The rapid ageing and break-up in 2285 of the planet created by the Genesis Device, whose matrix was unstable because David Marcus had used protomatter.
The end of the Genesis Planet is shown in Star Trek III: The Search for Spock. The planet formed from the Mutara Nebula when Khan set off the Genesis Device, and Spock's coffin came to rest on its surface. Within weeks it shows wild shifts of climate, with snow falling beside desert and jungle.
David Marcus admits that he used protomatter, a substance most scientists had condemned as dangerously unstable, in the Genesis matrix. The planet is ageing in surges, and the regenerated Spock ages with it.
As the surface tears itself apart, Kirk fights Kruge on a crumbling ledge and kicks him into the lava below. He then has himself and Spock beamed to the Klingon Bird-of-Prey, and the planet breaks up behind them. The result ends hopes for Genesis as a means of creating new worlds.