Mammoth Hot Springs Terraces Walk

The Mammoth Hot Springs Terraces Walk explores the most architecturally dramatic hydrothermal formation in Yellowstone National Park, where superheated water laden with dissolved calcium carbonate surfaces and builds vast stepped terraces of travertine limestone in a constantly evolving white and orange landscape. The boardwalk system loops through both the Lower and Upper Terrace areas, passing Liberty Cap—a 37-foot dormant hot spring cone—and ascending past Minerva, Mound, Canary Spring, and Angel Terrace, each with its distinctive pattern of flowing water, color-coded microbial mats, and skeletal dead trees bleached white by mineral deposits. The terraces change appearance dramatically depending on water flow; springs that were vigorously active a decade ago may today be dry and grey, while new vents open in unexpected locations. The colors of the microbial mats indicate water temperature: yellow thermophilic bacteria near 160 degrees Fahrenheit transition through orange to brown and black as water cools downslope. The Mammoth area is unique in Yellowstone for sitting atop carbonate rather than silicate rocks, making travertine rather than geyserite the dominant deposit. Pronghorn antelope and elk graze the broad flat terraces year-round, and elk frequently occupy the town of Mammoth adjacent to the park's oldest developed area, where the historic Fort Yellowstone buildings dating from 1891 still serve as park headquarters.