When a massive sinkhole opens up and swallows a retired couple from Iowa it seems like a freak occurrence. But it's not the only one. Similar sinkholes are opening all over the world, even on the sea floor. And they're getting bigger.People living near the pits are reporting strange phenomena--vibrations, sulfurous odors, and odd sounds in the stygian depths. Then the pets begin to go missing.When people start disappearing as well, the government...