Because we've walked the full perimeter already? I mean, there could be more out there than we saw. The fog got pretty thick there too, and it was too hot out in the desert to keep going. Even at night.

[and then there's the cold. and the water. and...okay, maybe they've made some assumptions. but there's something cutting them off from the outside world, so calling it an island seems fitting.]

I'm not saying we should head out there right now. We've kind of got bigger things to deal with first. But at some point, I think we need to take a look. It's the only other building I've seen so far.