Continuity mistake: When Trevor, Hannah and Sean are being pushed up in the T-Rex skull by the geyser, they are laying in the skull and you can see that there is harness rope that comes out from behind Trevor and Hannah's back (that they are laying on). But in the shot when they are pushed out the mountain by the geyser and reach their highest point (before they start falling back down to the ground again) there is no rope visible behind them or in the skull at all. In the following shot as they fall back down to the ground, the rope has reappeared. (01:17:35 - 01:18:20)
Continuity mistake: After Trevor, Hannah and Sean are forced out of the mountain (inside the T-Rex skull) by the pressure of the geyser, as they fall back down to the ground, they begin to slide through shrubbery. Between shots as they slide through, the amount of greenery and leaves that is inside the skull keeps changing from hardly any, to a lot, etc. (01:18:20)
Continuity mistake: As the T-Rex skull comes to a sliding stop at the bottom of the hill, Trevor, Sean and Hannah get splattered by berries. In the first shot there are a lot of berries on Trevor's shirt and face, then in the next shot there is hardly any and then there's a lot again in the third shot. (01:18:35)
Continuity mistake: When Sean is jumping around the floating, magnetic rocks, a piece breaks off and falls. Why does it fall? It would just float next to the big one - held up by the magnetism. It might even float higher up, since Sean's weight should affect the bigger piece a bit.
Continuity mistake: In the scene in Trevor's apartment, when he is leafing through the Jules Verne book, between shots he is looking in very different sections of the book. In one clip some of the first pages, next clip in the middle, then back to first pages.
Continuity mistake: When Sean first sees the 'magnetic rocks' forming a bridge across the chasm, there is a great distance between him and the other side, and about 20 floating rocks. When he starts to cross, the distance is now much shorter, and he only jumps on 6 or 7 rocks to get across.
Continuity mistake: When walking in the subterranean world, Trevor holds and reads from the Jules Verne Book. It is completely dry, even though they have just been swimming. A wet book stays wet for a long time, and the pages stick tightly together. And yes - they were long enough in the water for the book to get wet - and no, it was not in a watertight container.
Continuity mistake: As Trevor and Hannah and the boy are traveling up the volcano on the cushion of steam, Trevor's arm constantly changes position instantly with different shots. Sometimes his arm is across Hannah's chest, then it's under her head, and back across her chest.
Continuity mistake: When the Italian farmer starts to shout, Trevor raises his right arm to comfort Hannah. In the next shot it's down, and he doesn't raise it until much later.
Continuity mistake: The sweat stains on the front of their shirts keep changing throughout the movie.
Continuity mistake: After Trevor and the others are submerged in the water they have soaked everything, but the book is intact and dry moments after that.
Continuity mistake: Trevor is saved from falling down a cliff and sees a sign covered in dust. He gives it to Hannah and in the close-up most of the dust is gone.
Continuity mistake: The Italian farmer runs fast to see the crash. When the angle changes he's moved several meters behind where he was standing, and is now walking.
Continuity mistake: While crashing against the vineyards, the amount of grapes stain on all of the 3 guys' faces is not continuous between shots. It appears/disappears randomly.
Continuity mistake: After exiting the volcano, the group starts to fall down and they all shout in desperation. Then it cuts to a close-up where the cry is faintly heard, but none of them are shouting.
Continuity mistake: When the kid gives the diamond to the Italian man, the way the farmer holds it differs between shots.
Continuity mistake: After Trevor is saved from falling down a cliff, the way Hannah holds the No entry sign differs between shots.
Continuity mistake: Trevor arrives at the lab and Leonard has made a popsicle. The amount of ice on it increases or decreases randomly between shots.
Continuity mistake: After having flown up the volcano, and they start falling, while still lying in the T-Rex jaw, they should have been weightless, but they still lie down.
Continuity mistake: The black hose next to Leonard swaps from stiff to bent down between shots.
Answer: A mountain.