Let's Play Ninja Gaiden, Part 28

Wandering into the cavern of ice and fire, searching for iron ore and a furnace to smelt it in. Feels familiar, somehow. I'm very fascinated by the white strip that appears on the right side of the screen in the magma parts. It's not visible when playing, only appearing in the recording and disappearing if an object comes too close to the camera. It can't be an error with the capture device since that only takes the video signal and has no way of measuring Z depth, so it's probably some trick the game pulls that doesn't normally show up on a TV. I'm inclined to presume that it has something to do with the full-screen heat distortion effect, somehow. If anyone knows what's up with that, do tell!