Chromatic Spring, Hot spring in Upper Geyser Basin, Yellowstone National Park, US.

Chromatic Spring is a hot spring in Upper Geyser Basin, Yellowstone National Park, reaching temperatures between 73 and 79 degrees Celsius (164 to 175 degrees Fahrenheit). The water displays intense color gradients caused by temperature variations and heat-loving microorganisms living in the pool.

This feature formed through volcanic activity and groundwater circulation beneath the Yellowstone region over thousands of years. Its thermal characteristics were documented by explorers and scientists during the 19th century as the park became known to the outside world.

The name Chromatic Spring refers to the pool's two colour zones: a deep blue centre ringed by a rust-orange margin, as seen from the nearby boardwalk. The spring shares its water with Beauty Pool, and rangers and visitors watch the pair to see which one is currently higher.

Stay on marked boardwalks when observing the spring, as the ground around it can be unstable and the water is extremely hot. The colors are best viewed under clear skies and when the sun is not directly overhead.

This pool has a direct water-level connection with nearby Beauty Pool, causing the water to rise and fall alternately between the two features. This happens because underground channels link the two systems together.