Shooting these striking photos—some taken just a few feet away from the flames—was far more physically demanding than most of Grunewald's previous projects of landscapes and wildlife. "The main problem was the acidic gases that whirled constantly in the crater," he says. "The night seriously increased the difficulty as well, because it became almost impossible to see when dense gases arrived—at times, we were stuck in gas plumes for over an hour without being able to see our hands.