This is a skull embedded in the flowstone floor. ...

I was trying to take a picture that would be about the moment of discovery, because when you're looking around in a cave, all you see is the little narrow cone of light that your headlamp hits. And it'll swing over this skull and there's a human skull on the floor looking at you. And there's this moment of discovery that's—it's quite a shock.

We came into this chamber with Dr. Awe, and he was talking. I went a little bit ahead and turned around, and I think I audibly gasped when I saw the skull.

—Photographer Stephen Alvarez