Factual error: As the machine is traveling through time George becomes aware of "strange sounds" which, when he stops, turn out to be air raid sirens. At the speed at which he was traveling through time, the sirens would have had to operate continuously for several days in order for him to have been able to hear them.
Factual error: The plateau blows up because of a volcanic explosion, but the explosion looks nothing like a real eruption. First of all, the plume would be a darker colour, mostly dark grey, and second, the explosion would fly out of the tube the group came out of, so they should still be running, not resting. Also, there would be danger from pyroclastic flow, and lava runoff.