Do you remeber the movie "Crack in the World"? If you do, you know what happens next. I need not elaborate.
Is that the movie in which a male planet mates with Mother Earth and she has babies....?(sorry tasteless joke ping!)
Great movie, couldn't find a poster or trailer to link to. It has become obscure.
Hey, not only do I remember it fondly, but I actually got to talk to the guy who wrote the screenplay!
And I have to admit that when I saw this story, "Crack in the World" is the first thing that came to mind. Classic, fun SF movie.