When Hunter May is talking to his father outside the Dome, he's looking at a piece of paper which reads, "NEED DON BABARA HERE NOW!" The next time we see it, it says the same thing but the word "DON" is on the same line as "NEED", which it wasn't originally.
If a sphere shrinks, it becomes smaller in all dimensions: length, width, and height. So as the Dome pulls away from the earth around it, it should also settle deeper into its own hole. Thus the ground level outside the Dome should appear higher than the ground level inside, contrary to what's shown in the episode. (Conceivably, the outside should also be experiencing vulcanism as the Dome slowly opens up a hole into the Earth's crust....)