Ghostly, otherworldly beauty flows across this part of the Yellowstone landscape in the form of rivulets, wash slopes and crystalline pools of hot mineral water. Below the surface, a mostly hidden pipe or underground stream carries this water many miles northward from the Norris Geyser Basin, where it pours from Mammoth Hot Springs supersaturated with calcium carbonate—the same compound that forms limestone. As flow from the world’s largest carbonate spring decompresses and cools, it precipitates huge amounts of the material, known as “travertine” in this form, across thousands of square yards of landscape. That creates fascinating, ever-changing formations such as this, and entombs trees.
