Just consider it a new way to carve a pumpkin at Halloween… the pumpkin is actually carved in the traditional way, but the pieces of the jack-o-lantern face get pushed back into place. A chemical reaction is triggered inside the pumpkin and the previously carved pieces are literally blown out of the pumpkin. If you didn't know that the pumpkin had been carved already, it would appear as if you magically carved the pumpkin with a single eruption. What about the science part of this? This method is a favorite among chemistry teachers, who use the demo to illustrate the energy released when you break a triple bond in a molecule of acetylene.
This information is provided for educational purposes only. Do not try this experiment. Make friends with your local chemistry teacher and let them amaze you with their pumpkin carving skills.
You will find a detailed discussion of the Exploding Pumpkin experiment on Steve Spangler's blog.