Ok, I can kinda see the train being built on a fault line. It would be a naturally flat area, but for the crack to open only as wide as the tracks I find questionable and the thing that really got me is it stopped as soon as it swallowed the train.
Kinda like the water stopping at their feet at the end. They didn't even get wet.
I think they made it cheesy on purpose. I think in the modern world of PC and feel good crap, they didn't want anyone to believe this could actually happen. They didn't want to scare anyone. And did anyone notice that not a single main character died. The only people with speaking roles who died were the family at the rest stop and the governor's aide. Afterall, they couldn't leave out that dying speech..."Tell Jimmy I love him" in a nice strong voice, just before she keels.
Nothing like the disaster movies of the 70s and 80s.