So cool！A special feature on the world’s five most amazing hot springs

Located in Yellowstone National Park in the United States, Mammoth Hot Springs is the world’s largest known carbonate-depositing hot spring. Millions of years ago, the seabed beneath the Mammoth area deposited thick layers of limestone. When hot acidic solutions flow through the rock layers to reach the surface of the springs, they dissolve large amounts of this depositing limestone. Upon exposure to air, some carbon dioxide in the solution evaporates. At the same time, solid minerals form and eventually settle as pristine white travertine, giving the Mammoth Hot Springs area vast terraces that look as if coated in frosting. This remarkable landscape also earns Mammoth Hot Springs a spot among the world’s most fascinating hot springs.

The color of the Grand Prismatic Spring’s surface changes with the seasons. In spring, the surface shifts from green to brilliant orange-red, due to the varying proportions of chlorophyll and carotenoids in the algae and pigmented bacteria living in the mineral-rich waters, which shift with the seasons and give the water different hues. In summer, with relatively lower chlorophyll levels, the colors appear orange, red, or yellow. In winter, due to lack of sunlight, these microorganisms produce more chlorophyll to suppress the carotenoid colors, resulting in a deep green appearance of the water.