The ever-changing thermal geology of Yellowstone National Park has created a hot spot that melted an asphalt road and closed access to popular geysers and other attractions at the height of tourist season. As they examined possible fixes, park officials warned visitors not to hike into the affected area, where the danger of stepping through solid-looking soil into boiling-hot water was high. "There are plenty of other great places to see thermal features in the park," Yellowstone spokesman Al Nash said. "I wouldn't risk personal injury to see these during this temporary closure."