actually a single impact might not have kill the dinosaur at all... newer studies shows the single impact kill scenario as being unlikely, it maybe that there were a few impact! if the rock is very BIG, earth gravity may cause enough stress on the rock to break it apart (http://en.wikipedia.org/wiki/Roche_limit). we won't be looking at 1 "killzone" but many... carpet bombing style... so maybe you would ask for a list of impact site instead of believing in hollywood's single impact theory.