Strap explosives to the business end of a long hammer and bang it hard on the ground. That's the basic idea of this strange celebration in the town of San Juan de la Vega in Guanajuato, Mexico.

Metafilter user aetg explains what's going on:

OK, so the reasons for doing so may be a little vague, but in any case, they're exploding 'artisanal' explosives of a potassium chloride and sulphur base with big hammers. Apparently 17 people had minor wounds seen to by medics in 2007, and 50 in 2008, mostly due to being hit by explosive fragments, etc. That's not so bad given that there are 10-20 thousand people that come for the celebration. There are actually authorities supervising everything that's going on.

Explosives on a hammer? What can go wrong?

- via ask

From the Upcoming ueue, submitted by Christophe.