Sam can feel the movement of the guy's feet, even from just the shifting of his weight, like a shudder and a tremor in the ground, and it occurs to him that he could very easily accidentally crush Sam to death. Or at least seriously maim him.

The guy seems to have had that thought as well, thank God, and Sam shouts back, 'Here!' Then he pauses, and takes a moment to look around him. There's a rock, something he thinks would probably be a smallish boulder were he his normal size, near enough that he can feel the chill from it, and after a bracing breath, Sam (with utter inelegance) sets to scaling it.

It's harder than it looks, and he keeps sliding down, but after a moment or two, he hauls himself up on top of it, standing as tall as he can. It's weird to need to try and make himself tall. Again, he shouts, 'I'm here! Now would you tell me what the hell is going on here?!'