Continuity mistake: When Lex comes climbing over the edge she rams one of her icepicks in the ground. Two shots later she has suddenly rammed her other icepick in the ground as well. We would have noticed if she did so. (00:04:25)
Continuity mistake: Lex gets the Predators glowing green blood splashed on her clothes when the alien kills it. Next shot her clothes are clean.
Answer: Remember that they find the pyramid because of detecting a heat source - which implies that there's something down there, either something living or a technological source, that's created that heat, as spontaneous fires are something of a rarity in the Antarctic. Essentially, they have little or no idea what they might encounter down there, so it makes sense to cover all the possible scenarios, including the possibility of encountering a hostile force.
Tailkinker ★