Continuity mistake: When they are in the sunken city, the haversack is put down on a rock with a hammer on top of it. In a later scene, the hammer handle is pointing in a different direction.
Visible crew/equipment: A diary flies out of Mason's hand while they are on a raft because of Earth's magnetic field. You can see a wire attached to the left corner of the book. (01:43:55)
Continuity mistake: When they are climbing up out of the hole to avoid the rising water in the cave, as they show the hole from below the water is about two feet below the hole, however when shown from the top the water looks to be about six inches below the hole, this keeps shifting back and forth during that scene.
Continuity mistake: Pat Boone was shot in the right arm by the villain. After a few scenes, his wound is gone - no evidence of an injury. (01:34:05)
Revealing mistake: When the four travelers are riding up the volcano in the asbestos basin, they are obviously dummies.
Factual error: There is an explosion in the laboratory supposedly because the professor's assistant added too much aqua regia. Aqua regia will do a lot of things, but in an open furnace it will not explode.
Revealing mistake: Pat Boone gets lost. He walks over to a rock bridge, over a phosphorescent lake, which breaks up just before he steps on it. The larger chunk begins to fall but stops and bounces back up a bit because it hits a stage. (01:13:30)
Continuity mistake: Arlene Dahl trips while running away from a dinosaur by stepping into a loop in a rope attached to a raft. Her foot snags it below the ankle near her toes. A few seconds later, you see a close-up of her and the dinosaur and now the rope is above her ankle. A few scenes later it's below her ankle again as the men come to her rescue. (01:42:10)
Continuity mistake: Before the explosion in the lab, James Mason has his gloves, after the explosion he has to crawl around the desk only to find his gloves laying on the floor. Extra set?
Revealing mistake: As Mason's party rides a giant offering bowl (on magma) up a volcanic vent, you can see a straight seam joining the tubular vent on the bottom portion of the screen. (02:02:30)
Continuity mistake: When madam breaks the stalactite during the flood, there is a small hole which grows wider and smoother as the team evacuates.
Other mistake: The Count and the Professor jump into the water to save themselves from the dinosaurs (which can't swim). In the long shots, it appears they are out very far, in at least six foot deep water, but close up, the water they are in couldn't be higher than four feet. What's to keep the dinosaurs from grabbing the two if they're in water that wouldn' come up to the dinosaurs' kneecaps?
Audio problem: Throughout the movie when they are underground, when someone speaks sometimes you hear an echo and sometimes you don't.
Factual error: Iceland has had no titles of nobility for nearly 1000 years, therefore Saknussem can't be a "count".
Other mistake: While they're waiting for sunrise on the volcano the professor is carrying a rifle. Later on underground it's never seen.
Answer: It's just an added sound effect that foreshadows an ominous event (the giant reptile) that is about to happen. It's not meant to be anything naturally occurring.
raywest ★