I actually had this thought years ago but I never thought it was viable. One big explosion and a 25,000 year half life would spread it all over the world. So then I thought, how about an undersea volcanoe. But about that time I saw a couple of movies, like those things that got all radioactive and moved inland down in California, and Gorgo, and It Came From Beneath the Sea, and Them, and the one with the giant crab.
So I dismissed the idea, and ate a few bags of Cheetos instead.
parsy, who remembers that for some strange reason
“Them” and “It Came From Beneath the Sea” are classics.