the firehole river in yellowstone national park, as seen from the hot springs in the black sand basin geothermal area

algae america approaching area bacteria basin beauty black boardwalks boiling caldera ecosystem eruption famous feature firehole footpath geothermal geyser green heat hot lake landmark landscape mineral national nature nonchalant orange outdoors park pool river sand scenic seen spring springs steam storm storms summer thermal travel upper usa volcano water weather wonder wyoming yellow yellowstone