A tourist visiting Yellowstone National park is believed to have died after falling into an acidic hot spring. A man is missing, presumed dead after wandering off a designated boardwalk and falling into a boiling spring, according to park officials on Tuesday. Billings Gazette reports: Witnesses saw a man in his early 20s walk off a boardwalk at Norris Geyser Basin and fall into a hot spring. Rangers have not found the man and are treating the incident as a probable death, park officials said in a statement. Because of the thermal hazards, rangers are being extremely cautious as they respond to the incident, according to the statement. The man fell about 225 yards away from the boardwalk. Norris Geyser Basin was subsequently closed. Rangers are investigating the incident and said no additional information would be released Tuesday evening. The basin is considered the hottest, oldest and most dynamic of Yellowstone’s thermal areas, according to the park’s website. It’s home to the highest temperature recorded in a Yellowstone geothermal area and has few thermal features under the boiling point. “The features in the basin change daily, with frequent disturbances from seismic activity and water fluctuations,” according to the park website. The possible death [...]