He sets the skewers on the grill as heat from a volcano begins to cook them. You see, it erupted there hundreds of years ago, but even today, the bedrock remains scorching hot. So if you pour water into a hole, it turns into steam in seconds, and dry brush can even ignite just by touching the surface. By placing a grill on top, the intense heat rises from the ground and superheats the metal, giving the meat a perfect sear.