Continuity mistake: At the end of the film, Nicolas Cage assaults the enemy compound with two Glock 17s. When he exits the compound and shoots at the boss's car, which is pulling away, in one shot he is firing a SIG P226, but in a later shot is using a Glock again. (01:28:55 - 01:29:45)
Character mistake: The professor identifies the "sea monsters" as plesiosaurs from the Pleistocene. Plesiosaurs became extinct at the end of the age of dinosaurs, nearly 60 million years before the Pleistocene. Of course, the Loch Ness Monster might be an exception.
Continuity mistake: When King is fighting with Lazarus in the bar, Lazarus gets blood near his mouth like you get when getting hit in the face. But when they fight near the white door, the blood is gone. (01:13:00 - 01:18:00)
Factual error: One of the women in the group picks up a piece of calcite (Iceland Spar variety). It is obviously calcite because of the very obvious rhombohedral cleavage and other visual indicators. The sample is later identified as ringwoodite. Ringwoodite is cubic with no reported cleavage. Even if it did exhibit cleavage, it would not be rhombodedral.
Visible crew/equipment: When Yu and his friends have finished dragging Yoko into the van, Yu jumps into the van and closes the door behind him. When he finishes closing the door, the reflection of the boom mic can be seen in the window. (02:44:50)
Factual error: The bar shown in Iqualuit is not real. Iqualuit only has 6100 or so people, and there is no bar like the one shown in the movie. The building is wrong - it doesn't even look like any buildings in Iqualuit. There is one bar that looks nothing like the movie, one Legion, and a bar in the hotel in Iqualuit.