Orange Mound Spring

Orange Mound Spring is a distinctive hot spring in Yellowstone National Park’s Mammoth Hot Springs area, notable for rising above the surrounding mostly flat terraces on a mound of travertine. Its dark orange color comes from orange cyanobacteria living on the travertine, supported by water that is relatively cool for Yellowstone at about 170°F. The spring’s color can shift with changing nutrient conditions, and its mound and limited outflow suggest great age. Its travertine deposits have also contributed to nearby cone-shaped springs. With flow that can vary from nearly dry to much stronger, it remains one of Mammoth’s most unusual thermal features.

Wyoming · United States