Character mistake: When in the mineshaft Trevor says that magnesium is used in gunpowder. That is not correct.
Character mistake: Trevor tells Sean to "eat his trilobite to keep his strength up." However, Trevor, a geologist, pronounces trilobite incorrectly as "TRIL-o-byt" instead of the correct pronunciation "TRY-luh-byt." The name derives from the fact that the creatures have 3 (tri) lobes. Tri - for 3 not Tril - for 3.
Answer: A mountain.