opalescent pool at black sand basin in yellowstone national park

active america attraction background bacterial basin beautiful beauty black colorful destination erupting eruption formations fountain geologic geological geology geothermal geyser green heart hot hottest lake landmark landscape lava liquid mist montana national natural nature norris opalescent orange outdoor park pattern pool predicted rock rocks sand scenic shape smoke south spring springs states stones terrain thermal thermophiles tourism tourist travel upper usa vacation view volcanic volcano walkway water whirligig wonder world wyoming yellowstone