to prevent it. But I seriously doubt a 1 cm piece of glass caused that, I've ran into larger pieces of glass then that with skinny fragile road tires with far less damage then that, and a small 1 cm piece of glass did that to a MTB tire? I doubt it.