Stephen King, "The End of the Whole Mess"

The brother of a well-meaning, civilization-killing genius tries to explain what happened to humanity in his last few hours.

(from Wastelands: Stories of the Apocalypse)

Funny and crazy, though not exactly scary, this is the messed up little fable of the too-smart brother thinking he can solve mankind's self-destructive tendencies. It's strange to think this was written in 1986 — although its description of Waco, TX, as one of the calmest places in the country does date it a little — because so much of the violence and unrest alluded to could be similarly described today. (According to Wikipedia, there's a TV version of this story out there somewhere.)

What Happened: A chemical presumed to contain a calming agent is dropped into a massive volcano so that, upon eruption, it will be dispersed around the world. Unfortunately it gives everybody Alzheimer's.
Destruct-O-Meter Score: 4. With its faculties horrifically and suddenly impaired, all of humanity is presumed to headed for an early demise. The planet, however, will probably be better off.
I've been wanting a collection like this. As in: I have verbalized — have specifically wished for — an anthology of end-of-the-world stories. You can have all your Illness Stories and your Turns Out Dad Was A Scoundrel Stories and This Lady Silently Bore A Burden Stories. I'll take ragnarok, thanks.