Orange Mound Spring, Thermal spring in Mammoth Hot Springs, Yellowstone National Park, US.
Orange Mound Spring is a thermal spring in Mammoth Hot Springs within Yellowstone National Park that emerges from multiple openings across its summit and sides. The water takes on an orange hue from cyanobacteria and leaves behind white travertine deposits that form layered terraces.
An early Yellowstone assistant superintendent named G.L. Henderson gave this thermal feature its name based on its distinctive orange appearance. The spring was long known to local people before receiving an official designation.
The spring sits in an area where Shoshone and Bannock peoples collected minerals from terraces to make traditional white pigments used in ceremonies and daily life. This practice reflected their deep connection to the thermal features of the region.
The spring maintains a steady temperature of around 77 degrees Celsius throughout the year, though water flow patterns shift with changing seasons. Visitors should observe from designated areas and avoid touching the thermal water since it reaches scalding temperatures.
A network of natural fractures beneath the spring forms an underground plumbing system that channels heated rainwater and snowmelt from surrounding mountains to the surface. This hidden pipe work runs continuously and shows how geothermal activity works beneath the ground.
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