I wasn't really talking about aliens. Most people who believe in the sort of fire-and-brimstone end to earth think that god (or some deity) will have a hand in it.
And God destroyed the world once... but saved Noah and his family. God said that He would not use water to rid the world of wickedness... the next time he would use fire.
We have no evidence that god destroyed the world, or that he even exists. At this point people generally cite evidence of floods of biblical proportions. My response: I don't doubt many many floods have occurred, and great floods are described in many religious texts. That just means a flood happened, not that god did it.
Yeah, I just wonder if that's just influence from earlier works than the Bible. The same things happened in other mythologies, I mean sharing very similar (or the same) stories. I know that the Bible is the truth for you, I'm just considering this.