Looks like we made it just in time. I backtracked to take a peek at the surface, and it's just one big fire. That's not a metaphor, I mean it's actually burning.
I guess some combination of the radiation that's leaking through the barrier and reflected sunlight is turning it into our own private hellscape. That's not exactly the kind of thing you want in your backyard, so the plan is to keep delving into these caverns.
The good news is that they're way bigger than we ever thought. We should be able to set up a pretty extensive base of operations, and after that...better not think that far ahead. Chin up and eyes forward, soldier.