I knelt down on the boardwalk, my camera hanging from my neck. “Look,” I exclaimed with excitement. “There really is something there.” There, with steam rising from it, and the sulphuric odor suffusing the air, there was life there at the water’s edge. This was on a walk among the glaciers in Yellowstone National Park. The brochures were right, it seemed. Even in this inhospitable environment, the very crust of…