This mound of geyserite to the left of the creek indicates that there have been geysers in this part of Yellowstone National Park for eons.
https://www.circologhislandi.net/en/conferenze/ The run off from pools and geysers in the Black Sand Geyser Basin flows into Iron Spring Creek. The reddish-brown color of the creek, however, is not from iron, but from a reddish brown algae that is present in the creek because of thermal warming.
This is another sunrise photograph.
https://www.petwantsclt.com/petwants-charlotte-ingredients/ The temperature had dropped to 28˚F on this early October morning, and so there was a magnificent display of steaming hot pools in the basin. The early light bathed the whole area in luminous beauty.